dummysigner: add low level exit handling

- do not rely on iced close_on_exit
- listen to window event and ctrl-c signal to exit
- drop any connection on exit

close revault#278

contrib/tools/dummysigner/src/app.rs

@@ -80,6 +80,7 @@ impl Application for App {
         match message {
             Message::CtrlC | Message::Event(Event::Window(window::Event::CloseRequested)) => {
                 self.exit = true;
+                self.status = AppStatus::Waiting {};
                 Command::none()
             }
             Message::Server(server::ServerMessage::NewConnection(addr, writer)) => {
@@ -125,7 +126,8 @@ impl Application for App {
                 }
                 Command::none()
             }
-            Message::Server(server::ServerMessage::ConnectionDropped) => {
+            Message::Server(server::ServerMessage::ConnectionDropped)
+            | Message::Server(server::ServerMessage::Stopped) => {
                 self.status = AppStatus::Waiting {};
                 Command::none()
             }
@@ -287,10 +289,14 @@ impl Application for App {
     }
 
     fn subscription(&self) -> iced::Subscription<Message> {
-        Subscription::batch(vec![
-            iced_native::subscription::events().map(Message::Event),
-            iced::Subscription::batch(vec![server::listen("0.0.0.0:8080").map(Message::Server)]),
-        ])
+        if !self.exit {
+            Subscription::batch(vec![
+                iced_native::subscription::events().map(Message::Event),
+                server::listen("0.0.0.0:8080").map(Message::Server),
+            ])
+        } else {
+            Subscription::none()
+        }
     }
 
     fn view(&mut self) -> Element<Message> {