[Chromium-dev] How to safely access an extension in a super spu?

[Mike H. <mho...@gr...>]

I need more advanced blending modes for composite spus, so I want to use 
blending extensions if available.  How do I safely do this?  It's easy 
to get and check the extension within my spu, but I then need to call 
that function on my parent/super, 'render'.  If I do this the "safe" way 
within my spu, I issue a crGetProcAddress and set a local function 
pointer.  Obviously this does not work for the parent/super spu.

A quick explanation of why I need this.  After a brief chat with Kurt 
Akeley about my blending issues doing a parallel composite, he told me 
about how the base blending modes are mostly broken and were a carry 
over from a rash implementation of them in IrisGL.  If you use 
src_alpha, 1-src_alpha in glBlendFunc, the alpha values of the src and 
dst are also multiplied.  Then, when you issue a readback, the values in 
the alpha channel that you will use for the next composite are broken.  
What I really want to do is a normal alpha blend and have only the color 
components, but not the alpha values, effected.  The correct solution 
seems to be glBlendFunSeparateEXT.

Ideas on how to safely use this extension within a spu?  Under linux I 
don't need to load the extension as it is exported already, but Windows, 
of course, does not export the function so a GetProcAddress of some sort 
is required.

Thanks,

-Mike