I'm currently setting up a new Xen paravirt domain running KDE (4.2.2, from Kubuntu 9.04). As I have been unable to get the virtual framebuffer working in it, I've decided to set up VNC (from the vnc4server package), and run KDE over Xvnc.
This is all fine and good, and KDE starts up okay. However, all the colours look dithered, especially on the task bar and title bar, making them impossible to see. From my web searches, it appears to be because these items are drawn using Porter-Duff. This is especially the case when using the Oxygen style, and Oxygen and Ozone window titlebars (selecting these styles generates messages about Porter-Duff being unavailable); not using those styles at least makes most of the UI widgets and window titles usable again.
But this doesn't solve the problem for the task bar, nor for the desktop, where the only theme available to me is Oxygen (this is under the "Desktop Settings - Plasma Workspace" window, just for reference). So, unless I have a way to use a non-Porter-Duff theme for those, it seems that KDE would still be unusable under VNC.
So if someone experienced with KDE can advise on how to work around, or even fix, these issues, I'd appreciate it very much. :-)
