XGetImage returns junk with Xorg/dummy_drv/VTs

Adam Jackson ajax at nwnk.net
Mon Nov 24 10:06:38 PST 2008

On Mon, 2008-11-24 at 10:19 -0700, McDonald, Michael-p7438c wrote:

> > Yes, it does that.  When Xorg loses the VT, it empties the 
> > clip list for the root window.  All drawing to the root window gets
> > thrown away, and all readbacks from it do nothing (which looks like 
> > uninitialized data).
>   Why would it do that? X apps don't know anything about VT switching,
> nor should they.

Because when you don't have the VT, you don't have the hardware, so you
can't submit commands to it.  We don't preserve the framebuffer when we
VT switch away, we just generate exposures for all windows when we
restore X.

There was some debate about this way way back in like xfree86 4.0 or so.
I don't remember what the motivation was for what we've got now, but
it's what we do, so...

- ajax
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