Bug#1094820: gtk4 needs dependency on libpng >= 1.6.45

[Jeremy Bícha]

Source: libpng1.6
Version: 1.6.46-1
Severity: serious
Control: affects -1 src:gtk4
X-Debbugs-CC: locutusofborg at debian.org, gtk4 at packages.debian.org

gtk4 4.16.12+ds-2 added a patch to build with libpng >= 1.6.45. The
patch means that GTK4 won't work with older libpng versions. This is
seen in all the autopkgtest failures from gtk4 reverse depends.

https://tracker.debian.org/pkg/gtk4

This could be fixed by adding a binary depends in gtk4 like
https://salsa.debian.org/gnome-team/gtk4/-/merge_requests/35

I'd rather see libpng1.6 get an update to either
1. Switch from shlibs to a symbols file with Build-Depends-Package
2. Or update the shlibs file to >= 1.6.45

gtk4 would still need an upload in those cases against the new libpng
but only the Build-Depends would need to be updated and Depends:
${shlibs:Depends} would fill in the correct minimum version of libpng.

Thank you,
Jeremy Bícha