PFNGLCOPYTEXTURESUBIMAGE2DPROCDart typedef
        PFNGLCOPYTEXTURESUBIMAGE2DPROCDart =
     void Function(int texture, int level, int xoffset, int yoffset, int x, int y, int width, int height)
    
    
    
Implementation
typedef PFNGLCOPYTEXTURESUBIMAGE2DPROCDart =
    void Function(
      int texture,
      int level,
      int xoffset,
      int yoffset,
      int x,
      int y,
      int width,
      int height,
    );