1219241 - Incorrect scroll position when loading a specific site

Status: RESOLVED WORKSFORME

(Firefox for iOS :: General, defect)

Description

[Catalin Suciu [:csuciu]]

Build: Beta 1113
Devices: iPod Air 6 (iOS 9.1), iPhone 4S (9.0)

Steps: 
1. Visit www.ziare.com
2. Check the the scroll position on the page 

Result: The page is scrolled down
  
https://www.youtube.com/watch?v=JYla4AdlV60

Note: Doesn't reproduce on Safari

Comment 1

[Richard Newman [:rnewman]]

Needs investigation.

Comment 2

[Emily Toop (:fluffyemily)]

Oddly, this is an issue that only manifests on device - I can't replicate it in the simulator.

We are calling viewDidLayoutSubviews after starting to load www.ziare.com but before the redirect to m.ziare.com has taken effect from BrowserScrollController: animateToolbarsWithOffsets, causing the desktop site to partially render, before redirection causes the mobile site to render. This then loads to mobile site with an odd scroll position.

If you open m.ziare.com directly, the odd scroll position rendering does not occur. However, since I loaded m.ziare.com directly, I have not been able to replicate the original redirection issue, even after clearing my cache....

Comment 3

[Emily Toop (:fluffyemily)]

Attachment: Pull request

Comment 4

[Brian Nicholson (:bnicholson)]

Comment on attachment 8687987 [details] [review]
Pull request

Unfortunately, I'm still able to reproduce this issue with the PR applied. I found that I'm also able to reproduce even if I go to m.ziare.com directly.

Maybe it's a race affected by network, etc.? Otherwise, I wonder if they're serving different content to the UK.

Comment 5

[Brian Nicholson (:bnicholson)]

FWIW, just tried reproducing in the simulator and saw the same issue there, too. Strangely, I've had trouble finding any cases where this *doesn't* happen, which sounds like the opposite of what you're seeing!

Comment 6

[Emily Toop (:fluffyemily)]

Bugger. I was worried that would be the case. Once I stopped being able to replicate the issue it became very difficult to track down.

Comment 7

[Emily Toop (:fluffyemily)]

It's a latency thing. If I set the Network Link Conditioner to Very Bad Network I can reproduce this 3 times out of every 5. 

My patch did _something_. It is less frequent with this patch than it was before, but the problem still manifests.

Comment 8

[Catalin Suciu [:csuciu]]

I'm unable to reproduce this issue on latest master.