Re: Runtime error when using blending (on windows XP)

Yann Morvan wrote:

> Well, it looks like I've been too quick to speak.
> I was stuck with an old opengl dll (the one that came with windows,
> somehow I expected it to be reasonably up to date), so
> most wglGetProcAddress calls are indeed returning NULL.
> Replacing it with a recent mesa one made my C test program return non NULL
> addresses.
> I don't really understand how libHopenGL is built from the relevent dlls,
> but it looks like I will have to recompile the package, since my program
> still crashes.

OpenGL libraries which support hardware acceleration (including the
one supplied with Windows) simply act as a front end to a separate
driver which is specific to your graphics hardware. A particular
driver may or may not support a specific OpenGL extension; if the
driver doesn't support it, then wglGetProcAddress() will return NULL.

If the driver doesn't implement a particular function, it may be
because the hardware isn't capable of providing the corresponding
functionality. In that situation, the only solution would be to get a
more featureful graphics card.

OTOH, if you use Mesa, the functionality available doesn't depend upon
the hardware, as Mesa does all of the rendering in software. If one
version of Mesa doesn't provide a particular extension, a later
version might.

-- 
Glynn Clements <[email protected]>