From X-Plane SDK
WIDGET_API void XPSetWidgetDescriptor( XPWidgetID inWidget, const char * inDescriptor);Every widget has a descriptor, which is a text string. What the text string is used for varies from widget to widget; for example, a push button's text is its descriptor, a caption shows its descriptor, and a text field's descriptor is the text being edited. In other words, the usage for the text varies from widget to widget, but this API provides a universal and convenient way to get at it. While not all UI widgets need their descriptor, many do.