lisp/hl-line.el

   1 ;;; hl-line.el --- highlight the current line
   2
   3 ;; Copyright (C) 1998, 2000, 2001 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 minor mode (toggled by M-x hl-line-mode) and a global minor
  29 ;; mode (toggled by M-x global-hl-line-mode) to highlight, on a
  30 ;; suitable terminal, the line in the current window on which point is
  31 ;; (except in a minibuffer window).  Done to satisfy a request for a
  32 ;; feature of Lesser Editors.
  33
  34 ;; You probably don't really want this; if the cursor is difficult to
  35 ;; spot, try changing its colour, relying on `blink-cursor-mode' or
  36 ;; both.  The hookery used might affect response noticeably on a slow
  37 ;; machine.  It may be useful in "non-text" buffers such as Gnus or
  38 ;; PCL-CVS though.
  39
  40 ;; An overlay is used, active only on the selected window.  Hooks are
  41 ;; added to `pre-command-hook' and `post-command-hook' to activate and
  42 ;; deactivate (by deleting) the overlay.  `hl-line-unhighlight', on
  43 ;; `pre-command-hook', deactivates it unconditionally in case the
  44 ;; command changes the selected window.  (It does so rather than
  45 ;; keeping track of changes in the selected window).
  46 ;; `hl-line-highlight', on `post-command-hook', activates it again
  47 ;; across the window width.
  48
  49 ;;; Code:
  50
  51 (defgroup hl-line nil
  52   "Highlight the current line."
  53   :version "21.1"
  54   :group 'editing)
  55
  56 (defcustom hl-line-face 'highlight
  57   "Face with which to highlight the current line."
  58   :type 'face
  59   :group 'hl-line)
  60
  61 (defvar hl-line-overlay nil)
  62
  63 ;;;###autoload
  64 (define-minor-mode hl-line-mode
  65   "Minor mode to highlight the line about point in the current window.
  66 With ARG, turn Hl-Line mode on if ARG is positive, off otherwise.
  67 Uses functions `hl-line-unhighlight' and `hl-line-highlight' on
  68 `pre-command-hook' and `post-command-hook'."
  69   nil nil nil
  70   (if hl-line-mode
  71       (progn
  72         (add-hook 'pre-command-hook #'hl-line-unhighlight nil t)
  73         (add-hook 'post-command-hook #'hl-line-highlight nil t))
  74     (hl-line-unhighlight)
  75     (remove-hook 'pre-command-hook #'hl-line-unhighlight t)
  76     (remove-hook 'post-command-hook #'hl-line-highlight t)))
  77
  78 ;;;###autoload
  79 (easy-mmode-define-global-mode
  80  global-hl-line-mode hl-line-mode (lambda () (hl-line-mode 1))
  81  :group 'hl-line)
  82
  83 (defun hl-line-highlight ()
  84   "Active the Hl-Line overlay on the current line in the current window.
  85 \(Unless it's a minibuffer window.)"
  86   (when hl-line-mode            ; Might be changed outside the mode function.
  87     (unless (window-minibuffer-p (selected-window)) ; silly in minibuffer
  88       (unless hl-line-overlay
  89         (setq hl-line-overlay (make-overlay 1 1)) ; to be moved
  90         (overlay-put hl-line-overlay 'face hl-line-face))
  91       (overlay-put hl-line-overlay 'window (selected-window))
  92       (move-overlay hl-line-overlay
  93                     (line-beginning-position) (1+ (line-end-position))
  94                     (current-buffer)))))
  95
  96 (defun hl-line-unhighlight ()
  97   "Deactivate the Hl-Line overlay on the current line in the current window."
  98   (if hl-line-overlay
  99       (delete-overlay hl-line-overlay)))
 100
 101 (provide 'hl-line)
 102
 103 ;;; hl-line.el ends here