Re: [ft-devel] Variable fonts: hhea/typo/win metrics interpreted differently for instances compared to static fonts?

[Nikolaus Waxweiler]

Even more testing.

ftview and Qt actually do the same GTK does: they don't add the line 
gap to the top, so text fields look compressed when the 
USE_TYPO_METRICS bit is set and typo asc+desc is smaller than hhea 
asc+desc. I'm not sure this is supposed to happen?! Didn't test MVAR 
modification.

Firefox and Chromium disregard FT_Face's ascender, descender and height 
attributes and use either hhea (I think; no USE_TYPO_METRICS) or typo 
metrics (USE_TYPO_METRICS), modifying typo metrics and the FT_Face 
attributes through the MVAR table therefore has no effect unless the 
USE_TYPO_METRICS bit is set.

The document body of a new text file in LibreOffice Writer 6.1.4.2 
stays the same  regardless of bit so I think LO Writer is doing it 
right. It doesn't support VFs though so I can't test MVAR modifications.

Behdad, I'm not completely sure of typo deltas in MVAR modifying the 
currently active metrics. Given that the hhea set is basically a legacy 
value and is probably taller spaced than the typo metrics, so we might 
end up doing things the designer didn't intend? What FF/Chromium do 
strikes me as saner, i.e. writing typo metrics to FT_Face 
ascender/descender/height when USE_TYPO_METRICS is set :/

Otherwise, I'd say unless anyone has objections, I think we can merge 
the branch.