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Add new option `mouse-drag-and-drop-region-scroll-margin'

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* etc/NEWS: Announce new user option.
* lisp/mouse.el (mouse-drag-and-drop-region-scroll-margin): New
user option.
(mouse-drag-and-drop-region): Implement "scroll margin" like
behavior during mouse movement.
This commit is contained in:
Po Lu 2022-04-02 15:45:00 +08:00
parent 0a32037c92
commit e351e9037c
2 changed files with 41 additions and 0 deletions
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36
lisp/mouse.el
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@ -97,6 +97,14 @@ point at the click position."
:type 'boolean
:version "22.1")
(defcustom mouse-drag-and-drop-region-scroll-margin nil
"If non-nil, the scroll margin inside a window when dragging text.
If the mouse moves this many lines close to the top or bottom of
a window while dragging text, then that window will be scrolled
down and up respectively."
:type 'integer
:version "29.1")
(defvar mouse--last-down nil)
(defun mouse--down-1-maybe-follows-link (&optional _prompt)
@ -3084,6 +3092,34 @@ is copied instead of being cut."
;; Handle `mouse-autoselect-window'.
(memq (car event) '(select-window switch-frame))))
(catch 'drag-again
;; If the mouse is in the drag scroll margin, scroll
;; either up or down depending on which margin it is in.
(when mouse-drag-and-drop-region-scroll-margin
(let* ((row (cdr (posn-col-row (event-end event))))
(window (posn-window (event-end event)))
(text-height (window-text-height window))
;; Make sure it's possible to scroll both up
;; and down if the margin is too large for the
;; window.
(margin (min (/ text-height 3)
mouse-drag-and-drop-region-scroll-margin)))
;; At 2 lines, the window becomes too small for any
;; meaningful scrolling.
(unless (<= text-height 2)
;; We could end up at the beginning or end of the
;; buffer.
(ignore-errors
(when (windowp window)
(cond
;; Inside the bottom scroll margin, scroll up.
((> row (- text-height margin))
(with-selected-window window
(scroll-up 1)))
;; Inside the top scroll margin, scroll down.
((< row margin)
(with-selected-window window
(scroll-down 1)))))))))
;; Obtain the dragged text in region. When the loop was
;; skipped, value-selection remains nil.
(unless value-selection