Findings on JDK-8211302

[Thiago Milczarek Sayao]

Hello,

I have been looking into JDK-8211302.

https://bugs.openjdk.java.net/browse/JDK-8211302

Did not find a solution, but the problem is because 
gdk_drag_context_get_selected_action(event->context) is returning ZERO. That's 
also why the cursor does not update on the drop location. Subsequent events do 
not get fired to complete the drop, because it falls on the abort code below:

static void process_dnd_source_mouse_release(GdkWindow *window, GdkEventButton 
*event) {
    (void)window;
    (void)event;

    glass_gdk_master_pointer_ungrab();

    if (gdk_drag_context_get_selected_action(get_drag_context())) {
        gdk_drag_drop(get_drag_context(), GDK_CURRENT_TIME);
    } else {
        gdk_drag_abort(get_drag_context(), GDK_CURRENT_TIME);
        /* let the gdk_drag_abort messages handled before finish */
        gdk_threads_add_idle((GSourceFunc) dnd_finish_callback, NULL);
    }
}


I also suspect this will be needed, and it was introduced in GDK 3.20:

gdk_drag_drop_done(get_drag_context(), TRUE)

One solution is to check the version on build, other is to bundle the GTK lib 
(which makes it more safe to GDK changes).

Cheers.