Match an event with the control surfaces belonging to a widget
int PtCheckSurfaces( PtWidget_t *widget, PhPoint_t *point, PhEvent_t *event );
This function matches the given event with the control surfaces belonging to widget. If the event corresponds to a control surface, the surface's action is invoked.
PtCheckSurfaces() is usually called only from PtEventHandler(), although you can call it with a fake event if you need to.
PhEvent_t, PtEventHandler(), PhPoint_t
Control Surfaces chapter of the Photon Programmer's Guide