Re: Controlling vertical sync on Mac OS X / crashes when trying to access platform-specific stuff via ctypes

On Fri, Jun 14, 2013 at 3:18 AM, Nathaniel Virgo
<[email protected]>wrote:

> Hi all
>
> I need to turn on vsync. Does anyone have a way to do this on OS X?  I
> found the following code on the web, but when I run it (after creating a
> Glut window) it always causes a segmentation fault:
>
> import sys
>
> def enable_vsync():
>     if sys.platform != 'darwin':
>         return
>     try:
>         import ctypes
>         import ctypes.util
>         ogl = ctypes.cdll.LoadLibrary(ctypes.util.find_library("OpenGL"))
>         # set v to 1 to enable vsync, 0 to disable vsync
>         v = ctypes.c_int(1)
>         ogl.CGLSetParameter(ogl.CGLGetCurrentContext(), ctypes.c_int(222),
> ctypes.pointer(v))
>     except:
>         print "Unable to set vsync mode, using driver defaults"
>
> My (very uneducated) guess is that this is because CGLGetCurrentContext
> returns an int, whereas CGLSetParameter expects a pointer to a struct as
> its first argument. I have tried many permutations of the above code, but I
> don't know enough about ctypes to be able to fix it.
>
> From looking at the PyOpenGL source, it looks like there's some stuff in
> there that's aimed at exposing this kind of platform-specific stuff, but I
> couldn't find any documentation for it. Is there a "correct" way to call
> CGLSetParameter and similar functions?
>
This seems relevant to GLUT VSync-ing:
www.opengl.org/discussion_boards/showthread.php/173017-Vsync-with-glut

Ian

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