lisp/hl-line.el

   1 ;;; hl-line.el --- highlight the current line
   2
   3 ;; Copyright (C) 1998, 2000, 2001, 2003 Free Software Foundation, Inc.
   4
   5 ;; Author:  Dave Love <fx@gnu.org>
   6 ;; Created: 1998-09-13
   7 ;; Keywords: faces, frames, emulation
   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 2, 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., 59 Temple Place - Suite 330,
  24 ;; Boston, MA 02111-1307, USA.
  25
  26 ;;; Commentary:
  27
  28 ;; Provides a buffer-local minor mode (toggled by M-x hl-line-mode)
  29 ;; and a global minor mode (toggled by M-x global-hl-line-mode) to
  30 ;; highlight, on a suitable terminal, the line on which point is.  The
  31 ;; global mode highlights the current line in the selected window only
  32 ;; (except when the minibuffer window is selected).  This was
  33 ;; implemented to satisfy a request for a feature of Lesser Editors.
  34 ;; The local mode is sticky: it highlights the line about the buffer's
  35 ;; point even if the buffer's window is not selected.  Caveat: the
  36 ;; buffer's point might be different from the point of a non-selected
  37 ;; window.  Set the variable `hl-line-sticky-flag' to nil to make the
  38 ;; local mode behave like the global mode.
  39
  40 ;; You probably don't really want to use the global mode; if the
  41 ;; cursor is difficult to spot, try changing its colour, relying on
  42 ;; `blink-cursor-mode' or both.  The hookery used might affect
  43 ;; response noticeably on a slow machine.  The local mode may be
  44 ;; useful in non-editing buffers such as Gnus or PCL-CVS though.
  45
  46 ;; An overlay is used.  In the non-sticky cases, this overlay is
  47 ;; active only on the selected window.  A hook is added to
  48 ;; `post-command-hook' to activate the overlay and move it to the line
  49 ;; about point.  To get the non-sticky behavior, `hl-line-unhighlight'
  50 ;; is added to `pre-command-hook' as well.  This function deactivates
  51 ;; the overlay unconditionally in case the command changes the
  52 ;; selected window.  (It does so rather than keeping track of changes
  53 ;; in the selected window).
  54
  55 ;; You could make variable `global-hl-line-mode' buffer-local and set
  56 ;; it to nil to avoid highlighting specific buffers, when the global
  57 ;; mode is used.
  58
  59 ;;; Code:
  60
  61 (defgroup hl-line nil
  62   "Highlight the current line."
  63   :version "21.1"
  64   :group 'editing)
  65
  66 (defcustom hl-line-face 'highlight
  67   "Face with which to highlight the current line."
  68   :type 'face
  69   :group 'hl-line)
  70
  71 (defcustom hl-line-sticky-flag t
  72   "*Non-nil means highlight the current line in all windows.
  73 Otherwise Hl-Line mode will highlight only in the selected
  74 window.  Setting this variable takes effect the next time you use
  75 the command `hl-line-mode' to turn Hl-Line mode on."
  76   :type 'boolean
  77   :version "21.4"
  78   :group 'hl-line)
  79
  80 (defvar hl-line-overlay nil
  81   "Overlay used by Hl-Line mode to highlight the current line.")
  82 (make-variable-buffer-local 'hl-line-overlay)
  83
  84 (defvar global-hl-line-overlay nil
  85   "Overlay used by Global-Hl-Line mode to highlight the current line.")
  86
  87 ;;;###autoload
  88 (define-minor-mode hl-line-mode
  89   "Buffer-local minor mode to highlight the line about point.
  90 With ARG, turn Hl-Line mode on if ARG is positive, off otherwise.
  91
  92 If `hl-line-sticky-flag' is non-nil, Hl-Line mode highlights the
  93 line about the buffer's point in all windows.  Caveat: the
  94 buffer's point might be different from the point of a
  95 non-selected window.  Hl-Line mode uses the function
  96 `hl-line-highlight' on `post-command-hook' in this case.
