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Re: :stuck psuedo class WAS: specifying position:sticky

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Tue, 27 Aug 2013 22:19:53 -0700
Message-ID: <CAAWBYDAX-OXo6UGB6F7-k75pGNDgL3_QsBDCS9eu4nLiRXFGCQ@mail.gmail.com>
To: Brian Kardell <bkardell@gmail.com>
Cc: Ojan Vafai <ojan@chromium.org>, Corey Ford <cford@mozilla.com>, "www-style@w3.org" <www-style@w3.org>, "L. David Baron" <dbaron@dbaron.org>
On Tue, Aug 27, 2013 at 7:10 PM, Brian Kardell <bkardell@gmail.com> wrote:
> On Tue, Aug 27, 2013 at 9:27 PM, Tab Atkins Jr. <jackalmage@gmail.com>
> wrote:
>> On Tue, Aug 27, 2013 at 5:34 PM, Ojan Vafai <ojan@chromium.org> wrote:
>> > This may be too early, but I think we should add a pseudo-class for
>> > position:sticky's that are stuck to an edge. This lets you easily style
>> > the
>> > stuck element (e.g. with a box-shadow).
>> Immediately bringing up the obvious question of what ":stuck {
>> position: static; }" does.
>> I think we can't avoid this problem forever, and that the right
>> solution is to define a set of "selector-affecting properties" and
>> "property-affected selectors", and say that you can't set any of the
>> former in a style rule whose selector contains one of the latter.
>> (That is, you can't *just* say "you can't set position inside a :stuck
>> rule", because as soon as another property/selector (foo-prop and
>> :foo), you can just set 'foo-prop' inside of :stuck and then set
>> 'position' inside of :foo and run into circularity again.  You have to
>> treat the whole set of properties as infectious to the whole set of
>> selectors.)
> Wow - I think my mind just exploded.  Can you (or anyone who understands)
> try explaining that again with some slightly more intuitively named
> fictitious prop/selectors so I can try wrapping my head around what you are
> saying in that last paragraph? or explain the relationship you are
> explaining another way that leads to circularity?  It seems like you are
> saying that if we had a simple "setting the following properties in a :stuck
> rule has no effect..." that is some other way to hit circularity because of
> another (new) situation like it?  Is it only in the case where the
> properties overlap between two of them or something?  Perhaps I am being
> dense, but my mind is spinning.

Okay, better example. ^_^  Assume that my Toggle States suggestion
also exists: <http://tabatkins.github.io/specs/css-toggle-states/Overview.html#checked-problems>

You could then write code like:

.foo { position: sticky; }
.foo:stuck {
  toggle-states: 2;
  toggle-initial: 1;
  /* makes it match :checked */
.foo:checked {
  position: static;
  /* makes it not match :stuck */

If you get stuck, you match :checked. If you're checked, you're
unstuck.  Circles!

Instead, 'position' and the 'toggle-*' properties are both defined as
"selector-affecting properties", and :stuck and :checked are
"property-affected selectors", so you can't use any of those
properties in blocks with either of those selectors.

Received on Wednesday, 28 August 2013 05:20:40 UTC

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