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APIOptions.md

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API Option A: run-loop is built into the browser

The run-loop could be built into the browser and integrated closely with the browser’s event-loop. This would automatically move #4 into the browser and #3 becomes the platform exposed API. The API sketch follows.

API for posting & canceling tasks

NOTE: syntax is likely to change for compatibility for posting work off main thread variant (TODO: Link to repo).

function mytask() {
  ...
}

myQueue = TaskQueue.default("user-blocking")

returns the global task queue with priority “user-blocking”, for posting to main thread.

taskId = myQueue.postTask(myTask, <list of args>);

where myTask is a callback. The return value is a long integer, the task id, that uniquely identifies the entry in the queue.

myQueue.cancelTask(taskId);

taskId can be used to later cancel the task.

NOTE: The return type could be a promise instead of ID, for convenience and chaining of tasks. If so, then AbortController is a standard way to cancel pending promises.

API Option B: run-loop is built in a JS library

The run-loop could be built into a JS scheduling library. This would mean that #3 is defined in JS and not a platform primitive. The platform exposed API is essentially focused on exposing what's needed for the run-loop:

  • 4a. can be addressed with shouldYield proposal.
  • 4b. is really difficult to reason about and expose to JS.

The platform exposed API would also fill in the gaps for how to post work at specific priorities:

  • Posting work at default priority: var handle = window.requestDefaultCallback(callback[, options])

TODO: API Sketch / sample code for JS scheduler. Eg. React Scheduler, Maps Scheduler

Pros & Cons:API Option A vs B

API Option A: Cons

  • Really difficult to reason about and expose all necessary signals in #4, especially 4b.
  • Not possible to expose priorities

A key thing here is understanding what subset of 4b. is necessary for effective scheduling and what it might take to support that.

API Option B: Cons

  • potentially tougher interop story?