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−;;; auto-show.el --- perform automatic horizontal scrolling as point moves
+
−
+
−;; Copyright (C) 1997 Free Software Foundation, Inc.
+
−;; This file is in the public domain.
+
−
+
−;; Author: Pete Ware <ware@cis.ohio-state.edu>
+
−;; Maintainer: XEmacs Development Team
+
−;; Keywords: extensions, internal, dumped
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−
+
−;; 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 XEmacs; see the file COPYING.  If not, write to the Free
+
−;; Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+
−;; 02111-1307, USA.
+
−
+
−;;; Synched up with: Emacs/Mule zeta.
+
−
+
−;;; Commentary:
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−
+
−;; This file is dumped with XEmacs.
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−
+
−;; Modified by: Ben Wing <ben@xemacs.org>
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−
+
−;; This file provides functions that
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−;; automatically scroll the window horizontally when the point moves
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−;; off the left or right side of the window.
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−
+
−;; Once this library is loaded, automatic horizontal scrolling
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−;; occurs whenever long lines are being truncated.
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−;; To request truncation of long lines, set the variable
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−;; Setting the variable `truncate-lines' to non-nil.
+
−;; You can do this for all buffers as follows:
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−;;
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−;; (set-default 'truncate-lines t)
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−
+
−;; Here is how to do it for C mode only:
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−;;
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−;; (set-default 'truncate-lines nil)	; this is the original value
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−;; (defun my-c-mode-hook ()
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−;;   "Run when C-mode starts up.  Changes ..."
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−;;   ... set various personal preferences ...
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−;;   (setq truncate-lines t))
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−;; (add-hook 'c-mode-hook 'my-c-mode-hook)
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−;;
+
−;;
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−;; As a finer level of control, you can still have truncated lines but
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−;; without the automatic horizontal scrolling by setting the buffer
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−;; local variable `auto-show-mode' to nil.  The default value is t.
+
−;; The command `auto-show-mode' toggles the value of the variable
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−;; `auto-show-mode'.
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−
+
−;;; Code:
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−
+
−(defgroup auto-show nil
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−  "Perform automatic horizontal scrolling as point moves."
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−  :group 'display
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−  :group 'extensions)
+
−
+
−;; This is preloaded, so we don't need special :set, :require, etc.
+
−(defcustom auto-show-mode t
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−  "*Non-nil enables automatic horizontal scrolling, when lines are truncated.
+
−The default value is t.  To change the default, do this:
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−	(set-default 'auto-show-mode nil)
+
−See also command `auto-show-mode'.
+
−This variable has no effect when lines are not being truncated.
+
−This variable is automatically local in each buffer where it is set."
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−  :type 'boolean
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−  :group 'auto-show)
+
−
+
−(make-variable-buffer-local 'auto-show-mode)
+
−
+
−(defcustom auto-show-shift-amount 8 
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−  "*Extra columns to scroll. for automatic horizontal scrolling."
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−  :type 'integer
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−  :group 'auto-show)
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−
+
−(defcustom auto-show-show-left-margin-threshold 50
+
−  "*Threshold column for automatic horizontal scrolling to the right.
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−If point is before this column, we try to scroll to make the left margin
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−visible.  Setting this to 0 disables this feature."
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−  :type 'number
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−  :group 'auto-show)
+
−
+
−(defun auto-show-mode (arg)
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−  "Turn automatic horizontal scroll mode on or off.
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−With arg, turn auto scrolling on if arg is positive, off otherwise.
+
−This mode is enabled or disabled for each buffer individually.
+
−It takes effect only when `truncate-lines' is non-nil."
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−  (interactive "P")
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−  (setq auto-show-mode
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−	(if (null arg)
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−	    (not auto-show-mode)
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−	  (> (prefix-numeric-value arg) 0))))
+
−
+
−;; XEmacs addition:
+
−(defvar auto-show-inhibiting-commands
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−  '(scrollbar-char-left
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−    scrollbar-char-right
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−    scrollbar-page-left
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−    scrollbar-page-right
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−    scrollbar-to-left
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−    scrollbar-to-right
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−    scrollbar-horizontal-drag)
+
−  "Commands that inhibit auto-show behavior.
+
−This normally includes the horizontal scrollbar commands.")
+
−
+
−;; XEmacs addition:
+
−(defun auto-show-should-take-action-p ()
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−  (and auto-show-mode (window-truncated-p)
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−       (equal (window-buffer) (current-buffer))
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−       (not (memq this-command auto-show-inhibiting-commands))))
+
−
+
−;; XEmacs addition:
+
−(defun auto-show-make-region-visible (start end)
+
−  "Move point in such a way that the region (START, END) is visible.
+
−This only does anything if auto-show-mode is enabled, and it doesn't
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−actually do any horizontal scrolling; rather, it just sets things up so
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−that the region will be visible when `auto-show-make-point-visible'
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−is next called (this happens after every command)."
+
−  (if (auto-show-should-take-action-p)
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−      (let* ((scroll (window-hscroll))	;how far window is scrolled
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−	     (w-width (- (window-width) 
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−			 (if (> scroll 0)
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−			     2 1)))	;how wide window is on the screen
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−	     (right-col (+ scroll w-width))
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−	     (start-col (save-excursion (goto-char start) (current-column)))
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−	     (end-col (save-excursion (goto-char end) (current-column))))
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−	(cond ((and (>= start-col scroll)
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−		    (<= end-col right-col))
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−	       ;; already completely visible
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−	       nil)
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−	      ((< start-col scroll)
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−	       (scroll-right (- scroll start-col)))
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−	      (t
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−	       (scroll-left (- end-col right-col)))))))
+
−
+
−(defun auto-show-make-point-visible (&optional ignore-arg)
+
−  "Scroll horizontally to make point visible, if that is enabled.
+
−This function only does something if `auto-show-mode' is non-nil
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−and longlines are being truncated in the selected window.
+
−See also the command `auto-show-mode'."
+
−  (interactive)
+
−  ;; XEmacs change
+
−  (if (auto-show-should-take-action-p)
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−      (let* ((col (current-column))	;column on line point is at
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−	     (scroll (window-hscroll))	;how far window is scrolled
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−	     (w-width (- (window-width) 
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−			 (if (> scroll 0)
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−			     2 1)))	;how wide window is on the screen
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−	     (right-col (+ scroll w-width)))
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−	(if (and (< col auto-show-show-left-margin-threshold)
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−		 (< col (window-width))
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−		 (> scroll 0))
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−	    (scroll-right scroll)
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−	  (if (< col scroll)		;to the left of the screen
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−	      (scroll-right (+ (- scroll col) auto-show-shift-amount))
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−	    (if (or (> col right-col)	;to the right of the screen
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−		    (and (= col right-col)
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−			 (not (eolp))))
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−		(scroll-left (+ auto-show-shift-amount 
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−				(- col (+ scroll w-width))))))))))
+
−
+
−;; XEmacs change:
+
−;; #### instead of this, we kludgily call it from the C code, to make sure
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−;; that it's done after any other things on post-command-hook (which might
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−;; move point).
+
−;; Do auto-scrolling after commands.
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−;;(add-hook 'post-command-hook 'auto-show-make-point-visible)
+
−
+
−;; If being dumped, turn it on right away.
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−(when (boundp 'pureload)
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−  (auto-show-mode 1))
+
−
+
−;; Do auto-scrolling in comint buffers after process output also.
+
−; XEmacs -- don't do this now, it messes up comint.
+
−;(add-hook 'comint-output-filter-functions 'auto-show-make-point-visible t)
+
−
+
−(provide 'auto-show)
+
−
+
−;;; auto-show.el ends here