Function XPGetNthChildWidget 

pub unsafe extern "C" fn XPGetNthChildWidget(
    inWidget: XPWidgetID,
    inIndex: c_int,
) -> XPWidgetID

XPGetNthChildWidget

This routine returns the widget ID of a child widget by index. Indexes are 0 based, from 0 to the number of widgets in the parentone minus one, inclusive. If the index is invalid, 0 is returned.