Color gradient.

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#include <sdl/sdl.h>

#ifdef WIN32
#pragma comment(lib,"sdl.lib")
#pragma comment(lib,"sdlmain.lib")
#endif

void UpdateEvents(Sint32* mousex,Sint32* mousey,char boutons[8],char key[SDLK_LAST])
{
    SDL_Event event;
    while(SDL_PollEvent(&event))
    {
        switch (event.type)
        {
        case SDL_KEYDOWN:
            key[event.key.keysym.sym]=1;
            break;
        case SDL_KEYUP:
            key[event.key.keysym.sym]=0;
            break;
        case SDL_MOUSEMOTION:
            *mousex=event.motion.x;
            *mousey=event.motion.y;
            break;
        case SDL_MOUSEBUTTONDOWN:
            boutons[event.button.button]=1;
            break;
        case SDL_MOUSEBUTTONUP:
            boutons[event.button.button]=0;
            break;
        }
    }
}

void SDL_PutPixel32(SDL_Surface *surface, int x, int y, Uint32 pixel)
{
    Uint8 *p = (Uint8*)surface->pixels + y * surface->pitch + x * 4;
    *(Uint32*)p = pixel;
}

Uint32 SDL_GetPixel32(SDL_Surface *surface, int x, int y)
{
    Uint8 *p = (Uint8*)surface->pixels + y * surface->pitch + x * 4;
    return *(Uint32*)p;
}

int main(int argc,char** argv)
{
    Sint32 mousex = 0;
    Sint32 mousey = 0;
    char boutons[8] = {0};
    char key[SDLK_LAST] = {0};
    SDL_Surface* screen;
    int i,j;
    unsigned char currentblue = 0;
    SDL_Init(SDL_INIT_VIDEO);
    screen=SDL_SetVideoMode(256,256,32,SDL_SWSURFACE|SDL_DOUBLEBUF);  
    SDL_ShowCursor(1);
    while(!key[SDLK_ESCAPE])
    {
        UpdateEvents(&mousex,&mousey,boutons,key);
        if (SDL_MUSTLOCK(screen))
            SDL_LockSurface(screen);
        for(i=0;i<256;i++)
            for(j=0;j<256;j++)
            {
                SDL_PutPixel32(screen,i,j,SDL_MapRGBA(screen->format,i,j,currentblue,0));
            }
        currentblue++;
        if (SDL_MUSTLOCK(screen))
            SDL_UnlockSurface(screen);        
        SDL_Flip(screen);
    }
    return 0;
}

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