{Reconciling \pkg{unicode-math} with \LaTeXe\ mathematics}
{Will Robertson}
{The \pkg{unicode-math} package was developed before Unicode was widely
used, and some of its original features and design decisions have
needed to be re-considered as \XeTeX{} and Lua\TeX{} have become more
popular. In \pkg{unicode-math}, there is currently a mismatch between
the interface provided for OpenType/Unicode maths fonts and the
original interface of \LaTeX{} itself, since they provide different
alphabets for different purposes. Specifically, in \LaTeXe{}
\cs{mathbf} selects a text-based font and uses it in a maths
context. In \pkg{unicode-math}, \cs{mathbf} selects bold math
glyphs from the Plane 1 Unicode mathematics range. This has some
subtle implications depending on usage. More problematically,
\cs{mathit} produces incorrect spacing with \pkg{unicode-math}
since Unicode mathematics doesn't provide glyphs for multi-letter
italics, and \pkg{unicode-math} overlooked this essential requirement.

Replacing the maths font commands in this way was a poor design
decision when considering backwards compatibility, and in 2015 this is
causing problems with authors wishing to switch to OpenType Unicode
fonts. In this talk, I'll present what has been provided historically
for alphabetic maths fonts in \LaTeXe{}, and what Unicode mathematics
provides instead. A brief retrospective will be given on \pkg{unicode-math},
emphasising the design decisions that lead to the current
incompatibilities, with possible solutions.}