lisp/hl-line.el

   1 ;;; hl-line.el --- highlight the current line
   2
   3 ;; Copyright (C) 1998 Free Software Foundation, Inc.
   4
   5 ;; Author:  Dave Love <fx@gnu.org>
   6 ;; Created: 1998-09-13
   7 ;; Keywords: faces, frames
   8
   9 ;; Hl-Line mode is free software; you can redistribute it and/or modify
  10 ;; it under the terms of the GNU General Public License as published by
  11 ;; the Free Software Foundation; either version 2, or (at your option)
  12 ;; any later version.
  13
  14 ;; Hl-Line mode is distributed in the hope that it will be useful,
  15 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 ;; GNU General Public License for more details.
  18
  19 ;; You should have received a copy of the GNU General Public License
  20 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  21 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  22 ;; Boston, MA 02111-1307, USA.
  23
  24 ;;; Commentary:
  25
  26 ;; Provides a global minor mode (toggled by M-x hl-line-mode) to
  27 ;; highlight, in a windowing system, the line on which point is
  28 ;; (except in a minibuffer window) to satisfy a request for a feature
  29 ;; of Lesser Editors.
  30
  31 ;; You probably don't really want this; if the cursor is difficult to
  32 ;; spot, try changing its colour or using a cursor blinking
  33 ;; <URL:http://www.wonderworks.com/download/blinking-cursor.el.gz> or
  34 ;; jiggling <URL:http://www.eskimo.com/%7Eseldon> package.  (Cursor
  35 ;; blinking will be built in to Emacs 21.)  The hookery involved here
  36 ;; might slow Emacs noticeably on a slow machine.
  37
  38 ;; An overlay is used, active only on the selected window.  Hooks are
  39 ;; added to `pre-command-hook' and `post-command-hook' to activate and
  40 ;; deactivate (by deleting) the overlay.  `hl-line-unhighlight', on
  41 ;; `pre-command-hook', deactivates it unconditionally in case the
  42 ;; command changes the selected window.  (It does so rather than
  43 ;; keeping track of changes in the selected window).
  44 ;; `hl-line-highlight', on `post-command-hook', activates it again
  45 ;; across the window width.
  46
  47 ;;; Code:
  48
  49 (defgroup hl-line nil
  50   "Highliight the current line."
  51   :version "21.1"
  52   :group 'editing)
  53
  54 ;;;###autoload
  55 (defcustom hl-line-mode nil
  56   "Non-nil if Hl-Line mode is enabled."
  57   :set (lambda (symbol value)
  58          (hl-line-mode (or value 0)))
  59   :initialize 'custom-initialize-default
  60   :type 'boolean
  61   :group 'hl-line
  62   :require 'hl-line)
  63
  64 (defcustom hl-line-face 'highlight
  65   "Face with which to highlight the current line."
  66   :type 'face
  67   :group 'hl-line)
  68
  69 (defvar hl-line-overlay nil)
  70 (make-variable-buffer-local 'hl-line-overlay)
  71
  72 (defun hl-line-highlight ()
  73   "Active the Hl-Line overlay on the current line in the current window.
  74 \(Unless it's a minibuffer window.)"
  75   (unless (window-minibuffer-p (selected-window)) ; silly in minibuffer
  76     (unless hl-line-overlay             ; new overlay for this buffer
  77       (setq hl-line-overlay (make-overlay 1 1)) ; to be moved
  78       (overlay-put hl-line-overlay 'face hl-line-face))
  79     (overlay-put hl-line-overlay 'window (selected-window))
  80     (move-overlay hl-line-overlay
  81                   (line-beginning-position) (1+ (line-end-position)))))
  82
  83 (defun hl-line-unhighlight ()
  84   "Deactivate the Hl-Line overlay on the current line in the current window."
  85   (if hl-line-overlay
  86       (delete-overlay hl-line-overlay)))
  87
  88 ;;;###autoload
  89 (defun hl-line-mode (&optional arg)
  90   "Global minor mode to highlight the line about point.
  91
  92 With ARG, turn Hl-Line mode on if ARG is positive, off otherwise.
  93 Only useful with a windowing system.
  94 Uses functions `hl-line-unhighlight' and `hl-line-highlight' on
  95 `pre-command-hook' and `post-command-hook'."
  96   (interactive "P")
  97   (setq hl-line-mode (if (null arg)
  98                          (not hl-line-mode)
  99                        (> (prefix-numeric-value arg) 0)))
 100   (cond (hl-line-mode
 101          (add-hook 'pre-command-hook #'hl-line-unhighlight)
 102          (add-hook 'post-command-hook #'hl-line-highlight))
 103         (t
 104          (hl-line-unhighlight)
 105          (remove-hook 'pre-command-hook #'hl-line-unhighlight)
 106          (remove-hook 'post-command-hook #'hl-line-highlight)))
 107   (if (interactive-p)
 108       (message "Hl-Line mode %sabled" (if hl-line-mode "en" "dis"))))
 109
 110 (provide 'hl-line)
 111
 112 ;;; hl-line.el ends here