4.6 How to render a multitextured cube in OpenGL?

/*
 * MultiJPGTexturedCubeRotationByKeyInput.cpp 
 * Copyright (c) 2015 Antillia.com TOSHIYUKI ARAI. ALL RIGHTS RESERVED. 
 */


//2016/07/20
//2016/08/03 Updated.

#include <sol/opengl/OpenGLMainView.h>
#include <sol/opengl/OpenGLView.h>
#include <sol/opengl/OpenGLGC.h>
#include <sol/opengl/OpenGLMultiTexturedCube.h>

namespace SOL {

class MainView :public OpenGLMainView {

private:
  //Inner class starts.

  class SimpleView: public OpenGLView {
  private:
    SmartPtr<OpenGLGC>                gc;
    SmartPtr<OpenGLMultiTexturedCube> cube;
    float  angle;
    
  public:
    virtual void display()
    {
      if (gc && cube) {    
        gc -> clear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        gc -> clearColor(1.0f, 1.0f, 1.0f, 1.0f);

        gc -> loadIdentity();
        gc -> translate(0.0f,0.0f,-1.0f); 
        gc -> lookAt(2.0, 6.0, 10.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0); 

        //Rotation around y-axis.
        gc -> rotate(angle, 0.0, 1.0, 0.0);

        cube -> draw(gc);
      }
    }
  
 
    virtual void resize(int w, int h)
    {
      if (w == 0 || h == 0) {
        return;
      }
      if (gc) {
        gc -> matrixMode(GL_PROJECTION);
        gc -> loadIdentity();
        gc -> perspective(16.0, (double)w / (double)h, 0.5, 40.0); 

        gc -> matrixMode(GL_MODELVIEW);        
      }
    }

    virtual void initialize()
    {
      gc = new OpenGLGC();
      gc -> enable(GL_DEPTH_TEST);
      gc -> enable(GL_TEXTURE_2D);
      try {
        static const char* jpgFiles[] = {
           "./images/1.jpg", "./images/2.jpg", "./images/3.jpg", 
           "./images/4.jpg", "./images/5.jpg", "./images/6.jpg", 
         };
        
        cube = new OpenGLMultiTexturedCube(6, jpgFiles);
        
      } catch (Exception& ex) {
        caught(ex);
      }
    }


    virtual void keyDown(Event& event)
    {
      WPARAM vkey = event.getWParam();
      switch (vkey) {
      case VK_LEFT:
        angle -= 2.0;
        postRenderRequest();
        break;
      case VK_RIGHT:
        angle += 2.0;
        postRenderRequest();
        break;
      default:
        break;
      }
    }
    
  public:
    SimpleView(View* parent, const char* name, Args& args)
    :OpenGLView(parent, name, args),
    angle(0.0)
    {
    } 

    ~SimpleView()
    {
    }
  };
  //Inner class ends.
  
private:
  SmartPtr<SimpleView>  view;

  long size(Event& event)
  {
    int w, h;
    event.getSize(w, h);
    if (view) {
      view -> reshape(10.0f, 10.0f, w-20, h-20);
      view -> postResizeRequest(w-20, h-20);
    }
    return 1L;
  }

  virtual long keyDown(Event& event)
  {
    if (view) {
      view -> keyDown(event);
    }
    return 0;
  }
  
public:
  MainView(Application& applet, const char* name, Args& args)
  :OpenGLMainView(applet, name, args)
  {
    addEventHandler(WM_KEYDOWN, this,
              (Handler)&MainView::keyDown, NULL);

    Args ar;
    view = new SimpleView(this, "", ar);
  }

  ~MainView()
  {
  }
};
}

//
void Main(int argc, char** argv) 
{
  try {
    const char*  name = appName(argv[0]);
    Application applet(name, argc, argv);

    Args args;
    args.set(XmNwidth,  480);
    args.set(XmNheight, 480);

    MainView view(applet, name, args);
    view.realize();

    applet.run();
    
  } catch (Exception& ex) {
    caught(ex);
  }
}