Draft ComboBox and Menu layer

native/src/overlay.rs

@@ -1,4 +1,5 @@
 use crate::{layout, Clipboard, Event, Hasher, Layer, Layout, Point, Size};
+use std::rc::Rc;
 
 #[allow(missing_debug_implementations)]
 pub struct Overlay<'a, Message, Renderer> {
@@ -17,6 +18,18 @@ where
         Self { position, layer }
     }
 
+    pub fn map<B>(self, f: Rc<dyn Fn(Message) -> B>) -> Overlay<'a, B, Renderer>
+    where
+        Message: 'static,
+        Renderer: 'a,
+        B: 'static,
+    {
+        Overlay {
+            position: self.position,
+            layer: Box::new(Map::new(self.layer, f)),
+        }
+    }
+
     pub fn layout(&self, renderer: &Renderer, bounds: Size) -> layout::Node {
         self.layer.layout(renderer, bounds, self.position)
     }
@@ -37,12 +50,87 @@ where
 
     pub fn on_event(
         &mut self,
-        _event: Event,
-        _layout: Layout<'_>,
-        _cursor_position: Point,
-        _messages: &mut Vec<Message>,
-        _renderer: &Renderer,
-        _clipboard: Option<&dyn Clipboard>,
+        event: Event,
+        layout: Layout<'_>,
+        cursor_position: Point,
+        messages: &mut Vec<Message>,
+        renderer: &Renderer,
+        clipboard: Option<&dyn Clipboard>,
     ) {
+        self.layer.on_event(
+            event,
+            layout,
+            cursor_position,
+            messages,
+            renderer,
+            clipboard,
+        )
+    }
+}
+
+struct Map<'a, A, B, Renderer> {
+    layer: Box<dyn Layer<A, Renderer> + 'a>,
+    mapper: Rc<dyn Fn(A) -> B>,
+}
+
+impl<'a, A, B, Renderer> Map<'a, A, B, Renderer> {
+    pub fn new(
+        layer: Box<dyn Layer<A, Renderer> + 'a>,
+        mapper: Rc<dyn Fn(A) -> B + 'static>,
+    ) -> Map<'a, A, B, Renderer> {
+        Map { layer, mapper }
+    }
+}
+
+impl<'a, A, B, Renderer> Layer<B, Renderer> for Map<'a, A, B, Renderer>
+where
+    Renderer: crate::Renderer,
+{
+    fn layout(
+        &self,
+        renderer: &Renderer,
+        bounds: Size,
+        position: Point,
+    ) -> layout::Node {
+        self.layer.layout(renderer, bounds, position)
+    }
+
+    fn on_event(
+        &mut self,
+        event: Event,
+        layout: Layout<'_>,
+        cursor_position: Point,
+        messages: &mut Vec<B>,
+        renderer: &Renderer,
+        clipboard: Option<&dyn Clipboard>,
+    ) {
+        let mut original_messages = Vec::new();
+
+        self.layer.on_event(
+            event,
+            layout,
+            cursor_position,
+            &mut original_messages,
+            renderer,
+            clipboard,
+        );
+
+        original_messages
+            .drain(..)
+            .for_each(|message| messages.push((self.mapper)(message)));
+    }
+
+    fn draw(
+        &self,
+        renderer: &mut Renderer,
+        defaults: &Renderer::Defaults,
+        layout: Layout<'_>,
+        cursor_position: Point,
+    ) -> Renderer::Output {
+        self.layer.draw(renderer, defaults, layout, cursor_position)
+    }
+
+    fn hash_layout(&self, state: &mut Hasher, position: Point) {
+        self.layer.hash_layout(state, position);
     }
 }