[css2] paint order of table caption relative to parts of the table should be better defined

[dbaron]

Based on a discussion I just had with @mattwoodrow:

There are some references in the Stacking Order appendix to "if the element is a ... table". It's not clear to me if these references mean to refer to "is a table grid box" or "table wrapper box". It would be nice and simple if they referred to table grid box, and the table wrapper box were just a regular block that treated its children (captions and table grid) in content order.

However, the problem with that is that the caption's content order might be in the middle of the table grid (though it must be between row groups). This makes it less clear about how the caption is supposed to be ordered in the paint order relative to pieces of the table. Having to order the caption in the middle of the table is complicated.

I think this needs to be better defined. It may also require some testing of existing implementations.

[dbaron]

(I also don't remember if row-spanning is allowed to cross row groups. If it's not, this could also be simplified by moving the rules for tables to being rules for row groups, although that might be a bit weird for the table background.)

[FremyCompany]

I just took a very brief look, but I'm now wondering how that actually matters in practice; I can't imagine a case where this matters and as a result I can't truly say I understood the problem.

My understanding is that it is basically impossible for the table grid (and its content) and the captions to overlap, unless a /transform is applied to the captions; that would make them move above all the other items, wouldn't it? (you can't apply a transform on the grid box)

[FremyCompany]

(also, to anwer your question, cells cannot span across rowgroups)