[SOLVED] creating xrandr virtual displays

obobskivich · 06-01-2021, 03:15 PM

I've run into a bit of a roadblock trying to figure out the xrandr --setmonitor command - my goal is to create a virtual display constituted of three physical displays (similar to Eyefinity). I found this documentation (plus the manpage): http://www.straightrunning.com/tools/xrandr.html#sect3 and https://wiki.archlinux.org/title/Mul...irtual_display

I can run the --setmonitor command like so (via terminal emulator inside the XFCE session):

Code:

 
xrandr --setmonitor Test auto DisplayPort-1,DisplayPort-2,DisplayPort-3

And then when running

Code:

xrandr --listmonitors

it will show 'Test' as a valid monitor (as 'monitor 0' specifically), however nothing in XFCE nor ARandR 'sees' this virtual display, and it treats all three still as independent displays (1, 2, and 3, respectively). The 'setmonitor' also does not seem to survive reboot, and (probably should have been obvious) cannot be run without X running (e.g. from tty session with XFCE stopped - just returns 'cannot open display'). I get the sense I need this command running 'while' or 'before' XFCE starts, but I'm not clear on how to do that, or if that sense is indeed accurate. I tried googling around for this and found a patchwork of either very old threads or guides for slicing up a single physical display into multiple virtual monitors (to set 'boundaries' for full-screen applications I guess) but neither quite applied to my desired outcome (combining physical outputs into a single 'display'). Any help would be appreciated.

Specifics about this machine:
- Xubuntu 20.04.2 LTS with XFCE (DE: Xfce; WM: Xfwm4)
- Graphics card is a Radeon Vega Frontier Edition (and everything is attached here so there's no multi-GPU/GPU-switching/etc hijinks to work around)
- Graphics driver: amdgpu (I don't quite understand the versioning here but I believe '20.2.6' is correct if I am understanding it right)
- The monitors are all identical in specification/geometry.

Any help would be appreciated, thanks.

EDIT with solution:

So I poked around with it a bit more, and came up with a solution. To make this work:

Step 1:
Run the

Code:

xrandr --setmonitor

command with the displays you want to 'merge' - I called it 'Big' for this but it doesn't matter what you call it:

Code:

 xrandr --setmonitor Big auto [display names go here, separated by commas, with NO SPACES]

Step 2:
Confirm that it did it, by running

Code:

xrandr --listmonitors

You should see 'Big' as one of the options (or whatever you put in place of Big)

Step 3:
Send the 'framebuffer' command to xrandr - this is specified as width (pixels) x height (pixels), and has to encompass the entire Xscreen, so for this configuration (with a trio of 1080p displays) you would run

Code:

xrandr --fb 5760x1080

And voila - it will 'blink' and you've got one big surface, which windows will fullscreen across (as opposed to per-monitor), and which will behave more or less like Eyefinity (which was my goal).

To undo there's one extra command:

Code:

 xrandr --delmonitor Big

(or whatever you called it instead of Big)

Then re-run the framebuffer command from Step 3, and the monitors will 're-appear' as independent displays within the Xscreen.

boughtonp · 06-02-2021, 08:15 AM

Quote:

Originally Posted by obobskivich

EDIT with solution:

It's better if you post solutions as a follow-up post, because:

1) it removes the thread from the list of "Zero Reply Threads".
2) it causes anyone who might have subscribed to get notified (which editing doesn't do).

obobskivich · 06-02-2021, 03:53 PM

I did not know that.

Thanks for the tip.

mrmazda · 06-05-2021, 01:38 AM

I must not be understanding your goal. For quite some time now, the default with multiple displays is to position each side by side with the primary display the left-most, as an extended desktop, a single surface with no seams. IOW, no xrandr or xorg.con* is needed to produce this arrangement by default:

Code:

# hwinfo --monitor | grep Model
  Model: "DELL U2913WM"
  Model: "NEC EA243WM"
  Model: "K272HUL"
# inxi -Gay
Graphics:
  Device-1: Intel HD Graphics 630 vendor: Gigabyte driver: i915 v: kernel
  bus-ID: 00:02.0 chip-ID: 8086:5912 class-ID: 0300
  Display: server: X.Org 1.20.3 driver: loaded: modesetting
  unloaded: fbdev,vesa alternate: intel display-ID: :0 screens: 1
  Screen-1: 0 s-res: 7040x1440 s-dpi: 96 s-size: 1490x304mm (58.7x12.0") s-diag: 1521mm (59.9")
  Monitor-1: HDMI-1 res: 2560x1080 hz: 60 dpi: 97 size: 673x284mm (26.5x11.2") diag: 730mm (28.8")
  Monitor-2: HDMI-2 res: 1920x1200 hz: 60 dpi: 94 size: 519x324mm (20.4x12.8") diag: 612mm (24.1")
  Monitor-3: DP-1 res: 2560x1440 hz: 60 dpi: 109 size: 598x336mm (23.5x13.2") diag: 686mm (27")
  OpenGL: renderer: Mesa DRI Intel HD Graphics 630 (KBL GT2)
  v: 4.6 Mesa 20.2.4 compat-v: 3.0 direct render: Yes
# xrandr | egrep 'onnect|creen|\*' | grep -v disconn | sort -r
Screen 0: minimum 320 x 200, current 7040 x 1440, maximum 16384 x 16384
HDMI-2 connected 1920x1200+2560+0 (normal left inverted right x axis y axis) 519mm x 324mm
HDMI-1 connected 2560x1080+0+0 (normal left inverted right x axis y axis) 673mm x 284mm
DP-1 connected primary 2560x1440+4480+0 (normal left inverted right x axis y axis) 598mm x 336mm
   2560x1440     59.95*+  74.92
   2560x1080     60.00*+
   1920x1200     59.95*+

