From 0e94edae74ae85e87ceafcebd35bbdafb25d70f4 Mon Sep 17 00:00:00 2001
From: Ruixi Zhang <39968857+RuixiZhang42@users.noreply.github.com>
Date: Wed, 25 Nov 2020 12:00:40 -0500
Subject: [PATCH] Force classical version of \genfrac

See https://github.com/latex3/latex2e/issues/432 and https://github.com/latex3/latex2e/issues/433
---
 mtpro2-patch.tex | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/mtpro2-patch.tex b/mtpro2-patch.tex
index 1c426fd..c01f77c 100644
--- a/mtpro2-patch.tex
+++ b/mtpro2-patch.tex
@@ -552,6 +552,16 @@
       used. So ##1 and so on will be gobbled and have no effect.}%
   }%
 }
+%   Since mtpro2 is TFM-based, we should force \genfrac to be the
+% classical version to avoid (a) bugs across different mathstyles
+% (see https://github.com/latex3/latex2e/issues/432) and (b) slow
+% processing (see https://github.com/latex3/latex2e/issues/433).
+\DeclareRobustCommand{\genfrac}[4]{%
+  \def\@tempa{#1#2}%
+  \edef\@tempb{\@nx\@genfrac\@mathstyle{#4}%
+    \csname @@\ifx @#3@over\else above\fi
+    \ifx\@tempa\@empty \else withdelims\fi\endcsname}
+  \@tempb{#1#2#3}}
 % https://github.com/latex3/latex2e/issues/160
 \patchcmd\math@cr@@@aligned
   {\next@ \cr}