struct CanvasGL : GLCtrl {
    typedef CanvasGL CLASSNAME;

    virtual void GLPaint() {
        StdView();

        glLoadIdentity();
        glShadeModel(GL_SMOOTH);
        glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        // glClearDepth(1.0f);
    }
};

struct DialogGL : public TopWindow {
    typedef DialogGL CLASSNAME;

    DialogGL() {
        Add(canvasGL.SizePos());
    }

    void open() {
        if(!IsOpen()) {
            Open();
        }
    }

    void close() {
        if(IsOpen()) {
            Close();
        }
    }

private:
    CanvasGL canvasGL;
};