[Feature Request] Support for Combining Unicode Charactor

[czhang03]

Description

Combining charactors are characters that are intended to modify other characters. For example charactors like U+0304 (latex equivalent to \bar{}) and U+0302 (latex equivalent to \hat{}). However when typing b̄ (U+0062 U+0304) the bar does not show up in the compiled document

Add info or delete as appropriate:

• Relevant for XeTeX [Not Sure]
• Relevant for LuaTeX [Confirmed on LuaLatex]
• Issue tracker has been searched for similar issues? [Haven't found related issue]
• Links to <tex.stackexchange.com> discussion if appropriate [NA]

Minimal example demonstrating the issue

\documentclass{article}
\usepackage{unicode-math}
\setmathfont{texgyrepagella-math.otf}% filename only please!
\begin{document}
\[b̄\]
\end{document}

Further details

version:

package:     unicode-math
category:    Package
shortdesc:   Unicode mathematics support for XeTeX and LuaTeX
longdesc:    This package will provide a complete implementation of unicode maths for XeLaTeX and LuaLaTeX. Unicode maths is currently supported by the following freely available fonts: Latin Modern Math (Boguslaw Jackowski, Janusz M. Nowacki), TeX Gyre Bonum Math (Boguslaw Jackowski, , P. Strzelczyk, Janusz M. Nowacki), TeX Gyre Pagella Math (Boguslaw Jackowski, , P. Strzelczyk, Janusz M. Nowacki), TeX Gyre Schola Math (Boguslaw Jackowski, P. Strzelczyk, Janusz M. Nowacki), TeX Gyre Termes Math (Boguslaw Jackowski, P. Strzelczyk, Janusz M. Nowacki), DejaVu Math TeX Gyre (Boguslaw Jackowski, P. Strzelczyk, Janusz M. Nowacki), Asana-Math fonts (Apostolos Syropolous), STIX (STI Pub), XITS Math (Khaled Hosny), Libertinus Math (Philipp H. Poll and Khaled Hosny), and Fira Math (Xiangdong Zeng). The following fonts are proprietary with OpenType maths support: Lucida Bright Math (Charles Bigelow and Kris Holmes), Cambria Math (Microsoft), Minion Math (Johannes Kuster, typoma GmbH). As well as running XeTeX or LuaTeX, this package requires recent versions of the fontspec, expl3, xpackages, ucharcat and lualatex-math packages.
installed:   Yes
revision:    61719
sizes:       src: 269k, doc: 1845k, run: 509k
relocatable: Yes
cat-version: 0.8q
cat-license: lppl1.3c
cat-topics:  maths font-use luatex xetex unicode
cat-contact-home: https://wspr.io/unicode-math/
cat-contact-bugs: https://github.com/wspr/unicode-math/issues
cat-contact-repository: https://github.com/wspr/unicode-math/
collection:  collection-latexrecommended

System:

Fedora 38 Workstation with texlive-scheme-full

Build:

> lualatex test.tex
This is LuaHBTeX, Version 1.15.0 (TeX Live 2022/CVE-2023-32700 patched) 
 restricted system commands enabled.
(./test.tex
LaTeX2e <2022-06-01> patch level 5
 L3 programming layer <2022-12-17>
(/usr/share/texlive/texmf-dist/tex/latex/base/article.cls
Document Class: article 2021/10/04 v1.4n Standard LaTeX document class
(/usr/share/texlive/texmf-dist/tex/latex/base/size10.clo))
(/usr/share/texlive/texmf-dist/tex/latex/unicode-math/unicode-math.sty
(/usr/share/texlive/texmf-dist/tex/latex/l3kernel/expl3.sty
(/usr/share/texlive/texmf-dist/tex/latex/l3backend/l3backend-luatex.def))
(/usr/share/texlive/texmf-dist/tex/latex/unicode-math/unicode-math-luatex.sty
(/usr/share/texlive/texmf-dist/tex/latex/l3packages/xparse/xparse.sty)
(/usr/share/texlive/texmf-dist/tex/latex/l3packages/l3keys2e/l3keys2e.sty)
(/usr/share/texlive/texmf-dist/tex/latex/fontspec/fontspec.sty
(/usr/share/texlive/texmf-dist/tex/latex/fontspec/fontspec-luatex.sty
(/usr/share/texlive/texmf-dist/tex/latex/base/fontenc.sty)
(/usr/share/texlive/texmf-dist/tex/latex/fontspec/fontspec.cfg)))
(/usr/share/texlive/texmf-dist/tex/latex/base/fix-cm.sty
(/usr/share/texlive/texmf-dist/tex/latex/base/ts1enc.def))
(/usr/share/texlive/texmf-dist/tex/latex/amsmath/amsmath.sty
For additional information on amsmath, use the `?' option.
(/usr/share/texlive/texmf-dist/tex/latex/amsmath/amstext.sty
(/usr/share/texlive/texmf-dist/tex/latex/amsmath/amsgen.sty))
(/usr/share/texlive/texmf-dist/tex/latex/amsmath/amsbsy.sty)
(/usr/share/texlive/texmf-dist/tex/latex/amsmath/amsopn.sty))
(/usr/share/texlive/texmf-dist/tex/lualatex/lualatex-math/lualatex-math.sty
(/usr/share/texlive/texmf-dist/tex/latex/etoolbox/etoolbox.sty))
(/usr/share/texlive/texmf-dist/tex/latex/unicode-math/unicode-math-table.tex)))
(./test.aux)
Missing character: There is no ̄ (U+0304) in font cmmi10!
[1{/var/lib/texmf/fonts/map/pdftex/updmap/pdftex.map}] (./test.aux))
 488 words of node memory still in use:
   6 hlist, 2 vlist, 2 rule, 2 glue, 4 kern, 1 glyph, 7 attribute, 52 glue_spec
, 7 attribute_list, 1 write nodes
   avail lists: 2:23,3:8,4:2,5:22,6:2,7:36,8:2,9:20
</usr/share/texlive/texmf-dist/fonts/opentype/public/lm/lmroman10-regular.otf><
/usr/share/texlive/texmf-dist/fonts/opentype/public/tex-gyre-math/texgyrepagell
a-math.otf>
Output written on test.pdf (1 page, 3918 bytes).
Transcript written on test.log.

[ArchangeGabriel]

For LuaLaTeX at least, there is code to do so here and here.

[czhang03]

Thanks @ArchangeGabriel do you know any code that also incoperate U+0338, which is the \not combining charactor?