gtk: detect if Audio is availble

qemu-display-listener/Cargo.toml

@@ -8,7 +8,7 @@ edition = "2018"
 
 [dependencies]
 derivative = "2.2.0"
-zbus = "2.0.0-beta"
+zbus = { version = "2.0.0-beta", features = ["xml"] }
 zvariant = { version = "2.4.0", features = ["serde_bytes"] }
 libc = "0.2.86"
 glib = { git = "https://github.com/gtk-rs/gtk-rs", optional = true }

qemu-display-listener/src/audio.rs

@@ -3,6 +3,7 @@ use std::os::unix::net::UnixStream;
 use std::sync::mpsc::{self, Receiver, SendError};
 use std::sync::Arc;
 use std::{os::unix::io::AsRawFd, thread};
+use std::str::FromStr;
 
 use zbus::{dbus_interface, dbus_proxy, export::zvariant::Fd};
 
@@ -234,6 +235,14 @@ impl Audio {
         Ok(Self { proxy })
     }
 
+    pub fn available(conn: &zbus::Connection) -> bool {
+        // TODO: we may want to generalize interface detection
+        let ip = zbus::fdo::IntrospectableProxy::new_for(&conn, "org.qemu", "/org/qemu/Display1").unwrap();
+        let introspect = zbus::xml::Node::from_str(&ip.introspect().unwrap()).unwrap();
+        let has_audio = introspect.nodes().iter().any(|n| n.name().map(|n| n == "Audio").unwrap_or(false));
+        has_audio
+    }
+
     pub fn listen_out(&self) -> Result<Receiver<AudioOutEvent>> {
         let (p0, p1) = UnixStream::pair()?;
         let (tx, rx) = mpsc::channel();

qemu-gtk4/src/application.rs

@@ -96,11 +96,14 @@ mod imp {
             }
             .expect("Failed to connect to DBus");
 
-            if let Ok(audio) = Audio::new(&conn) {
-                self.audio
-                    .set(GstAudio::new(audio).expect("Failed to setup audio"))
-                    .expect("Audio already set");
+            if Audio::available(&conn) {
+                if let Ok(audio) = Audio::new(&conn) {
+                    self.audio
+                        .set(GstAudio::new(audio).expect("Failed to setup audio"))
+                        .unwrap();
+                }
             }
+
             let console = Console::new(&conn, 0).expect("Failed to get the console");
             self.conn.set(conn).expect("Connection already set.");