wayland: Ensure drag surface offset changes update the DnD actor

src/wayland/meta-wayland-data-device.c

@@ -643,3 +643,29 @@ meta_wayland_data_device_set_keyboard_focus (MetaWaylandDataDevice *data_device)
       wl_data_device_send_selection (data_device_resource, offer);
     }
 }
+
+gboolean
+meta_wayland_data_device_is_dnd_surface (MetaWaylandDataDevice *data_device,
+                                         MetaWaylandSurface    *surface)
+{
+  return data_device->current_grab &&
+    data_device->current_grab->drag_surface == surface;
+}
+
+void
+meta_wayland_data_device_update_dnd_surface (MetaWaylandDataDevice *data_device)
+{
+  MetaWaylandDragGrab *drag_grab;
+
+  if (!data_device->current_grab)
+    return;
+
+  drag_grab = data_device->current_grab;
+
+  if (!drag_grab->feedback_actor || !drag_grab->drag_surface)
+    return;
+
+  meta_feedback_actor_set_anchor (META_FEEDBACK_ACTOR (drag_grab->feedback_actor),
+                                  -drag_grab->drag_surface->offset_x,
+                                  -drag_grab->drag_surface->offset_y);
+}

src/wayland/meta-wayland-data-device.h

@@ -44,4 +44,8 @@ void meta_wayland_data_device_init (MetaWaylandDataDevice *data_device);
 
 void meta_wayland_data_device_set_keyboard_focus (MetaWaylandDataDevice *data_device);
 
+gboolean meta_wayland_data_device_is_dnd_surface (MetaWaylandDataDevice *data_device,
+                                                  MetaWaylandSurface    *surface);
+void meta_wayland_data_device_update_dnd_surface (MetaWaylandDataDevice *data_device);
+
 #endif /* META_WAYLAND_DATA_DEVICE_H */

src/wayland/meta-wayland-surface.c

@@ -175,6 +175,13 @@ cursor_surface_commit (MetaWaylandSurface      *surface,
     meta_wayland_seat_update_cursor_surface (surface->compositor->seat);
 }
 
+static void
+dnd_surface_commit (MetaWaylandSurface      *surface,
+                    MetaWaylandPendingState *pending)
+{
+  meta_wayland_data_device_update_dnd_surface (&surface->compositor->seat->data_device);
+}
+
 static void
 calculate_surface_window_geometry (MetaWaylandSurface *surface,
                                    MetaRectangle      *total_geometry,
@@ -445,6 +452,8 @@ commit_pending_state (MetaWaylandSurface      *surface,
 
   if (surface == compositor->seat->pointer.cursor_surface)
     cursor_surface_commit (surface, pending);
+  else if (meta_wayland_data_device_is_dnd_surface (&compositor->seat->data_device, surface))
+    dnd_surface_commit (surface, pending);
   else if (surface->window)
     toplevel_surface_commit (surface, pending);
   else if (surface->subsurface.resource)