[Mesa-dev] [Bug 71870] Metro: Last Light rendering issues

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=71870

--- Comment #38 from José Suárez <j.suarez.agapito at gmail.com> ---
I just wanted to give my my 2 cents on this topic. Be warned that I am no
programmer nor do i have any knowledge of graphics drivers (so please, forgive
me for any inaccuracy or incorrect technical point of view). I also know that
the mesa policy is not to fix third programs bugs within mesa's code. I think
that is the right choice, but maybe a compromise could be reached, especially
in the light that both proprietary drivers seem to be more fault tolerant with
this problem.

If the "__" macro names are reserved for _future_ use, I asume the reservation
of certain "__" macro names should be explicitly made in a particular GLSL spec
version (or subsequent versions if more need to be added). I don't know if that
has happened yet, but I presume that once that happens there should be a list
(as well as a spec) of those macro names. I also suppose that if no especific
"__" macro names have been established yet, game programmers may not be too
aware of this limitation even though the reservation has been established since
long time ago, as Ian pointed out.

Therefore, if a compromise is to be reached I think there could be two
alternatives for adressing this problem:

(i) Only enforce the "__" macro reservation beginning from the first GLSL
version that establishes any of those macro names. I.e, if program uses GLSL
version equal or greater than X.Y (being X.Y the first GLSL version with a
reservation for a particular "__" macro), then disallow the use of those custom
macros. Otherwise, allow the use. Mesa could output a warning instead of
failing.

(ii) Once the GLSL specs begin expressly reserving certain "__" macro names,
only disallow the use of them as custom macro names.

I believe the second approach is less desirable.

Of course not doing anything is also a possibility, but I believe trying to get
a third party programmer to change a game's code is quite difficult. There are
very collaborative game devs (such as, for instance, The Farm 51, who offered
steam keys to mesa devs to sort out some bugs), but I'm sure there will be
others who are not so friendly. And if this use of "__" macro names comes from
using some develoment apps or techniques, I supose they would not be willing to
risk messing the code just for satisfying a very small fraction of users who
are gaming on Linux with mesa -dont't get me wrong, I wish we were a majority
of the gamers- or (if not construed by the game developer that altruisticly)
achieving 100% spec compatible code.

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