lisp/scroll-bar.el

   1 ;;; scroll-bar.el --- window system-independent scroll bar support
   2
   3 ;; Copyright (C) 1993-1995, 1999-2015 Free Software Foundation, Inc.
   4
   5 ;; Maintainer: emacs-devel@gnu.org
   6 ;; Keywords: hardware
   7 ;; Package: emacs
   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 of the License, or
  14 ;; (at your option) 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.  If not, see <http://www.gnu.org/licenses/>.
  23
  24 ;;; Commentary:
  25
  26 ;; Window-system-independent bindings of mouse clicks on the scroll bar.
  27 ;; Presently emulates the scroll-bar behavior of xterm.
  28
  29 ;;; Code:
  30
  31 (require 'mouse)
  32 (eval-when-compile (require 'cl-lib))
  33
  34 \f
  35 ;;;; Utilities.
  36
  37 (defun scroll-bar-event-ratio (event)
  38   "Given a scroll bar event EVENT, return the scroll bar position as a ratio.
  39 The value is a cons cell (PORTION . WHOLE) containing two integers
  40 whose ratio gives the event's vertical position in the scroll bar, with 0
  41 referring to the top and 1 to the bottom."
  42   (nth 2 event))
  43
  44 (defun scroll-bar-scale (num-denom whole)
  45   "Given a pair (NUM . DENOM) and WHOLE, return (/ (* NUM WHOLE) DENOM).
  46 This is handy for scaling a position on a scroll bar into real units,
  47 like buffer positions.  If SCROLL-BAR-POS is the (PORTION . WHOLE) pair
  48 from a scroll bar event, then (scroll-bar-scale SCROLL-BAR-POS
  49 \(buffer-size)) is the position in the current buffer corresponding to
  50 that scroll bar position."
  51   ;; We multiply before we divide to maintain precision.
  52   ;; We use floating point because the product of a large buffer size
  53   ;; with a large scroll bar portion can easily overflow a lisp int.
  54   (truncate (/ (* (float (car num-denom)) whole) (cdr num-denom))))
  55
  56 (defun scroll-bar-columns (side)
  57   "Return the width, measured in columns, of the vertical scrollbar on SIDE.
  58 SIDE must be the symbol `left' or `right'."
  59   (let* ((wsb   (window-scroll-bars))
  60          (vtype (nth 2 wsb))
  61          (cols  (nth 1 wsb)))
  62     (cond
  63      ((not (memq side '(left right)))
  64       (error "‘left’ or ‘right’ expected instead of %S" side))
  65      ((and (eq vtype side) cols))
  66      ((eq (frame-parameter nil 'vertical-scroll-bars) side)
  67       ;; nil means it's a non-toolkit scroll bar, and its width in
  68       ;; columns is 14 pixels rounded up.
  69       (ceiling (or (frame-parameter nil 'scroll-bar-width) 14)
  70                (frame-char-width)))
  71      (0))))
  72
  73 (defun scroll-bar-lines ()
  74   "Return the height, measured in lines, of the horizontal scrollbar."
  75   (let* ((wsb   (window-scroll-bars))
  76          (htype (nth 5 wsb))
  77          (lines  (nth 4 wsb)))
  78     (cond
  79      (htype lines)
  80      ((frame-parameter nil 'horizontal-scroll-bars)
  81       ;; nil means it's a non-toolkit scroll bar (which is currently
  82       ;; impossible), and its height in lines is 14 pixels rounded up.
  83       (ceiling (or (frame-parameter nil 'scroll-bar-height) 14)
  84                (frame-char-width)))
  85      (0))))
  86
  87 \f
  88 ;;;; Helpful functions for enabling and disabling scroll bars.
  89
  90 (defvar scroll-bar-mode)
  91 (defvar horizontal-scroll-bar-mode)
  92 (defvar previous-scroll-bar-mode nil)
  93
  94 (defvar scroll-bar-mode-explicit nil
  95   "Non-nil means `set-scroll-bar-mode' should really do something.
  96 This is nil while loading `scroll-bar.el', and t afterward.")
  97
  98 (defun set-scroll-bar-mode (value)
  99   "Set the scroll bar mode to VALUE and put the new value into effect.
