"--scale 2x2" in xrandr causes the monitor to not display anything

Just wanted to add that this is something I've been fighting with for a long time, and each time I just gave up - until I decided to figure it out once and for all. The solution below works for me, hope it does for you as well.

tl;dr: Configure ForceFullCompositionPipeline=On

Background

Some of this is also in hopes of providing more keywords in case someone with a similar problem ends up looking for the solution.

My setup is:

• ThinkPad P50 with a built-in 4K display at 3840×2160 (primary)
• An external monitor as a secondary display - Dell U2412M - 1920×1200

I use Ubuntu Gnome 16.04 LTS.

When I plug in the monitor via a HDMI cable + a HDMI-to-DVI converter (as the monitor doesn't have an HDMI input), everything was too large. Various articles online suggested using xrandr to configure --scale 2x2 on that display, which resulted in it being almost completely black, with only a thin line visible on top.

I bumped into this question and while the 2x2.001 scaling solution enabled the monitor to actually display stuff, it also added an extra pixel below the X screen which resulted in slight up/down scrolling when the cursors reaches the top/bottom of the screen.

After a lot of Googling, much of which yielded problems and no solutions, I stumbled upon this: https://devtalk.nvidia.com/default/topic/891207/-355-11-358-09-viewportin-on-2nd-monitor-results-in-garbled-display-for-values-over-3211x1800

So to test it out, I configured this using the following commands - assume xrandr hasn't been configured with scaling yet.

$ nvidia-settings -q CurrentMetaMode

  Attribute 'CurrentMetaMode' (lilicorp:1.0): id=50, switchable=no, source=RandR :: DPY-4: nvidia-auto-select @3840x2160 +0+0 {ViewPortIn=3840x2160, ViewPortOut=3840x2160+0+0}, DPY-1: nvidia-auto-select @1920x1200 +3840+0 {ViewPortIn=1920x1200, ViewPortOut=1920x1200+0+0}

This displays the CurrentMetaMode value and this is where I added the ForceFullCompositionPipeline=On option to both displays. Note that DPY-4 is my built-in laptop display, whereas DPY-1 is the external monitor.

The actual string that needs to be configured is the one after :: in the output of that command.

$ nvidia-settings --assign CurrentMetaMode="DPY-4: nvidia-auto-select @3840x2160 +0+0 {ViewPortIn=3840x2160, ViewPortOut=3840x2160+0+0, ForceFullCompositionPipeline=On}, DPY-1: nvidia-auto-select @1920x1200 +3840+0 {ViewPortIn=1920x1200, ViewPortOut=1920x1200+0+0, ForceFullCompositionPipeline=On}"

After this, I ran:

$ xrandr --output DP-1 --scale=2x2

Finally, the external display resolution was fine with no scrolling or any other issues.

Note that after running those commands, the CurrentMetaMode is a bit different from what was assigned, probably due to the scaling getting applied:

$ nvidia-settings -q CurrentMetaMode

  Attribute 'CurrentMetaMode' (lilicorp:1.0): id=50, switchable=no, source=RandR :: DPY-4: nvidia-auto-select @3840x2160 +0+0 {ViewPortIn=3840x2160, ViewPortOut=3840x2160+0+0, ForceCompositionPipeline=On, ForceFullCompositionPipeline=On}, DPY-1: nvidia-auto-select @3840x2400 +3840+0 {Transform=(2.000000,0.000000,0.000000,0.000000,2.000000,0.000000,0.000000,0.000000,1.000000), ViewPortIn=3840x2400, ViewPortOut=1920x1200+0+0, ResamplingMethod=Bilinear, ForceCompositionPipeline=On, ForceFullCompositionPipeline=On}

Hope this solves the problem for someone else too!

I had exactly the same problem. I got it resolved with --scale 2x2.001. Oddly enough, --scale 2x1.999 or 2x2.0001 didn't work, so be sure to try several numbers around 2.

Thank you Milos for your excellent solution, which worked well for me!

I've a small addition. Besides using the command line you can also comfortably set the ForceFullCompositionPipeline in the Nvidia-Settings UI. For this you've to go to "X Server Display Configuration", click on "Advanced" and just activate the option "Force Full Composition Pipeline". Please see https://imgur.com/a/3jE78 for an example.

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PS: I'm using a triple-head setup with two external monitors (1920x1080; 1680x1050) and an internal 3k monitor (3840x2160). For this to work I apply the following xrandr-config:

xrandr --output eDP-1-1 --auto --output HDMI-0 --auto --scale 2x2 --above eDP-1-1 --output DP-1 --auto --scale 2x2 --rotate left --right-of eDP-1-1