Bug 1312500

So we'll need to do a bit more triage on this one, but I'm busy right now so just want to file it. Today's openQA French install test for Rawhide failed. The failure seems to be caused by some messed-up rendering of particular character combinations. Here's the failed step:

https://openqa.fedoraproject.org/tests/6079/modules/_do_install_and_reboot/steps/18

Note the incorrect rendering of the message above the "Redémarrer" (reboot) button, which is:

"Fedora est maintenant installé avec succès et est prêt à être utilisé !"

This text contains the two character sequence "êt" twice, and both times, it is incorrectly rendered - the characters are overlapped.

A similar issue can be observed on the main hub:

https://openqa.fedoraproject.org/tests/6079/modules/disk_guided_empty/steps/4

with the text "NOM D'HÔTE ET RÉSEAU" - the ÔT sequence is similarly incorrectly rendered.

As I'm writing this bug report, I've become pretty sure the bug is in Cantarell. If I paste the text êt into gedit (where my font is DejaVu Sans Mono) it renders fine. If I then change gedit's font to Cantarell it displays incorrectly (overlapped, like in the screenshots). If I change to another proportional font it also renders fine. So this seems like an error in cantarell. It also affects â and ô and ü and Ô and a few others, but not î or û. In gucharmap the affected characters actually display off-centre within the boxes in the character table, so you can see which characters are affected quite easily. Basically it seems like these characters are not correctly placed in the glyph grid or whatever it's called - they're nearly a whole character's width to the right of where they should be.