[whatwg] readonly attribute

[Domenic Denicola]

Hi Jonathan, sorry for the delay in responding here.

> This doesn't quite jive with my understanding of the distinction between
> `readonly` and `disabled` - to me, "readonly" and "disabled" controls can both
> not be edited by the user, but "readonly" means that the value will be
> included in the payload when the form is submitted, whereas "disabled"
> means that the value will not be included. It seems like this distinction does
> apply to `button`, `checkbox`, and `select` as well as for `input`.

It's true that there is also an impact on form submission. This was discussed somewhat recently in https://github.com/whatwg/html/issues/2311. Perhaps the section you quoted should be updated to also point this out, and discuss the tradeoffs we go through in that thread.

> One other related question - it seems like select inputs are always matched
> by the `:read-only` selector in CSS, but the `readOnly` property in Javascript is
> always `undefined` - the inconsistency there makes me think that something
> is not right...  https://jsfiddle.net/jrz/yt1c3ee7/

Yeah, unfortunately :read-only in CSS is only vaguely connected to the readonly="" attribute. It's more about "is it not possible to edit this?" You can find its full definition at https://html.spec.whatwg.org/multipage/semantics-other.html#selector-read-only. As you can see the reason <select> is :read-only is because it isn't considered an "editable" form control for these purposes---just like <div>. Note that divEl.readOnly is also undefined, so this is basically consistent.