+;;; scroll-bar.el --- window system-independent scroll bar support.
+
+;; Copyright (C) 1993, 1994, 1995 Free Software Foundation, Inc.
+
+;; Maintainer: FSF
+;; Keywords: hardware
+
+;; 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 2, 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; see the file COPYING. If not, write to the
+;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+;; Boston, MA 02111-1307, USA.
+
+;;; Commentary:
+
+;; Window-system-independent bindings of mouse clicks on the scroll bar.
+;; Presently emulates the scroll-bar behavior of xterm.
+
+;;; Code:
+
+(require 'mouse)
+
+\f
+;;;; Utilities.
+
+(defun scroll-bar-event-ratio (event)
+ "Given a scroll bar event EVENT, return the scroll bar position as a ratio.
+The value is a cons cell (PORTION . WHOLE) containing two integers
+whose ratio gives the event's vertical position in the scroll bar, with 0
+referring to the top and 1 to the bottom."
+ (nth 2 event))
+
+(defun scroll-bar-scale (num-denom whole)
+ "Given a pair (NUM . DENOM) and WHOLE, return (/ (* NUM WHOLE) DENOM).
+This is handy for scaling a position on a scroll bar into real units,
+like buffer positions. If SCROLL-BAR-POS is the (PORTION . WHOLE) pair
+from a scroll bar event, then (scroll-bar-scale SCROLL-BAR-POS
+\(buffer-size)) is the position in the current buffer corresponding to
+that scroll bar position."
+ ;; We multiply before we divide to maintain precision.
+ ;; We use floating point because the product of a large buffer size
+ ;; with a large scroll bar portion can easily overflow a lisp int.
+ (truncate (/ (* (float (car num-denom)) whole) (cdr num-denom))))
+
+\f
+;;;; Helpful functions for enabling and disabling scroll bars.
+
+(defvar scroll-bar-mode)
+
+(defvar scroll-bar-mode-explicit nil
+ "Non-nil means `set-scroll-bar-mode' should really do something.
+This is nil while loading `scroll-bar.el', and t afterward.")
+
+(defun set-scroll-bar-mode-1 (ignore value)
+ (set-scroll-bar-mode value))
+
+(defun set-scroll-bar-mode (value)
+ "Set `scroll-bar-mode' to VALUE and put the new value into effect."
+ (setq scroll-bar-mode value)
+
+ (when scroll-bar-mode-explicit
+ ;; Apply it to default-frame-alist.
+ (let ((parameter (assq 'vertical-scroll-bars default-frame-alist)))
+ (if (consp parameter)
+ (setcdr parameter scroll-bar-mode)
+ (setq default-frame-alist
+ (cons (cons 'vertical-scroll-bars scroll-bar-mode)
+ default-frame-alist))))
+
+ ;; Apply it to existing frames.
+ (let ((frames (frame-list)))
+ (while frames
+ (modify-frame-parameters
+ (car frames)
+ (list (cons 'vertical-scroll-bars scroll-bar-mode)))
+ (setq frames (cdr frames))))))
+
+(defcustom scroll-bar-mode 'left
+ "*Specify whether to have vertical scroll bars, and on which side.
+Possible values are nil (no scroll bars), `left' (scroll bars on left)
+and `right' (scroll bars on right).
+When you set the variable in a Lisp program, it takes effect for new frames,
+and for existing frames when `toggle-scroll-bar' is used.
+When you set this with the customization buffer,
+it takes effect immediately for all frames."
+ :type '(choice (const :tag "none (nil)")
+ (const left)
+ (const right))
+ :group 'frames
+ :set 'set-scroll-bar-mode-1)
+
+;; We just set scroll-bar-mode, but that was the default.
+;; If it is set again, that is for real.
+(setq scroll-bar-mode-explicit t)
+
+(defun scroll-bar-mode (flag)
+ "Toggle display of vertical scroll bars on all frames.
+This command applies to all frames that exist and frames to be
+created in the future.
+With a numeric argument, if the argument is negative,
+turn off scroll bars; otherwise, turn on scroll bars."
+ (interactive "P")
+ (if flag (setq flag (prefix-numeric-value flag)))
+
+ ;; Tweedle the variable according to the argument.
+ (set-scroll-bar-mode (if (null flag) (not scroll-bar-mode)
+ (and (or (not (numberp flag)) (>= flag 0))
+ 'left))))
+
+(defun toggle-scroll-bar (arg)
+ "Toggle whether or not the selected frame has vertical scroll bars.
+With arg, turn vertical scroll bars on if and only if arg is positive.
+The variable `scroll-bar-mode' controls which side the scroll bars are on
+when they are turned on; if it is nil, they go on the left."
+ (interactive "P")
+ (if (null arg)
+ (setq arg
+ (if (cdr (assq 'vertical-scroll-bars
+ (frame-parameters (selected-frame))))
+ -1 1))
+ (setq arg (prefix-numeric-value arg)))
+ (modify-frame-parameters (selected-frame)
+ (list (cons 'vertical-scroll-bars
+ (if (> arg 0)
+ (or scroll-bar-mode 'left))))))
+
+(defun toggle-horizontal-scroll-bar (arg)
+ "Toggle whether or not the selected frame has horizontal scroll bars.
+With arg, turn horizontal scroll bars on if and only if arg is positive.
+Horizontal scroll bars aren't implemented yet."
+ (interactive "P")
+ (error "Horizontal scroll bars aren't implemented yet"))
+\f
+;;;; Buffer navigation using the scroll bar.
+
+;;; This was used for up-events on button 2, but no longer.
