[Webkit-unassigned] [Bug 21495] Need "--onscreen" option on DRT tool

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=21495





------- Comment #8 from pol at apple.com  2008-10-10 12:15 PDT -------
> I'd be very curious as well.  Could you maybe post some explanation in the bug?
>  Chromium's test_shell also renders onscreen, but I'd like them to move towards
> a model similar to DRT where the window is offscreen instead.  You sound like
> you have reasons not to move to such?  When is the backing store for a window
> going to be different from the contents captured some other way?  When OpenGL
> is in play?

You are correct: if there's a GL surface on the window, like for the Apple
Quartz Composer webkit plug-in, or third party plug-ins that use GL, by
definition the rendering of these plug-ins is not in the window backing. So to
get a proper snapshot, you need to use the new APIs in CG introduced in 10.5
(or read directly from the framebuffer, but it's more complicated).

There are probably other cases I can't think of (maybe if the bits put on
screen are "touched" in any way when blit from the window backing like color
matching).


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