[Mesa-dev] is it possible to dynamic load OSMesa?

[Patrick Baggett]

If libOSMesa.so is separate library, then isn't libGL.so too? You're calling
glGetIntegerv() from libGL.so but not from libOSMesa.so -- try doing
dlsym("glGetIntegerv") and removing libGL.so from the link line.

Patrick

On Fri, Jul 15, 2011 at 2:41 PM, Paul Gotzel <paul.gotzel at gmail.com> wrote:

> Hello,
>
> I've downloaded the latest 7.10.3 and I need to be able to dynamically load
> OSMesa.  Is this possible?  I've tried to use dlopen and dlsym to load the
> functions and all the OSMesa calls return success but when I make the gl
> calls I get:
>
> GL User Error: glGetIntegerv called without a rendering context
> GL User Error: glGetIntegerv called without a rendering context
> GL User Error: glGetIntegerv called without a rendering context
>
> Any help would be appreciated.
>
> Thanks,
> Paul
>
> My sample program is as follows.  I compile it with the same flags as the
> rest of the demo programs without linking to OSMesa.
>
> static void *
> loadOSMesa()
> {
>   return dlopen("libOSMesa.so", RTLD_DEEPBIND | RTLD_NOW | RTLD_GLOBAL);
> }
>
> static OSMesaContext
> dynOSMesaCreateContext()
> {
>   typedef OSMesaContext (*CreateContextProto)( GLenum , GLint , GLint ,
> GLint , OSMesaContext );
>   static void *createPfunc = NULL;
>   CreateContextProto createContext;
>   if (createPfunc == NULL)
>   {
>     void *handle = loadOSMesa();
>     if (handle)
>     {
>       createPfunc = dlsym(handle, "OSMesaCreateContextExt");
>     }
>   }
>
>   if (createPfunc)
>   {
>     createContext = (CreateContextProto)(createPfunc);
>     return (*createContext)(GL_RGBA, 16, 0, 0, NULL);
>   }
>   return 0;
> }
>
> static GLboolean
> dynOSMesaMakeCurrent(OSMesaContext cid, void * win, GLenum type, GLsizei w,
> GLsizei h)
> {
>   typedef GLboolean (*MakeCurrentProto)(OSMesaContext, void *, GLenum,
> GLsizei, GLsizei);
>   static void *currentPfunc = NULL;
>   MakeCurrentProto makeCurrent;
>   if (currentPfunc == NULL)
>   {
>     void *handle = loadOSMesa();
>     if (handle)
>     {
>       currentPfunc = dlsym(handle, "OSMesaMakeCurrent");
>     }
>   }
>   if (currentPfunc)
>   {
>     makeCurrent = (MakeCurrentProto)(currentPfunc);
>     return (*makeCurrent)(cid, win, type, w, h);
>   }
>   return GL_FALSE;
> }
>
> int
> main(int argc, char *argv[])
> {
>    OSMesaContext ctx;
>    void *buffer;
>
>    ctx = dynOSMesaCreateContext();
>    if (!ctx) {
>       printf("OSMesaCreateContext failed!\n");
>       return 0;
>    }
>
>    int Width = 100;
>    int Height = 100;
>
>    /* Allocate the image buffer */
>    buffer = malloc( Width * Height * 4 * sizeof(GLubyte) );
>    if (!buffer) {
>       printf("Alloc image buffer failed!\n");
>       return 0;
>    }
>
>    /* Bind the buffer to the context and make it current */
>    if (!dynOSMesaMakeCurrent( ctx, buffer, GL_UNSIGNED_BYTE, Width, Height
> )) {
>       printf("OSMesaMakeCurrent failed!\n");
>       return 0;
>    }
>
>
>    {
>       int z, s, a;
>       glGetIntegerv(GL_DEPTH_BITS, &z);
>       glGetIntegerv(GL_STENCIL_BITS, &s);
>       glGetIntegerv(GL_ACCUM_RED_BITS, &a);
>       printf("Depth=%d Stencil=%d Accum=%d\n", z, s, a);
>    }
>
>    return 0;
> }
>
>
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>
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