[mutter/gnome-3-36] wayland: Avoid automatically decoupling source/offer after grab

[Robert Mader <rmader src gnome org>]

commit a798438b5fb78a89f432196a8dc22143b58717ec
Author: Carlos Garnacho <carlosg gnome org>
Date:   Mon Feb 8 20:23:22 2021 +0100

    wayland: Avoid automatically decoupling source/offer after grab
    
    In the case that DnD is performed and succeeds, we want to release
    the grab early, and let the transfer IPC happen in the back. For
    that to happen without a hitch, drag source and offer must be left
    related to each other after undoing the grab, even though the default
    ungrabbing code does that automatically (indirectly, by unsetting the
    drag focus).
    
    In these cases, we used to manually unset the current source, so
    this decoupling was skipped. Notably, one missed case is X11 DnD,
    so we might end up with the situation there that DnD did succeed,
    transfer is ongoing, but the source and offer are already decoupled,
    this confused the machinery and missed the finishing XdndFinished
    to be emitted to the X11 drag source.
    
    The prior commits prepared for this source/offer decoupling being
    a manual operation, this commit avoids doing this automatically
    when ungrabbing.
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1720>
    
    (cherry picked from commit 698fe3f1a98ae492335cfe718bc8818c14e813de)

 src/wayland/meta-wayland-data-device.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)
---
diff --git a/src/wayland/meta-wayland-data-device.c b/src/wayland/meta-wayland-data-device.c
index 9311fd55d0..e40a58c29e 100644
--- a/src/wayland/meta-wayland-data-device.c
+++ b/src/wayland/meta-wayland-data-device.c
@@ -352,6 +352,7 @@ drag_grab_motion (MetaWaylandPointerGrab *grab,
 static void
 data_device_end_drag_grab (MetaWaylandDragGrab *drag_grab)
 {
+  meta_wayland_drag_grab_set_source (drag_grab, NULL);
   meta_wayland_drag_grab_set_focus (drag_grab, NULL);
 
   if (drag_grab->drag_origin)
@@ -366,8 +367,6 @@ data_device_end_drag_grab (MetaWaylandDragGrab *drag_grab)
       wl_list_remove (&drag_grab->drag_icon_listener.link);
     }
 
-  meta_wayland_drag_grab_set_source (drag_grab, NULL);
-
   if (drag_grab->feedback_actor)
     {
       clutter_actor_remove_all_children (drag_grab->feedback_actor);
@@ -448,9 +447,6 @@ drag_grab_button (MetaWaylandPointerGrab *grab,
           meta_wayland_data_source_has_target (source) &&
           meta_wayland_data_source_get_current_action (source))
         {
-          /* Detach the data source from the grab, it's meant to live longer */
-          meta_wayland_drag_grab_set_source (drag_grab, NULL);
-
           meta_wayland_surface_drag_dest_drop (drag_grab->drag_focus);
           meta_wayland_data_source_notify_drop_performed (source);