After a bit of experimenting, my only guess is that in "selection" mode, the
window is in the background and not the foreground as it is with "window"
mode (Grab is the foreground process during selection mode.) This is
probably forcing the card to not accelerate as much of the drawing as it was
before and place the image in AGP memory. Since most cards can only fully
accelerate one window at a time (the foreground window), the others have to
fall back on some software rendering functions.
This is common not only on Macs, but also on PCs. It's the same reason that
some video doesn't show up during a capture. The video card is accelerating
the blt of the video to the screen. Or in ATIs case, I believe they actually
do MPEG decoding right on the card. Hence the video image never has a
reason to come back into AGP memory, and you get a big blank spot during a
capture. Going from the video card to AGP memory is extremely slow.
----- Original Message -----
From: "Karin Kosina" <email@hidden>
To: "Stephen Manchester" <email@hidden>
Cc: <email@hidden>
Sent: Monday, September 27, 2004 5:23 PM
Subject: Re: Screenshot of a window containing an NSOpenGLView
> On Mon, 27 Sep 2004 17:18:46 -0700, Stephen Manchester
> <email@hidden> wrote:
> > When you do a screen capture, it is capturing the system (AGP) memory
> > resident portion of video memory. Since many 3d views are handled
> > exclusively by the video card, there is no system memory representation
of
> > that data. Screen captures do not (usuallly) pull the data directly off
the
> > card, they pull it from the system (AGP) memory resident copy.
>
> This is interesting, thanks for the insight.
>
> You don't happen to have an idea why the behaviour is different for
> "window" vs. "selection" mode, do you?
>
> Cheers, kyrah
>
> --
> We are Elektropeople for a better living.
>
> Karin Kosina, KSC (vka kyrah)
> http://kyrah.net
>
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