[bpt/emacs.git] / lisp / window.el

;;; window.el --- GNU Emacs window commands aside from those written in C

;; Copyright (C) 1985, 1989, 1992-1994, 2000-2012
;;   Free Software Foundation, Inc.

;; Maintainer: FSF
;; Keywords: internal
;; Package: emacs

;; This file is part of GNU Emacs.

;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:

;; Window tree functions.

;;; Code:

(defmacro save-selected-window (&rest body)
  "Execute BODY, then select the previously selected window.
The value returned is the value of the last form in BODY.

This macro saves and restores the selected window, as well as the
selected window in each frame.  If the previously selected window
is no longer live, then whatever window is selected at the end of
BODY remains selected.  If the previously selected window of some
frame is no longer live at the end of BODY, that frame's selected
window is left alone.

This macro saves and restores the current buffer, since otherwise
its normal operation could make a different buffer current.  The
order of recently selected windows and the buffer list ordering
are not altered by this macro (unless they are altered in BODY)."
  (declare (indent 0) (debug t))
  `(let ((save-selected-window-window (selected-window))
         ;; We save and restore all frames' selected windows, because
         ;; `select-window' can change the frame-selected-window of
         ;; whatever frame that window is in.  Each text terminal's
         ;; top-frame is preserved by putting it last in the list.
         (save-selected-window-alist
          (apply 'append
                 (mapcar (lambda (terminal)
                           (let ((frames (frames-on-display-list terminal))
                                 (top-frame (tty-top-frame terminal))
                                 alist)
                             (if top-frame
                                 (setq frames
                                       (cons top-frame
                                             (delq top-frame frames))))
                             (dolist (f frames)
                               (push (cons f (frame-selected-window f))
                                     alist))))
                         (terminal-list)))))
     (save-current-buffer
       (unwind-protect
           (progn ,@body)
         (dolist (elt save-selected-window-alist)
           (and (frame-live-p (car elt))
                (window-live-p (cdr elt))
                (set-frame-selected-window (car elt) (cdr elt) 'norecord)))
         (when (window-live-p save-selected-window-window)
           (select-window save-selected-window-window 'norecord))))))

(defvar temp-buffer-window-setup-hook nil
  "Normal hook run by `with-temp-buffer-window' before buffer display.
This hook is run by `with-temp-buffer-window' with the buffer to be
displayed current.")

(defvar temp-buffer-window-show-hook nil
  "Normal hook run by `with-temp-buffer-window' after buffer display.
This hook is run by `with-temp-buffer-window' with the buffer
displayed and current and its window selected.")

(defun temp-buffer-window-setup (buffer-or-name)
  "Set up temporary buffer specified by BUFFER-OR-NAME 
Return the buffer."
  (let ((old-dir default-directory)
        (buffer (get-buffer-create buffer-or-name)))
    (with-current-buffer buffer
      (kill-all-local-variables)
      (setq default-directory old-dir)
      (delete-all-overlays)
      (setq buffer-read-only nil)
      (setq buffer-file-name nil)
      (setq buffer-undo-list t)
      (let ((inhibit-read-only t)
            (inhibit-modification-hooks t))
        (erase-buffer)
        (run-hooks 'temp-buffer-window-setup-hook))
      ;; Return the buffer.
      buffer)))

(defun temp-buffer-window-show (&optional buffer action)
  "Show temporary buffer BUFFER in a window.
Return the window showing BUFFER.  Pass ACTION as action argument
to `display-buffer'."
  (let (window frame)
    (with-current-buffer buffer
      (set-buffer-modified-p nil)
      (setq buffer-read-only t)
      (goto-char (point-min))
      (when (setq window (display-buffer buffer action))
        (setq frame (window-frame window))
        (unless (eq frame (selected-frame))
          (raise-frame frame))
        (setq minibuffer-scroll-window window)
        (set-window-hscroll window 0)
        (with-selected-window window
          (run-hooks 'temp-buffer-window-show-hook)
          (when temp-buffer-resize-mode
            (resize-temp-buffer-window window)))
        ;; Return the window.
        window))))

(defmacro with-temp-buffer-window (buffer-or-name action quit-function &rest body)
  "Evaluate BODY and display buffer specified by BUFFER-OR-NAME.
BUFFER-OR-NAME must specify either a live buffer or the name of a
buffer.  If no buffer with such a name exists, create one.

Make sure the specified buffer is empty before evaluating BODY.
Do not make that buffer current for BODY.  Instead, bind
`standard-output' to that buffer, so that output generated with
`prin1' and similar functions in BODY goes into that buffer.

After evaluating BODY, mark the specified buffer unmodified and
read-only, and display it in a window via `display-buffer'.  Pass
ACTION as action argument to `display-buffer'.  Automatically
shrink the window used if `temp-buffer-resize-mode' is enabled.

Return the value returned by BODY unless QUIT-FUNCTION specifies
a function.  In that case, run the function with two arguments -
the window showing the specified buffer and the value returned by
BODY - and return the value returned by that function.

If the buffer is displayed on a new frame, the window manager may
decide to select that frame.  In that case, it's usually a good
strategy if the function specified by QUIT-FUNCTION selects the
window showing the buffer before reading a value from the
minibuffer, for example, when asking a `yes-or-no-p' question.

This construct is similar to `with-output-to-temp-buffer' but
does neither put the buffer in help mode nor does it call
`temp-buffer-show-function'.  It also runs different hooks,
namely `temp-buffer-window-setup-hook' (with the specified buffer
current) and `temp-buffer-window-show-hook' (with the specified
buffer current and the window showing it selected).

Since this macro calls `display-buffer', the window displaying
the buffer is usually not selected and the specified buffer
usually not made current.  QUIT-FUNCTION can override that."
  (declare (debug t))
  (let ((buffer (make-symbol "buffer"))
        (window (make-symbol "window"))
        (value (make-symbol "value")))
    `(let* ((,buffer (temp-buffer-window-setup ,buffer-or-name))
            (standard-output ,buffer)
            ,window ,value)
       (with-current-buffer ,buffer
         (setq ,value (progn ,@body))
         (setq ,window (temp-buffer-window-show ,buffer ,action)))

       (if (functionp ,quit-function)
           (funcall ,quit-function ,window ,value)
         ,value))))

;; The following two functions are like `window-next-sibling' and
;; `window-prev-sibling' but the WINDOW argument is _not_ optional (so
;; they don't substitute the selected window for nil), and they return
;; nil when WINDOW doesn't have a parent (like a frame's root window or
;; a minibuffer window).
(defun window-right (window)
  "Return WINDOW's right sibling.
Return nil if WINDOW is the root window of its frame.  WINDOW can
be any window."
  (and window (window-parent window) (window-next-sibling window)))

(defun window-left (window)
  "Return WINDOW's left sibling.
Return nil if WINDOW is the root window of its frame.  WINDOW can
be any window."
  (and window (window-parent window) (window-prev-sibling window)))

(defun window-child (window)
  "Return WINDOW's first child window.
WINDOW can be any window."
  (or (window-top-child window) (window-left-child window)))

(defun window-child-count (window)
  "Return number of WINDOW's child windows.
WINDOW can be any window."
  (let ((count 0))
    (when (and (windowp window) (setq window (window-child window)))
      (while window
        (setq count (1+ count))
        (setq window (window-next-sibling window))))
    count))

(defun window-last-child (window)
  "Return last child window of WINDOW.
WINDOW can be any window."
  (when (and (windowp window) (setq window (window-child window)))
    (while (window-next-sibling window)
      (setq window (window-next-sibling window))))
  window)

(defun window-normalize-buffer (buffer-or-name)
  "Return buffer specified by BUFFER-OR-NAME.
BUFFER-OR-NAME must be either a buffer or a string naming a live
buffer and defaults to the current buffer."
  (cond
   ((not buffer-or-name)
    (current-buffer))
   ((bufferp buffer-or-name)
    (if (buffer-live-p buffer-or-name)
        buffer-or-name
      (error "Buffer %s is not a live buffer" buffer-or-name)))
   ((get-buffer buffer-or-name))
   (t
    (error "No such buffer %s" buffer-or-name))))

(defun window-normalize-frame (frame)
  "Return frame specified by FRAME.
FRAME must be a live frame and defaults to the selected frame."
  (if frame
      (if (frame-live-p frame)
          frame
        (error "%s is not a live frame" frame))
    (selected-frame)))

(defun window-normalize-window (window &optional live-only)
  "Return the window specified by WINDOW.
If WINDOW is nil, return the selected window.  Otherwise, if
WINDOW is a live or an internal window, return WINDOW; if
LIVE-ONLY is non-nil, return WINDOW for a live window only.
Otherwise, signal an error."
  (cond
   ((null window)
    (selected-window))
   (live-only
    (if (window-live-p window)
        window
      (error "%s is not a live window" window)))
   ((window-valid-p window)
    window)
   (t
    (error "%s is not a valid window" window))))

(defvar ignore-window-parameters nil
  "If non-nil, standard functions ignore window parameters.
The functions currently affected by this are `split-window',
`delete-window', `delete-other-windows' and `other-window'.

An application may bind this to a non-nil value around calls to
these functions to inhibit processing of window parameters.")

(defconst window-safe-min-height 1
  "The absolute minimum number of lines of a window.
Anything less might crash Emacs.")

(defcustom window-min-height 4
  "The minimum number of lines of any window.
The value has to accommodate a mode- or header-line if present.
A value less than `window-safe-min-height' is ignored.  The value
of this variable is honored when windows are resized or split.

Applications should never rebind this variable.  To resize a
window to a height less than the one specified here, an
application should instead call `window-resize' with a non-nil
IGNORE argument.  In order to have `split-window' make a window
shorter, explicitly specify the SIZE argument of that function."
  :type 'integer
  :version "24.1"
  :group 'windows)

(defconst window-safe-min-width 2
  "The absolute minimum number of columns of a window.
Anything less might crash Emacs.")

(defcustom window-min-width 10
  "The minimum number of columns of any window.
The value has to accommodate margins, fringes, or scrollbars if
present.  A value less than `window-safe-min-width' is ignored.
The value of this variable is honored when windows are resized or
split.

Applications should never rebind this variable.  To resize a
window to a width less than the one specified here, an
application should instead call `window-resize' with a non-nil
IGNORE argument.  In order to have `split-window' make a window
narrower, explicitly specify the SIZE argument of that function."
  :type 'integer
  :version "24.1"
  :group 'windows)

(defun window-combined-p (&optional window horizontal)
  "Return non-nil if WINDOW has siblings in a given direction.
WINDOW must be a valid window and defaults to the selected one.

HORIZONTAL determines a direction for the window combination.
If HORIZONTAL is omitted or nil, return non-nil if WINDOW is part
of a vertical window combination.
If HORIZONTAL is non-nil, return non-nil if WINDOW is part of a
horizontal window combination."
  (setq window (window-normalize-window window))
  (let ((parent (window-parent window)))
    (and parent
         (if horizontal
             (window-left-child parent)
           (window-top-child parent)))))

(defun window-combinations (window &optional horizontal)
  "Return largest number of windows vertically arranged within WINDOW.
WINDOW must be a valid window and defaults to the selected one.
If HORIZONTAL is non-nil, return the largest number of
windows horizontally arranged within WINDOW."
  (setq window (window-normalize-window window))
  (cond
   ((window-live-p window)
    ;; If WINDOW is live, return 1.
    1)
   ((if horizontal
        (window-left-child window)
      (window-top-child window))
    ;; If WINDOW is iso-combined, return the sum of the values for all
    ;; child windows of WINDOW.
    (let ((child (window-child window))
          (count 0))
      (while child
        (setq count
              (+ (window-combinations child horizontal)
                 count))
        (setq child (window-right child)))
      count))
   (t
    ;; If WINDOW is not iso-combined, return the maximum value of any
    ;; child window of WINDOW.
    (let ((child (window-child window))
          (count 1))
      (while child
        (setq count
              (max (window-combinations child horizontal)
                   count))
        (setq child (window-right child)))
      count))))

(defun walk-window-tree-1 (fun walk-window-tree-window any &optional sub-only)
  "Helper function for `walk-window-tree' and `walk-window-subtree'."
  (let (walk-window-tree-buffer)
    (while walk-window-tree-window
      (setq walk-window-tree-buffer
            (window-buffer walk-window-tree-window))
      (when (or walk-window-tree-buffer any)
        (funcall fun walk-window-tree-window))
      (unless walk-window-tree-buffer
        (walk-window-tree-1
         fun (window-left-child walk-window-tree-window) any)
        (walk-window-tree-1
         fun (window-top-child walk-window-tree-window) any))
      (if sub-only
          (setq walk-window-tree-window nil)
        (setq walk-window-tree-window
              (window-right walk-window-tree-window))))))

(defun walk-window-tree (fun &optional frame any minibuf)
  "Run function FUN on each live window of FRAME.
FUN must be a function with one argument - a window.  FRAME must
be a live frame and defaults to the selected one.  ANY, if
non-nil, means to run FUN on all live and internal windows of
FRAME.

Optional argument MINIBUF t means run FUN on FRAME's minibuffer
window even if it isn't active.  MINIBUF nil or omitted means run
FUN on FRAME's minibuffer window only if it's active.  In both
cases the minibuffer window must be part of FRAME.  MINIBUF
neither nil nor t means never run FUN on the minibuffer window.

This function performs a pre-order, depth-first traversal of the
window tree.  If FUN changes the window tree, the result is
unpredictable."
  (setq frame (window-normalize-frame frame))
  (walk-window-tree-1 fun (frame-root-window frame) any)
  (when (memq minibuf '(nil t))
    ;; Run FUN on FRAME's minibuffer window if requested.
    (let ((minibuffer-window (minibuffer-window frame)))
      (when (and (window-live-p minibuffer-window)
                 (eq (window-frame minibuffer-window) frame)
                 (or (eq minibuf t)
                     (minibuffer-window-active-p minibuffer-window)))
        (funcall fun minibuffer-window)))))

(defun walk-window-subtree (fun &optional window any)
  "Run function FUN on the subtree of windows rooted at WINDOW.
WINDOW defaults to the selected window.  FUN must be a function
with one argument - a window.  By default, run FUN only on live
windows of the subtree.  If the optional argument ANY is non-nil,
run FUN on all live and internal windows of the subtree.  If
WINDOW is live, run FUN on WINDOW only.

This function performs a pre-order, depth-first traversal of the
subtree rooted at WINDOW.  If FUN changes that tree, the result
is unpredictable."
  (setq window (window-normalize-window window))
  (walk-window-tree-1 fun window any t))

(defun window-with-parameter (parameter &optional value frame any minibuf)
  "Return first window on FRAME with PARAMETER non-nil.
FRAME defaults to the selected frame.  Optional argument VALUE
non-nil means only return a window whose window-parameter value
for PARAMETER equals VALUE (comparison is done with `equal').
Optional argument ANY non-nil means consider internal windows
too.

Optional argument MINIBUF t means consider FRAME's minibuffer
window even if it isn't active.  MINIBUF nil or omitted means
consider FRAME's minibuffer window only if it's active.  In both
cases the minibuffer window must be part of FRAME.  MINIBUF
neither nil nor t means never consider the minibuffer window."
  (let (this-value)
    (catch 'found
      (walk-window-tree
       (lambda (window)
         (when (and (setq this-value (window-parameter window parameter))
                    (or (not value) (equal value this-value)))
           (throw 'found window)))
       frame any minibuf))))

;;; Atomic windows.
(defun window-atom-root (&optional window)
  "Return root of atomic window WINDOW is a part of.
WINDOW must be a valid window and defaults to the selected one.
Return nil if WINDOW is not part of an atomic window."
  (setq window (window-normalize-window window))
  (let (root)
    (while (and window (window-parameter window 'window-atom))
      (setq root window)
      (setq window (window-parent window)))
    root))

(defun window-make-atom (window)
  "Make WINDOW an atomic window.
WINDOW must be an internal window.  Return WINDOW."
  (if (not (window-child window))
      (error "Window %s is not an internal window" window)
    (walk-window-subtree
     (lambda (window)
       (set-window-parameter window 'window-atom t))
     window t)
    window))

(defun display-buffer-in-atom-window (buffer alist)
  "Display BUFFER in an atomic window.
This function displays BUFFER in a new window that will be
combined with an existing window to form an atomic window.  If
the existing window is already part of an atomic window, add the
new window to that atomic window.  Operations like `split-window'
or `delete-window', when applied to a constituent of an atomic
window, are applied atomically to the root of that atomic window.

ALIST is an association list of symbols and values.  The
following symbols can be used.

`window' specifies the existing window the new window shall be
  combined with.  Use `window-atom-root' to make the new window a
  sibling of an atomic window's root.  If an internal window is
  specified here, all children of that window become part of the
  atomic window too.  If no window is specified, the new window
  becomes a sibling of the selected window.

`side' denotes the side of the existing window where the new
  window shall be located.  Valid values are `below', `right',
  `above' and `left'.  The default is `below'.

The return value is the new window, nil when creating that window
failed."
  (let ((ignore-window-parameters t)
        (window-combination-limit t)
        (window (cdr (assq 'window alist)))
        (side (cdr (assq 'side alist)))
        new)
    (setq window (window-normalize-window window))
    ;; Split off new window
    (when (setq new (split-window window nil side))
      ;; Make sure we have a valid atomic window.
      (window-make-atom (window-parent window))
      ;; Display BUFFER in NEW and return NEW.
      (window--display-buffer
       buffer new 'window display-buffer-mark-dedicated))))

(defun window--atom-check-1 (window)
  "Subroutine of `window--atom-check'."
  (when window
    (if (window-parameter window 'window-atom)
        (let ((count 0))
          (when (or (catch 'reset
                      (walk-window-subtree
                       (lambda (window)
                         (if (window-parameter window 'window-atom)
                             (setq count (1+ count))
                           (throw 'reset t)))
                       window t))
                    ;; count >= 1 must hold here.  If there's no other
                    ;; window around dissolve this atomic window.
                    (= count 1))
            ;; Dissolve atomic window.
            (walk-window-subtree
             (lambda (window)
               (set-window-parameter window 'window-atom nil))
             window t)))
      ;; Check children.
      (unless (window-buffer window)
        (window--atom-check-1 (window-left-child window))
        (window--atom-check-1 (window-top-child window))))
    ;; Check right sibling
    (window--atom-check-1 (window-right window))))

(defun window--atom-check (&optional frame)
  "Check atomicity of all windows on FRAME.
FRAME defaults to the selected frame.  If an atomic window is
wrongly configured, reset the atomicity of all its windows on
FRAME to nil.  An atomic window is wrongly configured if it has
no child windows or one of its child windows is not atomic."
  (window--atom-check-1 (frame-root-window frame)))

;; Side windows.
(defvar window-sides '(left top right bottom)
  "Window sides.")

(defcustom window-sides-vertical nil
  "If non-nil, left and right side windows are full height.
Otherwise, top and bottom side windows are full width."
  :type 'boolean
  :group 'windows
  :version "24.1")

(defcustom window-sides-slots '(nil nil nil nil)
  "Maximum number of side window slots.
The value is a list of four elements specifying the number of
side window slots on (in this order) the left, top, right and
bottom side of each frame.  If an element is a number, this means
to display at most that many side windows on the corresponding
side.  If an element is nil, this means there's no bound on the
number of slots on that side."
  :version "24.1"
  :risky t
  :type
  '(list
    :value (nil nil nil nil)
    (choice
     :tag "Left"
     :help-echo "Maximum slots of left side window."
     :value nil
     :format "%[Left%] %v\n"
     (const :tag "Unlimited" :format "%t" nil)
     (integer :tag "Number" :value 2 :size 5))
    (choice
     :tag "Top"
     :help-echo "Maximum slots of top side window."
     :value nil
     :format "%[Top%] %v\n"
     (const :tag "Unlimited" :format "%t" nil)
     (integer :tag "Number" :value 3 :size 5))
    (choice
     :tag "Right"
     :help-echo "Maximum slots of right side window."
     :value nil
     :format "%[Right%] %v\n"
     (const :tag "Unlimited" :format "%t" nil)
     (integer :tag "Number" :value 2 :size 5))
    (choice
     :tag "Bottom"
     :help-echo "Maximum slots of bottom side window."
     :value nil
     :format "%[Bottom%] %v\n"
     (const :tag "Unlimited" :format "%t" nil)
     (integer :tag "Number" :value 3 :size 5)))
  :group 'windows)

(defun window--major-non-side-window (&optional frame)
  "Return the major non-side window of frame FRAME.
The optional argument FRAME must be a live frame and defaults to
the selected one.

If FRAME has at least one side window, the major non-side window
is either an internal non-side window such that all other
non-side windows on FRAME descend from it, or the single live
non-side window of FRAME.  If FRAME has no side windows, return
its root window."
  (let ((frame (window-normalize-frame frame))
        major sibling)
    ;; Set major to the _last_ window found by `walk-window-tree' that
    ;; is not a side window but has a side window as its sibling.
    (walk-window-tree
     (lambda (window)
       (and (not (window-parameter window 'window-side))
            (or (and (setq sibling (window-prev-sibling window))
                     (window-parameter sibling 'window-side))
                (and (setq sibling (window-next-sibling window))
                     (window-parameter sibling 'window-side)))
            (setq major window)))
     frame t)
    (or major (frame-root-window frame))))

(defun window--major-side-window (side)
  "Return major side window on SIDE.
SIDE must be one of the symbols `left', `top', `right' or
`bottom'.  Return nil if no such window exists."
  (let ((root (frame-root-window))
        window)
    ;; (1) If a window on the opposite side exists, return that window's
    ;;     sibling.
    ;; (2) If the new window shall span the entire side, return the
    ;;     frame's root window.
    ;; (3) If a window on an orthogonal side exists, return that
    ;;     window's sibling.
    ;; (4) Otherwise return the frame's root window.
    (cond
     ((or (and (eq side 'left)
               (setq window (window-with-parameter 'window-side 'right nil t)))
          (and (eq side 'top)
               (setq window (window-with-parameter 'window-side 'bottom nil t))))
      (window-prev-sibling window))
     ((or (and (eq side 'right)
               (setq window (window-with-parameter 'window-side 'left nil t)))
          (and (eq side 'bottom)
               (setq window (window-with-parameter 'window-side 'top nil t))))
      (window-next-sibling window))
     ((memq side '(left right))
      (cond
       (window-sides-vertical
        root)
       ((setq window (window-with-parameter 'window-side 'top nil t))
        (window-next-sibling window))
       ((setq window (window-with-parameter 'window-side 'bottom nil t))
        (window-prev-sibling window))
       (t root)))
     ((memq side '(top bottom))
      (cond
       ((not window-sides-vertical)
        root)
       ((setq window (window-with-parameter 'window-side 'left nil t))
        (window-next-sibling window))
       ((setq window (window-with-parameter 'window-side 'right nil t))
        (window-prev-sibling window))
       (t root))))))

(defun display-buffer-in-major-side-window (buffer side slot &optional alist)
  "Display BUFFER in a new window on SIDE of the selected frame.
SIDE must be one of `left', `top', `right' or `bottom'.  SLOT
specifies the slot to use.  ALIST is an association list of
symbols and values as passed to `display-buffer-in-side-window'.
This function may be called only if no window on SIDE exists yet.
The new window automatically becomes the \"major\" side window on
SIDE.  Return the new window, nil if its creation window failed."
  (let* ((root (frame-root-window))
         (left-or-right (memq side '(left right)))
         (size (or (assq 'size alist)
                   (/ (window-total-size (frame-root-window) left-or-right)
                      ;; By default use a fourth of the size of the
                      ;; frame's root window.  This has to be made
                      ;; customizable via ALIST.
                      4)))
         (major (window--major-side-window side))
         (selected-window (selected-window))
         (on-side (cond
                   ((eq side 'top) 'above)
                   ((eq side 'bottom) 'below)
                   (t side)))
         ;; The following two bindings will tell `split-window' to take
         ;; the space for the new window from `major' and not make a new
         ;; parent window unless needed.
         (window-combination-resize 'side)
         (window-combination-limit nil)
         (new (split-window major (- size) on-side))
         fun)
    (when new
      ;; Initialize `window-side' parameter of new window to SIDE.
      (set-window-parameter new 'window-side side)
      ;; Install `window-slot' parameter of new window.
      (set-window-parameter new 'window-slot slot)
      ;; Install `delete-window' parameter thus making sure that when
      ;; the new window is deleted, a side window on the opposite side
      ;; does not get resized.
      (set-window-parameter new 'delete-window 'delete-side-window)
      ;; Install BUFFER in new window and return NEW.
      (window--display-buffer buffer new 'window 'side))))

(defun delete-side-window (window)
  "Delete side window WINDOW."
  (let ((window-combination-resize
         (window-parameter (window-parent window) 'window-side))
        (ignore-window-parameters t))
    (delete-window window)))

(defun display-buffer-in-side-window (buffer alist)
  "Display BUFFER in a window on side SIDE of the selected frame.
ALIST is an association list of symbols and values.  The
following symbols can be used:

`side' denotes the side of the existing window where the new
  window shall be located.  Valid values are `bottom', `right',
  `top' and `left'.  The default is `bottom'.

`slot' if non-nil, specifies the window slot where to display
  BUFFER.  A value of zero or nil means use the middle slot on
  the specified side.  A negative value means use a slot
  preceding (that is, above or on the left of) the middle slot.
  A positive value means use a slot following (that is, below or
  on the right of) the middle slot.  The default is zero."
  (let ((side (or (cdr (assq 'side alist)) 'bottom))
        (slot (or (cdr (assq 'slot alist)) 0))
        new)
    (cond
     ((not (memq side '(top bottom left right)))
      (error "Invalid side %s specified" side))
     ((not (numberp slot))
      (error "Invalid slot %s specified" slot)))

    (let* ((major (window-with-parameter 'window-side side nil t))
           ;; `major' is the major window on SIDE, `windows' the list of
           ;; life windows on SIDE.
           (windows
            (when major
              (let (windows)
                (walk-window-tree
                 (lambda (window)
                   (when (eq (window-parameter window 'window-side) side)
                     (setq windows (cons window windows)))))
                (nreverse windows))))
           (slots (when major (max 1 (window-child-count major))))
           (max-slots
            (nth (cond
                  ((eq side 'left) 0)
                  ((eq side 'top) 1)
                  ((eq side 'right) 2)
                  ((eq side 'bottom) 3))
                 window-sides-slots))
           (selected-window (selected-window))
           window this-window this-slot prev-window next-window
           best-window best-slot abs-slot new-window)

      (cond
       ((and (numberp max-slots) (<= max-slots 0))
        ;; No side-slots available on this side.  Don't create an error,
        ;; just return nil.
        nil)
       ((not windows)
        ;; No major window exists on this side, make one.
        (display-buffer-in-major-side-window buffer side slot alist))
       (t
        ;; Scan windows on SIDE.
        (catch 'found
          (dolist (window windows)
            (setq this-slot (window-parameter window 'window-slot))
            (cond
             ;; The following should not happen and probably be checked
             ;; by window--side-check.
             ((not (numberp this-slot)))
             ((= this-slot slot)
              ;; A window with a matching slot has been found.
              (setq this-window window)
              (throw 'found t))
             (t
              ;; Check if this window has a better slot value wrt the
              ;; slot of the window we want.
              (setq abs-slot
                    (if (or (and (> this-slot 0) (> slot 0))
                            (and (< this-slot 0) (< slot 0)))
                        (abs (- slot this-slot))
                      (+ (abs slot) (abs this-slot))))
              (unless (and best-slot (<= best-slot abs-slot))
                (setq best-window window)
                (setq best-slot abs-slot))
              (cond
               ((<= this-slot slot)
                (setq prev-window window))
               ((not next-window)
                (setq next-window window)))))))

        ;; `this-window' is the first window with the same SLOT.
        ;; `prev-window' is the window with the largest slot < SLOT.  A new
        ;; window will be created after it.
        ;; `next-window' is the window with the smallest slot > SLOT.  A new
        ;; window will be created before it.
        ;; `best-window' is the window with the smallest absolute difference
        ;; of its slot and SLOT.

        ;; Note: We dedicate the window used softly to its buffer to
        ;; avoid that "other" (non-side) buffer display functions steal
        ;; it from us.  This must eventually become customizable via
        ;; ALIST (or, better, avoided in the "other" functions).
        (or (and this-window
                 ;; Reuse `this-window'.
                 (window--display-buffer buffer this-window 'reuse 'side))
            (and (or (not max-slots) (< slots max-slots))
                 (or (and next-window
                          ;; Make new window before `next-window'.
                          (let ((next-side
                                 (if (memq side '(left right)) 'above 'left))
                                (window-combination-resize 'side))
                            (setq window (split-window next-window nil next-side))
                            ;; When the new window is deleted, its space
                            ;; is returned to other side windows.
                            (set-window-parameter
                             window 'delete-window 'delete-side-window)
                            window))
                     (and prev-window
                          ;; Make new window after `prev-window'.
                          (let ((prev-side
                                 (if (memq side '(left right)) 'below 'right))
                                (window-combination-resize 'side))
                            (setq window (split-window prev-window nil prev-side))
                            ;; When the new window is deleted, its space
                            ;; is returned to other side windows.
                            (set-window-parameter
                             window 'delete-window 'delete-side-window)
                            window)))
                   (set-window-parameter window 'window-slot slot)
                   (window--display-buffer buffer window 'window 'side))
            (and best-window
                 ;; Reuse `best-window'.
                 (progn
                   ;; Give best-window the new slot value.
                   (set-window-parameter best-window 'window-slot slot)
                   (window--display-buffer buffer best-window 'reuse 'side)))))))))

(defun window--side-check (&optional frame)
  "Check the side window configuration of FRAME.
FRAME defaults to the selected frame.

A valid side window configuration preserves the following two
invariants:

- If there exists a window whose window-side parameter is
  non-nil, there must exist at least one live window whose
  window-side parameter is nil.

- If a window W has a non-nil window-side parameter (i) it must
  have a parent window and that parent's window-side parameter
  must be either nil or the same as for W, and (ii) any child
  window of W must have the same window-side parameter as W.

