Introduce Widget::overlay 🎉

native/src/overlay.rs

@@ -0,0 +1,33 @@
+use crate::{layout, Clipboard, Event, Hasher, Layout, Point};
+
+pub trait Overlay<Message, Renderer>
+where
+    Renderer: crate::Renderer,
+{
+    fn layout(
+        &self,
+        renderer: &Renderer,
+        limits: &layout::Limits,
+    ) -> layout::Node;
+
+    fn draw(
+        &self,
+        renderer: &mut Renderer,
+        defaults: &Renderer::Defaults,
+        layout: Layout<'_>,
+        cursor_position: Point,
+    ) -> Renderer::Output;
+
+    fn hash_layout(&self, state: &mut Hasher);
+
+    fn on_event(
+        &mut self,
+        _event: Event,
+        _layout: Layout<'_>,
+        _cursor_position: Point,
+        _messages: &mut Vec<Message>,
+        _renderer: &Renderer,
+        _clipboard: Option<&dyn Clipboard>,
+    ) {
+    }
+}