app_containers: Add Wayland handling

app_containers/.local/bin/run_app_container

@@ -8,6 +8,14 @@ die() {
 [ -z "$CONTAINER_NAME" ] && die "\$CONTAINER_NAME not set"
 [ -z "$DISPLAY" ] && die "\$DISPLAY not set (you must run the script in a desktop environment"
 
+# Create a XDG_RUNTIME_DIR for guest on host
+container_xdg_runtime="$(mktemp -d)"
+trap 'rm -rf -- "$container_xdg_runtime"' EXIT
+
+# Link the current wayland session to the container's xdg runtime
+# Note that the session itself must be bind-mounted first
+ln -s /run/host/$WAYLAND_DISPLAY $container_xdg_runtime/$WAYLAND_DISPLAY
+
 # From <https://liolok.com/run-desktop-app-with-systemd-nspawn-container>
 if [[ -n $DBUS_SESSION_BUS_ADDRESS ]]; then # remove prefix
     host_bus=${DBUS_SESSION_BUS_ADDRESS#unix:path=}
@@ -21,7 +29,7 @@ else # default guess
   host_pulse=$XDG_RUNTIME_DIR/pulse
 fi
 
-# Default username
+# Default username (assume `user` always has the same uid as the host user)
 run_as=user
 homedir=/home/user
 if [ "$CONTAINER_RUN_AS_ROOT" = true ]; then
@@ -39,9 +47,15 @@ sudo systemd-nspawn -M $CONTAINER_NAME \
     `# Input devices` \
     --bind-ro=/dev/input \
     --property=DeviceAllow='char-input r' \
+    `# Xdg runtime` \
+    --bind=$container_xdg_runtime:/run/xdg \
+    --setenv=XDG_RUNTIME_DIR=/run/xdg \
     `# Xorg / Xwayland` \
     --bind-ro=/tmp/.X11-unix \
     --setenv=DISPLAY=$DISPLAY \
+    `# Wayland (note the symlink created before in xdg runtime)` \
+    --bind-ro=$XDG_RUNTIME_DIR/$WAYLAND_DISPLAY:/run/host/$WAYLAND_DISPLAY \
+    --setenv=WAYLAND_DISPLAY=$WAYLAND_DISPLAY \
     `# PulseAudio` \
     --bind-ro=$host_pulse:/run/host/pulse \
     --setenv=PULSE_SERVER=unix:/run/host/pulse/native \