CIwGame Object – The Eye in the Sky

Introduction

CIwGame is basically the kind of eye-in-the-sky controller of the game engine and can be thought of as the main loop of the game engine. CIwGame takes care of many things including:

• Initialisation, processing and clean-up of many systems including graphics, input, resource manager and audio etc..
• Managing and updating scenes
• Sorting scenes by layer order
• Notifying the user of scene change events
• Rendering scenes
• Tracking frame speed
• Processing events such as tapped, touch begin / end

You never actually create an instance of CIwGame, instead you derive you own version of the class from CIwGame like this:

#define	GAME	Game::getInstance()

class Game : public CIwGame
{
	CDEFINE_SINGLETON(Game)
public:
protected:
	//// Properties
public:
	//// Properties end
protected:
public:
	void			Init(bool enable_http);
	void			Release();
	bool			Update();
	void			Draw();
	void			PostDraw();
	void			Save();
	void			Load();
};

You then implement Init(), Release(), Update() and Draw() methods to provide your own initialisation, clean-up, per frame update and per frame rendering code. You can also override PostDraw() to apply post rendering.

Note that the games Init() method takes a parameter called enable_http. If you plan on using anything relating to the HTTP manager, such as ads, web file / image access then you will need to pass true to the game object during initialisation.

Implementing our own CIwGame

Lets now take a quick look at a bare bones implementation of the above methods:

CDECLARE_SINGLETON(Game)

void Game::Init(bool enable_http)
{
	CIwGame::Init(enable_http);

	// TODO: Insert your own initialisation here
}

void Game::Release()
{
	// TODO: Insert your own cleanup here

	CIwGame::Release();
}

bool Game::Update()
{
	if (!CIwGame::Update())
		return false;

	// TODO: Insert your own custom game update functionality here

	return true;
}

void Game::Draw()
{
	CIwGame::Draw();

	// TODO: Insert your own custom game rendering functionality here
}

void Game::Save()
{
	// TODO: Insert your own game save functionality
}

void Game::Load()
{
	// TODO: Insert your own game load functionality
}

Note that if you utilise IwGames systems then it is very unlikely that you will need to add additional rendering code to Game::Draw().

At its heart, CIwGame contains a collection of game scenes (CIwGameScene’s) that in turn drive actors and cameras to provide your games functionality (more on these classes later).

CIwGame enables you to add, remove and search for scenes within the game as well as set the currently active scene using the following methods:

void		addScene(CIwGameScene *scene, bool bring_to_front = true);
void		removeScene(CIwGameScene* scene);
void		removeScene(unsigned int name_hash);
CIwGameScene*	findScene(unsigned int name_hash);
CIwGameScene*	findScene(const char* name);
CIwGameScene*	findScene(int type);
CIwGameScene*	getScene(int index);
void		clearScenes();
void		changeScene(CIwGameScene *new_scene);
bool		changeScene(unsigned int name_hash);
CIwGameScene*	getCurrentScene();
void		BringSceneToFront(CIwGameScene* scene);

Note that all visible scenes will be rendered every game frame and usually only the current scene will be updated.