autoplay rule [x0paj4] failed examples don't autoplay in major browsers

[carlosapaduarte]

https://github.com/act-rules/act-rules.github.io/pull/1655#discussion_r1098674794 raises the issue about the failed example not working in Chromium browsers. A quick test reveals that the same happens in Firefox and Safari.

The way I see it, we have two choices:

• Deprecate the rule, since browsers have addressed the accessibility issue caught by this rule
• Change the applicability as suggested by @WilcoFiers in https://github.com/act-rules/act-rules.github.io/pull/1655#discussion_r1098674794, i.e., make it applicable to media elements that get turned on by scripts within 3 seconds of the page loading

[Jym77]

While building the Alfa semi-automated implementation, I had mixed result with that… Sometimes the media did autoplay (often when opening the example from the rule page), sometimes it didn't (often when entering the URL directly). I was also going to open such an issue, but more attempts show that stuff did autoplay sometimes 😖 And I'm not sure when exactly (this may also depend on devtools being open or not, on headset being connected or not, … 🙃 ) Tried both with Chrome and Firefox (on Windows 10).

[carlosapaduarte]

I'll check support for audio autoplay and for scripted auto-play and report back here

[carlosapaduarte]

I've run the tests. Results are the same for audio and video elements with audio content.

Autoplay

• Firefox and Safari do not autoplay media content unless the user has instructed the browser to do so
• Chrome tries to learn the user behaviour and acts accordingly (which might explain why it sometimes autoplayed for @Jym77). Chrome computes a Media Engagement Index to measure a user's "propensity to consume media on a site", and decides based on that to autoplay. I searched for this when, all of sudden, the examples that did not autoplay, started to autoplay after I manually played them.

Scripted autoplay

• Chrome, Firefox and Safari all block it unless the user has instructed the browser to authorise it
• This happens if there is an attempt to play the media before the user has interacted with the webpage, irrespective of the script running on load or after a timeout

[Jym77]

MDN usage note on play():

Although the term "autoplay" is usually thought of as referring to pages that immediately begin playing media upon being loaded, web browsers' autoplay policies also apply to any script-initiated playback of media, including calls to play(). (…) Note: The play() method may cause the user to be asked to grant permission to play the media, resulting in a possible delay before the returned promise is resolved. Be sure your code doesn't expect an immediate response.

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And the MDN Autoplay guide states:

As a general rule, you can assume that media will be allowed to autoplay only if at least one of the following is true:

• The audio is muted or its volume is set to 0
• The user has interacted with the site (by clicking, tapping, pressing keys, etc.)
• If the site has been allowlisted; this may happen either automatically if the browser determines that the user engages with media frequently, or manually through preferences or other user interface features
• If the autoplay Permissions Policy is used to grant autoplay support to an