RE: when do transitions occur?

Thanks for the responses Tab and David. I didn't realize that shorthands don't have a computed value since getComputedStyle seems to return a valid string for shorthands.

And just for clarification regarding zero duration transitions and animations (since I seem to have trouble finding the previous discussion of it), 0 duration transitions should not throw events if the delay is also 0. If the delay is positive, 0 duration transitions should throw an event. 0 duration animations, on the other hand, should throw events. Are those statements accurate?

-----Original Message-----
From: L. David Baron [mailto:dbaron@dbaron.org] 
Sent: Wednesday, September 14, 2011 12:06 PM
To: Brian Manthos
Cc: Tab Atkins Jr.; Jennifer Yu; www-style@w3.org
Subject: Re: when do transitions occur?

On Wednesday 2011-09-14 17:48 +0000, Brian Manthos wrote:
> 1. Are there any scenarios where an event should fire for the shorthand due to transitioning?

No (in my opinion).

> 2. Or are component longhands the only events that ever fire for transitioning?

Yes.

> 3. If 2, should longhands that are unchanged in value but members of a shorthand that is explicitly transitioned be excluded from the events?

Yes.  Transitions are triggered by changes in computed value (see section 3, Starting of Transitions).  It doesn't matter whether these changes occurred because a shorthand was changed or because the individual longhand properties were changed.  Only longhand properties have computed values, and only those whose computed values changed should have events.


> Example A:
>  from background: blue;
>  to background: transparent;
> A1: background
> A2: background-color
> A3: background-image
> A4: background-* (all 8)
> A5: A2 and A3
> A6: A1, A2, and A3
> A7: A1 and A4
> A8: something else
> 
> My evaluation of each event set option:
> A1: it's the author-aligned delta
> A2: (doesn't make sense in isolation)
> A3: (doesn't make sense in isolation)
> A4: all longhands are involved in the delta, no culling of unchanged 
> properties
> A5: all longhands are involved in the delta, only include changed 
> properties
> A6: same reasons as A1 and A5, both apply
> A7: same reasons as A1 and A4, both apply
> A8: (tbd)

I think it's clearly A2, since background-color is the only property whose computed value changed.  (Also, many of the background-* properties aren't animatable at all.)

-David

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𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla Corporation               http://www.mozilla.com/   𝄂

Received on Saturday, 17 September 2011 01:06:48 UTC