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OpenGL and SDL integration
Alex Barry
Guest

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I'm attempting to integrate OpenGL into SDL by including <GL\gl.h> instead
of doing all this weird dynamic stuff (because I have no idea how to do it)

Anyway, whenever I startup the videa with the SDL_OPENGL flag, the video
doesn't work and it aborts (without going through my error checking)

Any thoughts?

Alex~

Here's some code, too:
class ScreenData
{
public:

void set( int xres, int yres, int bbp, Uint32 flags ); /* Set video
(will clear previous page if set) */
void setgl( int xmin, int ymin, int xmax, int ymax ); /* set opengl
window */

SDL_Surface *page; /* Screen
Surface */
};

void ScreenData::set( int xres, int yres, int bbp, Uint32 flags )
/*
sets the video mode appropriately
*/
{
if( page )
{
SDL_FreeSurface( page ); /* If there is an
existant page, clear it */
}
page = SDL_SetVideoMode (xres, yres, bbp, flags ); /* Reset the page
to the current */
if( page == NULL )
{
char* msg;
sprintf( msg, "Couldn't set %dx%dx%d video mode: %s\n", xres, yres,
bbp, SDL_GetError ( ) );
MessageBox( 0, msg, "Error", MB_ICONHAND );
free( msg );
exit( 2 );
}
}
void ScreenData::setgl( int xmin, int ymin, int xmax, int ymax )
/*
Setup OpenGL video
*/
{
glViewport(xmin, ymin, xmax, ymax);
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glClearDepth(1.0);
glDepthFunc(GL_LESS);
glEnable(GL_DEPTH_TEST);
glShadeModel(GL_SMOOTH);
glMatrixMode(GL_PROJECTION);
glMatrixMode(GL_MODELVIEW);

}
/* #################################### */

int main (int argc, char *argv[])
{
char *msg;
int done;

/* Initialize SDL */
if (SDL_Init (SDL_INIT_VIDEO) < 0)
{
sprintf (msg, "Couldn't initialize SDL: %s", SDL_GetError ());
progshutdown( screen.page, true, "SDL Initialization Error", msg, 27
);
}
atexit (SDL_Quit);

if(TTF_Init()==-1) {
sprintf (msg, "Couldn't initialize SDL_ttf: %s\nError Code: 0x02",
TTF_GetError() );
MessageBox (0, msg, "Error", MB_ICONHAND);
free (msg);
exit(2);
}
atexit( TTF_Quit );

screen.set( 800, 600, 16, SDL_OPENGL | SDL_HWSURFACE | SDL_NOFRAME );
screen.setgl( 0, 0, 800, 600 ); // this sets up the opengl window view
port and such...

SDL_WM_SetCaption ("Atosoft++ (c) 2006", NULL);
// there's more, but it's irrelevant
}

--
Smith: "...Why, Mr Anderson, Why - Do - You - Persist?"
Neo: "Because I choose to."
-Matrix Revolutions
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OpenGL and SDL integration
Koshmaar
Guest

Reply with quote
Alex Barry written:

Quote:
I'm attempting to integrate OpenGL into SDL by including <GL\gl.h>
instead of doing all this weird dynamic stuff (because I have no idea
how to do it)

Anyway, whenever I startup the videa with the SDL_OPENGL flag, the video
doesn't work and it aborts (without going through my error checking)

Any thoughts?

Alex~

if( page )
{
SDL_FreeSurface( page ); /* If there is an existant page, clear it */
}

In your code I didn't see anywhere any assignment in form of "page = 0",
which typically occurs in constructors. So, when you're first calling
ScreenData::set(), page will have random value, which may explain why
program is aborting, but it doesn't explain why it aborts only when you
pass SDL_OPENGL flag.


Anyway, this line of code doesn't make any sense, since surface
allocated by SDL_SetVideoMode is managed by SDL automatically and
calling SDL_FreeSurface on it is illegal. Consult SDL_Wiki for details :-)

Koshmaar
OpenGL and SDL integration
Ryan C. Gordon
Guest

Reply with quote
Quote:
SDL_FreeSurface( page ); /* If there is

Don't call FreeSurface on the return value from SDL_SetVideoMode().

Quote:
if( page == NULL )
{
char* msg;
sprintf( msg, "Couldn't set %dx%dx%d video mode: %s\n", xres,
yres, bbp, SDL_GetError ( ) );
MessageBox( 0, msg, "Error", MB_ICONHAND );
free( msg );
exit( 2 );
}

Your sprintf() is writing to an uninitialized pointer, and freeing it, too.

