ui: refactor signals

pqcli/ui/exit_view.py

@@ -6,15 +6,12 @@ from pqcli.ui.button import MenuButton
 
 
 class ExitView(urwid.Overlay):
-    def __init__(
-        self, parent: urwid.Widget, on_exit: T.Callable, on_cancel: T.Callable
-    ) -> None:
-        self.on_exit = on_exit
-        self.on_cancel = on_cancel
+    signals = ["exit", "cancel"]
 
+    def __init__(self, parent: urwid.Widget) -> None:
         question = urwid.Text(("bold", "Really quit?"), "center")
-        yes_btn = MenuButton("Yes", lambda _user_data: self.on_exit())
-        no_btn = MenuButton("No", lambda _user_data: self.on_cancel())
+        yes_btn = MenuButton("Yes", lambda _user_data: self.exit())
+        no_btn = MenuButton("No", lambda _user_data: self.cancel())
 
         line_box = urwid.LineBox(
             urwid.ListBox(
@@ -26,9 +23,15 @@ class ExitView(urwid.Overlay):
 
     def keypress(self, size: T.Any, key: str) -> T.Optional[str]:
         if key in {"y", "Y"}:
-            self.on_exit()
+            self.exit()
             return None
         if key in {"n", "N"}:
-            self.on_cancel()
+            self.cancel()
             return None
-        return super().keypress(size, key)
+        return T.cast(T.Optional[str], super().keypress(size, key))
+
+    def exit(self) -> None:
+        self._emit("exit")
+
+    def cancel(self) -> None:
+        self._emit("cancel")