Tell the widget library about a change in visibility
PtUpdateVisibility( PtWidget_t *widget, PhRect_t *rect );
This function tells the widget library that a change has occurred that may affect the visibility of widgets that intersect with the provided rect in the given container widget. This change may make the intersecting widgets completely obscured, completely unobscured, or partially obscured. This information is used to optimize refreshing the screen:
0 on success; -1 if widget isn't a container.
PhRect_t in the Photon Library Reference