Commit 495a2b0a authored by Richard M. Stallman's avatar Richard M. Stallman
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Initial revision

parent ed17d24f
;; LCD Archive Entry:
;; auto-show|Pete Ware||
;; Automatically scroll horizontally|
;; 95-02-24|1.9|~/misc/auto-show.el|
;;; Author:
;;; Pete Ware
;;; CIS Dept, Ohio State University w/ (614) 292-8501
;;; 774 Dreese, 2015 Neil Ave. h/ (614) 791-1347
;;; Columbus, OH 43210
;;; 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 <> 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 added auto-show-toggle function.
;;; 02/08/95 Added auto-show-enable as per
;;; (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."
(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'."
(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."
(add-hook 'comint-output-filter-functions 'auto-show-make-point-visible t)
;; end of auto-show.el
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