 100 See the `scroll-bar-mode' variable for possible values to use."
 101   (if scroll-bar-mode
 102       (setq previous-scroll-bar-mode scroll-bar-mode))
 103
 104   (setq scroll-bar-mode value)
 105
 106   (when scroll-bar-mode-explicit
 107     (modify-all-frames-parameters (list (cons 'vertical-scroll-bars
 108                                               scroll-bar-mode)))))
 109
 110 (defcustom scroll-bar-mode default-frame-scroll-bars
 111   "Specify whether to have vertical scroll bars, and on which side.
 112 Possible values are nil (no scroll bars), `left' (scroll bars on left)
 113 and `right' (scroll bars on right).
 114 To set this variable in a Lisp program, use `set-scroll-bar-mode'
 115 to make it take real effect.
 116 Setting the variable with a customization buffer also takes effect."
 117   :type '(choice (const :tag "none (nil)" nil)
 118                  (const left)
 119                  (const right))
 120   :group 'frames
 121   ;; The default value for :initialize would try to use :set
 122   ;; when processing the file in cus-dep.el.
 123   :initialize 'custom-initialize-default
 124   :set (lambda (_sym val) (set-scroll-bar-mode val)))
 125
 126 ;; We just set scroll-bar-mode, but that was the default.
 127 ;; If it is set again, that is for real.
 128 (setq scroll-bar-mode-explicit t)
 129
 130 (defun get-scroll-bar-mode ()
 131   (declare (gv-setter set-scroll-bar-mode))
 132   scroll-bar-mode)
 133
 134 (define-minor-mode scroll-bar-mode
 135   "Toggle vertical scroll bars on all frames (Scroll Bar mode).
 136 With a prefix argument ARG, enable Scroll Bar mode if ARG is
 137 positive, and disable it otherwise.  If called from Lisp, enable
 138 the mode if ARG is omitted or nil.
 139
 140 This command applies to all frames that exist and frames to be
 141 created in the future."
 142   :variable ((get-scroll-bar-mode)
 143              . (lambda (v) (set-scroll-bar-mode
 144                             (if v (or previous-scroll-bar-mode
 145                                       default-frame-scroll-bars))))))
 146
 147 (defun horizontal-scroll-bars-available-p ()
 148   "Return non-nil when horizontal scroll bars are available on this system."
 149   (and (display-graphic-p)
 150        (boundp 'x-toolkit-scroll-bars)
 151        x-toolkit-scroll-bars
 152        (not (eq (window-system) 'ns))))
 153
 154 (define-minor-mode horizontal-scroll-bar-mode
 155   "Toggle horizontal scroll bars on all frames (Horizontal Scroll Bar mode).
 156 With a prefix argument ARG, enable Horizontal Scroll Bar mode if
 157 ARG is positive, and disable it otherwise.  If called from Lisp,
 158 enable the mode if ARG is omitted or nil.
 159
 160 This command applies to all frames that exist and frames to be
 161 created in the future."
 162   :init-value nil
 163   :global t
 164   :group 'frames
 165   (if (and horizontal-scroll-bar-mode
 166            (not (horizontal-scroll-bars-available-p)))
 167       (progn
 168         (setq horizontal-scroll-bar-mode nil)
 169         (message "Horizontal scroll bars are not implemented on this system"))
 170     (dolist (frame (frame-list))
 171       (set-frame-parameter
 172        frame 'horizontal-scroll-bars horizontal-scroll-bar-mode))
 173     ;; Handle `default-frame-alist' entry.
 174     (setq default-frame-alist
 175           (cons (cons 'horizontal-scroll-bars horizontal-scroll-bar-mode)
 176                 (assq-delete-all 'horizontal-scroll-bars
 177                                  default-frame-alist)))))
 178
 179 (defun toggle-scroll-bar (arg)
 180   "Toggle whether or not the selected frame has vertical scroll bars.
 181 With ARG, turn vertical scroll bars on if and only if ARG is positive.
 182 The variable `scroll-bar-mode' controls which side the scroll bars are on
 183 when they are turned on; if it is nil, they go on the left."
 184   (interactive "P")
 185   (if (null arg)
 186       (setq arg
 187             (if (cdr (assq 'vertical-scroll-bars
 188                            (frame-parameters (selected-frame))))
 189                 -1 1))
 190     (setq arg (prefix-numeric-value arg)))
 191   (modify-frame-parameters
 192    (selected-frame)
 193    (list (cons 'vertical-scroll-bars
 194                (if (> arg 0)
 195                    (or scroll-bar-mode default-frame-scroll-bars))))))
 196
 197 (defun toggle-horizontal-scroll-bar (arg)
 198   "Toggle whether or not the selected frame has horizontal scroll bars.
