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;;; hhist.el --- Maintains history of Hyperbole buttons selected.
;; Copyright (C) 1991-1995 Free Software Foundation, Inc.
;; Developed with support from Motorola Inc.
;; Author: Bob Weiner, Brown U.
;; Maintainer: Mats Lidell <matsl@contactor.se>
;; Keywords: hypermedia
;; This file is part of GNU Hyperbole.
;; GNU Hyperbole 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 Hyperbole 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., 51 Franklin Street, Fifth Floor,
;; Boston, MA 02110-1301, USA.
;;; Commentary:
;;
;; This is minimal right now and will be extended.
;; Currently, it implements a push-pop stack of traversed locations.
;;
;; It will be extended to allow random access to previous locations
;; and to store traversal histories for later recall.
;;
;;; Code:
;;;
;;; Public functions
;;;
(defun hhist:add (elt)
"Adds ELT to hyper-history list if not the same as current or previous loc.
ELT must have been created via a call to 'hhist:element'."
;; Even though this next line looks useless, it cures a problem with
;; window buffer correspondences on startup, so don't remove it.
(set-buffer (window-buffer (selected-window)))
(let ((prev-buf (car elt)))
(if (or (equal prev-buf (buffer-name))
(equal prev-buf (car (car *hhist*))))
nil
(setq *hhist* (cons elt *hhist*)))))
(defun hhist:element ()
"Returns a history element for current point location."
(list (current-buffer) (point)))
(defun hhist:remove (&optional arg)
"Removes optional prefix ARG entries from history, returns to ARGth location.
The command is ignored with ARG < 1."
(interactive "p")
(setq arg (or arg 1))
(let ((prev-buf-line))
(if (null *hhist*)
(and (> arg 0)
(message "(hhist:remove): No previous source to which to return.")
(beep))
(while (and (> arg 0) *hhist*)
(setq prev-buf-line (car *hhist*)
*hhist* (cdr *hhist*)
arg (1- arg)))
(switch-to-buffer (car prev-buf-line))
(goto-char (car (cdr prev-buf-line)))
)))
(defun hhist:init ()
"Resets history list."
(interactive)
(setq *hhist* nil))
;;;
;;; Private functions
;;;
(defun hhist:wind-line ()
"Returns window relative line number that point is on."
(max 0 (1- (- (count-lines 1 (1+ (point)))
(count-lines 1 (window-start))))))
;;;
;;; Private variables
;;;
(defconst *hhist* nil
"List of previously visited Hyperbole button source locations.
Car of list is most recent.")
(provide 'hhist)
;;; hhist.el ends here
|
