cursor-tracker: Add way to force tracking cursor position

On X11 we won't always receive cursor positions, as some other client
might have grabbed the pointer (e.g. for implementing a popup menu). To
make screen casting show a somewhat correct cursor position, we need to
actively poll the X server about the current cursor position.

We only really want to do this when screen casting or taking a
screenshot, so add an API that forces the cursor tracker to track the
cursor position.

On the native backend this is a no-op as we by default always track the
cursor position anyway.

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1391

src/backends/meta-cursor-tracker-private.h

@@ -30,6 +30,9 @@
 struct _MetaCursorTrackerClass
 {
   GObjectClass parent_class;
+
+  void (* set_force_track_position) (MetaCursorTracker *tracker,
+                                     gboolean           is_enabled);
 };
 
 gboolean meta_cursor_tracker_handle_xevent (MetaCursorTracker *tracker,
@@ -45,6 +48,10 @@ void     meta_cursor_tracker_update_position (MetaCursorTracker *tracker,
                                               float              new_x,
                                               float              new_y);
 
+void meta_cursor_tracker_track_position (MetaCursorTracker *tracker);
+
+void meta_cursor_tracker_untrack_position (MetaCursorTracker *tracker);
+
 MetaCursorSprite * meta_cursor_tracker_get_displayed_cursor (MetaCursorTracker *tracker);
 
 #endif