After landing the FontMetrics abstraction from bug 51456, vertical line metrics are incorrect.
There's a hack in SimpleFontDataMac.mm that modifies lineGap/descent for a certain vertical font. That hack now influences the lineSpacing, where it shouldn't.
Attaching a patch soon, to restore the old behaviour.
Created attachment 79844 [details]
Comment on attachment 79844 [details]
Landed fix in r76445. Let's see..