implementation detail: enableScheduling uses MessageChannel API?
I can put in the work to polyfill it, but why is it needed to begin with? does the scheduler do any wacky iframe/webworker stuff under the hood?
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another web-specific API:
I'll just drop in an undefined variable here
MessageChannel has a very specific timing (on its event) that the scheduler needs.
where are you running this, may I ask?Proprietary embedded context! It's not react native, but the broad strokes are super similar
so any web-specific API i need to polyfill, but we don't have things like iframes to worry about
I see, yes it's a bit tricky on the scheduler's side
ok notes for future spelunkers. MessageChannel is used in the body of this function and nowhere else:
https://github.com/solidjs/solid/blob/460068202bbd7a56a14664ac14fa7efb900d8194/packages/solid/src/reactive/scheduler.ts#L29
The solidjs tests replace it with a do-nearly-nothing polyfill that using setTimeout instead:
https://github.com/solidjs/solid/blob/460068202bbd7a56a14664ac14fa7efb900d8194/packages/solid/test/MessageChannel.ts#L1C1-L9C3
The purpose of this piece of code is to schedule work to be done at a future time. Using setTimeout means it'll happen in the next frame's update loop, I don't know exactly what MessageChannel does but it's probably something similar. queueMicrotask() would be a bad idea, it'd just do everything in a single frame, and requestIdleCallback() would probably result in a very laggy experience.
The scheduler uses 'navigator.scheduling.isInputPending' to detect if it should yield to existing user input:
https://developer.mozilla.org/en-US/docs/Web/API/Scheduling/isInputPending
https://github.com/solidjs/solid/blob/460068202bbd7a56a14664ac14fa7efb900d8194/packages/solid/src/reactive/scheduler.ts#L68
if it doesn't detect any user input, it will attempt to run for as long as possible, up to the maxYieldInterval (300ms).
If you don't implement isInputPending, it will assume that there's always input pending and yield after the the yieldInterval, 5ms.
All of this is user-customizable by providing a custom implementation of
requestCallback to enableScheduling.