Feature: :host, ::slotted(), ::part()

[Westbrook]

:host, ::slotted(), and ::part() are integral to develop/consuming/understanding styling for elements with Shadow Root. They also have a lot of opportunity to be leveled up with recent advances like :has() and @container. Understanding the current state of their usage and any specific issues that CSS developers might be facing with them would be amazingly beneficial in outlining paths forward with them.

[LeaVerou]

Great idea!

I think ::part() should be separate than :host and ::slotted() as they are used by different types of developers: the former by web component consumers, and the latter by web component authors, so they are likely to have vastly different exposure stats.

[Westbrook]

Likely, possibly, hopefully, there's so many known unknowns here, great call!

[SachaG]

I ended up deciding to have them all in the same question, in the interest of keeping the survey length manageable.

[LeaVerou]

Last moment thing: if we can only have one question about this, let's just keep ::part() and drop the others. Now that they're together, it's hard to gauge how many developers are aware of ::part(), and it's far more useful to know whether developers use that / know about that than the other ones that are only used in component implementation. If we have a question about ::part() we can add the other next year, but if we have them together, we can never separate them without losing historical comparison.