/**
  * Initialize the compilation by:
  * 
  * * 1. Spawning public and private compilation directoryies.
  * * 2. Instantiating appropriate rendering engine and CSS utilities.
  * 
  * for the next compilation process.
  */
 protected function initCompilation()
 {
     $ds = DIRECTORY_SEPARATOR;
     // Initialize public and private compilation directories.
     $this->setPrivateDirectory($this->spawnPrivateDirectory());
     $this->setPublicDirectory($this->spawnPublicDirectory());
     // Extra path.
     $testService = taoQtiTest_models_classes_QtiTestService::singleton();
     $testDefinitionDir = dirname($testService->getRelTestPath($this->getResource()));
     $this->setExtraPath($testDefinitionDir);
     // Initialize rendering engine.
     $renderingEngine = new XhtmlRenderingEngine();
     $renderingEngine->setStylesheetPolicy(XhtmlRenderingEngine::STYLESHEET_SEPARATE);
     $renderingEngine->setXmlBasePolicy(XhtmlRenderingEngine::XMLBASE_PROCESS);
     $renderingEngine->setFeedbackShowHidePolicy(XhtmlRenderingEngine::TEMPLATE_ORIENTED);
     $renderingEngine->setViewPolicy(XhtmlRenderingEngine::TEMPLATE_ORIENTED);
     $renderingEngine->setPrintedVariablePolicy(XhtmlRenderingEngine::TEMPLATE_ORIENTED);
     $renderingEngine->setStateName(TAOQTITEST_RENDERING_STATE_NAME);
     $renderingEngine->setRootBase(TAOQTITEST_PLACEHOLDER_BASE_URI . rtrim($this->getExtraPath(), $ds));
     $renderingEngine->setViewsName(TAOQTITEST_VIEWS_NAME);
     $this->setRenderingEngine($renderingEngine);
     // Initialize CSS Scoper.
     $this->setCssScoper(new CssScoper());
     // Initialize Post Markup Renderer.
     $this->setMarkupPostRenderer(new MarkupPostRenderer(true, true, true));
 }