Version: (using KDE 4.2.2) Compiler: gcc (Gentoo 4.3.3-r2 p1.1, pie-10.1.5) 4.3.3 CXXFLAGS="-O2 -pipe -march=k8-sse3 " OS: Linux Installed from: Gentoo Packages Steps to reproduce: 0) switch off desktop effects 1) open two or more windows; 2) move one window so that it at least can be intersected by one popup from task panel and at most one popup doesn't intersect it; 3) point mouse to task panel to see popup that intersect window 4) move mouse out of task panel and wait until popup disappeared 5) move mouse to task panel to see popup that doesn't intersect window Result: the area that was under first popup is repainted one more time, but only background and panel repainted, not the window. If repeat same steps but with different panels the panel is not repainted also. See screen shots.
Created attachment 33279 [details] Screen shot for case with one panel
Created attachment 33280 [details] Screen shot for case with two panels
what's your graphics card, driver and X server version?
Radeon HD3200 with proprietary driver from AMD version 8.593 (with opensource radeonhd driver result is the same) X version: X.Org X Server 1.5.3 Release Date: 5 November 2008 X Protocol Version 11, Revision 0
When desktop effects is disabled it's the application's (By Expose events), X's (Correctly sending those Expose events) and driver's (If using a backing store correctly use it) responsibility to repaint the damaged areas, not KWin.
With that said I should mention that I can reproduce it in xorg-server 1.6.1 running nVidia 180.51 drivers (I think? Don't have access to the system right now but it has existed for a while though in different driver versions).