[webkit-dev] Nesting Level of DOMTimer (non-one-shot timer)

Gavin Barraclough barraclough at apple.com
Fri Oct 10 10:22:22 PDT 2014

Yep, looks like a pretty straightforward problem – the timer nesting level should also be being cleared before the early return in DOMTimer::fired.

Please file a bug!


> On Oct 10, 2014, at 8:19 AM, 陈浩 <chenhao at ucweb.com> wrote:
> Hi, all,
> I am confused about the nesting level of DOMTimer.
> First, there is a long story which come from:
>    https://bugs.webkit.org/show_bug.cgi?id=42861
> Current situation is the timer could forward the gesture state only if the nesting level is zero. The problem is the nesting level is managed in the Document (ScriptExecutionContext), that means all timers in the same document share one nesting level. If one repeat timer was launched, all other timers after that could not forward the gesture state, due to all of them has a non-zero nesting level.
> Below is my testing page, three images at the end of page could delay the onload event. You could follow below steps to reproduce what I met:
> 1. Click "Start repeating timer" first
> 2. After the text change to "Running...", click "Goto next page"
> 3. When WebKit page come out, click back button.
> What I see is the page before the testing page, because the NavigationScheduler::mustLockBackForwardList refused the creation of new history item.
>  <html>
>  <head>
>  </head>
>  <body>
>  <input type="button" value="Goto next page" onclick="gotoNextPage();">
>  <input type="button" value="Start repeating timer" onclick="startRepeatingTimer();">
>  <p>
>  <div id="Timer">Paused</div>
>  </p>
>  <script type="text/javascript">
>  function gotoNextPage(){
> setTimeout(function(){location.href="http://www.webkit.org/";},300);
>  }
>  function startRepeatingTimer(){
> setInterval(function(){document.getElementById("Timer").innerHTML="Running...";},500);
>  }
>  </script>
>  <img src="http://therecoveringpolitician.com/wp-content/uploads/2013/01/moderate.jpg" width="640" height="480">
>  <img src="http://cullogo.com/full/wallpapers-high-resolution-widescreen-hd-pk.jpg" width="640" height="480">
>  <img src="http://www.highresolutionwallpapers.net/wallpapers/autumn-1680x1050.jpg" width="640" height="480">
>  </body>
>  </html>
> According to Web App APIs defintion(http://www.w3.org/html/wg/drafts/html/CR/webappapis.html#timer-nesting-level), the nesting level of repeating timer will be increased in the loop. I doubt that the nesting level should owned by the timer itself, do not share with others. Just as described in the defintion, that is task's nesting level.
> That's appreciate to get your comment!
> Thanks & Best Regards!
> Hao
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