On Wed, Oct 18, 2017 at 8:43 PM, 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?
> >>
> > ​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
>
> GNU Emacs 27.0.50 (build 1, x86_64-apple-darwin13.4.0, NS appkit-1265.21
> Version 10.9.5 (Build 13F1911)) of 2017-10-17
> Emacs -Q
>
> I cannot drag text among frames yet.  I think I still miss something.
> Can you show recipe that starts from emacs -Q?
>

​See if adding this fixes it:

    ;; From mouse-position:
    ;;    f = SELECTED_FRAME ();
    ;;    XSETFRAME (lispy_dummy, f);
    ;;  It seems like the XSETFRAME macro is not properly copying the value
of f on initial frame selection under the macOS window system.
    ;;  The problem occurs on other systems as well, e.g. Emacs 25.2 under
Windows 7.
    ;;  The function below is a temporary fix for this.
    (setq mouse-position-function
  (lambda (frame-x-dot-y)
    "Under macOS, mouse-position and mouse-pixel-position sometimes fail to
return the selected-frame (returning the prior frame instead); fix that
here."
    (if frame-x-dot-y (setcar frame-x-dot-y (selected-frame)))
    frame-x-dot-y))​