snowcap: Add closed signal

Author: Ottatop

snowcap/api/lua/snowcap/widget/signal.lua

@@ -6,6 +6,10 @@
 ---
 ---@enum snowcap.widget.signal
 return {
+    ---Notifies that a redraw is needed.
     redraw_needed = "widget::redraw_needed",
+    ---Emits a message that will update widgets.
     send_message = "widget::send_message",
+    ---Notifies that a widget closed.
+    closed = "widget::closed",
 }

snowcap/api/rust/src/widget/signal.rs

@@ -29,3 +29,9 @@ impl<Msg> From<Msg> for Message<Msg> {
 }
 
 impl<Msg: Clone + 'static> Signal for Message<Msg> {}
+
+/// Notifies that a widget closed.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct Closed;
+
+impl Signal for Closed {}