mtable support

[fred-wang]

MathML core defines a very basic support for mtable, essentially based on CSS.
Do we want more?

Can we improve alignment / gaps using css (maybe https://www.w3.org/TR/css-align-3/ )?
Should features be polyfilled instead?

Related to that is w3c/mathml#67

[davidcarlisle]

I think the mathml microsyntaxes for column alignments

groupalign=
         "{decimalpoint left left decimalpoint left left decimalpoint}"

etc can probably go from core, however it would be really useful (almost essential) if decimal column alignment columns could be specified (somehow) whether that is by adding decimal column alignment to css generally including html tables or as a specific feature for mtable I don't really know,

If that could be added somehow then probably most of the mathml3 alignment attributes can be polyfilled as they are only an authoring convenience specifying alignments at the row or table level to avoid specifying them on every cell.

[fred-wang]

Basic tests are at https://w3c-test.org/mathml/presentation-markup/tables/

[NSoiffer]

The elementary math polyfill I wrote produces a table. I'd rather produce an mtable, but I decided against it until there is a robust implementation of mtable in browsers. I hope that mtable will allow CSS for styling in core. For the record and to provide motivation as to what needs to be supported in mtable, the polyfill uses the following CSS settings on the table/tr/td:

• border-collapse
• border-spacing
• vertical-align
• font-size
• border
• height
• padding
• text-align

It also makes use of the following to deal with carries and crossouts, but it is possible (maybe likely) that someone with better CSS knowledge would do them differently:

• line-height
• display (inline-block and and inline-table to get alignment on first/last row of a multiline td -- need nth line to handle a very rare case that is not currently handled.

crossouts make use of :before/:after along with position:absolute, right, top, width, and transform: skewY. If I could use an mtable, they would be done with menclose and would hopefully look a little better.

[NSoiffer]

Adding need polyfill label because none of the attrs are currently listed as being in core. This also needs to be done for mtr and mtd.

I agree with @davidcarlisle that it is sad if a standard for laying out math doesn't support something basic like decimal alignment. I'm baffled why this isn't supported in CSS already -- I couldn't find it if it already exists.

[fred-wang]

I also wonder whether we actually want https://mathml-refresh.github.io/mathml-core/#dfn-frame ; this attribute was inherited from the original implementation note but we never discussed whether that's needed or if the proposed CSS makes sense. If we really do want it, we should also add tests.

[NSoiffer]

Since core doesn't support the other mtable attrs (some of which are much more useful than frame), it seems strange to only support frame.

[faceless2]

something basic like decimal alignment. I'm baffled why this isn't supported in CSS already -- I couldn't find it if it already exists.

The "align to a string" values is defined in https://www.w3.org/TR/css-text-4/#text-align-property - I'm sure I recall this in css-text-3 at some point, if it's been pushed back to revision 4 I'd presume that was due to either lack of implementer interest and/or implementations, of which there are - to my knowledge - none.