clutter: Add ClutterSeat private API to grab devices

This will be necessary to string along ClutterGrab with backend
behavior, and mostly for the X11 backend so implement this pair
of vfuncs there.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2068>

clutter/clutter/clutter-enums.h

@@ -1628,6 +1628,15 @@ typedef enum
   CLUTTER_PHASE_BUBBLE,
 } ClutterEventPhase;
 
+typedef enum
+{
+  CLUTTER_GRAB_STATE_NONE = 0,
+  CLUTTER_GRAB_STATE_POINTER = 1 << 0,
+  CLUTTER_GRAB_STATE_KEYBOARD = 1 << 1,
+  CLUTTER_GRAB_STATE_ALL = (CLUTTER_GRAB_STATE_POINTER |
+                            CLUTTER_GRAB_STATE_KEYBOARD),
+} ClutterGrabState;
+
 G_END_DECLS
 
 #endif /* __CLUTTER_ENUMS_H__ */

clutter/clutter/clutter-seat-private.h

@@ -28,4 +28,9 @@
 CLUTTER_EXPORT
 void clutter_seat_destroy (ClutterSeat *seat);
 
+ClutterGrabState clutter_seat_grab (ClutterSeat *seat,
+                                    uint32_t     time);
+void clutter_seat_ungrab (ClutterSeat *seat,
+                          uint32_t     time);
+
 #endif /* CLUTTER_SEAT_PRIVATE_H */

clutter/clutter/clutter-seat.c

@@ -705,3 +705,27 @@ clutter_seat_destroy (ClutterSeat *seat)
   g_object_run_dispose (G_OBJECT (seat));
   g_object_unref (seat);
 }
+
+ClutterGrabState
+clutter_seat_grab (ClutterSeat *seat,
+                   uint32_t     time)
+{
+  ClutterSeatClass *seat_class;
+
+  seat_class = CLUTTER_SEAT_GET_CLASS (seat);
+  if (seat_class->grab)
+    return seat_class->grab (seat, time);
+  else
+    return CLUTTER_GRAB_STATE_ALL;
+}
+
+void
+clutter_seat_ungrab (ClutterSeat *seat,
+                     uint32_t     time)
+{
+  ClutterSeatClass *seat_class;
+
+  seat_class = CLUTTER_SEAT_GET_CLASS (seat);
+  if (seat_class->ungrab)
+    return seat_class->ungrab (seat, time);
+}

clutter/clutter/clutter-seat.h

@@ -97,6 +97,11 @@ struct _ClutterSeatClass
                             graphene_point_t     *coords,
                             ClutterModifierType  *modifiers);
 
+  ClutterGrabState (* grab) (ClutterSeat *seat,
+                             uint32_t     time);
+  void (* ungrab) (ClutterSeat *seat,
+                   uint32_t     time);
+
   /* Virtual devices */
   ClutterVirtualInputDevice * (* create_virtual_device) (ClutterSeat            *seat,
                                                          ClutterInputDeviceType  device_type);

src/backends/x11/meta-seat-x11.c

@@ -71,6 +71,7 @@ struct _MetaSeatX11
   int pointer_id;
   int keyboard_id;
   int opcode;
+  ClutterGrabState grab_state;
   guint has_touchscreens : 1;
   guint touch_mode : 1;
   guint has_pointer_focus : 1;
@@ -1652,6 +1653,56 @@ meta_touch_info_free (MetaTouchInfo *touch_info)
   g_free (touch_info);
 }
 
+static ClutterGrabState
+meta_seat_x11_grab (ClutterSeat *seat,
+                    uint32_t     time)
+{
+  MetaSeatX11 *seat_x11 = META_SEAT_X11 (seat);
+  MetaBackend *backend = meta_get_backend ();
+  ClutterGrabState state = CLUTTER_GRAB_STATE_NONE;
+
+  g_return_val_if_fail (seat_x11->grab_state == CLUTTER_GRAB_STATE_NONE,
+                        seat_x11->grab_state);
+
+  if (meta_backend_grab_device (backend,
+                                META_VIRTUAL_CORE_POINTER_ID,
+                                time))
+    state |= CLUTTER_GRAB_STATE_POINTER;
+
+  if (meta_backend_grab_device (backend,
+                                META_VIRTUAL_CORE_KEYBOARD_ID,
+                                time))
+    state |= CLUTTER_GRAB_STATE_KEYBOARD;
+
+  seat_x11->grab_state = state;
+
+  return state;
+}
+
+static void
+meta_seat_x11_ungrab (ClutterSeat *seat,
+                      uint32_t     time)
+{
+  MetaSeatX11 *seat_x11 = META_SEAT_X11 (seat);
+  MetaBackend *backend = meta_get_backend ();
+
+  if ((seat_x11->grab_state & CLUTTER_GRAB_STATE_POINTER) != 0)
+    {
+      meta_backend_ungrab_device (backend,
+                                  META_VIRTUAL_CORE_POINTER_ID,
+                                  time);
+    }
+
+  if ((seat_x11->grab_state & CLUTTER_GRAB_STATE_KEYBOARD) != 0)
+    {
+      meta_backend_ungrab_device (backend,
+                                  META_VIRTUAL_CORE_KEYBOARD_ID,
+                                  time);
+    }
+
+  seat_x11->grab_state = CLUTTER_GRAB_STATE_NONE;
+}
+
 static void
 meta_seat_x11_class_init (MetaSeatX11Class *klass)
 {
@@ -1673,6 +1724,8 @@ meta_seat_x11_class_init (MetaSeatX11Class *klass)
   seat_class->warp_pointer = meta_seat_x11_warp_pointer;
   seat_class->handle_event_post = meta_seat_x11_handle_event_post;
   seat_class->query_state = meta_seat_x11_query_state;
+  seat_class->grab = meta_seat_x11_grab;
+  seat_class->ungrab = meta_seat_x11_ungrab;
 
   props[PROP_OPCODE] =
     g_param_spec_int ("opcode",