If the configuration is invalid, reset the window-side parameters
of all windows on FRAME to nil."
  (let (left top right bottom none side parent parent-side)
    (when (or (catch 'reset
                (walk-window-tree
                 (lambda (window)
                   (setq side (window-parameter window 'window-side))
                   (setq parent (window-parent window))
                   (setq parent-side
                         (and parent (window-parameter parent 'window-side)))
                   ;; The following `cond' seems a bit tedious, but I'd
                   ;; rather stick to using just the stack.
                   (cond
                    (parent-side
                     (when (not (eq parent-side side))
                       ;; A parent whose window-side is non-nil must
                       ;; have a child with the same window-side.
                       (throw 'reset t)))
                    ((not side)
                     (when (window-buffer window)
                       ;; Record that we have at least one non-side,
                       ;; live window.
                       (setq none t)))
                    ((if (memq side '(left top))
                         (window-prev-sibling window)
                       (window-next-sibling window))
                     ;; Left and top major side windows must not have a
                     ;; previous sibling, right and bottom major side
                     ;; windows must not have a next sibling.
                     (throw 'reset t))
                    ;; Now check that there's no more than one major
                    ;; window for any of left, top, right and bottom.
                    ((eq side 'left)
                     (if left (throw 'reset t) (setq left t)))
                    ((eq side 'top)
                     (if top (throw 'reset t) (setq top t)))
                    ((eq side 'right)
                     (if right (throw 'reset t) (setq right t)))
                    ((eq side 'bottom)
                     (if bottom (throw 'reset t) (setq bottom t)))
                    (t 
                     (throw 'reset t))))
                 frame t))
              ;; If there's a side window, there must be at least one
              ;; non-side window.
              (and (or left top right bottom) (not none)))
      (walk-window-tree
       (lambda (window)
         (set-window-parameter window 'window-side nil))
       frame t))))

(defun window--check (&optional frame)
  "Check atomic and side windows on FRAME.
FRAME defaults to the selected frame."
  (window--side-check frame)
  (window--atom-check frame))

;;; Window sizes.
(defvar window-size-fixed nil
  "Non-nil in a buffer means windows displaying the buffer are fixed-size.
If the value is `height', then only the window's height is fixed.
If the value is `width', then only the window's width is fixed.
Any other non-nil value fixes both the width and the height.

Emacs won't change the size of any window displaying that buffer,
unless it has no other choice (like when deleting a neighboring
window).")
(make-variable-buffer-local 'window-size-fixed)

(defun window--size-ignore-p (window ignore)
  "Return non-nil if IGNORE says to ignore size restrictions for WINDOW."
  (if (window-valid-p ignore) (eq window ignore) ignore))

(defun window-min-size (&optional window horizontal ignore)
  "Return the minimum size of WINDOW.
WINDOW must be a valid window and defaults to the selected one.
Optional argument HORIZONTAL non-nil means return the minimum
number of columns of WINDOW; otherwise return the minimum number
of WINDOW's lines.

Optional argument IGNORE, if non-nil, means ignore restrictions
imposed by fixed size windows, `window-min-height' or
`window-min-width' settings.  If IGNORE equals `safe', live
windows may get as small as `window-safe-min-height' lines and
`window-safe-min-width' columns.  If IGNORE is a window, ignore
restrictions for that window only.  Any other non-nil value
means ignore all of the above restrictions for all windows."
  (window--min-size-1
   (window-normalize-window window) horizontal ignore))

(defun window--min-size-1 (window horizontal ignore)
  "Internal function of `window-min-size'."
  (let ((sub (window-child window)))
    (if sub
        (let ((value 0))
          ;; WINDOW is an internal window.
          (if (window-combined-p sub horizontal)
              ;; The minimum size of an iso-combination is the sum of
              ;; the minimum sizes of its child windows.
              (while sub
                (setq value (+ value
                               (window--min-size-1 sub horizontal ignore)))
                (setq sub (window-right sub)))
            ;; The minimum size of an ortho-combination is the maximum of
            ;; the minimum sizes of its child windows.
            (while sub
              (setq value (max value
                               (window--min-size-1 sub horizontal ignore)))
              (setq sub (window-right sub))))
          value)
      (with-current-buffer (window-buffer window)
        (cond
         ((and (not (window--size-ignore-p window ignore))
               (window-size-fixed-p window horizontal))
          ;; The minimum size of a fixed size window is its size.
          (window-total-size window horizontal))
         ((or (eq ignore 'safe) (eq ignore window))
          ;; If IGNORE equals `safe' or WINDOW return the safe values.
          (if horizontal window-safe-min-width window-safe-min-height))
         (horizontal
          ;; For the minimum width of a window take fringes and
          ;; scroll-bars into account.  This is questionable and should
          ;; be removed as soon as we are able to split (and resize)
          ;; windows such that the new (or resized) windows can get a
          ;; size less than the user-specified `window-min-height' and
          ;; `window-min-width'.
          (let ((frame (window-frame window))
                (fringes (window-fringes window))
                (scroll-bars (window-scroll-bars window)))
            (max
             (+ window-safe-min-width
                (ceiling (car fringes) (frame-char-width frame))
                (ceiling (cadr fringes) (frame-char-width frame))
                (cond
                 ((memq (nth 2 scroll-bars) '(left right))
                  (nth 1 scroll-bars))
                 ((memq (frame-parameter frame 'vertical-scroll-bars)
                        '(left right))
                  (ceiling (or (frame-parameter frame 'scroll-bar-width) 14)
                           (frame-char-width)))
                 (t 0)))
             (if (and (not (window--size-ignore-p window ignore))
                      (numberp window-min-width))
                 window-min-width
               0))))
         (t
          ;; For the minimum height of a window take any mode- or
          ;; header-line into account.
          (max (+ window-safe-min-height
                  (if header-line-format 1 0)
                  (if mode-line-format 1 0))
               (if (and (not (window--size-ignore-p window ignore))
                        (numberp window-min-height))
                   window-min-height
                 0))))))))

(defun window-sizable (window delta &optional horizontal ignore)
  "Return DELTA if DELTA lines can be added to WINDOW.
WINDOW must be a valid window and defaults to the selected one.
Optional argument HORIZONTAL non-nil means return DELTA if DELTA
columns can be added to WINDOW.  A return value of zero means
that no lines (or columns) can be added to WINDOW.

This function looks only at WINDOW and, recursively, its child
windows.  The function `window-resizable' looks at other windows
as well.

DELTA positive means WINDOW shall be enlarged by DELTA lines or
columns.  If WINDOW cannot be enlarged by DELTA lines or columns
return the maximum value in the range 0..DELTA by which WINDOW
can be enlarged.

DELTA negative means WINDOW shall be shrunk by -DELTA lines or
columns.  If WINDOW cannot be shrunk by -DELTA lines or columns,
return the minimum value in the range DELTA..0 by which WINDOW
can be shrunk.

Optional argument IGNORE non-nil means ignore restrictions
imposed by fixed size windows, `window-min-height' or
`window-min-width' settings.  If IGNORE equals `safe', live
windows may get as small as `window-safe-min-height' lines and
`window-safe-min-width' columns.  If IGNORE is a window, ignore
restrictions for that window only.  Any other non-nil value means
ignore all of the above restrictions for all windows."
  (setq window (window-normalize-window window))
  (cond
   ((< delta 0)
    (max (- (window-min-size window horizontal ignore)
            (window-total-size window horizontal))
         delta))
   ((window--size-ignore-p window ignore)
    delta)
   ((> delta 0)
    (if (window-size-fixed-p window horizontal)
        0
      delta))
   (t 0)))

(defun window-sizable-p (window delta &optional horizontal ignore)
  "Return t if WINDOW can be resized by DELTA lines.
WINDOW must be a valid window and defaults to the selected one.
For the meaning of the arguments of this function see the
doc-string of `window-sizable'."
  (setq window (window-normalize-window window))
  (if (> delta 0)
      (>= (window-sizable window delta horizontal ignore) delta)
    (<= (window-sizable window delta horizontal ignore) delta)))

(defun window--size-fixed-1 (window horizontal)
  "Internal function for `window-size-fixed-p'."
  (let ((sub (window-child window)))
    (catch 'fixed
      (if sub
          ;; WINDOW is an internal window.
          (if (window-combined-p sub horizontal)
              ;; An iso-combination is fixed size if all its child
              ;; windows are fixed-size.
              (progn
                (while sub
                  (unless (window--size-fixed-1 sub horizontal)
                    ;; We found a non-fixed-size child window, so
                    ;; WINDOW's size is not fixed.
                    (throw 'fixed nil))
                  (setq sub (window-right sub)))
                ;; All child windows are fixed-size, so WINDOW's size is
                ;; fixed.
                (throw 'fixed t))
            ;; An ortho-combination is fixed-size if at least one of its
            ;; child windows is fixed-size.
            (while sub
              (when (window--size-fixed-1 sub horizontal)
                ;; We found a fixed-size child window, so WINDOW's size
                ;; is fixed.
                (throw 'fixed t))
              (setq sub (window-right sub))))
        ;; WINDOW is a live window.
        (with-current-buffer (window-buffer window)
          (if horizontal
              (memq window-size-fixed '(width t))
            (memq window-size-fixed '(height t))))))))

(defun window-size-fixed-p (&optional window horizontal)
  "Return non-nil if WINDOW's height is fixed.
WINDOW must be a valid window and defaults to the selected one.
Optional argument HORIZONTAL non-nil means return non-nil if
WINDOW's width is fixed.

If this function returns nil, this does not necessarily mean that
WINDOW can be resized in the desired direction.  The function
`window-resizable' can tell that."
  (window--size-fixed-1
   (window-normalize-window window) horizontal))

(defun window--min-delta-1 (window delta &optional horizontal ignore trail noup)
  "Internal function for `window-min-delta'."
  (if (not (window-parent window))
      ;; If we can't go up, return zero.
      0
    ;; Else try to find a non-fixed-size sibling of WINDOW.
    (let* ((parent (window-parent window))
           (sub (window-child parent)))
      (catch 'done
        (if (window-combined-p sub horizontal)
            ;; In an iso-combination throw DELTA if we find at least one
            ;; child window and that window is either not fixed-size or
            ;; we can ignore fixed-sizeness.
            (let ((skip (eq trail 'after)))
              (while sub
                (cond
                 ((eq sub window)
                  (setq skip (eq trail 'before)))
                 (skip)
                 ((and (not (window--size-ignore-p window ignore))
                       (window-size-fixed-p sub horizontal)))
                 (t
                  ;; We found a non-fixed-size child window.
                  (throw 'done delta)))
                (setq sub (window-right sub))))
          ;; In an ortho-combination set DELTA to the minimum value by
          ;; which other child windows can shrink.
          (while sub
            (unless (eq sub window)
              (setq delta
                    (min delta
                         (- (window-total-size sub horizontal)
                            (window-min-size sub horizontal ignore)))))
            (setq sub (window-right sub))))
        (if noup
            delta
          (window--min-delta-1 parent delta horizontal ignore trail))))))

(defun window-min-delta (&optional window horizontal ignore trail noup nodown)
  "Return number of lines by which WINDOW can be shrunk.
WINDOW must be a valid window and defaults to the selected one.
Return zero if WINDOW cannot be shrunk.

Optional argument HORIZONTAL non-nil means return number of
columns by which WINDOW can be shrunk.

Optional argument IGNORE non-nil means ignore restrictions
imposed by fixed size windows, `window-min-height' or
`window-min-width' settings.  If IGNORE is a window, ignore
restrictions for that window only.  If IGNORE equals `safe',
live windows may get as small as `window-safe-min-height' lines
and `window-safe-min-width' columns.  Any other non-nil value
means ignore all of the above restrictions for all windows.

Optional argument TRAIL restricts the windows that can be enlarged.
If its value is `before', only windows to the left of or above WINDOW
can be enlarged.  If it is `after', only windows to the right of or
below WINDOW can be enlarged.

Optional argument NOUP non-nil means don't go up in the window
tree, but try to enlarge windows within WINDOW's combination only.

Optional argument NODOWN non-nil means don't check whether WINDOW
itself (and its child windows) can be shrunk; check only whether
at least one other window can be enlarged appropriately."
  (setq window (window-normalize-window window))
  (let ((size (window-total-size window horizontal))
        (minimum (window-min-size window horizontal ignore)))
    (cond
     (nodown
      ;; If NODOWN is t, try to recover the entire size of WINDOW.
      (window--min-delta-1 window size horizontal ignore trail noup))
     ((= size minimum)
      ;; If NODOWN is nil and WINDOW's size is already at its minimum,
      ;; there's nothing to recover.
      0)
     (t
      ;; Otherwise, try to recover whatever WINDOW is larger than its
      ;; minimum size.
      (window--min-delta-1
       window (- size minimum) horizontal ignore trail noup)))))

(defun window--max-delta-1 (window delta &optional horizontal ignore trail noup)
  "Internal function of `window-max-delta'."
  (if (not (window-parent window))
      ;; Can't go up.  Return DELTA.
      delta
    (let* ((parent (window-parent window))
           (sub (window-child parent)))
      (catch 'fixed
        (if (window-combined-p sub horizontal)
            ;; For an iso-combination calculate how much we can get from
            ;; other child windows.
            (let ((skip (eq trail 'after)))
              (while sub
                (cond
                 ((eq sub window)
                  (setq skip (eq trail 'before)))
                 (skip)
                 (t
                  (setq delta
                        (+ delta
                           (- (window-total-size sub horizontal)
                              (window-min-size sub horizontal ignore))))))
                (setq sub (window-right sub))))
          ;; For an ortho-combination throw DELTA when at least one
          ;; child window is fixed-size.
          (while sub
            (when (and (not (eq sub window))
                       (not (window--size-ignore-p sub ignore))
                       (window-size-fixed-p sub horizontal))
              (throw 'fixed delta))
            (setq sub (window-right sub))))
        (if noup
            ;; When NOUP is nil, DELTA is all we can get.
            delta
          ;; Else try with parent of WINDOW, passing the DELTA we
          ;; recovered so far.
          (window--max-delta-1 parent delta horizontal ignore trail))))))

(defun window-max-delta (&optional window horizontal ignore trail noup nodown)
  "Return maximum number of lines by which WINDOW can be enlarged.
WINDOW must be a valid window and defaults to the selected one.
The return value is zero if WINDOW cannot be enlarged.

Optional argument HORIZONTAL non-nil means return maximum number
of columns by which WINDOW can be enlarged.

Optional argument IGNORE non-nil means ignore restrictions
imposed by fixed size windows, `window-min-height' or
`window-min-width' settings.  If IGNORE is a window, ignore
restrictions for that window only.  If IGNORE equals `safe',
live windows may get as small as `window-safe-min-height' lines
and `window-safe-min-width' columns.  Any other non-nil value means
ignore all of the above restrictions for all windows.

Optional argument TRAIL restricts the windows that can be enlarged.
If its value is `before', only windows to the left of or above WINDOW
can be enlarged.  If it is `after', only windows to the right of or
below WINDOW can be enlarged.

Optional argument NOUP non-nil means don't go up in the window
tree but try to obtain the entire space from windows within
WINDOW's combination.

Optional argument NODOWN non-nil means do not check whether
WINDOW itself (and its child windows) can be enlarged; check
only whether other windows can be shrunk appropriately."
  (setq window (window-normalize-window window))
  (if (and (not (window--size-ignore-p window ignore))
           (not nodown) (window-size-fixed-p window horizontal))
      ;; With IGNORE and NOWDON nil return zero if WINDOW has fixed
      ;; size.
      0
    ;; WINDOW has no fixed size.
    (window--max-delta-1 window 0 horizontal ignore trail noup)))

;; Make NOUP also inhibit the min-size check.
(defun window--resizable (window delta &optional horizontal ignore trail noup nodown)
  "Return DELTA if WINDOW can be resized vertically by DELTA lines.
WINDOW must be a valid window and defaults to the selected one.
Optional argument HORIZONTAL non-nil means return DELTA if WINDOW
can be resized horizontally by DELTA columns.  A return value of
zero means that WINDOW is not resizable.

DELTA positive means WINDOW shall be enlarged by DELTA lines or
columns.  If WINDOW cannot be enlarged by DELTA lines or columns,
return the maximum value in the range 0..DELTA by which WINDOW
can be enlarged.

DELTA negative means WINDOW shall be shrunk by -DELTA lines or
columns.  If WINDOW cannot be shrunk by -DELTA lines or columns,
return the minimum value in the range DELTA..0 that can be used
for shrinking WINDOW.

Optional argument IGNORE non-nil means ignore restrictions
imposed by fixed size windows, `window-min-height' or
`window-min-width' settings.  If IGNORE is a window, ignore
restrictions for that window only.  If IGNORE equals `safe',
live windows may get as small as `window-safe-min-height' lines
and `window-safe-min-width' columns.  Any other non-nil value
means ignore all of the above restrictions for all windows.

Optional argument TRAIL `before' means only windows to the left
of or below WINDOW can be shrunk.  Optional argument TRAIL
`after' means only windows to the right of or above WINDOW can be
shrunk.

Optional argument NOUP non-nil means don't go up in the window
tree but check only whether space can be obtained from (or given
to) WINDOW's siblings.

Optional argument NODOWN non-nil means don't go down in the
window tree.  This means do not check whether resizing would
violate size restrictions of WINDOW or its child windows."
  (setq window (window-normalize-window window))
  (cond
   ((< delta 0)
    (max (- (window-min-delta window horizontal ignore trail noup nodown))
         delta))
   ((> delta 0)
    (min (window-max-delta window horizontal ignore trail noup nodown)
         delta))
   (t 0)))

(defun window--resizable-p (window delta &optional horizontal ignore trail noup nodown)
  "Return t if WINDOW can be resized vertically by DELTA lines.
WINDOW must be a valid window and defaults to the selected one.
For the meaning of the arguments of this function see the
doc-string of `window--resizable'."
  (setq window (window-normalize-window window))
  (if (> delta 0)
      (>= (window--resizable window delta horizontal ignore trail noup nodown)
          delta)
    (<= (window--resizable window delta horizontal ignore trail noup nodown)
        delta)))

(defun window-resizable (window delta &optional horizontal ignore)
  "Return DELTA if WINDOW can be resized vertically by DELTA lines.
WINDOW must be a valid window and defaults to the selected one.
Optional argument HORIZONTAL non-nil means return DELTA if WINDOW
can be resized horizontally by DELTA columns.  A return value of
zero means that WINDOW is not resizable.

DELTA positive means WINDOW shall be enlarged by DELTA lines or
columns.  If WINDOW cannot be enlarged by DELTA lines or columns
return the maximum value in the range 0..DELTA by which WINDOW
can be enlarged.

DELTA negative means WINDOW shall be shrunk by -DELTA lines or
columns.  If WINDOW cannot be shrunk by -DELTA lines or columns,
return the minimum value in the range DELTA..0 that can be used
for shrinking WINDOW.

Optional argument IGNORE non-nil means ignore restrictions
imposed by fixed size windows, `window-min-height' or
`window-min-width' settings.  If IGNORE is a window, ignore
restrictions for that window only.  If IGNORE equals `safe',
live windows may get as small as `window-safe-min-height' lines
and `window-safe-min-width' columns.  Any other non-nil value
means ignore all of the above restrictions for all windows."
  (setq window (window-normalize-window window))
  (window--resizable window delta horizontal ignore))

(defun window-total-size (&optional window horizontal)
  "Return the total height or width of WINDOW.
WINDOW must be a valid window and defaults to the selected one.

If HORIZONTAL is omitted or nil, return the total height of
WINDOW, in lines, like `window-total-height'.  Otherwise return
the total width, in columns, like `window-total-width'."
  (if horizontal
      (window-total-width window)
    (window-total-height window)))

;; Eventually we should make `window-height' obsolete.
(defalias 'window-height 'window-total-height)

;; See discussion in bug#4543.
(defun window-full-height-p (&optional window)
  "Return t if WINDOW is as high as its containing frame.
More precisely, return t if and only if the total height of
WINDOW equals the total height of the root window of WINDOW's
frame.  WINDOW must be a valid window and defaults to the
selected one."
  (setq window (window-normalize-window window))
  (= (window-total-size window)
     (window-total-size (frame-root-window window))))

(defun window-full-width-p (&optional window)
  "Return t if WINDOW is as wide as its containing frame.
More precisely, return t if and only if the total width of WINDOW
equals the total width of the root window of WINDOW's frame.
WINDOW must be a valid window and defaults to the selected one."
  (setq window (window-normalize-window window))
  (= (window-total-size window t)
     (window-total-size (frame-root-window window) t)))

(defun window-body-size (&optional window horizontal)
  "Return the height or width of WINDOW's text area.
WINDOW must be a live window and defaults to the selected one.

If HORIZONTAL is omitted or nil, return the height of the text
area, like `window-body-height'.  Otherwise, return the width of
the text area, like `window-body-width'."
  (if horizontal
      (window-body-width window)
    (window-body-height window)))

;; Eventually we should make `window-height' obsolete.
(defalias 'window-width 'window-body-width)

(defun window-current-scroll-bars (&optional window)
  "Return the current scroll bar settings for WINDOW.
WINDOW must be a live window and defaults to the selected one.

The return value is a cons cell (VERTICAL . HORIZONTAL) where
VERTICAL specifies the current location of the vertical scroll
bars (`left', `right', or nil), and HORIZONTAL specifies the
current location of the horizontal scroll bars (`top', `bottom',
or nil).

Unlike `window-scroll-bars', this function reports the scroll bar
type actually used, once frame defaults and `scroll-bar-mode' are
taken into account."
  (setq window (window-normalize-window window t))
  (let ((vert (nth 2 (window-scroll-bars window)))
        (hor nil))
    (when (or (eq vert t) (eq hor t))
      (let ((fcsb (frame-current-scroll-bars (window-frame window))))
        (if (eq vert t)
            (setq vert (car fcsb)))
        (if (eq hor t)
            (setq hor (cdr fcsb)))))
    (cons vert hor)))

(defun walk-windows (fun &optional minibuf all-frames)
  "Cycle through all live windows, calling FUN for each one.
FUN must specify a function with a window as its sole argument.
The optional arguments MINIBUF and ALL-FRAMES specify the set of
windows to include in the walk.

MINIBUF t means include the minibuffer window even if the
minibuffer is not active.  MINIBUF nil or omitted means include
the minibuffer window only if the minibuffer is active.  Any
other value means do not include the minibuffer window even if
the minibuffer is active.

ALL-FRAMES nil or omitted means consider all windows on the
selected frame, plus the minibuffer window if specified by the
MINIBUF argument.  If the minibuffer counts, consider all windows
on all frames that share that minibuffer too.  The following
non-nil values of ALL-FRAMES have special meanings:

- t means consider all windows on all existing frames.

- `visible' means consider all windows on all visible frames on
  the current terminal.

- 0 (the number zero) means consider all windows on all visible
  and iconified frames on the current terminal.

- A frame means consider all windows on that frame only.

Anything else means consider all windows on the selected frame
and no others.

This function changes neither the order of recently selected
windows nor the buffer list."
  ;; If we start from the minibuffer window, don't fail to come
  ;; back to it.
  (when (window-minibuffer-p (selected-window))
    (setq minibuf t))
  ;; Make sure to not mess up the order of recently selected
  ;; windows.  Use `save-selected-window' and `select-window'
  ;; with second argument non-nil for this purpose.
  (save-selected-window
    (when (framep all-frames)
      (select-window (frame-first-window all-frames) 'norecord))
    (dolist (walk-windows-window (window-list-1 nil minibuf all-frames))
      (funcall fun walk-windows-window))))

(defun window-at-side-p (&optional window side)
  "Return t if WINDOW is at SIDE of its containing frame.
WINDOW must be a valid window and defaults to the selected one.
SIDE can be any of the symbols `left', `top', `right' or
`bottom'.  The default value nil is handled like `bottom'."
  (setq window (window-normalize-window window))
  (let ((edge
         (cond
          ((eq side 'left) 0)
          ((eq side 'top) 1)
          ((eq side 'right) 2)
          ((memq side '(bottom nil)) 3))))
    (= (nth edge (window-edges window))
       (nth edge (window-edges (frame-root-window window))))))

(defun window-at-side-list (&optional frame side)
  "Return list of all windows on SIDE of FRAME.
FRAME must be a live frame and defaults to the selected frame.
SIDE can be any of the symbols `left', `top', `right' or
`bottom'.  The default value nil is handled like `bottom'."
  (setq frame (window-normalize-frame frame))
  (let (windows)
    (walk-window-tree
     (lambda (window)
       (when (window-at-side-p window side)
         (setq windows (cons window windows))))
     frame nil 'nomini)
    (nreverse windows)))

(defun window--in-direction-2 (window posn &optional horizontal)
  "Support function for `window-in-direction'."
  (if horizontal
      (let ((top (window-top-line window)))
        (if (> top posn)
            (- top posn)
          (- posn top (window-total-height window))))
    (let ((left (window-left-column window)))
      (if (> left posn)
          (- left posn)
        (- posn left (window-total-width window))))))

;; Predecessors to the below have been devised by Julian Assange in
;; change-windows-intuitively.el and Hovav Shacham in windmove.el.
;; Neither of these allow to selectively ignore specific windows
;; (windows whose `no-other-window' parameter is non-nil) as targets of
;; the movement.
(defun window-in-direction (direction &optional window ignore)
  "Return window in DIRECTION as seen from WINDOW.
More precisely, return the nearest window in direction DIRECTION
as seen from the position of `window-point' in window WINDOW.
DIRECTION must be one of `above', `below', `left' or `right'.
WINDOW must be a live window and defaults to the selected one.

Do not return a window whose `no-other-window' parameter is
non-nil.  If the nearest window's `no-other-window' parameter is
non-nil, try to find another window in the indicated direction.
If, however, the optional argument IGNORE is non-nil, return that
window even if its `no-other-window' parameter is non-nil.

Return nil if no suitable window can be found."
  (setq window (window-normalize-window window t))
  (unless (memq direction '(above below left right))
    (error "Wrong direction %s" direction))
  (let* ((frame (window-frame window))
         (hor (memq direction '(left right)))
         (first (if hor
                    (window-left-column window)
                  (window-top-line window)))
         (last (+ first (if hor
                            (window-total-width window)
                          (window-total-height window))))
         (posn-cons (nth 6 (posn-at-point (window-point window) window)))
         ;; The column / row value of `posn-at-point' can be nil for the
         ;; mini-window, guard against that.
         (posn (if hor
                   (+ (or (cdr posn-cons) 1) (window-top-line window))
                 (+ (or (car posn-cons) 1) (window-left-column window))))
         (best-edge
          (cond
           ((eq direction 'below) (frame-height frame))
           ((eq direction 'right) (frame-width frame))
           (t -1)))
         (best-edge-2 best-edge)
         (best-diff-2 (if hor (frame-height frame) (frame-width frame)))
         best best-2 best-diff-2-new)
    (walk-window-tree
     (lambda (w)
       (let* ((w-top (window-top-line w))
              (w-left (window-left-column w)))
         (cond
          ((or (eq window w)
               ;; Ignore ourselves.
               (and (window-parameter w 'no-other-window)
                    ;; Ignore W unless IGNORE is non-nil.
                    (not ignore))))
          (hor
           (cond
            ((and (<= w-top posn)
                  (< posn (+ w-top (window-total-height w))))
             ;; W is to the left or right of WINDOW and covers POSN.
             (when (or (and (eq direction 'left)
                            (<= w-left first) (> w-left best-edge))
                       (and (eq direction 'right)
                            (>= w-left last) (< w-left best-edge)))
               (setq best-edge w-left)
               (setq best w)))
            ((and (or (and (eq direction 'left)
                           (<= (+ w-left (window-total-width w)) first))
                      (and (eq direction 'right) (<= last w-left)))
                  ;; W is to the left or right of WINDOW but does not
                  ;; cover POSN.
                  (setq best-diff-2-new
                        (window--in-direction-2 w posn hor))
                  (or (< best-diff-2-new best-diff-2)
                      (and (= best-diff-2-new best-diff-2)
                           (if (eq direction 'left)
                               (> w-left best-edge-2)
                             (< w-left best-edge-2)))))
             (setq best-edge-2 w-left)
             (setq best-diff-2 best-diff-2-new)
             (setq best-2 w))))
          (t
           (cond
            ((and (<= w-left posn)
                  (< posn (+ w-left (window-total-width w))))
             ;; W is above or below WINDOW and covers POSN.
             (when (or (and (eq direction 'above)
                            (<= w-top first) (> w-top best-edge))
                       (and (eq direction 'below)
                            (>= w-top first) (< w-top best-edge)))
               (setq best-edge w-top)
               (setq best w)))
            ((and (or (and (eq direction 'above)
                           (<= (+ w-top (window-total-height w)) first))
                      (and (eq direction 'below) (<= last w-top)))
                  ;; W is above or below WINDOW but does not cover POSN.
                  (setq best-diff-2-new
                        (window--in-direction-2 w posn hor))
                  (or (< best-diff-2-new best-diff-2)
                      (and (= best-diff-2-new best-diff-2)
                           (if (eq direction 'above)
                               (> w-top best-edge-2)
                             (< w-top best-edge-2)))))
             (setq best-edge-2 w-top)
             (setq best-diff-2 best-diff-2-new)
             (setq best-2 w)))))))
     frame)
    (or best best-2)))

(defun get-window-with-predicate (predicate &optional minibuf all-frames default)
  "Return a live window satisfying PREDICATE.
More precisely, cycle through all windows calling the function
PREDICATE on each one of them with the window as its sole
argument.  Return the first window for which PREDICATE returns
non-nil.  Windows are scanned starting with the window following
the selected window.  If no window satisfies PREDICATE, return
DEFAULT.

MINIBUF t means include the minibuffer window even if the
minibuffer is not active.  MINIBUF nil or omitted means include
the minibuffer window only if the minibuffer is active.  Any
other value means do not include the minibuffer window even if
the minibuffer is active.

ALL-FRAMES nil or omitted means consider all windows on the selected
frame, plus the minibuffer window if specified by the MINIBUF
argument.  If the minibuffer counts, consider all windows on all
frames that share that minibuffer too.  The following non-nil
values of ALL-FRAMES have special meanings:

- t means consider all windows on all existing frames.

- `visible' means consider all windows on all visible frames on
  the current terminal.

- 0 (the number zero) means consider all windows on all visible
  and iconified frames on the current terminal.

- A frame means consider all windows on that frame only.

Anything else means consider all windows on the selected frame
and no others."
  (catch 'found
    (dolist (window (window-list-1
                     (next-window nil minibuf all-frames)
                     minibuf all-frames))
      (when (funcall predicate window)
        (throw 'found window)))
    default))

(defalias 'some-window 'get-window-with-predicate)

(defun get-lru-window (&optional all-frames dedicated not-selected)
   "Return the least recently used window on frames specified by ALL-FRAMES.
Return a full-width window if possible.  A minibuffer window is
never a candidate.  A dedicated window is never a candidate
unless DEDICATED is non-nil, so if all windows are dedicated, the
value is nil.  Avoid returning the selected window if possible.
Optional argument NOT-SELECTED non-nil means never return the
selected window.

The following non-nil values of the optional argument ALL-FRAMES
have special meanings:

- t means consider all windows on all existing frames.

- `visible' means consider all windows on all visible frames on
  the current terminal.

- 0 (the number zero) means consider all windows on all visible
  and iconified frames on the current terminal.

- A frame means consider all windows on that frame only.

