lisp/electric.el

   1 ;;; electric.el --- window maker and Command loop for `electric' modes.
   2
   3 ;; Copyright (C) 1985, 1986 Free Software Foundation, Inc.
   4
   5 ;; Author: K. Shane Hartman
   6 ;; Maintainer: FSF
   7 ;; Keywords: extensions
   8
   9 ;; This file is part of GNU Emacs.
  10
  11 ;; GNU Emacs is free software; you can redistribute it and/or modify
  12 ;; it under the terms of the GNU General Public License as published by
  13 ;; the Free Software Foundation; either version 2, or (at your option)
  14 ;; any later version.
  15
  16 ;; GNU Emacs is distributed in the hope that it will be useful,
  17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19 ;; GNU General Public License for more details.
  20
  21 ;; You should have received a copy of the GNU General Public License
  22 ;; along with GNU Emacs; see the file COPYING.  If not, write to
  23 ;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  24
  25 ;;; Commentary:
  26
  27 ; zaaaaaaap
  28
  29 ;;; Code:
  30
  31 ;; This loop is the guts for non-standard modes which retain control
  32 ;; until some event occurs.  It is a `do-forever', the only way out is to
  33 ;; throw.  It assumes that you have set up the keymap, window, and
  34 ;; everything else: all it does is read commands and execute them -
  35 ;; providing error messages should one occur (if there is no loop
  36 ;; function - which see).  The required argument is a tag which should
  37 ;; expect a value of nil if the user decides to punt. The
  38 ;; second argument is a prompt string (defaults to "->").  Given third
  39 ;; argument non-nil, it INHIBITS quitting unless the user types C-g at
  40 ;; toplevel.  This is so user can do things like C-u C-g and not get
  41 ;; thrown out.  Fourth argument, if non-nil, should be a function of two
  42 ;; arguments which is called after every command is executed.  The fifth
  43 ;; argument, if provided, is the state variable for the function.  If the
  44 ;; loop-function gets an error, the loop will abort WITHOUT throwing
  45 ;; (moral: use unwind-protect around call to this function for any
  46 ;; critical stuff).  The second argument for the loop function is the
  47 ;; conditions for any error that occurred or nil if none.
  48
  49 (defun Electric-command-loop (return-tag
  50                               &optional prompt inhibit-quit
  51                                         loop-function loop-state)
  52   (if (not prompt) (setq prompt "->"))
  53   (let (cmd (err nil))
  54     (while t
  55       (setq cmd (read-key-sequence (if (stringp prompt)
  56                                        prompt (funcall prompt))))
  57       (setq last-command-char (aref cmd (1- (length cmd)))
  58             this-command (key-binding cmd)
  59             cmd this-command)
  60       (if (or (prog1 quit-flag (setq quit-flag nil))
  61               (eq last-input-char ?\C-g))
  62           (progn (setq unread-command-events nil
  63                        prefix-arg nil)
  64                  ;; If it wasn't cancelling a prefix character, then quit.
  65                  (if (or (= (length (this-command-keys)) 1)
  66                          (not inhibit-quit)) ; safety
  67                      (progn (ding)
  68                             (message "Quit")
  69                             (throw return-tag nil))
  70                    (setq cmd nil))))
  71       (setq current-prefix-arg prefix-arg)
  72       (if cmd
  73           (condition-case conditions
  74               (progn (command-execute cmd)
  75                      (setq last-command this-command)
  76                      (if (or (prog1 quit-flag (setq quit-flag nil))
  77                              (eq last-input-char ?\C-g))
  78                          (progn (setq unread-command-events nil)
  79                                 (if (not inhibit-quit)
  80                                     (progn (ding)
  81                                            (message "Quit")
  82                                            (throw return-tag nil))
  83                                   (ding)))))
  84             (buffer-read-only (if loop-function
  85                                   (setq err conditions)
  86                                 (ding)
  87                                 (message "Buffer is read-only")
  88                                 (sit-for 2)))
  89             (beginning-of-buffer (if loop-function
  90                                      (setq err conditions)
  91                                    (ding)
  92                                    (message "Beginning of Buffer")
  93                                    (sit-for 2)))
  94             (end-of-buffer (if loop-function
  95                                (setq err conditions)
  96                              (ding)
  97                              (message "End of Buffer")
  98                              (sit-for 2)))
  99             (error (if loop-function
 100                        (setq err conditions)
 101                      (ding)
 102                      (message "Error: %s"
 103                               (if (eq (car conditions) 'error)
 104                                   (car (cdr conditions))
 105                                 (prin1-to-string conditions)))
 106                      (sit-for 2))))
 107         (ding))
 108       (if loop-function (funcall loop-function loop-state err))))
 109   (ding)
 110   (throw return-tag nil))
 111
 112 ;; This function is like pop-to-buffer, sort of.
 113 ;; The algorithm is
 114 ;; If there is a window displaying buffer
 115 ;;      Select it
 116 ;; Else if there is only one window
 117 ;;      Split it, selecting the window on the bottom with height being
 118 ;;      the lesser of max-height (if non-nil) and the number of lines in
 119 ;;      the buffer to be displayed subject to window-min-height constraint.
 120 ;; Else
 121 ;;      Switch to buffer in the current window.
 122 ;;
 123 ;; Then if max-height is nil, and not all of the lines in the buffer
 124 ;; are displayed, grab the whole frame.
 125 ;;
 126 ;; Returns selected window on buffer positioned at point-min.
 127
 128 (defun Electric-pop-up-window (buffer &optional max-height)
 129   (let* ((win (or (get-buffer-window buffer) (selected-window)))
 130          (buf (get-buffer buffer))
 131          (one-window (one-window-p t))
 132          (pop-up-windows t)
 133          (target-height)
 134          (lines))
 135     (if (not buf)
 136         (error "Buffer %s does not exist" buffer)
 137       (save-excursion
 138         (set-buffer buf)
 139         (setq lines (count-lines (point-min) (point-max)))
 140         (setq target-height
 141               (min (max (if max-height (min max-height (1+ lines)) (1+ lines))
 142                         window-min-height)
 143                    (save-window-excursion
 144                      (delete-other-windows)
 145                      (1- (window-height (selected-window)))))))
 146       (cond ((and (eq (window-buffer win) buf))
 147              (select-window win))
 148             (one-window
 149              (goto-char (window-start win))
 150              (pop-to-buffer buffer)
 151              (setq win (selected-window))
 152              (enlarge-window (- target-height (window-height win))))
 153             (t
 154              (switch-to-buffer buf)))
 155       (if (and (not max-height)
 156                (> target-height (window-height (selected-window))))
 157           (progn (goto-char (window-start win))
 158                  (enlarge-window (- target-height (window-height win)))))
 159       (goto-char (point-min))
 160       win)))
 161
 162 (provide 'electric)
 163
 164 ;;; electric.el ends here