Bug 87571 – WebProcess sends many synchronous messages to the UI process while scrolling beneath ScrollView::contentsToScreen()

• Component: UI Events
• Status: RESOLVED FIXED

<rdar://problem/11439771>

Looking at a WebProcess sample from scrolling a fairly simple page, I noticed over a 1/10 of the time was spent beneath ScrollView::contentsToScreen() waiting on a synchronous message to the UI process. This function is called from EventHandler::fakeMouseMoveEventTimerFired().

Created attachment 144194 [details]
Store and use the last known mouse position in screen coordinates

[Simon Fraser (smfr)]

Comment on attachment 144194 [details]
Store and use the last known mouse position in screen coordinates

View in context: https://bugs.webkit.org/attachment.cgi?id=144194&action=review

> Source/WebCore/page/EventHandler.h:428
> +    IntPoint m_currentMouseGlobalPosition;

Does "global" always equate to "screen" on systems with more than one screen?

(In reply to comment #2)
> (From update of attachment 144194 [details])
> View in context: https://bugs.webkit.org/attachment.cgi?id=144194&action=review
> 
> > Source/WebCore/page/EventHandler.h:428
> > +    IntPoint m_currentMouseGlobalPosition;
> 
> Does "global" always equate to "screen" on systems with more than one screen?

Not sure. If not, then this makes the fake event more faithful, since it just replicates the global position of the last real event.

Thanks for the review!

Fixed in <http://trac.webkit.org/r118611>.