# [Webkit-unassigned] [Bug 107856] mathml fences often look bad

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Sat Jun 21 02:30:43 PDT 2014

https://bugs.webkit.org/show_bug.cgi?id=107856

--- Comment #6 from Frédéric Wang (:fredw) <fred.wang at free.fr>  2014-06-21 02:31:02 PST ---
>
> Actually, as I read the spec, the <mfenced> in this case isn't even really legal, since there's no closing fence.

I think this testcase has been generated by a previous version of MathJax which incorrectly used <mfenced> to convert thinks like

\left{ ... \right.

into

<mfenced open="{" close=""> ... </mfenced>

which per http://www.w3.org/TR/MathML3/chapter3.html#presm.mfenced is equivalent to

<mrow>
<mo>{</mo>
<mrow>
...
</mrow>
<mo></mo>
</mrow>

I'm not sure it is very good semantically to have this empty <mo> as a closing fence. That's one more good reason not to use the <mfenced> element. Fortunately, MathJax stopped using that element in the most recent versions.

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