Version: (using KDE 4.3.2) Installed from: Debian testing/unstable Packages In a multiple display setup, the cursor shouldn't be allowed to simply go to the other display. The edge should pose some resistance, for example only continually moving the mouse for 10 pixels or more should allow it to pass to the other display. Other method are good as well. Why: the edge is a sweet spot for grabbing a scrollbar, for resizing a window, and maybe others. KWin already does this for windows, they don't simply pass to another display when they are moved. The only possible problem I see for this is if an application is if an application is on two screens, the user would expect the cursor to behave as usual. This would be bad especially for games.
This has to be done at the X server level as the pointer is processed on the server.
Upstream bug at https://bugs.freedesktop.org/show_bug.cgi?id=25474