[css-display][css-pseudo] Clearly define display: contents behaviour on pseudo-elements (original) (raw)

https://drafts.csswg.org/css-display/#box-generation

https://drafts.csswg.org/css-pseudo/

While working on display: contents handling for ::backdrop (which has clearly defined rules), I noticed it is not well defined for pseudo elements in general, and behaviour is inconsistent across different browsers (notably for ::marker or ::file-selector-button). Should we try and make some easy to understand rules?

It would be convenient if those rules were based on spec concepts, e.g. "tree-abiding pseudo-elements", "Typographic Pseudo-elements". "highlight pseudo-elements".