SDL whats wrong with display format?

[mozly]

Im following lazy foo's SDL tutorial to set the color key on an image.
I did many of his tutorials and now I have a problem that didn't exist before.

I load img1 but the line SDL_DisplayFormat(img1) DOES NOTHING ( found this out during debug) and so the program exits.What am I doing wrong?

Here is the snipper

SDL_Surface* loadimg(std::string filename)
{
	SDL_Surface* img1 = NULL;
	SDL_Surface* img2 =NULL;
	img1 = IMG_Load(filename.c_str());

	if(img1 !=NULL)
	{
		img2 = SDL_DisplayFormat(img1);
		SDL_FreeSurface(img1); 
		if(img2 != NULL)
		SDL_SetColorKey(img2,SDL_SRCCOLORKEY,SDL_MapRGB(img2->format,0xFF,0xFF,0xFF));
	}
	return img2;
}

Thanks in advance.

[Return 0]

mozly wrote:

I load img1 but the line SDL_DisplayFormat(img1) DOES NOTHING ( found this out during debug) and so the program exits.What am I doing wrong?

Not sure what you are doing with the return value, but look at the following:

	if(img1 !=NULL)
	{
		img2 = SDL_DisplayFormat(img1);
		SDL_FreeSurface(img1); 
		if(img2 != NULL)
		SDL_SetColorKey(img2,SDL_SRCCOLORKEY,SDL_MapRGB(img2->format,0xFF,0xFF,0xFF));
	}
	return img1;

You are successfully copying img1 to img2, of course assuming img1 loaded successfully in the first place, but then you are freeing img1 here: SDL_FreeSurface(img1); which is fine. But you are returning img1 which you just destroyed. You should be returning the optimized image, img2. Make sense?

[mozly]

Actually i did return img2; return img1 is a typo. it is display format that doesent work.

[Return 0]

Ok so you need to confirm if img1 was loaded successfully then. Run some tests. img1 must be NULL.

[mozly]

img1 is not NULL, I checked during runtime debug.

[Return 0]

Alright, and have you confirmed that img2 is not NULL after img2 = SDL_DisplayFormat(img1);? Just trying to determine if that's really the problem because I don't see anything wrong with your code. If it's not null then there is a problem with your blitting function.

[mozly]

There is most definately a problem with the SDL_DisplayFormat()

here is the complete code if it helps
scroll to the bottom to see the function i'm having problems with

#include <SDL.h>
#include <SDL_image.h>
#include <string>
SDL_Surface* loadimg(std::string filename);

SDL_Surface* screen=NULL;
SDL_Surface* background = NULL;

SDL_Event event;



class Window
{
private:
	bool windowed;
	bool windowOK;
public:
	Window();
	void handle_event();
	void toggle_fullscreen();
	bool error();
};






void applysurface(int x, int y, SDL_Surface* src, SDL_Surface* dst, SDL_Rect* clop = NULL)
{
	SDL_Rect offset;
	offset.x=x;
	offset.y=y;

	SDL_BlitSurface(src,clop,dst,&offset);
}

bool init()
{
	if(SDL_Init(SDL_INIT_EVERYTHING) ==-1)
	return false;

	background = loadimg("window.png");

	if(screen ==NULL || background ==NULL )
		return false;

	return true;
}

void bye()
{
	SDL_FreeSurface(background);
	SDL_Quit();
}


class Timer
{
public:
	Timer()
	{
		startTicks = 0;
		pausedTicks = 0;
		paused = false;
		started = false;
	}
	void start()
	{
		started = true;
		paused = false;
		startTicks = SDL_GetTicks();
	}
	void stop(){
	started = false;
	paused = false;
	}

	void pause(){
		if(started && !paused)
		{
			paused = true;
			pausedTicks = SDL_GetTicks() - startTicks;
		}
	}
	void unpause()
	{
		if(paused)
		{
			paused = false;
			startTicks = SDL_GetTicks() - pausedTicks;
			pausedTicks = 0;
		}
	}
	int get_ticks(){
		if(started)
		{
			if(paused)
				return pausedTicks;
			else
				return SDL_GetTicks() - startTicks;
		}
		return 0;
	}
	bool is_started(){
	return started;
	}
	bool is_paused()
	{
		return paused;
	}

protected:
	int startTicks;
	int pausedTicks;
	bool paused;
	bool started;
};

Window::Window()
{
	screen = SDL_SetVideoMode(640,480,32, SDL_SWSURFACE | SDL_RESIZABLE);

	if(screen == NULL)
	{
		windowOK = false;
		return;
	}
	else
	{
		windowOK = true;
	}

