Function XPGetWidgetProperty 

pub unsafe extern "C" fn XPGetWidgetProperty(
    inWidget: XPWidgetID,
    inProperty: XPWidgetPropertyID,
    inExists: *mut c_int,
) -> isize

XPGetWidgetProperty

This routine returns the value of a widget’s property, or 0 if the property is not defined. If you need to know whether the property is defined, pass a pointer to an int for inExists; the existence of that property will be returned in the int. Pass NULL for inExists if you do not need this information.