lisp/reveal.el

   1 ;;; reveal.el --- Automatically reveal hidden text at point -*- lexical-binding: t -*-
   2
   3 ;; Copyright (C) 2000-2017 Free Software Foundation, Inc.
   4
   5 ;; Author: Stefan Monnier <monnier@iro.umontreal.ca>
   6 ;; Keywords: outlines
   7
   8 ;; This file is part of GNU Emacs.
   9
  10 ;; GNU Emacs is free software: you can redistribute it and/or modify
  11 ;; it under the terms of the GNU General Public License as published by
  12 ;; the Free Software Foundation, either version 3 of the License, or
  13 ;; (at your option) any later version.
  14
  15 ;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;; GNU General Public License for more details.
  19
  20 ;; You should have received a copy of the GNU General Public License
  21 ;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
  22
  23 ;;; Commentary:
  24
  25 ;; Reveal mode is a minor mode that makes sure that text around point
  26 ;; is always visible.  When point enters a region of hidden text,
  27 ;; `reveal-mode' temporarily makes it visible.
  28 ;;
  29 ;; This is normally used in conjunction with `outline-minor-mode',
  30 ;; `hs-minor-mode', `hide-ifdef-mode', ...
  31 ;;
  32 ;; It only works with packages that hide text using overlays.
  33 ;; Packages can provide special support for it by placing
  34 ;; a function in the `reveal-toggle-invisible' property on the symbol
  35 ;; used as the value of the `invisible' overlay property.
  36 ;; The function is called right after revealing (or re-hiding) the
  37 ;; text with two arguments: the overlay and a boolean that's non-nil
  38 ;; if we have just revealed the text.  When revealing, that function
  39 ;; may re-hide some of the text.
  40
  41 ;;; Todo:
  42
  43 ;; - find other hysteresis features.
  44 ;; - don't hide after a scroll command
  45 ;; - delay hiding by a couple seconds (i.e. hide in the background)
  46
  47 ;;; Code:
  48
  49 (defgroup reveal nil
  50   "Reveal hidden text on the fly."
  51   :group 'convenience)
  52
  53 (defcustom reveal-around-mark t
  54   "Reveal text around the mark, if active."
  55   :type 'boolean
  56   :group 'reveal)
  57
  58 (defvar reveal-open-spots nil
  59   "List of spots in the buffer which are open.
  60 Each element has the form (WINDOW . OVERLAY).")
  61 (make-variable-buffer-local 'reveal-open-spots)
  62
  63 (defvar reveal-last-tick nil)
  64 (make-variable-buffer-local 'reveal-last-tick)
  65
  66 ;; Actual code
  67
  68 (defun reveal-post-command ()
  69   ;; Refresh the spots that might have changed.
  70   ;; `Refreshing' here means to try and re-hide the corresponding text.
  71   ;; We don't refresh everything correctly:
  72   ;; - we only refresh spots in the current window.
  73   ;; FIXME: do we actually know that (current-buffer) = (window-buffer) ?
  74   (with-local-quit
  75     (with-demoted-errors "Reveal: %s"
  76       (let ((old-ols
  77              (delq nil
  78                    (mapcar
  79                     (lambda (x)
  80                       ;; We refresh any spot in the current window as well
  81                       ;; as any spots associated with a dead window or
  82                       ;; a window which does not show this buffer any more.
  83                       (cond
  84                        ((eq (car x) (selected-window)) (cdr x))
  85                        ((not (and (window-live-p (car x))
  86                                   (eq (window-buffer (car x))
  87                                       (current-buffer))))
  88                         ;; Adopt this since it's owned by a window that's
  89                         ;; either not live or at least not showing this
  90                         ;; buffer any more.
  91                         (setcar x (selected-window))
  92                         (cdr x))))
  93                     reveal-open-spots))))
  94         (setq old-ols (reveal-open-new-overlays old-ols))
  95         (reveal-close-old-overlays old-ols)))))
  96
  97 (defun reveal-open-new-overlays (old-ols)
  98   (let ((repeat t))
  99     (while repeat
 100       (setq repeat nil)
 101       (dolist (ol (nconc (when (and reveal-around-mark mark-active)
 102                            (overlays-at (mark)))
 103                          (overlays-at (point))))
 104         (setq old-ols (delq ol old-ols))
 105         (when (overlay-start ol)        ;Check it's still live.
 106           (let ((inv (overlay-get ol 'invisible)) open)
 107             (when (and inv
 108                        ;; There's an `invisible' property.  Make sure it's
 109                        ;; actually invisible, and ellipsized.
 110                        (and (consp buffer-invisibility-spec)
 111                             (cdr (assq inv buffer-invisibility-spec)))
 112                        (or (setq open
 113                                  (or (overlay-get ol 'reveal-toggle-invisible)
 114                                      (and (symbolp inv)
 115                                           (get inv 'reveal-toggle-invisible))
 116                                      (overlay-get ol 'isearch-open-invisible-temporary)))
 117                            (overlay-get ol 'isearch-open-invisible)
 118                            (and (consp buffer-invisibility-spec)
 119                                 (cdr (assq inv buffer-invisibility-spec))))
 120                        (overlay-put ol 'reveal-invisible inv))
 121               (push (cons (selected-window) ol) reveal-open-spots)
 122               (if (null open)
 123                   (overlay-put ol 'invisible nil)
 124                 ;; Use the provided opening function and repeat (since the
 125                 ;; opening function might have hidden a subpart around point
 126                 ;; or moved/killed some of the overlays).
