lisp/scroll-bar.el

   1 ;;; scroll-bar.el --- window system-independent scroll bar support
   2
   3 ;; Copyright (C) 1993, 1994, 1995, 1999, 2000, 2001, 2002, 2003,
   4 ;;   2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
   5
   6 ;; Maintainer: FSF
   7 ;; Keywords: hardware
   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 3, 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 the
  23 ;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  24 ;; Boston, MA 02110-1301, USA.
  25
  26 ;;; Commentary:
  27
  28 ;; Window-system-independent bindings of mouse clicks on the scroll bar.
  29 ;; Presently emulates the scroll-bar behavior of xterm.
  30
  31 ;;; Code:
  32
  33 (require 'mouse)
  34
  35 \f
  36 ;;;; Utilities.
  37
  38 (defun scroll-bar-event-ratio (event)
  39   "Given a scroll bar event EVENT, return the scroll bar position as a ratio.
  40 The value is a cons cell (PORTION . WHOLE) containing two integers
  41 whose ratio gives the event's vertical position in the scroll bar, with 0
  42 referring to the top and 1 to the bottom."
  43   (nth 2 event))
  44
  45 (defun scroll-bar-scale (num-denom whole)
  46   "Given a pair (NUM . DENOM) and WHOLE, return (/ (* NUM WHOLE) DENOM).
  47 This is handy for scaling a position on a scroll bar into real units,
  48 like buffer positions.  If SCROLL-BAR-POS is the (PORTION . WHOLE) pair
  49 from a scroll bar event, then (scroll-bar-scale SCROLL-BAR-POS
  50 \(buffer-size)) is the position in the current buffer corresponding to
  51 that scroll bar position."
  52   ;; We multiply before we divide to maintain precision.
  53   ;; We use floating point because the product of a large buffer size
  54   ;; with a large scroll bar portion can easily overflow a lisp int.
  55   (truncate (/ (* (float (car num-denom)) whole) (cdr num-denom))))
  56
  57 (defun scroll-bar-columns (side)
  58   "Return the width, measured in columns, of the vertical scrollbar on SIDE.
  59 SIDE must be the symbol `left' or `right'."
  60   (let* ((wsb   (window-scroll-bars))
  61          (vtype (nth 2 wsb))
  62          (cols  (nth 1 wsb)))
  63     (cond
  64      ((not (memq side '(left right)))
  65       (error "`left' or `right' expected instead of %S" side))
  66      ((and (eq vtype side) cols))
  67      ((eq (frame-parameter nil 'vertical-scroll-bars) side)
  68       ;; nil means it's a non-toolkit scroll bar, and its width in
  69       ;; columns is 14 pixels rounded up.
  70       (ceiling (or (frame-parameter nil 'scroll-bar-width) 14)
  71                (frame-char-width)))
  72      (0))))
  73
  74 \f
  75 ;;;; Helpful functions for enabling and disabling scroll bars.
  76
  77 (defvar scroll-bar-mode)
  78 (defvar previous-scroll-bar-mode nil)
  79
  80 (defvar scroll-bar-mode-explicit nil
  81   "Non-nil means `set-scroll-bar-mode' should really do something.
  82 This is nil while loading `scroll-bar.el', and t afterward.")
  83
  84 (defun set-scroll-bar-mode-1 (ignore value)
  85   (set-scroll-bar-mode value))
  86
  87 (defun set-scroll-bar-mode (value)
  88   "Set `scroll-bar-mode' to VALUE and put the new value into effect."
  89   (if scroll-bar-mode
  90       (setq previous-scroll-bar-mode scroll-bar-mode))
  91
  92   (setq scroll-bar-mode value)
  93
  94   (when scroll-bar-mode-explicit
  95     (modify-all-frames-parameters (list (cons 'vertical-scroll-bars
  96                                               scroll-bar-mode)))))
  97
  98 (defcustom scroll-bar-mode default-frame-scroll-bars
  99   "*Specify whether to have vertical scroll bars, and on which side.
 100 Possible values are nil (no scroll bars), `left' (scroll bars on left)
 101 and `right' (scroll bars on right).
 102 To set this variable in a Lisp program, use `set-scroll-bar-mode'
 103 to make it take real effect.
 104 Setting the variable with a customization buffer also takes effect."
 105   :type '(choice (const :tag "none (nil)" nil)
 106                  (const left)
 107                  (const right))
 108   :group 'frames
 109   ;; The default value for :initialize would try to use :set
 110   ;; when processing the file in cus-dep.el.
 111   :initialize 'custom-initialize-default
 112   :set 'set-scroll-bar-mode-1)
 113
 114 ;; We just set scroll-bar-mode, but that was the default.
 115 ;; If it is set again, that is for real.
 116 (setq scroll-bar-mode-explicit t)
 117
 118 (defun scroll-bar-mode (&optional flag)
 119   "Toggle display of vertical scroll bars on all frames.
 120 This command applies to all frames that exist and frames to be
 121 created in the future.
 122 With a numeric argument, if the argument is negative,
 123 turn off scroll bars; otherwise, turn on scroll bars."
