xwayland: Expose DISPLAY variable to clients

src/session.rs

@@ -77,6 +77,9 @@ pub fn setup_socket(handle: LoopHandle<Data>, state: &State) -> Result<()> {
                     .into_string()
                     .map_err(|_| anyhow!("wayland socket is no valid utf-8 string?"))?,
             );
+            if let Some(display) = state.common.xwayland_state.values().find_map(|s| s.display) {
+                env.insert(String::from("DISPLAY"), format!(":{}", display));
+            }
             let message = serde_json::to_string(&Message::SetEnv { variables: env })
                 .with_context(|| "Failed to encode environment variables into json")?;
             let bytes = message.into_bytes();