+(defun scroll-bar-set-window-start (event)
+ "Set the window start according to where the scroll bar is dragged.
+EVENT should be a scroll bar click or drag event."
+ (interactive "e")
+ (let* ((end-position (event-end event))
+ (window (nth 0 end-position))
+ (portion-whole (nth 2 end-position)))
+ (save-excursion
+ (set-buffer (window-buffer window))
+ (save-excursion
+ (goto-char (+ (point-min)
+ (scroll-bar-scale portion-whole
+ (- (point-max) (point-min)))))
+ (beginning-of-line)
+ (set-window-start window (point))))))
+
+(defun scroll-bar-drag-position (portion-whole)
+ "Calculate new window start for drag event."
+ (save-excursion
+ (goto-char (+ (point-min)
+ (scroll-bar-scale portion-whole
+ (- (point-max) (point-min)))))
+ (beginning-of-line)
+ (point)))
+
+(defun scroll-bar-maybe-set-window-start (event)
+ "Set the window start according to where the scroll bar is dragged.
+Only change window start if the new start is substantially different.
+EVENT should be a scroll bar click or drag event."
+ (interactive "e")
+ (let* ((end-position (event-end event))
+ (window (nth 0 end-position))
+ (portion-whole (nth 2 end-position))
+ (next-portion-whole (cons (1+ (car portion-whole))
+ (cdr portion-whole)))
+ portion-start
+ next-portion-start
+ (current-start (window-start window)))
+ (save-excursion
+ (set-buffer (window-buffer window))
+ (setq portion-start (scroll-bar-drag-position portion-whole))
+ (setq next-portion-start (max
+ (scroll-bar-drag-position next-portion-whole)
+ (1+ portion-start)))
+ (if (or (>= current-start next-portion-start)
+ (< current-start portion-start))
+ (set-window-start window portion-start)
+ ;; Always set window start, to ensure scroll bar position is updated.
+ (set-window-start window current-start)))))
+
+;; Scroll the window to the proper position for EVENT.
+(defun scroll-bar-drag-1 (event)
+ (let* ((start-position (event-start event))
+ (window (nth 0 start-position))
+ (portion-whole (nth 2 start-position)))
+ (save-excursion
+ (set-buffer (window-buffer window))
+ ;; Calculate position relative to the accessible part of the buffer.
+ (goto-char (+ (point-min)
+ (scroll-bar-scale portion-whole
+ (- (point-max) (point-min)))))
+ (beginning-of-line)
+ (set-window-start window (point)))))
+
+(defun scroll-bar-drag (event)
+ "Scroll the window by dragging the scroll bar slider.
+If you click outside the slider, the window scrolls to bring the slider there."
+ (interactive "e")
+ (let* (done
+ (echo-keystrokes 0))
+ (or point-before-scroll
+ (setq point-before-scroll (point)))
+ ;; Our scrolling can move point; don't let that clear point-before-scroll.
+ (let (point-before-scroll)
+ (scroll-bar-drag-1 event)
+ (track-mouse
+ (while (not done)
+ (setq event (read-event))
+ (if (eq (car-safe event) 'mouse-movement)
+ (setq event (read-event)))
+ (cond ((eq (car-safe event) 'scroll-bar-movement)
+ (scroll-bar-drag-1 event))
+ (t
+ ;; Exit when we get the drag event; ignore that event.
+ (setq done t)))))
+ (sit-for 0))))
+
+(defun scroll-bar-scroll-down (event)
+ "Scroll the window's top line down to the location of the scroll bar click.
+EVENT should be a scroll bar click."
+ (interactive "e")
+ (let ((old-selected-window (selected-window)))
+ (unwind-protect
+ (progn
+ (let* ((end-position (event-end event))
+ (window (nth 0 end-position))
+ (portion-whole (nth 2 end-position)))
+ (let (point-before-scroll)
+ (select-window window))
+ (or point-before-scroll
+ (setq point-before-scroll (point)))
+ (let (point-before-scroll)
+ (scroll-down
+ (scroll-bar-scale portion-whole (1- (window-height)))))))
+ (select-window old-selected-window))))
+
+(defun scroll-bar-scroll-up (event)
+ "Scroll the line next to the scroll bar click to the top of the window.
+EVENT should be a scroll bar click."
+ (interactive "e")
+ (let ((old-selected-window (selected-window)))
+ (unwind-protect
+ (progn
+ (let* ((end-position (event-end event))
+ (window (nth 0 end-position))
+ (portion-whole (nth 2 end-position)))
+ (let (point-before-scroll)
+ (select-window window))
+ (or point-before-scroll
+ (setq point-before-scroll (point)))
+ (let (point-before-scroll)
+ (scroll-up
+ (scroll-bar-scale portion-whole (1- (window-height)))))))
+ (select-window old-selected-window))))
+
+\f
+;;;; Bindings.
+
+;;; For now, we'll set things up to work like xterm.
+(global-set-key [vertical-scroll-bar mouse-1] 'scroll-bar-scroll-up)
+(global-set-key [vertical-scroll-bar drag-mouse-1] 'scroll-bar-scroll-up)
+
+(global-set-key [vertical-scroll-bar down-mouse-2] 'scroll-bar-drag)
+
+(global-set-key [vertical-scroll-bar mouse-3] 'scroll-bar-scroll-down)
+(global-set-key [vertical-scroll-bar drag-mouse-3] 'scroll-bar-scroll-down)
+
+\f
+(provide 'scroll-bar)
+
+;;; scroll-bar.el ends here
HCoop / bpt / emacs.git / blobdiff