User Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:34.0) Gecko/20100101 Firefox/34.0 (Beta/Release) Build ID: 20140815030202 Steps to reproduce: Visit http://www.mathjax.org/demos/tex-samples/, or run MathJax on $$\mathbf{V}_1 \times \mathbf{V}_2 = \begin{vmatrix} \mathbf{i} & \mathbf{j} & \mathbf{k} \\ \frac{\partial X}{\partial u} & \frac{\partial Y}{\partial u} & 0 \\ \frac{\partial X}{\partial v} & \frac{\partial Y}{\partial v} & 0 \end{vmatrix}$$ Actual results: The table in the display is aligned to the first row, instead of centered vertically, so there is a large white space above the table Expected results: The table should be aligned to vertical center

This bug was also reported at MathJax: https://github.com/mathjax/MathJax/issues/891 but since it only occurs on my Firefox Nightly 34.0a1 build, they suggested that I report it here.

[Tracking Requested - why for this release]: regression Regression window(m-c) Good: https://hg.mozilla.org/mozilla-central/rev/a4dcfbebcb58 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:34.0) Gecko/20100101 Firefox/34.0 ID:20140728034717 Bad: https://hg.mozilla.org/mozilla-central/rev/70b3fc807a70 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:34.0) Gecko/20100101 Firefox/34.0 ID:20140728063421 Pushlog: http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=a4dcfbebcb58&tochange=70b3fc807a70 Regression window(m-i) Good: https://hg.mozilla.org/integration/mozilla-inbound/rev/ca1c3ca7d314 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:34.0) Gecko/20100101 Firefox/34.0 ID:20140725154409 Bad: https://hg.mozilla.org/integration/mozilla-inbound/rev/eb01c53fd879 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:34.0) Gecko/20100101 Firefox/34.0 ID:20140725155048 Pushlog: http://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=ca1c3ca7d314&tochange=eb01c53fd879

In local build Last Good: 5edaa0a67cb8 First Bad: 22cfcffb5a8b Triggered by: 22cfcffb5a8b Andy Anderson — Bug 369778 - RegExp capturing groups that aren't matched during a match (because of, say, a *?+{n}{n,m} quantifier that means they're never used) should be matched as |undefined|, not as the empty string. r=jwalden

I commented in the MathJax issue: https://github.com/mathjax/MathJax/issues/891#issuecomment-52482708

So is this on our side or theirs?

(In reply to Benjamin Kerensa [:bkerensa] from comment #5) > So is this on our side or theirs? I'm not yet entirely sure. I thought it was certain to be on their side, but now I think it might be bug 1053944, and thus something we might/could work on on our side.

Update: This bug has been patched and fixed on the MathJax end, so if it is deemed that there is nothing Mozilla aught to do about this bug then it's probably safe to close.

Thanks, di.gama. Given that we encountered more breakage through the RegExp.$N behavior change, we still might revert that. Still, it's good to hear that you were able to work around the issue on your end.

Not tracking based on Comment 7