Any other value of ALL-FRAMES means consider all windows on the
selected frame and no others."
   (let (best-window best-time second-best-window second-best-time time)
    (dolist (window (window-list-1 nil 'nomini all-frames))
      (when (and (or dedicated (not (window-dedicated-p window)))
                 (or (not not-selected) (not (eq window (selected-window)))))
        (setq time (window-use-time window))
        (if (or (eq window (selected-window))
                (not (window-full-width-p window)))
            (when (or (not second-best-time) (< time second-best-time))
              (setq second-best-time time)
              (setq second-best-window window))
          (when (or (not best-time) (< time best-time))
            (setq best-time time)
            (setq best-window window)))))
    (or best-window second-best-window)))

(defun get-mru-window (&optional all-frames dedicated not-selected)
   "Return the most recently used window on frames specified by ALL-FRAMES.
A minibuffer window is never a candidate.  A dedicated window is
never a candidate unless DEDICATED is non-nil, so if all windows
are dedicated, the value is nil.  Optional argument NOT-SELECTED
non-nil means never return the selected window.

The following non-nil values of the optional argument ALL-FRAMES
have special meanings:

- t means consider all windows on all existing frames.

- `visible' means consider all windows on all visible frames on
  the current terminal.

- 0 (the number zero) means consider all windows on all visible
  and iconified frames on the current terminal.

- A frame means consider all windows on that frame only.

Any other value of ALL-FRAMES means consider all windows on the
selected frame and no others."
   (let (best-window best-time time)
    (dolist (window (window-list-1 nil 'nomini all-frames))
      (setq time (window-use-time window))
      (when (and (or dedicated (not (window-dedicated-p window)))
                 (or (not not-selected) (not (eq window (selected-window))))
                 (or (not best-time) (> time best-time)))
        (setq best-time time)
        (setq best-window window)))
    best-window))

(defun get-largest-window (&optional all-frames dedicated not-selected)
  "Return the largest window on frames specified by ALL-FRAMES.
A minibuffer window is never a candidate.  A dedicated window is
never a candidate unless DEDICATED is non-nil, so if all windows
are dedicated, the value is nil.  Optional argument NOT-SELECTED
non-nil means never return the selected window.

The following non-nil values of the optional argument ALL-FRAMES
have special meanings:

- t means consider all windows on all existing frames.

- `visible' means consider all windows on all visible frames on
  the current terminal.

- 0 (the number zero) means consider all windows on all visible
  and iconified frames on the current terminal.

- A frame means consider all windows on that frame only.

Any other value of ALL-FRAMES means consider all windows on the
selected frame and no others."
  (let ((best-size 0)
        best-window size)
    (dolist (window (window-list-1 nil 'nomini all-frames))
      (when (and (or dedicated (not (window-dedicated-p window)))
                 (or (not not-selected) (not (eq window (selected-window)))))
        (setq size (* (window-total-size window)
                      (window-total-size window t)))
        (when (> size best-size)
          (setq best-size size)
          (setq best-window window))))
    best-window))

(defun get-buffer-window-list (&optional buffer-or-name minibuf all-frames)
  "Return list of all windows displaying BUFFER-OR-NAME, or nil if none.
BUFFER-OR-NAME may be a buffer or the name of an existing buffer
and defaults to the current buffer.  Windows are scanned starting
with the selected window.

MINIBUF t means include the minibuffer window even if the
minibuffer is not active.  MINIBUF nil or omitted means include
the minibuffer window only if the minibuffer is active.  Any
other value means do not include the minibuffer window even if
the minibuffer is active.

ALL-FRAMES nil or omitted means consider all windows on the
selected frame, plus the minibuffer window if specified by the
MINIBUF argument.  If the minibuffer counts, consider all windows
on all frames that share that minibuffer too.  The following
non-nil values of ALL-FRAMES have special meanings:

- t means consider all windows on all existing frames.

- `visible' means consider all windows on all visible frames on
  the current terminal.

- 0 (the number zero) means consider all windows on all visible
  and iconified frames on the current terminal.

- A frame means consider all windows on that frame only.

Anything else means consider all windows on the selected frame
and no others."
  (let ((buffer (window-normalize-buffer buffer-or-name))
        windows)
    (dolist (window (window-list-1 (selected-window) minibuf all-frames))
      (when (eq (window-buffer window) buffer)
        (setq windows (cons window windows))))
    (nreverse windows)))

(defun minibuffer-window-active-p (window)
  "Return t if WINDOW is the currently active minibuffer window."
  (eq window (active-minibuffer-window)))

(defun count-windows (&optional minibuf)
   "Return the number of live windows on the selected frame.
The optional argument MINIBUF specifies whether the minibuffer
window shall be counted.  See `walk-windows' for the precise
meaning of this argument."
   (length (window-list-1 nil minibuf)))
\f
;;; Resizing windows.
(defun window--resize-reset (&optional frame horizontal)
  "Reset resize values for all windows on FRAME.
FRAME defaults to the selected frame.

This function stores the current value of `window-total-size' applied
with argument HORIZONTAL in the new total size of all windows on
FRAME.  It also resets the new normal size of each of these
windows."
  (window--resize-reset-1
   (frame-root-window (window-normalize-frame frame)) horizontal))

(defun window--resize-reset-1 (window horizontal)
  "Internal function of `window--resize-reset'."
  ;; Register old size in the new total size.
  (set-window-new-total window (window-total-size window horizontal))
  ;; Reset new normal size.
  (set-window-new-normal window)
  (when (window-child window)
    (window--resize-reset-1 (window-child window) horizontal))
  (when (window-right window)
    (window--resize-reset-1 (window-right window) horizontal)))

;; The following routine is used to manually resize the minibuffer
;; window and is currently used, for example, by ispell.el.
(defun window--resize-mini-window (window delta)
  "Resize minibuffer window WINDOW by DELTA lines.
If WINDOW cannot be resized by DELTA lines make it as large (or
as small) as possible, but don't signal an error."
  (when (window-minibuffer-p window)
    (let* ((frame (window-frame window))
           (root (frame-root-window frame))
           (height (window-total-size window))
           (min-delta
            (- (window-total-size root)
               (window-min-size root))))
      ;; Sanitize DELTA.
      (cond
       ((<= (+ height delta) 0)
        (setq delta (- (- height 1))))
       ((> delta min-delta)
        (setq delta min-delta)))

      ;; Resize now.
      (window--resize-reset frame)
      ;; Ideally we should be able to resize just the last child of root
      ;; here.  See the comment in `resize-root-window-vertically' for
      ;; why we do not do that.
      (window--resize-this-window root (- delta) nil nil t)
      (set-window-new-total window (+ height delta))
      ;; The following routine catches the case where we want to resize
      ;; a minibuffer-only frame.
      (resize-mini-window-internal window))))

(defun window-resize (window delta &optional horizontal ignore)
  "Resize WINDOW vertically by DELTA lines.
WINDOW can be an arbitrary window and defaults to the selected
one.  An attempt to resize the root window of a frame will raise
an error though.

DELTA a positive number means WINDOW shall be enlarged by DELTA
lines.  DELTA negative means WINDOW shall be shrunk by -DELTA
lines.

Optional argument HORIZONTAL non-nil means resize WINDOW
horizontally by DELTA columns.  In this case a positive DELTA
means enlarge WINDOW by DELTA columns.  DELTA negative means
WINDOW shall be shrunk by -DELTA columns.

Optional argument IGNORE non-nil means ignore restrictions
imposed by fixed size windows, `window-min-height' or
`window-min-width' settings.  If IGNORE is a window, ignore
restrictions for that window only.  If IGNORE equals `safe',
live windows may get as small as `window-safe-min-height' lines
and `window-safe-min-width' columns.  Any other non-nil value
means ignore all of the above restrictions for all windows.

This function resizes other windows proportionally and never
deletes any windows.  If you want to move only the low (right)
edge of WINDOW consider using `adjust-window-trailing-edge'
instead."
  (setq window (window-normalize-window window))
  (let* ((frame (window-frame window))
         (minibuffer-window (minibuffer-window frame))
         sibling)
    (cond
     ((eq window (frame-root-window frame))
      (error "Cannot resize the root window of a frame"))
     ((window-minibuffer-p window)
      (if horizontal
          (error "Cannot resize minibuffer window horizontally")
        (window--resize-mini-window window delta)))
     ((and (not horizontal)
           (window-full-height-p window)
           (eq (window-frame minibuffer-window) frame)
           (or (not resize-mini-windows)
               (eq minibuffer-window (active-minibuffer-window))))
      ;; If WINDOW is full height and either `resize-mini-windows' is
      ;; nil or the minibuffer window is active, resize the minibuffer
      ;; window.
      (window--resize-mini-window minibuffer-window (- delta)))
     ((window--resizable-p window delta horizontal ignore)
      (window--resize-reset frame horizontal)
      (window--resize-this-window window delta horizontal ignore t)
      (if (and (not window-combination-resize)
               (window-combined-p window horizontal)
               (setq sibling (or (window-right window) (window-left window)))
               (window-sizable-p sibling (- delta) horizontal ignore))
          ;; If window-combination-resize is nil, WINDOW is part of an
          ;; iso-combination, and WINDOW's neighboring right or left
          ;; sibling can be resized as requested, resize that sibling.
          (let ((normal-delta
                 (/ (float delta)
                    (window-total-size (window-parent window) horizontal))))
            (window--resize-this-window sibling (- delta) horizontal nil t)
            (set-window-new-normal
             window (+ (window-normal-size window horizontal)
                       normal-delta))
            (set-window-new-normal
             sibling (- (window-normal-size sibling horizontal)
                        normal-delta)))
        ;; Otherwise, resize all other windows in the same combination.
        (window--resize-siblings window delta horizontal ignore))
      (window-resize-apply frame horizontal))
     (t
      (error "Cannot resize window %s" window)))))

(defun window--resize-child-windows-skip-p (window)
  "Return non-nil if WINDOW shall be skipped by resizing routines."
  (memq (window-new-normal window) '(ignore stuck skip)))

(defun window--resize-child-windows-normal (parent horizontal window this-delta &optional trail other-delta)
  "Recursively set new normal height of child windows of window PARENT.
HORIZONTAL non-nil means set the new normal width of these
windows.  WINDOW specifies a child window of PARENT that has been
resized by THIS-DELTA lines (columns).

Optional argument TRAIL either `before' or `after' means set values
only for windows before or after WINDOW.  Optional argument
OTHER-DELTA, a number, specifies that this many lines (columns)
have been obtained from (or returned to) an ancestor window of
PARENT in order to resize WINDOW."
  (let* ((delta-normal
          (if (and (= (- this-delta) (window-total-size window horizontal))
                   (zerop other-delta))
              ;; When WINDOW gets deleted and we can return its entire
              ;; space to its siblings, use WINDOW's normal size as the
              ;; normal delta.
              (- (window-normal-size window horizontal))
            ;; In any other case calculate the normal delta from the
            ;; relation of THIS-DELTA to the total size of PARENT.
            (/ (float this-delta) (window-total-size parent horizontal))))
         (sub (window-child parent))
         (parent-normal 0.0)
         (skip (eq trail 'after)))

    ;; Set parent-normal to the sum of the normal sizes of all child
    ;; windows of PARENT that shall be resized, excluding only WINDOW
    ;; and any windows specified by the optional TRAIL argument.
    (while sub
      (cond
       ((eq sub window)
        (setq skip (eq trail 'before)))
       (skip)
       (t
        (setq parent-normal
              (+ parent-normal (window-normal-size sub horizontal)))))
      (setq sub (window-right sub)))

    ;; Set the new normal size of all child windows of PARENT from what
    ;; they should have contributed for recovering THIS-DELTA lines
    ;; (columns).
    (setq sub (window-child parent))
    (setq skip (eq trail 'after))
    (while sub
      (cond
       ((eq sub window)
        (setq skip (eq trail 'before)))
       (skip)
       (t
        (let ((old-normal (window-normal-size sub horizontal)))
          (set-window-new-normal
           sub (min 1.0 ; Don't get larger than 1.
                    (max (- old-normal
                            (* (/ old-normal parent-normal)
                               delta-normal))
                         ;; Don't drop below 0.
                         0.0))))))
      (setq sub (window-right sub)))

    (when (numberp other-delta)
      ;; Set the new normal size of windows from what they should have
      ;; contributed for recovering OTHER-DELTA lines (columns).
      (setq delta-normal (/ (float (window-total-size parent horizontal))
                            (+ (window-total-size parent horizontal)
                               other-delta)))
      (setq sub (window-child parent))
      (setq skip (eq trail 'after))
      (while sub
        (cond
         ((eq sub window)
          (setq skip (eq trail 'before)))
         (skip)
         (t
          (set-window-new-normal
           sub (min 1.0 ; Don't get larger than 1.
                    (max (* (window-new-normal sub) delta-normal)
                         ;; Don't drop below 0.
                         0.0)))))
        (setq sub (window-right sub))))

    ;; Set the new normal size of WINDOW to what is left by the sum of
    ;; the normal sizes of its siblings.
    (set-window-new-normal
     window
     (let ((sum 0))
       (setq sub (window-child parent))
       (while sub
         (cond
          ((eq sub window))
          ((not (numberp (window-new-normal sub)))
           (setq sum (+ sum (window-normal-size sub horizontal))))
          (t
           (setq sum (+ sum (window-new-normal sub)))))
         (setq sub (window-right sub)))
       ;; Don't get larger than 1 or smaller than 0.
       (min 1.0 (max (- 1.0 sum) 0.0))))))

(defun window--resize-child-windows (parent delta &optional horizontal window ignore trail edge)
  "Resize child windows of window PARENT vertically by DELTA lines.
PARENT must be a vertically combined internal window.

Optional argument HORIZONTAL non-nil means resize child windows of
PARENT horizontally by DELTA columns.  In this case PARENT must
be a horizontally combined internal window.

WINDOW, if specified, must denote a child window of PARENT that
is resized by DELTA lines.

Optional argument IGNORE non-nil means ignore restrictions
imposed by fixed size windows, `window-min-height' or
`window-min-width' settings.  If IGNORE equals `safe', live
windows may get as small as `window-safe-min-height' lines and
`window-safe-min-width' columns.  If IGNORE is a window, ignore
restrictions for that window only.  Any other non-nil value means
ignore all of the above restrictions for all windows.

Optional arguments TRAIL and EDGE, when non-nil, restrict the set
of windows that shall be resized.  If TRAIL equals `before',
resize only windows on the left or above EDGE.  If TRAIL equals
`after', resize only windows on the right or below EDGE.  Also,
preferably only resize windows adjacent to EDGE.

Return the symbol `normalized' if new normal sizes have been
already set by this routine."
  (let* ((first (window-child parent))
         (sub first)
         (parent-total (+ (window-total-size parent horizontal) delta))
         best-window best-value)

    (if (and edge (memq trail '(before after))
             (progn
               (setq sub first)
               (while (and (window-right sub)
                           (or (and (eq trail 'before)
                                    (not (window--resize-child-windows-skip-p
                                          (window-right sub))))
                               (and (eq trail 'after)
                                    (window--resize-child-windows-skip-p sub))))
                 (setq sub (window-right sub)))
               sub)
             (if horizontal
                 (if (eq trail 'before)
                     (= (+ (window-left-column sub)
                           (window-total-size sub t))
                        edge)
                   (= (window-left-column sub) edge))
               (if (eq trail 'before)
                   (= (+ (window-top-line sub)
                         (window-total-size sub))
                      edge)
                 (= (window-top-line sub) edge)))
             (window-sizable-p sub delta horizontal ignore))
        ;; Resize only windows adjacent to EDGE.
        (progn
          (window--resize-this-window
           sub delta horizontal ignore t trail edge)
          (if (and window (eq (window-parent sub) parent))
              (progn
                ;; Assign new normal sizes.
                (set-window-new-normal
                 sub (/ (float (window-new-total sub)) parent-total))
                (set-window-new-normal
                 window (- (window-normal-size window horizontal)
                           (- (window-new-normal sub)
                              (window-normal-size sub horizontal)))))
            (window--resize-child-windows-normal
             parent horizontal sub 0 trail delta))
          ;; Return 'normalized to notify `window--resize-siblings' that
          ;; normal sizes have been already set.
          'normalized)
      ;; Resize all windows proportionally.
      (setq sub first)
      (while sub
        (cond
         ((or (window--resize-child-windows-skip-p sub)
              ;; Ignore windows to skip and fixed-size child windows -
              ;; in the latter case make it a window to skip.
              (and (not ignore)
                   (window-size-fixed-p sub horizontal)
                   (set-window-new-normal sub 'ignore))))
         ((< delta 0)
          ;; When shrinking store the number of lines/cols we can get
          ;; from this window here together with the total/normal size
          ;; factor.
          (set-window-new-normal
           sub
           (cons
            ;; We used to call this with NODOWN t, "fixed" 2011-05-11.
            (window-min-delta sub horizontal ignore trail t) ; t)
            (- (/ (float (window-total-size sub horizontal))
                  parent-total)
               (window-normal-size sub horizontal)))))
         ((> delta 0)
          ;; When enlarging store the total/normal size factor only
          (set-window-new-normal
           sub
           (- (/ (float (window-total-size sub horizontal))
                 parent-total)
              (window-normal-size sub horizontal)))))

        (setq sub (window-right sub)))

      (cond
       ((< delta 0)
        ;; Shrink windows by delta.
        (setq best-window t)
        (while (and best-window (not (zerop delta)))
          (setq sub first)
          (setq best-window nil)
          (setq best-value most-negative-fixnum)
          (while sub
            (when (and (consp (window-new-normal sub))
                       (not (zerop (car (window-new-normal sub))))
                       (> (cdr (window-new-normal sub)) best-value))
              (setq best-window sub)
              (setq best-value (cdr (window-new-normal sub))))

            (setq sub (window-right sub)))

          (when best-window
            (setq delta (1+ delta)))
          (set-window-new-total best-window -1 t)
          (set-window-new-normal
           best-window
           (if (= (car (window-new-normal best-window)) 1)
               'skip ; We can't shrink best-window any further.
             (cons (1- (car (window-new-normal best-window)))
                   (- (/ (float (window-new-total best-window))
                         parent-total)
                      (window-normal-size best-window horizontal)))))))
       ((> delta 0)
        ;; Enlarge windows by delta.
        (setq best-window t)
        (while (and best-window (not (zerop delta)))
          (setq sub first)
          (setq best-window nil)
          (setq best-value most-positive-fixnum)
          (while sub
            (when (and (numberp (window-new-normal sub))
                       (< (window-new-normal sub) best-value))
              (setq best-window sub)
              (setq best-value (window-new-normal sub)))

            (setq sub (window-right sub)))

          (when best-window
            (setq delta (1- delta)))
          (set-window-new-total best-window 1 t)
          (set-window-new-normal
           best-window
           (- (/ (float (window-new-total best-window))
                 parent-total)
              (window-normal-size best-window horizontal))))))

      (when best-window
        (setq sub first)
        (while sub
          (when (or (consp (window-new-normal sub))
                    (numberp (window-new-normal sub)))
            ;; Reset new normal size fields so `window-resize-apply'
            ;; won't use them to apply new sizes.
            (set-window-new-normal sub))

          (unless (eq (window-new-normal sub) 'ignore)
            ;; Resize this window's child windows (back-engineering
            ;; delta from sub's old and new total sizes).
            (let ((delta (- (window-new-total sub)
                            (window-total-size sub horizontal))))
              (unless (and (zerop delta) (not trail))
                ;; For the TRAIL non-nil case we have to resize SUB
                ;; recursively even if it's size does not change.
                (window--resize-this-window
                 sub delta horizontal ignore nil trail edge))))
          (setq sub (window-right sub)))))))

(defun window--resize-siblings (window delta &optional horizontal ignore trail edge)
  "Resize other windows when WINDOW is resized vertically by DELTA lines.
Optional argument HORIZONTAL non-nil means resize other windows
when WINDOW is resized horizontally by DELTA columns.  WINDOW
itself is not resized by this function.

Optional argument IGNORE non-nil means ignore restrictions
imposed by fixed size windows, `window-min-height' or
`window-min-width' settings.  If IGNORE equals `safe', live
windows may get as small as `window-safe-min-height' lines and
`window-safe-min-width' columns.  If IGNORE is a window, ignore
restrictions for that window only.  Any other non-nil value means
ignore all of the above restrictions for all windows.

Optional arguments TRAIL and EDGE, when non-nil, refine the set
of windows that shall be resized.  If TRAIL equals `before',
resize only windows on the left or above EDGE.  If TRAIL equals
`after', resize only windows on the right or below EDGE.  Also,
preferably only resize windows adjacent to EDGE."
  (when (window-parent window)
    (let* ((parent (window-parent window))
           (sub (window-child parent)))
      (if (window-combined-p sub horizontal)
          ;; In an iso-combination try to extract DELTA from WINDOW's
          ;; siblings.
          (let ((skip (eq trail 'after))
                this-delta other-delta)
            ;; Decide which windows shall be left alone.
            (while sub
              (cond
               ((eq sub window)
                ;; Make sure WINDOW is left alone when
                ;; resizing its siblings.
                (set-window-new-normal sub 'ignore)
                (setq skip (eq trail 'before)))
               (skip
                ;; Make sure this sibling is left alone when
                ;; resizing its siblings.
                (set-window-new-normal sub 'ignore))
               ((or (window--size-ignore-p sub ignore)
                    (not (window-size-fixed-p sub horizontal)))
                ;; Set this-delta to t to signal that we found a sibling
                ;; of WINDOW whose size is not fixed.
                (setq this-delta t)))

              (setq sub (window-right sub)))

            ;; Set this-delta to what we can get from WINDOW's siblings.
            (if (= (- delta) (window-total-size window horizontal))
                ;; A deletion, presumably.  We must handle this case
                ;; specially since `window--resizable' can't be used.
                (if this-delta
                    ;; There's at least one resizable sibling we can
                    ;; give WINDOW's size to.
                    (setq this-delta delta)
                  ;; No resizable sibling exists.
                  (setq this-delta 0))
              ;; Any other form of resizing.
              (setq this-delta
                    (window--resizable window delta horizontal ignore trail t)))

            ;; Set other-delta to what we still have to get from
            ;; ancestor windows of parent.
            (setq other-delta (- delta this-delta))
            (unless (zerop other-delta)
              ;; Unless we got everything from WINDOW's siblings, PARENT
              ;; must be resized by other-delta lines or columns.
              (set-window-new-total parent other-delta 'add))

            (if (zerop this-delta)
                ;; We haven't got anything from WINDOW's siblings but we
                ;; must update the normal sizes to respect other-delta.
                (window--resize-child-windows-normal
                 parent horizontal window this-delta trail other-delta)
              ;; We did get something from WINDOW's siblings which means
              ;; we have to resize their child windows.
              (unless (eq (window--resize-child-windows
                           parent (- this-delta) horizontal
                           window ignore trail edge)
                          ;; If `window--resize-child-windows' returns
                          ;; 'normalized, this means it has set the
                          ;; normal sizes already.
                          'normalized)
                ;; Set the normal sizes.
                (window--resize-child-windows-normal
                 parent horizontal window this-delta trail other-delta))
              ;; Set DELTA to what we still have to get from ancestor
              ;; windows.
              (setq delta other-delta)))

        ;; In an ortho-combination all siblings of WINDOW must be
        ;; resized by DELTA.
        (set-window-new-total parent delta 'add)
        (while sub
          (unless (eq sub window)
            (window--resize-this-window sub delta horizontal ignore t))
          (setq sub (window-right sub))))

      (unless (zerop delta)
        ;; "Go up."
        (window--resize-siblings
         parent delta horizontal ignore trail edge)))))

(defun window--resize-this-window (window delta &optional horizontal ignore add trail edge)
  "Resize WINDOW vertically by DELTA lines.
Optional argument HORIZONTAL non-nil means resize WINDOW
horizontally by DELTA columns.

Optional argument IGNORE non-nil means ignore restrictions
imposed by fixed size windows, `window-min-height' or
`window-min-width' settings.  If IGNORE equals `safe', live
windows may get as small as `window-safe-min-height' lines and
`window-safe-min-width' columns.  If IGNORE is a window, ignore
restrictions for that window only.  Any other non-nil value
means ignore all of the above restrictions for all windows.

Optional argument ADD non-nil means add DELTA to the new total
size of WINDOW.

Optional arguments TRAIL and EDGE, when non-nil, refine the set
of windows that shall be resized.  If TRAIL equals `before',
resize only windows on the left or above EDGE.  If TRAIL equals
`after', resize only windows on the right or below EDGE.  Also,
preferably only resize windows adjacent to EDGE.

This function recursively resizes WINDOW's child windows to fit the
new size.  Make sure that WINDOW is `window--resizable' before
calling this function.  Note that this function does not resize
siblings of WINDOW or WINDOW's parent window.  You have to
eventually call `window-resize-apply' in order to make resizing
actually take effect."
  (when add
    ;; Add DELTA to the new total size of WINDOW.
    (set-window-new-total window delta t))

  (let ((sub (window-child window)))
    (cond
     ((not sub))
     ((window-combined-p sub horizontal)
      ;; In an iso-combination resize child windows according to their
      ;; normal sizes.
      (window--resize-child-windows
       window delta horizontal nil ignore trail edge))
     ;; In an ortho-combination resize each child window by DELTA.
     (t
      (while sub
        (window--resize-this-window
         sub delta horizontal ignore t trail edge)
        (setq sub (window-right sub)))))))

(defun window--resize-root-window (window delta horizontal ignore)
  "Resize root window WINDOW vertically by DELTA lines.
HORIZONTAL non-nil means resize root window WINDOW horizontally
by DELTA columns.

IGNORE non-nil means ignore any restrictions imposed by fixed
size windows, `window-min-height' or `window-min-width' settings.

This function is only called by the frame resizing routines.  It
resizes windows proportionally and never deletes any windows."
  (when (and (windowp window) (numberp delta)
             (window-sizable-p window delta horizontal ignore))
    (window--resize-reset (window-frame window) horizontal)
    (window--resize-this-window window delta horizontal ignore t)))

(defun window--resize-root-window-vertically (window delta)
  "Resize root window WINDOW vertically by DELTA lines.
If DELTA is less than zero and we can't shrink WINDOW by DELTA
lines, shrink it as much as possible.  If DELTA is greater than
zero, this function can resize fixed-size windows in order to
recover the necessary lines.

Return the number of lines that were recovered.

This function is only called by the minibuffer window resizing
routines.  It resizes windows proportionally and never deletes
any windows."
  (when (numberp delta)
    (let (ignore)
      (cond
       ((< delta 0)
        (setq delta (window-sizable window delta)))
       ((> delta 0)
        (unless (window-sizable window delta)
          (setq ignore t))))

      (window--resize-reset (window-frame window))
      ;; Ideally, we would resize just the last window in a combination
      ;; but that's not feasible for the following reason: If we grow
      ;; the minibuffer window and the last window cannot be shrunk any
      ;; more, we shrink another window instead.  But if we then shrink
      ;; the minibuffer window again, the last window might get enlarged
      ;; and the state after shrinking is not the state before growing.
      ;; So, in practice, we'd need a history variable to record how to
      ;; proceed.  But I'm not sure how such a variable could work with
      ;; repeated minibuffer window growing steps.
      (window--resize-this-window window delta nil ignore t)
      delta)))

(defun adjust-window-trailing-edge (window delta &optional horizontal)
  "Move WINDOW's bottom edge by DELTA lines.
Optional argument HORIZONTAL non-nil means move WINDOW's right
edge by DELTA columns.  WINDOW must be a valid window and
defaults to the selected one.

