;;; gutter.el --- Gutter manipulation for XEmacs.

;; Copyright (C) 1999 Free Software Foundation, Inc.
;; Copyright (C) 1999, 2000 Andy Piper.

;; Maintainer: XEmacs Development Team
;; Keywords: frames, extensions, internal, dumped

;; This file is part of XEmacs.

;; XEmacs 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.

;; XEmacs 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 Xmacs; see the file COPYING.  If not, write to the
;; Free Software Foundation, 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;; Some of this is taken from the buffer-menu stuff in menubar-items.el
;; and the custom specs in toolbar.el.

(defgroup gutter nil
  "Input from the gutters."
  :group 'environment)

;; Although these customizations appear bogus, they are neccessary in
;; order to be able to save options through the options menu.
(defcustom default-gutter-position
  (default-gutter-position)
  "The location of the default gutter. It can be 'top, 'bottom, 'left or
'right. This option should be customized through the options menu.
To set the gutter position explicitly use `set-default-gutter-position'"
  :group 'gutter
  :type '(choice (const :tag "top" top)
		 (const :tag "bottom" bottom)
		 (const :tag "left" left)
		 (const :tag "right" right))
  :set #'(lambda (var val)
	   (set-default-gutter-position val)
	   (setq default-gutter-position val)))

;;; Gutter helper functions

;; called by Fset_default_gutter_position()
(defvar default-gutter-position-changed-hook nil
  "Function or functions to be called when the gutter position is changed.
The value of this variable may be buffer-local.")

;; called by set-gutter-element-visible-p
(defvar gutter-element-visibility-changed-hook nil
  "Function or functions to be called when the visibility of an
element in the gutter changes.  The value of this variable may be
buffer-local. The gutter element symbol is passed as an argument to
the hook, as is the visibility flag.")

(defun set-gutter-element (gutter-specifier prop val &optional locale tag-set)
  "Set GUTTER-SPECIFIER gutter element PROP to VAL in optional LOCALE.
This is a convenience function for setting gutter elements.
VAL in general must be a string. If VAL is a glyph then a string will be
created to put the glyph into."
  (let ((spec val))
    (when (glyphp val)
      (setq spec (copy-sequence "\n"))
      (set-extent-begin-glyph (make-extent 0 1 spec) val))
    (map-extents #'(lambda (extent arg) 
		     (set-extent-property extent 'duplicable t)) spec)
    (modify-specifier-instances gutter-specifier #'plist-put (list prop spec)
				'force nil locale tag-set)))

(defun remove-gutter-element (gutter-specifier prop &optional locale tag-set)
  "Remove gutter element PROP from GUTTER-SPECIFIER in optional LOCALE.
This is a convenience function for removing gutter elements."
  (modify-specifier-instances gutter-specifier #'plist-remprop (list prop)
                              'force nil locale tag-set))

(defun set-gutter-element-visible-p (gutter-visible-specifier-p
				     prop &optional visible-p
				     locale tag-set)
  "Change the visibility of gutter elements.
Set the visibility of element PROP to VISIBLE-P for
GUTTER-SPECIFIER-VISIBLE-P in optional LOCALE.  
This is a convenience function for hiding and showing gutter elements."
  (modify-specifier-instances 
   gutter-visible-specifier-p #'(lambda (spec prop visible-p)
				  (if (consp spec)
				      (if visible-p 
					  (if (memq prop spec) spec  
					    (cons prop spec))
					(delq prop spec))
				    (if visible-p (list prop))))
   (list prop visible-p)
   'force nil locale tag-set)
  (run-hook-with-args 'gutter-element-visibility-changed-hook prop visible-p))

(defun gutter-element-visible-p (gutter-visible-specifier-p
				 prop &optional domain)
  "Determine whether a gutter element is visible.
Given GUTTER-VISIBLE-SPECIFIER-P and gutter element PROP, return
non-nil if it is visible in optional DOMAIN."
  (let ((spec (specifier-instance gutter-visible-specifier-p domain)))
    (or (and (listp spec) (memq 'buffers-tab spec))
 	spec)))

(defun init-gutter ()
  "Initialize the gutter."
  ;; do nothing as yet.
  )

;;; gutter.el ends here.