You'll find the setting "Display content in resizing windows" there. It sucks that we have to do this though :(
On another note, if I logout of KDE 4 and then back in, fglrx stops providing 3D support. I have to reboot the machine to have composite and 3D in general working again. Can you confirm this?
If you're using Compiz, go into ccs and look for the "Resize Window" settings. Under the General tab there is a pull down menu that lets you set resize modes. If you set it to normal resizing eats up your CPU and the whole thing is slow; setting it to stretch "fixes" it but then you have to look at another silly effect while you resize (but then again, silly effects are the main reason to use Compiz :p).
Don't forget the heavily annoying slowness of maximizing/un-maximizing windows as well restoring them from the taskbar after they were minimized. That is really annoying as hell.
Also the plethora of other bugs of course (hang while switching users or 3D stopping to work after logging out of KDE4 and then back in...)
Using stretch I have no lag. Minimising and restore, still no lag.
A second or so lag on maximising and restore.
I've even reported a bug to AMD - without any results - they're treating users as an idiots... Look at this bug report and stupid answers from AMD/Ati employees: click
In my opinion, the only hope for r600/700 owners is fast development of open sourced 2D/3D driver. Fglrx driver quality is miserable - much more than Nvidia closed source driver.
Just curious, what were the "stupid answers" from the support desk ? All they said was "you're sending this to the wrong place" and offered a couple of alternatives including the recommended bug tracker (the Bugzilla database at http://ati.cchtml.com. Our developers do look at *that* bug tracker.
When you persisted they asked you to read their previous response again (in the "solution" field), ie they were saying "DUDE, YOU'RE BUGGING THE WRONG PEOPLE" as nicely as possible ;)
I'll see if I can get Phoronix added to the list of recommended support forums; I think there may be more Linux activity here than at the sites they mentioned.