If DELTA is greater than zero, move the edge downwards or to the
right.  If DELTA is less than zero, move the edge upwards or to
the left.  If the edge can't be moved by DELTA lines or columns,
move it as far as possible in the desired direction."
  (setq window (window-normalize-window window))
  (let* ((frame (window-frame window))
         (minibuffer-window (minibuffer-window frame))
         (right window)
         left this-delta min-delta max-delta)
    ;; Find the edge we want to move.
    (while (and (or (not (window-combined-p right horizontal))
                    (not (window-right right)))
                (setq right (window-parent right))))
    (cond
     ((and (not right) (not horizontal)
           ;; Resize the minibuffer window if it's on the same frame as
           ;; and immediately below WINDOW and it's either active or
           ;; `resize-mini-windows' is nil.
           (eq (window-frame minibuffer-window) frame)
           (= (nth 1 (window-edges minibuffer-window))
              (nth 3 (window-edges window)))
           (or (not resize-mini-windows)
               (eq minibuffer-window (active-minibuffer-window))))
      (window--resize-mini-window minibuffer-window (- delta)))
     ((or (not (setq left right)) (not (setq right (window-right right))))
      (if horizontal
          (error "No window on the right of this one")
        (error "No window below this one")))
     (t
      ;; Set LEFT to the first resizable window on the left.  This step is
      ;; needed to handle fixed-size windows.
      (while (and left (window-size-fixed-p left horizontal))
        (setq left
              (or (window-left left)
                  (progn
                    (while (and (setq left (window-parent left))
                                (not (window-combined-p left horizontal))))
                    (window-left left)))))
      (unless left
        (if horizontal
            (error "No resizable window on the left of this one")
          (error "No resizable window above this one")))

      ;; Set RIGHT to the first resizable window on the right.  This step
      ;; is needed to handle fixed-size windows.
      (while (and right (window-size-fixed-p right horizontal))
        (setq right
              (or (window-right right)
                  (progn
                    (while (and (setq right (window-parent right))
                                (not (window-combined-p right horizontal))))
                    (window-right right)))))
      (unless right
        (if horizontal
            (error "No resizable window on the right of this one")
          (error "No resizable window below this one")))

      ;; LEFT and RIGHT (which might be both internal windows) are now the
      ;; two windows we want to resize.
      (cond
       ((> delta 0)
        (setq max-delta (window--max-delta-1 left 0 horizontal nil 'after))
        (setq min-delta (window--min-delta-1 right (- delta) horizontal nil 'before))
        (when (or (< max-delta delta) (> min-delta (- delta)))
          ;; We can't get the whole DELTA - move as far as possible.
          (setq delta (min max-delta (- min-delta))))
        (unless (zerop delta)
          ;; Start resizing.
          (window--resize-reset frame horizontal)
          ;; Try to enlarge LEFT first.
          (setq this-delta (window--resizable left delta horizontal))
          (unless (zerop this-delta)
            (window--resize-this-window
             left this-delta horizontal nil t 'before
             (if horizontal
                 (+ (window-left-column left) (window-total-size left t))
               (+ (window-top-line left) (window-total-size left)))))
          ;; Shrink windows on right of LEFT.
          (window--resize-siblings
           left delta horizontal nil 'after
           (if horizontal
               (window-left-column right)
             (window-top-line right)))))
       ((< delta 0)
        (setq max-delta (window--max-delta-1 right 0 horizontal nil 'before))
        (setq min-delta (window--min-delta-1 left delta horizontal nil 'after))
        (when (or (< max-delta (- delta)) (> min-delta delta))
          ;; We can't get the whole DELTA - move as far as possible.
          (setq delta (max (- max-delta) min-delta)))
        (unless (zerop delta)
          ;; Start resizing.
          (window--resize-reset frame horizontal)
          ;; Try to enlarge RIGHT.
          (setq this-delta (window--resizable right (- delta) horizontal))
          (unless (zerop this-delta)
            (window--resize-this-window
             right this-delta horizontal nil t 'after
             (if horizontal
                 (window-left-column right)
               (window-top-line right))))
          ;; Shrink windows on left of RIGHT.
          (window--resize-siblings
           right (- delta) horizontal nil 'before
           (if horizontal
               (+ (window-left-column left) (window-total-size left t))
             (+ (window-top-line left) (window-total-size left)))))))
      (unless (zerop delta)
        ;; Don't report an error in the standard case.
        (unless (window-resize-apply frame horizontal)
          ;; But do report an error if applying the changes fails.
          (error "Failed adjusting window %s" window)))))))

(defun enlarge-window (delta &optional horizontal)
  "Make the selected window DELTA lines taller.
Interactively, if no argument is given, make the selected window
one line taller.  If optional argument HORIZONTAL is non-nil,
make selected window wider by DELTA columns.  If DELTA is
negative, shrink selected window by -DELTA lines or columns.
Return nil."
  (interactive "p")
  (let ((minibuffer-window (minibuffer-window)))
    (cond
     ((zerop delta))
     ((window-size-fixed-p nil horizontal)
      (error "Selected window has fixed size"))
     ((window-minibuffer-p)
      (if horizontal
          (error "Cannot resize minibuffer window horizontally")
        (window--resize-mini-window (selected-window) delta)))
     ((and (not horizontal)
           (window-full-height-p)
           (eq (window-frame minibuffer-window) (selected-frame))
           (not resize-mini-windows))
      ;; If the selected window is full height and `resize-mini-windows'
      ;; is nil, resize the minibuffer window.
      (window--resize-mini-window minibuffer-window (- delta)))
     ((window--resizable-p nil delta horizontal)
      (window-resize nil delta horizontal))
     (t
      (window-resize
       nil (if (> delta 0)
               (window-max-delta nil horizontal)
             (- (window-min-delta nil horizontal)))
       horizontal)))))

(defun shrink-window (delta &optional horizontal)
  "Make the selected window DELTA lines smaller.
Interactively, if no argument is given, make the selected window
one line smaller.  If optional argument HORIZONTAL is non-nil,
make selected window narrower by DELTA columns.  If DELTA is
negative, enlarge selected window by -DELTA lines or columns.
Also see the `window-min-height' variable.
Return nil."
  (interactive "p")
  (let ((minibuffer-window (minibuffer-window)))
    (cond
     ((zerop delta))
     ((window-size-fixed-p nil horizontal)
      (error "Selected window has fixed size"))
     ((window-minibuffer-p)
      (if horizontal
          (error "Cannot resize minibuffer window horizontally")
        (window--resize-mini-window (selected-window) (- delta))))
     ((and (not horizontal)
           (window-full-height-p)
           (eq (window-frame minibuffer-window) (selected-frame))
           (not resize-mini-windows))
      ;; If the selected window is full height and `resize-mini-windows'
      ;; is nil, resize the minibuffer window.
      (window--resize-mini-window minibuffer-window delta))
     ((window--resizable-p nil (- delta) horizontal)
      (window-resize nil (- delta) horizontal))
     (t
      (window-resize
       nil (if (> delta 0)
               (- (window-min-delta nil horizontal))
             (window-max-delta nil horizontal))
       horizontal)))))

(defun maximize-window (&optional window)
  "Maximize WINDOW.
Make WINDOW as large as possible without deleting any windows.
WINDOW must be a valid window and defaults to the selected one."
  (interactive)
  (setq window (window-normalize-window window))
  (window-resize window (window-max-delta window))
  (window-resize window (window-max-delta window t) t))

(defun minimize-window (&optional window)
  "Minimize WINDOW.
Make WINDOW as small as possible without deleting any windows.
WINDOW must be a valid window and defaults to the selected one."
  (interactive)
  (setq window (window-normalize-window window))
  (window-resize window (- (window-min-delta window)))
  (window-resize window (- (window-min-delta window t)) t))
\f
(defun frame-root-window-p (window)
  "Return non-nil if WINDOW is the root window of its frame."
  (eq window (frame-root-window window)))

(defun window--subtree (window &optional next)
  "Return window subtree rooted at WINDOW.
Optional argument NEXT non-nil means include WINDOW's right
siblings in the return value.

See the documentation of `window-tree' for a description of the
return value."
  (let (list)
    (while window
      (setq list
            (cons
             (cond
              ((window-top-child window)
               (cons t (cons (window-edges window)
                             (window--subtree (window-top-child window) t))))
              ((window-left-child window)
               (cons nil (cons (window-edges window)
                               (window--subtree (window-left-child window) t))))
              (t window))
             list))
      (setq window (when next (window-next-sibling window))))
    (nreverse list)))

(defun window-tree (&optional frame)
  "Return the window tree of frame FRAME.
FRAME must be a live frame and defaults to the selected frame.
The return value is a list of the form (ROOT MINI), where ROOT
represents the window tree of the frame's root window, and MINI
is the frame's minibuffer window.

If the root window is not split, ROOT is the root window itself.
Otherwise, ROOT is a list (DIR EDGES W1 W2 ...) where DIR is nil
for a horizontal split, and t for a vertical split.  EDGES gives
the combined size and position of the child windows in the split,
and the rest of the elements are the child windows in the split.
Each of the child windows may again be a window or a list
representing a window split, and so on.  EDGES is a list (LEFT
TOP RIGHT BOTTOM) as returned by `window-edges'."
  (setq frame (window-normalize-frame frame))
  (window--subtree (frame-root-window frame) t))
\f
(defun other-window (count &optional all-frames)
  "Select another window in cyclic ordering of windows.
COUNT specifies the number of windows to skip, starting with the
selected window, before making the selection.  If COUNT is
positive, skip COUNT windows forwards.  If COUNT is negative,
skip -COUNT windows backwards.  COUNT zero means do not skip any
window, so select the selected window.  In an interactive call,
COUNT is the numeric prefix argument.  Return nil.

If the `other-window' parameter of the selected window is a
function and `ignore-window-parameters' is nil, call that
function with the arguments COUNT and ALL-FRAMES.

This function does not select a window whose `no-other-window'
window parameter is non-nil.

This function uses `next-window' for finding the window to
select.  The argument ALL-FRAMES has the same meaning as in
`next-window', but the MINIBUF argument of `next-window' is
always effectively nil."
  (interactive "p")
  (let* ((window (selected-window))
         (function (and (not ignore-window-parameters)
                        (window-parameter window 'other-window)))
         old-window old-count)
    (if (functionp function)
        (funcall function count all-frames)
      ;; `next-window' and `previous-window' may return a window we are
      ;; not allowed to select.  Hence we need an exit strategy in case
      ;; all windows are non-selectable.
      (catch 'exit
        (while (> count 0)
          (setq window (next-window window nil all-frames))
          (cond
           ((eq window old-window)
            (when (= count old-count)
              ;; Keep out of infinite loops.  When COUNT has not changed
              ;; since we last looked at `window' we're probably in one.
              (throw 'exit nil)))
           ((window-parameter window 'no-other-window)
            (unless old-window
              ;; The first non-selectable window `next-window' got us:
              ;; Remember it and the current value of COUNT.
              (setq old-window window)
              (setq old-count count)))
           (t
            (setq count (1- count)))))
        (while (< count 0)
          (setq window (previous-window window nil all-frames))
          (cond
           ((eq window old-window)
            (when (= count old-count)
              ;; Keep out of infinite loops.  When COUNT has not changed
              ;; since we last looked at `window' we're probably in one.
              (throw 'exit nil)))
           ((window-parameter window 'no-other-window)
            (unless old-window
              ;; The first non-selectable window `previous-window' got
              ;; us: Remember it and the current value of COUNT.
              (setq old-window window)
              (setq old-count count)))
           (t
            (setq count (1+ count)))))

        (select-window window)
        ;; Always return nil.
        nil))))

;; This should probably return non-nil when the selected window is part
;; of an atomic window whose root is the frame's root window.
(defun one-window-p (&optional nomini all-frames)
  "Return non-nil if the selected window is the only window.
Optional arg NOMINI non-nil means don't count the minibuffer
even if it is active.  Otherwise, the minibuffer is counted
when it is active.

Optional argument ALL-FRAMES specifies the set of frames to
consider, see also `next-window'.  ALL-FRAMES nil or omitted
means consider windows on the selected frame only, plus the
minibuffer window if specified by the NOMINI argument.  If the
minibuffer counts, consider all windows on all frames that share
that minibuffer too.  The remaining non-nil values of ALL-FRAMES
with a special meaning are:

- t means consider all windows on all existing frames.

- `visible' means consider all windows on all visible frames on
  the current terminal.

- 0 (the number zero) means consider all windows on all visible
  and iconified frames on the current terminal.

- A frame means consider all windows on that frame only.

Anything else means consider all windows on the selected frame
and no others."
  (let ((base-window (selected-window)))
    (if (and nomini (eq base-window (minibuffer-window)))
        (setq base-window (next-window base-window)))
    (eq base-window
        (next-window base-window (if nomini 'arg) all-frames))))
\f
;;; Deleting windows.
(defun window-deletable-p (&optional window)
  "Return t if WINDOW can be safely deleted from its frame.
WINDOW must be a valid window and defaults to the selected one.
Return `frame' if deleting WINDOW should also delete its frame."
  (setq window (window-normalize-window window))

  (unless ignore-window-parameters
    ;; Handle atomicity.
    (when (window-parameter window 'window-atom)
      (setq window (window-atom-root window))))

  (let ((frame (window-frame window)))
    (cond
     ((frame-root-window-p window)
      ;; WINDOW's frame can be deleted only if there are other frames
      ;; on the same terminal, and it does not contain the active
      ;; minibuffer.
      (unless (or (eq frame (next-frame frame 0))
                  (let ((minibuf (active-minibuffer-window)))
                    (and minibuf (eq frame (window-frame minibuf)))))
        'frame))
     ((or ignore-window-parameters
          (not (eq window (window--major-non-side-window frame))))
      ;; WINDOW can be deleted unless it is the major non-side window of
      ;; its frame.
      t))))

(defun window--in-subtree-p (window root)
  "Return t if WINDOW is either ROOT or a member of ROOT's subtree."
  (or (eq window root)
      (let ((parent (window-parent window)))
        (catch 'done
          (while parent
            (if (eq parent root)
                (throw 'done t)
              (setq parent (window-parent parent))))))))

(defun delete-window (&optional window)
  "Delete WINDOW.
WINDOW must be a valid window and defaults to the selected one.
Return nil.

If the variable `ignore-window-parameters' is non-nil or the
`delete-window' parameter of WINDOW equals t, do not process any
parameters of WINDOW.  Otherwise, if the `delete-window'
parameter of WINDOW specifies a function, call that function with
WINDOW as its sole argument and return the value returned by that
function.

Otherwise, if WINDOW is part of an atomic window, call
`delete-window' with the root of the atomic window as its
argument.  Signal an error if WINDOW is either the only window on
its frame, the last non-side window, or part of an atomic window
that is its frame's root window."
  (interactive)
  (setq window (window-normalize-window window))
  (let* ((frame (window-frame window))
         (function (window-parameter window 'delete-window))
         (parent (window-parent window))
         atom-root)
    (window--check frame)
    (catch 'done
      ;; Handle window parameters.
      (cond
       ;; Ignore window parameters if `ignore-window-parameters' tells
       ;; us so or `delete-window' equals t.
       ((or ignore-window-parameters (eq function t)))
       ((functionp function)
        ;; The `delete-window' parameter specifies the function to call.
        ;; If that function is `ignore' nothing is done.  It's up to the
        ;; function called here to avoid infinite recursion.
        (throw 'done (funcall function window)))
       ((and (window-parameter window 'window-atom)
             (setq atom-root (window-atom-root window))
             (not (eq atom-root window)))
        (if (eq atom-root (frame-root-window frame))
            (error "Root of atomic window is root window of its frame")
          (throw 'done (delete-window atom-root))))
       ((not parent)
        (error "Attempt to delete minibuffer or sole ordinary window"))
       ((eq window (window--major-non-side-window frame))
        (error "Attempt to delete last non-side window")))

      (let* ((horizontal (window-left-child parent))
             (size (window-total-size window horizontal))
             (frame-selected
              (window--in-subtree-p (frame-selected-window frame) window))
             ;; Emacs 23 preferably gives WINDOW's space to its left
             ;; sibling.
             (sibling (or (window-left window) (window-right window))))
        (window--resize-reset frame horizontal)
        (cond
         ((and (not window-combination-resize)
               sibling (window-sizable-p sibling size))
          ;; Resize WINDOW's sibling.
          (window--resize-this-window sibling size horizontal nil t)
          (set-window-new-normal
           sibling (+ (window-normal-size sibling horizontal)
                      (window-normal-size window horizontal))))
         ((window--resizable-p window (- size) horizontal nil nil nil t)
          ;; Can do without resizing fixed-size windows.
          (window--resize-siblings window (- size) horizontal))
         (t
          ;; Can't do without resizing fixed-size windows.
          (window--resize-siblings window (- size) horizontal t)))
        ;; Actually delete WINDOW.
        (delete-window-internal window)
        (when (and frame-selected
                   (window-parameter
                    (frame-selected-window frame) 'no-other-window))
          ;; `delete-window-internal' has selected a window that should
          ;; not be selected, fix this here.
          (other-window -1 frame))
        (run-window-configuration-change-hook frame)
        (window--check frame)
        ;; Always return nil.
        nil))))

(defun delete-other-windows (&optional window)
  "Make WINDOW fill its frame.
WINDOW must be a valid window and defaults to the selected one.
Return nil.

If the variable `ignore-window-parameters' is non-nil or the
`delete-other-windows' parameter of WINDOW equals t, do not
process any parameters of WINDOW.  Otherwise, if the
`delete-other-windows' parameter of WINDOW specifies a function,
call that function with WINDOW as its sole argument and return
the value returned by that function.

Otherwise, if WINDOW is part of an atomic window, call this
function with the root of the atomic window as its argument.  If
WINDOW is a non-side window, make WINDOW the only non-side window
on the frame.  Side windows are not deleted.  If WINDOW is a side
window signal an error."
  (interactive)
  (setq window (window-normalize-window window))
  (let* ((frame (window-frame window))
         (function (window-parameter window 'delete-other-windows))
         (window-side (window-parameter window 'window-side))
         atom-root side-main)
    (window--check frame)
    (catch 'done
      (cond
       ;; Ignore window parameters if `ignore-window-parameters' is t or
       ;; `delete-other-windows' is t.
       ((or ignore-window-parameters (eq function t)))
       ((functionp function)
        ;; The `delete-other-windows' parameter specifies the function
        ;; to call.  If the function is `ignore' no windows are deleted.
        ;; It's up to the function called to avoid infinite recursion.
        (throw 'done (funcall function window)))
       ((and (window-parameter window 'window-atom)
             (setq atom-root (window-atom-root window))
             (not (eq atom-root window)))
        (if (eq atom-root (frame-root-window frame))
            (error "Root of atomic window is root window of its frame")
          (throw 'done (delete-other-windows atom-root))))
       ((memq window-side window-sides)
        (error "Cannot make side window the only window"))
       ((and (window-minibuffer-p window)
             (not (eq window (frame-root-window window))))
        (error "Can't expand minibuffer to full frame")))

      ;; If WINDOW is the major non-side window, do nothing.
      (if (window-with-parameter 'window-side)
          (setq side-main (window--major-non-side-window frame))
        (setq side-main (frame-root-window frame)))
      (unless (eq window side-main)
        (delete-other-windows-internal window side-main)
        (run-window-configuration-change-hook frame)
        (window--check frame))
      ;; Always return nil.
      nil)))

(defun delete-other-windows-vertically (&optional window)
  "Delete the windows in the same column with WINDOW, but not WINDOW itself.
This may be a useful alternative binding for \\[delete-other-windows]
 if you often split windows horizontally."
  (interactive)
  (let* ((window (or window (selected-window)))
         (edges (window-edges window))
         (w window) delenda)
    (while (not (eq (setq w (next-window w 1)) window))
      (let ((e (window-edges w)))
        (when (and (= (car e) (car edges))
                   (= (nth 2 e) (nth 2 edges)))
          (push w delenda))))
    (mapc 'delete-window delenda)))

;;; Windows and buffers.

;; `prev-buffers' and `next-buffers' are two reserved window slots used
;; for (1) determining which buffer to show in the window when its
;; buffer shall be buried or killed and (2) which buffer to show for
;; `switch-to-prev-buffer' and `switch-to-next-buffer'.

;; `prev-buffers' consists of <buffer, window-start, window-point>
;; triples.  The entries on this list are ordered by the time their
;; buffer has been removed from the window, the most recently removed
;; buffer's entry being first.  The window-start and window-point
;; components are `window-start' and `window-point' at the time the
;; buffer was removed from the window which implies that the entry must
;; be added when `set-window-buffer' removes the buffer from the window.

;; `next-buffers' is the list of buffers that have been replaced
;; recently by `switch-to-prev-buffer'.  These buffers are the least
;; preferred candidates of `switch-to-prev-buffer' and the preferred
;; candidates of `switch-to-next-buffer' to switch to.  This list is
;; reset to nil by any action changing the window's buffer with the
;; exception of `switch-to-prev-buffer' and `switch-to-next-buffer'.
;; `switch-to-prev-buffer' pushes the buffer it just replaced on it,
;; `switch-to-next-buffer' pops the last pushed buffer from it.

;; Both `prev-buffers' and `next-buffers' may reference killed buffers
;; if such a buffer was killed while the window was hidden within a
;; window configuration.  Such killed buffers get removed whenever
;; `switch-to-prev-buffer' or `switch-to-next-buffer' encounter them.

;; The following function is called by `set-window-buffer' _before_ it
;; replaces the buffer of the argument window with the new buffer.
(defun record-window-buffer (&optional window)
  "Record WINDOW's buffer.
WINDOW must be a live window and defaults to the selected one."
  (let* ((window (window-normalize-window window t))
         (buffer (window-buffer window))
         (entry (assq buffer (window-prev-buffers window))))
    ;; Reset WINDOW's next buffers.  If needed, they are resurrected by
    ;; `switch-to-prev-buffer' and `switch-to-next-buffer'.
    (set-window-next-buffers window nil)

    (when entry
      ;; Remove all entries for BUFFER from WINDOW's previous buffers.
      (set-window-prev-buffers
       window (assq-delete-all buffer (window-prev-buffers window))))

    ;; Don't record insignificant buffers.
    (unless (eq (aref (buffer-name buffer) 0) ?\s)
      ;; Add an entry for buffer to WINDOW's previous buffers.
      (with-current-buffer buffer
        (let ((start (window-start window))
              (point (window-point window)))
          (setq entry
                (cons buffer
                      (if entry
                          ;; We have an entry, update marker positions.
                          (list (set-marker (nth 1 entry) start)
                                (set-marker (nth 2 entry) point))
                        ;; Make new markers.
                        (list (copy-marker start)
                              (copy-marker point)))))

          (set-window-prev-buffers
           window (cons entry (window-prev-buffers window))))))))

(defun unrecord-window-buffer (&optional window buffer)
  "Unrecord BUFFER in WINDOW.
WINDOW must be a live window and defaults to the selected one.
BUFFER must be a live buffer and defaults to the buffer of
WINDOW."
  (let* ((window (window-normalize-window window t))
         (buffer (or buffer (window-buffer window))))
    (set-window-prev-buffers
     window (assq-delete-all buffer (window-prev-buffers window)))
    (set-window-next-buffers
     window (delq buffer (window-next-buffers window)))))

(defun set-window-buffer-start-and-point (window buffer &optional start point)
  "Set WINDOW's buffer to BUFFER.
WINDOW must be a live window and defaults to the selected one.
Optional argument START non-nil means set WINDOW's start position
to START.  Optional argument POINT non-nil means set WINDOW's
point to POINT.  If WINDOW is selected this also sets BUFFER's
`point' to POINT.  If WINDOW is selected and the buffer it showed
before was current this also makes BUFFER the current buffer."
  (setq window (window-normalize-window window t))
  (let ((selected (eq window (selected-window)))
        (current (eq (window-buffer window) (current-buffer))))
    (set-window-buffer window buffer)
    (when (and selected current)
      (set-buffer buffer))
    (when start
      ;; Don't force window-start here (even if POINT is nil).
      (set-window-start window start t))
    (when point
      (set-window-point window point))))

(defcustom switch-to-visible-buffer t
  "If non-nil, allow switching to an already visible buffer.
If this variable is non-nil, `switch-to-prev-buffer' and
`switch-to-next-buffer' may switch to an already visible buffer
provided the buffer was shown in the argument window before.  If
this variable is nil, `switch-to-prev-buffer' and
`switch-to-next-buffer' always try to avoid switching to a buffer
that is already visible in another window on the same frame."
  :type 'boolean
  :version "24.1"
  :group 'windows)

(defun switch-to-prev-buffer (&optional window bury-or-kill)
  "In WINDOW switch to previous buffer.
WINDOW must be a live window and defaults to the selected one.
Return the buffer switched to, nil if no suitable buffer could be
found.

Optional argument BURY-OR-KILL non-nil means the buffer currently
shown in WINDOW is about to be buried or killed and consequently
shall not be switched to in future invocations of this command.

As a special case, if BURY-OR-KILL equals `append', this means to
move the buffer to the end of WINDOW's previous buffers list so a
future invocation of `switch-to-prev-buffer' less likely switches
to it."
  (interactive)
  (let* ((window (window-normalize-window window t))
         (frame (window-frame window))
         (old-buffer (window-buffer window))
         ;; Save this since it's destroyed by `set-window-buffer'.
         (next-buffers (window-next-buffers window))
         (pred (frame-parameter frame 'buffer-predicate))
         entry new-buffer killed-buffers visible)
    (when (window-minibuffer-p window)
      ;; Don't switch in minibuffer window.
      (unless (setq window (minibuffer-selected-window))
        (error "Window %s is a minibuffer window" window)))

    (when (window-dedicated-p window)
      ;; Don't switch in dedicated window.
      (error "Window %s is dedicated to buffer %s" window old-buffer))

    (catch 'found
      ;; Scan WINDOW's previous buffers first, skipping entries of next
      ;; buffers.
      (dolist (entry (window-prev-buffers window))
        (when (and (setq new-buffer (car entry))
                   (or (buffer-live-p new-buffer)
                       (not (setq killed-buffers
                                  (cons new-buffer killed-buffers))))
                   (not (eq new-buffer old-buffer))
                   (or (null pred) (funcall pred new-buffer))
                   ;; When BURY-OR-KILL is nil, avoid switching to a
                   ;; buffer in WINDOW's next buffers list.
                   (or bury-or-kill (not (memq new-buffer next-buffers))))
          (if (and (not switch-to-visible-buffer)
                   (get-buffer-window new-buffer frame))
              ;; Try to avoid showing a buffer visible in some other
              ;; window.
              (setq visible new-buffer)
            (set-window-buffer-start-and-point
             window new-buffer (nth 1 entry) (nth 2 entry))
            (throw 'found t))))
      ;; Scan reverted buffer list of WINDOW's frame next, skipping
      ;; entries of next buffers.  Note that when we bury or kill a
      ;; buffer we don't reverse the global buffer list to avoid showing
      ;; a buried buffer instead.  Otherwise, we must reverse the global
      ;; buffer list in order to make sure that switching to the
      ;; previous/next buffer traverse it in opposite directions.
      (dolist (buffer (if bury-or-kill
                          (buffer-list frame)
                        (nreverse (buffer-list frame))))
        (when (and (buffer-live-p buffer)
                   (not (eq buffer old-buffer))
                   (or (null pred) (funcall pred buffer))
                   (not (eq (aref (buffer-name buffer) 0) ?\s))
                   (or bury-or-kill (not (memq buffer next-buffers))))
          (if (get-buffer-window buffer frame)
              ;; Try to avoid showing a buffer visible in some other window.
              (unless visible
                (setq visible buffer))
            (setq new-buffer buffer)
            (set-window-buffer-start-and-point window new-buffer)
            (throw 'found t))))
      (unless bury-or-kill
        ;; Scan reverted next buffers last (must not use nreverse
        ;; here!).
        (dolist (buffer (reverse next-buffers))
          ;; Actually, buffer _must_ be live here since otherwise it
          ;; would have been caught in the scan of previous buffers.
          (when (and (or (buffer-live-p buffer)
                         (not (setq killed-buffers
                                    (cons buffer killed-buffers))))
                     (not (eq buffer old-buffer))
                     (or (null pred) (funcall pred buffer))
                     (setq entry (assq buffer (window-prev-buffers window))))
            (setq new-buffer buffer)
            (set-window-buffer-start-and-point
             window new-buffer (nth 1 entry) (nth 2 entry))
            (throw 'found t))))

      ;; Show a buffer visible in another window.
      (when visible
        (setq new-buffer visible)
        (set-window-buffer-start-and-point window new-buffer)))

    (if bury-or-kill
        (let ((entry (and (eq bury-or-kill 'append)
                          (assq old-buffer (window-prev-buffers window)))))
          ;; Remove `old-buffer' from WINDOW's previous and (restored list
          ;; of) next buffers.
          (set-window-prev-buffers
           window (assq-delete-all old-buffer (window-prev-buffers window)))
          (set-window-next-buffers window (delq old-buffer next-buffers))
          (when entry
            ;; Append old-buffer's entry to list of WINDOW's previous
            ;; buffers so it's less likely to get switched to soon but
            ;; `display-buffer-in-previous-window' can nevertheless find
            ;; it.
            (set-window-prev-buffers
             window (append (window-prev-buffers window) (list entry)))))
      ;; Move `old-buffer' to head of WINDOW's restored list of next
      ;; buffers.
      (set-window-next-buffers
       window (cons old-buffer (delq old-buffer next-buffers))))

    ;; Remove killed buffers from WINDOW's previous and next buffers.
    (when killed-buffers
      (dolist (buffer killed-buffers)
        (set-window-prev-buffers
         window (assq-delete-all buffer (window-prev-buffers window)))
        (set-window-next-buffers
         window (delq buffer (window-next-buffers window)))))

    ;; Return new-buffer.
    new-buffer))

(defun switch-to-next-buffer (&optional window)
  "In WINDOW switch to next buffer.
WINDOW must be a live window and defaults to the selected one.
Return the buffer switched to, nil if no suitable buffer could be
found."
  (interactive)
  (let* ((window (window-normalize-window window t))
         (frame (window-frame window))
         (old-buffer (window-buffer window))
         (next-buffers (window-next-buffers window))
         (pred (frame-parameter frame 'buffer-predicate))
         new-buffer entry killed-buffers visible)
    (when (window-minibuffer-p window)
      ;; Don't switch in minibuffer window.
      (unless (setq window (minibuffer-selected-window))
        (error "Window %s is a minibuffer window" window)))

    (when (window-dedicated-p window)
      ;; Don't switch in dedicated window.
      (error "Window %s is dedicated to buffer %s" window old-buffer))

    (catch 'found
      ;; Scan WINDOW's next buffers first.
      (dolist (buffer next-buffers)
        (when (and (or (buffer-live-p buffer)
                       (not (setq killed-buffers
                                  (cons buffer killed-buffers))))
                   (not (eq buffer old-buffer))
                   (or (null pred) (funcall pred buffer))
                   (setq entry (assq buffer (window-prev-buffers window))))
          (setq new-buffer buffer)
          (set-window-buffer-start-and-point
           window new-buffer (nth 1 entry) (nth 2 entry))
          (throw 'found t)))
      ;; Scan the buffer list of WINDOW's frame next, skipping previous
      ;; buffers entries.
      (dolist (buffer (buffer-list frame))
        (when (and (buffer-live-p buffer)
                   (not (eq buffer old-buffer))
                   (or (null pred) (funcall pred buffer))
                   (not (eq (aref (buffer-name buffer) 0) ?\s))
                   (not (assq buffer (window-prev-buffers window))))
          (if (get-buffer-window buffer frame)
              ;; Try to avoid showing a buffer visible in some other window.
              (setq visible buffer)
            (setq new-buffer buffer)
            (set-window-buffer-start-and-point window new-buffer)
            (throw 'found t))))
      ;; Scan WINDOW's reverted previous buffers last (must not use
      ;; nreverse here!)
      (dolist (entry (reverse (window-prev-buffers window)))
        (when (and (setq new-buffer (car entry))
                   (or (buffer-live-p new-buffer)
                       (not (setq killed-buffers
                                  (cons new-buffer killed-buffers))))
                   (not (eq new-buffer old-buffer))
                   (or (null pred) (funcall pred new-buffer)))
          (if (and (not switch-to-visible-buffer)
                   (get-buffer-window new-buffer frame))
              ;; Try to avoid showing a buffer visible in some other window.
              (unless visible
                (setq visible new-buffer))
            (set-window-buffer-start-and-point
             window new-buffer (nth 1 entry) (nth 2 entry))
            (throw 'found t))))

      ;; Show a buffer visible in another window.
      (when visible
        (setq new-buffer visible)
        (set-window-buffer-start-and-point window new-buffer)))

    ;; Remove `new-buffer' from and restore WINDOW's next buffers.
    (set-window-next-buffers window (delq new-buffer next-buffers))

    ;; Remove killed buffers from WINDOW's previous and next buffers.
    (when killed-buffers
      (dolist (buffer killed-buffers)
        (set-window-prev-buffers
         window (assq-delete-all buffer (window-prev-buffers window)))
        (set-window-next-buffers
         window (delq buffer (window-next-buffers window)))))

    ;; Return new-buffer.
    new-buffer))

(defun get-next-valid-buffer (list &optional buffer visible-ok frame)
  "Search LIST for a valid buffer to display in FRAME.
Return nil when all buffers in LIST are undesirable for display,
otherwise return the first suitable buffer in LIST.

