1264549 - APZ scroll position jumps on Google+ when any dialog is opened

Status: RESOLVED DUPLICATE of bug 1257641

(Core :: Panning and Zooming, defect)

Description

[gordonrankin82]

User Agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/49.0.2623.112 Safari/537.36

Steps to reproduce:

1. Go to https://plus.google.com/
2. Scroll down 5+ pixels, but not too far, so that the "What's new with you" button/card is still visible.  but you 'must' scroll down a little to replicate this bug.
3. Click the "What's new with you" button to open the "new post" dialog and overlay.


Actual results:

The scroll position/content position judders dramatically.


Expected results:

The content should remain static.

Google is using a common technique to disable root document scrolling when it opens a dialog here.  They are taking the scroll position and applying it's negative offset to an inner "content" element and translating it upwards while also setting that content to "position:fixed".

This removes the content from the flow and the body/root element no longer scrolls.

With APZ turned on however, there is a noticeable judder when doing so.  It appears as though the main thread and the compositor are out of sync during this change.

Comment 1

[gordonrankin82]

Today's 'nightly' update seems to have fixed this. Can anyone else confirm that this bug is no longer present as I don't have any other machines to test on right now?

Comment 2

[Kartikaya Gupta (email:[e-mail])]

This sounds a lot like bug 1258045 which is also fixed in today's nightly via bug 1257641. It's quite possible that this bug was fixed by the same thing. Optimistically duping, but please reopen if you see it again. (I also just tested on today's nightly and didn't see it).