http://bugs.winehq.org/show_bug.cgi?id=27879
--- Comment #14 from Henri Verbeet hverbeet@gmail.com 2013-04-04 06:04:01 CDT --- (In reply to comment #13)
Maybe my patch is wrong (extra sets of eyes are appreciated), but I find it suspect that every texture format, including those not supporting FBO attachment, are claimed to support blending. ARB_internalformat_query2 spec text pretty much implies that FRAMEBUFFER_BLEND should be a stricter requirement than FRAMEBUFFER_RENDERABLE.
So (guess what) I'm blaming the drivers. I'd be happy to be proved wrong.
I can confirm GL_RGBA16 returns FULL_SUPPORT for FRAMEBUFFER_BLEND on my GF9600M with 313.26. I can also confirm that Nouveau lists the format as supporting blending only on Fermi and later at http://cgit.freedesktop.org/mesa/mesa/tree/src/gallium/drivers/nv50/nv50_for...
So yeah, I'd consider that a bug in nvidia's internalformat_query2 implementation. I think we'll still want internalformat_query2 support, but once that's in this will probably be resolved UPSTREAM.