+ NO_SIZE_NEGOTIATION = 1<<3, ///< True if control does not need size negotiation, i.e. it can be skipped in the algorithm
+ REQUIRES_HOVER_EVENTS = 1<<4, ///< True if the OnHoverEvent() callback is required.
+ REQUIRES_MOUSE_WHEEL_EVENTS = 1<<5 ///< True if the OnMouseWheelEvent() callback is required.