X11 and wayland

 

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