[Mesa-dev] How does FakeGLX work since Mesa 10?

[Tom Hudson]

I'm trying to upgrade a Mesa 10 installation to Mesa 17. There have been
plenty of changes, but only one breakage that's left me perplexed.

https://cgit.freedesktop.org/mesa/mesa/commit/?id=c00b250c8061d042d9905e61b9077462ee91008b

In this CL, Mesa stopped maintaining a __GLXcontext for FakeGLX; there's
just an XMesaContext.

Fake_glXGetCurrentContext() casts the XMesaContext to a __GLXContext and
returns it. Perhaps the reasonable assumption is that a context is an
opaque object.

However, glXGetCurrentDisplay() doesn't respect that assumption; it assumes
it is getting a valid __GLXContext and returns __GLXContext::currentDpy,
the first pointer.

The first pointer in an XMesaContext is *not* a pointer to a Display, and
so any code that relies on this code path seems doomed to disappointment.

This is hitting us in open-source projects based on Ogre, but seems like a
breakage in the public API that other users would have run into in the 3
years since that commit?

Is this really a bug (which presumably I should file), or am I missing
something?
Does anyone have suggestions for working around it?

Tom
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