 199 With ARG, turn vertical scroll bars on if and only if ARG is positive."
 200   (interactive "P")
 201   (if (null arg)
 202       (setq arg
 203             (if (cdr (assq 'horizontal-scroll-bars
 204                            (frame-parameters (selected-frame))))
 205                 -1 1))
 206     (setq arg (prefix-numeric-value arg)))
 207   (modify-frame-parameters
 208    (selected-frame)
 209    (list (cons 'horizontal-scroll-bars
 210                (when (> arg 0) 'bottom)))))
 211 \f
 212 ;;;; Buffer navigation using the scroll bar.
 213
 214 ;; This was used for up-events on button 2, but no longer.
 215 (defun scroll-bar-set-window-start (event)
 216   "Set the window start according to where the scroll bar is dragged.
 217 EVENT should be a scroll bar click or drag event."
 218   (interactive "e")
 219   (let* ((end-position (event-end event))
 220          (window (nth 0 end-position))
 221          (portion-whole (nth 2 end-position)))
 222     (with-current-buffer (window-buffer window)
 223       (save-excursion
 224         (goto-char (+ (point-min)
 225                       (scroll-bar-scale portion-whole
 226                                         (- (point-max) (point-min)))))
 227         (beginning-of-line)
 228         (set-window-start window (point))))))
 229
 230 (defun scroll-bar-drag-position (portion-whole)
 231   "Calculate new window start for drag event."
 232   (save-excursion
 233     (goto-char (+ (point-min)
 234                   (scroll-bar-scale portion-whole
 235                                     (- (point-max) (point-min)))))
 236     (beginning-of-line)
 237     (point)))
 238
 239 (defun scroll-bar-maybe-set-window-start (event)
 240   "Set the window start according to where the scroll bar is dragged.
 241 Only change window start if the new start is substantially different.
 242 EVENT should be a scroll bar click or drag event."
 243   (interactive "e")
 244   (let* ((end-position (event-end event))
 245          (window (nth 0 end-position))
 246          (portion-whole (nth 2 end-position))
 247          (next-portion-whole (cons (1+ (car portion-whole))
 248                                    (cdr portion-whole)))
 249          portion-start
 250          next-portion-start
 251          (current-start (window-start window)))
 252     (with-current-buffer (window-buffer window)
 253       (setq portion-start (scroll-bar-drag-position portion-whole))
 254       (setq next-portion-start (max
 255                                 (scroll-bar-drag-position next-portion-whole)
 256                                 (1+ portion-start)))
 257       (if (or (>= current-start next-portion-start)
 258               (< current-start portion-start))
 259           (set-window-start window portion-start)
 260         ;; Always set window start, to ensure scroll bar position is updated.
 261         (set-window-start window current-start)))))
 262
 263 ;; Scroll the window to the proper position for EVENT.
 264 (defun scroll-bar-drag-1 (event)
 265   (let* ((start-position (event-start event))
 266          (window (nth 0 start-position))
 267          (portion-whole (nth 2 start-position)))
 268     (save-excursion
 269       (with-current-buffer (window-buffer window)
 270         ;; Calculate position relative to the accessible part of the buffer.
 271         (goto-char (+ (point-min)
 272                       (scroll-bar-scale portion-whole
 273                                         (- (point-max) (point-min)))))
 274         (vertical-motion 0 window)
 275         (set-window-start window (point))))))
 276
 277 (defun scroll-bar-drag (event)
 278   "Scroll the window by dragging the scroll bar slider.
 279 If you click outside the slider, the window scrolls to bring the slider there."
 280   (interactive "e")
 281   (let* (done
 282          (echo-keystrokes 0)
 283          (end-position (event-end event))
 284          (window (nth 0 end-position))
 285          (before-scroll))
 286     (with-current-buffer (window-buffer window)
 287       (setq before-scroll point-before-scroll))
 288     (save-selected-window
 289       (select-window window)
 290       (setq before-scroll
 291             (or before-scroll (point))))
 292     (scroll-bar-drag-1 event)
 293     (track-mouse
 294       (while (not done)
 295         (setq event (read-event))
 296         (if (eq (car-safe event) 'mouse-movement)
 297             (setq event (read-event)))
 298         (cond ((eq (car-safe event) 'scroll-bar-movement)
 299                (scroll-bar-drag-1 event))
 300               (t
 301                ;; Exit when we get the drag event; ignore that event.