  97
  98 When `hl-line-sticky-flag' is nil, Hl-Line mode highlights the
  99 line about point in the selected window only.  In this case, it
 100 uses the function `hl-line-unhighlight' on `pre-command-hook' in
 101 addition to `hl-line-highlight' on `post-command-hook'."
 102   nil nil nil
 103   (if hl-line-mode
 104       (progn
 105         ;; In case `kill-all-local-variables' is called.
 106         (add-hook 'change-major-mode-hook #'hl-line-unhighlight nil t)
 107         (if hl-line-sticky-flag
 108             (remove-hook 'pre-command-hook #'hl-line-unhighlight t)
 109           (add-hook 'pre-command-hook #'hl-line-unhighlight nil t))
 110         (hl-line-highlight)
 111         (add-hook 'post-command-hook #'hl-line-highlight nil t))
 112     (remove-hook 'post-command-hook #'hl-line-highlight t)
 113     (hl-line-unhighlight)
 114     (remove-hook 'change-major-mode-hook #'hl-line-unhighlight t)
 115     (remove-hook 'pre-command-hook #'hl-line-unhighlight t)))
 116
 117 (defun hl-line-highlight ()
 118   "Active the Hl-Line overlay on the current line."
 119   (if hl-line-mode      ; Might be changed outside the mode function.
 120       (progn
 121         (unless hl-line-overlay
 122           (setq hl-line-overlay (make-overlay 1 1)) ; to be moved
 123           (overlay-put hl-line-overlay 'face hl-line-face))
 124         (overlay-put hl-line-overlay
 125                      'window (unless hl-line-sticky-flag (selected-window)))
 126         (move-overlay hl-line-overlay
 127                       (line-beginning-position) (line-beginning-position 2)))
 128     (hl-line-unhighlight)))
 129
 130 (defun hl-line-unhighlight ()
 131   "Deactivate the Hl-Line overlay on the current line."
 132   (if hl-line-overlay
 133       (delete-overlay hl-line-overlay)))
 134
 135 ;;;###autoload
 136 (define-minor-mode global-hl-line-mode
 137   "Global minor mode to highlight the line about point in the current window.
 138 With ARG, turn Global-Hl-Line mode on if ARG is positive, off otherwise.
 139
 140 Global-Hl-Line mode uses the functions `global-hl-line-unhighlight' and
 141 `global-hl-line-highlight' on `pre-command-hook' and `post-command-hook'."
 142   :global t
 143   :group 'hl-line
 144   (if global-hl-line-mode
 145       (progn
 146         (add-hook 'pre-command-hook #'global-hl-line-unhighlight)
 147         (add-hook 'post-command-hook #'global-hl-line-highlight))
 148     (global-hl-line-unhighlight)
 149     (remove-hook 'pre-command-hook #'global-hl-line-unhighlight)
 150     (remove-hook 'post-command-hook #'global-hl-line-highlight)))
 151
 152 (defun global-hl-line-highlight ()
 153   "Active the Global-Hl-Line overlay on the current line in the current window."
 154   (when global-hl-line-mode     ; Might be changed outside the mode function.
 155     (unless (window-minibuffer-p (selected-window))
 156       (unless global-hl-line-overlay
 157         (setq global-hl-line-overlay (make-overlay 1 1)) ; to be moved
 158         (overlay-put global-hl-line-overlay 'face hl-line-face))
 159       (overlay-put global-hl-line-overlay 'window (selected-window))
 160       (move-overlay global-hl-line-overlay
 161                     (line-beginning-position) (line-beginning-position 2)))))
 162
 163 (defun global-hl-line-unhighlight ()
 164   "Deactivate the Global-Hl-Line overlay on the current line."
 165   (if global-hl-line-overlay
 166       (delete-overlay global-hl-line-overlay)))
 167
 168 (provide 'hl-line)
 169
 170 ;;; hl-line.el ends here