WIDGET_API XPWidgetID XPCreateCustomWidget(
                         int                  inLeft,    
                         int                  inTop,    
                         int                  inRight,    
                         int                  inBottom,    
                         int                  inVisible,    
                         const char *         inDescriptor,    
                         int                  inIsRoot,    
                         XPWidgetID           inContainer,    
                         XPWidgetFunc_t       inCallback);    

This function is the same as XPCreateWidget except that instead of passing a class ID, you pass your widget callback function pointer defining the widget. Use this function to define a custom widget. All parameters are the same as XPCreateWidget, except that the widget class has been replaced with the widget function.