[mutter/wip/carlosg/sync-pointer-in-mutter: 1/2] compositor: Sync pointer after begin/end modal on X11

[Carlos Garnacho <carlosg src gnome org>]

commit afc06cd8a161d2ede09cf9848ab7a8c5e6ef0011
Author: Carlos Garnacho <carlosg gnome org>
Date:   Fri Dec 18 14:59:17 2020 +0100

    compositor: Sync pointer after begin/end modal on X11
    
    Ensure we issue a motion event for the current pointer position,
    as there might be situations where compositor modals get X grabs
    from other clients stacked on top, or missed events in between
    otherwise.
    
    Ensure the Clutter state is still up-to-date afterwards here. This
    replaces some sync_pointer() calls done in GNOME Shell code, always
    done after modality changes.

 src/backends/meta-backend-private.h |  2 ++
 src/backends/meta-backend.c         | 23 +++++++++++++++++++++++
 src/compositor/compositor.c         |  8 ++++++++
 3 files changed, 33 insertions(+)
---
diff --git a/src/backends/meta-backend-private.h b/src/backends/meta-backend-private.h
index 80df654bc6..970ed451dc 100644
--- a/src/backends/meta-backend-private.h
+++ b/src/backends/meta-backend-private.h
@@ -202,4 +202,6 @@ void meta_backend_remove_hw_cursor_inhibitor (MetaBackend           *backend,
 
 gboolean meta_backend_is_hw_cursors_inhibited (MetaBackend *backend);
 
+void meta_backend_sync_pointer (MetaBackend *backend);
+
 #endif /* META_BACKEND_PRIVATE_H */
diff --git a/src/backends/meta-backend.c b/src/backends/meta-backend.c
index aca0d6fc99..1a1c589f4e 100644
--- a/src/backends/meta-backend.c
+++ b/src/backends/meta-backend.c
@@ -1612,3 +1612,26 @@ meta_backend_is_hw_cursors_inhibited (MetaBackend *backend)
 
   return FALSE;
 }
+
+void
+meta_backend_sync_pointer (MetaBackend *backend)
+{
+  MetaBackendPrivate *priv = meta_backend_get_instance_private (backend);
+  ClutterSeat *seat = clutter_backend_get_default_seat (priv->clutter_backend);
+  ClutterInputDevice *pointer = clutter_seat_get_pointer (seat);
+  ClutterModifierType modifiers;
+  ClutterEvent *event;
+  graphene_point_t pos;
+
+  event = clutter_event_new (CLUTTER_MOTION);
+  clutter_seat_query_state (seat, pointer, NULL, &pos, &modifiers);
+  clutter_event_set_flags (event, CLUTTER_EVENT_FLAG_SYNTHETIC);
+  clutter_event_set_coords (event, pos.x, pos.y);
+  clutter_event_set_device (event, pointer);
+  clutter_event_set_state (event, modifiers);
+  clutter_event_set_source_device (event, NULL);
+  clutter_event_set_stage (event, CLUTTER_STAGE (priv->stage));
+
+  clutter_event_put (event);
+  clutter_event_free (event);
+}
diff --git a/src/compositor/compositor.c b/src/compositor/compositor.c
index 3be8d2e9ee..104c0ed14c 100644
--- a/src/compositor/compositor.c
+++ b/src/compositor/compositor.c
@@ -440,6 +440,10 @@ meta_begin_modal_for_plugin (MetaCompositor   *compositor,
       meta_dnd_wayland_handle_begin_modal (compositor);
 #endif
     }
+  else
+    {
+      meta_backend_sync_pointer (meta_get_backend ());
+    }
 
   return TRUE;
 }
@@ -473,7 +477,11 @@ meta_end_modal_for_plugin (MetaCompositor *compositor,
       meta_dnd_wayland_handle_end_modal (compositor);
       meta_display_sync_wayland_input_focus (display);
     }
+  else
 #endif
+    {
+      meta_backend_sync_pointer (meta_get_backend ());
+    }
 
   g_signal_emit_by_name (display, "grab-op-end",
                          meta_plugin_get_display (plugin),