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From: tml@hemuli.tik.vtt.fi (Tor Lillqvist)
Newsgroups: comp.text.tex
Subject: Bug in TeX in make_accent?
Message-ID: <TML.90Jul10181833@hemuli.hemuli.tik.vtt.fi>
Date: 10 Jul 90 22:18:33 GMT
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(I already sent this to texhax, but I didn't notice it showing up, so
I post here, too.)

I was reading the code for the procedure make_accent and the section
@<Append the accent with appropriate kerns, then set |p:=q|@> when I
noticed that the actual code does not correspond to the comment in
front of make_accent:

    Given an accent of width |a|, designed for characters of height
    |x| and slant |s|; and given a character of width |w|, height |h|,
    and slant |t|: We will shift the accent down by |x-h|, and we will
    insert kern nodes that have the effect of centering the accent
    over the character and shifting the accent to the right by
    $\delta={1\over2}(w-a)+h\cdot t-x\cdot s$.

OK, I understand that this assigns the slant of the font to s:

    s:=slant(f)/float_constant(65536);

But what is the slant of a character?  The actual code calculates the
same value as s:

    t:=slant(f)/float_constant(65536);

These values are used in calculating delta:

   delta:=round((w-a)/float_constant(2)+h*t-x*s);

As t = s, why not simplify this expression to:

   delta:=round((w-a)/float_constant(2)+(h-x)*s);

and forget about t?

Or should we use the italic correction of the character instead of
h*t?
--
Tor Lillqvist,
working, but not speaking, for the Technical Research Centre of Finland