SDLDrawable.cpp

#include "SDLDrawable.hpp"

SDLDrawable::SDLDrawable(int w, int h) : width(w), height(h)
{
    SDL_Init(SDL_INIT_VIDEO);
    screen = SDL_SetVideoMode(width, height, 32, SDL_SWSURFACE);
    if (SDL_MUSTLOCK(screen)) 
        SDL_LockSurface(screen);    
}

SDLDrawable::~SDLDrawable()
{
      SDL_Quit();
}

struct ColorTriplet
{
    unsigned char r;
    unsigned char g;
    unsigned char b;
};

// Assume ARGB order
ColorTriplet getColorTriplet(unsigned int color)
{
    return ColorTriplet {
        static_cast<unsigned char>(color << 8 >> 24),
        static_cast<unsigned char>(color << 16 >> 24),
        static_cast<unsigned char>(color << 24 >> 24)
    };
}

// Assume ARGB order
unsigned int getColor(const ColorTriplet& color)
{
    return 0xff000000 | (color.r << 16) | (color.g << 8) | color.b;
}

void SDLDrawable::updateScreen()
{
    if (SDL_MUSTLOCK(screen)) 
        SDL_UnlockSurface(screen);
        
    SDL_Flip(screen); 
    
    if (SDL_MUSTLOCK(screen)) 
        SDL_LockSurface(screen);
}

unsigned int SDLDrawable::getPixel(int x, int y) 
{
    auto pixel = *(reinterpret_cast<Uint32*>(screen->pixels) + y * width + x);
    ColorTriplet color;
    unsigned char alpha = 0;
    SDL_GetRGBA(pixel, screen->format, &color.r, &color.g, &color.b, &alpha);
    return getColor(color);
};

void SDLDrawable::setPixel(int x, int y, unsigned int color)
{
    auto colorTriplet = getColorTriplet(color);
    auto pixelPtr = reinterpret_cast<Uint32*>(screen->pixels) + y * width + x;
     *pixelPtr = SDL_MapRGBA(screen->format, colorTriplet.r, colorTriplet.g, colorTriplet.b, 255);
}