Initial revision

lisp/hl-line.el

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+;;; hl-line.el --- highlight the current line
+
+;; Copyright (C) 1998 Free Software Foundation, Inc.
+
+;; Author:  Dave Love <fx@gnu.org>
+;; Created: 1998-09-13
+;; Keywords: faces, frames
+
+;; Hl-Line mode is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation; either version 2, or (at your option)
+;; any later version.
+
+;; Hl-Line mode is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs; see the file COPYING.  If not, write to the
+;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+;; Boston, MA 02111-1307, USA.
+
+;;; Commentary:
+
+;; Provides a global minor mode (toggled by M-x hl-line-mode) to
+;; highlight, in a windowing system, the line on which point is
+;; (except in a minibuffer window) to satisfy a request for a feature
+;; of Lesser Editors.
+
+;; You probably don't really want this; if the cursor is difficult to
+;; spot, try changing its colour or using a cursor blinking
+;; <URL:http://www.wonderworks.com/download/blinking-cursor.el.gz> or
+;; jiggling <URL:http://www.eskimo.com/%7Eseldon> package.  (Cursor
+;; blinking will be built in to Emacs 21.)  The hookery involved here
+;; might slow Emacs noticeably on a slow machine.
+
+;; An overlay is used, active only on the selected window.  Hooks are
+;; added to `pre-command-hook' and `post-command-hook' to activate and
+;; deactivate (by deleting) the overlay.  `hl-line-unhighlight', on
+;; `pre-command-hook', deactivates it unconditionally in case the
+;; command changes the selected window.  (It does so rather than
+;; keeping track of changes in the selected window).
+;; `hl-line-highlight', on `post-command-hook', activates it again
+;; across the window width.
+
+;;; Code:
+
+(defgroup hl-line nil
+  "Highliight the current line."
+  :group 'editing)
+
+(defcustom hl-line-mode nil
+  "Non-nil if Hl-Line mode is enabled."
+  :set (lambda (symbol value)
+	 (hl-line-mode (or value 0)))
+  :initialize 'custom-initialize-default
+  :type 'boolean
+  :group 'hl-line
+  :require 'hl-line)
+
+(defcustom hl-line-face 'highlight
+  "Face with which to highlight the current line."
+  :type 'face
+  :group 'hl-line)
+
+(defvar hl-line-overlay nil)
+(make-variable-buffer-local 'hl-line-overlay)
+
+(defun hl-line-highlight ()
+  "Active the Hl-Line overlay on the current line in the current window.
+\(Unless it's a minibuffer window.)"
+  (unless (window-minibuffer-p (selected-window)) ; silly in minibuffer
+    (unless hl-line-overlay		; new overlay for this buffer
+      (setq hl-line-overlay (make-overlay 1 1))	; to be moved
+      (overlay-put hl-line-overlay 'face hl-line-face))
+    (overlay-put hl-line-overlay 'window (selected-window))
+    (move-overlay hl-line-overlay
+		  (line-beginning-position) (1+ (line-end-position)))))
+
+(defun hl-line-unhighlight ()
+  "Deactivate the Hl-Line overlay on the current line in the current window."
+  (if hl-line-overlay
+      (delete-overlay hl-line-overlay)))
+
+(defun hl-line-mode (&optional arg)
+  "Global minor mode to highlight the line about point.
+
+With ARG, turn Hl-Line mode on if ARG is positive, off otherwise.
+Only useful with a windowing system.
+Uses functions `hl-line-unhighlight' and `hl-line-highlight' on
+`pre-command-hook' and `post-command-hook'."
+  (interactive "P")
+  (setq hl-line-mode (if (null arg)
+			 (not hl-line-mode)
+		       (> (prefix-numeric-value arg) 0)))
+  (cond (hl-line-mode
+	 (add-hook 'pre-command-hook #'hl-line-unhighlight)
+	 (add-hook 'post-command-hook #'hl-line-highlight))
+	(t
+	 (hl-line-unhighlight)
+	 (remove-hook 'pre-command-hook #'hl-line-unhighlight)
+	 (remove-hook 'post-command-hook #'hl-line-highlight)))
+  (if (interactive-p)
+      (message "Hl-Line mode %sabled" (if hl-line-mode "en" "dis"))))
+
+(provide 'hl-line)
+
+;;; hl-line.el ends here