[vtkusers] Crash with subsequent creation of vtkRenderWindow in Python

[Pearu Peterson]

On Sat, 5 Apr 2003, Charl P. Botha wrote:

> On Sat, Apr 05, 2003 at 07:29:18PM +0300, Pearu Peterson wrote:
> > #6   0x424fa5d3 in glXDestroyContext(dpy=0x8514be8,ctx=0x8518af8) in 'glxapi.c', line 208
> > #5   0x424fecd6 in Fake_glXDestroyContext(dpy=0x8514be8,ctx=0x8518af8) in 'fakeglx.c ', line 1462
> > #4   0x42505f34 in XMesaGarbageCollect() in 'xm_api.c', line 2530
> > #3   0x425d68b7 in XSync()
> > #2   0x425daba6 in _XReply()
> > #1   0x425d980c in ?()
> > #0   0x425f4cae in _X11TransWrite()
> 
> Hmmm, this is a perfectly normal glxDestroyContext call in
> vtkXOpenGLRenderWindow.  Maybe you could check what happens in that
> unfortunately named Fake_glXDestroyContext() call in Mesa?

Well, this is the code from fakeglx.c:

"""
/*
 * Our fake GLX context will contain a "real" GLX context and an XMesa
   context.
 *
 * Note that a pointer to a __GLXcontext is a pointer to a
   fake_glx_context,
 * and vice versa.
 *
 * We really just need this structure in order to make the libGL functions
 * glXGetCurrentContext(), glXGetCurrentDrawable() and 
   glXGetCurrentDisplay()
 * work correctly.
 */
struct fake_glx_context {
   __GLXcontext glxContext;   /* this MUST be first! */
   XMesaContext xmesaContext;
};


static void
Fake_glXDestroyContext( Display *dpy, GLXContext ctx )
{
   struct fake_glx_context *glxCtx = (struct fake_glx_context *) ctx;
   (void) dpy;
   MakeCurrent_PrevContext = 0;
   MakeCurrent_PrevDrawable = 0;
   MakeCurrent_PrevReadable = 0;
   MakeCurrent_PrevDrawBuffer = 0;
   MakeCurrent_PrevReadBuffer = 0;
   XMesaDestroyContext( glxCtx->xmesaContext );
   XMesaGarbageCollect();
}

"""

where from xm_api.c

"""
void XMesaDestroyContext( XMesaContext c )
{
#ifdef FX
   if (c->xm_draw_buffer && c->xm_buffer->FXctx)
      fxMesaDestroyContext(c->xm_draw_buffer->FXctx);
#endif
   if (c->gl_ctx) {
      _swsetup_DestroyContext( c->gl_ctx );
      _swrast_DestroyContext( c->gl_ctx );
      _tnl_DestroyContext( c->gl_ctx );
      _ac_DestroyContext( c->gl_ctx );
      _mesa_destroy_context( c->gl_ctx );
   }

   FREE( c );
}

/*
 * Look for XMesaBuffers whose X window has been destroyed.
 * Deallocate any such XMesaBuffers.
 */
void XMesaGarbageCollect( void )
{
   XMesaBuffer b, next;
   for (b=XMesaBufferList; b; b=next) {
      next = b->Next;
      if (b->display && b->frontbuffer && b->type == WINDOW) {
#ifdef XFree86Server
         /* NOT_NEEDED */
#else
         XSync(b->display, False);

         if (!window_exists( b->display, b->frontbuffer )) {
            /* found a dead window, free the ancillary info */
            XMesaDestroyBuffer( b );
         }
#endif
      }
   }
}
"""

I'll try to play with the above code (e.g. I am not sure why
XFree86Server was not defined in my case). But if you have
any hints what to try, they are most welcome.

> It's very difficult for me to help debugging this as I can't reproduce it.

Sure, it's understandable.

Thanks,
	Pearu