Bug#1058740: gtk4,librsvg: big-endian support is at risk of being removed

Source: gtk4,librsvg
Severity: important
Tags: upstream help
X-Debbugs-Cc: [email protected], [email protected]

gtk4 had a recent test failure regression on s390x and other big-endian
architectures like ppc64 (#1057782). I sent this upstream to
https://gitlab.gnome.org/GNOME/gtk/-/issues/6260 and proposed a patch in
https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/6653, but upstream is
reluctant to apply the patch because they think it is the wrong solution:

> I would rather people fix the actual issue, which is the large table
> mapping GdkMemoryFormat to the corresponding GL format (and I bet the
> one for dmabufs is broken, too, but we don't have tests for that).

librsvg also has long-standing unsolved endianness-related issues, most
likely in one of its dependencies (#1038447, which has affected bookworm
since September 2022).

The GNOME team does not have big-endian hardware where we can run manual
tests, so we do not know how much of an impact this has on practical
usability of GTK and librsvg on big-endian architectures: it's entirely
possible that they have always been misrendered or broken on big-endian,
but the bug was never reported because there were no users, and we
are only noticing this now as a result of wider test coverage being
introduced.

If porters are interested in having GTK and librsvg continue to be
available on big-endian, please work with upstream to get them to a point
where endianness-specific bugs can be taken seriously in the upstream
projects. I do not consider doing this downstream-only to be a solution.

If endianness-specific issues become a blocker for the Debian release
process at some point in the future, then it is likely that I will have
to start the process of doing architecture-specific removals for these
packages and their reverse dependencies. For s390x this is likely to
have little user-visible effect, because I find it unlikely that there
are genuinely users running GUI applications on IBM mainframes, but for
-ports architectures this will probably be a larger regression.

Thanks,
    smcv