 302                (setq done t)))))
 303     (sit-for 0)
 304     (with-current-buffer (window-buffer window)
 305       (setq point-before-scroll before-scroll))))
 306
 307 ;; Scroll the window to the proper position for EVENT.
 308 (defun scroll-bar-horizontal-drag-1 (event)
 309   (let* ((start-position (event-start event))
 310          (window (nth 0 start-position))
 311          (portion-whole (nth 2 start-position))
 312          (unit (frame-char-width (window-frame window))))
 313     (if (eq (current-bidi-paragraph-direction (window-buffer window))
 314             'left-to-right)
 315         (set-window-hscroll
 316          window (/ (+ (car portion-whole) (1- unit)) unit))
 317       (set-window-hscroll
 318        window (/ (+ (- (cdr portion-whole) (car portion-whole))
 319                     (1- unit))
 320                  unit)))))
 321
 322 (defun scroll-bar-horizontal-drag (event)
 323   "Scroll the window horizontally by dragging the scroll bar slider.
 324 If you click outside the slider, the window scrolls to bring the slider there."
 325   (interactive "e")
 326   (let* (done
 327          (echo-keystrokes 0)
 328          (end-position (event-end event))
 329          (window (nth 0 end-position))
 330          (before-scroll))
 331     (with-current-buffer (window-buffer window)
 332       (setq before-scroll point-before-scroll))
 333     (save-selected-window
 334       (select-window window)
 335       (setq before-scroll
 336             (or before-scroll (point))))
 337     (scroll-bar-horizontal-drag-1 event)
 338     (track-mouse
 339       (while (not done)
 340         (setq event (read-event))
 341         (if (eq (car-safe event) 'mouse-movement)
 342             (setq event (read-event)))
 343         (cond ((eq (car-safe event) 'scroll-bar-movement)
 344                (scroll-bar-horizontal-drag-1 event))
 345               (t
 346                ;; Exit when we get the drag event; ignore that event.
 347                (setq done t)))))
 348     (sit-for 0)
 349     (with-current-buffer (window-buffer window)
 350       (setq point-before-scroll before-scroll))))
 351
 352 (defun scroll-bar-scroll-down (event)
 353   "Scroll the window's top line down to the location of the scroll bar click.
 354 EVENT should be a scroll bar click."
 355   (interactive "e")
 356   (let* ((end-position (event-end event))
 357          (window (nth 0 end-position))
 358          (before-scroll))
 359     (with-current-buffer (window-buffer window)
 360       (setq before-scroll point-before-scroll))
 361     (unwind-protect
 362         (save-selected-window
 363           (let ((portion-whole (nth 2 end-position)))
 364             (select-window window)
 365             (setq before-scroll
 366                   (or before-scroll (point)))
 367             (scroll-down
 368              (scroll-bar-scale portion-whole (1- (window-height)))))
 369           (sit-for 0))
 370       (with-current-buffer (window-buffer window)
 371         (setq point-before-scroll before-scroll)))))
 372
 373 (defun scroll-bar-scroll-up (event)
 374   "Scroll the line next to the scroll bar click to the top of the window.
 375 EVENT should be a scroll bar click."
 376   (interactive "e")
 377   (let* ((end-position (event-end event))
 378          (window (nth 0 end-position))
 379          (before-scroll))
 380     (with-current-buffer (window-buffer window)
 381       (setq before-scroll point-before-scroll))
 382     (unwind-protect
 383         (save-selected-window
 384           (let ((portion-whole (nth 2 end-position)))
 385             (select-window window)
 386             (setq before-scroll
 387                   (or before-scroll (point)))
 388             (scroll-up
 389              (scroll-bar-scale portion-whole (1- (window-height)))))
 390           (sit-for 0))
 391       (with-current-buffer (window-buffer window)
 392         (setq point-before-scroll before-scroll)))))
 393
 394 \f
 395 ;;; Tookit scroll bars.
 396
 397 (defun scroll-bar-toolkit-scroll (event)
 398   "Handle event EVENT on vertical scroll bar."
