X11 and wayland

Origin link 2023-4-22

see Environment variables for Wayland hackers and Wayland-specific environment variables for detail and what is setting in wsl2.

WAYLAND_DISPLAY

wayland unix socket
WAYLAND_DISPLAY=wayland-0

XDG_RUNTIME_DIR

directory of wayland unix socket
XDG_RUNTIME_DIR=/mnt/wslg/runtime-dir/ or XDG_RUNTIME_DIR=/run/user/1000/

DISPLAY

X11 unix socket
DISPLAY=:0 and /tmp/.X11-unix/X0

GDK_BACKEND

it is better to set according to GTK backend selection, or why GTK cannot open display: :0
If the special value of help is used, a GTK application will print the possible values it knows. see link.

gtk3/gtk3 in conda has disabled wayland support, see link.

with pygobject, GDK_BACKEND=wayland doesn't work but chrome/weston-terminal is OK and pygobject is OK with GDK_BACKEND=wayland, x11 or GDK_BACKEND=x11.
with GDK_BACKEND=help, gtk3 only support x11, not wayland
condas gtk3.0/gtk4.0 only support x11, not wayland since no ~/miniconda3/envs/gtk/include/gtk-3.0/gdk/gdkwayland.h.

(gtk) hongy19@WSL cairo$ GDK_BACKEND=help python test1.py

Supported GDK backends: x11