/**
 * Initialize an EGL context for the current display.
 */
int Engine::InitDisplay(android_app* app) {
  if (!initialized_resources_) {
    gl_context_->Init(app_->window);
    LoadResources();
    initialized_resources_ = true;
  } else if(app->window != gl_context_->GetANativeWindow()) {
    // Re-initialize ANativeWindow.
    // On some devices, ANativeWindow is re-created when the app is resumed
    assert(gl_context_->GetANativeWindow());
    UnloadResources();
    gl_context_->Invalidate();
    app_ = app;
    gl_context_->Init(app->window);
    LoadResources();
    initialized_resources_ = true;
  } else {
    // initialize OpenGL ES and EGL
    if (EGL_SUCCESS == gl_context_->Resume(app_->window)) {
      UnloadResources();
      LoadResources();
    } else {
        assert(0);
    }
  }

  ShowUI();

  // Initialize GL state.
  glEnable(GL_CULL_FACE);
  glEnable(GL_DEPTH_TEST);
  glDepthFunc(GL_LEQUAL);

  // Note that screen size might have been changed
  glViewport(0, 0, gl_context_->GetScreenWidth(),
             gl_context_->GetScreenHeight());
  renderer_.UpdateViewport();

  tap_camera_.SetFlip(1.f, -1.f, -1.f);
  tap_camera_.SetPinchTransformFactor(2.f, 2.f, 8.f);

  return 0;
}
void Engine::TrimMemory() {
  LOGI("Trimming memory");
  gl_context_->Invalidate();
}