[css-display][css-tables][css-flexbox][css-grid] 'block' outer display type does not always produce a block-level box #1704

CSS Tables says that table generates a block-level table.

CSS Flexbox says that flex generates a block-level flex container.

CSS Grid says that grid generates a block-level grid container.

CSS Display says the above plus things like that block generates a block box.

However, this is only true in flow layout. Outside of flow layout, the block outer display type can also generate a flex-level or grid-level principal box.

I think there are two reasonable solutions:

• Say that "flex-level" and "grid-level" are sublevels of "block-level" instead of entirely different things. So we could say e.g. that a flex item is both flex-level and block-level, but a block box in flow layout is only block-level.

  I think this would only require editing the text in CSS Flexbox and CSS Grid which says that flex items and grid items are not block-level.

• Define a new term called "blocklike-level", "normal-level", "auto-level" or similar which is defined as such:

  • Inside flow layout, a synonym for "block-level".
  • Inside flex layout, a synonym for "flex-level".
  • Inside grid layout, a synonym for "grid-level".

  And then update the specs to use that term instead of "block-level" when necessary. I prefer this option, but it's more work.

In both cases it would be a good idea to define all the possible box levels in CSS Display.