 124   (interactive "P")
 125
 126   ;; Tweedle the variable according to the argument.
 127   (set-scroll-bar-mode (if (if (null flag)
 128                                (not scroll-bar-mode)
 129                              (setq flag (prefix-numeric-value flag))
 130                              (or (not (numberp flag)) (>= flag 0)))
 131                            (or previous-scroll-bar-mode
 132                                default-frame-scroll-bars))))
 133
 134 (defun toggle-scroll-bar (arg)
 135   "Toggle whether or not the selected frame has vertical scroll bars.
 136 With arg, turn vertical scroll bars on if and only if arg is positive.
 137 The variable `scroll-bar-mode' controls which side the scroll bars are on
 138 when they are turned on; if it is nil, they go on the left."
 139   (interactive "P")
 140   (if (null arg)
 141       (setq arg
 142             (if (cdr (assq 'vertical-scroll-bars
 143                            (frame-parameters (selected-frame))))
 144                 -1 1))
 145     (setq arg (prefix-numeric-value arg)))
 146   (modify-frame-parameters
 147    (selected-frame)
 148    (list (cons 'vertical-scroll-bars
 149                (if (> arg 0)
 150                    (or scroll-bar-mode default-frame-scroll-bars))))))
 151
 152 (defun toggle-horizontal-scroll-bar (arg)
 153   "Toggle whether or not the selected frame has horizontal scroll bars.
 154 With arg, turn horizontal scroll bars on if and only if arg is positive.
 155 Horizontal scroll bars aren't implemented yet."
 156   (interactive "P")
 157   (error "Horizontal scroll bars aren't implemented yet"))
 158 \f
 159 ;;;; Buffer navigation using the scroll bar.
 160
 161 ;;; This was used for up-events on button 2, but no longer.
 162 (defun scroll-bar-set-window-start (event)
 163   "Set the window start according to where the scroll bar is dragged.
 164 EVENT should be a scroll bar click or drag event."
 165   (interactive "e")
 166   (let* ((end-position (event-end event))
 167          (window (nth 0 end-position))
 168          (portion-whole (nth 2 end-position)))
 169     (save-excursion
 170       (set-buffer (window-buffer window))
 171       (save-excursion
 172         (goto-char (+ (point-min)
 173                       (scroll-bar-scale portion-whole
 174                                         (- (point-max) (point-min)))))
 175         (beginning-of-line)
 176         (set-window-start window (point))))))
 177
 178 (defun scroll-bar-drag-position (portion-whole)
 179   "Calculate new window start for drag event."
 180   (save-excursion
 181     (goto-char (+ (point-min)
 182                   (scroll-bar-scale portion-whole
 183                                     (- (point-max) (point-min)))))
 184     (beginning-of-line)
 185     (point)))
 186
 187 (defun scroll-bar-maybe-set-window-start (event)
 188   "Set the window start according to where the scroll bar is dragged.
 189 Only change window start if the new start is substantially different.
 190 EVENT should be a scroll bar click or drag event."
 191   (interactive "e")
 192   (let* ((end-position (event-end event))
 193          (window (nth 0 end-position))
 194          (portion-whole (nth 2 end-position))
 195          (next-portion-whole (cons (1+ (car portion-whole))
 196                                    (cdr portion-whole)))
 197          portion-start
 198          next-portion-start
 199          (current-start (window-start window)))
 200     (save-excursion
 201       (set-buffer (window-buffer window))
 202       (setq portion-start (scroll-bar-drag-position portion-whole))
 203       (setq next-portion-start (max
 204                                 (scroll-bar-drag-position next-portion-whole)
 205                                 (1+ portion-start)))
 206       (if (or (>= current-start next-portion-start)
 207               (< current-start portion-start))
 208           (set-window-start window portion-start)
 209         ;; Always set window start, to ensure scroll bar position is updated.
 210         (set-window-start window current-start)))))
 211
 212 ;; Scroll the window to the proper position for EVENT.
 213 (defun scroll-bar-drag-1 (event)
 214   (let* ((start-position (event-start event))
 215          (window (nth 0 start-position))
 216          (portion-whole (nth 2 start-position)))
 217     (save-excursion
 218       (set-buffer (window-buffer window))
 219       ;; Calculate position relative to the accessible part of the buffer.
 220       (goto-char (+ (point-min)
 221                     (scroll-bar-scale portion-whole
 222                                       (- (point-max) (point-min)))))
 223       (vertical-motion 0 window)
 224       (set-window-start window (point)))))
 225
 226 (defun scroll-bar-drag (event)
 227   "Scroll the window by dragging the scroll bar slider.
 228 If you click outside the slider, the window scrolls to bring the slider there."
 229   (interactive "e")
 230   (let* (done
 231          (echo-keystrokes 0)
 232          (end-position (event-end event))
 233          (window (nth 0 end-position))
 234          (before-scroll))
 235     (with-current-buffer (window-buffer window)
 236       (setq before-scroll point-before-scroll))
 237     (save-selected-window
 238       (select-window window)
 239       (setq before-scroll
 240             (or before-scroll (point))))
 241     (scroll-bar-drag-1 event)
 242     (track-mouse
 243       (while (not done)
 244         (setq event (read-event))
 245         (if (eq (car-safe event) 'mouse-movement)
 246             (setq event (read-event)))
 247         (cond ((eq (car-safe event) 'scroll-bar-movement)
 248                (scroll-bar-drag-1 event))
 249               (t
 250                ;; Exit when we get the drag event; ignore that event.
