1 ;;; This file is in the public domain.
3 ;;; Keywords: scroll display minor-mode
4 ;;; Author: Pete Ware <ware@cis.ohio-state.edu>
9 ;;; This file provides functions that
10 ;;; automatically scroll the window horizontally when the point moves
11 ;;; off the left or right side of the window.
13 ;;; Once this library is loaded, automatic horizontal scrolling
14 ;;; occurs whenever long lines are being truncated.
15 ;;; To request truncation of long lines, set the variable
16 ;;; Setting the variable `truncate-lines' to non-nil.
17 ;;; You can do this for all buffers as follows:
19 ;;; (set-default 'truncate-lines t)
21 ;;; Here is how to do it for C mode only:
23 ;;; (set-default 'truncate-lines nil) ; this is the original value
24 ;;; (defun my-c-mode-hook ()
25 ;;; "Run when C-mode starts up. Changes ..."
26 ;;; ... set various personal preferences ...
27 ;;; (setq truncate-lines t))
28 ;;; (add-hook 'c-mode-hook 'my-c-mode-hook)
31 ;;; As a finer level of control, you can still have truncated lines but
32 ;;; without the automatic horizontal scrolling by setting the buffer
33 ;;; local variable `auto-show-mode' to nil. The default value is t.
34 ;;; The command `auto-show-mode' toggles the value of the variable
39 (defvar auto-show-mode t
40 "*Non-nil enables automatic horizontal scrolling, when lines are truncated.
41 The default value is t. To change the default, do this:
42 (set-default 'auto-show-mode nil)
43 See also command `auto-show-mode'.
44 This variable has no effect when lines are not being truncated.")
46 (make-variable-buffer-local 'auto-show-mode
)
48 (defvar auto-show-shift-amount
8
49 "*Extra columns to scroll. for automatic horizontal scrolling.")
51 (defvar auto-show-show-left-margin-threshold
50
52 "*Threshold column for automatic horizontal scrolling to the right.
53 If point is before this column, we try to scroll to make the left margin
54 visible. Setting this to 0 disables this feature.")
56 (defun auto-show-truncationp ()
57 "True if line truncation is enabled for the selected window."
59 (and truncate-partial-width-windows
60 (< (window-width) (frame-width)))))
63 (defun auto-show-mode (arg)
64 "Turn automatic horizontal scroll mode on or off.
65 With arg, turn auto scrolling on if arg is positive, off otherwise."
70 (> (prefix-numeric-value arg
) 0))))
72 (defun auto-show-make-point-visible (&optional ignore-arg
)
73 "Scroll horizontally to make point visible, if that is enabled.
74 This function only does something if `auto-show-mode' is non-nil
75 and longlines are being truncated in the selected window.
76 See also the command `auto-show-toggle'."
78 (if (and auto-show-mode
(auto-show-truncationp)
79 (equal (window-buffer) (current-buffer)))
80 (let* ((col (current-column)) ;column on line point is at
81 (scroll (window-hscroll)) ;how far window is scrolled
82 (w-width (- (window-width)
84 2 1))) ;how wide window is on the screen
85 (right-col (+ scroll w-width
)))
86 (if (and (< col auto-show-show-left-margin-threshold
)
87 (< col
(window-width))
90 (if (< col scroll
) ;to the left of the screen
91 (scroll-right (+ (- scroll col
) auto-show-shift-amount
))
92 (if (or (> col right-col
) ;to the right of the screen
93 (and (= col right-col
)
95 (scroll-left (+ auto-show-shift-amount
96 (- col
(+ scroll w-width
))))
104 ;; Do auto-scrolling after commands.
105 (add-hook 'post-command-hook
'auto-show-make-point-visible
)
107 ;; Do auto-scrolling in comint buffers after process output also.
108 (add-hook 'comint-output-filter-functions
'auto-show-make-point-visible t
)
112 ;; auto-show.el ends here