Hello all I am refreshing my kwoledge on SDL, using Lazy foo tutorials, and I need to code all my projects for SDL in C. So I convert all his C++ code to C. Bet I have serious issue in 12th tutorial about timing. Here is my code:
[source lang="cpp"]#include "SDL/SDL.h"
#include "SDL/SDL_image.h"
#include "SDL/SDL_ttf.h"

const int SCREEN_WIDTH = 640;
const int SCREEN_HEIGHT = 480;
const int SCREEN_BPP = 32;

SDL_Surface* message = NULL;
SDL_Surface* seconds = NULL;
SDL_Surface *background = NULL;
SDL_Surface *screen = NULL;
SDL_Event event;

TTF_Font* font = NULL;
SDL_Color textColor = {255,0,0};//white, same 0xff,0xff,0xff

SDL_Surface *load_image( char *filename )
{
SDL_Surface* loadedImage = NULL;
SDL_Surface* optimizedImage = NULL;
loadedImage = IMG_Load( filename );
if( loadedImage != NULL )
{
optimizedImage = SDL_DisplayFormat( loadedImage );
SDL_FreeSurface( loadedImage );
if (optimizedImage != NULL)
{
//map the color key
Uint32 colorkey = SDL_MapRGB(optimizedImage->format, 0,0xFF,0xFF);
//sets all pixels of color R0, G 0xFF, B 0xFF to be tranparent
SDL_SetColorKey(optimizedImage, SDL_SRCCOLORKEY, colorkey);
}
}
return optimizedImage;
}
void apply_surface( int x, int y, SDL_Surface* source, SDL_Surface* destination )
{
SDL_Rect offset;
offset.x = x;
offset.y = y;
SDL_BlitSurface( source, NULL, destination, &offset );
}

int init(char * caption)
{
if( SDL_Init( SDL_INIT_EVERYTHING ) == -1 )
{
return 0;
}
screen = SDL_SetVideoMode( SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP, SDL_SWSURFACE);
if( screen == NULL )
{
return 0;
}
//initiliaze SDL_ttf
if (TTF_Init() == -1)
{
return 0;
}
SDL_WM_SetCaption( caption, NULL );
return 1;
}
int load_files()
{
background = load_image("background.png");
//open the font
font = TTF_OpenFont("lazy.ttf",30);
if( background == NULL )
{
return 0;
}
if( font == NULL )
{
return 0;
}
return 1;
}
void clean_up()
{
SDL_FreeSurface( background );
SDL_FreeSurface( message );
TTF_CloseFont(font);

TTF_Quit();
SDL_Quit();
}

int main( int argc, char* args[] )
{
int quit = 0;//make sure program waits for quit

//the timer starting time
Uint32 start = 0;

//the timer start/stop flag
int running = 0;

if( init("Simple timer") == 0 )return 1;

if(load_files() == 0) return 1;

message = TTF_RenderText_Solid(font,"Press s to start/stop the timer", textColor);
if (message == 0) return 1;

//start the timer
start = SDL_GetTicks();

//main loop
while (!quit)//while user hasnt quit
{
//while there's event to handle!
while(SDL_PollEvent(&event))
{
//if user has Xed out
if(event.type == SDL_QUIT)
{
//quit the program
quit = 1;
}
else if(event.type == SDL_KEYDOWN)
{
if(event.key.keysym.sym == SDLK_s)
{
//if timer is running
if(running)
{
//stop the timer
running = 0;
start = 0;
}
else
{
//start the timer
running = 1;
start = SDL_GetTicks();
}
}
else if(event.key.keysym.sym == SDLK_ESCAPE)
{
quit = 1;
}
}
//rendering
apply_surface(0,0,background,screen);
apply_surface((SCREEN_WIDTH - message->w)/2,SCREEN_HEIGHT/2,message,screen);

//if the timer is running
if(running)
{
//timer: as a string
char* time = "Timer: ";
//current time as a string
char* current = 0;
//convert timers time to a string
itoa((SDL_GetTicks() - start), current, 10);
//adds time (Timer: ) + time in ms
strcat(time, current);
//renders the time surface
seconds = TTF_RenderText_Solid(font, time, textColor);
//apply the times surface
apply_surface((SCREEN_WIDTH - seconds->w)/2,50,seconds,screen);
SDL_FreeSurface(seconds);
}

//updating
if( SDL_Flip( screen ) == -1 )
{
return 1;
}
}
}
clean_up();
return 0;
}
[/source]
It doesn't have any compile or link errors, I can launch it, surfaces loads, but when I press 's'(to start/stop timer) it suddenly quits. I don't have idea what the problem might be, but I think issue in my "C version" of converting SDL time to string (Lazy Foo used string streams to handle this). This is the code where I used some standart C functions for doing so:
[source lang="cpp"]//rendering
apply_surface(0,0,background,screen);
apply_surface((SCREEN_WIDTH - message->w)/2,SCREEN_HEIGHT/2,message,screen);

//if the timer is running
if(running)
{
//timer: as a string
char* time = "Timer: ";
//current time as a string
char* current = 0;
//convert timers time to a string
itoa((SDL_GetTicks() - start), current, 10);
//adds time (Timer: ) + time in ms
strcat(time, current);
//renders the time surface
seconds = TTF_RenderText_Solid(font, time, textColor);
//apply the times surface
apply_surface((SCREEN_WIDTH - seconds->w)/2,50,seconds,screen);
SDL_FreeSurface(seconds);
}[/source]

Besides your C string issues, do you also realize your rendering code will only run while this is true: ?

while(SDL_PollEvent(&event))

since all the rendering is done within that loop (meaning, it only renders when it gets an event, typically an input event).

You are right guys, it was silly mistake, now it works, thanks for your assistance