[bug #61751] want metric 'type' data for character-cell fonts

[G. Branden Robinson]

URL:
  <https://savannah.gnu.org/bugs/?61751>

                 Summary: want metric 'type' data for character-cell fonts
                 Project: GNU troff
            Submitted by: gbranden
            Submitted on: Fri 31 Dec 2021 10:08:39 PM UTC
                Category: Font - others
                Severity: 1 - Wish
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None

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Details:

The "character type" (ascender, descender, both, neither)
information for nroff device fonts is typically absent.  At
first I thought this was a defect in groff.  I then checked
Heirloom and found it was consistent with that implementation,
and also with Unix V7 nroff.

I'm not aware of any documentation anywhere that mentions this
fact.  CSTR #54 doesn't (nor does it give a formal definition
of the ascender datum--its definition of "ascender", we must
infer from its example of "Y", is a glyph that is taller than
than the x-height of the font, not one with a serif or other
feature that renders it taller than a capital letter in the
font).

I reckon this isn't high-priority since nothing seems to really
expect to use the `ct` register after interpolating a \w escape
sequence on an nroff device to perform vertical spacing
adjustment.

In the meantime I intend to document it, though.





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