[worklets] Allow long running scripts to be informed that they are being treated as unresponsive?

[asajeffrey]

In https://www.w3.org/TR/css-paint-api-1/#drawing-an-image, there is a note

Note: The user agent should consider long running paint functions similar to long running script in the main execution context. For example, they should show a "unresponsive script" dialog or similar. In addition user agents should provide tooling within their debugging tools to show authors how expensive their paint classes are.

This provides user and developer feedback in the UI, but does not inform the script that the UA is considering it to be unresponsive. Should unresponsive scripts be informed that they are unresponsive?

[asajeffrey]

This came up in the context of testing the behaviour of unresponsive scripts, but may come up in other contexts too. servo/servo#17370

[tabatkins]

I guess throw an error at window? I think that's been used for similar things.

[asajeffrey]

Or at the element which has the worklet attached to it?

[css-meeting-bot]

The Working Group just discussed Unresponsive scripts, and agreed to the following resolutions:

• RESOLVED: Punt slow-script dev notification to level 2 of worklets

The full IRC log of that discussion

<TabAtkins> Topic: Unresponsive scripts
<TabAtkins> github: https://github.com//issues/507
<TabAtkins> iank_: Curreently the spec text allows a while(true) loop, the UA can kill it whenever.
<TabAtkins> iank_: But no feedback to the dev, nothing throws.
<TabAtkins> iank_: Do we want to notify th edev?
<TabAtkins> iank_: So an error fired on the Worklet object (in the main thread), perhaps?
<TabAtkins> iank_: Or punt to l2
<TabAtkins> smfr: Specific to paint worklets?
<TabAtkins> iank_: All worklets
<TabAtkins> surma: I think at the start, dev tooling is good enough, no need to require it yet
<TabAtkins> Rossen: We can kick it down the road
<TabAtkins> iank_: That' my impression too.
<TabAtkins> dbaron: Should we tag this as for worklets spec, not paint api?
<TabAtkins> iank_: yES
<TabAtkins> RESOLVED: Punt slow-script dev notification to level 2 of worklets