[bug #57506] Suspicious "slant" values in devps/TI, devlbp/HI, devlbp/HBI

[Dave]

Follow-up Comment #10, bug #57506 (project groff):

[comment #6 comment #6:]
> This could be tested, but it's not obvious how: the "is used by
> groff" line above is awfully vague about what accent-placing
> mechanism uses the value.  The \o escape, for instance,

I tested this using a character that doesn't have a precomposed form in any
font on my system, so groff can't fall back to that behind the scenes; it has
to combine the letter and the diacritic.

As predicted, "slant"'s parameter has no effect on \o's glyph placement:

echo '\fIThis is Spi\o@n\[u00A8]@al Tap' | groff

This produces the same output no matter what "slant" value you put in font
description file "TI".

The next thing I tried was a Unicode combining form of the diacritic glyph. 
However, none of the typesetting fonts that ship with groff contain these
characters.

$ echo '\fIThis is Spin\[u0308]al Tap' | groff > /dev/null
troff:<standard input>:1: warning: special character 'u0308' not defined

(This works for utf8 output, however.

$ echo '\fIThis is Spin\[u0308]al Tap' | groff -Tutf8 -P-i | cat -s
This is Spin̈al Tap

No telling how your browser will render that output line, though.)

I do have a locally installed italic font that contains U+0308, and using that
makes the above command line work.  But as before, changing the "slant"
parameter in the font description file has no effect on the placement of the
¨.

So I'm still in the dark about what mechanism afmtodit(1)'s "is used by groff"
refers to.


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