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+;;  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
+