some more core refactor before fixing the mess

crates/tek_core/src/engine/exit.rs

@@ -0,0 +1,32 @@
+use crate::*;
+
+pub trait Exit: Send {
+    fn exited (&self) -> bool;
+    fn exit (&mut self);
+    fn boxed (self) -> Box<dyn Exit> where Self: Sized + 'static {
+        Box::new(self)
+    }
+}
+
+/// Marker trait for [Component]s that can [Exit]
+pub trait ExitableComponent<E>: Exit + Component<E> where E: Engine {
+    /// Perform type erasure for collecting heterogeneous components.
+    fn boxed (self) -> Box<dyn ExitableComponent<E>> where Self: Sized + 'static {
+        Box::new(self)
+    }
+}
+
+impl<E: Engine, C: Component<E> + Exit> ExitableComponent<E> for C {}
+
+#[macro_export] macro_rules! exit {
+    ($T:ty) => {
+        impl Exit for $T {
+            fn exited (&self) -> bool {
+                self.exited
+            }
+            fn exit (&mut self) {
+                self.exited = true
+            }
+        }
+    }
+}