 399   (interactive "e")
 400   (let* ((end-position (event-end event))
 401          (window (nth 0 end-position))
 402          (part (nth 4 end-position))
 403          before-scroll)
 404     (cond
 405      ((eq part 'end-scroll))
 406      (t
 407       (with-current-buffer (window-buffer window)
 408         (setq before-scroll point-before-scroll))
 409       (save-selected-window
 410         (select-window window)
 411         (setq before-scroll (or before-scroll (point)))
 412         (cond
 413          ((eq part 'above-handle)
 414           (scroll-up '-))
 415          ((eq part 'below-handle)
 416           (scroll-up nil))
 417          ((eq part 'ratio)
 418           (let* ((portion-whole (nth 2 end-position))
 419                  (lines (scroll-bar-scale portion-whole
 420                                           (1- (window-height)))))
 421             (scroll-up (cond ((not (zerop lines)) lines)
 422                              ((< (car portion-whole) 0) -1)
 423                              (t 1)))))
 424          ((eq part 'up)
 425           (scroll-up -1))
 426          ((eq part 'down)
 427           (scroll-up 1))
 428          ((eq part 'top)
 429           (set-window-start window (point-min)))
 430          ((eq part 'bottom)
 431           (goto-char (point-max))
 432           (recenter))
 433          ((eq part 'handle)
 434           (scroll-bar-drag-1 event))))
 435       (sit-for 0)
 436       (with-current-buffer (window-buffer window)
 437         (setq point-before-scroll before-scroll))))))
 438
 439 (defun scroll-bar-toolkit-horizontal-scroll (event)
 440   "Handle event EVENT on horizontal scroll bar."
 441   (interactive "e")
 442   (let* ((end-position (event-end event))
 443          (window (nth 0 end-position))
 444          (part (nth 4 end-position))
 445          (bidi-factor
 446           (if (eq (current-bidi-paragraph-direction (window-buffer window))
 447                   'left-to-right)
 448               1
 449             -1))
 450          before-scroll)
 451     (cond
 452      ((eq part 'end-scroll))
 453      (t
 454       (with-current-buffer (window-buffer window)
 455         (setq before-scroll point-before-scroll))
 456       (save-selected-window
 457         (select-window window)
 458         (setq before-scroll (or before-scroll (point)))
 459         (cond
 460          ((eq part 'before-handle)
 461           (scroll-right (* bidi-factor 4)))
 462          ((eq part 'after-handle)
 463           (scroll-left (* bidi-factor 4)))
 464          ((eq part 'ratio)
 465           (let* ((portion-whole (nth 2 end-position))
 466                  (columns (scroll-bar-scale portion-whole
 467                                             (1- (window-width)))))
 468             (scroll-right
 469              (* (cond
 470                  ((not (zerop columns))
 471                   columns)
 472                  ((< (car portion-whole) 0) -1)
 473                  (t 1))
 474                 bidi-factor))))
 475          ((eq part 'left)
 476           (scroll-right (* bidi-factor 1)))
 477          ((eq part 'right)
 478           (scroll-left (* bidi-factor 1)))
 479          ((eq part 'leftmost)
 480           (goto-char (if (eq bidi-factor 1)
 481                          (line-beginning-position)
 482                        (line-end-position))))
 483          ((eq part 'rightmost)
 484           (goto-char (if (eq bidi-factor 1)
 485                          (line-end-position)
 486                        (line-beginning-position))))
 487          ((eq part 'horizontal-handle)
 488           (scroll-bar-horizontal-drag-1 event))))
 489       (sit-for 0)
 490       (with-current-buffer (window-buffer window)
 491         (setq point-before-scroll before-scroll))))))
 492 \f
 493 ;;;; Bindings.
 494
 495 ;; For now, we'll set things up to work like xterm.
 496 (cond ((and (boundp 'x-toolkit-scroll-bars) x-toolkit-scroll-bars)
 497        (global-set-key [vertical-scroll-bar mouse-1]
 498                        'scroll-bar-toolkit-scroll)
 499        (global-set-key [horizontal-scroll-bar mouse-1]
 500                        'scroll-bar-toolkit-horizontal-scroll))
 501       (t
 502        (global-set-key [vertical-scroll-bar mouse-1]
 503                        'scroll-bar-scroll-up)
 504        (global-set-key [vertical-scroll-bar drag-mouse-1]
 505                        'scroll-bar-scroll-up)
 506        (global-set-key [vertical-scroll-bar down-mouse-2]
 507                        'scroll-bar-drag)
 508        (global-set-key [vertical-scroll-bar mouse-3]
 509                        'scroll-bar-scroll-down)
 510        (global-set-key [vertical-scroll-bar drag-mouse-3]
 511                        'scroll-bar-scroll-down)))
 512
 513 \f
 514 (provide 'scroll-bar)
 515
 516 ;;; scroll-bar.el ends here