Bug#1080327: gtk4: intermittent test failure in gsk/scaling test: generated texture for r16g16b16a16-float* doesn't match reference

[Simon McVittie]

Control: tags -1 + upstream
Control: forwarded -1 https://gitlab.gnome.org/GNOME/gtk/-/issues/6978

On Mon, 02 Sep 2024 at 10:56:46 +0100, Simon McVittie wrote:
> While working on other FTBFS issues that are fixed in 4.15.6+ds-1, I saw
> an intermittent test failure on multiple architectures (amd64, armel, s390x)
> in the gsk / scaling test.
...
> The obvious next step would be to produce more diagnostic output on
> failure.

https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/7680

Based on that, I've identified two different failure modes, depending on
the random pixel values that the test generates:

* alpha == 0: https://gitlab.gnome.org/GNOME/gtk/-/issues/6977
* alpha == 0xf1/0x100: https://gitlab.gnome.org/GNOME/gtk/-/issues/6978

I can only reproduce #6977 on my laptop and not on porterboxes, so I'm
going to assume that the failure I saw on porterboxes is #6978.

    smcv