contains_pointer
Description:
Whether the pointer of a Drag-and-Drop operation is in the controller's widget or a descendant.
See also [property@Gtk.DropControllerMotion:is-pointer].
When handling crossing events, this property is updated before [signal@Gtk.DropControllerMotion:GtkDropControllerMotion:enter],
but after [signal@Gtk.DropControllerMotion:GtkDropControllerMotion:leave] is emitted.