Intent to prototype and ship: :user-valid and :user-invalid pseudo-classes.

[Emilio Cobos Álvarez]

Hi,

In bug 1694141 I plan to unprefix :-moz-ui-valid and :-moz-ui-invalid
pseudo-classes. These are useful pseudo-classes to determine when to
show feedback to the user about a form control being invalid.

Standard: https://drafts.csswg.org/selectors/#user-pseudos

Platform coverage: all

Preference: None

Devtools bug: N/A

Other browsers: No signal from other vendors, though we've shipped this
functionality for quite a while and the CSS working group considers it
useful, see discussions:

* https://lists.w3.org/Archives/Public/www-style/2012Aug/0749.html
* https://lists.w3.org/Archives/Public/www-style/2015Sep/0111.html

I'm hoping that unprefixing it in Gecko will serve as a bit of a nag to
other browsers.

Chromium bug: https://bugs.chromium.org/p/chromium/issues/detail?id=1156069

WebKit bug: https://bugs.webkit.org/show_bug.cgi?id=222267

web-platform-tests: There's a test for :user-invalid in css/selectors. I
plan to add a test for :user-valid. There's
https://github.com/web-platform-tests/wpt/issues/9346 on file for adding
WPTs that test the user-interaction part of this.

Let me know if you have any objections about this change, but I think
having a prefixed pseudo-class for this is not a great state of affairs.

-- Emilio

[Anne van Kesteren]

On Mon, Feb 22, 2021 at 2:59 PM Emilio Cobos Álvarez <emi...@mozilla.com> wrote:
> Let me know if you have any objections about this change, but I think
> having a prefixed pseudo-class for this is not a great state of affairs.

This seems reasonable, but I think we should define the processing
model for them in the HTML Standard as well, to ensure everyone can
align on when exactly these are supposed to match.

[Xidorn Quan]

On Tue, Feb 23, 2021, at 12:59 AM, Emilio Cobos Álvarez wrote:
> Standard: https://drafts.csswg.org/selectors/#user-pseudos

>
> Other browsers: No signal from other vendors, though we've shipped this
> functionality for quite a while and the CSS working group considers it
> useful, see discussions:
>
> * https://lists.w3.org/Archives/Public/www-style/2012Aug/0749.html
> * https://lists.w3.org/Archives/Public/www-style/2015Sep/0111.html
>
> I'm hoping that unprefixing it in Gecko will serve as a bit of a nag to
> other browsers.

Please head up in CSS working group about this, and probably ask for a resolution on no objection for us to ship it, as this spec is still in draft.

- Xidorn

[Emilio Cobos Álvarez]

On 2/23/21 11:52, Xidorn Quan wrote:
> Please head up in CSS working group about this, and probably ask for a resolution on no objection for us to ship it, as this spec is still in draft.

Hmm, is it? https://www.w3.org/TR/selectors-4/#user-pseudos has had
:user-invalid for quite a while, and we and other engines ship a lot of
stuff in selectors-4.

(I just added spec text for :user-valid, but it was noted in the
non-draft spec that there was a resolution to add it as well).

Anyhow not particularly trying to avoid this, just trying to clarify the
situation. A heads-up probably wouldn't hurt anyways, and per Anne's
comments we might want some html spec text as well.

-- Emilio

[Emilio Cobos Álvarez]

The original spec text for :user-invalid was pretty flexible in terms of
when it can match. My understanding is that that was kind of intentional
(cc'ing fantasai who was part of those discussions).

But yeah I tend to agree we probably want to define more precisely when
these must match and maybe even when they may match.

-- Emilio

[Anne van Kesteren]

On Tue, Feb 23, 2021 at 9:49 PM fantasai <fantasa...@inkedblade.net> wrote:
> We wanted it to be flexible enough that UAs could experiment with behavior and
> improve usability over time, so we locked down the one period in time that we
> felt was not up for debate (between attempted submission and next interaction
> with the invalid input) and left the rest open to interpretation.

I played with this some more and I think that might be a tad too
vague. E.g., if you cancel an invalid event Firefox will no longer
show UI messages to the user about filling in a form control, but
:-moz-ui-invalid still matches (see
https://software.hixie.ch/utilities/js/live-dom-viewer/saved/8957 for
a demo). And flexibility here is tough as web developers likely want
these to be fully deterministic to be able to build consistent
experiences.