XPCreateCustomWidget
From X-Plane SDK
XPCreateCustomWidget
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.