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GNOME and Wayland

My articles:

GNOME

GNOME desktop made of multiple components:

  • Mutter: compositor supportting Xorg and Wayland, use Clutter library
  • libinput: library that provides a full input stack for display servers and other applications that need to handle input devices provided by the kernel. Try sudo libinput list-devices and sudo libinput debug-events commands.
  • GJS: Javascript Bindings for Gnome, use Mozilla SpiderMonkey. Provide "gjs" program which can run Javascript in the command line.
  • Xwayland: X server using Wayland compositor
  • GNOME Shell is the GNOME desktop environment. It is written in C and JavaScript as a plugin for Mutter. It's the gnome-shell program. Main features:
    • Handle inputs using libinput library
    • Wayland compositor using Mutter (as a library)
    • Run shell extensions written in Javascript using GJS (as a library)

Mutter spawns Xwayland and sets the DISPLAY environment variable which is inherited by child processes: all graphical applications started in GNOME.

Wayland

This section is unrelated to Hybrid Graphics, but useful to debug graphics issues.

Do I use Wayland?

Is "type wayland" found in the loginctl session status?

$ loginctl session-status|grep Service:
Service: gdm-password; type wayland; class user

Is WAYLAND_DISPLAY environment variable set?

$ env|grep -E '^(XDG_SESSION_TYPE|WAYLAND_DISPLAY|DISPLAY)'
XDG_SESSION_TYPE=wayland
WAYLAND_DISPLAY=wayland-0
DISPLAY=:0

Is Xwayland running?

$ ps ax|grep Xwayland
 1956 tty2     Sl+    6:38 /usr/bin/Xwayland :0 ...

In GNOME Shell, Mutter spawns Xwayland and sets the DISPLAY environment variable which is inherited by child processes: all graphical applications started in GNOME.

Is this application using Wayland or Xorg?

xprop or xwininfo program can be in Wayland to check if an application is using Xorg or Wayland: the mouse cursor becomes a cross only and only if the application is used Xorg (X11 API).

xlsclients command lists programs using XWayland.

Opt-in for Wayland

To opt-in for Wayland support in Firefox and Thunderbird, set MOZ_ENABLE_WAYLAND=1 environment variable.

For example, I put the following line into /etc/environment to run Firefox with Wayland:

MOZ_ENABLE_WAYLAND=1

When a Wayland compositor is running, Gtk applications prefer Wayland by default. In that case, you can opt-in for X11 by seting GDK_BACKEND=x11 environment variable.

Wayland and Xorg

Debug: https://fedoraproject.org/wiki/How_to_debug_Wayland_problems

See also: https://fedoraproject.org/wiki/How_to_debug_Firefox_problems

Environment to opt-in for Wayland support:

export GDK_BACKEND=wayland

To run Firefow with Firefox, edit /etc/environment to add the line:

MOZ_ENABLE_WAYLAND=1

Get GPUs:

$ lspci|grep VGA
00:02.0 VGA compatible controller: Intel Corporation HD Graphics 530 (rev 06)
01:00.0 VGA compatible controller: NVIDIA Corporation GM107GLM [Quadro M1000M] (rev a2)

Get OpenGL GPU:

$ glxinfo|grep -E 'Device|rendering'
direct rendering: Yes
    Device: Mesa DRI Intel(R) HD Graphics 530 (Skylake GT2)  (0x191b)

Get screen resolution:

$ xrandr
Screen 0: minimum 320 x 200, current 3840 x 1080, maximum 8192 x 8192
XWAYLAND0 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 510mm x 290mm
   1920x1080     59.96*+
XWAYLAND1 connected 1920x1080+1920+0 (normal left inverted right x axis y axis) 480mm x 270mm
   1920x1080     59.96*+

Get screen DPI (96x96 in this example):

$ xdpyinfo | grep -B 2 resolution
screen #0:
  dimensions:    3840x1080 pixels (1016x286 millimeters)
  resolution:    96x96 dots per inch

Check if an application is using Xorg or Wayland in Wayland: run xprop, the mouse cursor becomes a cross only for Xorg appplications.

Hybrid Graphics (2 GPUs)

Disable Nouveau driver:

sudo grubby --update-kernel=ALL --args="modprobe.blacklist=nouveau"

Fedora 30, add an argument to all GRUB kernel configurations:

sudo grubby --update-kernel=ALL --args="xdg.force_integrated=0"

Disable switcheroo-control (don't run it anymore at startup):

sudo systemctl stop switcheroo-control.service
sudo systemctl disable switcheroo-control.service

My Lenovo P50 has 2 GPU, one slow integrated Intel GPU and one fast Nvidia GPU. There is a switcheroo-control D-Bus service to check if the system has 2 GPUs.

Linux kernel vgaswitcheroo:

$ sudo cat /sys/kernel/debug/vgaswitcheroo/switch
0:IGD:+:Pwr:0000:00:02.0
1:DIS: :DynPwr:0000:01:00.0
  • IGD: Integrated Graphics Device
  • DIS: DIScrete graphics device
  • "+": active card

Links:

DBus:

gdbus introspect --system --dest net.hadess.SwitcherooControl --object-path /net/hadess/SwitcherooControl
...
interface net.hadess.SwitcherooControl {
  ...
  properties:
    readonly b HasDualGpu = true;
};

See bumblebee.

Launch an application with Nvidia GPU from a terminal:

DRI_PRIME=1 firefox

Firefox:

  • Go to about:support and search for the Graphics section

  • WebGL https://webglreport.com/

    Unmasked Vendor: nouveau
    Unmasked Renderer: NV117
    

Xorg BadWindow issue

Set GDK_SYNCHRONIZE environment variable to debug such issue:

The program 'gnome-shell' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadWindow (invalid Window parameter)'.
  (Details: serial 352312 error_code 3 request_code 18 (core protocol) minor_code 0)
  (Note to programmers: normally, X errors are reported asynchronously;
   that is, you will receive the error a while after causing it.
   To debug your program, run it with the GDK_SYNCHRONIZE environment
   variable to change this behavior. You can then get a meaningful
   backtrace from your debugger if you break on the gdk_x_error() function.)
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