I wanted to uses a different \ell from that in XITS, so I thought I'd try an interesting feature of unicode-math.sty allowing for the use of multiple fonts.
The following code (MacTeX 2016, recently updated) works for the \ell but causes another unexpected problem:
% !TEX encoding = UTF-8 Unicode
% !TEX TS-program = XeLaTeX
\documentclass{book}
\usepackage{unicode-math}
\setmainfont[Ligatures=TeX]{XITS}
\setmathfont{XITS Math}
\setmathfont{Lucida Bright Math OT}[range={"2113},Scale=0.8]
\usepackage{microtype}
\begin{document}
$\big( \big)$
\end{document}
produces this output:
The little boxes indicate missing glyphs. If I comment-out the second \setmathfont line:
\usepackage{unicode-math}
\setmainfont[Ligatures=TeX]{XITS}
\setmathfont{XITS Math}
%\setmathfont{Lucida Bright Math OT}[range={"2113},Scale=0.8]
\usepackage{microtype}
the output is normal:
Am I misunderstanding this? Or, hopefully, is there a fix/workaround?


unicode-mathversion 0.8j, released 2018-01-07. – egreg Jan 10 '18 at 12:05