Make sure starting listenvars is idempodent (fixes #360)

crates/eww/src/app.rs

@@ -332,7 +332,8 @@ impl App {
             let mut eww_window = initialize_window(monitor_geometry, root_widget, window_def, window_scope)?;
             eww_window.gtk_window.style_context().add_class(&window_name.to_string());
 
-            // initialize script var handlers for variables that where not used before opening this window.
+            // initialize script var handlers for variables. As starting a scriptvar with the script_var_handler is idempodent,
+            // we can just start script vars that are already running without causing issues
             // TODO maybe this could be handled by having a track_newly_used_variables function in the scope tree?
             for used_var in self.scope_graph.borrow().variables_used_in_self_or_subscopes_of(eww_window.scope_index) {
                 if let Ok(script_var) = self.eww_config.get_script_var(&used_var) {
@@ -348,9 +349,8 @@ impl App {
                     // Generally, this should get disconnected before the gtk window gets destroyed.
                     // It serves as a fallback for when the window is closed manually.
                     let (response_sender, _) = daemon_response::create_pair();
-                    if let Err(err) = app_evt_sender
+                    let command = DaemonCommand::CloseWindows { windows: vec![window_name.clone()], sender: response_sender };
-                        .send(DaemonCommand::CloseWindows { windows: vec![window_name.clone()], sender: response_sender })
+                    if let Err(err) = app_evt_sender.send(command) {
-                    {
                         log::error!("Error sending close window command to daemon after gtk window destroy event: {}", err);
                     }
                 }

crates/eww/src/script_var_handler.rs

@@ -61,6 +61,8 @@ pub struct ScriptVarHandlerHandle {
 
 impl ScriptVarHandlerHandle {
     /// Add a new script-var that should be executed.
+    /// This is idempodent, meaning that running a definition that already has a script_var attached which is running
+    /// won't do anything.
     pub fn add(&self, script_var: ScriptVarDefinition) {
         crate::print_result_err!(
             "while forwarding instruction to script-var handler",
@@ -204,8 +206,16 @@ impl ListenVarHandler {
         Ok(handler)
     }
 
+    /// Start a listen-var. Starting a variable that is already running will not do anything.
     async fn start(&mut self, var: ListenScriptVar) {
         log::debug!("starting listen-var {}", &var.name);
+
+        // Make sure the same listenvar is never started twice,
+        // as that would cause eww to not clean up the older listenvar on window close.
+        if self.listen_process_handles.contains_key(&var.name) {
+            return;
+        }
+
         let cancellation_token = CancellationToken::new();
         self.listen_process_handles.insert(var.name.clone(), cancellation_token.clone());
 
@@ -264,7 +274,7 @@ async fn terminate_handle(mut child: tokio::process::Child) {
     if let Some(id) = child.id() {
         let _ = signal::killpg(Pid::from_raw(id as i32), signal::SIGTERM);
         tokio::select! {
-            _ = child.wait() => {},
+            _ = child.wait() => { },
             _ = tokio::time::sleep(std::time::Duration::from_secs(10)) => {
                 let _ = child.kill().await;
             }