[mythtv-users] Seasonal theme experiments

[Mark Kendall]

On Fri, 11 Dec 2020 at 10:01, Stuart Auchterlonie
<stuarta at squashedfrog.net> wrote:

> Is it worth handling a file reference in the theme.xml file, so that
> rather than having to embed GSL into the theme.xml, the GSL can be
> contained in it's own file (shipped along with the theme) and it's
> loaded out of that file instead?
>
> It does seem a cleaner way to do it. (my 2c's)

That would be my long term goal - the initial code is very much just a
proof of concept.

Moving the shaders into their own files also allows the themer to
reuse them - I would expect that in most cases the vertex shader will
be the same. We should probably be caching the shaders as well.

The bigger issue is portability; with half an eye on how this would be
implemented on Vulkan, but also GLSL versions. Strictly speaking an
OpenGL implementation does not have to offer compatibility with older
versions and all of our current OpenGL shaders target GLSL 1.2 (GLSL
ES 1.0)  (although they appear to work with GLSL 1.1 as well). So in
theory they may not work on newer OpenGL instances but I have seen no
references to issues in the 'wild'; I suspect all of the major vendors
just allow backwards compatibility.

Qt works around this by writing all of their shaders with 'vulkan
style' GLSL and converting to other formats. We would probably need to
do something similar; we already have glslang support in master -
though conversion should really be done offline.

Regards
Mark