> > I wonder why it doesn't work to drop the text onto other applications.
>
> Probably because there's no standard protocol to drag and drop anything
> but files between different applications.
>
> Maybe not for every window system but on MacOS there is and many applications accept dragged text
> directly:
> https://developer.apple.com/documentation/uikit/drag_and_ drop/making_a_view_into_a_ drag_source
> - source info
For now `mouse-drag-and-drop-region' does nothing when
(event-end (read-event)) is toward out of the current frame.
I think the first step is to revise `mouse-drag-and-drop-region' to let
it drag text to a different frame.