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Re: [ft-devel] Variable fonts: hhea/typo/win metrics interpreted differe

From: Behdad Esfahbod
Subject: Re: [ft-devel] Variable fonts: hhea/typo/win metrics interpreted differently for instances compared to static fonts?
Date: Wed, 30 Jan 2019 16:38:27 -0800

That's what line-gap is: gap between consecutive lines.  There is no line before the first line, and as such, no gap.

On Wed, Jan 30, 2019 at 4:37 PM Nikolaus Waxweiler <address@hidden> wrote:
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

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
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.


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