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Interaction between height and baseline alignment #259
Description
Follow-up of #75
I've worked on the Firefox implementation of width/height, tried to follow what MathML Core / Chromium do and I'm adding missing test coverage.
I just uploaded a testcase for various situations: https://bug1916988.bmoattachments.org/attachment.cgi?id=9425482
One behavior I'm not sure is what happens when we specify a CSS height that is smaller than the line-ascent. It seems Chrome sets the corresponding height and does not clamp the line-ascent, so baseline alignment with other siblings stay the same. I think that makes sense to me and that's what I'm implementing in Firefox, but we might need some extra text is the spec to clarify.
Related to that, when we specify a height for the "content box" that is different from the one of the "math content box", then MathML Core (and Chromium, in what I'm implementing in Firefox and in WPT tests I'm adding) says to align the top edges of these boxes. But maybe what is more natural is to tweak the line-ascent/line-descent evenly so that the baseline is unchanged.
Activity
Support CSS width/height properties on MathML elements.
Bug 1916988 - Support CSS width/height properties on MathML elements.…
Bug 1916988 - Support CSS width/height properties on MathML elements.…
Bug 1916988 - Support CSS width/height properties on MathML elements.…
Bug 1916988 - Support CSS width/height properties on MathML elements.…
Support CSS width/height properties on MathML elements. (#48375)
Bug 1916988 - Support CSS width/height properties on MathML elements.…
fred-wang commentedon Oct 14, 2024
FWIW, I'm implementing Chromium's behavior in WebKit too.
davidcarlisle commentedon Oct 28, 2024
@fred-wang
The WG discussed this on the call 2024-10-28 and we think this baseline alignment does sound more natural.
Support CSS width/height properties on MathML elements
bkardell commentedon Aug 22, 2025
Does this require spec changes?
fred-wang commentedon Aug 23, 2025
I think we would need to check the status in Firefox and whether it remains FIXME in the code, but likely not urgent to change anything in the spec for now.
bkardell commentedon Aug 25, 2025
It's urgent in the sense that we are trying to move it toward REC :)
NSoiffer commentedon Aug 25, 2025
We discussed this today.
It also appears that we need to say something about this in the spec. Probably where line-ascent is defined.
Bug 1916988 - Support CSS width/height properties on MathML elements.…