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;;; page.el --- page motion commands for Emacs
;; Copyright (C) 1985, 2001-2017 Free Software Foundation, Inc.
;; Maintainer: emacs-devel@gnu.org
;; Keywords: wp convenience
;; Package: emacs
;; 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 3 of the License, 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. If not, see <https://www.gnu.org/licenses/>.
;;; Commentary:
;; This code provides the page-oriented movement and selection commands
;; documented in the Emacs manual.
;;; Code:
(defun forward-page (&optional count)
"Move forward to page boundary. With arg, repeat, or go back if negative.
A page boundary is any line whose beginning matches the regexp
`page-delimiter'."
(interactive "p")
(or count (setq count 1))
(while (and (> count 0) (not (eobp)))
;; In case the page-delimiter matches the null string,
;; don't find a match without moving.
(if (bolp) (forward-char 1))
(if (re-search-forward page-delimiter nil t)
nil
(goto-char (point-max)))
(setq count (1- count)))
(while (and (< count 0) (not (bobp)))
;; In case the page-delimiter matches the null string,
;; don't find a match without moving.
(and (save-excursion (re-search-backward page-delimiter nil t))
(= (match-end 0) (point))
(goto-char (match-beginning 0)))
(unless (bobp)
(forward-char -1)
(if (re-search-backward page-delimiter nil t)
;; We found one--move to the end of it.
(goto-char (match-end 0))
;; We found nothing--go to beg of buffer.
(goto-char (point-min))))
(setq count (1+ count))))
(defun backward-page (&optional count)
"Move backward to page boundary. With arg, repeat, or go fwd if negative.
A page boundary is any line whose beginning matches the regexp
`page-delimiter'."
(interactive "p")
(or count (setq count 1))
(forward-page (- count)))
(defun mark-page (&optional arg)
"Put mark at end of page, point at beginning.
A numeric arg specifies to move forward or backward by that many pages,
thus marking a page other than the one point was originally in."
(interactive "P")
(setq arg (if arg (prefix-numeric-value arg) 0))
(if (> arg 0)
(forward-page arg)
(if (< arg 0)
(forward-page (1- arg))))
(forward-page)
(push-mark nil t t)
(forward-page -1))
(defun narrow-to-page (&optional arg)
"Make text outside current page invisible.
A numeric arg specifies to move forward or backward by that many pages,
thus showing a page other than the one point was originally in."
(interactive "P")
(setq arg (if arg (prefix-numeric-value arg) 0))
(save-excursion
(widen)
(if (> arg 0)
(forward-page arg)
(if (< arg 0)
(let ((adjust 0)
(opoint (point)))
;; If we are not now at the beginning of a page,
;; move back one extra time, to get to the start of this page.
(save-excursion
(beginning-of-line)
(or (and (looking-at page-delimiter)
(eq (match-end 0) opoint))
(setq adjust 1)))
(forward-page (- arg adjust)))))
;; Find the end of the page.
(set-match-data nil)
(forward-page)
;; If we stopped due to end of buffer, stay there.
;; If we stopped after a page delimiter, put end of restriction
;; at the beginning of that line.
;; Before checking the match that was found,
;; verify that forward-page actually set the match data.
(if (and (match-beginning 0)
(save-excursion
(goto-char (match-beginning 0)) ; was (beginning-of-line)
(looking-at page-delimiter)))
(goto-char (match-beginning 0))) ; was (beginning-of-line)
(narrow-to-region (point)
(progn
;; Find the top of the page.
(forward-page -1)
;; If we found beginning of buffer, stay there.
;; If extra text follows page delimiter on same line,
;; include it.
;; Otherwise, show text starting with following line.
(if (and (eolp) (not (bobp)))
(forward-line 1))
(point)))))
(put 'narrow-to-page 'disabled t)
(defun count-lines-page ()
"Report number of lines on current page, and how many are before or after point."
(interactive)
(save-excursion
(let ((opoint (point)) beg end
total before after)
(forward-page)
(beginning-of-line)
(or (looking-at page-delimiter)
(end-of-line))
(setq end (point))
(backward-page)
(setq beg (point))
(setq total (count-lines beg end)
before (count-lines beg opoint)
after (count-lines opoint end))
(message "Page has %d lines (%d + %d)" total before after))))
(defun what-page ()
"Print page and line number of point."
(interactive)
(save-restriction
(widen)
(save-excursion
(let ((count 1)
(opoint (point)))
(goto-char (point-min))
(while (re-search-forward page-delimiter opoint t)
(if (= (match-beginning 0) (match-end 0))
(forward-char 1))
(setq count (1+ count)))
(message "Page %d, line %d" count (line-number-at-pos opoint))))))
;;; Place `provide' at end of file.
(provide 'page)
;;; page.el ends here
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