Comment 18 for bug 1556457

https://launchpadlibrarian.net/251449771/upstream_git-log.txt has a lot of changes which seem desirable, and not actually much in terms of new features (aside from documentation updates). However, the sheer number/size of the changes makes this risky, particularly as testing this is extremely difficult (e. g. how reliably can we test Ubuntu/Kubuntu/Xubuntu in Bengali, Thai, various CJK, or e. g. Georgian and are confident that fonts look right?).

I don't know much about fontconfig, but is there any better/simpler way of mass-testing with our fonts than visual inspection? I. e. can we compare which glyphs are being used from which font (for our default font selection) with the current and the new version, to ensure that we don't suddenly swap fonts around, or if that happens, that this is expected? Is there some way to iterate over the unicode glyphs for fonts that we have available, to ensure that the new fontconfig does not crash on those? Any other ideas for a test plan?

Does this need any other dependencies (freetype etc.)? I. e. if 2.11.94 causes trouble, how easily can we go back to 2.11.1?