WIDGET_API int        XPUDragWidget(
                         XPWidgetMessage      inMessage,    
                         XPWidgetID           inWidget,    
                         intptr_t             inParam1,    
                         intptr_t             inParam2,    
                         int                  inLeft,    
                         int                  inTop,    
                         int                  inRight,    
                         int                  inBottom);    

XPUDragWidget drags the widget in response to mouse clicks. Pass in not only the event, but the global coordinates of the drag region, which might be a sub-region of your widget (for example, a title bar).