[selectors] Add :role() pseudo-class

TabAtkins: jcraig suggested a :role pseudo
hober: There's a few problems. One is the impl RA roles on the
elements. When you have multiple roles on one element, you
get all of them.
hober: For styling you may want to style that as a switch or a
checkbox. Right now that's difficult in CSS.
hober: There's also the case of wanting to simply style all the
buttons on the page.
hober: You want to be able to say :role(button) and be done.
TabAtkins: That's convincing. Is there anything outside that?

hober: We can always add more.
glazou: You mentioned implied role. So some won't need an assigned

role. We'll need to refer to HTML.

hober: In CSS we say the host language has that.
dbaron: It's :: or : ?

TabAtkins: It's a functional class. It should be an ident.

glazou: Can you have multiple roles?

hober: Syntactically you can,

hober: But only one is active.

glazou: So if you have multiple roles on one element, it's

whitespace broken?

dino: So if you do :role...

hober: You can do role=button and role="super button". Or we

separate in the list itself.

glazou: So the role attr is multiple but the :role() pseudo is only

one?

hober: Yeah.
dauwhe: dpub is working on adding things for role attr.

TabAtkins: Do you know if it will be consistent with this?

dauwhe: They haven't said. I'll raise that with them.
TabAtkins: So I guess that's simple. Objections to adding :role()

to selectors?

TabAtkins: So :role(button) would target anything that has a

button according to aria rules.

hober: It wouldn't match button role = checkbox or something crazy
dbaron: So people are okay with agreeing CSS won't do future

things to influence what the aria role is.

hober: It should be defined by pointing over there [to markup layer].

fantasai: We need to have another language that has CSS syntax for

that kind of stuff. Our stuff should be about styling.

fantasai: People keep asking us to put things in CSS that belong

in the DOM, because they want to use CSS selectors and

cascading to attach it to the tree.

TabAtkins: If someone would like to implement cascading attr

selectors in a browser shrug

dbaron: Having CSS do this side makes sense, but we can't do both.

hober: Should we have a note in the spec saying "you may be

confused"?

glazou: When we had selectors we didn't have a note. I'm not sure

we need a note.

hober: Okay.
glazou: So no objections?
RESOLVED: add :role() to selectors
glazou: Who is going to write the prose?

TabAtkins: I will.