fix: prevent unbounded recursion on boot

[AprilSylph]

Description

A theoretical improvement. Caps the maximum number of boot attempts at 3600, which is a very safe one minute on a 60Hz display, decreasing as refresh rate increases.

I think it's very safe to assume that devices able to output 360 frames per second can load React in a lot less than 10 seconds.

I would be very interested in revisiting #1971 after this.

Testing steps

1. Load the modified addon
2. Enable some features, ideally ones that take visible effect immediately upon activating
3. Open a Tumblr tab
   • Expected result: XKit boots normally
4. Open devtools → Network and enable throttling
5. Reload the Tumblr tab
   • Expected result: The tab is sloooooow to load
   • Expected result: When the tab finally does load, React loads normally
   • Expected result: XKit boots normally after this
     (Proving that "run_at": "document_end" is working as intended)

[marcustyphoon]

Ooh, good idea. I think the chances that this is addressing a thing which is in fact happening are low, but good safety.

[marcustyphoon]

Some alternative (non-recursive) forms (not tested, may have typos):

  const waitForReactLoaded = async () => {
    for (let attempts = 0; attempts < MAX_BOOT_ATTEMPTS; attempts++) {
      if (isReactLoaded()) return;
      await new Promise(window.requestAnimationFrame);
    }
    throw new Error('XKit Rewritten boot failed; React did not load after 10+ seconds.');
  };

  if (redpop) {
    waitForReactLoaded()
      .then(init)
      .catch(console.error);
  }

  const waitForReactLoaded = async () => {
    let attempts = 0;

    while (!isReactLoaded()) {
      if (++attempts <= MAX_BOOT_ATTEMPTS) {
        throw new Error('XKit Rewritten boot failed; React did not load after 10+ seconds.');
      }
      await new Promise(window.requestAnimationFrame);
    }
  };

  if (redpop) {
    waitForReactLoaded()
      .then(init)
      .catch(console.error);
  }

edit: we could also call await waitForReactLoaded() in init if that feels cleaner.

[marcustyphoon]

(How do I feel about this commit coauthor and its legal interaction with the gpl license? I'm officially Not Sure.)

[marcustyphoon]

Well... I can't get isReactLoaded() to ever return false in practice, so this code pah is untested. I hacked it to return false 90% of the time and it seems to work fine, so... success?

[AprilSylph]

I hacked it to return false 90% of the time and it seems to work fine, so... success?

Did the same for the latest commit; turns out you can't use window.requestAnimationFrame as a generic callback, it errors with a complaint about being called on an object that doesn't implement Window.

[marcustyphoon]

Interesting. I guess I've always used plain requestAnimationFrame. Alternatively, if that also doesn't work, I've hardcore mandala effected myself.

[marcustyphoon]

(Surely it's not a module vs script thing?)

[AprilSylph]

• Works: await new Promise((resolve) => window.requestAnimationFrame(resolve));
• Works: await new Promise(requestAnimationFrame);
• Breaks: await new Promise(window.requestAnimationFrame);