Goal
I want to use KDE across two monitors, but I only want the window manager to see them as one single virtual monitor. I would like to achieve this goal either using KDE settings, nvidia-settings, or xorg.conf.
What I've tried
I have tried enabling Xinerama in my xorg.conf file and it works at the login page, but then the Plasma desktop doesn't load. I get no taskbar and have to use alt-F2 to run anything, as well as encounter lots of other problems. I have also tried TwinView as I am running nvidia, but I get the same above problems.
More info
Basically I want the taskbar to stretch across both screens, and to be able to maximize windows to take up both screens. I've had this problem in every flavor of Ubuntu (Ubuntu 15, Kubuntu, Mint 17) and every window manager (Openbox, Compiz, Awesome) I've tested.
Here is a screenshot of what I see:
xorg.conf
# nvidia-settings: X configuration file generated by nvidia-settings
# nvidia-settings: version 361.42 (buildd@lgw01-18) Tue Apr 5 14:33:28 UTC 2016
Section "ServerLayout"
Identifier "Layout0"
Screen 0 "Screen0" 0 0
InputDevice "Keyboard0" "CoreKeyboard"
InputDevice "Mouse0" "CorePointer"
Option "Xinerama" "0"
Option "Twinview" "true"
EndSection
Section "Files"
EndSection
Section "Module"
Load "dbe"
Load "extmod"
Load "type1"
Load "freetype"
Load "glx"
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: edid, VertRefresh source: edid
Identifier "Monitor0"
VendorName "Unknown"
ModelName "DELL UP2414Q"
HorizSync 31.0 - 140.0
VertRefresh 29.0 - 75.0
Option "DPMS"
EndSection
Section "Device"
Identifier "Device0"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BoardName "GeForce GTX 970"
EndSection
Section "Screen"
Identifier "Screen0"
Device "Device0"
Monitor "Monitor0"
DefaultDepth 24
Option "nvidiaXineramaInfoOrder" "DFP-2.9"
Option "metamodes" "DP-0.8: nvidia-auto-select +1920+0, DP-0.9: nvidia-auto-select +0+0"
SubSection "Display"
Depth 24
EndSubSection
EndSection
Other window managers might work better, but I really like the one in Plasma 5 and would prefer to keep using it.