1916988 - Support CSS width/height properties on MathML elements

Status: RESOLVED FIXED

(Core :: MathML, task)

Description

[Frédéric Wang (:fredw)]

The generic thing is described here: https://w3c.github.io/mathml-core/#layout-algorithms

By default, the box metrics, offsets, baselines, italic correction and top accent attachment of the content box are set to the one calculated for the math content box. However if a different size is specified for the content box (via width, height or related properties), that size is used instead and the inline-start and block-start edges of the math content box are aligned with the ones of the content box, unless otherwise specified in a specific layout algorithm.

Some elements like mfrac specifies a different placement:

The math content box is placed within the content box so that their block-start edges are aligned and the middles of these edges are at the same position.

I'm not sure if the current text of MathML Core defines resolution of percentages, there seem to https://github.com/w3c/mathml-core/issues/76 and https://github.com/w3c/mathml-core/issues/77 about that with the consensus to use the size of a block container. But maybe we can just treat them as auto for now (maybe what chrome does too?).

Some tests are available here:

https://wpt.fyi/results/mathml/relations/css-styling?label=master&label=experimental&aligned&q=width-height

The spec does not mention box-sizing and always say width/height applies to the content box. I opened https://github.com/w3c/mathml-core/issues/257

Comment 1

[Frédéric Wang (:fredw)]

Attachment: mfrac-width-height.html

Comment 2

[Frédéric Wang (:fredw)]

Attachment: width-height-logging.patch

It seems we should just be able to get the values from StylePosition. With the attached patch and testcase I get something like this:

mfrac=0x750611046c70, measureonly=1
width: auto
height: auto
mfrac=0x750611046c70, measureonly=0
width: auto
height: auto
mfrac=0x750611047180, measureonly=0
width: 9000
height: 6000
mfrac=0x750611047690, measureonly=0
width: 1,000000
height: 0,500000

Comment 3

[Frédéric Wang (:fredw)]

Attachment: Bug 1916988 - Support CSS width/height properties on MathML elements. r=emilio

Comment 4

[Frédéric Wang (:fredw)]

(In reply to Frédéric Wang (:fredw) from comment #0)

Some tests are available here:

https://wpt.fyi/results/mathml/relations/css-styling?label=master&label=experimental&aligned&q=width-height

The latest version of the patch pass all these tests, but I believe test coverage is not sufficient.

Comment 5

[Frédéric Wang (:fredw)]

Attachment: Bug 1916988 - Set vertical offset of mfrac denominator from the baseline. r=emilio

Currently, we have

aDesiredSize.Height() = aDesiredSize.BlockStartAscent() +
  sizeDen.Height() + denMargin.bottom - sizeDen.BlockStartAscent() +
  denShift;

Then a call to InflateReflowAndBoundingMetrics respectively increments
aDesiredSize.BlockStartAscent() and aDesiredSize.Height() by
borderPadding.top and borderPadding.top + borderPadding.bottom.

Finally, we set

dy = aDesiredSize.Height() - sizeDen.Height() - denMargin.bottom -
     borderPadding.bottom;

which is equivalent to

aDesiredSize.BlockStartAscent() + denShift - sizeDen.BlockStartAscent()

Comment 6

[Frédéric Wang (:fredw)]

Attachment: mathml-width-height.html

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/47fb7922be7f
Set vertical offset of mfrac denominator from the baseline. r=emilio
https://hg.mozilla.org/integration/autoland/rev/dc8483828112
Support CSS width/height properties on MathML elements. r=emilio

Comment 8

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/48375 for changes under testing/web-platform/tests

Comment 9

[Serban Stanca [:SerbanS]]

https://hg.mozilla.org/mozilla-central/rev/47fb7922be7f
https://hg.mozilla.org/mozilla-central/rev/dc8483828112

Comment 10

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Upstream PR merged by fred-wang