Buffers not visible in windows are preferred to visible buffers,
unless VISIBLE-OK is non-nil.
If the optional argument FRAME is nil, it defaults to the selected frame.
If BUFFER is non-nil, ignore occurrences of that buffer in LIST."
  ;; This logic is more or less copied from other-buffer.
  (setq frame (or frame (selected-frame)))
  (let ((pred (frame-parameter frame 'buffer-predicate))
        found buf)
    (while (and (not found) list)
      (setq buf (car list))
      (if (and (not (eq buffer buf))
               (buffer-live-p buf)
               (or (null pred) (funcall pred buf))
               (not (eq (aref (buffer-name buf) 0) ?\s))
               (or visible-ok (null (get-buffer-window buf 'visible))))
          (setq found buf)
        (setq list (cdr list))))
    (car list)))

(defun last-buffer (&optional buffer visible-ok frame)
  "Return the last buffer in FRAME's buffer list.
If BUFFER is the last buffer, return the preceding buffer
instead.  Buffers not visible in windows are preferred to visible
buffers, unless optional argument VISIBLE-OK is non-nil.
Optional third argument FRAME nil or omitted means use the
selected frame's buffer list.  If no such buffer exists, return
the buffer `*scratch*', creating it if necessary."
  (setq frame (or frame (selected-frame)))
  (or (get-next-valid-buffer (nreverse (buffer-list frame))
                             buffer visible-ok frame)
      (get-buffer "*scratch*")
      (let ((scratch (get-buffer-create "*scratch*")))
        (set-buffer-major-mode scratch)
        scratch)))

(defcustom frame-auto-hide-function #'iconify-frame
  "Function called to automatically hide frames.
The function is called with one argument - a frame.

Functions affected by this option are those that bury a buffer
shown in a separate frame like `quit-window' and `bury-buffer'."
  :type '(choice (const :tag "Iconify" iconify-frame)
                 (const :tag "Delete" delete-frame)
                 (const :tag "Do nothing" ignore)
                 function)
  :group 'windows
  :group 'frames
  :version "24.1")

(defun window--delete (&optional window dedicated-only kill)
  "Delete WINDOW if possible.
WINDOW must be a live window and defaults to the selected one.
Optional argument DEDICATED-ONLY non-nil means to delete WINDOW
only if it's dedicated to its buffer.  Optional argument KILL
means the buffer shown in window will be killed.  Return non-nil
if WINDOW gets deleted or its frame is auto-hidden."
  (setq window (window-normalize-window window t))
  (unless (and dedicated-only (not (window-dedicated-p window)))
    (let ((deletable (window-deletable-p window)))
      (cond
       ((eq deletable 'frame)
        (let ((frame (window-frame window)))
          (cond
           (kill
            (delete-frame frame))
           ((functionp frame-auto-hide-function)
            (funcall frame-auto-hide-function frame))))
        'frame)
       (deletable
        (delete-window window)
        t)))))

(defun bury-buffer (&optional buffer-or-name)
  "Put BUFFER-OR-NAME at the end of the list of all buffers.
There it is the least likely candidate for `other-buffer' to
return; thus, the least likely buffer for \\[switch-to-buffer] to
select by default.

You can specify a buffer name as BUFFER-OR-NAME, or an actual
buffer object.  If BUFFER-OR-NAME is nil or omitted, bury the
current buffer.  Also, if BUFFER-OR-NAME is nil or omitted,
remove the current buffer from the selected window if it is
displayed there."
  (interactive)
  (let* ((buffer (window-normalize-buffer buffer-or-name)))
    ;; If `buffer-or-name' is not on the selected frame we unrecord it
    ;; although it's not "here" (call it a feature).
    (bury-buffer-internal buffer)
    ;; Handle case where `buffer-or-name' is nil and the current buffer
    ;; is shown in the selected window.
    (cond
     ((or buffer-or-name (not (eq buffer (window-buffer)))))
     ((window--delete nil t))
     (t
      ;; Switch to another buffer in window.
      (set-window-dedicated-p nil nil)
      (switch-to-prev-buffer nil 'bury)))

    ;; Always return nil.
    nil))

(defun unbury-buffer ()
  "Switch to the last buffer in the buffer list."
  (interactive)
  (switch-to-buffer (last-buffer)))

(defun next-buffer ()
  "In selected window switch to next buffer."
  (interactive)
  (cond
   ((window-minibuffer-p)
    (error "Cannot switch buffers in minibuffer window"))
   ((eq (window-dedicated-p) t)
    (error "Window is strongly dedicated to its buffer"))
   (t
    (switch-to-next-buffer))))

(defun previous-buffer ()
  "In selected window switch to previous buffer."
  (interactive)
  (cond
   ((window-minibuffer-p)
    (error "Cannot switch buffers in minibuffer window"))
   ((eq (window-dedicated-p) t)
    (error "Window is strongly dedicated to its buffer"))
   (t
    (switch-to-prev-buffer))))

(defun delete-windows-on (&optional buffer-or-name frame)
  "Delete all windows showing BUFFER-OR-NAME.
BUFFER-OR-NAME may be a buffer or the name of an existing buffer
and defaults to the current buffer.

The following non-nil values of the optional argument FRAME
have special meanings:

- t means consider all windows on the selected frame only.

- `visible' means consider all windows on all visible frames on
  the current terminal.

- 0 (the number zero) means consider all windows on all visible
  and iconified frames on the current terminal.

- A frame means consider all windows on that frame only.

Any other value of FRAME means consider all windows on all
frames.

When a window showing BUFFER-OR-NAME is dedicated and the only
window of its frame, that frame is deleted when there are other
frames left."
  (interactive "BDelete windows on (buffer):\nP")
  (let ((buffer (window-normalize-buffer buffer-or-name))
        ;; Handle the "inverted" meaning of the FRAME argument wrt other
        ;; `window-list-1' based function.
        (all-frames (cond ((not frame) t) ((eq frame t) nil) (t frame))))
    (dolist (window (window-list-1 nil nil all-frames))
      (if (eq (window-buffer window) buffer)
          (let ((deletable (window-deletable-p window)))
            (cond
             ((and (eq deletable 'frame) (window-dedicated-p window))
              ;; Delete frame if and only if window is dedicated.
              (delete-frame (window-frame window)))
             ((eq deletable t)
              ;; Delete window.
              (delete-window window))
             (t
              ;; In window switch to previous buffer.
              (set-window-dedicated-p window nil)
              (switch-to-prev-buffer window 'bury))))
        ;; If a window doesn't show BUFFER, unrecord BUFFER in it.
        (unrecord-window-buffer window buffer)))))

(defun replace-buffer-in-windows (&optional buffer-or-name)
  "Replace BUFFER-OR-NAME with some other buffer in all windows showing it.
BUFFER-OR-NAME may be a buffer or the name of an existing buffer
and defaults to the current buffer.

When a window showing BUFFER-OR-NAME is dedicated, that window is
deleted.  If that window is the only window on its frame, the
frame is deleted too when there are other frames left.  If there
are no other frames left, some other buffer is displayed in that
window.

This function removes the buffer denoted by BUFFER-OR-NAME from
all window-local buffer lists."
  (interactive "bBuffer to replace: ")
  (let ((buffer (window-normalize-buffer buffer-or-name)))
    (dolist (window (window-list-1 nil nil t))
      (if (eq (window-buffer window) buffer)
          (unless (window--delete window t t)
            ;; Switch to another buffer in window.
            (set-window-dedicated-p window nil)
            (switch-to-prev-buffer window 'kill))
        ;; Unrecord BUFFER in WINDOW.
        (unrecord-window-buffer window buffer)))))

(defun quit-restore-window (&optional window bury-or-kill)
  "Quit WINDOW and deal with its buffer.
WINDOW must be a live window and defaults to the selected one.

According to information stored in WINDOW's `quit-restore' window
parameter either (1) delete WINDOW and its frame, (2) delete
WINDOW, (3) restore the buffer previously displayed in WINDOW,
or (4) make WINDOW display some other buffer than the present
one.  If non-nil, reset `quit-restore' parameter to nil.

Optional second argument BURY-OR-KILL tells how to proceed with
the buffer of WINDOW.  The following values are handled:

`nil' means to not handle the buffer in a particular way.  This
  means that if WINDOW is not deleted by this function, invoking
  `switch-to-prev-buffer' will usually show the buffer again.

`append' means that if WINDOW is not deleted, move its buffer to
  the end of WINDOW's previous buffers so it's less likely that a
  future invocation of `switch-to-prev-buffer' will switch to it.
  Also, move the buffer to the end of the frame's buffer list.

`bury' means that if WINDOW is not deleted, remove its buffer
  from WINDOW'S list of previous buffers.  Also, move the buffer
  to the end of the frame's buffer list.  This value provides the
  most reliable remedy to not have `switch-to-prev-buffer' switch
  to this buffer again without killing the buffer.

`kill' means to kill WINDOW's buffer."
  (setq window (window-normalize-window window t))
  (let* ((buffer (window-buffer window))
         (quit-restore (window-parameter window 'quit-restore))
         (prev-buffer
          (let* ((prev-buffers (window-prev-buffers window))
                 (prev-buffer (caar prev-buffers)))
            (and (or (not (eq prev-buffer buffer))
                     (and (cdr prev-buffers)
                          (not (eq (setq prev-buffer (cadr prev-buffers))
                                   buffer))))
                 prev-buffer)))
         quad entry)
    (cond
     ((and (not prev-buffer)
           (memq (nth 1 quit-restore) '(window frame))
           (eq (nth 3 quit-restore) buffer)
           ;; Delete WINDOW if possible.
           (window--delete window nil (eq bury-or-kill 'kill)))
      ;; If the previously selected window is still alive, select it.
      (when (window-live-p (nth 2 quit-restore))
        (select-window (nth 2 quit-restore))))
     ((and (listp (setq quad (nth 1 quit-restore)))
           (buffer-live-p (car quad))
           (eq (nth 3 quit-restore) buffer))
      ;; Show another buffer stored in quit-restore parameter.
      (when (and (integerp (nth 3 quad))
                 (/= (nth 3 quad) (window-total-size window)))
        ;; Try to resize WINDOW to its old height but don't signal an
        ;; error.
        (condition-case nil
            (window-resize window (- (nth 3 quad) (window-total-size window)))
          (error nil)))
      (set-window-dedicated-p window nil)
      ;; Restore WINDOW's previous buffer, start and point position.
      (set-window-buffer-start-and-point
       window (nth 0 quad) (nth 1 quad) (nth 2 quad))
      ;; Deal with the buffer we just removed from WINDOW.
      (setq entry (and (eq bury-or-kill 'append)
                       (assq buffer (window-prev-buffers window))))
      (when bury-or-kill
        ;; Remove buffer from WINDOW's previous and next buffers.
        (set-window-prev-buffers
         window (assq-delete-all buffer (window-prev-buffers window)))
        (set-window-next-buffers
         window (delq buffer (window-next-buffers window))))
      (when entry
        ;; Append old buffer's entry to list of WINDOW's previous
        ;; buffers so it's less likely to get switched to soon but
        ;; `display-buffer-in-previous-window' can nevertheless find it.
        (set-window-prev-buffers
         window (append (window-prev-buffers window) (list entry))))
      ;; Reset the quit-restore parameter.
      (set-window-parameter window 'quit-restore nil)
      ;; Select old window.
      (when (window-live-p (nth 2 quit-restore))
        (select-window (nth 2 quit-restore))))
     (t
      ;; Show some other buffer in WINDOW and reset the quit-restore
      ;; parameter.
      (set-window-parameter window 'quit-restore nil)
      ;; Make sure that WINDOW is no more dedicated.
      (set-window-dedicated-p window nil)
      (switch-to-prev-buffer window bury-or-kill)))

    ;; Deal with the buffer.
    (cond
     ((not (buffer-live-p buffer)))
     ((eq bury-or-kill 'kill)
      (kill-buffer buffer))
     (bury-or-kill
      (bury-buffer-internal buffer)))))

(defun quit-window (&optional kill window)
  "Quit WINDOW and bury its buffer.
WINDOW must be a live window and defaults to the selected one.
With prefix argument KILL non-nil, kill the buffer instead of
burying it.

According to information stored in WINDOW's `quit-restore' window
parameter either (1) delete WINDOW and its frame, (2) delete
WINDOW, (3) restore the buffer previously displayed in WINDOW,
or (4) make WINDOW display some other buffer than the present
one.  If non-nil, reset `quit-restore' parameter to nil."
  (interactive "P")
  (quit-restore-window window (if kill 'kill 'bury)))

(defun quit-windows-on (&optional buffer-or-name kill frame)
  "Quit all windows showing BUFFER-OR-NAME.
BUFFER-OR-NAME may be a buffer or the name of an existing buffer
and defaults to the current buffer.  Optional argument KILL
non-nil means to kill BUFFER-OR-NAME.  KILL nil means to bury
BUFFER-OR-NAME.  Optional argument FRAME is handled as by
`delete-windows-on'.

This function calls `quit-window' on all candidate windows
showing BUFFER-OR-NAME."
  (interactive "BQuit windows on (buffer):\nP")
  (let ((buffer (window-normalize-buffer buffer-or-name))
        ;; Handle the "inverted" meaning of the FRAME argument wrt other
        ;; `window-list-1' based function.
        (all-frames (cond ((not frame) t) ((eq frame t) nil) (t frame))))
    (dolist (window (window-list-1 nil nil all-frames))
      (if (eq (window-buffer window) buffer)
          (quit-window kill window)
        ;; If a window doesn't show BUFFER, unrecord BUFFER in it.
        (unrecord-window-buffer window buffer)))))
\f
;;; Splitting windows.
(defun window-split-min-size (&optional horizontal)
  "Return minimum height of any window when splitting windows.
Optional argument HORIZONTAL non-nil means return minimum width."
  (if horizontal
      (max window-min-width window-safe-min-width)
    (max window-min-height window-safe-min-height)))

(defun split-window (&optional window size side)
  "Make a new window adjacent to WINDOW.
WINDOW must be a valid window and defaults to the selected one.
Return the new window which is always a live window.

Optional argument SIZE a positive number means make WINDOW SIZE
lines or columns tall.  If SIZE is negative, make the new window
-SIZE lines or columns tall.  If and only if SIZE is non-nil, its
absolute value can be less than `window-min-height' or
`window-min-width'; so this command can make a new window as
small as one line or two columns.  SIZE defaults to half of
WINDOW's size.  Interactively, SIZE is the prefix argument.

Optional third argument SIDE nil (or `below') specifies that the
new window shall be located below WINDOW.  SIDE `above' means the
new window shall be located above WINDOW.  In both cases SIZE
specifies the new number of lines for WINDOW (or the new window
if SIZE is negative) including space reserved for the mode and/or
header line.

SIDE t (or `right') specifies that the new window shall be
located on the right side of WINDOW.  SIDE `left' means the new
window shall be located on the left of WINDOW.  In both cases
SIZE specifies the new number of columns for WINDOW (or the new
window provided SIZE is negative) including space reserved for
fringes and the scrollbar or a divider column.  Any other non-nil
value for SIDE is currently handled like t (or `right').

If the variable `ignore-window-parameters' is non-nil or the
`split-window' parameter of WINDOW equals t, do not process any
parameters of WINDOW.  Otherwise, if the `split-window' parameter
of WINDOW specifies a function, call that function with all three
arguments and return the value returned by that function.

Otherwise, if WINDOW is part of an atomic window, \"split\" the
root of that atomic window.  The new window does not become a
member of that atomic window.

If WINDOW is live, properties of the new window like margins and
scrollbars are inherited from WINDOW.  If WINDOW is an internal
window, these properties as well as the buffer displayed in the
new window are inherited from the window selected on WINDOW's
frame.  The selected window is not changed by this function."
  (interactive "i")
  (setq window (window-normalize-window window))
  (let* ((side (cond
                ((not side) 'below)
                ((memq side '(below above right left)) side)
                (t 'right)))
         (horizontal (not (memq side '(below above))))
         (frame (window-frame window))
         (parent (window-parent window))
         (function (window-parameter window 'split-window))
         (window-side (window-parameter window 'window-side))
         ;; Rebind `window-combination-limit' and
         ;; `window-combination-resize' since in some cases we may have
         ;; to override their value.
         (window-combination-limit window-combination-limit)
         (window-combination-resize window-combination-resize)
         atom-root)

    (window--check frame)
    (catch 'done
      (cond
       ;; Ignore window parameters if either `ignore-window-parameters'
       ;; is t or the `split-window' parameter equals t.
       ((or ignore-window-parameters (eq function t)))
       ((functionp function)
        ;; The `split-window' parameter specifies the function to call.
        ;; If that function is `ignore', do nothing.
        (throw 'done (funcall function window size side)))
       ;; If WINDOW is part of an atomic window, split the root window
       ;; of that atomic window instead.
       ((and (window-parameter window 'window-atom)
             (setq atom-root (window-atom-root window))
             (not (eq atom-root window)))
        (throw 'done (split-window atom-root size side)))
       ;; If WINDOW is a side window or its first or last child is a
       ;; side window, throw an error unless `window-combination-resize'
       ;; equals 'side.
       ((and (not (eq window-combination-resize 'side))
             (or (window-parameter window 'window-side)
                 (and (window-child window)
                      (or (window-parameter
                           (window-child window) 'window-side)
                          (window-parameter
                           (window-last-child window) 'window-side)))))
        (error "Cannot split side window or parent of side window"))
       ;; If `window-combination-resize' is 'side and window has a side
       ;; window sibling, bind `window-combination-limit' to t.
       ((and (not (eq window-combination-resize 'side))
             (or (and (window-prev-sibling window)
                      (window-parameter
                       (window-prev-sibling window) 'window-side))
                 (and (window-next-sibling window)
                      (window-parameter
                       (window-next-sibling window) 'window-side))))
        (setq window-combination-limit t)))

      ;; If `window-combination-resize' is t and SIZE is non-negative,
      ;; bind `window-combination-limit' to t.
      (when (and (eq window-combination-resize t) size (> size 0))
        (setq window-combination-limit t))

      (let* ((parent-size
              ;; `parent-size' is the size of WINDOW's parent, provided
              ;; it has one.
              (when parent (window-total-size parent horizontal)))
             ;; `resize' non-nil means we are supposed to resize other
             ;; windows in WINDOW's combination.
             (resize
              (and window-combination-resize
                   (or (window-parameter window 'window-side)
                       (not (eq window-combination-resize 'side)))
                   (not window-combination-limit)
                   ;; Resize makes sense in iso-combinations only.
                   (window-combined-p window horizontal)))
             ;; `old-size' is the current size of WINDOW.
             (old-size (window-total-size window horizontal))
             ;; `new-size' is the specified or calculated size of the
             ;; new window.
             (new-size
              (cond
               ((not size)
                (max (window-split-min-size horizontal)
                     (if resize
                         ;; When resizing try to give the new window the
                         ;; average size of a window in its combination.
                         (min (- parent-size
                                 (window-min-size parent horizontal))
                              (/ parent-size
                                 (1+ (window-combinations
                                      parent horizontal))))
                       ;; Else try to give the new window half the size
                       ;; of WINDOW (plus an eventual odd line).
                       (+ (/ old-size 2) (% old-size 2)))))
               ((>= size 0)
                ;; SIZE non-negative specifies the new size of WINDOW.

                ;; Note: Specifying a non-negative SIZE is practically
                ;; always done as workaround for making the new window
                ;; appear above or on the left of the new window (the
                ;; ispell window is a typical example of that).  In all
                ;; these cases the SIDE argument should be set to 'above
                ;; or 'left in order to support the 'resize option.
                ;; Here we have to nest the windows instead, see above.
                (- old-size size))
               (t
                ;; SIZE negative specifies the size of the new window.
                (- size))))
             new-parent new-normal)

        ;; Check SIZE.
        (cond
         ((not size)
          (cond
           (resize
            ;; SIZE unspecified, resizing.
            (when (and (not (window-sizable-p parent (- new-size) horizontal))
                       ;; Try again with minimum split size.
                       (setq new-size
                             (max new-size (window-split-min-size horizontal)))
                       (not (window-sizable-p parent (- new-size) horizontal)))
              (error "Window %s too small for splitting" parent)))
           ((> (+ new-size (window-min-size window horizontal)) old-size)
            ;; SIZE unspecified, no resizing.
            (error "Window %s too small for splitting" window))))
         ((and (>= size 0)
               (or (>= size old-size)
                   (< new-size (if horizontal
                                   window-safe-min-width
                                 window-safe-min-width))))
          ;; SIZE specified as new size of old window.  If the new size
          ;; is larger than the old size or the size of the new window
          ;; would be less than the safe minimum, signal an error.
          (error "Window %s too small for splitting" window))
         (resize
          ;; SIZE specified, resizing.
          (unless (window-sizable-p parent (- new-size) horizontal)
            ;; If we cannot resize the parent give up.
            (error "Window %s too small for splitting" parent)))
         ((or (< new-size
                 (if horizontal window-safe-min-width window-safe-min-height))
              (< (- old-size new-size)
                 (if horizontal window-safe-min-width window-safe-min-height)))
          ;; SIZE specification violates minimum size restrictions.
          (error "Window %s too small for splitting" window)))

        (window--resize-reset frame horizontal)

        (setq new-parent
              ;; Make new-parent non-nil if we need a new parent window;
              ;; either because we want to nest or because WINDOW is not
              ;; iso-combined.
              (or window-combination-limit
                  (not (window-combined-p window horizontal))))
        (setq new-normal
              ;; Make new-normal the normal size of the new window.
              (cond
               (size (/ (float new-size) (if new-parent old-size parent-size)))
               (new-parent 0.5)
               (resize (/ 1.0 (1+ (window-combinations parent horizontal))))
               (t (/ (window-normal-size window horizontal) 2.0))))

        (if resize
            ;; Try to get space from OLD's siblings.  We could go "up" and
            ;; try getting additional space from surrounding windows but
            ;; we won't be able to return space to those windows when we
            ;; delete the one we create here.  Hence we do not go up.
            (progn
              (window--resize-child-windows parent (- new-size) horizontal)
              (let* ((normal (- 1.0 new-normal))
                     (sub (window-child parent)))
                (while sub
                  (set-window-new-normal
                   sub (* (window-normal-size sub horizontal) normal))
                  (setq sub (window-right sub)))))
          ;; Get entire space from WINDOW.
          (set-window-new-total window (- old-size new-size))
          (window--resize-this-window window (- new-size) horizontal)
          (set-window-new-normal
           window (- (if new-parent 1.0 (window-normal-size window horizontal))
                     new-normal)))

        (let* ((new (split-window-internal window new-size side new-normal)))
          ;; Assign window-side parameters, if any.
          (when (eq window-combination-resize 'side)
            (let ((window-side
                   (cond
                    (window-side window-side)
                    ((eq side 'above) 'top)
                    ((eq side 'below) 'bottom)
                    (t side))))
              ;; We made a new side window.
              (set-window-parameter new 'window-side window-side)
              (when (and new-parent (window-parameter window 'window-side))
                ;; We've been splitting a side root window.  Give the
                ;; new parent the same window-side parameter.
                (set-window-parameter
                 (window-parent new) 'window-side window-side))))

          (run-window-configuration-change-hook frame)
          (window--check frame)
          ;; Always return the new window.
          new)))))

;; I think this should be the default; I think people will prefer it--rms.
(defcustom split-window-keep-point t
  "If non-nil, \\[split-window-below] preserves point in the new window.
If nil, adjust point in the two windows to minimize redisplay.
This option applies only to `split-window-below' and functions
that call it.  The low-level `split-window' function always keeps
the original point in both windows."
  :type 'boolean
  :group 'windows)

(defun split-window-below (&optional size)
  "Split the selected window into two windows, one above the other.
The selected window is above.  The newly split-off window is
below, and displays the same buffer.  Return the new window.

If optional argument SIZE is omitted or nil, both windows get the
same height, or close to it.  If SIZE is positive, the upper
\(selected) window gets SIZE lines.  If SIZE is negative, the
lower (new) window gets -SIZE lines.

If the variable `split-window-keep-point' is non-nil, both
windows get the same value of point as the selected window.
Otherwise, the window starts are chosen so as to minimize the
amount of redisplay; this is convenient on slow terminals."
  (interactive "P")
  (let ((old-window (selected-window))
        (old-point (window-point))
        (size (and size (prefix-numeric-value size)))
        moved-by-window-height moved new-window bottom)
    (when (and size (< size 0) (< (- size) window-min-height))
      ;; `split-window' would not signal an error here.
      (error "Size of new window too small"))
    (setq new-window (split-window nil size))
    (unless split-window-keep-point
      (with-current-buffer (window-buffer)
        ;; Use `save-excursion' around vertical movements below
        ;; (Bug#10971).  Note: When the selected window's buffer has a
        ;; header line, up to two lines of the buffer may not show up
        ;; in the resulting configuration.
        (save-excursion
          (goto-char (window-start))
          (setq moved (vertical-motion (window-height)))
          (set-window-start new-window (point))
          (when (> (point) (window-point new-window))
            (set-window-point new-window (point)))
          (when (= moved (window-height))
            (setq moved-by-window-height t)
            (vertical-motion -1))
          (setq bottom (point)))
        (and moved-by-window-height
             (<= bottom (point))
             (set-window-point old-window (1- bottom)))
        (and moved-by-window-height
             (<= (window-start new-window) old-point)
             (set-window-point new-window old-point)
             (select-window new-window))))
    ;; Always copy quit-restore parameter in interactive use.
    (let ((quit-restore (window-parameter old-window 'quit-restore)))
      (when quit-restore
        (set-window-parameter new-window 'quit-restore quit-restore)))
    new-window))

(defalias 'split-window-vertically 'split-window-below)

(defun split-window-right (&optional size)
  "Split the selected window into two side-by-side windows.
The selected window is on the left.  The newly split-off window
is on the right, and displays the same buffer.  Return the new
window.

If optional argument SIZE is omitted or nil, both windows get the
same width, or close to it.  If SIZE is positive, the left-hand
\(selected) window gets SIZE columns.  If SIZE is negative, the
right-hand (new) window gets -SIZE columns.  Here, SIZE includes
the width of the window's scroll bar; if there are no scroll
bars, it includes the width of the divider column to the window's
right, if any."
  (interactive "P")
  (let ((old-window (selected-window))
        (size (and size (prefix-numeric-value size)))
        new-window)
    (when (and size (< size 0) (< (- size) window-min-width))
      ;; `split-window' would not signal an error here.
      (error "Size of new window too small"))
    (setq new-window (split-window nil size t))
    ;; Always copy quit-restore parameter in interactive use.
    (let ((quit-restore (window-parameter old-window 'quit-restore)))
      (when quit-restore
        (set-window-parameter new-window 'quit-restore quit-restore)))
    new-window))

(defalias 'split-window-horizontally 'split-window-right)
\f
;;; Balancing windows.

;; The following routine uses the recycled code from an old version of
;; `window--resize-child-windows'.  It's not very pretty, but coding it the way the
;; new `window--resize-child-windows' code does would hardly make it any shorter or
;; more readable (FWIW we'd need three loops - one to calculate the
;; minimum sizes per window, one to enlarge or shrink windows until the
;; new parent-size matches, and one where we shrink the largest/enlarge
;; the smallest window).
(defun balance-windows-2 (window horizontal)
  "Subroutine of `balance-windows-1'.
WINDOW must be a vertical combination (horizontal if HORIZONTAL
is non-nil)."
  (let* ((first (window-child window))
         (sub first)
         (number-of-children 0)
         (parent-size (window-new-total window))
         (total-sum parent-size)
         failed size sub-total sub-delta sub-amount rest)
    (while sub
      (setq number-of-children (1+ number-of-children))
      (when (window-size-fixed-p sub horizontal)
        (setq total-sum
              (- total-sum (window-total-size sub horizontal)))
        (set-window-new-normal sub 'ignore))
      (setq sub (window-right sub)))

    (setq failed t)
    (while (and failed (> number-of-children 0))
      (setq size (/ total-sum number-of-children))
      (setq failed nil)
      (setq sub first)
      (while (and sub (not failed))
        ;; Ignore child windows that should be ignored or are stuck.
        (unless (window--resize-child-windows-skip-p sub)
          (setq sub-total (window-total-size sub horizontal))
          (setq sub-delta (- size sub-total))
          (setq sub-amount
                (window-sizable sub sub-delta horizontal))
          ;; Register the new total size for this child window.
          (set-window-new-total sub (+ sub-total sub-amount))
          (unless (= sub-amount sub-delta)
            (setq total-sum (- total-sum sub-total sub-amount))
            (setq number-of-children (1- number-of-children))
            ;; We failed and need a new round.
            (setq failed t)
            (set-window-new-normal sub 'skip)))
        (setq sub (window-right sub))))

    (setq rest (% total-sum number-of-children))
    ;; Fix rounding by trying to enlarge non-stuck windows by one line
    ;; (column) until `rest' is zero.
    (setq sub first)
    (while (and sub (> rest 0))
      (unless (window--resize-child-windows-skip-p window)
        (set-window-new-total sub 1 t)
        (setq rest (1- rest)))
      (setq sub (window-right sub)))

    ;; Fix rounding by trying to enlarge stuck windows by one line
    ;; (column) until `rest' equals zero.
    (setq sub first)
    (while (and sub (> rest 0))
      (unless (eq (window-new-normal sub) 'ignore)
        (set-window-new-total sub 1 t)
        (setq rest (1- rest)))
      (setq sub (window-right sub)))

    (setq sub first)
    (while sub
      ;; Record new normal sizes.
      (set-window-new-normal
       sub (/ (if (eq (window-new-normal sub) 'ignore)
                  (window-total-size sub horizontal)
                (window-new-total sub))
              (float parent-size)))
      ;; Recursively balance each window's child windows.
      (balance-windows-1 sub horizontal)
      (setq sub (window-right sub)))))

(defun balance-windows-1 (window &optional horizontal)
  "Subroutine of `balance-windows'."
  (if (window-child window)
      (let ((sub (window-child window)))
        (if (window-combined-p sub horizontal)
            (balance-windows-2 window horizontal)
          (let ((size (window-new-total window)))
            (while sub
              (set-window-new-total sub size)
              (balance-windows-1 sub horizontal)
              (setq sub (window-right sub))))))))

(defun balance-windows (&optional window-or-frame)
  "Balance the sizes of windows of WINDOW-OR-FRAME.
WINDOW-OR-FRAME is optional and defaults to the selected frame.
If WINDOW-OR-FRAME denotes a frame, balance the sizes of all
windows of that frame.  If WINDOW-OR-FRAME denotes a window,
recursively balance the sizes of all child windows of that
window."
  (interactive)
  (let* ((window
          (cond
           ((or (not window-or-frame)
                (frame-live-p window-or-frame))
            (frame-root-window window-or-frame))
           ((or (window-live-p window-or-frame)
                (window-child window-or-frame))
            window-or-frame)
           (t
            (error "Not a window or frame %s" window-or-frame))))
         (frame (window-frame window)))
    ;; Balance vertically.
    (window--resize-reset (window-frame window))
    (balance-windows-1 window)
    (window-resize-apply frame)
    ;; Balance horizontally.
    (window--resize-reset (window-frame window) t)
    (balance-windows-1 window t)
    (window-resize-apply frame t)))

(defun window-fixed-size-p (&optional window direction)
  "Return t if WINDOW cannot be resized in DIRECTION.
WINDOW defaults to the selected window.  DIRECTION can be
nil (i.e. any), `height' or `width'."
  (with-current-buffer (window-buffer window)
    (when (and (boundp 'window-size-fixed) window-size-fixed)
      (not (and direction
                (member (cons direction window-size-fixed)
                        '((height . width) (width . height))))))))

