[webkit-dev] Detecting a finished paint via JavaScript

Darin Fisher darin at chromium.org
Wed Jul 8 10:57:27 PDT 2009

While this is not a perfect solution, a common technique is to call (from
onload) a DOM method like offsetHeight that forces layout to run.  That way
the bulk of the work required to paint is forced to happen before the
benchmark considers the page load complete.

On Wed, Jul 8, 2009 at 10:45 AM, RDC <rdc49360 at googlemail.com> 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.
> -R
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