--ryan.
OpenGL and SDL integration
Damien A
Guest

Reply with quote
OK, here goes:
Both statements in your Initialise SDL block are not written correctly.
1) The character pointer msg is not initialised before it is used.
I'll assume that you forgot to put that in the snippet Razz. Just make
sure that the size of the buffer that it points to is large enough to
hold the final error message.
2) Although I don't know what progshutdown does, it seems as though it
writes a message to the 'SDL_Surface *page'. This pointer (assuming you
declared 'screen' as 'ScreenData screen', and forgot to put it in the
code snippet), can't hold a valid SDL Surface if SDL's Video subsystem
is _not_ initialised, so you should redirect your error to a file, or
message box.

Besides those, here are somethings you might want to consider:
As you are using the SDL_OPENGL flag, SDL_HWSURFACE is unnecessary. Also
if you are using OpenGL for rendering, you won't need to save the
surface returned by SDL_SetVideoMode. Just set up your projection and
model view matrices to suit your application. You simply select a
matrix, and then move on to another, but don't set them to anything
meaningful.

Reread whatever tutorials you are using, and take a look at the opengl
redbook (you can google for that) for more information on using opengl.

Here is a useful opengl FAQ:
http://www.gamedev.net/community/forums/showfaq.asp?forum_id=25

Alex Barry wrote:
Quote:
I'm attempting to integrate OpenGL into SDL by including <GL\gl.h>
instead of doing all this weird dynamic stuff (because I have no idea
how to do it)

Anyway, whenever I startup the videa with the SDL_OPENGL flag, the
video doesn't work and it aborts (without going through my error
checking)

Any thoughts?

Alex~

Here's some code, too:
class ScreenData
{
public:

void set( int xres, int yres, int bbp, Uint32 flags ); /* Set
video (will clear previous page if set) */
void setgl( int xmin, int ymin, int xmax, int ymax ); /* set
opengl window */

SDL_Surface *page; /*
Screen Surface */
};

void ScreenData::set( int xres, int yres, int bbp, Uint32 flags )
/*
sets the video mode appropriately
*/
{
if( page )
{
SDL_FreeSurface( page ); /* If there
is an existant page, clear it */
}
page = SDL_SetVideoMode (xres, yres, bbp, flags ); /* Reset the
page to the current */
if( page == NULL )
{
char* msg;
sprintf( msg, "Couldn't set %dx%dx%d video mode: %s\n", xres,
yres, bbp, SDL_GetError ( ) );
MessageBox( 0, msg, "Error", MB_ICONHAND );
free( msg );
exit( 2 );
}
}
void ScreenData::setgl( int xmin, int ymin, int xmax, int ymax )
/*
Setup OpenGL video
*/
{
glViewport(xmin, ymin, xmax, ymax);
glClearColor( 0.0f, 0.0f, 0.0f, 0.0f);
glClearDepth(1.0);
glDepthFunc(GL_LESS);
glEnable(GL_DEPTH_TEST);
glShadeModel(GL_SMOOTH);
glMatrixMode(GL_PROJECTION);
glMatrixMode(GL_MODELVIEW);

}
/* #################################### */

int main (int argc, char *argv[])
{
char *msg;
int done;

/* Initialize SDL */
if (SDL_Init (SDL_INIT_VIDEO) < 0)
{
sprintf (msg, "Couldn't initialize SDL: %s", SDL_GetError ());
progshutdown( screen.page, true, "SDL Initialization Error",
msg, 27 );
}
atexit (SDL_Quit);

if(TTF_Init()==-1) {
sprintf (msg, "Couldn't initialize SDL_ttf: %s\nError Code:
0x02", TTF_GetError() );
MessageBox (0, msg, "Error", MB_ICONHAND);
free (msg);
exit(2);
}
atexit( TTF_Quit );

screen.set( 800, 600, 16, SDL_OPENGL | SDL_HWSURFACE | SDL_NOFRAME );
screen.setgl( 0, 0, 800, 600 ); // this sets up the opengl window
view port and such...

SDL_WM_SetCaption ("Atosoft++ (c) 2006", NULL);
// there's more, but it's irrelevant
}

--
Smith: "...Why, Mr Anderson, Why - Do - You - Persist?"
Neo: "Because I choose to."
-Matrix Revolutions
------------------------------------------------------------------------

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