wip: refactor pt.29: 12 errors

crates/tek_core/src/engine.rs

@@ -122,6 +122,21 @@ impl<E: Engine, W: Widget<Engine = E>> Widget for Option<W> {
         self.as_ref().map(|widget|widget.render(to)).unwrap_or(Ok(()))
     }
 }
+/// Render either of two widgets depending on predicate
+pub struct Either<E: Engine, A: Widget<Engine = E>, B: Widget<Engine = E>>(
+    pub bool,
+    pub A,
+    pub B,
+);
+impl<E: Engine, A: Widget<Engine = E>, B: Widget<Engine = E>> Widget for Either<E, A, B> {
+    type Engine = E;
+    fn layout (&self, to: E::Size) -> Perhaps<E::Size> {
+        if self.0 { self.1.layout(to) } else { self.2.layout(to) }
+    }
+    fn render (&self, to: &mut E::Output) -> Usually<()> {
+        if self.0 { self.1.render(to) } else { self.2.render(to) }
+    }
+}
 /// A custom [Widget] defined by passing layout and render closures in place.
 pub struct CustomWidget<
     E: Engine,