Bug#993550: gtk4: gsk repeat, repeat-negative-coords tests fail with ngl renderer on mips*el

[Simon McVittie]

Source: gtk4
Version: 4.4.0+ds1-3
Severity: normal
Tags: upstream
X-Debbugs-Cc: debian-mips at lists.debian.org
Forwarded: https://gitlab.gnome.org/GNOME/gtk/-/issues/4228

GTK 4 has a new scene-graph-based rendering model, "GSK", with an OpenGL
preferred implementation and a Cairo fallback. Its regression tests draw
various combinations of "render nodes" and check the results against
reference PNG images.

When using the "new" OpenGL renderer, "ngl", there's a weird rendering
glitch on mips*el on two tests involving repeating a pattern: the top
left pixel in each 2x2 block is darker than the other three.
For more details and comparison images:
https://gitlab.gnome.org/GNOME/gtk/-/issues/4228

Is there anything unusual about the OpenGL implementation on mips*el
that would cause this sort of thing? It seems to be using Mesa swrast_dri.so
(which I think is llvmpipe?), the same as any other machine without a GPU.

The "old" OpenGL renderer, "gl", does not seem to suffer from this - but
it is no longer the default, has been deleted in newer upstream versions,
and crashes in two (unrelated) tests on mipsel, so I'm going to disable
testing for "gl" in the next upload to avoid wasting machine resources and
developer time on it.

I'm going to skip these two tests on mips*el. I don't know what practical
effect this will have on GTK applications; I would recommend that people
who are interested in GUIs on mips*el should try the gtk-4-examples package
when mips*el builds become available, and find out.

    smcv