[LyX/master] MathML: allow XArrow to stretch.

[Thibaut Cuvelier]

commit f0bf41f5746dd6edd1815b52cf7be72fee1b1d8e
Author: Thibaut Cuvelier <tcuvelier at lyx.org>
Date:   Wed Dec 8 01:36:24 2021 +0100

    MathML: allow XArrow to stretch.
    
    Based on https://www.lyx.org/trac/ticket/12221#comment:10
    by lynx
---
 src/mathed/InsetMathXArrow.cpp |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/src/mathed/InsetMathXArrow.cpp b/src/mathed/InsetMathXArrow.cpp
index a9ed6b0..dceb794 100644
--- a/src/mathed/InsetMathXArrow.cpp
+++ b/src/mathed/InsetMathXArrow.cpp
@@ -161,7 +161,8 @@ void InsetMathXArrow::mathmlize(MathMLStream & ms) const
 	}
 
 	ms << "<" << from_ascii(ms.namespacedTag("munderover")) << " accent='false' accentunder='false'>"
-	   << arrow << cell(1) << cell(0)
+	   << MTagInline("mo") << arrow << ETagInline("mo")
+	   << cell(1) << cell(0)
 	   << "</" << from_ascii(ms.namespacedTag("munderover"))<< ">";
 }