[css-display] Make table-caption and table-cell <display-outside> values #3940
Description
Splitting out from @MatsPalmgren's comment in #3771:
Random thought: maybe
markershould be adisplayvalue rather than apositionvalue.It should be a new
<display-outside>value, or an additional keyword, in that case. I think it would ruin this feature if you can't specify the marker's internal layout to begridetc. Comparetable-caption/cell, which has severely limited layout because you can't specify a<display-inside>value.
::marker,table-caption,<legend>and<summary>have a lot in common in this respect. They are in-flow by default, but not quite, since they aren't flowed normally together with other children in the layout context. S 6655 emantically, they're like a third variation of "flow" (besides in-flow, out-of-flow). I wonder if we should model them in the same way for that reason. Either through<display-outside>or a new property. E.g.
<display-outside> = block | inline | run-in| marker | caption | cell | legend | summaryThis would add a lot more power to authors to control the layout without having to add wrapper elements. E.g.
<caption>would havedisplay: caption flow-rootby default, but you could also specify<caption style="display: caption grid">to display its children using Grid layout.
legend | summaryallows an arbitrary child to be displayed as the rendered legend/summary in a fieldset/details element.(FYI, It would be trivial to support table captions/cells with internal grid/flex/table layout in Gecko. The only thing missing is some way to specify it in CSS.)
It would be trivial to make table-caption a <display-outside> value in the spec, too. Should we do it? (By which I mean, does anyone actually want to implement it?)