(C++) SDL Mandelbrot set

#include <stdio.h>
#include <SDL2/SDL.h>
#include <SDL2/SDL_image.h>

static int scr_width;
static int scr_height;
static SDL_Window* winsource;
static SDL_Renderer* winrenderer;

struct Camera
{
    float xoffset, yoffset;
    double zoom;
    int detail;
    float colorshift;
};

static Camera cam;

struct ColorRGB
{
    unsigned char r,g,b;
};


void Init(int width, int height)
{
    // SDL Init
    SDL_Init(SDL_INIT_VIDEO);
    IMG_Init(IMG_INIT_PNG);

    // Create Window/Renderer
    scr_width = width;
    scr_height = height;
    cam.xoffset = 0;
    cam.yoffset = 0;
    cam.zoom = 2.5;
    cam.detail = 50;
    cam.colorshift = 1.0;

    winsource = SDL_CreateWindow("SDL Test",SDL_WINDOWPOS_CENTERED,SDL_WINDOWPOS_CENTERED,scr_width,scr_height,SDL_WINDOW_OPENGL);
    winrenderer = SDL_CreateRenderer(winsource, -1, SDL_RENDERER_ACCELERATED);
}

void SDLEnd()
{
    SDL_DestroyRenderer(winrenderer);
    SDL_DestroyWindow(winsource);
    SDL_Quit();
}

inline double nmap(double x, double from, double to, double mapfrom, double mapto)
{
    return (x-from)/(to-from) * (mapto-mapfrom) + mapfrom;
}

inline float hue2rgb(float p, float q, float t)
{
    if(t < 0) t += 1;
    if(t > 1) t -= 1;
    if(t < 1./6.) return p + (q - p) * 6 * t;
    if(t < 1./2.) return q;
    if(t < 2./3.) return p + (q - p) * (2./3. - t) * 6;
    return p;
}

ColorRGB hslToRgb(float h, float s, float l){
    float r, g, b;

    if(s == 0)
    {
        r = g = b = l; // achromatic
    }
    else
    {
        float q = (l < 0.5) ? (l * (1 + s)) : (l + s - l * s);
        float p = 2 * l - q;
        r = hue2rgb(p, q, h + 1./3.);
        g = hue2rgb(p, q, h);
        b = hue2rgb(p, q, h - 1./3.);
    }
    return (ColorRGB) {floor(r * 255), floor(g * 255), floor(b * 255)};
}


float MandleFind(double& xi, double& yi, int range, unsigned long inf)
{
    register int i;

    double oldxi = xi;
    double oldyi = yi;
    Camera oldcam = cam;

    for(i = 0; i < range; i++)
    {
        double xx = (xi*xi) - (yi*yi);
        double yy = 2 * xi * yi;
        xi = xx + oldxi;
        yi = yy + oldyi;
        if( abs(xx+yy) > inf) break;
    }
    float part = (float)i/range;
}

void Draw()
{
    ColorRGB pixel;
    #define dUpdateColor(h,l) pixel = hslToRgb(h,0.6,l); SDL_SetRenderDrawColor(winrenderer, pixel.r,pixel.g,pixel.b, 0xFF)
    dUpdateColor(0,1.0);

    for(int y = 0; y < scr_height; y++)
    {
        for(int x = 0; x < scr_width; x++)
        {
            double adir = nmap(x,0,scr_width,-cam.zoom,cam.zoom)+cam.xoffset;
            double bdir = nmap(y,0,scr_height,-cam.zoom,cam.zoom)+cam.yoffset;
            float mandleHit = MandleFind(adir,bdir,cam.detail,16);
            //printf("%f\n",mandleHit);
            dUpdateColor(cam.colorshift*mandleHit,0.5);

            SDL_RenderDrawPoint(winrenderer,x,y);
        }
    }
    SDL_RenderPresent(winrenderer);
}

void Update()
{
    SDL_Event ev;
    while(true)
    {
        SDL_PollEvent(&ev);
        double czoom = cam.zoom/2.5;
        if(ev.type == SDL_QUIT) break;
        if(ev.type == SDL_KEYDOWN)
        {
            SDL_Keycode skey = ev.key.keysym.sym;
            switch(skey)
            {
                case SDLK_LEFT:
                    cam.xoffset -= 0.2 * czoom;
                    Draw();
                break;
                case SDLK_RIGHT:
                    cam.xoffset += 0.2 * czoom;
                    Draw();
                break;
                case SDLK_UP:
                    cam.yoffset -= 0.2 * czoom;
                    Draw();
                break;
                case SDLK_DOWN:
                    cam.yoffset += 0.2 * czoom;
                    Draw();
                break;
                case SDLK_w:
                    cam.zoom *= 0.5;
                    cam.detail += 5;
                    Draw();
                break;
                case SDLK_s:
                    cam.zoom /= 0.5;
                    cam.detail -= 5;
                    Draw();
                break;
            }
        }
    }
}

int main()
{
    Init(320,200);
    Draw();
    Update();
    SDLEnd();
    return 0;
}