gtk/main: Fix handling of !owner_events grabs

These are meant to always redirect events to the grabbing surface,
even for other surfaces of the same client. We weren't doing that
(instead letting the event go through unmodified), fix this handling
so GTK sees the events consistenty.

gtk/gtkmain.c

@@ -1013,8 +1013,7 @@ rewrite_event_for_grabs (GdkEvent *event)
       display = gdk_event_get_display (event);
       device = gdk_event_get_device (event);
 
-      if (!gdk_device_grab_info (display, device, &grab_surface, &owner_events) ||
-          !owner_events)
+      if (!gdk_device_grab_info (display, device, &grab_surface, &owner_events))
         return NULL;
       break;
     default:
@@ -1024,11 +1023,24 @@ rewrite_event_for_grabs (GdkEvent *event)
   event_widget = gtk_get_event_widget (event);
   grab_widget = GTK_WIDGET (gtk_native_get_for_surface (grab_surface));
 
-  if (grab_widget &&
-      gtk_main_get_window_group (grab_widget) != gtk_main_get_window_group (event_widget))
-    return rewrite_event_for_surface (event, grab_surface);
-  else
+  if (!grab_widget)
     return NULL;
+
+  /* If owner_events was set, events in client surfaces get forwarded
+   * as normal, but we consider other window groups foreign surfaces.
+   */
+  if (owner_events &&
+      gtk_main_get_window_group (grab_widget) == gtk_main_get_window_group (event_widget))
+    return NULL;
+
+  /* If owner_events was not set, events only get sent to the grabbing
+   * surface.
+   */
+  if (!owner_events &&
+      grab_surface == gtk_native_get_surface (gtk_widget_get_native (event_widget)))
+    return NULL;
+
+  return rewrite_event_for_surface (event, grab_surface);
 }
 
 static GdkEvent *