Andrew McCreight [:mccr8] Reporter
	Description • 10 years ago

Addons shouldn't be able to cause ghost windows any more, but apparently CanvasBlocker does (bug 1065461 comment 10).  We should figure out how that is possible, and how we could stop it.

	Kris Maglione [:kmag]
	Comment 1 • 10 years ago

Add-ons should still be able to create ghost windows if they store them as references on XPCOM objects, but the CanvasBlocker add-on doesn't use any non-SDK interfaces, so I don't know what's going on there.

	Andrew McCreight [:mccr8] Reporter
	Comment 2 • 9 years ago

Paul, I'm sorry I never followed up on this, but I'm looking into some issues now with ghost windows caused by addons. Are you still seeing this issue with CanvasBlocker? I wasn't able to reproduce the problem myself, so if you still see it and can give me some steps to cause the leak I'd appreciate it.

	Paul
	Comment 3 • 9 years ago

Yes, the issue still exists in Firefox 38 under Linux. Steps to reproduce:

1. Install CanvasBlocker from https://addons.mozilla.org/en-US/firefox/addon/canvasblocker/
2. Visit a page that uses the canvas, e.g. http://www.kevs3d.co.uk/dev/plasma/, let it load, and close it
3. Verify in about:memory that there are ghost windows, and that the are not garbage collected
4. Modify the CanvasBlocker block mode in about:addons to another type (probably doesn't matter which one); this should reset CanvasBlocker and clear the ghost windows
5. Verify in about:memory that the ghost windows are gone

	Kris Maglione [:kmag]
	Comment 4 • 9 years ago

I can't reproduce this in Firefox 38 on Linux.

Can you attach the contents of about:support and a dump from about:memory (Measure and Save)?

Thanks.

	Paul
	Comment 5 • 9 years ago

about:memory, as requested by kmag.

	Paul
	Comment 6 • 9 years ago

about:memory attached.

I'd rather not upload the entire about:support output; is there anything specific you're after?

	Kris Maglione [:kmag]
	Comment 7 • 9 years ago

It's all important, with the possible exception of the Graphics section. If there's anything you'd rather not share, it might be best to try to reproduce with a fresh profile. Or, feel free to email it to me if you'd just rather it not be public.

	Kris Maglione [:kmag]
	Comment 8 • 9 years ago

Also, it would really help to have a non-anonymized about:memory dump in this instance. There shouldn't be any URLs in yours other than the leaked document and some add-on URLs, both of which would be useful to see.

	Paul
	Comment 9 • 9 years ago

I can't reproduce the issue using a fresh profile, so it may be caused by an interaction between add-ons. I've emailed you the full memory and support output.

You might be surprised to learn that immediately after application startup, the memory-report.json contains several hundred URLs, mostly of favicons and app tabs. I use Firefox heavily, on a slow machine, which is why I hit all these bugs.

	Andrew McCreight [:mccr8] Reporter
	Comment 10 • 8 years ago

The steps in comment 3 don't reproduce the leak for me any more.