add CustomWidget and use it to remove more one-time components

crates/tek_core/src/engine.rs

@@ -183,6 +183,36 @@ pub trait ContentComponent<E: Engine>: Widget<Engine = E> + Handle<E> {}
 /// Everything that implements [Render] and [Handle] is a [Component].
 impl<E: Engine, C: Content<Engine = E> + Handle<E>> ContentComponent<E> for C {}
 
+pub struct CustomWidget<
+    E: Engine,
+    L: Send + Sync + Fn(E::Size)->Perhaps<E::Size>,
+    R: Send + Sync + Fn(&mut E::Output)->Usually<()>
+>(L, R, PhantomData<E>);
+
+impl<
+    E: Engine,
+    L: Send + Sync + Fn(E::Size)->Perhaps<E::Size>,
+    R: Send + Sync + Fn(&mut E::Output)->Usually<()>
+> CustomWidget<E, L, R> {
+    pub fn new (layout: L, render: R) -> Self {
+        Self(layout, render, Default::default())
+    }
+}
+impl<
+    E: Engine,
+    L: Send + Sync + Fn(E::Size)->Perhaps<E::Size>,
+    R: Send + Sync + Fn(&mut E::Output)->Usually<()>
+> Widget for CustomWidget<E, L, R> {
+    type Engine = E;
+    fn layout (&self, to: E::Size) -> Perhaps<E::Size> {
+        self.0(to)
+    }
+    fn render (&self, to: &mut E::Output) -> Usually<()> {
+        self.1(to)
+    }
+}
+
+
 pub trait Exit: Send {
     fn exited (&self) -> bool;
     fn exit (&mut self);