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;;; hl-line.el --- highlight the current line
;; Copyright (C) 1998, 2000 Free Software Foundation, Inc.
;; Author: Dave Love <fx@gnu.org>
;; Created: 1998-09-13
;; Keywords: faces, frames, emulation
;; This file is part of GNU Emacs.
;; GNU Emacs 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.
;; GNU Emacs 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, on a suitable terminal, the line in the current window
;; on which point is (except in a minibuffer window). Done 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, relying on `blink-cursor-mode' or
;; both. The hookery used might affect response 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.
;; You could make variable `hl-line-mode' buffer-local to avoid
;; highlighting specific buffers.
;;; Code:
(defgroup hl-line nil
"Highliight the current line."
:version "21.1"
:group 'editing)
(defcustom hl-line-face 'highlight
"Face with which to highlight the current line."
:type 'face
:group 'hl-line)
(defvar hl-line-overlay nil)
(defun hl-line-highlight ()
"Active the Hl-Line overlay on the current line in the current window.
\(Unless it's a minibuffer window.)"
(when hl-line-mode ; Could be made buffer-local.
(unless (window-minibuffer-p (selected-window)) ; silly in minibuffer
(unless hl-line-overlay
(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))
(current-buffer)))))
(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)))
;;;###autoload
(define-minor-mode hl-line-mode
"Global minor mode to highlight the line about point in the current window.
With ARG, turn Hl-Line mode on if ARG is positive, off otherwise.
Uses functions `hl-line-unhighlight' and `hl-line-highlight' on
`pre-command-hook' and `post-command-hook'."
nil nil nil :global t
(if hl-line-mode
(progn
(add-hook 'pre-command-hook #'hl-line-unhighlight)
(add-hook 'post-command-hook #'hl-line-highlight))
(hl-line-unhighlight)
(remove-hook 'pre-command-hook #'hl-line-unhighlight)
(remove-hook 'post-command-hook #'hl-line-highlight)))
(provide 'hl-line)
;;; hl-line.el ends here
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