[webkit-dev] Detecting a finished paint via JavaScript

Maciej Stachowiak mjs at apple.com
Wed Jul 8 14:21:33 PDT 2009

On Jul 8, 2009, at 10:45 AM, RDC wrote:

>> Would you be willing elaborate on why you want this?
> Of course; I would like it for benchmarking page rendering times-- 
> something I believe would be possible with Web Inspector, but I'm  
> after a cross-browser way of achieving it.
> At the moment I have a benchmark that uses the onLoad event to move  
> onto the next page; on Firefox this sometimes results in pages being  
> "skipped" as the onLoad event is triggered before any painting is  
> done. We use the mozAfterPaint to control this somewhat (though not  
> completely effectively--any DOM manipulation via JS causes further  
> paint events, but by this time the onLoad has fired).
> Thinking more about it, perhaps it is the case that WebKit doesn't  
> behave in exactly the same way, and the afterPaint event is not  
> needed to guarantee that at least *some* of the page is painted  
> before moving on.

If it's for purposes of the Web Inspector, a custom event or callback  
mechanism that's only available to the inspector might do. We probably  
want to avoid exposing the event to Web content initially, since it's  
hard to define the semantics clearly.

  - Maciej

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