[Wayland-bugs] [Bug 97773] New Mesa master now results in warnings in glrender (and subsurfaces and simple-egl), black screen

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=97773

Pekka Paalanen <ppaalanen at gmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |emil.l.velikov at gmail.com

--- Comment #1 from Pekka Paalanen <ppaalanen at gmail.com> ---
Yes, it does. You have to stick to an older Mesa until we fix it in Weston by
starting to use libepoxy I believe. But I also heard someone say libepoxy does
not build without X11 yet (I have not confirmed), so that would need fixing
too.

The reason is, that Khronos decided to stop declaring any OpenGL ES 2 core
functions unless GL_GLEXT_PROTOTYPES is defined. IMO that is wrong on multiple
levels: "GLEXT" refers to extension functions, not core functions; it breaks
existing applications just like in this bug report.

Traditionally using GL_GLEXT_PROTOTYPES means "I do not care about the
portability of my program between different GL implementations." Therefore we
should not simply use it and it will expose far too much.

My own speculation is, based on what GL_GLEXT_PROTOTYPES used to mean, is that
libGLESv2.so will at some point actually stop exporting any GL ES 2.0 core
functions. This will break all existing application binaries.

It is probably all part of an attempt to fix the issue that different (GL ES)
implementations export different sets of functions. Khronos' decision is one
that makes everyone equally unhappy, so at least it's not favouring anyone.

In the end, we need to start getting also the GL ES core functions via
eglGetProcAddress(). This is probably easiest to do by relying on libepoxy
(Xwayland/glamor already requires it, and I hear recent GTK+ 3.x too). It will
only work when EGL_KHR_get_all_proc_addresses extension is supported, so one
needs a fallback to dlsym(). It's not too complicated, but very unfruitful to
write and maintain ourselves, hence libepoxy.

If you are too bored, there is a related discussion that gives some background
here:
https://lists.freedesktop.org/archives/mesa-dev/2016-June/120763.html
Obviously Khronos went its own way, already in March 2015 I hear.

I also hear there are bug reports open at Khronos, so let's see if things
change again.

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