1 files changed, 170 insertions, 0 deletions
diff --git a/native/src/overlay/element.rs b/native/src/overlay/element.rs
new file mode 100644
index 00000000..e1fd9b88
--- /dev/null
+++ b/native/src/overlay/element.rs
@@ -0,0 +1,170 @@
+pub use crate::Overlay;
+
+use crate::{layout, Clipboard, Event, Hasher, Layout, Point, Size, Vector};
+
+/// A generic [`Overlay`].
+///
+/// [`Overlay`]: trait.Overlay.html
+#[allow(missing_debug_implementations)]
+pub struct Element<'a, Message, Renderer> {
+    position: Point,
+    overlay: Box<dyn Overlay<Message, Renderer> + 'a>,
+}
+
+impl<'a, Message, Renderer> Element<'a, Message, Renderer>
+where
+    Renderer: crate::Renderer,
+{
+    /// Creates a new [`Element`] containing the given [`Overlay`].
+    ///
+    /// [`Element`]: struct.Element.html
+    /// [`Overlay`]: trait.Overlay.html
+    pub fn new(
+        position: Point,
+        overlay: Box<dyn Overlay<Message, Renderer> + 'a>,
+    ) -> Self {
+        Self { position, overlay }
+    }
+
+    /// Translates the [`Element`].
+    ///
+    /// [`Element`]: struct.Element.html
+    pub fn translate(mut self, translation: Vector) -> Self {
+        self.position = self.position + translation;
+        self
+    }
+
+    /// Applies a transformation to the produced message of the [`Element`].
+    ///
+    /// [`Element`]: struct.Element.html
+    pub fn map<B>(self, f: &'a dyn Fn(Message) -> B) -> Element<'a, B, Renderer>
+    where
+        Message: 'a,
+        Renderer: 'a,
+        B: 'static,
+    {
+        Element {
+            position: self.position,
+            overlay: Box::new(Map::new(self.overlay, f)),
+        }
+    }
+
+    /// Computes the layout of the [`Element`] in the given bounds.
+    ///
+    /// [`Element`]: struct.Element.html
+    pub fn layout(&self, renderer: &Renderer, bounds: Size) -> layout::Node {
+        self.overlay.layout(renderer, bounds, self.position)
+    }
+
+    /// Processes a runtime [`Event`].
+    ///
+    /// [`Event`]: enum.Event.html
+    pub fn on_event(
+        &mut self,
+        event: Event,
+        layout: Layout<'_>,
+        cursor_position: Point,
+        messages: &mut Vec<Message>,
+        renderer: &Renderer,
+        clipboard: Option<&dyn Clipboard>,
+    ) {
+        self.overlay.on_event(
+            event,
+            layout,
+            cursor_position,
+            messages,
+            renderer,
+            clipboard,
+        )
+    }
+
+    /// Draws the [`Element`] and its children using the given [`Layout`].
+    ///
+    /// [`Element`]: struct.Element.html
+    /// [`Layout`]: layout/struct.Layout.html
+    pub fn draw(
+        &self,
+        renderer: &mut Renderer,
+        defaults: &Renderer::Defaults,
+        layout: Layout<'_>,
+        cursor_position: Point,
+    ) -> Renderer::Output {
+        self.overlay
+            .draw(renderer, defaults, layout, cursor_position)
+    }
+
+    /// Computes the _layout_ hash of the [`Element`].
+    ///
+    /// [`Element`]: struct.Element.html
+    pub fn hash_layout(&self, state: &mut Hasher) {
+        self.overlay.hash_layout(state, self.position);
+    }
+}
+
+struct Map<'a, A, B, Renderer> {
+    content: Box<dyn Overlay<A, Renderer> + 'a>,
+    mapper: &'a dyn Fn(A) -> B,
+}
+
+impl<'a, A, B, Renderer> Map<'a, A, B, Renderer> {
+    pub fn new(
+        content: Box<dyn Overlay<A, Renderer> + 'a>,
+        mapper: &'a dyn Fn(A) -> B,
+    ) -> Map<'a, A, B, Renderer> {
+        Map { content, mapper }
+    }
+}
+
+impl<'a, A, B, Renderer> Overlay<B, Renderer> for Map<'a, A, B, Renderer>
+where
+    Renderer: crate::Renderer,
+{
+    fn layout(
+        &self,
+        renderer: &Renderer,
+        bounds: Size,
+        position: Point,
+    ) -> layout::Node {
+        self.content.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.content.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.content
+            .draw(renderer, defaults, layout, cursor_position)
+    }
+
+    fn hash_layout(&self, state: &mut Hasher, position: Point) {
+        self.content.hash_layout(state, position);
+    }
+}