1961816 - Microtasks posted from a direct macOS event don't run until an arbitrary checkpoint inside a gecko event.

Status: RESOLVED FIXED

(Core :: XPCOM, defect)

Description

[Emilio Cobos Álvarez (:emilio)]

This is the root cause of bug 1960926. The TLDR is:

• The macOS event set-up doesn't use Gecko events.
• That gets us to run random JS (mouseup events and so on) with a RecursionDepth() of zero.
• That makes microtask checkpoints not run here (because 0 >= 0).
• That causes the microtasks to run basically on whatever arbitrary microtask checkpoint happens inside a Gecko task, which in bug 1960926 was the nsRefreshDriver animation checkpoint.

I think the code in RunMicrotaskCheckpoints should be more robust, but ideally we also fix that the event nesting level issue.

Comment 1

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1961816 - Use saner event nesting set-up on macOS. r=smaug

Account for native event loop nesting level.

Comment 2

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1961816 - Run microtask checkpoints on direct widget events correctly. r=smaug!

Comment 3

[Sarah Clements [:sclements]]

Emilio, thanks for working on the regression in bug 1961816 - should this have tracking to get this fix into 139 along with bug 1960926?

Comment 4

[Emilio Cobos Álvarez (:emilio)]

No, this should land after the freeze, it's a bit riskier change.

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/152a0c0ed6c4
Run microtask checkpoints on direct widget events correctly. r=smaug

Comment 6

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/152a0c0ed6c4