[Development] CI - Mesa warning "couldn't open dxtn.dll" on Windows machines

[Zack Rusin]

On Fri, Aug 9, 2013 at 5:39 AM, Koehne Kai <Kai.Koehne at digia.com> wrote:
> Hi,
>
> I just ran into suspicious compiler warnings in the CI system logs for Windows:
>
>   Mesa warning: couldn't open dxtn.dll, software DXTn compression/decompression unavailable
>   Mesa warning: couldn't open dxtn.dll, software DXTn compression/decompression unavailable
>   Mesa warning: couldn't open dxtn.dll, software DXTn compression/decompression unavailable
>   Mesa warning: couldn't open dxtn.dll, software DXTn compression/decompression unavailable
>
> (from
> http://testresults.qt-project.org/ci/QtDeclarative_stable_Integration/build_00830/win32-msvc2010_developer-build_qtnamespace_Windows_7/log.txt.gz
> )
>
> Digging a bit it seems that some logs even back from 2012 have these errors, e.g.
>
> http://testresults.qt-project.org/ci/QtBase_master_Integration/build_04706/win32-msvc2010_Windows_7/log.txt.gz
>
> I don't think the warning itself is crucial. Anyhow, did anyone ever checked out whether there's an easy fix for it?

I guess that depends on the patent situation in your favorite country
and/or your willingness to be an outlaw, which is generally connected
to your ability to grow wickedly awesome mustache. We use an external
dxtn library for s3tc compression, which is governed by patents and
thus the code for it can't be distributed with free software mesa
itself. It's just four (or five) entrypoints that need to be shipped
out to that external library that's dlopened at runtime. If you just
want to make the errors stop on your test systems then you can just
compile some version of libtxc_dxtn using mingw to produce dxtn.dll,
e.g.
http://cgit.freedesktop.org/~mareko/libtxc_dxtn/
or you can check the entry points inside libtxc_dxtn and just create a
file with empty stubs for those functions and compile that into
dxtn.dll.

I guess the second one would work for many of Qt users (a fake
dxtn.dll with empty stubs for those entrypoints) but the whole reason
mesa warns about this stuff, is that having a gl implementation that
doesn't support s3tc is a bit like having a dance party without music
- possible but everyone just looks stupid.

z