;;; A different solution to balance-windows.
(defvar window-area-factor 1
  "Factor by which the window area should be over-estimated.
This is used by `balance-windows-area'.
Changing this globally has no effect.")
(make-variable-buffer-local 'window-area-factor)

(defun balance-windows-area-adjust (window delta horizontal)
  "Wrapper around `window-resize' with error checking.
Arguments WINDOW, DELTA and HORIZONTAL are passed on to that function."
  ;; `window-resize' may fail if delta is too large.
  (while (>= (abs delta) 1)
    (condition-case nil
        (progn
          (window-resize window delta horizontal)
          (setq delta 0))
      (error
       ;;(message "adjust: %s" (error-message-string err))
       (setq delta (/ delta 2))))))

(defun balance-windows-area ()
  "Make all visible windows the same area (approximately).
See also `window-area-factor' to change the relative size of
specific buffers."
  (interactive)
  (let* ((unchanged 0) (carry 0) (round 0)
         ;; Remove fixed-size windows.
         (wins (delq nil (mapcar (lambda (win)
                                   (if (not (window-fixed-size-p win)) win))
                                 (window-list nil 'nomini))))
         (changelog nil)
         next)
    ;; Resizing a window changes the size of surrounding windows in complex
    ;; ways, so it's difficult to balance them all.  The introduction of
    ;; `adjust-window-trailing-edge' made it a bit easier, but it is still
    ;; very difficult to do.  `balance-window' above takes an off-line
    ;; approach: get the whole window tree, then balance it, then try to
    ;; adjust the windows so they fit the result.
    ;; Here, instead, we take a "local optimization" approach, where we just
    ;; go through all the windows several times until nothing needs to be
    ;; changed.  The main problem with this approach is that it's difficult
    ;; to make sure it terminates, so we use some heuristic to try and break
    ;; off infinite loops.
    ;; After a round without any change, we allow a second, to give a chance
    ;; to the carry to propagate a minor imbalance from the end back to
    ;; the beginning.
    (while (< unchanged 2)
      ;; (message "New round")
      (setq unchanged (1+ unchanged) round (1+ round))
      (dolist (win wins)
        (setq next win)
        (while (progn (setq next (next-window next))
                      (window-fixed-size-p next)))
        ;; (assert (eq next (or (cadr (member win wins)) (car wins))))
        (let* ((horiz
                (< (car (window-edges win)) (car (window-edges next))))
               (areadiff (/ (- (* (window-height next) (window-width next)
                                  (buffer-local-value 'window-area-factor
                                                      (window-buffer next)))
                               (* (window-height win) (window-width win)
                                  (buffer-local-value 'window-area-factor
                                                      (window-buffer win))))
                            (max (buffer-local-value 'window-area-factor
                                                     (window-buffer win))
                                 (buffer-local-value 'window-area-factor
                                                     (window-buffer next)))))
               (edgesize (if horiz
                             (+ (window-height win) (window-height next))
                           (+ (window-width win) (window-width next))))
               (diff (/ areadiff edgesize)))
          (when (zerop diff)
            ;; Maybe diff is actually closer to 1 than to 0.
            (setq diff (/ (* 3 areadiff) (* 2 edgesize))))
          (when (and (zerop diff) (not (zerop areadiff)))
            (setq diff (/ (+ areadiff carry) edgesize))
            ;; Change things smoothly.
            (if (or (> diff 1) (< diff -1)) (setq diff (/ diff 2))))
          (if (zerop diff)
              ;; Make sure negligible differences don't accumulate to
              ;; become significant.
              (setq carry (+ carry areadiff))
            ;; This used `adjust-window-trailing-edge' before and uses
            ;; `window-resize' now.  Error wrapping is still needed.
            (balance-windows-area-adjust win diff horiz)
            ;; (sit-for 0.5)
            (let ((change (cons win (window-edges win))))
              ;; If the same change has been seen already for this window,
              ;; we're most likely in an endless loop, so don't count it as
              ;; a change.
              (unless (member change changelog)
                (push change changelog)
                (setq unchanged 0 carry 0)))))))
    ;; We've now basically balanced all the windows.
    ;; But there may be some minor off-by-one imbalance left over,
    ;; so let's do some fine tuning.
    ;; (bw-finetune wins)
    ;; (message "Done in %d rounds" round)
    ))

;;; Window states, how to get them and how to put them in a window.
(defun window--state-get-1 (window &optional writable)
  "Helper function for `window-state-get'."
  (let* ((type
          (cond
           ((window-top-child window) 'vc)
           ((window-left-child window) 'hc)
           (t 'leaf)))
         (buffer (window-buffer window))
         (selected (eq window (selected-window)))
         (head
          `(,type
            ,@(unless (window-next-sibling window) `((last . t)))
            (total-height . ,(window-total-size window))
            (total-width . ,(window-total-size window t))
            (normal-height . ,(window-normal-size window))
            (normal-width . ,(window-normal-size window t))
            (combination-limit . ,(window-combination-limit window))
            ,@(let ((parameters (window-parameters window))
                    list)
                ;; Make copies of those window parameters whose
                ;; persistence property is `writable' if WRITABLE is
                ;; non-nil and non-nil if WRITABLE is nil.
                (dolist (par parameters)
                  (let ((pers (cdr (assq (car par)
                                         window-persistent-parameters))))
                    (when (and pers (or (not writable) (eq pers 'writable)))
                      (setq list (cons (cons (car par) (cdr par)) list)))))
                ;; Add `clone-of' parameter if necessary.
                (let ((pers (cdr (assq 'clone-of
                                       window-persistent-parameters))))
                  (when (and pers (or (not writable) (eq pers 'writable))
                             (not (assq 'clone-of list)))
                    (setq list (cons (cons 'clone-of window) list))))
                (when list
                  `((parameters . ,list))))
            ,@(when buffer
                ;; All buffer related things go in here.
                (let ((point (window-point window))
                      (start (window-start window)))
                  `((buffer
                     ,(buffer-name buffer)
                     (selected . ,selected)
                     (hscroll . ,(window-hscroll window))
                     (fringes . ,(window-fringes window))
                     (margins . ,(window-margins window))
                     (scroll-bars . ,(window-scroll-bars window))
                     (vscroll . ,(window-vscroll window))
                     (dedicated . ,(window-dedicated-p window))
                     (point . ,(if writable point
                                 (copy-marker point
                                              (buffer-local-value
                                               'window-point-insertion-type
                                               buffer))))
                     (start . ,(if writable start (copy-marker start)))))))))
         (tail
          (when (memq type '(vc hc))
            (let (list)
              (setq window (window-child window))
              (while window
                (setq list (cons (window--state-get-1 window writable) list))
                (setq window (window-right window)))
              (nreverse list)))))
    (append head tail)))

(defun window-state-get (&optional window writable)
  "Return state of WINDOW as a Lisp object.
WINDOW can be any window and defaults to the root window of the
selected frame.

Optional argument WRITABLE non-nil means do not use markers for
sampling `window-point' and `window-start'.  Together, WRITABLE
and the variable `window-persistent-parameters' specify which
window parameters are saved by this function.  WRITABLE should be
non-nil when the return value shall be written to a file and read
back in another session.  Otherwise, an application may run into
an `invalid-read-syntax' error while attempting to read back the
value from file.

The return value can be used as argument for `window-state-put'
to put the state recorded here into an arbitrary window.  The
value can be also stored on disk and read back in a new session."
  (setq window
        (if window
            (if (window-valid-p window)
                window
              (error "%s is not a live or internal window" window))
          (frame-root-window)))
  ;; The return value is a cons whose car specifies some constraints on
  ;; the size of WINDOW.  The cdr lists the states of the child windows
  ;; of WINDOW.
  (cons
   ;; Frame related things would go into a function, say `frame-state',
   ;; calling `window-state-get' to insert the frame's root window.
   `((min-height        . ,(window-min-size window))
     (min-width         . ,(window-min-size window t))
     (min-height-ignore . ,(window-min-size window nil t))
     (min-width-ignore  . ,(window-min-size window t t))
     (min-height-safe   . ,(window-min-size window nil 'safe))
     (min-width-safe    . ,(window-min-size window t 'safe)))
   (window--state-get-1 window writable)))

(defvar window-state-put-list nil
  "Helper variable for `window-state-put'.")

(defun window--state-put-1 (state &optional window ignore totals)
  "Helper function for `window-state-put'."
  (let ((type (car state)))
    (setq state (cdr state))
    (cond
     ((eq type 'leaf)
      ;; For a leaf window just add unprocessed entries to
      ;; `window-state-put-list'.
      (push (cons window state) window-state-put-list))
     ((memq type '(vc hc))
      (let* ((horizontal (eq type 'hc))
             (total (window-total-size window horizontal))
             (first t)
             size new)
        (dolist (item state)
          ;; Find the next child window.  WINDOW always points to the
          ;; real window that we want to fill with what we find here.
          (when (memq (car item) '(leaf vc hc))
            (if (assq 'last item)
                ;; The last child window.  Below `window--state-put-1'
                ;; will put into it whatever ITEM has in store.
                (setq new nil)
              ;; Not the last child window, prepare for splitting
              ;; WINDOW.  SIZE is the new (and final) size of the old
              ;; window.
              (setq size
                    (if totals
                        ;; Use total size.
                        (cdr (assq (if horizontal 'total-width 'total-height) item))
                      ;; Use normalized size and round.
                      (round (* total
                                (cdr (assq
                                      (if horizontal 'normal-width 'normal-height)
                                      item))))))

              ;; Use safe sizes, we try to resize later.
              (setq size (max size (if horizontal
                                       window-safe-min-height
                                     window-safe-min-width)))

              (if (window-sizable-p window (- size) horizontal 'safe)
                  (let* ((window-combination-limit
                          (assq 'combination-limit item)))
                    ;; We must inherit the combination limit, otherwise
                    ;; we might mess up handling of atomic and side
                    ;; window.
                    (setq new (split-window window size horizontal)))
                ;; Give up if we can't resize window down to safe sizes.
                (error "Cannot resize window %s" window))

              (when first
                (setq first nil)
                ;; When creating the first child window add for parent
                ;; unprocessed entries to `window-state-put-list'.
                (setq window-state-put-list
                      (cons (cons (window-parent window) state)
                            window-state-put-list))))

            ;; Now process the current window (either the one we've just
            ;; split or the last child of its parent).
            (window--state-put-1 item window ignore totals)
            ;; Continue with the last window split off.
            (setq window new))))))))

(defun window--state-put-2 (ignore)
  "Helper function for `window-state-put'."
  (dolist (item window-state-put-list)
    (let ((window (car item))
          (combination-limit (cdr (assq 'combination-limit item)))
          (parameters (cdr (assq 'parameters item)))
          (state (cdr (assq 'buffer item))))
      (when combination-limit
        (set-window-combination-limit window combination-limit))
      ;; Reset window's parameters and assign saved ones (we might want
      ;; a `remove-window-parameters' function here).
      (dolist (parameter (window-parameters window))
        (set-window-parameter window (car parameter) nil))
      (when parameters
        (dolist (parameter parameters)
          (set-window-parameter window (car parameter) (cdr parameter))))
      ;; Process buffer related state.
      (when state
        ;; We don't want to raise an error here so we create a buffer if
        ;; there's none.
        (set-window-buffer window (get-buffer-create (car state)))
        (with-current-buffer (window-buffer window)
          (set-window-hscroll window (cdr (assq 'hscroll state)))
          (apply 'set-window-fringes
                 (cons window (cdr (assq 'fringes state))))
          (let ((margins (cdr (assq 'margins state))))
            (set-window-margins window (car margins) (cdr margins)))
          (let ((scroll-bars (cdr (assq 'scroll-bars state))))
            (set-window-scroll-bars
             window (car scroll-bars) (nth 2 scroll-bars) (nth 3 scroll-bars)))
          (set-window-vscroll window (cdr (assq 'vscroll state)))
          ;; Adjust vertically.
          (if (memq window-size-fixed '(t height))
              ;; A fixed height window, try to restore the original size.
              (let ((delta (- (cdr (assq 'total-height item))
                              (window-total-height window)))
                    window-size-fixed)
                (when (window--resizable-p window delta)
                  (window-resize window delta)))
            ;; Else check whether the window is not high enough.
            (let* ((min-size (window-min-size window nil ignore))
                   (delta (- min-size (window-total-size window))))
              (when (and (> delta 0)
                         (window--resizable-p window delta nil ignore))
                (window-resize window delta nil ignore))))
          ;; Adjust horizontally.
          (if (memq window-size-fixed '(t width))
              ;; A fixed width window, try to restore the original size.
              (let ((delta (- (cdr (assq 'total-width item))
                              (window-total-width window)))
                    window-size-fixed)
                (when (window--resizable-p window delta)
                  (window-resize window delta)))
            ;; Else check whether the window is not wide enough.
            (let* ((min-size (window-min-size window t ignore))
                   (delta (- min-size (window-total-size window t))))
              (when (and (> delta 0)
                         (window--resizable-p window delta t ignore))
                (window-resize window delta t ignore))))
          ;; Set dedicated status.
          (set-window-dedicated-p window (cdr (assq 'dedicated state)))
          ;; Install positions (maybe we should do this after all windows
          ;; have been created and sized).
          (ignore-errors
            (set-window-start window (cdr (assq 'start state)))
            (set-window-point window (cdr (assq 'point state))))
          ;; Select window if it's the selected one.
          (when (cdr (assq 'selected state))
            (select-window window)))))))

(defun window-state-put (state &optional window ignore)
  "Put window state STATE into WINDOW.
STATE should be the state of a window returned by an earlier
invocation of `window-state-get'.  Optional argument WINDOW must
specify a live window and defaults to the selected one.

Optional argument IGNORE non-nil means ignore minimum window
sizes and fixed size restrictions.  IGNORE equal `safe' means
windows can get as small as `window-safe-min-height' and
`window-safe-min-width'."
  (setq window (window-normalize-window window t))
  (let* ((frame (window-frame window))
         (head (car state))
         ;; We check here (1) whether the total sizes of root window of
         ;; STATE and that of WINDOW are equal so we can avoid
         ;; calculating new sizes, and (2) if we do have to resize
         ;; whether we can do so without violating size restrictions.
         (totals
          (and (= (window-total-size window)
                  (cdr (assq 'total-height state)))
               (= (window-total-size window t)
                  (cdr (assq 'total-width state)))))
         (min-height (cdr (assq 'min-height head)))
         (min-width (cdr (assq 'min-width head))))
    (if (and (not totals)
             (or (> min-height (window-total-size window))
                 (> min-width (window-total-size window t)))
             (or (not ignore)
                 (and (setq min-height
                            (cdr (assq 'min-height-ignore head)))
                      (setq min-width
                            (cdr (assq 'min-width-ignore head)))
                      (or (> min-height (window-total-size window))
                          (> min-width (window-total-size window t)))
                      (or (not (eq ignore 'safe))
                          (and (setq min-height
                                     (cdr (assq 'min-height-safe head)))
                               (setq min-width
                                     (cdr (assq 'min-width-safe head)))
                               (or (> min-height
                                      (window-total-size window))
                                   (> min-width
                                      (window-total-size window t))))))))
        ;; The check above might not catch all errors due to rounding
        ;; issues - so IGNORE equal 'safe might not always produce the
        ;; minimum possible state.  But such configurations hardly make
        ;; sense anyway.
        (error "Window %s too small to accommodate state" window)
      (setq state (cdr state))
      (setq window-state-put-list nil)
      ;; Work on the windows of a temporary buffer to make sure that
      ;; splitting proceeds regardless of any buffer local values of
      ;; `window-size-fixed'.  Release that buffer after the buffers of
      ;; all live windows have been set by `window--state-put-2'.
      (with-temp-buffer
        (set-window-buffer window (current-buffer))
        (window--state-put-1 state window nil totals)
        (window--state-put-2 ignore))
      (window--check frame))))
\f
(defun display-buffer-record-window (type window buffer)
  "Record information for window used by `display-buffer'.
TYPE specifies the type of the calling operation and must be one
of the symbols 'reuse (when WINDOW existed already and was
reused for displaying BUFFER), 'window (when WINDOW was created
on an already existing frame), or 'frame (when WINDOW was
created on a new frame).  WINDOW is the window used for or created
by the `display-buffer' routines.  BUFFER is the buffer that
shall be displayed.

This function installs or updates the quit-restore parameter of
WINDOW.  The quit-restore parameter is a list of four elements:
The first element is one of the symbols 'window, 'frame, 'same or
'other.  The second element is either one of the symbols 'window
or 'frame or a list whose elements are the buffer previously
shown in the window, that buffer's window start and window point,
and the window's height.  The third element is the window
selected at the time the parameter was created.  The fourth
element is BUFFER."
  (cond
   ((eq type 'reuse)
    (if (eq (window-buffer window) buffer)
        ;; WINDOW shows BUFFER already.
        (when (consp (window-parameter window 'quit-restore))
          ;; If WINDOW has a quit-restore parameter, reset its car.
          (setcar (window-parameter window 'quit-restore) 'same))
      ;; WINDOW shows another buffer.
      (set-window-parameter
       window 'quit-restore
       (list 'other
             ;; A quadruple of WINDOW's buffer, start, point and height.
             (list (window-buffer window) (window-start window)
                   (window-point window) (window-total-size window))
             (selected-window) buffer))))
   ((eq type 'window)
    ;; WINDOW has been created on an existing frame.
    (set-window-parameter
     window 'quit-restore
     (list 'window 'window (selected-window) buffer)))
   ((eq type 'frame)
    ;; WINDOW has been created on a new frame.
    (set-window-parameter
     window 'quit-restore
     (list 'frame 'frame (selected-window) buffer)))))

(defcustom display-buffer-function nil
  "If non-nil, function to call to handle `display-buffer'.
It will receive two args, the buffer and a flag which if non-nil
means that the currently selected window is not acceptable.  It
should choose or create a window, display the specified buffer in
it, and return the window.

The specified function should call `display-buffer-record-window'
with corresponding arguments to set up the quit-restore parameter
of the window used."
  :type '(choice
          (const nil)
          (function :tag "function"))
  :group 'windows)

;; Eventually, we want to turn this into a defvar; instead of
;; customizing this, the user should use a `pop-up-frame-parameters'
;; alist entry in `display-buffer-base-action'.
(defcustom pop-up-frame-alist nil
  "Alist of parameters for automatically generated new frames.
If non-nil, the value you specify here is used by the default
`pop-up-frame-function' for the creation of new frames.

Since `pop-up-frame-function' is used by `display-buffer' for
making new frames, any value specified here by default affects
the automatic generation of new frames via `display-buffer' and
all functions based on it.  The behavior of `make-frame' is not
affected by this variable."
  :type '(repeat (cons :format "%v"
                       (symbol :tag "Parameter")
                       (sexp :tag "Value")))
  :group 'frames)

(defcustom pop-up-frame-function
  (lambda () (make-frame pop-up-frame-alist))
  "Function used by `display-buffer' for creating a new frame.
This function is called with no arguments and should return a new
frame.  The default value calls `make-frame' with the argument
`pop-up-frame-alist'."
  :type 'function
  :group 'frames)

(defcustom special-display-buffer-names nil
  "List of names of buffers that should be displayed specially.
Displaying a buffer with `display-buffer' or `pop-to-buffer', if
its name is in this list, displays the buffer in a way specified
by `special-display-function'.  `special-display-popup-frame'
\(the default for `special-display-function') usually displays
the buffer in a separate frame made with the parameters specified
by `special-display-frame-alist'.  If `special-display-function'
has been set to some other function, that function is called with
the buffer as first, and nil as second argument.

Alternatively, an element of this list can be specified as
\(BUFFER-NAME FRAME-PARAMETERS), where BUFFER-NAME is a buffer
name and FRAME-PARAMETERS an alist of (PARAMETER . VALUE) pairs.
`special-display-popup-frame' will interpret such pairs as frame
parameters when it creates a special frame, overriding the
corresponding values from `special-display-frame-alist'.

As a special case, if FRAME-PARAMETERS contains (same-window . t)
`special-display-popup-frame' displays that buffer in the
selected window.  If FRAME-PARAMETERS contains (same-frame . t),
it displays that buffer in a window on the selected frame.

If `special-display-function' specifies some other function than
`special-display-popup-frame', that function is called with the
buffer named BUFFER-NAME as first, and FRAME-PARAMETERS as second
argument.

Finally, an element of this list can be also specified as
\(BUFFER-NAME FUNCTION OTHER-ARGS).  In that case,
`special-display-popup-frame' will call FUNCTION with the buffer
named BUFFER-NAME as first argument, and OTHER-ARGS as the
second.

Any alternative function specified here is responsible for
setting up the quit-restore parameter of the window used.

If this variable appears \"not to work\", because you added a
name to it but the corresponding buffer is displayed in the
selected window, look at the values of `same-window-buffer-names'
and `same-window-regexps'.  Those variables take precedence over
this one.

See also `special-display-regexps'."
  :type '(repeat
          (choice :tag "Buffer"
                  :value ""
                  (string :format "%v")
                  (cons :tag "With parameters"
                        :format "%v"
                        :value ("" . nil)
                        (string :format "%v")
                        (repeat :tag "Parameters"
                                (cons :format "%v"
                                      (symbol :tag "Parameter")
                                      (sexp :tag "Value"))))
                  (list :tag "With function"
                        :format "%v"
                        :value ("" . nil)
                        (string :format "%v")
                        (function :tag "Function")
                        (repeat :tag "Arguments" (sexp)))))
  :group 'windows
  :group 'frames)
(make-obsolete-variable 'special-display-buffer-names 'display-buffer-alist "24.3")
(put 'special-display-buffer-names 'risky-local-variable t)

(defcustom special-display-regexps nil
  "List of regexps saying which buffers should be displayed specially.
Displaying a buffer with `display-buffer' or `pop-to-buffer', if
any regexp in this list matches its name, displays it specially
using `special-display-function'.  `special-display-popup-frame'
\(the default for `special-display-function') usually displays
the buffer in a separate frame made with the parameters specified
by `special-display-frame-alist'.  If `special-display-function'
has been set to some other function, that function is called with
the buffer as first, and nil as second argument.

Alternatively, an element of this list can be specified as
\(REGEXP FRAME-PARAMETERS), where REGEXP is a regexp as above and
FRAME-PARAMETERS an alist of (PARAMETER . VALUE) pairs.
`special-display-popup-frame' will then interpret these pairs as
frame parameters when creating a special frame for a buffer whose
name matches REGEXP, overriding the corresponding values from
`special-display-frame-alist'.

As a special case, if FRAME-PARAMETERS contains (same-window . t)
`special-display-popup-frame' displays buffers matching REGEXP in
the selected window.  (same-frame . t) in FRAME-PARAMETERS means
to display such buffers in a window on the selected frame.

If `special-display-function' specifies some other function than
`special-display-popup-frame', that function is called with the
buffer whose name matched REGEXP as first, and FRAME-PARAMETERS
as second argument.

Finally, an element of this list can be also specified as
\(REGEXP FUNCTION OTHER-ARGS).  `special-display-popup-frame'
will then call FUNCTION with the buffer whose name matched
REGEXP as first, and OTHER-ARGS as second argument.

Any alternative function specified here is responsible for
setting up the quit-restore parameter of the window used.

If this variable appears \"not to work\", because you added a
name to it but the corresponding buffer is displayed in the
selected window, look at the values of `same-window-buffer-names'
and `same-window-regexps'.  Those variables take precedence over
this one.

See also `special-display-buffer-names'."
  :type '(repeat
          (choice :tag "Buffer"
                  :value ""
                  (regexp :format "%v")
                  (cons :tag "With parameters"
                        :format "%v"
                        :value ("" . nil)
                        (regexp :format "%v")
                        (repeat :tag "Parameters"
                                (cons :format "%v"
                                      (symbol :tag "Parameter")
                                      (sexp :tag "Value"))))
                  (list :tag "With function"
                        :format "%v"
                        :value ("" . nil)
                        (regexp :format "%v")
                        (function :tag "Function")
                        (repeat :tag "Arguments" (sexp)))))
  :group 'windows
  :group 'frames)
(make-obsolete-variable 'special-display-regexps 'display-buffer-alist "24.3")
(put 'special-display-regexps 'risky-local-variable t)

(defun special-display-p (buffer-name)
  "Return non-nil if a buffer named BUFFER-NAME gets a special frame.
More precisely, return t if `special-display-buffer-names' or
`special-display-regexps' contain a string entry equaling or
matching BUFFER-NAME.  If `special-display-buffer-names' or
`special-display-regexps' contain a list entry whose car equals
or matches BUFFER-NAME, the return value is the cdr of that
entry."
  (let (tmp)
    (cond
     ((member buffer-name special-display-buffer-names)
      t)
     ((setq tmp (assoc buffer-name special-display-buffer-names))
      (cdr tmp))
     ((catch 'found
        (dolist (regexp special-display-regexps)
          (cond
           ((stringp regexp)
            (when (string-match-p regexp buffer-name)
              (throw 'found t)))
           ((and (consp regexp) (stringp (car regexp))
                 (string-match-p (car regexp) buffer-name))
            (throw 'found (cdr regexp))))))))))

(defcustom special-display-frame-alist
  '((height . 14) (width . 80) (unsplittable . t))
  "Alist of parameters for special frames.
Special frames are used for buffers whose names are listed in
`special-display-buffer-names' and for buffers whose names match
one of the regular expressions in `special-display-regexps'.

This variable can be set in your init file, like this:

  (setq special-display-frame-alist '((width . 80) (height . 20)))

These supersede the values given in `default-frame-alist'."
  :type '(repeat (cons :format "%v"
                         (symbol :tag "Parameter")
                         (sexp :tag "Value")))
  :group 'frames)
(make-obsolete-variable 'special-display-frame-alist 'display-buffer-alist "24.3")

(defun special-display-popup-frame (buffer &optional args)
  "Pop up a frame displaying BUFFER and return its window.
If BUFFER is already displayed in a visible or iconified frame,
raise that frame.  Otherwise, display BUFFER in a new frame.

Optional argument ARGS is a list specifying additional
information.

If ARGS is an alist, use it as a list of frame parameters.  If
these parameters contain (same-window . t), display BUFFER in
the selected window.  If they contain (same-frame . t), display
BUFFER in a window of the selected frame.

If ARGS is a list whose car is a symbol, use (car ARGS) as a
function to do the work.  Pass it BUFFER as first argument,
and (cdr ARGS) as second."
  (if (and args (symbolp (car args)))
      (apply (car args) buffer (cdr args))
    (let ((window (get-buffer-window buffer 0)))
      (or
       ;; If we have a window already, make it visible.
       (when window
         (let ((frame (window-frame window)))
           (make-frame-visible frame)
           (raise-frame frame)
           (display-buffer-record-window 'reuse window buffer)
           window))
       ;; Reuse the current window if the user requested it.
       (when (cdr (assq 'same-window args))
         (condition-case nil
             (progn (switch-to-buffer buffer nil t) (selected-window))
           (error nil)))
       ;; Stay on the same frame if requested.
       (when (or (cdr (assq 'same-frame args)) (cdr (assq 'same-window args)))
         (let* ((pop-up-windows t)
                pop-up-frames
                special-display-buffer-names special-display-regexps)
           (display-buffer buffer)))
       ;; If no window yet, make one in a new frame.
       (let* ((frame
               (with-current-buffer buffer
                 (make-frame (append args special-display-frame-alist))))
              (window (frame-selected-window frame)))
         (display-buffer-record-window 'frame window buffer)
         (unless (eq buffer (window-buffer window))
           (set-window-buffer window buffer)
           (set-window-prev-buffers window nil))
         (set-window-dedicated-p window t)
         window)))))

(defcustom special-display-function 'special-display-popup-frame
  "Function to call for displaying special buffers.
This function is called with two arguments - the buffer and,
optionally, a list - and should return a window displaying that
buffer.  The default value usually makes a separate frame for the
buffer using `special-display-frame-alist' to specify the frame
parameters.  See the definition of `special-display-popup-frame'
for how to specify such a function.

A buffer is special when its name is either listed in
`special-display-buffer-names' or matches a regexp in
`special-display-regexps'.

The specified function should call `display-buffer-record-window'
with corresponding arguments to set up the quit-restore parameter
of the window used."
  :type 'function
  :group 'frames)
(make-obsolete-variable 'special-display-function 'display-buffer-alist "24.3")

(defcustom same-window-buffer-names nil
  "List of names of buffers that should appear in the \"same\" window.
`display-buffer' and `pop-to-buffer' show a buffer whose name is
on this list in the selected rather than some other window.

An element of this list can be a cons cell instead of just a
string.  In that case, the cell's car must be a string specifying
the buffer name.  This is for compatibility with
`special-display-buffer-names'; the cdr of the cons cell is
ignored.

See also `same-window-regexps'."
 :type '(repeat (string :format "%v"))
 :group 'windows)

(defcustom same-window-regexps nil
  "List of regexps saying which buffers should appear in the \"same\" window.
`display-buffer' and `pop-to-buffer' show a buffer whose name
matches a regexp on this list in the selected rather than some
other window.

An element of this list can be a cons cell instead of just a
string.  In that case, the cell's car must be a regexp matching
the buffer name.  This is for compatibility with
`special-display-regexps'; the cdr of the cons cell is ignored.

See also `same-window-buffer-names'."
  :type '(repeat (regexp :format "%v"))
  :group 'windows)

(defun same-window-p (buffer-name)
  "Return non-nil if a buffer named BUFFER-NAME would be shown in the \"same\" window.
This function returns non-nil if `display-buffer' or
`pop-to-buffer' would show a buffer named BUFFER-NAME in the
selected rather than (as usual) some other window.  See
`same-window-buffer-names' and `same-window-regexps'."
  (cond
   ((not (stringp buffer-name)))
   ;; The elements of `same-window-buffer-names' can be buffer
   ;; names or cons cells whose cars are buffer names.
   ((member buffer-name same-window-buffer-names))
   ((assoc buffer-name same-window-buffer-names))
   ((catch 'found
      (dolist (regexp same-window-regexps)
        ;; The elements of `same-window-regexps' can be regexps
        ;; or cons cells whose cars are regexps.
        (when (or (and (stringp regexp)
                       (string-match-p regexp buffer-name))
                  (and (consp regexp) (stringp (car regexp))
                       (string-match-p (car regexp) buffer-name)))
          (throw 'found t)))))))

(defcustom pop-up-frames nil
  "Whether `display-buffer' should make a separate frame.
If nil, never make a separate frame.
If the value is `graphic-only', make a separate frame
on graphic displays only.
Any other non-nil value means always make a separate frame."
  :type '(choice
          (const :tag "Never" nil)
          (const :tag "On graphic displays only" graphic-only)
          (const :tag "Always" t))
  :group 'windows)

(defcustom display-buffer-reuse-frames nil
  "Non-nil means `display-buffer' should reuse frames.
If the buffer in question is already displayed in a frame, raise
that frame."
  :type 'boolean
  :version "21.1"
  :group 'windows)

(make-obsolete-variable
 'display-buffer-reuse-frames
 "use a `reusable-frames' alist entry in `display-buffer-alist'."
 "24.3")

(defcustom pop-up-windows t
  "Non-nil means `display-buffer' should make a new window."
  :type 'boolean
  :group 'windows)

(defcustom split-window-preferred-function 'split-window-sensibly
  "Function called by `display-buffer' routines to split a window.
This function is called with a window as single argument and is
supposed to split that window and return the new window.  If the
window can (or shall) not be split, it is supposed to return nil.
The default is to call the function `split-window-sensibly' which
tries to split the window in a way which seems most suitable.
You can customize the options `split-height-threshold' and/or
`split-width-threshold' in order to have `split-window-sensibly'
prefer either vertical or horizontal splitting.

