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Re: [csswg-drafts] [scroll-animations] Support progress-based animations on finite timelines (#4862)

From: Robert Flack via GitHub <sysbot+gh@w3.org>
Date: Wed, 10 Jun 2020 03:22:58 +0000
To: public-css-archive@w3.org
Message-ID: <issue_comment.created-641696579-1591759377-sysbot+gh@w3.org>
I've updated the pull request to clarify the key points from our discussion. In particular
* The duration of ScrollTimeline is 100%
* start and end delay on an animation with a percentage based iteration duration (i.e. `duration: auto` on a ScrollTimeline) resolves to 0. This is because we have no time to resolve them against. In the future, we could support percentages here.
* a non-auto iteration duration on a percentage based timeline resolves to 0. In the future we could define magical animation scaling to fit the timeline's duration range.
* The auto iteration duration resolves to 100% / iteration count.
* The time values internally for percentage based animations go from 0 to 1.

I believe this allows developers to use auto duration for now (in fact requires it for scroll timeline since anything else results in a 0 duration animation), and should not conflict with future specifications of how percentage based durations could work as auto is implementing the "filling" behavior that makes sense for unspecified values.

We may want to specify automatic filling behavior if the animation's iteration duration is not auto so that switching a time-based animation to a scroll timeline does the "right thing", let me know.

-- 
GitHub Notification of comment by flackr
Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/4862#issuecomment-641696579 using your GitHub account
Received on Wednesday, 10 June 2020 03:22:59 UTC

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