Comment 16 for bug 1285184

I don't know what's the reason for using HarfBuzz (text shaping) that's still marked as experimental in Qt (I guess there's a good one), but the bug comes from qtbase when built with HarfBuzz support. QT_HARFBUZZ=old disables the use of HarfBuzz, as if not built in, so we can force that environment variable, we can switch back to a non-HarfBuzz build or we can backport that patch from trunk : https://codereview.qt-project.org/#change,78991