--- /dev/null
+;; LCD Archive Entry:
+;; auto-show|Pete Ware|ware@cis.ohio-state.edu|
+;; Automatically scroll horizontally|
+;; 95-02-24|1.9|~/misc/auto-show.el|
+;;
+;;;
+;;; Author:
+;;;
+;;; Pete Ware ware@cis.ohio-state.edu
+;;; CIS Dept, Ohio State University w/ (614) 292-8501
+;;; 774 Dreese, 2015 Neil Ave. h/ (614) 791-1347
+;;; Columbus, OH 43210 http://www.cis.ohio-state.edu/~ware
+;;;
+;;;
+;;; Modification history:
+;;; 02/24/95 Added auto-show-show-left-margin-threshold so that if
+;;; there is anyway for the left margin to be displayed it is.
+;;; 02/24/95 Only scroll window if it matches current buffer. Added
+;;; function for enabeling scrolling in comint buffers on output.
+;;; 02/13/95 Aded Kevin Broadey <KevinB@bartley.demon.co.uk> fix so that
+;;; it doesn't scroll if we are at window border and at the
+;;; end of the line (i.e. newline character)
+;;; 02/10/95 jeff.dwork@amd.com added auto-show-toggle function.
+;;; 02/08/95 Added auto-show-enable as per
+;;; jeff.dwork@amd.com (Jeff Dwork)'s suggestion. Cleaned up
+;;; documentation.
+;;; 02/07/95 Rewrote for emacs 19: much, much cleaner. Renamed auto-show
+;;; 8/6/90 Make next-line/previous-line do better job following movement.
+;;; 3/21/90 better calculation of w-width in e-make-point-visible
+;;; test for truncated windows
+;;; added substitute-in-keymap
+;;; renamed to auto-horizontal
+;;; added backward-delete-char
+;;; 8/13/88 Created
+
+;;;
+;;; This is a rewrite of auto-horizontal. It is comparable in
+;;; functionality to hscroll.el except it is not a minor mode and does
+;;; not use any timers. This file provides functions that
+;;; automatically scroll the window horizontally when the point moves
+;;; off the left or right side of the window. To load it just add:
+;;; (require 'auto-show)
+;;; to your .emacs.
+;;;
+;;; Setting the variable ``truncate-lines'' to non-nil causes long
+;;; lines to disappear off the end of the screen instead of wrapping
+;;; to the beginning of the next line. To make this the default for
+;;; all buffers add the following line to your .emacs (sans ;;;):
+;;;
+;;; (set-default 'truncate-lines t)
+;;;
+
+;;; However, I've found that I only want this when I'm editing C code.
+;;; Accordingly I have something like the following in my .emacs:
+;;;
+;;; (set-default 'truncate-lines nil) ; this is the original value
+;;; (defun my-c-mode-hook ()
+;;; "Run when C-mode starts up. Changes ..."
+;;; ... set various personal preferences ...
+;;; (setq truncate-lines t))
+;;; (add-hook 'c-mode-hook 'my-c-mode-hook)
+;;;
+;;;
+;;; As a finer level of control, one can still have truncated lines but
+;;; without the automatic left and right scrolling by setting the buffer
+;;; local variable ``auto-show-enable'' to nil. The default value is t.
+;;; The command ``auto-show-toggle'' will toggle the value of
+;;; ``auto-show-enable''.
+;;;
+;;;
+;;; I also like the output from my shell's (and other comint.el based commands)
+;;; to scroll on output. One can call:
+;;;
+;;; (auto-show-comint-make-point-visible)
+;;;
+;;; which adds auto-show-make-point-visible to comint-output-filter-functions.
+
+(provide 'auto-show)
+
+;;;************************************************************
+;;;*
+;;;* Define Automatic Horizontal Scrolling Functions
+;;;*
+;;;************************************************************
+
+(add-hook 'post-command-hook 'auto-show-make-point-visible)
+
+(defvar auto-show-enable t
+ "*Allows one to turn off automatic horizontal scrolling on a per buffer
+basis independent of whether truncate-lines is t. The default value is t.
+To change the default:
+ (set-default 'auto-show-enable nil)
+Any time auto-show-enable is changed it is only in the current buffer:
+ (setq auto-show-enable nil)
+turns it on for this buffer.
+See also command `auto-show-toggle'.")
+
+(make-variable-buffer-local 'auto-show-enable)
+
+(defvar auto-show-shift-amount 8
+ "*Extra amount to shift a line when point is not visible.")
+
+(defvar auto-show-show-left-margin-threshold 50
+ "*Point must be before this column for us to try and make the left margin
+visible. Setting this to 0 disables this feature.")
+
+(defun auto-show-truncationp ()
+ "True if truncation is on for current window."
+ (or truncate-lines
+ (and truncate-partial-width-windows
+ (< (window-width) (frame-width)))))
+
+(defun auto-show-toggle ()
+ "Toggle value of auto-show-enable."
+ (interactive)
+ (setq auto-show-enable (not auto-show-enable)))
+
+(defun auto-show-make-point-visible (&optional ignore-arg)
+ "Scrolls the screen horizontally to make point visible but only if
+auto-show-enable is non-nil and lines are truncated. See also variable
+`auto-show-enable' and command `auto-show-toggle'."
+ (interactive)
+ (if (and auto-show-enable (auto-show-truncationp)
+ (equal (window-buffer) (current-buffer)))
+ (let* ((col (current-column)) ;column on line point is at
+ (scroll (window-hscroll)) ;how far window is scrolled
+ (w-width (- (window-width)
+ (if (> scroll 0)
+ 2 1))) ;how wide window is on the screen
+ (right-col (+ scroll w-width)))
+ (if (and (< col auto-show-show-left-margin-threshold)
+ (< col (window-width))
+ (> scroll 0))
+ (scroll-right scroll)
+ (if (< col scroll) ;to the left of the screen
+ (scroll-right (+ (- scroll col) auto-show-shift-amount))
+ (if (or (> col right-col) ;to the right of the screen
+ (and (= col right-col)
+ (not (eolp))))
+ (scroll-left (+ auto-show-shift-amount
+ (- col (+ scroll w-width))))
+ )
+ )
+ )
+ )
+ )
+ )
+
+(defun auto-show-comint-make-point-visible ()
+ "Add a function to comint-output-filter-functions that auto-scrolls
+left or right on output to the buffer.
+
+NOTE: you should load comint mode before this as comint.el uses a
+defvar to initialize comint-output-filter-functions to the default value."
+ (interactive)
+ (add-hook 'comint-output-filter-functions 'auto-show-make-point-visible t)
+ )
+
+;; end of auto-show.el
+
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