[Mesa-dev] [PATCH 1/6] mesa: Add _mesa_format_fallback_rgba_to_rgbx()

[Dylan Baker]

Quoting Chad Versace (2017-06-06 15:11:18)
> On Tue 06 Jun 2017, Dylan Baker wrote:
> > Quoting Chad Versace (2017-06-06 13:36:55)
> > > The new function takes a mesa_format and, if the format is an alpha
> > > format with a non-alpha variant, returns the non-alpha format.
> > > Otherwise, it returns the original format.
> > > 
> > > Example:
> > >   input -> output
> > > 
> > >   // Fallback exists
> > >   MESA_FORMAT_R8G8B8X8_UNORM -> MESA_FORMAT_R8G8B8A8_UNORM
> > >   MESA_FORMAT_RGBX_UNORM16 -> MESA_FORMAT_RGBA_UNORM16
> > > 
> > >   // No fallback
> > >   MESA_FORMAT_R8G8B8A8_UNORM -> MESA_FORMAT_R8G8B8A8_UNORM
> > >   MESA_FORMAT_Z_FLOAT32 -> MESA_FORMAT_Z_FLOAT32
> > > 
> > > i965 will use this for EGLImages and DRIimages.
> > > ---
> > >  src/mesa/Android.gen.mk          |  12 +++
> > >  src/mesa/Makefile.am             |   7 ++
> > >  src/mesa/Makefile.sources        |   2 +
> > >  src/mesa/main/.gitignore         |   1 +
> > >  src/mesa/main/format_fallback.h  |  31 +++++++
> > >  src/mesa/main/format_fallback.py | 180 +++++++++++++++++++++++++++++++++++++++
> > >  6 files changed, 233 insertions(+)
> > >  create mode 100644 src/mesa/main/format_fallback.h
> > >  create mode 100644 src/mesa/main/format_fallback.py
> 
> [snip]
> 
> > > +def main():
> > > +    pargs = parse_args()
> > > +
> > > +    formats = {}
> > > +    for fmt in format_parser.parse(pargs.csv):
> > > +        formats[fmt.name] = fmt
> > 
> > You could simplify this as:
> > formats = {f.name: f for f in format_parser.parse(pargs.csv)}
> 
> Thanks. I'll do that.
> 
> > 
> > > +
> > > +    write_preamble(stdout)
> > > +    write_func_mesa_format_fallback_rgbx_to_rgba(stdout, formats)
> > 
> > We really shouldn't write to stdout like this, it can cause all kinds of
> > breakages if there's ever a UTF-8 character (say ©) and the terminal doesn't
> > have a unicode locale it'll fail,
> 
> Ugh. I wasn't aware that Python's stdout was broken. Is Python's
> sys.stdout opened in "text" mode, and is that the cause of the
> brokenness?
> 
> Does it still fail if stdout is redirected to a file? Because that's the
> only case that matters here.

It's not python, it's the shell (I think). In this case it won't be a problem
since you don't have any non-ascii characters, but we've run into cases where
someone (like me) adds "Copyright © 3001 Mystery Science Theatre" and then
breaks some (but not many) systems. I know this because I added such a copyright
and broke someone's system, and eventually we narrowed it down to the fact that
this person didn't have a UTF-8 locale but I did, we ended up just removing the
© character from the output to fix it.

> 
> > if you just open the file you want (say one
> > passed as an argument) then it doesn't matter what the console supports. We do
> > this all over the place so it's not a blocker for me, but I still think it's a
> > bad idea to write to stdout.
> 
> > If you decide not to change this you at the very least need to call
> > stdout.flush() after write_func_mesa_format_fallback_Rgbx_to_rgba.
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