[web-animations-1] Should a property be not animatable by default?

[cdoublev]

I created a few PRs to add Animation Type to property definitions that were missing this field, because Web Animations 1 says:

Unless otherwise specified, all CSS properties are animatable.

There might be some reason for this choice but if not, I think it would be easier to define properties as not animatable unless otherwise specified, eg. when they are not defined with Animation Type.

[birtles]

Good question.

I don't recall, but I suspect this came about because when CSS transitions etc. were introduced, we didn't want to have to edit all the specs in order to mark all the properties as animatable. Rather, we just defined, e.g. how to animate a <length> and if the property took a <length> it would animate using that definition unless it explicitly opted out of it.

If we're now at the point where all the specs have Animatable type specified, then we could switch that definition to default to not animatable as suggested.

Personally, I think the cases where we don't want a property to be animatable are very few (e.g. animation-* properties and possibly display) such that they are very much the exception and require justification for why they are not animatable so keeping animatable as the default makes sense to me in that regard.

[cdoublev]

You are right. There are very few non animatable properties and the risk of a spec author introducing one because Animation type: not animatable would not be defined, is very low.

I suggested to add Animation type: not animatable to properties from CSS Spatial Navigation and CSS Speech, but actually I am not sure all properties from CSS Speech should be not animatable, eg. voice-volume, voice-balance, voice-rate, etc.

[birtles]

Thanks for following up here.

I suggested to add Animation type: not animatable to properties from CSS Spatial Navigation and CSS Speech, but actually I am not sure all properties from CSS Speech should be not animatable, eg. voice-volume, voice-balance, voice-rate, etc.

Generally we should make all properties, even if it is only discrete animation, unless there's a reason not to (e.g. creating cyclic dependencies with the animation parameters). Without knowing the CSS Speech spec, my initial assumption is that all the voice-* properties should be animatable.

[cdoublev]

I assume you meant we should make all properties animatable.

Yeah, I realized this while reviewing all non animatable properties or missing Animation type.

Among non-animatable properties, background-blend-mode and mix-blend-mode are the only non animatable properties I wonder why their animation type cannot be discrete, therefore I created this issue.

Among properties missing Animation type, only those from CSS Spatial Navigation and other properties than voice-* from CSS Speech, should be non animatable, imo.

[birtles]

I assume you meant we should make all properties animatable.

Yes, sorry!

Yeah, I realized this while reviewing all non animatable properties or missing Animation type.

Among non-animatable properties, background-blend-mode and mix-blend-mode are the only non animatable properties I wonder why their animation type cannot be discrete, therefore I created this issue.

Among properties missing Animation type, only those from CSS Spatial Navigation and other properties than voice-* from CSS Speech, should be non animatable, imo.

Thanks, that sounds great.