Normally with these three displays I stack them with largest at the bottom:

Code:

# xrandr --output DP-1 --primary --output HDMI-1 --above DP-1 --output HDMI-2 --above HDMI-1
# inxi -Gay
Graphics:
  Device-1: Intel HD Graphics 630 vendor: Gigabyte driver: i915 v: kernel
  bus-ID: 00:02.0 chip-ID: 8086:5912 class-ID: 0300
  Display: server: X.Org 1.20.3 driver: loaded: modesetting
  unloaded: fbdev,vesa alternate: intel display-ID: :0 screens: 1
  Screen-1: 0 s-res: 2560x3720 s-dpi: 96 s-size: 677x984mm (26.7x38.7") s-diag: 1194mm (47")
  Monitor-1: HDMI-1 res: 2560x1080 hz: 60 dpi: 97 size: 673x284mm (26.5x11.2") diag: 730mm (28.8")
  Monitor-2: HDMI-2 res: 1920x1200 hz: 60 dpi: 94 size: 519x324mm (20.4x12.8") diag: 612mm (24.1")
  Monitor-3: DP-1 res: 2560x1440 hz: 60 dpi: 109 size: 598x336mm (23.5x13.2") diag: 686mm (27")
  OpenGL: renderer: Mesa DRI Intel HD Graphics 630 (KBL GT2)
  v: 4.6 Mesa 20.2.4 compat-v: 3.0 direct render: Yes
# xrandr | egrep 'onnect|creen|\*' | grep -v disconn | sort -r
Screen 0: minimum 320 x 200, current 2560 x 3720, maximum 16384 x 16384
HDMI-2 connected 1920x1200+0+0 (normal left inverted right x axis y axis) 519mm x 324mm
HDMI-1 connected 2560x1080+0+1200 (normal left inverted right x axis y axis) 673mm x 284mm
DP-1 connected primary 2560x1440+0+2280 (normal left inverted right x axis y axis) 598mm x 336mm
   2560x1440     59.95*+  74.92
   2560x1080     60.00*+
   1920x1200     59.95*+

If I want largest resolution to left, and smallest to right:

Code:

# xrandr --output HDMI-1 --right-of DP-1 --output HDMI-2 --right-of HDMI-1
# inxi -Gay
Graphics:
  Device-1: Intel HD Graphics 630 vendor: Gigabyte driver: i915 v: kernel
  bus-ID: 00:02.0 chip-ID: 8086:5912 class-ID: 0300
  Display: server: X.Org 1.20.3 driver: loaded: modesetting
  unloaded: fbdev,vesa alternate: intel display-ID: :0 screens: 1
  Screen-1: 0 s-res: 7040x1440 s-dpi: 96 s-size: 1862x380mm (73.3x15.0")
  s-diag: 1900mm (74.8")
  Monitor-1: HDMI-1 res: 2560x1080 hz: 60 dpi: 97 size: 673x284mm (26.5x11.2") diag: 730mm (28.8")
  Monitor-2: HDMI-2 res: 1920x1200 hz: 60 dpi: 94 size: 519x324mm (20.4x12.8") diag: 612mm (24.1")
  Monitor-3: DP-1 res: 2560x1440 hz: 60 dpi: 109 size: 598x336mm (23.5x13.2") diag: 686mm (27")
  OpenGL: renderer: Mesa DRI Intel HD Graphics 630 (KBL GT2)
  v: 4.6 Mesa 20.2.4 compat-v: 3.0 direct render: Yes
# xrandr | egrep 'onnect|creen|\*' | grep -v disconn | sort -r
Screen 0: minimum 320 x 200, current 7040 x 1440, maximum 16384 x 16384
HDMI-2 connected 1920x1200+5120+0 (normal left inverted right x axis y axis) 519mm x 324mm
HDMI-1 connected 2560x1080+2560+0 (normal left inverted right x axis y axis) 673mm x 284mm
DP-1 connected primary 2560x1440+0+0 (normal left inverted right x axis y axis) 598mm x 336mm
   2560x1440     59.95*+  74.92
   2560x1080     60.00*+
   1920x1200     59.95*+

obobskivich · 06-08-2021, 03:26 PM

Quote:

Originally Posted by mrmazda

I must not be understanding your goal. For quite some time now, the default with multiple displays is to position each side by side with the primary display the left-most, as an extended desktop, a single surface with no seams. IOW, no xrandr or xorg.con* is needed to produce this arrangement by default:[code]# hwinfo

That's a 'typical configuration' for these displays as well (they're all identical in this case but still run as extended displays), the goal here is to create a single virtual display with a resolution equal to the combined resolution of all three involved displays, so instead of 3x1920x1080 it becomes 5760x1080. 'But why?' because it means applications can be full-screen'd across the entirety of it.

mrmazda · 06-08-2021, 08:02 PM

Quote:

Originally Posted by obobskivich

it means applications can be full-screen'd across the entirety of it.

That's what

Quote:

current 7040 x 1440

and

Quote:

current 2560 x 3720

in post #4 mean.