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(scroll-bar-drag-position): New function.

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(scroll-bar-maybe-set-window-start): New function.
This commit is contained in:
Richard M. Stallman 1996-05-11 18:30:16 +00:00
parent 12c11fcd42
commit aeee66be3b
1 changed files with 32 additions and 0 deletions
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32
lisp/scroll-bar.el
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@ -114,6 +114,38 @@ EVENT should be a scroll bar click or drag event."
(beginning-of-line)
(set-window-start window (point))))))
(defun scroll-bar-drag-position (portion-whole)
"Calculate new window start for drag event."
(save-excursion
(goto-char (+ (point-min)
(scroll-bar-scale portion-whole
(- (point-max) (point-min)))))
(beginning-of-line)
(point)))
(defun scroll-bar-maybe-set-window-start (event)
"Set the window start according to where the scroll bar is dragged.
Only change window start if the new start is substantially different.
EVENT should be a scroll bar click or drag event."
(interactive "e")
(let* ((end-position (event-end event))
(window (nth 0 end-position))
(portion-whole (nth 2 end-position))
(next-portion-whole (cons (1+ (car portion-whole))
(cdr portion-whole)))
portion-start
next-portion-start
(current-start (window-start window)))
(save-excursion
(set-buffer (window-buffer window))
(setq portion-start (scroll-bar-drag-position portion-whole))
(setq next-portion-start (max
(scroll-bar-drag-position next-portion-whole)
(1+ portion-start)))
(if (or (> current-start next-portion-start)
(< current-start portion-start))
(set-window-start window portion-start)))))
;; Scroll the window to the proper position for EVENT.
(defun scroll-bar-drag-1 (event)
(let* ((start-position (event-start event))