Follow-up Comment #4, bug #67544 (group groff): At 2026-01-27T13:53:05-0500, Dave wrote: > Follow-up Comment #3, bug #67544 (group groff): > > [comment #2 comment #2:] >> The URW fonts have more kerning data. >> >> See bug #65974#28 for getting those into the "devps" directory. > > I know the URW fonts have greater glyph coverage, but I don't know > their provenance related to the regular fonts. Do the URW fonts only > _add_ glyphs--that is, are the glyphs common to both fonts identical? > Or can there be minor variances in glyph shapes? If the latter, > importing metrics from one to the other, even for the common > characters, wouldn't be typographically valid.
My understanding of the purpose of the URW fonts--which is only
folkloric in nature--is that they're intended to be metrically
compatible with the fonts of the Adobe PostScript level 2 standard.
If that's correct, then there _can_ be minor variances in glyphs shapes,
as with, say, the selection of an open versus closed descender bowl in
the lowercase "g", but none such that they would affect the _metrics_.
For groff's purposes, metrics are only as follows, and do not include
parameters that influence, say, hinting. (Except where hints would
alter the metrics described below, and as far as I know, none do.)
groff_font(5):
The form of the metrics field is as follows (on one line; it may be
broken here for readability).
width[,[height[,[depth[,[italic‐correction[,[
left‐italic‐correction[,[subscript‐correction]]]]]]]]]]
...
The width subfield gives the width of the glyph. The height
subfield gives the height of the glyph (upward is positive); if a
glyph does not extend above the baseline, give it a zero height,
not a negative height. The depth subfield gives the depth of the
glyph——that is, the distance below the baseline to which the glyph
extends (downward is positive); if a glyph does not extend below
the baseline, give it a zero depth, not a negative depth. Italic
corrections apply when upright and slanted (italic or oblique)
styles are typeset adjacently. The italic‐correction is the amount
of space to add after a slanted glyph to be followed immediately by
an upright glyph. The left‐italic‐correction is the amount of
space to add before a slanted glyph to be preceded immediately by
an upright glyph. The subscript‐correction is the amount of space
to add after a slanted glyph to be followed by a subscript; it
should be less than the italic correction.
I suspect that these parameters are coarse from a font designer's
perspective, and that much can be done with "minor variances in glyph
shape" without altering them.
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