[csswg-drafts] [CSS2] define and use a term for things that create a stacking context

dbaron has just created a new issue for https://github.com/w3c/csswg-drafts:

== [CSS2] define and use a term for things that create a stacking context ==
This is a subtask of #2717 covering only the edits to CSS2, and not the edits that will be needed to other specs to depend on the edits to CSS2.

Per [working group discussion today](https://github.com/w3c/csswg-drafts/issues/2717#issuecomment-420709643), we want to add a term to CSS2 for things that create a stacking context.  We then want to rewrite relevant parts of the spec (for example, some but probably not all of the references to "positioned descendants" in [Appendix E](https://drafts.csswg.org/css2/zindex.html)) to use this term, so that when other CSS specs add to the term, they will be referenced appropriately.

Some of these edits require some care.  For example, bullet point 8 of Appendix E currently begins:

> All positioned descendants with 'z-index: auto' or 'z-index: 0'

and this is interesting because:

* of these conditions, having `z-index: 0` (when `z-index` applies, i.e., when positioned) establishes a stacking context but `z-index: auto` does not
* `z-index` only applies to things that are actually positioned, and not to the other things that establish a stacking context
* everything else that establishes a stacking context should be considered here, *unless* it's also positioned and has a `z-index` other than `auto` or `0` which moves it to bullet point 3 or 9.

so the revised wording needs to account for all of this.

I suspect an appropriate place for the definition may be in [9. Layered presentation](https://drafts.csswg.org/css2/visuren.html#layers) (maybe or maybe not in the existing 9.9.1 subsection).  I suspect that section will also require edits.  Some other sections may as well.

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/3102 using your GitHub account

Received on Wednesday, 12 September 2018 22:00:39 UTC