842149 - nsIdleService polls too often if an idle listener removes itself

Status: RESOLVED FIXED

(Core :: Widget, defect)

Description

[:Irving Reid (No longer working on Firefox)]

On platforms that support polling for how long the system has been idle (OS/2, GTK, Windows, Qt, OS/X), when a handler that is currently in the idle state deregisters itself from the idle service, the idle service doesn't change its "mAnyObserverIdle" flag.

This can lead to the idle service polling the OS for idle status every five seconds, to detect the idle -> user back transition, even though there is no handler waiting for that transition.

Comment 1

[:Irving Reid (No longer working on Firefox)]

Attachment: Count idle observers to handle case where an observer is removed while idle

This takes the approach of counting the number of idle observers. The alternative approach would be to scan the observer list looking for remaining observers in idle mode, when one is removed.

Comment 2

[Justin Lebar (not reading bugmail)]

Gosh, we really need to rewrite this whole file.

Comment 3

[Justin Lebar (not reading bugmail)]

>   // Find the entry and remove it, if it was the last entry, we just let the
>   // existing timer run to completion (there might be a new registration in a
>   // little while.
>   IdleListenerComparator c;
>-  if (mArrayListeners.RemoveElement(listener, c)) {
>+  nsTArray<IdleListener>::index_type element = mArrayListeners.IndexOf(listener, 0, c);

Nit: This is an index, so please don't call it |element|.

r=me, I guess.  It would take me all day to verify that this patch actually works, but it's hard to imagine how this would make things any worse...

Comment 4

[Justin Lebar (not reading bugmail)]

At the risk of stating the obvious, please keep an eye out for regressions after landing this; we don't have a great track record with modifying the idle service.

Comment 5

[:Irving Reid (No longer working on Firefox)]

Inbound with nit fixed: https://hg.mozilla.org/integration/mozilla-inbound/rev/601c2d37c2bc

Comment 6

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/601c2d37c2bc