Dual-screen partial overlap on Ubuntu 18.04

I have 2 monitors set up with my Ubuntu system, primary (landscape) and a secondary rotated (portrait) monitor to the left of it. I've been having a problem where there's about a 2-pixel wide overlap from the secondary monitor onto the primary. This isn't window-specific (as in, its not a window-bleed, its the entire leftmost columns of the secondary framebuffer).

This issue doesn't occur with both monitors set to landscape. On top of this, strangely, it doesn't occur with the secondary monitor set to portrait and set to the right of the primary monitor. Another thing to note is that when arranging the monitors with display settings, there's a space between the monitors when placing the secondary to the right, but no space when placing the monitor to the left.Here's a side-by-side comparison of monitor arrangement in gnome-control-center.

This led me to believe the issue may be in the treatment of rotated screens in gnome-control-center (not rotating around the true origin?) so I started looking at the source for it, making small modifications but to no avail.

I've tried manually setting monitor positions with xrandr, but the issue I ran into there was that the 'screen' framebuffer (for the overall desktop) ended up consisting of a full bounding box of both monitors (i.e. windows in the primary display could go above and below the monitor due to the secondary monitor being a higher vertical resolution).

System-wise, I'm running Ubuntu 18.04 with Wayland disabled (completely different kettle of fish with Wayland), with an AMD Rx370 primary GPU (AMDGPU driver) and an NVidia gtx 660 GPU for compute (NVidia 396 driver).

Just wondering if anyone has any ideas of what's going on, or if anyone could confirm that this is a true bug in gnome-control-center/X11 that's worth opening a tracker on.

Thanks

2 Answers

I started to see same in Ubuntu 18.04. I never got success with desktop display adjuster, either running Gnome or Xfce4. The problem happens for me when I move from various projectors with different resolutions.

You can fix if you install the GUI program arandr, a nice interface to xrandr. arandr gives easy to drag overlapped window out of way.

This noob worked it out as well before finding this! This is similar to the above arandr answer but without installing any software. Shared at noob level as that's what I appreciate myself...

Mine was a two pixel overlap (left primary overlaps onto external right hand screen) and here is how I eradicated it on Xubuntu 20.04 with the XFCE desktop environment.

Using the terminal (Ctrl-Alt-T to run) type the following commands:

xrandr -q (Which queries which monitors you have and their settings)

then refer to BatchyX's excellent answer for help and using the information from the above command, type something like the following:

xrandr --output HDMI-0 --pos 1368x0

• Where HDMI-0 is my screen that I wanted to move; change this to yours.
• And where its previous position (--pos) was 1366, 0 (I added 2 pixels to it's x position and left it's y position alone)

Finally, I opened the Control Panel, Display settings then selected the 'Advanced' tab. I saved or updated the appropriate profile so that when this monitor connects, it will always resume this arrangement.

Note: This actually leaves a 2 pixel blind spot or hole between the two monitors. You could add more than 2 but then you could lose things like cursors/windows in this hole...

Note 2: Now I recall that this might have happened on other external screens/projectors so perhaps my best bet would have been to move the primary screen left by 2 pixels, that would be xrandr --output eDP --pos -2x0 but I'm going to stop faffing now. Good luck.