If you set this to any other function, bear in mind that the
`display-buffer' routines may call this function two times.  The
argument of the first call is the largest window on its frame.
If that call fails to return a live window, the function is
called again with the least recently used window as argument.  If
that call fails too, `display-buffer' will use an existing window
to display its buffer.

The window selected at the time `display-buffer' was invoked is
still selected when this function is called.  Hence you can
compare the window argument with the value of `selected-window'
if you intend to split the selected window instead or if you do
not want to split the selected window."
  :type 'function
  :version "23.1"
  :group 'windows)

(defcustom split-height-threshold 80
  "Minimum height for splitting windows sensibly.
If this is an integer, `split-window-sensibly' may split a window
vertically only if it has at least this many lines.  If this is
nil, `split-window-sensibly' is not allowed to split a window
vertically.  If, however, a window is the only window on its
frame, `split-window-sensibly' may split it vertically
disregarding the value of this variable."
  :type '(choice (const nil) (integer :tag "lines"))
  :version "23.1"
  :group 'windows)

(defcustom split-width-threshold 160
  "Minimum width for splitting windows sensibly.
If this is an integer, `split-window-sensibly' may split a window
horizontally only if it has at least this many columns.  If this
is nil, `split-window-sensibly' is not allowed to split a window
horizontally."
  :type '(choice (const nil) (integer :tag "columns"))
  :version "23.1"
  :group 'windows)

(defun window-splittable-p (window &optional horizontal)
  "Return non-nil if `split-window-sensibly' may split WINDOW.
Optional argument HORIZONTAL nil or omitted means check whether
`split-window-sensibly' may split WINDOW vertically.  HORIZONTAL
non-nil means check whether WINDOW may be split horizontally.

WINDOW may be split vertically when the following conditions
hold:
- `window-size-fixed' is either nil or equals `width' for the
  buffer of WINDOW.
- `split-height-threshold' is an integer and WINDOW is at least as
  high as `split-height-threshold'.
- When WINDOW is split evenly, the emanating windows are at least
  `window-min-height' lines tall and can accommodate at least one
  line plus - if WINDOW has one - a mode line.

WINDOW may be split horizontally when the following conditions
hold:
- `window-size-fixed' is either nil or equals `height' for the
  buffer of WINDOW.
- `split-width-threshold' is an integer and WINDOW is at least as
  wide as `split-width-threshold'.
- When WINDOW is split evenly, the emanating windows are at least
  `window-min-width' or two (whichever is larger) columns wide."
  (when (window-live-p window)
    (with-current-buffer (window-buffer window)
      (if horizontal
          ;; A window can be split horizontally when its width is not
          ;; fixed, it is at least `split-width-threshold' columns wide
          ;; and at least twice as wide as `window-min-width' and 2 (the
          ;; latter value is hardcoded).
          (and (memq window-size-fixed '(nil height))
               ;; Testing `window-full-width-p' here hardly makes any
               ;; sense nowadays.  This can be done more intuitively by
               ;; setting up `split-width-threshold' appropriately.
               (numberp split-width-threshold)
               (>= (window-width window)
                   (max split-width-threshold
                        (* 2 (max window-min-width 2)))))
        ;; A window can be split vertically when its height is not
        ;; fixed, it is at least `split-height-threshold' lines high,
        ;; and it is at least twice as high as `window-min-height' and 2
        ;; if it has a mode line or 1.
        (and (memq window-size-fixed '(nil width))
             (numberp split-height-threshold)
             (>= (window-height window)
                 (max split-height-threshold
                      (* 2 (max window-min-height
                                (if mode-line-format 2 1))))))))))

(defun split-window-sensibly (&optional window)
  "Split WINDOW in a way suitable for `display-buffer'.
WINDOW defaults to the currently selected window.
If `split-height-threshold' specifies an integer, WINDOW is at
least `split-height-threshold' lines tall and can be split
vertically, split WINDOW into two windows one above the other and
return the lower window.  Otherwise, if `split-width-threshold'
specifies an integer, WINDOW is at least `split-width-threshold'
columns wide and can be split horizontally, split WINDOW into two
windows side by side and return the window on the right.  If this
can't be done either and WINDOW is the only window on its frame,
try to split WINDOW vertically disregarding any value specified
by `split-height-threshold'.  If that succeeds, return the lower
window.  Return nil otherwise.

By default `display-buffer' routines call this function to split
the largest or least recently used window.  To change the default
customize the option `split-window-preferred-function'.

You can enforce this function to not split WINDOW horizontally,
by setting (or binding) the variable `split-width-threshold' to
nil.  If, in addition, you set `split-height-threshold' to zero,
chances increase that this function does split WINDOW vertically.

In order to not split WINDOW vertically, set (or bind) the
variable `split-height-threshold' to nil.  Additionally, you can
set `split-width-threshold' to zero to make a horizontal split
more likely to occur.

Have a look at the function `window-splittable-p' if you want to
know how `split-window-sensibly' determines whether WINDOW can be
split."
  (let ((window (or window (selected-window))))
    (or (and (window-splittable-p window)
             ;; Split window vertically.
             (with-selected-window window
               (split-window-below)))
        (and (window-splittable-p window t)
             ;; Split window horizontally.
             (with-selected-window window
               (split-window-right)))
        (and (eq window (frame-root-window (window-frame window)))
             (not (window-minibuffer-p window))
             ;; If WINDOW is the only window on its frame and is not the
             ;; minibuffer window, try to split it vertically disregarding
             ;; the value of `split-height-threshold'.
             (let ((split-height-threshold 0))
               (when (window-splittable-p window)
                 (with-selected-window window
                   (split-window-below))))))))

(defun window--try-to-split-window (window)
  "Try to split WINDOW.
Return value returned by `split-window-preferred-function' if it
represents a live window, nil otherwise."
      (and (window-live-p window)
           (not (frame-parameter (window-frame window) 'unsplittable))
           (let ((new-window
                  ;; Since `split-window-preferred-function' might
                  ;; throw an error use `condition-case'.
                  (condition-case nil
                      (funcall split-window-preferred-function window)
                    (error nil))))
             (and (window-live-p new-window) new-window))))

(defun window--frame-usable-p (frame)
  "Return FRAME if it can be used to display a buffer."
  (when (frame-live-p frame)
    (let ((window (frame-root-window frame)))
      ;; `frame-root-window' may be an internal window which is considered
      ;; "dead" by `window-live-p'.  Hence if `window' is not live we
      ;; implicitly know that `frame' has a visible window we can use.
      (unless (and (window-live-p window)
                   (or (window-minibuffer-p window)
                       ;; If the window is soft-dedicated, the frame is usable.
                       ;; Actually, even if the window is really dedicated,
                       ;; the frame is still usable by splitting it.
                       ;; At least Emacs-22 allowed it, and it is desirable
                       ;; when displaying same-frame windows.
                       nil ; (eq t (window-dedicated-p window))
                       ))
        frame))))

(defcustom even-window-heights t
  "If non-nil `display-buffer' will try to even window heights.
Otherwise `display-buffer' will leave the window configuration
alone.  Heights are evened only when `display-buffer' chooses a
window that appears above or below the selected window."
  :type 'boolean
  :group 'windows)

(defun window--even-window-heights (window)
  "Even heights of WINDOW and selected window.
Do this only if these windows are vertically adjacent to each
other, `even-window-heights' is non-nil, and the selected window
is higher than WINDOW."
  (when (and even-window-heights
             ;; Even iff WINDOW forms a vertical combination with the
             ;; selected window, and WINDOW's height exceeds that of the
             ;; selected window, see also bug#11880.
             (window-combined-p window)
             (= (window-child-count (window-parent window)) 2)
             (eq (window-parent) (window-parent window))
             (> (window-total-height) (window-total-height window)))
    ;; Don't throw an error if we can't even window heights for
    ;; whatever reason.
    (condition-case nil
        (enlarge-window
         (/ (- (window-total-height window) (window-total-height)) 2))
      (error nil))))

(defun window--display-buffer (buffer window type &optional dedicated)
  "Display BUFFER in WINDOW and make its frame visible.
TYPE must be one of the symbols `reuse', `window' or `frame' and
is passed unaltered to `display-buffer-record-window'. Set
`window-dedicated-p' to DEDICATED if non-nil.  Return WINDOW if
BUFFER and WINDOW are live."
  (when (and (buffer-live-p buffer) (window-live-p window))
    (display-buffer-record-window type window buffer)
    (unless (eq buffer (window-buffer window))
      (set-window-dedicated-p window nil)
      (set-window-buffer window buffer)
      (when dedicated
        (set-window-dedicated-p window dedicated))
      (when (memq type '(window frame))
        (set-window-prev-buffers window nil)))
    window))

(defun window--maybe-raise-frame (frame)
  (let ((visible (frame-visible-p frame)))
    (unless (or (not visible)
                ;; Assume the selected frame is already visible enough.
                (eq frame (selected-frame))
                ;; Assume the frame from which we invoked the
                ;; minibuffer is visible.
                (and (minibuffer-window-active-p (selected-window))
                     (eq frame (window-frame (minibuffer-selected-window)))))
      (raise-frame frame))))

;; FIXME: Not implemented.
;; FIXME: By the way, there could be more levels of dedication:
;; - `barely' dedicated doesn't prevent reuse of the window, only records that
;;   the window hasn't been used for something else yet.
;; - `softly' dedicated only allows reuse when asked explicitly.
;; - `strongly' never allows reuse.
(defvar display-buffer-mark-dedicated nil
  "If non-nil, `display-buffer' marks the windows it creates as dedicated.
The actual non-nil value of this variable will be copied to the
`window-dedicated-p' flag.")

(defconst display-buffer--action-function-custom-type
  '(choice :tag "Function"
           (const :tag "--" ignore) ; default for insertion
           (const display-buffer-reuse-window)
           (const display-buffer-pop-up-window)
           (const display-buffer-same-window)
           (const display-buffer-pop-up-frame)
           (const display-buffer-use-some-window)
           (function :tag "Other function"))
  "Custom type for `display-buffer' action functions.")

(defconst display-buffer--action-custom-type
  `(cons :tag "Action"
         (choice :tag "Action functions"
                 ,display-buffer--action-function-custom-type
                 (repeat
                  :tag "List of functions"
                  ,display-buffer--action-function-custom-type))
         (alist :tag "Action arguments"
                :key-type symbol
                :value-type (sexp :tag "Value")))
  "Custom type for `display-buffer' actions.")

(defvar display-buffer-overriding-action '(nil . nil)
  "Overriding action to perform to display a buffer.
It should be a cons cell (FUNCTION . ALIST), where FUNCTION is a
function or a list of functions.  Each function should accept two
arguments: a buffer to display and an alist similar to ALIST.
See `display-buffer' for details.")
(put 'display-buffer-overriding-action 'risky-local-variable t)

(defcustom display-buffer-alist nil
  "Alist of conditional actions for `display-buffer'.
This is a list of elements (CONDITION . ACTION), where:

 CONDITION is either a regexp matching buffer names, or a function
  that takes a buffer and returns a boolean.

 ACTION is a cons cell (FUNCTION . ALIST), where FUNCTION is a
  function or a list of functions.  Each such function should
  accept two arguments: a buffer to display and an alist of the
  same form as ALIST.  See `display-buffer' for details."
  :type `(alist :key-type
                (choice :tag "Condition"
                        regexp
                        (function :tag "Matcher function"))
                :value-type ,display-buffer--action-custom-type)
  :risky t
  :version "24.1"
  :group 'windows)

(defcustom display-buffer-base-action '(nil . nil)
  "User-specified default action for `display-buffer'.
It should be a cons cell (FUNCTION . ALIST), where FUNCTION is a
function or a list of functions.  Each function should accept two
arguments: a buffer to display and an alist similar to ALIST.
See `display-buffer' for details."
  :type display-buffer--action-custom-type
  :risky t
  :version "24.1"
  :group 'windows)

(defconst display-buffer-fallback-action
  '((display-buffer--maybe-same-window  ;FIXME: why isn't this redundant?
     display-buffer-reuse-window
     display-buffer--maybe-pop-up-frame-or-window
     display-buffer-use-some-window
     ;; If all else fails, pop up a new frame.
     display-buffer-pop-up-frame))
  "Default fallback action for `display-buffer'.
This is the action used by `display-buffer' if no other actions
specified, e.g. by the user options `display-buffer-alist' or
`display-buffer-base-action'.  See `display-buffer'.")
(put 'display-buffer-fallback-action 'risky-local-variable t)

(defun display-buffer-assq-regexp (buffer-name alist)
  "Retrieve ALIST entry corresponding to BUFFER-NAME."
  (catch 'match
    (dolist (entry alist)
      (let ((key (car entry)))
        (when (or (and (stringp key)
                       (string-match-p key buffer-name))
                  (and (symbolp key) (functionp key)
                       (funcall key buffer-name alist)))
          (throw 'match (cdr entry)))))))

(defvar display-buffer--same-window-action
  '(display-buffer-same-window
    (inhibit-same-window . nil))
  "A `display-buffer' action for displaying in the same window.")
(put 'display-buffer--same-window-action 'risky-local-variable t)

(defvar display-buffer--other-frame-action
  '((display-buffer-reuse-window
     display-buffer-pop-up-frame)
    (reusable-frames . 0)
    (inhibit-same-window . t))
  "A `display-buffer' action for displaying in another frame.")
(put 'display-buffer--other-frame-action 'risky-local-variable t)

(defun display-buffer (buffer-or-name &optional action frame)
  "Display BUFFER-OR-NAME in some window, without selecting it.
BUFFER-OR-NAME must be a buffer or the name of an existing
buffer.  Return the window chosen for displaying BUFFER-OR-NAME,
or nil if no such window is found.

Optional argument ACTION should have the form (FUNCTION . ALIST).
FUNCTION is either a function or a list of functions.
ALIST is an arbitrary association list (alist).

Each such FUNCTION should accept two arguments: the buffer to
display and an alist.  Based on those arguments, it should either
display the buffer and return the window, or return nil if unable
to display the buffer.

The `display-buffer' function builds a function list and an alist
by combining the functions and alists specified in
`display-buffer-overriding-action', `display-buffer-alist', the
ACTION argument, `display-buffer-base-action', and
`display-buffer-fallback-action' (in order).  Then it calls each
function in the combined function list in turn, passing the
buffer as the first argument and the combined alist as the second
argument, until one of the functions returns non-nil.

Available action functions include:
 `display-buffer-same-window'
 `display-buffer-reuse-window'
 `display-buffer-pop-up-frame'
 `display-buffer-pop-up-window'
 `display-buffer-use-some-window'

Recognized alist entries include:

 `inhibit-same-window' -- A non-nil value prevents the same
                          window from being used for display.

 `inhibit-switch-frame' -- A non-nil value prevents any other
                           frame from being raised or selected,
                           even if the window is displayed there.

 `reusable-frames' -- Value specifies frame(s) to search for a
                      window that already displays the buffer.
                      See `display-buffer-reuse-window'.

 `pop-up-frame-parameters' -- Value specifies an alist of frame
                              parameters to give a new frame, if
                              one is created.

The ACTION argument to `display-buffer' can also have a non-nil
and non-list value.  This means to display the buffer in a window
other than the selected one, even if it is already displayed in
the selected window.  If called interactively with a prefix
argument, ACTION is t.

Optional argument FRAME, if non-nil, acts like an additional
ALIST entry (reusable-frames . FRAME), specifying the frame(s) to
search for a window that is already displaying the buffer.  See
`display-buffer-reuse-window'."
  (interactive (list (read-buffer "Display buffer: " (other-buffer))
                     (if current-prefix-arg t)))
  (let ((buffer (if (bufferp buffer-or-name)
                    buffer-or-name
                  (get-buffer buffer-or-name)))
        ;; Handle the old form of the first argument.
        (inhibit-same-window (and action (not (listp action)))))
    (unless (listp action) (setq action nil))
    (if display-buffer-function
        ;; If `display-buffer-function' is defined, let it do the job.
        (funcall display-buffer-function buffer inhibit-same-window)
      ;; Otherwise, use the defined actions.
      (let* ((user-action
              (display-buffer-assq-regexp (buffer-name buffer)
                                          display-buffer-alist))
             (special-action (display-buffer--special-action buffer))
             ;; Extra actions from the arguments to this function:
             (extra-action
              (cons nil (append (if inhibit-same-window
                                    '((inhibit-same-window . t)))
                                (if frame
                                    `((reusable-frames . ,frame))))))
             ;; Construct action function list and action alist.
             (actions (list display-buffer-overriding-action
                            user-action special-action action extra-action
                            display-buffer-base-action
                            display-buffer-fallback-action))
             (functions (apply 'append
                               (mapcar (lambda (x)
                                         (setq x (car x))
                                         (if (functionp x) (list x) x))
                                       actions)))
             (alist (apply 'append (mapcar 'cdr actions)))
             window)
        (unless (buffer-live-p buffer)
          (error "Invalid buffer"))
        (while (and functions (not window))
          (setq window (funcall (car functions) buffer alist)
                functions (cdr functions)))
        window))))

(defun display-buffer-other-frame (buffer)
  "Display buffer BUFFER in another frame.
This uses the function `display-buffer' as a subroutine; see
its documentation for additional customization information."
  (interactive "BDisplay buffer in other frame: ")
  (display-buffer buffer display-buffer--other-frame-action t))

;;; `display-buffer' action functions:

(defun display-buffer-same-window (buffer alist)
  "Display BUFFER in the selected window.
This fails if ALIST has a non-nil `inhibit-same-window' entry, or
if the selected window is a minibuffer window or is dedicated to
another buffer; in that case, return nil.  Otherwise, return the
selected window."
  (unless (or (cdr (assq 'inhibit-same-window alist))
              (window-minibuffer-p)
              (window-dedicated-p))
    (window--display-buffer buffer (selected-window) 'reuse)))

(defun display-buffer--maybe-same-window (buffer alist)
  "Conditionally display BUFFER in the selected window.
If `same-window-p' returns non-nil for BUFFER's name, call
`display-buffer-same-window' and return its value.  Otherwise,
return nil."
  (and (same-window-p (buffer-name buffer))
       (display-buffer-same-window buffer alist)))

(defun display-buffer-reuse-window (buffer alist)
  "Return a window that is already displaying BUFFER.
Return nil if no usable window is found.

If ALIST has a non-nil `inhibit-same-window' entry, the selected
window is not eligible for reuse.

If ALIST contains a `reusable-frames' entry, its value determines
which frames to search for a reusable window:
  nil -- the selected frame (actually the last non-minibuffer frame)
  A frame   -- just that frame
  `visible' -- all visible frames
  0   -- all frames on the current terminal
  t   -- all frames.

If ALIST contains no `reusable-frames' entry, search just the
selected frame if `display-buffer-reuse-frames' and
`pop-up-frames' are both nil; search all frames on the current
terminal if either of those variables is non-nil.

If ALIST has a non-nil `inhibit-switch-frame' entry, then in the
event that a window on another frame is chosen, avoid raising
that frame."
  (let* ((alist-entry (assq 'reusable-frames alist))
         (frames (cond (alist-entry (cdr alist-entry))
                       ((if (eq pop-up-frames 'graphic-only)
                            (display-graphic-p)
                          pop-up-frames)
                        0)
                       (display-buffer-reuse-frames 0)
                       (t (last-nonminibuffer-frame))))
         (window (if (and (eq buffer (window-buffer))
                          (not (cdr (assq 'inhibit-same-window alist))))
                     (selected-window)
                   (car (delq (selected-window)
                              (get-buffer-window-list buffer 'nomini
                                                      frames))))))
    (when (window-live-p window)
      (prog1 (window--display-buffer buffer window 'reuse)
        (unless (cdr (assq 'inhibit-switch-frame alist))
          (window--maybe-raise-frame (window-frame window)))))))

(defun display-buffer--special-action (buffer)
  "Return special display action for BUFFER, if any.
If `special-display-p' returns non-nil for BUFFER, return an
appropriate display action involving `special-display-function'.
See `display-buffer' for the format of display actions."
  (and special-display-function
       ;; `special-display-p' returns either t or a list of frame
       ;; parameters to pass to `special-display-function'.
       (let ((pars (special-display-p (buffer-name buffer))))
         (when pars
           (list (list #'display-buffer-reuse-window
                       `(lambda (buffer _alist)
                          (funcall special-display-function
                                   buffer ',(if (listp pars) pars)))))))))

(defun display-buffer-pop-up-frame (buffer alist)
  "Display BUFFER in a new frame.
This works by calling `pop-up-frame-function'.  If successful,
return the window used; otherwise return nil.

If ALIST has a non-nil `inhibit-switch-frame' entry, avoid
raising the new frame.

If ALIST has a non-nil `pop-up-frame-parameters' entry, the
corresponding value is an alist of frame parameters to give the
new frame."
  (let* ((params (cdr (assq 'pop-up-frame-parameters alist)))
         (pop-up-frame-alist (append params pop-up-frame-alist))
         (fun pop-up-frame-function)
         frame window)
    (when (and fun
               (setq frame (funcall fun))
               (setq window (frame-selected-window frame)))
      (prog1 (window--display-buffer buffer window
                                     'frame display-buffer-mark-dedicated)
        (unless (cdr (assq 'inhibit-switch-frame alist))
          (window--maybe-raise-frame frame))))))

(defun display-buffer-pop-up-window (buffer alist)
  "Display BUFFER by popping up a new window.
The new window is created on the selected frame, or in
`last-nonminibuffer-frame' if no windows can be created there.
If successful, return the new window; otherwise return nil.

If ALIST has a non-nil `inhibit-switch-frame' entry, then in the
event that the new window is created on another frame, avoid
raising the frame."
  (let ((frame (or (window--frame-usable-p (selected-frame))
                   (window--frame-usable-p (last-nonminibuffer-frame))))
        window)
    (when (and (or (not (frame-parameter frame 'unsplittable))
                   ;; If the selected frame cannot be split, look at
                   ;; `last-nonminibuffer-frame'.
                   (and (eq frame (selected-frame))
                        (setq frame (last-nonminibuffer-frame))
                        (window--frame-usable-p frame)
                        (not (frame-parameter frame 'unsplittable))))
               ;; Attempt to split largest or least recently used window.
               (setq window (or (window--try-to-split-window
                                 (get-largest-window frame t))
                                (window--try-to-split-window
                                 (get-lru-window frame t)))))
      (prog1 (window--display-buffer buffer window
                                     'window display-buffer-mark-dedicated)
        (unless (cdr (assq 'inhibit-switch-frame alist))
          (window--maybe-raise-frame (window-frame window)))))))

(defun display-buffer--maybe-pop-up-frame-or-window (buffer alist)
  "Try displaying BUFFER based on `pop-up-frames' or `pop-up-windows'.

If `pop-up-frames' is non-nil (and not `graphic-only' on a
text-only terminal), try with `display-buffer-pop-up-frame'.

If that cannot be done, and `pop-up-windows' is non-nil, try
again with `display-buffer-pop-up-window'."
  (or (and (if (eq pop-up-frames 'graphic-only)
               (display-graphic-p)
             pop-up-frames)
           (display-buffer-pop-up-frame buffer alist))
      (and pop-up-windows
           (display-buffer-pop-up-window buffer alist))))

(defun display-buffer-below-selected (buffer _alist)
  "Try displaying BUFFER in a window below the selected window.
This either splits the selected window or reuses the window below
the selected one."
  (let (window)
    (or (and (not (frame-parameter nil 'unsplittable))
             (setq window (window--try-to-split-window (selected-window)))
             (window--display-buffer
              buffer window 'window display-buffer-mark-dedicated))
        (and (setq window (window-in-direction 'below))
             (not (window-dedicated-p window))
             (window--display-buffer
              buffer window 'reuse display-buffer-mark-dedicated)))))

(defun display-buffer-use-some-window (buffer alist)
  "Display BUFFER in an existing window.
Search for a usable window, set that window to the buffer, and
return the window.  If no suitable window is found, return nil.

If ALIST has a non-nil `inhibit-switch-frame' entry, then in the
event that a window in another frame is chosen, avoid raising
that frame."
  (let* ((not-this-window (cdr (assq 'inhibit-same-window alist)))
         (frame (or (window--frame-usable-p (selected-frame))
                    (window--frame-usable-p (last-nonminibuffer-frame))))
         (window
          ;; Reuse an existing window.
          (or (get-lru-window frame nil not-this-window)
              (let ((window (get-buffer-window buffer 'visible)))
                (unless (and not-this-window
                             (eq window (selected-window)))
                  window))
              (get-largest-window 'visible nil not-this-window)
              (let ((window (get-buffer-window buffer 0)))
                (unless (and not-this-window
                             (eq window (selected-window)))
                  window))
              (get-largest-window 0 not-this-window))))
    (when (window-live-p window)
      (prog1
          (window--display-buffer buffer window 'reuse)
        (window--even-window-heights window)
        (unless (cdr (assq 'inhibit-switch-frame alist))
          (window--maybe-raise-frame (window-frame window)))))))

;;; Display + selection commands:
(defun pop-to-buffer (buffer &optional action norecord)
  "Select buffer BUFFER in some window, preferably a different one.
BUFFER may be a buffer, a string (a buffer name), or nil.  If it
is a string not naming an existent buffer, create a buffer with
that name.  If BUFFER is nil, choose some other buffer.  Return
the buffer.

This uses `display-buffer' as a subroutine.  The optional ACTION
argument is passed to `display-buffer' as its ACTION argument.
See `display-buffer' for more information.  ACTION is t if called
interactively with a prefix argument, which means to pop to a
window other than the selected one even if the buffer is already
displayed in the selected window.

If the window to show BUFFER is not on the selected
frame, raise that window's frame and give it input focus.

Optional third arg NORECORD non-nil means do not put this buffer
at the front of the list of recently selected ones."
  (interactive (list (read-buffer "Pop to buffer: " (other-buffer))
                     (if current-prefix-arg t)))
  (setq buffer (window-normalize-buffer-to-switch-to buffer))
  (set-buffer buffer)
  (let* ((old-frame (selected-frame))
         (window (display-buffer buffer action))
         (frame (window-frame window)))
    ;; If we chose another frame, make sure it gets input focus.
    (unless (eq frame old-frame)
      (select-frame-set-input-focus frame norecord))
    ;; Make sure new window is selected (Bug#8615), (Bug#6954).
    (select-window window norecord)
    buffer))

(defun pop-to-buffer-same-window (buffer &optional norecord)
  "Select buffer BUFFER in some window, preferably the same one.
This function behaves much like `switch-to-buffer', except it
displays with `special-display-function' if BUFFER has a match in
`special-display-buffer-names' or `special-display-regexps'.

Unlike `pop-to-buffer', this function prefers using the selected
window over popping up a new window or frame.

BUFFER may be a buffer, a string (a buffer name), or nil.  If it
is a string not naming an existent buffer, create a buffer with
that name.  If BUFFER is nil, choose some other buffer.  Return
the buffer.

NORECORD, if non-nil means do not put this buffer at the front of
the list of recently selected ones."
  (pop-to-buffer buffer display-buffer--same-window-action norecord))

(defun read-buffer-to-switch (prompt)
  "Read the name of a buffer to switch to, prompting with PROMPT.
Return the name of the buffer as a string.

This function is intended for the `switch-to-buffer' family of
commands since these need to omit the name of the current buffer
from the list of completions and default values."
  (let ((rbts-completion-table (internal-complete-buffer-except)))
    (minibuffer-with-setup-hook
        (lambda ()
          (setq minibuffer-completion-table rbts-completion-table)
          ;; Since rbts-completion-table is built dynamically, we
          ;; can't just add it to the default value of
          ;; icomplete-with-completion-tables, so we add it
          ;; here manually.
          (if (and (boundp 'icomplete-with-completion-tables)
                   (listp icomplete-with-completion-tables))
              (set (make-local-variable 'icomplete-with-completion-tables)
                   (cons rbts-completion-table
                         icomplete-with-completion-tables))))
      (read-buffer prompt (other-buffer (current-buffer))
                   (confirm-nonexistent-file-or-buffer)))))

(defun window-normalize-buffer-to-switch-to (buffer-or-name)
  "Normalize BUFFER-OR-NAME argument of buffer switching functions.
If BUFFER-OR-NAME is nil, return the buffer returned by
`other-buffer'.  Else, if a buffer specified by BUFFER-OR-NAME
exists, return that buffer.  If no such buffer exists, create a
buffer with the name BUFFER-OR-NAME and return that buffer."
  (if buffer-or-name
      (or (get-buffer buffer-or-name)
          (let ((buffer (get-buffer-create buffer-or-name)))
            (set-buffer-major-mode buffer)
            buffer))
    (other-buffer)))

(defun switch-to-buffer (buffer-or-name &optional norecord force-same-window)
  "Switch to buffer BUFFER-OR-NAME in the selected window.
If called interactively, prompt for the buffer name using the
minibuffer.  The variable `confirm-nonexistent-file-or-buffer'
determines whether to request confirmation before creating a new
buffer.

BUFFER-OR-NAME may be a buffer, a string (a buffer name), or
nil.  If BUFFER-OR-NAME is a string that does not identify an
existing buffer, create a buffer with that name.  If
BUFFER-OR-NAME is nil, switch to the buffer returned by
`other-buffer'.

Optional argument NORECORD non-nil means do not put the buffer
specified by BUFFER-OR-NAME at the front of the buffer list and
do not make the window displaying it the most recently selected
one.

If FORCE-SAME-WINDOW is non-nil, BUFFER-OR-NAME must be displayed
in the selected window; signal an error if that is
impossible (e.g. if the selected window is minibuffer-only).  If
nil, BUFFER-OR-NAME may be displayed in another window.

