// create the data for the derived class here
virtual wxGDIImageRefData *CreateData() const = 0;
virtual wxGDIRefData *CreateGDIRefData() const { return CreateData(); }
// create the data for the derived class here
virtual wxGDIImageRefData *CreateData() const = 0;
virtual wxGDIRefData *CreateGDIRefData() const { return CreateData(); }