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

[Chia-I Wu]

On Sat, Jul 16, 2011 at 5:19 AM, Paul Gotzel <paul.gotzel at gmail.com> wrote:
> Patrick,
>
> Good thought but it doesn't work.  I don't understand why adding -lOSMesa to
> the following makes everything work.
>
> gcc -I../../include -g -O2 -Wall -Wmissing-prototypes -std=c99 -ffast-math
> -fvisibility=hidden -fno-strict-aliasing -g  -fPIC   -D_GNU_SOURCE
> -DPTHREADS -DDEBUG -DHAVE_POSIX_MEMALIGN -DUSE_XSHM  osdemo.c -L../../lib
> -lGL -o osdemo
> There must be some other initialization I need to call to get things to work
> but I don't understand enough of the details of Mesa to know what is
> missing.  I've stepped through the mesa context initialization and I cannot
> see what is different between the two runs.  The odd thing is that
> everything seems to work but then I end up what I believe is an empty gl
> dispatch table.  This is the first time I've looked this so I'm not really
> sure what to expect.  Any ideas of where to look in the Mesa code?
I am not familiar with OSMesa, but when both GL and OSMesa live in the
same address space, there are two copies of glapi (the dispatch table
and etc.).  In your example, it may happen that dynOSMesaMakeCurrent
updates OSMesa's copy of glapi, but glGetIntegerv uses GL's copy of
glapi.  But when both libraries are linked at compile time,
dynOSMesaMakeCurrent and glGetIntegerv may happen to use the same copy
of glapi.

>
> Thanks,
> Paul
>
> On Fri, Jul 15, 2011 at 3:45 PM, Patrick Baggett <baggett.patrick at gmail.com>
> wrote:
>>
>> 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;
>>> }
>>>
>>>
>>> _______________________________________________
>>> mesa-dev mailing list
>>> mesa-dev at lists.freedesktop.org
>>> http://lists.freedesktop.org/mailman/listinfo/mesa-dev
>>>
>>
>
>
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