[gust-l] Latin Modern OS/2 & hhea metrics

[Alexis King]

Hello,

I’d like to start by thanking GUST for its work on Latin Modern and the
other TeX Gyre fonts—I am currently tinkering with a new implementation of
an OpenType math layout engine, and the GUST fonts have already proven
enormously helpful.

Onto my actual subject: I have discovered that the metrics for the Latin
Modern text fonts differ from the metrics for the other fonts (including LM
Math) in two respects:

1. In the OS/2 table, the USE_TYPO_METRICS bit of the fsSelection field
is not set.
2. The metrics in the hhea table differ (significantly) from the metrics
in the OS/2 table.

This seems unintentional to me, as the hhea metrics do not seem correct.
Unfortunately, I have discovered that Harfbuzz uses the hhea metrics if the
USE_TYPO_METRICS bit is not set, which results in the incorrect metrics
being used in my renderer (and a visible discrepancy between LM and LM
Math).

I am not sure how actively maintained these fonts are, but seeing as there
was a new LM release as recently as this year, I figured I’d at least
attempt to let you know. For now, I will patch the fonts to adjust the
metrics myself, but it would be wonderful if they could be updated in the
distribution.

Many thanks,
Alexis