Re: [PyOpenGL-Users] using glGetSynciv

[Mike C. F. <mcf...@vr...>]

On 11-05-23 05:44 PM, Henry Gomersall wrote:
...
> That didn't seem to be the problem.
>
> I've had a bit more of a play. Its seems that the problem is *actually*
> the first argument: my_sync is an integer. I can't find the type that it
> actually needs as the argument though. I've not idea what GLsync
> actually is.
>
> Cheers,
>
> Henry
Okay, I constructed my own test case so I could see what the problem
is.  There was a bug in the declaration of GLsync, which was declared to
be a c_void_p, it should have been declared as a ctypes.POINTER(
structure ).  I had thought c_void_p would create an opaque pointer type
as a return-type, but apparently ctypes short-circuits it to return an
integer.

I've checked a fix into bzr, and that should appear in the next release
of PyOpenGL.  In the meantime, you can patch your copy of PyOpenGL with
this:

=== modified file 'OpenGL/constants.py'
--- OpenGL/constants.py 2011-04-12 19:23:44 +0000
+++ OpenGL/constants.py 2011-05-24 02:47:52 +0000
@@ -103,7 +103,9 @@
 # GL.ARB.sync extension, GLsync is an opaque pointer to a struct
 # in the extensions header, basically just a "token" that can be
 # passed to the various operations...
-GLsync = ctypes.c_void_p
+class _GLsync( ctypes.Structure ):
+    """Opaque structure definition to fool ctypes into treating us as a
real structure"""
+GLsync = ctypes.POINTER( _GLsync ) # ctypes.c_void_p does *not* work as
a return type...
 GLvoidp = ctypes.c_void_p
 
 ARRAY_TYPE_TO_CONSTANT = [

HTH,
Mike

-- 
________________________________________________
  Mike C. Fletcher
  Designer, VR Plumber, Coder
  http://www.vrplumber.com
  http://blog.vrplumber.com