/**
 * Just the current frame in the display.
 */
void Engine::DrawFrame() {
  float fps;
  if (monitor_.Update(fps)) {
    UpdateFPS(fps);
  }
  renderer_.Update(monitor_.GetCurrentTime());

  // Just fill the screen with a color.
  glClearColor(0.5f, 0.5f, 0.5f, 1.f);
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  renderer_.Render();

  // Swap
  if (EGL_SUCCESS != gl_context_->Swap()) {
    UnloadResources();
    LoadResources();
  }
}