PFNGLSHADERSOURCEPROCDart typedef
        PFNGLSHADERSOURCEPROCDart =
     void Function(int shader, int count, Pointer<Pointer<Int8> >  string, Pointer<Int32>  length)
    
    
    
Implementation
typedef PFNGLSHADERSOURCEPROCDart =
    void Function(
      int shader,
      int count,
      Pointer<Pointer<Int8>> string,
      Pointer<Int32> length,
    );