RFR: 8325591: [Mac] DRAG_DONE reports null transferMode when destination is external

[Kevin Rushforth]

On Fri, 16 Feb 2024 22:35:49 GMT, Martin Fox <mfox at openjdk.org> wrote:

> At the end of a drag operation the Mac Glass code sends out a DRAG_DONE event using the operation mask tracked in the GlassDragSource to determine the final transfer mode. That mask is only updated when a window in the JavaFX app is the drop destination. If the drag moves to an external destination the mask is set to NONE. If the drag terminates in the external destination that NONE forms the basis of the transfer mode sent via the DRAG_DONE event.
> 
> At the very end of the drag the OS calls the NSDraggingSource (GlassDraggingSource) with the final drag operation. This PR issues the DRAG_DONE from that callback so it can get the final transfer mode correct for both internal and external destinations.

The code changes look good. I did a quick test and it seems fine.

Would you be able to provide a manual test program for this case, under `tests/manual/dnd`? Also, can you merge in the latest changes from `master`?

-------------

PR Review: https://git.openjdk.org/jfx/pull/1371#pullrequestreview-2029735350