688e5dd7c4
This is a "pseudo" base class. Basically it's a shared instance and class structure and a shared set of function between the two widget. It cannot have it's own type like normal base class since the one instance will implement GtkGLArea while the other implements GtkDrawingAreay. To workaround this, the parent instance and class is a union of both. https://bugzilla.gnome.org/show_bug.cgi?id=752441