;;; scroll-bar.el --- window system-independent scroll bar support.
-;;; Copyright (C) 1993 Free Software Foundation, Inc.
+;; Copyright (C) 1993, 1994, 1995 Free Software Foundation, Inc.
;; Maintainer: FSF
;; Keywords: hardware
-;;; This file is part of GNU 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 2, or (at your option)
-;;; any later version.
+;; 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.
+;; 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, 675 Mass Ave, Cambridge, MA 02139, USA.
-
-;;; Code:
+;; 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)
(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))
"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)
- (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)))))))
+ (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.
(let* ((end-position (event-end event))
(window (nth 0 end-position))
(portion-whole (nth 2 end-position)))
- (select-window window)
- (scroll-down
- (scroll-bar-scale portion-whole (1- (window-height))))))
+ (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)
(let* ((end-position (event-end event))
(window (nth 0 end-position))
(portion-whole (nth 2 end-position)))
- (select-window window)
- (scroll-up
- (scroll-bar-scale portion-whole (1- (window-height))))))
+ (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