# [NTG-context] italic correction after math

Hans Hagen pragma at wxs.nl
Tue Feb 13 19:21:21 CET 2018

On 2/13/2018 6:51 PM, Ulrike Fischer wrote:
> Am Tue, 13 Feb 2018 16:26:10 +0100 schrieb Hans Hagen:
>
>
>> basically it boils down to fonts being bad: traditional tex fonts cheat
>> about the width for italics and have lots or corrections that get always
>> added as a starter and removed in some cases (heuristics); opentype on
>> the other hand has proper widths and only applies italics in some cases
>
> But xits is in this case not lying about the italic. The cal-P has a
> large overhang and one would like to take this somehow into account.

well, how should math (or whatever) know what comes after it ... in
fact, italic correction should be clever enough to decide if what comes
after it is also italic

> Actually the italic is taken into account *inside* math.
> This here inserts \kern1.52 after the "F0151 and \kern2.45 after the
> "1D4AB (the math.italic values of these glyphs):

only when it binds with a character

> \tracingoutput1 \showboxbreadth\maxdimen \showboxdepth\maxdimen
> \input luaotfload.sty
>
> \font\xits={file:xits-math.otf} at 10pt
> \textfont0=\xits
> $\Umathchar"7"0"F0151 \Umathchar"7"0"1D4AB \Umathchar"7"0"78$
> \bye
>
> The problem is the boundary between math and text. There seem to be
> no way to insert automatically or manually the kern if the \cal P
> (\Umathchar"7"0"1D4AB) is the last char in the math.

maybe inserting a zerowidthjoiner character helps

$.... \Uchar"200D$

> Btw: I found in the luatex manuel the options
>     \mathoption nocharitalic 1
> but it seems to do nothing (the example in the manual show imho
> identical output).
these flags are just for testing (the mathoption ones will go away
eventually which is why we use \mathoption) .. there are other
\math*mode etc parameters

Hans

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