	SDL_WM_SetCaption("window event test", NULL);

	windowed = true;
}

void Window::toggle_fullscreen()
{
	if(windowed == true)
	{
		screen = SDL_SetVideoMode(640,480,32,SDL_SWSURFACE | SDL_RESIZABLE | SDL_FULLSCREEN);

		if(screen == NULL)
		{
			windowOK = false;
			return;
		}

		windowed = false;
	}

	else if(windowed == false)
	{
		screen = SDL_SetVideoMode(640,480,32,SDL_SWSURFACE | SDL_RESIZABLE);

		if(screen == NULL)
		{
			windowOK = false;
			return;
		}
		
		windowed = true;
	}
}

void Window::handle_event()
{
	if(windowOK == false)
	{
		return;
	}

	if(event.type == SDL_VIDEORESIZE)
	{
		screen = SDL_SetVideoMode(event.resize.w, event.resize.h, 32, SDL_SWSURFACE | SDL_RESIZABLE);

		if(screen == NULL)
		{
			windowOK = false;
			return;
		}
	}

	else if( (event.type == SDL_KEYDOWN) && (event.key.keysym.sym == SDLK_RETURN))
	{
		toggle_fullscreen();
	}

	else if(event.type == SDL_ACTIVEEVENT)
	{
		if(event.active.state & SDL_APPACTIVE)
		{
			if(event.active.gain == 0)
			{
				SDL_WM_SetCaption("Windwo Event Test:iconified",NULL);

			}
			else
			{
				SDL_WM_SetCaption("Window Event Test",NULL);
			}
		}
		else if(event.active.state & SDL_APPINPUTFOCUS)
		{
			if(event.active.gain == 0)
			{
				SDL_WM_SetCaption("Window Event Test: Keyboard focus lost",NULL);

			}
			else
			{
				SDL_WM_SetCaption("Window Event Test", NULL);
			}

		}

		else if(event.active.state & SDL_APPMOUSEFOCUS)
		{
			if(event.active.gain ==0 )
			{
				SDL_WM_SetCaption("Window event Test: Mouse Focus Lost", NULL);
			}
			else
			{
				SDL_WM_SetCaption("Window Event test", NULL);
			}
		}
	}
	else if(event.type == SDL_VIDEOEXPOSE)
	{
		if (SDL_Flip(screen) == -1)
		{
			windowOK = false;
			return;
		}
	}

}

bool Window::error()
{
	return !windowOK;
}

int main( int argc, char* args[] )
{
	bool quit = false;

	if(!init())
		return 1;

	Window myWindow;

	if(myWindow.error() == true)
	{
		return 1;
	}

	while(!quit)
	{
		while(SDL_PollEvent(&event))
		{
			myWindow.handle_event();
			if((event.type == SDL_KEYDOWN) && (event.key.keysym.sym == SDLK_ESCAPE))
			{
				quit = true;
			}

			if(event.type == SDL_QUIT)
				quit = true;

		}

		if(myWindow.error())
			return 1;

		SDL_FillRect(screen, &screen->clip_rect, SDL_MapRGB(screen->format, 0xFF,0xFF,0xFF));
		applysurface((screen->w - background->w)/2, (screen->h - background->h)/2, background, screen);

		if(SDL_Flip(screen) == -1)
			return 1;
	}



	return 0;
}


SDL_Surface* loadimg(std::string filename)
{
  SDL_Surface* img1 = IMG_Load(filename.c_str());

  if(img1 ==NULL)
  {
    return NULL;
  }

  SDL_Surface* img2 = SDL_DisplayFormat(img1);
  SDL_FreeSurface(img1); 
  if(img2 == NULL)
  {
    return NULL;
  }

  SDL_SetColorKey(img2,SDL_SRCCOLORKEY,SDL_MapRGB(img2->format,0xFF,0xFF,0xFF));

  return img2;
}

[Return 0]

Good Lord, this was a nightmare to debug... I believe i've found your problem. You need to set the Video mode first before attempting to load or copy images. You currently don't do this until after you try loading/copying the surfaces. Your setting it during your Window object's contstructor call. The below code needs to be used before calling your imgload function.

screen = SDL_SetVideoMode(640,480,32, SDL_SWSURFACE | SDL_RESIZABLE);

Because SDL_DisplayFormat copies pixel info, etc... if you haven't set the video mode before you try loading the images, I believe it's all going to be NULL data because it doesn't know dimensions, etc... Give that a shot and let me know if it works.