#include "Scene.hpp"

// OpenGL.
#include <qgl.h>

// With this (conservative) work-around, I was able to scale the
// projection matrix how painter->beginNativePainting() would do
// in case it failed (for systems with OpenGL 3.1).
//#define WORKAROUND_FOR_MY_PROBLEM

Scene::Scene(QWidget *parent)
   : QGraphicsScene(parent)
{
}

Scene::~Scene()
{
}

void Scene::drawBackground(QPainter *painter, const QRectF &rect)
{

#ifdef WORKAROUND_FOR_MY_PROBLEM
   static bool CALL_ONLY_ONCE_FLAG = true;
   if(CALL_ONLY_ONCE_FLAG)
   {
      painter->beginNativePainting();
      {
         const GLdouble identityMatrix[16] = {1., 0., 0., 0.,
                                              0., 1., 0., 0.,
                                              0., 0., 1., 0.,
                                              0., 0., 0., 1.};
         GLdouble projectionMatrix[16] = {0., 0., 0., 0.,
                                          0., 0., 0., 0.,
                                          0., 0., 0., 0.,
                                          0., 0., 0., 0.};
         glGetDoublev (GL_PROJECTION_MATRIX, projectionMatrix);

         // Check if projection matrix is identity.
         if(memcmp(projectionMatrix, identityMatrix, 16) == 0)
         {
            const int w = painter->device()->width();
            const int h = painter->device()->height();

            {
               // This is the Qt way of setting the viewport and perspective.
               // Compare with opengl/qpaintengine_opengl.cpp.
               glPushMatrix();
               glViewport(0, 0, w, h);
               glMatrixMode(GL_PROJECTION);
               glLoadIdentity();
               glOrtho(0, w, h, 0, -999999, 999999);
               glMatrixMode(GL_MODELVIEW);
               glPopMatrix();
            }
         }
      }
      painter->endNativePainting();

      // In any case, pass by here only once!
      CALL_ONLY_ONCE_FLAG = false;
   }
#endif // WORKAROUND_FOR_MY_PROBLEM


   // Regardless of the scanning state, set the back-ground color.
   painter->beginNativePainting();
   {
      // Clear the buffers.
      glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
      glClear(GL_COLOR_BUFFER_BIT |
              GL_DEPTH_BUFFER_BIT |
              GL_STENCIL_BUFFER_BIT);

      // Do other native painting...
      //
      //
      // ...
   }
   painter->endNativePainting();
}

//#inlude "Scene.moc"