This is a meta-bug to track issues related to <semantics/>. Currently, we use CSS to display only the first child. We should probably write a class nsMathMLsemanticsFrame to have a better control on what should be displayed or not. Also, this should probably help having the same behavior as other frames and hence fixing bugs.

I've just tried to implement a NS_NewMathMLsemanticsFrame and it allows to fix bug 468059, bug 512418, bug 523037 and bug 523045. I'll attach a patch when I've made reftests from their testcases.

This patch fixes the four bugs mentioned above as well as the special case of bug 21479 related to <semantics/>.

In bug 468059 comment 1 you suggested just creating an nsMathMLContainerFrame. Did that not work? Why did you create a new frame type here?

Actually, I haven't tried to directly use a NS_NewMathMLContainerFrame. I just need nsMathMLsemanticsFrame to get embellished-op data from the first child in TransmitAutomaticData(). Although I can implement a function TransmitAutomaticData in NewMathMLContainerFrame that does this job when mContent->Tag() == semantics_, I find it cleaner to work in a separate class. Also, this class could be useful if one improves the behavior of the <semantics/> element: http://mxr.mozilla.org/mozilla-central/source/layout/mathml/mathml.css#414

Comment on attachment 443701 [details] [diff] [review] Patch That makes sense.