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scroll-bar.el
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scroll-bar.el
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;;; 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, 675 Mass Ave, Cambridge, MA 02139, USA.
;;; Code:
;;; Commentary:
;; Window-system-independent bindings of mouse clicks on the scroll bar.
;; Presently emulates the scroll-bar behavior of xterm.
;;; Code:
(require 'mouse)
;;;; 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))))
;;;; Helpful functions for enabling and disabling scroll bars.
(defun scroll-bar-mode (flag)
"Toggle display of vertical scroll bars on each frame.
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)))
;; Obtain the current setting by looking at default-frame-alist.
(let ((scroll-bar-mode
(let ((assq (assq 'vertical-scroll-bars default-frame-alist)))
(if assq (cdr assq) t))))
;; Tweedle it according to the argument.
(setq scroll-bar-mode (if (null flag) (not scroll-bar-mode)
(or (not (numberp flag)) (>= flag 0))))
;; Apply it to default-frame-alist.
(mapcar
(function
(lambda (param-name)
(let ((parameter (assq param-name default-frame-alist)))
(if (consp parameter)
(setcdr parameter scroll-bar-mode)
(setq default-frame-alist
(cons (cons param-name scroll-bar-mode)
default-frame-alist))))))
'(vertical-scroll-bars horizontal-scroll-bars))
;; Apply it to existing frames.
(let ((frames (frame-list)))
(while frames
(modify-frame-parameters
(car frames)
(list (cons 'vertical-scroll-bars scroll-bar-mode)
(cons 'horizontal-scroll-bars scroll-bar-mode)))
(setq frames (cdr frames))))))
;;;; 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))))))
;; 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)))
(scroll-bar-drag-1 event)
(let (point-before-scroll)
(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))))))))
(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))))
;;;; 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)
(provide 'scroll-bar)
;;; scroll-bar.el ends here