KDE4: Multi head multi X servers causes desktops to be rendered on top of one another

[JB]

I run a current Kubuntu system with a dual head NVidia card and the proprietary NVidia drivers. For various reasons I have to run the dual head as two X servers. My current X config runs fine with KDE3, when running KDE4 however both heads desktops are drawn on top of one another on only one of my displays, the other display is inaccessible. Additionally the desktop config tool under KDE3 correctly identifies the two displays but under KDE4 it sees only one of the displays. I enquired about this problem on the Kubuntu-kde4 IRC channel where another user reported the same issue, but no known fix.

Description: Ubuntu 8.04
Release: 8.04

It affects any of the KDE4 versions I have tried over the last 6 months of tracking.

xorg.conf:

Section "ServerLayout"
    Identifier "Layout0"
    Screen 0 "Screen0" RightOf "Screen1"
    Screen 1 "Screen1" 0 0
    InputDevice "Keyboard0" "CoreKeyboard"
    InputDevice "Mouse0" "CorePointer"
EndSection

Section "Files"
    RgbPath "/usr/X11R6/lib/X11/rgb"
EndSection

Section "Module"
    Load "dbe"
    Load "extmod"
    Load "type1"
    Load "freetype"
    Load "glx"
EndSection

Section "ServerFlags"
    Option "Xinerama" "0"
EndSection

Section "InputDevice"
    # generated from default
    Identifier "Mouse0"
    Driver "mouse"
    Option "Protocol" "auto"
    Option "Device" "/dev/psaux"
    Option "Emulate3Buttons" "no"
    Option "ZAxisMapping" "4 5"
EndSection

Section "InputDevice"
    # generated from default
    Identifier "Keyboard0"
    Driver "kbd"
EndSection

Section "Monitor"
    # HorizSync source: twinview, VertRefresh source: twinview
    Identifier "Monitor1"
    VendorName "Unknown"
    ModelName "ViewSonic VX715"
    HorizSync 31.5 - 80.0
    VertRefresh 60.0
    Option "DPMS"
EndSection

Section "Monitor"
    # HorizSync source: edid, VertRefresh source: edid
    Identifier "Monitor0"
    VendorName "Unknown"
    ModelName "ViewSonic VX2235wm"
    HorizSync 30.0 - 82.0
    VertRefresh 50.0 - 75.0
    Option "DPMS"
EndSection

Section "Device"
    Identifier "Videocard0"
    Driver "nvidia"
    VendorName "NVIDIA Corporation"
    BoardName "GeForce 7600 GT"
    BusID "PCI:2:0:0"
    Screen 0
EndSection

Section "Device"
    Identifier "Videocard1"
    Driver "nvidia"
    VendorName "NVIDIA Corporation"
    BoardName "GeForce 7600 GT"
    BusID "PCI:2:0:0"
    Screen 1
EndSection

Section "Screen"
    Identifier "Screen1"
    Device "Videocard0"
    Monitor "Monitor1"
    DefaultDepth 24
    Option "metamodes" "DFP-1: 1280x1024 +0+0; DFP-1: 1024x768 +0+0"
    SubSection "Display"
        Depth 16
        Modes "1600x1200" "1280x1024" "1024x768" "800x600" "640x480"

        Depth 24
        Modes "1600x1200" "1280x1024" "1024x768" "800x600" "640x480"

        Depth 32
        Modes "1600x1200" "1280x1024" "1024x768" "800x600" "640x480"
    EndSubSection
EndSection

Section "Screen"
    Identifier "Screen0"
    Device "Videocard1"
    Monitor "Monitor0"
    DefaultDepth 24
    Option "metamodes" "DFP-0: 1680x1050 +0+0; DFP-0: 1280x1024 +0+0; DFP-0: 1024x768 +0+0"
    SubSection "Display"
        Depth 16
        Modes "1600x1200" "1280x1024" "1024x768" "800x600" "640x480"

        Depth 24
        Modes "1600x1200" "1280x1024" "1024x768" "800x600" "640x480"

        Depth 32
        Modes "1600x1200" "1280x1024" "1024x768" "800x600" "640x480"
    EndSubSection
EndSection