 251                (setq done t)))))
 252     (sit-for 0)
 253     (with-current-buffer (window-buffer window)
 254       (setq point-before-scroll before-scroll))))
 255
 256 (defun scroll-bar-scroll-down (event)
 257   "Scroll the window's top line down to the location of the scroll bar click.
 258 EVENT should be a scroll bar click."
 259   (interactive "e")
 260   (let* ((end-position (event-end event))
 261          (window (nth 0 end-position))
 262          (before-scroll))
 263     (with-current-buffer (window-buffer window)
 264       (setq before-scroll point-before-scroll))
 265     (unwind-protect
 266         (save-selected-window
 267           (let ((portion-whole (nth 2 end-position)))
 268             (select-window window)
 269             (setq before-scroll
 270                   (or before-scroll (point)))
 271             (scroll-down
 272              (scroll-bar-scale portion-whole (1- (window-height)))))
 273           (sit-for 0))
 274       (with-current-buffer (window-buffer window)
 275         (setq point-before-scroll before-scroll)))))
 276
 277 (defun scroll-bar-scroll-up (event)
 278   "Scroll the line next to the scroll bar click to the top of the window.
 279 EVENT should be a scroll bar click."
 280   (interactive "e")
 281   (let* ((end-position (event-end event))
 282          (window (nth 0 end-position))
 283          (before-scroll))
 284     (with-current-buffer (window-buffer window)
 285       (setq before-scroll point-before-scroll))
 286     (unwind-protect
 287         (save-selected-window
 288           (let ((portion-whole (nth 2 end-position)))
 289             (select-window window)
 290             (setq before-scroll
 291                   (or before-scroll (point)))
 292             (scroll-up
 293              (scroll-bar-scale portion-whole (1- (window-height)))))
 294           (sit-for 0))
 295       (with-current-buffer (window-buffer window)
 296         (setq point-before-scroll before-scroll)))))
 297
 298 \f
 299 ;;; Tookit scroll bars.
 300
 301 (defun scroll-bar-toolkit-scroll (event)
 302   (interactive "e")
 303   (let* ((end-position (event-end event))
 304          (window (nth 0 end-position))
 305          (part (nth 4 end-position))
 306          before-scroll)
 307     (cond ((eq part 'end-scroll))
 308           (t
 309            (with-current-buffer (window-buffer window)
 310              (setq before-scroll point-before-scroll))
 311            (save-selected-window
 312              (select-window window)
 313              (setq before-scroll (or before-scroll (point)))
 314              (cond ((eq part 'above-handle)
 315                     (scroll-up '-))
 316                    ((eq part 'below-handle)
 317                     (scroll-up nil))
 318                    ((eq part 'ratio)
 319                     (let* ((portion-whole (nth 2 end-position))
 320                            (lines (scroll-bar-scale portion-whole
 321                                                     (1- (window-height)))))
 322                       (scroll-up (cond ((not (zerop lines)) lines)
 323                                        ((< (car portion-whole) 0) -1)
 324                                        (t 1)))))
 325                    ((eq part 'up)
 326                     (scroll-up -1))
 327                    ((eq part 'down)
 328                     (scroll-up 1))
 329                    ((eq part 'top)
 330                     (set-window-start window (point-min)))
 331                    ((eq part 'bottom)
 332                     (goto-char (point-max))
 333                     (recenter))
 334                    ((eq part 'handle)
 335                     (scroll-bar-drag-1 event))))
 336            (sit-for 0)
 337            (with-current-buffer (window-buffer window)
 338              (setq point-before-scroll before-scroll))))))
 339
 340
 341 \f
 342 ;;;; Bindings.
 343
 344 ;;; For now, we'll set things up to work like xterm.
 345 (cond ((and (boundp 'x-toolkit-scroll-bars) x-toolkit-scroll-bars)
 346        (global-set-key [vertical-scroll-bar mouse-1]
 347                        'scroll-bar-toolkit-scroll))
 348       (t
 349        (global-set-key [vertical-scroll-bar mouse-1]
 350                        'scroll-bar-scroll-up)
 351        (global-set-key [vertical-scroll-bar drag-mouse-1]
 352                        'scroll-bar-scroll-up)
 353        (global-set-key [vertical-scroll-bar down-mouse-2]
 354                        'scroll-bar-drag)
 355        (global-set-key [vertical-scroll-bar mouse-3]
 356                        'scroll-bar-scroll-down)
 357        (global-set-key [vertical-scroll-bar drag-mouse-3]
 358                        'scroll-bar-scroll-down)))
 359
 360 \f
 361 (provide 'scroll-bar)
 362
 363 ;; arch-tag: 6f1d01d0-0b1e-4bf8-86db-d491e0f399f3
 364 ;;; scroll-bar.el ends here