[css-transitions][all-the-specs] Editing 'Animatable' to 'Animation type'


Back at TPAC last year I took an action to update all the specs to 
change their "Animatable" line to read "Animation type".[1][2]

Part of the background to this is that CSS Transitions says that all 
properties that are currently marked as "Animatable: no" should actually 
do a discrete switch from the 'from' value to the 'to' value 50% of the 
way through the timing function.

That behavior has been implemented in Chrome for CSS *Animations* and 
has been implemented for some (quite random subset of) properties in 
Firefox, again for CSS *Animations*. We don't know yet if doing the same 
thing will be web-compatible for CSS *Transitions* (personally, I'm 

However, not all properties should do the 50% switch. For example, 
'animation-*' properties, 'transition-*' properties, and the 'display' 
property should simply not be animatable at all.

I would like to go ahead and update all the last ED of all the concerned 
CSS specs to change lines like:

   Animatable: no

to, one of the following

   Animation type: discrete
   Animation type: none

Also, for consistency, I will change lines like "Animatable: yes, as 
length" to "Animation type: length".

I expect I'll make 'length' here link to 
https://drafts.csswg.org/css-transitions/#animtype-length although 
long-term I should probably make rework the Web Animations animation 
types and point it there since that includes (or will include) 
additional definitions such as how addition works for each type. 
Obviously newer specs can define their own animation types inline 
without referring to Web Animations as indeed some have already started 
to do.

I expect I'll set up the changes as a PR on each spec so that editors 
have a chance to give feedback.

If it turns out the 50% switch is not web-compatible for CSS 
transitions, we can just give 'discrete' a special meaning when used 
with transitions. CSS Animations and Web Animations can continue to use 
the 50% switch meaning.

Please let me know if you have any concerns.

Best regards,


PS- We've been doing some fairly thorough analysis of how these 
properties are interpolated in different modes in different browsers at 
[3][4] for those interested.

[1] https://lists.w3.org/Archives/Public/www-style/2015Nov/0308.html, item 8
[2] https://github.com/w3c/csswg-drafts/issues/72
[3] https://dadaa.github.io/IsAnimatableCSS/

Received on Monday, 16 May 2016 05:46:30 UTC