Re: [css3-transitions] transition-property with no supported properties

On Mar 17, 2014, at 10:00 AM, Daniel Tan <lists@novalistic.com> wrote:

> According to the specification for ‘transition-property’:
> 
>> If one of the identifiers listed is not a recognized property name or
>> is not an animatable property, the implementation must still start
>> transitions on the animatable properties in the list using the
>> duration, delay, and timing function at their respective indices in
>> the lists for ‘transition-duration’, ‘transition-delay’, and
>> ‘transition-timing-function’. In other words, unrecognized or
>> non-animatable properties must be kept in the list to preserve the
>> matching of indices.
> 
> This means that the following rule:
> 
>    transition-property: unknown, color;
>    transition-duration: 1s, 2s;
>    transition-timing-function: linear, ease-in-out;
> 
> Is treated as though only the ‘color 2s ease-in-out’ transition applies (in browsers that know how to transition color, of course).

Yes.

> 
> The spec does not seem to account for when none of the properties listed in ‘transition-property’ are animatable, such as in any of these declarations:
> 
>    transition-property: background-image;
>    transition-property: unknown;
>    transition-property: unknown, another-unknown;
> 
> Are we to assume that these would be functionally equivalent to ‘transition-property: none’? Or is there a special case to be made that hasn't been specified?

Yes, it doesn’t explicitly account for this case; in particular, the computed value is not ‘none’ but the result is the same. May instead of ‘If one the identifiers listed is not a recognized property…’, we should say ‘If any of….’ 

> 
> I ask this because, in researching the answer to the following Stack Overflow question:
> 
> http://stackoverflow.com/questions/22457222/ie10-11-uses-transform-webkit-transform
> 
> I found that with the following declaration:
> 
>    transition: -webkit-transform 1s, transform 1s;
> 
> Firefox and IE10+ apply the transition defined for the ‘transform’ property and safely ignore the one for ‘-webkit-transform’, as required by the spec. I would expect Chrome to similarly transition ‘-webkit-transform’ and ignore ‘transform’, however it seems to drop the declaration entirely. I suppose I will have to find out if this has been reported yet, since it looks clearly like a violation of the spec.
> 
> Note that Chrome is able to handle the transition just fine if I specify a property that, while not animatable, is at least recognized:
> 
>    transition: -webkit-transform 1s, background-image 1s;
> 
> Given that prefixes still see prevalent use today, this may also be a cause for concern when listing several declarations for various prefixes of ‘transition’ and/or other properties, as cascade resolution may lead to unexpected behavior as demonstrated in the question I link to.
> 
> If the behavior is intentional (i.e. having no animatable properties being equivalent to specifying ‘none’ rather than being flat-out invalid), it might be worth clarifying anyway, as it does not seem too clear to me at the moment.

Is the spec unclear, or are you less sure due to Chrome’s behavior? Given your two examples, the latter definitely seems buggy.

> 
> -- 
> Daniel Tan
> NOVALISTIC
> <http://NOVALISTIC.com>
>

Received on Monday, 17 March 2014 17:50:40 UTC