[csswg-drafts] [css-mediaqueries] Should prefers-reduced-motion apply to behaviours built into the browser? (#6403)

theres-waldo has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-mediaqueries] Should prefers-reduced-motion apply to behaviours built into the browser? ==
The CSS Media Queries spec says the [following](https://drafts.csswg.org/mediaqueries-5/#descdef-media-prefers-reduced-motion) about `prefers-reduced-motion`:

> The `prefers-reduced-motion` media feature is used to detect if the user has requested the system minimize the amount of animation or motion it uses.

(The [MDN page](https://developer.mozilla.org/en-US/docs/Web/CSS/@media/prefers-reduced-motion) uses slightly different wording, "minimize the amount of **non-essential** motion it uses". I believe this issue is relevant with either wording.)

I understand this is primarily a mechanism for **web developers** to choose to do something differently (e.g. disable certain animations or substitute them for lower-motion animations) based on the value of `prefers-reduced-motion`.

However, I'm wondering if this setting should also affect **behaviours built into the browser**.

A particular example where this came up is the "rubber-banding" overscroll effect that some browsers show on MacOS (and sometimes other platforms) when a scroll container reaches the end of its scroll range.

In Firefox, we recently implemented this effect (starting in Firefox 89), and we received a [bug report](https://bugzilla.mozilla.org/show_bug.cgi?id=1705927) requesting that the effect be turned off when `prefers-reduced-motion` is specified. I did so, because it seems to me that the overscroll effect is a good example of "non-essential" / avoidable motion, and therefore disabling it is in keeping with the spirit of this setting.

However, we then received [another bug report](https://bugzilla.mozilla.org/show_bug.cgi?id=1714143#c10) pointing out that the setting does not disable the overscroll effect in either Chrome or Safari, and Firefox's behaviour is therefore inconsistent with other browsers.

I would appreciate some guidance on:

  * Should browsers try to honour this setting in their built-in behaviours (such as the mentioned overscroll effect, and other animations that are in the browser's control, e.g. animations in the browser UI)?
  * If so, is there anything about a rubber-banding overscroll effect in particular that would **exempt** it from being disabled even if `prefers-reduced-motion` is specified?

Thanks!

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/6403 using your GitHub account


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Received on Monday, 21 June 2021 21:59:28 UTC