[Webkit-unassigned] [Bug 154864] New: repetitively focusing text input elements results in severe performance decrease

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=154864

            Bug ID: 154864
           Summary: repetitively focusing text input elements results in
                    severe performance decrease
    Classification: Unclassified
           Product: WebKit
           Version: Safari 9
          Hardware: iOS
                OS: iOS 9.2
            Status: NEW
          Severity: Major
          Priority: P2
         Component: WebKit2
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: tshoppainfo at gmail.com

switching focus between html text input elements has an impact on the overall performance.
This effect can be best observed when switching focus several (200-300) times, after witch the displayed page
becomes virtually unusable (extremely sluggish).

This is a simple fiddle to reproduce the bug:

http://jsfiddle.net/mzL205bL/

pressing "focus" button successively transfers the focus to all 100 inputs.
Repeat 3 times on IOS 9 Safari/Chrome/firefox for a strong effect.

Same effect appears when focus is set manually or over a longer time period.

Browser does not recover by time nor when page is reloaded (Tab has to be closed).

The bug seems to be related to the engine used in WkWebView, as it is reproducible on latest IOS 9 Chrome and Firefox Versions, but not on UIWebView based Browsers or on IOS 8 Version of Chrome.

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