Re: [css-will-change] 'will-change' and custom properties

On Fri, Dec 4, 2015 at 3:07 PM, L. David Baron <dbaron@dbaron.org> wrote:
> On Friday 2015-12-04 14:20 -0800, Tab Atkins Jr. wrote:
>> On Tue, Nov 24, 2015 at 3:44 PM, L. David Baron <dbaron@dbaron.org> wrote:
>> > https://drafts.csswg.org/css-will-change/#valdef-will-change-custom-ident
>> > defines the behavior of 'will-change: <custom-ident>'.  It has a
>> > number of statements that "If a[ny] non-initial value of a property
>> > would cause"...
>> >
>> > Xidorn pointed out to me in
>> > https://bugzilla.mozilla.org/show_bug.cgi?id=1227501 that
>> > technically this applies to custom properties, but it probably isn't
>> > meant to.  I don't think implementations should be required to trace
>> > through the uses of a custom property to see if the custom property
>> > could possibly cause the creation of a stacking context or the
>> > generation of a containing block for fixed-positioned elements.
>> > That seems like a lot of work for very little benefit... and
>> > will-change is intended to make things faster, not slower!
>> >
>> > I think this definition should explictly exclude custom properties
>> > from having these effects.
>>
>> Agreed, it's not intended that that line apply to such extreme "action
>> at a distance" effects.
>>
>> I've specced that custom property names must have no effect, including
>> the side-effect things.  That work?
>
> That works, although I think it could be clearer, since
> ""side-effect" management" isn't really defined.  Perhaps replace:
>
>   Specifying a custom property must have no effect, including the
>   "side-effect" management detailed below.
>
> with something more like:
>
>   Specifying a custom property must have no effect, which means that
>   effects that happen through custom properties do not count for the
>   rules below that are conditioned on any non-initial value of a
>   property causing something.
>
> (It also might help to change the fourth such rule (for "rendering
> differences") to use "If any" (like the other three rules) instead
> of "If a".)

Sure, both sound good. Done.

~TJ

Received on Saturday, 5 December 2015 00:07:38 UTC