Return the buffer switched to."
  (interactive
   (list (read-buffer-to-switch "Switch to buffer: ") nil 'force-same-window))
  (let ((buffer (window-normalize-buffer-to-switch-to buffer-or-name)))
    (cond
     ;; Don't call set-window-buffer if it's not needed since it
     ;; might signal an error (e.g. if the window is dedicated).
     ((eq buffer (window-buffer)))
     ((window-minibuffer-p)
      (if force-same-window
          (user-error "Cannot switch buffers in minibuffer window")
        (pop-to-buffer buffer norecord)))
     ((eq (window-dedicated-p) t)
      (if force-same-window
          (user-error "Cannot switch buffers in a dedicated window")
        (pop-to-buffer buffer norecord)))
     (t (set-window-buffer nil buffer)))

    (unless norecord
      (select-window (selected-window)))
    (set-buffer buffer)))

(defun switch-to-buffer-other-window (buffer-or-name &optional norecord)
  "Select the buffer specified by BUFFER-OR-NAME in another window.
BUFFER-OR-NAME may be a buffer, a string (a buffer name), or
nil.  Return the buffer switched to.

If called interactively, prompt for the buffer name using the
minibuffer.  The variable `confirm-nonexistent-file-or-buffer'
determines whether to request confirmation before creating a new
buffer.

If BUFFER-OR-NAME is a string and does not identify an existing
buffer, create a new buffer with that name.  If BUFFER-OR-NAME is
nil, switch to the buffer returned by `other-buffer'.

Optional second argument NORECORD non-nil means do not put this
buffer at the front of the list of recently selected ones.

This uses the function `display-buffer' as a subroutine; see its
documentation for additional customization information."
  (interactive
   (list (read-buffer-to-switch "Switch to buffer in other window: ")))
  (let ((pop-up-windows t))
    (pop-to-buffer buffer-or-name t norecord)))

(defun switch-to-buffer-other-frame (buffer-or-name &optional norecord)
  "Switch to buffer BUFFER-OR-NAME in another frame.
BUFFER-OR-NAME may be a buffer, a string (a buffer name), or
nil.  Return the buffer switched to.

If called interactively, prompt for the buffer name using the
minibuffer.  The variable `confirm-nonexistent-file-or-buffer'
determines whether to request confirmation before creating a new
buffer.

If BUFFER-OR-NAME is a string and does not identify an existing
buffer, create a new buffer with that name.  If BUFFER-OR-NAME is
nil, switch to the buffer returned by `other-buffer'.

Optional second arg NORECORD non-nil means do not put this
buffer at the front of the list of recently selected ones.

This uses the function `display-buffer' as a subroutine; see its
documentation for additional customization information."
  (interactive
   (list (read-buffer-to-switch "Switch to buffer in other frame: ")))
  (pop-to-buffer buffer-or-name display-buffer--other-frame-action norecord))
\f
(defun set-window-text-height (window height)
  "Set the height in lines of the text display area of WINDOW to HEIGHT.
WINDOW must be a live window and defaults to the selected one.
HEIGHT doesn't include the mode line or header line, if any, or
any partial-height lines in the text display area.

Note that the current implementation of this function cannot
always set the height exactly, but attempts to be conservative,
by allocating more lines than are actually needed in the case
where some error may be present."
  (setq window (window-normalize-window window t))
  (let ((delta (- height (window-text-height window))))
    (unless (zerop delta)
      ;; Setting window-min-height to a value like 1 can lead to very
      ;; bizarre displays because it also allows Emacs to make *other*
      ;; windows one line tall, which means that there's no more space
      ;; for the mode line.
      (let ((window-min-height (min 2 height)))
        (window-resize window delta)))))

(defun enlarge-window-horizontally (delta)
  "Make selected window DELTA columns wider.
Interactively, if no argument is given, make selected window one
column wider."
  (interactive "p")
  (enlarge-window delta t))

(defun shrink-window-horizontally (delta)
  "Make selected window DELTA columns narrower.
Interactively, if no argument is given, make selected window one
column narrower."
  (interactive "p")
  (shrink-window delta t))

(defun count-screen-lines (&optional beg end count-final-newline window)
  "Return the number of screen lines in the region.
The number of screen lines may be different from the number of actual lines,
due to line breaking, display table, etc.

Optional arguments BEG and END default to `point-min' and `point-max'
respectively.

If region ends with a newline, ignore it unless optional third argument
COUNT-FINAL-NEWLINE is non-nil.

The optional fourth argument WINDOW specifies the window used for obtaining
parameters such as width, horizontal scrolling, and so on.  The default is
to use the selected window's parameters.

Like `vertical-motion', `count-screen-lines' always uses the current buffer,
regardless of which buffer is displayed in WINDOW.  This makes possible to use
`count-screen-lines' in any buffer, whether or not it is currently displayed
in some window."
  (unless beg
    (setq beg (point-min)))
  (unless end
    (setq end (point-max)))
  (if (= beg end)
      0
    (save-excursion
      (save-restriction
        (widen)
        (narrow-to-region (min beg end)
                          (if (and (not count-final-newline)
                                   (= ?\n (char-before (max beg end))))
                              (1- (max beg end))
                            (max beg end)))
        (goto-char (point-min))
        (1+ (vertical-motion (buffer-size) window))))))

(defun window-buffer-height (window)
  "Return the height (in screen lines) of the buffer that WINDOW is displaying.
WINDOW must be a live window and defaults to the selected one."
  (setq window (window-normalize-window window t))
  (with-current-buffer (window-buffer window)
    (max 1
         (count-screen-lines (point-min) (point-max)
                             ;; If buffer ends with a newline, ignore it when
                             ;; counting height unless point is after it.
                             (eobp)
                             window))))

;;; Resizing buffers to fit their contents exactly.
(defun fit-window-to-buffer (&optional window max-height min-height)
  "Adjust height of WINDOW to display its buffer's contents exactly.
WINDOW must be a live window and defaults to the selected one.

Optional argument MAX-HEIGHT specifies the maximum height of
WINDOW and defaults to the height of WINDOW's frame.  Optional
argument MIN-HEIGHT specifies the minimum height of WINDOW and
defaults to `window-min-height'.  Both MAX-HEIGHT and MIN-HEIGHT
are specified in lines and include the mode line and header line,
if any.

Return the number of lines by which WINDOW was enlarged or
shrunk.  If an error occurs during resizing, return nil but don't
signal an error.

Note that even if this function makes WINDOW large enough to show
_all_ lines of its buffer you might not see the first lines when
WINDOW was scrolled."
  (interactive)
  (setq window (window-normalize-window window t))
  ;; Can't resize a full height or fixed-size window.
  (unless (or (window-size-fixed-p window)
              (window-full-height-p window))
    (with-selected-window window
      (let* ((height (window-total-size))
             (min-height
              ;; Adjust MIN-HEIGHT.
              (if (numberp min-height)
                  ;; Can't get smaller than `window-safe-min-height'.
                  (max min-height window-safe-min-height)
                ;; Preserve header and mode line if present.
                (window-min-size nil nil t)))
             (max-height
              ;; Adjust MAX-HEIGHT.
              (if (numberp max-height)
                  ;; Can't get larger than height of frame.
                  (min max-height
                       (window-total-size (frame-root-window window)))
                ;, Don't delete other windows.
                (+ height (window-max-delta nil nil window))))
             ;; Make `desired-height' the height necessary to show
             ;; all of WINDOW's buffer, constrained by MIN-HEIGHT
             ;; and MAX-HEIGHT.
             (desired-height
              (max
               (min
                (+ (count-screen-lines)
                   ;; For non-minibuffers count the mode line, if any.
                   (if (and (not (window-minibuffer-p window))
                            mode-line-format)
                       1
                     0)
                   ;; Count the header line, if any.
                   (if header-line-format 1 0))
                max-height)
               min-height))
             (desired-delta
              (- desired-height (window-total-size window)))
             (delta
              (if (> desired-delta 0)
                  (min desired-delta
                       (window-max-delta window nil window))
                (max desired-delta
                     (- (window-min-delta window nil window))))))
        (condition-case nil
            (if (zerop delta)
                ;; Return zero if DELTA became zero in the process.
                0
              ;; Don't try to redisplay with the cursor at the end on its
              ;; own line--that would force a scroll and spoil things.
              (when (and (eobp) (bolp) (not (bobp)))
                ;; It's silly to put `point' at the end of the previous
                ;; line and so maybe force horizontal scrolling.
                (set-window-point window (line-beginning-position 0)))
              ;; Call `window-resize' with OVERRIDE argument equal WINDOW.
              (window-resize window delta nil window)
              ;; Check if the last line is surely fully visible.  If
              ;; not, enlarge the window.
              (let ((end (save-excursion
                           (goto-char (point-max))
                           (when (and (bolp) (not (bobp)))
                             ;; Don't include final newline.
                             (backward-char 1))
                           (when truncate-lines
                             ;; If line-wrapping is turned off, test the
                             ;; beginning of the last line for
                             ;; visibility instead of the end, as the
                             ;; end of the line could be invisible by
                             ;; virtue of extending past the edge of the
                             ;; window.
                             (forward-line 0))
                           (point))))
                (set-window-vscroll window 0)
                ;; This loop might in some rare pathological cases raise
                ;; an error - another reason for the `condition-case'.
                (while (and (< desired-height max-height)
                            (= desired-height (window-total-size))
                            (not (pos-visible-in-window-p end)))
                  (window-resize window 1 nil window)
                  (setq desired-height (1+ desired-height)))))
          (error (setq delta nil)))
        delta))))

(defcustom fit-frame-to-buffer-bottom-margin 4
  "Bottom margin for `fit-frame-to-buffer'.
This is the number of lines `fit-frame-to-buffer' leaves free at the
bottom of the display in order to not obscure the system task bar."
  :type 'integer
  :version "24.2"
  :group 'windows)

(defun fit-frame-to-buffer (&optional frame max-height min-height)
  "Adjust height of FRAME to display its buffer's contents exactly.
FRAME can be any live frame and defaults to the selected one.

Optional argument MAX-HEIGHT specifies the maximum height of
FRAME and defaults to the height of the display below the current
top line of FRAME minus FIT-FRAME-TO-BUFFER-BOTTOM-MARGIN.
Optional argument MIN-HEIGHT specifies the minimum height of
FRAME."
  (interactive)
  (setq frame (window-normalize-frame frame))
  (let* ((root (frame-root-window frame))
         (frame-min-height
          (+ (- (frame-height frame) (window-total-size root))
             window-min-height))
         (frame-top (frame-parameter frame 'top))
         (top (if (consp frame-top)
                  (funcall (car frame-top) (cadr frame-top))
                frame-top))
         (frame-max-height
          (- (/ (- (x-display-pixel-height frame) top)
                (frame-char-height frame))
             fit-frame-to-buffer-bottom-margin))
         (compensate 0)
         delta)
    (when (and (window-live-p root) (not (window-size-fixed-p root)))
      (with-selected-window root
        (cond
         ((not max-height)
          (setq max-height frame-max-height))
         ((numberp max-height)
          (setq max-height (min max-height frame-max-height)))
         (t
          (error "%s is an invalid maximum height" max-height)))
        (cond
         ((not min-height)
          (setq min-height frame-min-height))
         ((numberp min-height)
          (setq min-height (min min-height frame-min-height)))
         (t
          (error "%s is an invalid minimum height" min-height)))
        ;; When tool-bar-mode is enabled and we have just created a new
        ;; frame, reserve lines for toolbar resizing.  This is needed
        ;; because for reasons unknown to me Emacs (1) reserves one line
        ;; for the toolbar when making the initial frame and toolbars
        ;; are enabled, and (2) later adds the remaining lines needed.
        ;; Our code runs IN BETWEEN (1) and (2).  YMMV when you're on a
        ;; system that behaves differently.
        (let ((quit-restore (window-parameter root 'quit-restore))
              (lines (tool-bar-lines-needed frame)))
          (when (and quit-restore (eq (car quit-restore) 'frame)
                     (not (zerop lines)))
            (setq compensate (1- lines))))
        (message "%s" compensate)
        (setq delta
              ;; Always count a final newline - we don't do any
              ;; post-processing, so let's play safe.
              (+ (count-screen-lines nil nil t)
                 (- (window-body-size))
                 compensate)))
      ;; Move away from final newline.
      (when (and (eobp) (bolp) (not (bobp)))
        (set-window-point root (line-beginning-position 0)))
      (set-window-start root (point-min))
      (set-window-vscroll root 0)
      (condition-case nil
          (set-frame-height
           frame
           (min (max (+ (frame-height frame) delta)
                     min-height)
                max-height))
        (error (setq delta nil))))
    delta))

(defun window-safely-shrinkable-p (&optional window)
  "Return t if WINDOW can be shrunk without shrinking other windows.
WINDOW defaults to the selected window."
  (with-selected-window (or window (selected-window))
    (let ((edges (window-edges)))
      (or (= (nth 2 edges) (nth 2 (window-edges (previous-window))))
          (= (nth 0 edges) (nth 0 (window-edges (next-window))))))))

(defun shrink-window-if-larger-than-buffer (&optional window)
  "Shrink height of WINDOW if its buffer doesn't need so many lines.
More precisely, shrink WINDOW vertically to be as small as
possible, while still showing the full contents of its buffer.
WINDOW must be a live window and defaults to the selected one.

Do not shrink WINDOW to less than `window-min-height' lines.  Do
nothing if the buffer contains more lines than the present window
height, or if some of the window's contents are scrolled out of
view, or if shrinking this window would also shrink another
window, or if the window is the only window of its frame.

Return non-nil if the window was shrunk, nil otherwise."
  (interactive)
  (setq window (window-normalize-window window t))
  ;; Make sure that WINDOW is vertically combined and `point-min' is
  ;; visible (for whatever reason that's needed).  The remaining issues
  ;; should be taken care of by `fit-window-to-buffer'.
  (when (and (window-combined-p window)
             (pos-visible-in-window-p (point-min) window))
    (fit-window-to-buffer window (window-total-size window))))
\f
(defun kill-buffer-and-window ()
  "Kill the current buffer and delete the selected window."
  (interactive)
  (let ((window-to-delete (selected-window))
        (buffer-to-kill (current-buffer))
        (delete-window-hook (lambda () (ignore-errors (delete-window)))))
    (unwind-protect
        (progn
          (add-hook 'kill-buffer-hook delete-window-hook t t)
          (if (kill-buffer (current-buffer))
              ;; If `delete-window' failed before, we rerun it to regenerate
              ;; the error so it can be seen in the echo area.
              (when (eq (selected-window) window-to-delete)
                (delete-window))))
      ;; If the buffer is not dead for some reason (probably because
      ;; of a `quit' signal), remove the hook again.
      (ignore-errors
       (with-current-buffer buffer-to-kill
         (remove-hook 'kill-buffer-hook delete-window-hook t))))))

\f
(defvar recenter-last-op nil
  "Indicates the last recenter operation performed.
Possible values: `top', `middle', `bottom', integer or float numbers.")

(defcustom recenter-positions '(middle top bottom)
  "Cycling order for `recenter-top-bottom'.
A list of elements with possible values `top', `middle', `bottom',
integer or float numbers that define the cycling order for
the command `recenter-top-bottom'.

Top and bottom destinations are `scroll-margin' lines from the true
window top and bottom.  Middle redraws the frame and centers point
vertically within the window.  Integer number moves current line to
the specified absolute window-line.  Float number between 0.0 and 1.0
means the percentage of the screen space from the top.  The default
cycling order is middle -> top -> bottom."
  :type '(repeat (choice
                  (const :tag "Top" top)
                  (const :tag "Middle" middle)
                  (const :tag "Bottom" bottom)
                  (integer :tag "Line number")
                  (float :tag "Percentage")))
  :version "23.2"
  :group 'windows)

(defun recenter-top-bottom (&optional arg)
  "Move current buffer line to the specified window line.
With no prefix argument, successive calls place point according
to the cycling order defined by `recenter-positions'.

A prefix argument is handled like `recenter':
 With numeric prefix ARG, move current line to window-line ARG.
 With plain `C-u', move current line to window center."
  (interactive "P")
  (cond
   (arg (recenter arg))                 ; Always respect ARG.
   (t
    (setq recenter-last-op
          (if (eq this-command last-command)
              (car (or (cdr (member recenter-last-op recenter-positions))
                       recenter-positions))
            (car recenter-positions)))
    (let ((this-scroll-margin
           (min (max 0 scroll-margin)
                (truncate (/ (window-body-height) 4.0)))))
      (cond ((eq recenter-last-op 'middle)
             (recenter))
            ((eq recenter-last-op 'top)
             (recenter this-scroll-margin))
            ((eq recenter-last-op 'bottom)
             (recenter (- -1 this-scroll-margin)))
            ((integerp recenter-last-op)
             (recenter recenter-last-op))
            ((floatp recenter-last-op)
             (recenter (round (* recenter-last-op (window-height))))))))))

(define-key global-map [?\C-l] 'recenter-top-bottom)

(defun move-to-window-line-top-bottom (&optional arg)
  "Position point relative to window.

With a prefix argument ARG, acts like `move-to-window-line'.

With no argument, positions point at center of window.
Successive calls position point at positions defined
by `recenter-positions'."
  (interactive "P")
  (cond
   (arg (move-to-window-line arg))      ; Always respect ARG.
   (t
    (setq recenter-last-op
          (if (eq this-command last-command)
              (car (or (cdr (member recenter-last-op recenter-positions))
                       recenter-positions))
            (car recenter-positions)))
    (let ((this-scroll-margin
           (min (max 0 scroll-margin)
                (truncate (/ (window-body-height) 4.0)))))
      (cond ((eq recenter-last-op 'middle)
             (call-interactively 'move-to-window-line))
            ((eq recenter-last-op 'top)
             (move-to-window-line this-scroll-margin))
            ((eq recenter-last-op 'bottom)
             (move-to-window-line (- -1 this-scroll-margin)))
            ((integerp recenter-last-op)
             (move-to-window-line recenter-last-op))
            ((floatp recenter-last-op)
             (move-to-window-line (round (* recenter-last-op (window-height))))))))))

(define-key global-map [?\M-r] 'move-to-window-line-top-bottom)
\f
;;; Scrolling commands.

;;; Scrolling commands which do not signal errors at top/bottom
;;; of buffer at first key-press (instead move to top/bottom
;;; of buffer).

(defcustom scroll-error-top-bottom nil
  "Move point to top/bottom of buffer before signaling a scrolling error.
A value of nil means just signal an error if no more scrolling possible.
A value of t means point moves to the beginning or the end of the buffer
\(depending on scrolling direction) when no more scrolling possible.
When point is already on that position, then signal an error."
  :type 'boolean
  :group 'windows
  :version "24.1")

(defun scroll-up-command (&optional arg)
  "Scroll text of selected window upward ARG lines; or near full screen if no ARG.
If `scroll-error-top-bottom' is non-nil and `scroll-up' cannot
scroll window further, move cursor to the bottom line.
When point is already on that position, then signal an error.
A near full screen is `next-screen-context-lines' less than a full screen.
Negative ARG means scroll downward.
If ARG is the atom `-', scroll downward by nearly full screen."
  (interactive "^P")
  (cond
   ((null scroll-error-top-bottom)
    (scroll-up arg))
   ((eq arg '-)
    (scroll-down-command nil))
   ((< (prefix-numeric-value arg) 0)
    (scroll-down-command (- (prefix-numeric-value arg))))
   ((eobp)
    (scroll-up arg))                    ; signal error
   (t
    (condition-case nil
        (scroll-up arg)
      (end-of-buffer
       (if arg
           ;; When scrolling by ARG lines can't be done,
           ;; move by ARG lines instead.
           (forward-line arg)
         ;; When ARG is nil for full-screen scrolling,
         ;; move to the bottom of the buffer.
         (goto-char (point-max))))))))

(put 'scroll-up-command 'scroll-command t)

(defun scroll-down-command (&optional arg)
  "Scroll text of selected window down ARG lines; or near full screen if no ARG.
If `scroll-error-top-bottom' is non-nil and `scroll-down' cannot
scroll window further, move cursor to the top line.
When point is already on that position, then signal an error.
A near full screen is `next-screen-context-lines' less than a full screen.
Negative ARG means scroll upward.
If ARG is the atom `-', scroll upward by nearly full screen."
  (interactive "^P")
  (cond
   ((null scroll-error-top-bottom)
    (scroll-down arg))
   ((eq arg '-)
    (scroll-up-command nil))
   ((< (prefix-numeric-value arg) 0)
    (scroll-up-command (- (prefix-numeric-value arg))))
   ((bobp)
    (scroll-down arg))                  ; signal error
   (t
    (condition-case nil
        (scroll-down arg)
      (beginning-of-buffer
       (if arg
           ;; When scrolling by ARG lines can't be done,
           ;; move by ARG lines instead.
           (forward-line (- arg))
         ;; When ARG is nil for full-screen scrolling,
         ;; move to the top of the buffer.
         (goto-char (point-min))))))))

(put 'scroll-down-command 'scroll-command t)

;;; Scrolling commands which scroll a line instead of full screen.

(defun scroll-up-line (&optional arg)
  "Scroll text of selected window upward ARG lines; or one line if no ARG.
If ARG is omitted or nil, scroll upward by one line.
This is different from `scroll-up-command' that scrolls a full screen."
  (interactive "p")
  (scroll-up (or arg 1)))

(put 'scroll-up-line 'scroll-command t)

(defun scroll-down-line (&optional arg)
  "Scroll text of selected window down ARG lines; or one line if no ARG.
If ARG is omitted or nil, scroll down by one line.
This is different from `scroll-down-command' that scrolls a full screen."
  (interactive "p")
  (scroll-down (or arg 1)))

(put 'scroll-down-line 'scroll-command t)

\f
(defun scroll-other-window-down (lines)
  "Scroll the \"other window\" down.
For more details, see the documentation for `scroll-other-window'."
  (interactive "P")
  (scroll-other-window
   ;; Just invert the argument's meaning.
   ;; We can do that without knowing which window it will be.
   (if (eq lines '-) nil
     (if (null lines) '-
       (- (prefix-numeric-value lines))))))

(defun beginning-of-buffer-other-window (arg)
  "Move point to the beginning of the buffer in the other window.
Leave mark at previous position.
With arg N, put point N/10 of the way from the true beginning."
  (interactive "P")
  (let ((orig-window (selected-window))
        (window (other-window-for-scrolling)))
    ;; We use unwind-protect rather than save-window-excursion
    ;; because the latter would preserve the things we want to change.
    (unwind-protect
        (progn
          (select-window window)
          ;; Set point and mark in that window's buffer.
          (with-no-warnings
           (beginning-of-buffer arg))
          ;; Set point accordingly.
          (recenter '(t)))
      (select-window orig-window))))

(defun end-of-buffer-other-window (arg)
  "Move point to the end of the buffer in the other window.
Leave mark at previous position.
With arg N, put point N/10 of the way from the true end."
  (interactive "P")
  ;; See beginning-of-buffer-other-window for comments.
  (let ((orig-window (selected-window))
        (window (other-window-for-scrolling)))
    (unwind-protect
        (progn
          (select-window window)
          (with-no-warnings
           (end-of-buffer arg))
          (recenter '(t)))
      (select-window orig-window))))
\f
(defvar mouse-autoselect-window-timer nil
  "Timer used by delayed window autoselection.")

(defvar mouse-autoselect-window-position nil
  "Last mouse position recorded by delayed window autoselection.")

(defvar mouse-autoselect-window-window nil
  "Last window recorded by delayed window autoselection.")

(defvar mouse-autoselect-window-state nil
  "When non-nil, special state of delayed window autoselection.
Possible values are `suspend' (suspend autoselection after a menu or
scrollbar interaction) and `select' (the next invocation of
`handle-select-window' shall select the window immediately).")

(defun mouse-autoselect-window-cancel (&optional force)
  "Cancel delayed window autoselection.
Optional argument FORCE means cancel unconditionally."
  (unless (and (not force)
               ;; Don't cancel for select-window or select-frame events
               ;; or when the user drags a scroll bar.
               (or (memq this-command
                         '(handle-select-window handle-switch-frame))
                   (and (eq this-command 'scroll-bar-toolkit-scroll)
                        (memq (nth 4 (event-end last-input-event))
                              '(handle end-scroll)))))
    (setq mouse-autoselect-window-state nil)
    (when (timerp mouse-autoselect-window-timer)
      (cancel-timer mouse-autoselect-window-timer))
    (remove-hook 'pre-command-hook 'mouse-autoselect-window-cancel)))

(defun mouse-autoselect-window-start (mouse-position &optional window suspend)
  "Start delayed window autoselection.
MOUSE-POSITION is the last position where the mouse was seen as returned
by `mouse-position'.  Optional argument WINDOW non-nil denotes the
window where the mouse was seen.  Optional argument SUSPEND non-nil
means suspend autoselection."
  ;; Record values for MOUSE-POSITION, WINDOW, and SUSPEND.
  (setq mouse-autoselect-window-position mouse-position)
  (when window (setq mouse-autoselect-window-window window))
  (setq mouse-autoselect-window-state (when suspend 'suspend))
  ;; Install timer which runs `mouse-autoselect-window-select' after
  ;; `mouse-autoselect-window' seconds.
  (setq mouse-autoselect-window-timer
        (run-at-time
         (abs mouse-autoselect-window) nil 'mouse-autoselect-window-select)))

(defun mouse-autoselect-window-select ()
  "Select window with delayed window autoselection.
If the mouse position has stabilized in a non-selected window, select
that window.  The minibuffer window is selected only if the minibuffer
is active.  This function is run by `mouse-autoselect-window-timer'."
  (ignore-errors
   (let* ((mouse-position (mouse-position))
          (window
           (ignore-errors
            (window-at (cadr mouse-position) (cddr mouse-position)
                       (car mouse-position)))))
     (cond
      ((or (menu-or-popup-active-p)
           (and window
                (not (coordinates-in-window-p (cdr mouse-position) window))))
       ;; A menu / popup dialog is active or the mouse is on the scroll-bar
       ;; of WINDOW, temporarily suspend delayed autoselection.
       (mouse-autoselect-window-start mouse-position nil t))
      ((eq mouse-autoselect-window-state 'suspend)
       ;; Delayed autoselection was temporarily suspended, reenable it.
       (mouse-autoselect-window-start mouse-position))
      ((and window (not (eq window (selected-window)))
            (or (not (numberp mouse-autoselect-window))
                (and (> mouse-autoselect-window 0)
                     ;; If `mouse-autoselect-window' is positive, select
                     ;; window if the window is the same as before.
                     (eq window mouse-autoselect-window-window))
                ;; Otherwise select window if the mouse is at the same
                ;; position as before.  Observe that the first test after
                ;; starting autoselection usually fails since the value of
                ;; `mouse-autoselect-window-position' recorded there is the
                ;; position where the mouse has entered the new window and
                ;; not necessarily where the mouse has stopped moving.
                (equal mouse-position mouse-autoselect-window-position))
            ;; The minibuffer is a candidate window if it's active.
            (or (not (window-minibuffer-p window))
                (eq window (active-minibuffer-window))))
       ;; Mouse position has stabilized in non-selected window: Cancel
       ;; delayed autoselection and try to select that window.
       (mouse-autoselect-window-cancel t)
       ;; Select window where mouse appears unless the selected window is the
       ;; minibuffer.  Use `unread-command-events' in order to execute pre-
       ;; and post-command hooks and trigger idle timers.  To avoid delaying
       ;; autoselection again, set `mouse-autoselect-window-state'."
       (unless (window-minibuffer-p (selected-window))
         (setq mouse-autoselect-window-state 'select)
         (setq unread-command-events
               (cons (list 'select-window (list window))
                     unread-command-events))))
      ((or (and window (eq window (selected-window)))
           (not (numberp mouse-autoselect-window))
           (equal mouse-position mouse-autoselect-window-position))
       ;; Mouse position has either stabilized in the selected window or at
       ;; `mouse-autoselect-window-position': Cancel delayed autoselection.
       (mouse-autoselect-window-cancel t))
      (t
       ;; Mouse position has not stabilized yet, resume delayed
       ;; autoselection.
       (mouse-autoselect-window-start mouse-position window))))))

(defun handle-select-window (event)
  "Handle select-window events."
  (interactive "e")
  (let ((window (posn-window (event-start event))))
    (unless (or (not (window-live-p window))
                ;; Don't switch if we're currently in the minibuffer.
                ;; This tries to work around problems where the
                ;; minibuffer gets unselected unexpectedly, and where
                ;; you then have to move your mouse all the way down to
                ;; the minibuffer to select it.
                (window-minibuffer-p (selected-window))
                ;; Don't switch to minibuffer window unless it's active.
                (and (window-minibuffer-p window)
                     (not (minibuffer-window-active-p window)))
                ;; Don't switch when autoselection shall be delayed.
                (and (numberp mouse-autoselect-window)
                     (not (zerop mouse-autoselect-window))
                     (not (eq mouse-autoselect-window-state 'select))
                     (progn
                       ;; Cancel any delayed autoselection.
                       (mouse-autoselect-window-cancel t)
                       ;; Start delayed autoselection from current mouse
                       ;; position and window.
                       (mouse-autoselect-window-start (mouse-position) window)
                       ;; Executing a command cancels delayed autoselection.
                       (add-hook
                        'pre-command-hook 'mouse-autoselect-window-cancel))))
      (when mouse-autoselect-window
        ;; Reset state of delayed autoselection.
        (setq mouse-autoselect-window-state nil)
        ;; Run `mouse-leave-buffer-hook' when autoselecting window.
        (run-hooks 'mouse-leave-buffer-hook))
      ;; Clear echo area.
      (message nil)
      (select-window window))))

(defun truncated-partial-width-window-p (&optional window)
  "Return non-nil if lines in WINDOW are specifically truncated due to its width.
WINDOW must be a live window and defaults to the selected one.
Return nil if WINDOW is not a partial-width window
 (regardless of the value of `truncate-lines').
Otherwise, consult the value of `truncate-partial-width-windows'
 for the buffer shown in WINDOW."
  (setq window (window-normalize-window window t))
  (unless (window-full-width-p window)
    (let ((t-p-w-w (buffer-local-value 'truncate-partial-width-windows
                                       (window-buffer window))))
      (if (integerp t-p-w-w)
          (< (window-width window) t-p-w-w)
        t-p-w-w))))
\f
;; Some of these are in tutorial--default-keys, so update that if you
;; change these.
(define-key ctl-x-map "0" 'delete-window)
(define-key ctl-x-map "1" 'delete-other-windows)
(define-key ctl-x-map "2" 'split-window-below)
(define-key ctl-x-map "3" 'split-window-right)
(define-key ctl-x-map "o" 'other-window)
(define-key ctl-x-map "^" 'enlarge-window)
(define-key ctl-x-map "}" 'enlarge-window-horizontally)
(define-key ctl-x-map "{" 'shrink-window-horizontally)
(define-key ctl-x-map "-" 'shrink-window-if-larger-than-buffer)
(define-key ctl-x-map "+" 'balance-windows)
(define-key ctl-x-4-map "0" 'kill-buffer-and-window)

;;; window.el ends here