1412819 - Switching to a new opened tab may show toolbar when it shouldn't (TabScrollController KVO bug)

Status: NEW

(Firefox for iOS :: General, defect, P3)

Description

[Catalin Suciu [:csuciu]]

master d80fd66a
v10.0(7473)

1. Go to www.bbc.com.
2. Scroll to hide the toolbars.
3. Long tap on a link and select "Open in New Tab".
4. Switch to the new tab via the toast. 

Result: 
 - on iOS 10 the toolbars are displayed in the new tab.
 - on iOS 11 the toolbars are not displayed in the new tab.

I'm not sure which behavior is correct but it should be consistent across iOS versions.

Comment 1

[:garvan]

Correct behavior is to not show the toolbars once they are hidden.

On iOS 10 iPhone 6 Simulator I can't reproduce this, however I am building from master branch.

Comment 2

[:garvan]

I built v10.x in simulator. On v10x and master I can get bbc.com to trigger this but not other sites.

Any site could show the toolbars if the rendering of the page triggers a webview content size notification. The TabScrollController listens for this event (KVO) and shows the toolbar. I am sure we could get this to happen on 11, however I assume WKWebView on iOS 11 is more selective about when it sends content size notifications.

This code should be fragile and the KVO should be made more selective or removed entirely (maybe as part of tech debt work).

Comment 3

[:garvan]

Correction: `This code should be fragile` -> This code is fragile