Ubuntu Games Developer Resource Wiki

[Mickeysofine1972]

Hi

You may have noticed a large amount of HOWTO relating to SDL and games programming on this part of the forum, well, guess what! we've made a Wiki to store all these lovely articles.

We will continue to post on the forum about any questions and we will announce every new HOWTO as they are released.

If you have any ideas for HOWTOs or you have a HOWTO of your own that you would like to contribute, let us know and we will be happy to include anything you give.

The URL for our new Wiki is: http://ubuntu-gamedev.pbwiki.com/

Mike

[Choad]

following your first tutorial, libsdl OSS wants to get rid of libsdl ALSA

is there a reason why i want OSS over ALSA

will removing ALSA break things?

[Choad]

ok the second tutorial, in the wiki it says SDL_Flip(); but it needs to be SDL_Flip(screen);

also, i made this

#include "SDL/SDL.h"

int main(int argc, char* argv[])
{
	// start sdl
	SDL_Init(SDL_INIT_EVERYTHING);
	
	// load an image
	
	SDL_Surface* loaded_image = NULL;
	loaded_image = SDL_LoadBMP("MyImage.bmp");
	
	// convert it to the right format
	
	SDL_Surface* compatible_image = NULL;
	compatible_image = SDL_DisplayFormat(loaded_image);
	SDL_FreeSurface(loaded_image);
	
	// set up the screen
	
	const int SCREEN_WIDTH = 800;
	const int SCREEN_HEIGHT = 600;
	const int SCREEN_BPP = 32;
	
	SDL_Surface* screen = NULL;
	
	screen = SDL_SetVideoMode(	SCREEN_WIDTH, 
					SCREEN_HEIGHT, 
					SCREEN_BPP, 
					SDL_SWSURFACE);
	
	// put image on screen
	
	SDL_Rect position;
	position.x = 0;
	position.y = 0;
	
	SDL_BlitSurface(	compatible_image,
				NULL,
				screen,
				&position);
	
	SDL_Flip(screen);
	
	//Wait 2 seconds
	SDL_Delay( 2000 );
	

	// Destroy remaining surfaces
	SDL_FreeSurface( compatible_image );
	
	
	// quit sdl
	SDL_Quit();
	
	return 0;
}

and it compiles but it just displays a black window. my image is NOT displayed. why is this? the image is in the same directory as the binary

[Mickeysofine1972]

following your first tutorial, libsdl OSS wants to get rid of libsdl ALSA

is there a reason why i want OSS over ALSA

will removing ALSA break things?

No reason i can think of, you might have problems i fthe system you want to run the program on need OSS instead of ALSA. I'm not too sure theres much likelihood of that though unless someone else knows of something that might make a difference.

Go with OSS I would say, but only because I read somewhere that its a better sound system.

Mike

[Mickeysofine1972]

ok the second tutorial, in the wiki it says SDL_Flip(); but it needs to be SDL_Flip(screen);

also, i made this

#include "SDL/SDL.h"

int main(int argc, char* argv[])
{
	// start sdl
	SDL_Init(SDL_INIT_EVERYTHING);
	
	// load an image
	
	SDL_Surface* loaded_image = NULL;
	loaded_image = SDL_LoadBMP("MyImage.bmp");
	
	// convert it to the right format
	
	SDL_Surface* compatible_image = NULL;
	compatible_image = SDL_DisplayFormat(loaded_image);
	SDL_FreeSurface(loaded_image);
	
	// set up the screen
	
	const int SCREEN_WIDTH = 800;
	const int SCREEN_HEIGHT = 600;
	const int SCREEN_BPP = 32;
	
	SDL_Surface* screen = NULL;
	
	screen = SDL_SetVideoMode(	SCREEN_WIDTH, 
					SCREEN_HEIGHT, 
					SCREEN_BPP, 
					SDL_SWSURFACE);
	
	// put image on screen
	
	SDL_Rect position;
	position.x = 0;
	position.y = 0;
	
	SDL_BlitSurface(	compatible_image,
				NULL,
				screen,
				&position);
	
	SDL_Flip(screen);
	
	//Wait 2 seconds
	SDL_Delay( 2000 );
	

	// Destroy remaining surfaces
	SDL_FreeSurface( compatible_image );
	
	
	// quit sdl
	SDL_Quit();
	
	return 0;
}

and it compiles but it just displays a black window. my image is NOT displayed. why is this? the image is in the same directory as the binary

Do you have a bmp file in the same folder called 'MyImage.bmp'?

If you don't then you could make one with GIMP or some other image software and place it in that folder. It is a windows bmp btw.

Mike

[Choad]

yes i do.

[seethru]

yes i do.

Put some error checking in and have it output the error message you're getting to the terminal. It'll give you some insight into where you're going wrong. Plus, it's just good code to put in redundant checks.

[Mickeysofine1972]

The only thing that I can see that strikes me as different from our example is that you convert the image BEFORE you set the video surface.

Try doing it after you set the screen up and see what happens.

Mike

[Choad]

Put some error checking in and have it output the error message you're getting to the terminal. It'll give you some insight into where you're going wrong. Plus, it's just good code to put in redundant checks.

yeah i would have, but i was following the tutorial

dont you think the tutorial should be updated?

i dont actually know how to put error checking in. is it just checking the return value of each function for a positive or negative number?

[Choad]

The only thing that I can see that strikes me as different from our example is that you convert the image BEFORE you set the video surface.

Try doing it after you set the screen up and see what happens.

Mike

that did it