93 lines
3.1 KiB
EmacsLisp
93 lines
3.1 KiB
EmacsLisp
;;; guix-history.el --- History of buffer information
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;; Copyright © 2014 Alex Kost <alezost@gmail.com>
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;; This file is part of GNU Guix.
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;; GNU Guix is free software; you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
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;; (at your option) any later version.
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;; GNU Guix is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;; You should have received a copy of the GNU General Public License
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;; along with this program. If not, see <http://www.gnu.org/licenses/>.
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;;; Commentary:
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;; This file provides support for history of buffers similar to the
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;; history of a `help-mode' buffer.
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;;; Code:
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(require 'cl-macs)
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(defvar-local guix-history-stack-item nil
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"Current item of the history.
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A list of the form (FUNCTION [ARGS ...]).
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The item is used by calling (apply FUNCTION ARGS).")
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(put 'guix-history-stack-item 'permanent-local t)
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(defvar-local guix-history-back-stack nil
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"Stack (list) of visited items.
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Each element of the list has a form of `guix-history-stack-item'.")
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(put 'guix-history-back-stack 'permanent-local t)
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(defvar-local guix-history-forward-stack nil
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"Stack (list) of items visited with `guix-history-back'.
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Each element of the list has a form of `guix-history-stack-item'.")
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(put 'guix-history-forward-stack 'permanent-local t)
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(defvar guix-history-size 0
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"Maximum number of items saved in history.
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If 0, the history is disabled.")
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(defun guix-history-add (item)
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"Add ITEM to history."
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(and guix-history-stack-item
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(push guix-history-stack-item guix-history-back-stack))
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(setq guix-history-forward-stack nil
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guix-history-stack-item item)
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(when (>= (length guix-history-back-stack)
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guix-history-size)
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(setq guix-history-back-stack
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(cl-loop for elt in guix-history-back-stack
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for i from 1 to guix-history-size
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collect elt))))
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(defun guix-history-replace (item)
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"Replace current item in history with ITEM."
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(setq guix-history-stack-item item))
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(defun guix-history-goto (item)
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"Go to the ITEM of history.
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ITEM should have the form of `guix-history-stack-item'."
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(or (listp item)
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(error "Wrong value of history element"))
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(setq guix-history-stack-item item)
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(apply (car item) (cdr item)))
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(defun guix-history-back ()
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"Go back to the previous element of history in the current buffer."
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(interactive)
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(or guix-history-back-stack
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(user-error "No previous element in history"))
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(push guix-history-stack-item guix-history-forward-stack)
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(guix-history-goto (pop guix-history-back-stack)))
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(defun guix-history-forward ()
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"Go forward to the next element of history in the current buffer."
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(interactive)
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(or guix-history-forward-stack
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(user-error "No next element in history"))
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(push guix-history-stack-item guix-history-back-stack)
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(guix-history-goto (pop guix-history-forward-stack)))
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(provide 'guix-history)
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;;; guix-history.el ends here
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