ATL style templating and inheritance with "no virtuals".

.gitignore

*.swp
cppsdl

cppsdl.cpp

/*
	Sample: ATL style templating and inheritance with "no virtuals"
	almost for free :)

	Copyright (c) 2011, Mihail Szabolcs

	Released into the public domain.

	Compile & Run:
		make; ./cppsdl
*/
#include <SDL.h>

struct RectS
{
	short x, y;
	unsigned short w, h;
};

template< typename T >
class WindowI
{
public:
	void setTitle(const char *pTitle)
	{
		static_cast<T *>(this)->onSetTitle(pTitle);
	}
	bool setVideMode(int pWidth, int pHeight, int pBpp)
	{
		return static_cast<T *>(this)->onSetVideoMode(pWidth, pHeight, pBpp);
	}
	int exec(void)
	{
		T *self = static_cast<T *>(this);

		bool done = false;
		while(!done)
		{
			while(self->onPollMessages())
			{
				if(self->onProcessMessages())
				{
					done = true;
					break;
				}
			}

			self->onUpdate();
			self->onDraw();
			self->onSwapBuffers();
			
			//
			// sleep 10 ms
			//
			// Notes:
			// in a production app, especially when "rendering"
			// we should calculate the "delta" and sleep the
			// necessary amount in order to synch up with our 
			// 'fixed' time-step (i.e => FPS, 1000 sec/30 fps = 33.33 ms) or such :)
			//
			self->onSleep(10);
		}

		return EXIT_SUCCESS;
	}
	void clear(unsigned short pR, unsigned short pG, unsigned short pB, unsigned short pA)
	{
		static_cast<T *>(this)->onClear(pR, pG, pB, pA);
	}
	void fill(RectS *pRect, unsigned short pR, unsigned short pG, unsigned short pB, unsigned short pA)
	{
		static_cast<T *>(this)->onFill(pRect, pR, pG, pB, pA);
	}

protected:
	bool onPollMessages(void)
	{
		return true;
	}
	bool onProcessMessages(void)
	{
		return true;
	}
	void onSetTitle(const char *pTitle)
	{
		// empty
	}
	bool onSetVideoMode(int pWidth, int pHeight, int pBpp)
	{
		return false;
	}
	void onUpdate(void)
	{
		// empty
	}
	void onDraw(void)
	{
		// empty
	}
	void onSwapBuffers(void)
	{
		// empty
	}
	void onSleep(unsigned int pMs)
	{
		// empty
	}
	void onClear(unsigned short pR, unsigned short pG, unsigned short pB, unsigned short pA)
	{
		// empty
	}
	void onFill(RectS *pRect, unsigned short pR, unsigned short pG, unsigned short pB, unsigned short pA)
	{
		// empty
	}
};

template< typename T >
class SDLWindowC: public WindowI< SDLWindowC<T> >
{
	friend class WindowI< SDLWindowC<T> >;

protected:
	SDLWindowC(void) : mScreen(NULL)
	{
		SDL_Init(SDL_INIT_VIDEO);
	}
	
	~SDLWindowC(void)
	{
		SDL_Quit();
	}

	bool onSetVideoMode(int pWidth, int pHeight, int pBpp)
	{
		mScreen = SDL_SetVideoMode(pWidth, pHeight, pBpp, SDL_SWSURFACE);
		return (mScreen != NULL);
	}

	bool onPollMessages(void)
	{
		return SDL_PollEvent(&mEvent) == 1;
	}

	bool onProcessMessages(void)
	{
		return mEvent.type == SDL_QUIT;
	}

	void onSetTitle(const char *pTitle)
	{
		SDL_WM_SetCaption(pTitle, pTitle);
	}

	void onSwapBuffers(void)
	{
		SDL_Flip(mScreen);
	}

	void onSleep(unsigned int pMs)
	{
		SDL_Delay(pMs); 
	}

	void onClear(unsigned short pR, unsigned short pG, unsigned short pB, unsigned short pA)
	{
		SDL_FillRect(mScreen, &mScreen->clip_rect, SDL_MapRGBA(mScreen->format, pR, pG, pB, pA));
	}

	void onDraw(void)
	{
		return static_cast<T *>(this)->onDraw();
	}

	void onUpdate(void)
	{
		return static_cast<T *>(this)->onUpdate();
	}

	void onFill(RectS *pRect, unsigned short pR, unsigned short pG, unsigned short pB, unsigned short pA)
	{
		// FIXME: memcpy
		SDL_Rect rect;
		rect.x = pRect->x;
		rect.y = pRect->y;
		rect.w = pRect->w;
		rect.h = pRect->h;

		SDL_FillRect(mScreen, &rect, SDL_MapRGBA(mScreen->format, pR, pG, pB, pA));
	}

private:
	SDL_Surface *mScreen;
	SDL_Event mEvent;
};

class DemoC : public SDLWindowC<DemoC> 
{
	friend class SDLWindowC<DemoC>;

public:
	DemoC(void)
	{
		mRect.x = 100;
		mRect.y = 100;
		mRect.w = 100;
		mRect.h = 200;

		mRnd = 0;
	}
	
protected:
	void onDraw(void)
	{
		clear(120, 55, 23, 255);
		fill(&mRect, 200, 120, 200, 255);
	}

	void onUpdate(void)
	{
		if(++mRnd > 50)
		{
			mRect.x = rand() % 200;
			mRect.y = rand() % 200;
			mRnd = 0;
		}
	}

private:
	RectS mRect;
	unsigned int mRnd;
};

int main(int argc, char *argv[])
{
	DemoC demo;
	if(demo.setVideMode(800, 600, 32))
	{
		demo.setTitle("SDL Demo");
		return demo.exec();
	}

	return 0;
}

Makefile

SDL=`sdl-config --cflags --libs`

all:
	g++ cppsdl.cpp -Wall -o cppsdl $(SDL)

clean:
	rm -f cppsdl
	
distclean: clean
realclean: clean

.PHONY: all clean distclean realclean