SDL render perimiter

//http://www.youtube.com/user/thecplusplusguy
//render only the perimiter of SDL_Rect
#include <SDL/SDL.h>
#include <iostream>
#include <cmath>

void setPixel(int x,int y,int r,int g,int b)
{
    SDL_Surface* screen=SDL_GetVideoSurface();
    if(x>=0 && x<screen->w && y>=0 && y<=screen->h)
        ((Uint32*)screen->pixels)[y*screen->pitch/4+x]=SDL_MapRGB(screen->format,r,g,b);
}

void verticalLine(int y1,int y2,int x)
{
    for(int i=y1;i<y2;i++)
        setPixel(x,i,255,255,255);
}

void horizontalLine(int x1,int x2,int y)
{
    for(int i=x1;i<x2;i++)
        setPixel(i,y,255,255,255);
}

void renderPerimiter(SDL_Rect* rec)
{
    verticalLine(rec->y,rec->y+rec->h,rec->x);
    verticalLine(rec->y,rec->y+rec->h,rec->x+rec->w);
    horizontalLine(rec->x,rec->x+rec->w,rec->y);
    horizontalLine(rec->x,rec->x+rec->w,rec->y+rec->h);
}



int main(int argc, char** argv)
{
    SDL_Init(SDL_INIT_EVERYTHING);
    SDL_Surface *screen;
    screen = SDL_SetVideoMode(640, 480, 32, SDL_SWSURFACE);
//  screen = SDL_SetVideoMode(640, 480, 32, SDL_SWSURFACE|SDL_FULLSCREEN);
    bool running = true;
    const int FPS = 30;
    Uint32 start;
    SDL_Rect rect;
    rect.x = 10;
    rect.y = 10;
    rect.w = 20;
    rect.h = 20;
    Uint32 color = SDL_MapRGB(screen->format, 0,0,0);
    Uint32 color2 = SDL_MapRGB(screen->format, 0,0,0);
    int x=0,y=0;
    while(running) {
        start = SDL_GetTicks();
        SDL_Event event;
        while(SDL_PollEvent(&event)) {
            switch(event.type) {
                case SDL_QUIT:
                    running = false;
                    break;
            }
        }
        //logic && render

        SDL_FillRect(screen, &screen->clip_rect, color);
        //SDL_FillRect(screen, &rect, color2);
        renderPerimiter(&rect);
        SDL_Flip(screen);

        if(1000/FPS > SDL_GetTicks()-start) {
            SDL_Delay(1000/FPS-(SDL_GetTicks()-start));
        }
    }
    SDL_Quit();
    return 0;
}