[Mesa-dev] [Bug 92552] [softpipe] piglit egl-create-context-valid-flag-forward-compatible-gl regression

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Tue Oct 20 09:51:30 PDT 2015


--- Comment #5 from Matthew Waters <ystreet00 at gmail.com> ---
(In reply to Boyan Ding from comment #4)
> The spec of EGL_KHR_create_context says:
>     requesting a forward-compatible context for OpenGL versions less
>     than 3.0 will generate an error
> The code now takes "OpenGL version" above as version requested with EGL (1.0
> by default). However, the OpenGL version actually provided can be up to 3.0.
> In such case, your patch will fail to create forward-compatible context,
> giving the "appropriate" error, while mesa before 86ccb2a1 will succeed.
> Though both behaviors pass piglit.
> Any ideas?

IIRC, when I made that original patch over a year ago, I stole that logic from
the GLX code which does exactly the same thing.

Essentially the problem is whether "OpenGL version" is the requested version in
the EGLConfig or the effective version.  I would argue that it's ultimately
impossible to know the effective version without creating a context so the
"OpenGL version" therefore refers to the requested version in the EGLConfig.

I also wonder about the relevance.  Forward compatible contexts only appeared
in GL >= 3.0 versions so if an application knows about forward-compatible, it
knows that it's GL >= 3.0 only and must at least request a GL >= 3.0 to be able
to use the flag.  Requesting a GL < 3.0 context with forward compatible is a
dangerous game to be playing.

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