Render to multiple X Screens

support
1

I am writing an application (NVIDIA RTX5000, Ubuntu 20.04) which requires low latency (camera to screen).
I created an xorg configuration which defines each physical monitor as a separate x screen.
#nvidia-settings: X configuration file generated by nvidia-settings
#nvidia-settings: version 455.32.00

Section "ServerLayout"
Identifier     "X.org Configured"
Screen      0  "Screen0" 0 0
Screen      1  "Screen1" RightOf "Screen0"
InputDevice    "Mouse0" "CorePointer"
InputDevice    "Keyboard0" "CoreKeyboard"
Option         "Xinerama" "0"
EndSection

Section "Files"
ModulePath      "/usr/lib/xorg/modules"
FontPath        "/usr/share/fonts/X11/misc"
FontPath        "/usr/share/fonts/X11/cyrillic"
FontPath        "/usr/share/fonts/X11/100dpi/:unscaled"
FontPath        "/usr/share/fonts/X11/75dpi/:unscaled"
FontPath        "/usr/share/fonts/X11/Type1"
FontPath        "/usr/share/fonts/X11/100dpi"
FontPath        "/usr/share/fonts/X11/75dpi"
FontPath        "built-ins"
EndSection

Section "Module"
Load           "glx"
Load           "extmod"    
EndSection

Section "InputDevice"
Identifier     "Keyboard0"
Driver         "kbd"
EndSection

Section "InputDevice"
Identifier     "Mouse0"
Driver         "mouse"
Option         "Protocol" "auto"
Option         "Device" "/dev/input/mice"
Option         "ZAxisMapping" "4 5 6 7"
EndSection

Section "Monitor"
Identifier     "Monitor0"
VendorName     "Unknown"
ModelName      "DELL P2419H"
HorizSync       30.0 - 83.0
VertRefresh     56.0 - 76.0
EndSection

Section "Monitor"
Identifier     "Monitor1"
VendorName     "Unknown"
ModelName      "DELL U2718Q"
HorizSync       10.0 - 137.0
VertRefresh     49.0 - 86.0
EndSection

Section "Device"
Identifier     "Device0"
Driver         "nvidia"
VendorName     "NVIDIA Corporation"
BoardName      "Quadro RTX 5000"
BusID          "PCI:101:0:0"
Screen          0
Option "ZaphodHeads" "DFP-4"    
EndSection

Section "Device"
Identifier     "Device1"
Driver         "nvidia"
VendorName     "NVIDIA Corporation"
BoardName      "Quadro RTX 5000"
BusID          "PCI:101:0:0"
Screen          1
Option "ZaphodHeads" "DFP-3"
EndSection

Section "Screen"
Identifier     "Screen0"
Device         "Device0"
Monitor        "Monitor0"
SubSection     "Display"
    Depth       24
EndSubSection
EndSection

 Section "Screen"
Identifier     "Screen1"
Device         "Device1"
Monitor        "Monitor1"
SubSection     "Display"
    Depth       24
EndSubSection
EndSection

When I run the glfwGetMonitors function I only get 1 monitor, which I understand is only from the default x-server.
Is there any way to access/open multiple windows with such an xorg configuration?

2

This is very similar to the previous post:

From the documentation on GLFW: Standards conformance

GLFW uses the XRandR 1.3 extension to provide multi-monitor support. If the running X server does not support this version of this extension, multi-monitor support will not function and only a single, desktop-spanning monitor will be reported.

It seems the first step is to remove your xorg.conf file so XRandR can manage the screens.

3

How is it possible to define each physical monitor on a separate X-Screen without an xorg.conf file. The default is always one x screen for all physical displays

4

The configuration is now mostly handled with XRandR:
https://www.x.org/releases/X11R7.5/doc/man/man1/xrandr.1.html

I’ve not got multiple displays on my Linux setups, so haven’t used this but I believe the --screen option is used to configure each X Screen.

5

In case that is useful, I opened an issue here, maybe there will be some answer later on useful to you @ShacharDev

6

Thanks @dougbinks & @marianne .