BansheeEngine/Documentation/Manuals/Native/User/advancedStartup.md

Advanced startup {#advancedStartup}

We have already shown how to perform basic start-up of a Banshee application.

Application::startUp(VideoMode(1280, 720), "My app", false);

// Set up your scene here

Application::instance().runMainLoop();
Application::shutDown();

This form of start-up is adequate for applications using only the scene object/component system for implementing game logic. Applications wishing to implement systems that aren't components must use a more advanced form of start up. Implementing systems in such a way is necessary when extending the engine with new features, using low level rendering API, or if its just a preference.

To perform advanced start-up you must create your own version of the Application class by deriving from it. Once derived you can override any of the following methods:

• @ref bs::Application::onStartUp "Application::onStartUp()" - Called when the application is first starting up.
• @ref bs::Application::preUpdate "Application::preUpdate()" - Called every frame, just before component and plugin updates are triggered.
• @ref bs::Application::postUpdate "Application::postUpdate()" - Called every frame, after component and plugin updates are triggered.

• @ref bs::Application::onShutDown "Application::onShutDown()" - Called just before the application is about to shut down.

  class MyApplication : public Application
  {
  public:
  	// Pass along the start-up structure to the parent
  	MyApplication(const START_UP_DESC& desc)
  		:Application(desc)
  	{ }
  
  private:
  	void onStartUp() override
  	{
  		// Ensure all parent systems are initialized first
  		Application::onStartUp();
  
  		// Do your own initialization (i.e. start your custom systems)
  	}
  
  	void onShutDown() override
  	{
  		// Do your own shut-down (i.e. shut down your custom systems)
  
  		// Shut-down engine components
  		Application::onShutDown();
  	}
  
  	void preUpdate() override
  	{
  		// Execute per-frame logic of your custom systems (optionally do it in postUpdate)
  	}
  };
  

Once you have your own application override, you can now start the application by calling @ref bs::Application::startUp "Application::startUp()" with the template parameter being your application override class. Everything else regarding start-up remains the same.

Application::startUp<MyApplication>(VideoMode(1280, 720), "My app", false);

// Set up your scene here

Application::instance().runMainLoop();
Application::shutDown();

Take a look at the ExampleLowLevelRendering for a working example of how to use advanced start-up in order to perform low-level rendering.