Using metrics in Language C with the SDL library

/*
* F2IBuilder - Font to Image Builder
* Example with SDL - Loading fonts generated for F2IBuilder
* Exemplo com SDL - Carregando fonts geradas pelo F2IBuilder
*/

#include <cstdlib>
#include <string>
#include <cstdarg>
#include <SDL/SDL.h>
#include <SDL/SDL_image.h>

Uint8* pKey = NULL;
SDL_Surface* screen = NULL;

struct fontBitmap
{
SDL_Surface* image;
char largura[256];
SDL_Rect area;
};

void initSDL(std::string title)
{
if (SDL_Init(SDL_INIT_VIDEO) < 0) {
    printf("Nao foi possivel inicializar SDL %s",SDL_GetError());
    exit(-1);
} else {
    screen=SDL_SetVideoMode(640, 480, 32, SDL_SWSURFACE);
    if (screen) {
        SDL_WM_SetCaption(title.c_str(),NULL);
    } else {
        printf("Couldn't set 640x480 video mode: %s\n",SDL_GetError());
        exit(-2);
    }
}
}

void shutdownSDL()
{
    SDL_Quit();
}

void updateInput()
{
    static SDL_Event event;
    SDL_PollEvent(&event);
    pKey = SDL_GetKeyState(NULL);
}

bool key(SDLKey key)
{
    if (pKey[key]){
        return true;
    } else {
        return false;
    }
}

void loadFont(fontBitmap* font,std::string filename)
{
    FILE *fileFont;
    font->image = IMG_Load(filename.c_str());
    std::string txt=""; 

    if(font!=NULL){
        txt=filename.substr(0,filename.length()-4);
        txt+=".dat";
        fileFont = fopen(txt.c_str(),"rb");
        if (fileFont!=NULL){
            fread(&font->largura, 256, 1, fileFont);
            fclose(fileFont);
        } else {
            for (int l=0;l<256;l++){
                font->largura[l] = font->image->w/16;
            }
        }
        font->area.w=font->image->w/16;
        font->area.h=font->image->h/16;
    }
}

void unloadFont(fontBitmap* font)
{
    if (font->image){
        SDL_FreeSurface(font->image);
    }
}

void writeFont(fontBitmap* font, int X, int Y, const char* WORD)
{
    int i,t=strlen(WORD);
    unsigned char l;

    SDL_Rect position;
    SDL_Rect size; 

    position.x=X;
    position.y=Y;

    for (i=0; i<t; i++){
        l=WORD[i];
        size.x=(l%16)*font->area.w; size.w=font->largura[l];
        size.y=(l/16)*font->area.h; size.h=font->area.h;
        SDL_BlitSurface(font->image, &size , screen, &position);
        position.y=Y;
        position.x=position.x+font->largura[l];
    }
}

void writeImprovedFont(fontBitmap* font, int X, int Y, const char* TEXT, ...)
{
    char texto_aux[256];
    va_list ap;
    va_start(ap, TEXT);
    vsprintf(texto_aux, TEXT, ap);
    va_end(ap);
    writeFont(font,X,Y,texto_aux);
}

int main(int argc, char *argv[])
{
    bool loop = true;
    initSDL("F2IBuilder - Exemplo C++");
    fontBitmap fontBitmap;

    loadFont(&fontBitmap,"font.png");

    while(loop) {

        updateInput();

        SDL_FillRect(screen, NULL, 700);

        writeImprovedFont(&fontBitmap,10,0,"F2IBuilder");
        writeImprovedFont(&fontBitmap,100,150,"Number:%d",10);
        writeImprovedFont(&fontBitmap,300,260,"PJMOO");
        writeImprovedFont(&fontBitmap,10,360,"Exemplo - Example");

        if (key(SDLK_ESCAPE)){
            loop = false;
        }

        SDL_Flip(screen);
    }
    unloadFont(&fontBitmap);
    shutdownSDL();

    return 0;
}