The question is in the title: I would like to get a ⩽ whenever I type ≤, and I don't understand how to tell unicode-math that it should re-map the character.
(I know that I could re-map my keyboard...)
Sorry if this is a duplicate, I couldn't find the aswer but I may have missed something.
As in classic tex you can set the math code of the typed character to be the character that you want in the output.
I set it mid-document here to show the effect, commented out is a setting that would set it for the whole document.
\documentclass{article}
\usepackage{unicode-math}
\AtBeginDocument{%
% \Umathcodenum`≤=\Umathcodenum`⩽ %
}
\begin{document}
$ a ≤ b $
\Umathcodenum`≤=\Umathcodenum`⩽ %
$ a ≤ b $
\end{document}
works with lualatex and xelatex.
If you prefer slanted inequalities, some math fonts (Erewhon-Math, XCharter-Math, LatoMath, etc.) provide "features" to turn on slanted inequalities. It doesn't happen at unicode-math level but relies on a font StylisticSet feature. Here is an example with XCharter-Math.
\documentclass[a4paper,12pt]{article}
\usepackage{amsmath}
\usepackage{xcharter-otf}
\parindent=0pt
\begin{document}
\[x\leq y \quad x\geqq y \quad x \lesseqgtr y \]
\verb+\setmathfont{XCharter Math}[Style={leqslant}]+
\setmathfont{XCharter Math}[Style={leqslant}]
\[x\leq y \quad x\geqq y \quad x \lesseqgtr y \]
\end{document}
and the output:
See the fonts' documentation for more information.
