XGetImage returns junk with Xorg/dummy_drv/VTs

[McDonald, Michael-p7438c]

> -----Original Message-----
> From: Peter Harris [mailto:peter.harris at hummingbird.com] 
> Sent: Monday, November 24, 2008 11:18 AM
> To: McDonald, Michael-p7438c
> Cc: xorg at lists.freedesktop.org
> Subject: Re: XGetImage returns junk with Xorg/dummy_drv/VTs

> Basically, unless you are taking a screen shot, XGetImage is the wrong
> thing to do. And if you *are* taking a screen shot of a 
> screen that has
> switched to another VT, "junk" is the correct result. 

  I'm only doing XGetImage on the root window. And I strongly disagree
that "junk" is the correct result. In my example of running
Xorg+dummy_drv, how can returing junk be considered the "correct"
result? Dummy_drv's memory based framebuffer still has the pixels in it.
OK, if I'm running multiple X servers sharing the same card, then junk
might be a reasonable answer.

  But heck, Xorg isn't even consistant in returning junk! If I start
Xorg+dummy on a machine running Xorg+nvidia, I get good results. If I
run Xorg+dummy on a machine running Xorg+intel, I get junk. If I run
Xorg+dummy on a machine with no other X server, I get junk. What is
Xorg+nvidia doing "wrong"?

> Workaround (or, arguably, bug fix): Don't use XGetImage.

  And how is that a workaround?