Re: Window resizing _very_ slow with compiz
It's not the allocation that's slow. After allocating the new pixmap, the server copies pixels from the parent window into the new pixmap. For X.org 7.2 and earlier, this used XCopyArea but this turned out to be a security problem for certain windows, so they switched to the RENDER extension's Composite call instead for X.org 7.3. Since pixmaps start out in sysmem by default, this falls back to software *every single time the window is resized*.