 127                 (setq repeat t)
 128                 (condition-case err
 129                     (funcall open ol nil)
 130                   (error (message "!!Reveal-show (funcall %s %s nil): %s !!"
 131                                   open ol err)
 132                          ;; Let's default to a meaningful behavior to avoid
 133                          ;; getting stuck in an infinite loop.
 134                          (setq repeat nil)
 135                          (overlay-put ol 'invisible nil))))))))))
 136   old-ols)
 137
 138 (defun reveal-close-old-overlays (old-ols)
 139   (if (or track-mouse                   ;Don't close in the middle of a click.
 140           (not (eq reveal-last-tick
 141                    (setq reveal-last-tick (buffer-modified-tick)))))
 142       ;; The buffer was modified since last command: let's refrain from
 143       ;; closing any overlay because it tends to behave poorly when
 144       ;; inserting text at the end of an overlay (basically the overlay
 145       ;; should be rear-advance when it's open, but things like
 146       ;; outline-minor-mode make it non-rear-advance because it's
 147       ;; a better choice when it's closed).
 148       nil
 149     ;; The last command was only a point motion or some such
 150     ;; non-buffer-modifying command.  Let's close whatever can be closed.
 151     (dolist (ol old-ols)
 152       (if (and (overlay-start ol)       ;Check it's still live.
 153                (>= (point) (save-excursion
 154                              (goto-char (overlay-start ol))
 155                              (line-beginning-position 1)))
 156                (<= (point) (save-excursion
 157                              (goto-char (overlay-end ol))
 158                              (line-beginning-position 2)))
 159                ;; If the application has moved the overlay to some other
 160                ;; buffer, we'd better reset the buffer to its
 161                ;; original state.
 162                (eq (current-buffer) (overlay-buffer ol)))
 163           ;; Still near the overlay: keep it open.
 164           nil
 165         ;; Really close it.
 166         (let* ((inv (overlay-get ol 'reveal-invisible))
 167                (open (or (overlay-get ol 'reveal-toggle-invisible)
 168                          (get inv 'reveal-toggle-invisible)
 169                          (overlay-get ol 'isearch-open-invisible-temporary))))
 170           (if (and (overlay-start ol)   ;Check it's still live.
 171                    open)
 172               (condition-case err
 173                   (funcall open ol t)
 174                 (error (message "!!Reveal-hide (funcall %s %s t): %s !!"
 175                                 open ol err)))
 176             (overlay-put ol 'invisible inv))
 177           ;; Remove the overlay from the list of open spots.
 178           (overlay-put ol 'reveal-invisible nil)
 179           (setq reveal-open-spots
 180                 (delq (rassoc ol reveal-open-spots)
 181                       reveal-open-spots)))))))
 182
 183 (defvar reveal-mode-map
 184   (let ((map (make-sparse-keymap)))
 185     ;; Override the default move-beginning-of-line and move-end-of-line
 186     ;; which skips valuable invisible text.
 187     (define-key map [remap move-beginning-of-line] 'beginning-of-line)
 188     (define-key map [remap move-end-of-line] 'end-of-line)
 189     map))
 190
 191 ;;;###autoload
 192 (define-minor-mode reveal-mode
 193   "Toggle uncloaking of invisible text near point (Reveal mode).
 194 With a prefix argument ARG, enable Reveal mode if ARG is
 195 positive, and disable it otherwise.  If called from Lisp, enable
 196 Reveal mode if ARG is omitted or nil.
 197
 198 Reveal mode is a buffer-local minor mode.  When enabled, it
 199 reveals invisible text around point."
 200   :group 'reveal
 201   :lighter (global-reveal-mode nil " Reveal")
 202   :keymap reveal-mode-map
 203   (if reveal-mode
 204       (progn
 205         (set (make-local-variable 'search-invisible) t)
 206         (add-hook 'post-command-hook 'reveal-post-command nil t))
 207     (kill-local-variable 'search-invisible)
 208     (remove-hook 'post-command-hook 'reveal-post-command t)))
 209
 210 ;;;###autoload
 211 (define-minor-mode global-reveal-mode
 212   "Toggle Reveal mode in all buffers (Global Reveal mode).
 213 Reveal mode renders invisible text around point visible again.
 214
 215 With a prefix argument ARG, enable Global Reveal mode if ARG is
 216 positive, and disable it otherwise.  If called from Lisp, enable
 217 the mode if ARG is omitted or nil."
 218   :global t :group 'reveal
 219   (setq-default reveal-mode global-reveal-mode)
 220   (if global-reveal-mode
 221       (progn
 222         (setq search-invisible t)
 223         (add-hook 'post-command-hook 'reveal-post-command))
 224     (setq search-invisible 'open)       ;FIXME
 225     (remove-hook 'post-command-hook 'reveal-post-command)))
 226
 227 (provide 'reveal)
 228
 229 ;;; reveal.el ends here