Only a drag context which was created with 'drag_begin' will be
guaranteed to have a source window at all times. Thus, in finalize we
cannot assume we can retrieve a GdkDisplay from the source_window
pointer since it may be NULL. Though, the display is only needed for
contexts created via 'drag_begin' thus we can retrieve it after
checking that is the case.
https://bugzilla.gnome.org/show_bug.cgi?id=749339
We currently only hold the last offer received, which is wrong, as both
are independent and have different life cycles.
This means we have to store per-selection wl_data_offer and targets, and
maintain these as appropriate from the clipboard/DnD specific entry points.
gdk_wayland_drop_context_set_status() can't do much else currently besides
picking a mimetype (the first one is currently chosen). This may incorrectly
unset the mimetype chosen on .receive(), so the transfer is cancelled before
it even starts.
At the time drop_reply happens, we should have already picked a mimetype
along the way, so only cover for accepted=FALSE in order to unset it.
It will be useless to check the source window on the destination side,
it's at the moment always NULL. Fetch the display from the device instead,
which will be set for every GdkDragContext.
On wayland the DnD surface must be created early when starting the drag
operation, so offer API for GTK+ to get the GdkWindow used as a DnD
surface on the drag operation.
https://bugzilla.gnome.org/show_bug.cgi?id=697855
The wl_data_source is retrieved from the selection object for the DnD
selection, and used to initiate a drag. When the drag is finished, a
button release or touch end event is synthesized to finish the DnD
operation after the compositor grab is gone.
https://bugzilla.gnome.org/show_bug.cgi?id=697855
