On Mon, Oct 16, 2017 at 9:45 AM, Robert Weiner <rsw@gnu.org> wrote:

> On Fri, Oct 13, 2017 at 5:57 AM, Tak Kunihiro <homeros.misasa@gmail.com>
> wrote:
>
>> I tried the revised `mouse-drag-and-drop-region' on Emacs -Q 26.0.90 on
>> macOS 10.9.5.  I can drag text within a frame but cannot do so among
>> frames.  I think I miss something.  Do you have idea?
>>
>
> ​The yellow visual rectangle of the text being dragged seems to get stuck
> at the source frame but if you continue your drag and release in another
> frame with a non-read-only buffer, your text should be properly dropped
> there.  Is this what you did?  Try it a couple different times to ensure
> there is not some initialization warm up problem.
>

​I see the issue now; the standard Emacs code does not handle cross-frame
drags well.  Replace the mouse-set-point function from mouse.el with the
version below and then the yellow rectangle of text will follow you to the
drag release frame and your drag-and-drops should work as you expect (with
the mouse-drag-and-drop-region changes from before).  -- Bob​

(defun mouse-set-point (event &optional promote-to-region)
  "Move point to the position clicked on with the mouse.
This should be bound to a mouse click event type.
If PROMOTE-TO-REGION is non-nil and event is a multiple-click,
select the corresponding element around point, with the resulting position
of
point determined by `mouse-select-region-move-to-beginning'."
  (interactive "e\np")
  (let ((start-w-or-f (posn-window (event-start event)))
(end-w-or-f   (posn-window (event-end event))))
    (if (framep start-w-or-f)
(with-selected-frame start-w-or-f (setq start-w-or-f (selected-window))))
    (if (framep end-w-or-f)
(with-selected-frame end-w-or-f (setq end-w-or-f (selected-window))))
    (if (and (window-minibuffer-p start-w-or-f)
     (not (minibuffer-window-active-p start-w-or-f)))
;; Select the ending frame only, not the window pressed within.
(select-frame (window-frame end-w-or-f))
      ;; Give temporary modes such as isearch a chance to turn off.
      (run-hooks 'mouse-leave-buffer-hook)
      (if (and promote-to-region (> (event-click-count event) 1))
  (progn (mouse-set-region event)
(when (and (boundp 'mouse-select-region-move-to-beginning)
    mouse-select-region-move-to-beginning)
   (when (> (posn-point (event-start event)) (region-beginning))
     (exchange-point-and-mark))))
;; Use event-end in case called from mouse-drag-region.
;; If EVENT is a click, event-end and event-start give same value.
(if (and (window-minibuffer-p end-w-or-f)
(not (minibuffer-window-active-p end-w-or-f)))
    ;; Select the ending frame only, not the window pressed within.
    (select-frame (window-frame end-w-or-f))
  (condition-case ()
      (posn-set-point (event-end event))
    (error (select-frame (window-frame end-w-or-f)))))))))