Re: [web-animations] distance computation issue

On 2014/12/11 19:18, Aleksei Semenov wrote:
> Hi, everyone.
>
> Please, consider the following example:
>        var keyframes = [
>            {top: '10%'},
>            {top: '20%'},
>            {top: '50%'}
>        ];
>        var effect = new KeyframeEffect(keyframes, 'paced(top)');
>        effect.getFrames(); // value of computedOffset in returned frames?
>
> To calculate computedOffset spacing keyframes procedure needs to calculate
> distance between values of paced property. Distance computation for
> percentage values
> is specified here
> http://w3c.github.io/web-animations/#animatable-as-length-percentage-or-calc-section
>
>
>> distance computation: as with animatable as real number but using the
>> used value [CSS21] for Vstart and Vend.
>
> Used value definition http://www.w3.org/TR/CSS2/cascade.html#used-value
>
>> Computed values are processed as far as possible without formatting
>> the document.Some values, however, can only be determined when the
>> document is being laid out.For example, if the width of an element is
>> set to be a certain percentage of itscontaining block, the width
>> cannot be determined until the width of the containingblock has been
>> determined. The used value is the result of taking the computedvalue
>> and resolving any remaining dependencies into an absolute value.
>
> Since the actual element and its container are not available, the "used
> value" can not be determined here.
> So the distance and computed offset also can not be calculated.

Hi Aleksei,

Thanks for reporting this.

We discussed this last December.[1] I've now updated the spec to address 
this.[2] I hope this resolves the issue.

Best regards,

Brian

[1] https://lists.w3.org/Archives/Public/public-fx/2014OctDec/0126.html, 
item 4
[2] 
https://github.com/w3c/web-animations/commit/6b85b490a41b142b282df0c2e2f2b990cea470c3

Received on Friday, 13 February 2015 06:54:05 UTC