Bug 178066 – Cordova: elements with tag position:fixed disappears (flickering) when a long content is scrolling and appears again when the scroll is finished.

• Component: CSS
• Status: RESOLVED FIXED

A-  Overview: 
Elements width position:fixed disappears (flickering) when a long content is scrolling and appears again when the scroll is stoped.

B - Steps to Reproduce: 

1) Create a simple html page into a cordova proyect (for example) 

2) Put a div on the top and another on the buttom width "position:fixed" atribute. Include also a long text to make posible scroll it.
I use for my test this simple estructure: http://www.oscarabilleira.com/test_ios/index.php, just copy the source code and create a html file in a cordova proyect for example.

3) When scrolls the text into the webkit the "fixed elements" disappears until the scroll is finished, only if there's a long content to scroll, like in the example. In other situations (randomly) the "flickering efect" can be shown even with a short content to scroll.


C- Expected Results: 
When scroll the content the elements with "position:fixed" tag must be shown all the time even when the content is scrolled.


D- Build Date & Hardware: 
After update to iOS 11 and actually with iOS 11.0.2 
Tested iphone 7, iphone 7 plus and ipad air 2.
Doesn't Occur using iOS 10.x.x or earlier.


E- Additional Information: 
The same like in this old bug 
https://bugs.webkit.org/show_bug.cgi?id=137851

[Simon Fraser (smfr)]

Does this happen with the WKWebView version of Cordova (http://blog.ionic.io/cordova-ios-performance-improvements-drop-in-speed-with-wkwebview/)?

I have tested and using WKWebView works fine

[Radar WebKit Bug Importer]

<rdar://problem/34898141>

[Simon Fraser (smfr)]

rdar://problem/34808762

[Simon Fraser (smfr)]

I can reproduce. Investigating.

[Simon Fraser (smfr)]

Ah, we only call GraphicsLayer::setIsViewportConstrained() in the WKWebView code path, for coordinated scrolling.

[Simon Fraser (smfr)]

Created attachment 326420 [details]
Patch

[WebKit Commit Bot]

Comment on attachment 326420 [details]
Patch

Clearing flags on attachment: 326420

Committed r224617: <https://trac.webkit.org/changeset/224617>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.

[Darryl Pogue]

This has been merged, but I'm guessing it missed the cut-off date for inclusion in iOS 11.2 because the issue still exists there

[Simon Fraser (smfr)]

Correct.