Extended desktop with Optimus in Linux

Question

The issue I'm experiencing is extending my desktop, it also pans 1 monitor to the entire viewport of all screens.

This is what I'm dealing with:

Dell XPS L702X

sudo lspci | grep VGA
00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09)
01:00.0 VGA compatible controller: NVIDIA Corporation GF106M [GeForce GT 550M] (rev a1)

This is not the first time I had issues with Optimus in Linux (not by a long shot) but recently I've bought another screen and I wish to extend it to that one instead. Before I extended my internal display with a secondary one via mDP which worked.

The setup:

Monitor left is connected to the mDP port that is controlled by the intel card. Monitor right is connected to the HDMI port that is controlled by the nVidia card.

I have a default xorg.conf from the arch wiki (only setup that worked for me):

Section "Module"
    Load "modesetting"
EndSection

Section "Device"
    Identifier "nvidia"
    Driver "nvidia"
    BusID "PCI:1:0:0"
    Option "AllowEmptyInitialConfiguration"
EndSection

I currently have nvidia driver 364.19-2 installed.

The xrandr output (stripped from excessive resolution output)

Screen 0: minimum 8 x 8, current 3840 x 1080, maximum 16384 x 16384
HDMI-0 connected 1920x1080+1920+0 (normal left inverted right x axis y axis) 598mm x 336mm panning 3840x1080+0+0
   1920x1080     60.00*+  59.94    50.00    60.00    50.04  
LVDS-1 connected (normal left inverted right x axis y axis)
   1920x1080     60.01 +  40.01  
VGA-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 connected primary 1920x1080+1920+0 (normal left inverted right x axis y axis) 598mm x 336mm
   1920x1080     60.00*+  50.00    59.94  
DP-1 disconnected (normal left inverted right x axis y axis)
  1920x1080 (0x2b8) 148.500MHz +HSync +VSync
        h: width  1920 start 2008 end 2052 total 2200 skew    0 clock  67.50KHz
        v: height 1080 start 1084 end 1089 total 1125           clock  60.00Hz
  1920x1080 (0x2ba) 148.500MHz +HSync +VSync
        h: width  1920 start 2448 end 2492 total 2640 skew    0 clock  56.25KHz
        v: height 1080 start 1084 end 1089 total 1125           clock  50.00Hz

The issue

If in the KDE control panel I have monitor mDP on the left side and Monitor HDMI on the right it seems to work, only my mouse is stuck on the right side of the screen and I cannot move it to the left screen.

If in the KDE control panel I have monitor mDP on the right, and HDMI on the left, I can move my mouse to the right but what happens is that monitor HDMI scrolls horizontally to the mDP output so I have a cloned output. If I move left with my mouse, the left side of the desktop scrolls back. I believe the output of xrandr explains this behavior however this happens on the right monitor, connected to the HDMI not the mDP.

Answer 1

After struggling with this issue I've finally resolved the issue.

The reason why this is happening is that the Intel card acts as a sink provider for the nVidia card, meaning all screens are captured there and send back again. This caused xrandr to behave as it did cause it cannot render a 5760x1080 on a 1080p screen.

So fooling the system instead of fixing it resolved the issue for me. I did so with this script, but I cannot take credit for the idea.

xrandr --output HDMI-1 --mode 1920x1080 --pos 0x0 --panning 5760x1080+0+0/0x0+0+0/0/0/-3840/0
xrandr --output HDMI-0 --mode 1920x1080 --pos 1920x0 --panning 5760x1080+0+0/0x0+0+0/-1920/0/-1920/0
xrandr --output LVDS-1 --mode 1920x1080 --pos 3840x0 --panning 5760x1080+0+0/0x0+0+0/-3840/0/0/0

Source

I've modified the values to fit my monitor connections and resolutions. The next thing I did is making a bash file that runs on system startup that determines my connected monitors and manually execute xrandr commands from there. Usefull, if I bring my notebook along disconnecting the other monitors.