Use nested for lazy widgets

runtime/src/lib.rs

@@ -47,6 +47,7 @@ pub mod clipboard;
 pub mod command;
 pub mod font;
 pub mod keyboard;
+pub mod overlay;
 pub mod program;
 pub mod system;
 pub mod user_interface;

runtime/src/overlay.rs

@@ -0,0 +1,4 @@
+//! Overlays for user interfaces.
+mod nested;
+
+pub use nested::Nested;

runtime/src/overlay/nested.rs

@@ -21,6 +21,12 @@ where
         Self { overlay: element }
     }
 
+    /// Returns the position of the [`Nested`] overlay.
+    pub fn position(&self) -> Point {
+        self.overlay.position()
+    }
+
+    /// Returns the layout [`Node`] of the [`Nested`] overlay.
     pub fn layout(
         &mut self,
         renderer: &Renderer,
@@ -36,7 +42,7 @@ where
         where
             Renderer: renderer::Renderer,
         {
-            let translation = position - Point::ORIGIN;
+            let translation = position - element.position();
 
             let node = element.layout(renderer, bounds, translation);
 
@@ -58,6 +64,7 @@ where
         recurse(&mut self.overlay, renderer, bounds, position)
     }
 
+    /// Draws the [`Nested`] overlay using the associated `Renderer`.
     pub fn draw(
         &mut self,
         renderer: &mut Renderer,
@@ -127,6 +134,7 @@ where
         recurse(&mut self.overlay, layout, renderer, theme, style, cursor);
     }
 
+    /// Applies a [`widget::Operation`] to the [`Nested`] overlay.
     pub fn operate(
         &mut self,
         layout: Layout<'_>,
@@ -157,6 +165,7 @@ where
         recurse(&mut self.overlay, layout, renderer, operation)
     }
 
+    /// Processes a runtime [`Event`].
     pub fn on_event(
         &mut self,
         event: Event,
@@ -247,6 +256,7 @@ where
         status
     }
 
+    /// Returns the current [`mouse::Interaction`] of the [`Nested`] overlay.
     pub fn mouse_interaction(
         &mut self,
         layout: Layout<'_>,
@@ -298,6 +308,7 @@ where
             .unwrap_or_default()
     }
 
+    /// Returns true if the cursor is over the [`Nested`] overlay.
     pub fn is_over(
         &mut self,
         layout: Layout<'_>,

runtime/src/user_interface.rs

@@ -1,14 +1,12 @@
 //! Implement your own event loop to drive a user interface.
-mod overlay;
-
 use crate::core::event::{self, Event};
 use crate::core::layout;
 use crate::core::mouse;
 use crate::core::renderer;
 use crate::core::widget;
 use crate::core::window;
-use crate::core::{Clipboard, Point, Rectangle, Size};
-use crate::core::{Element, Layout, Shell};
+use crate::core::{Clipboard, Element, Layout, Point, Rectangle, Shell, Size};
+use crate::overlay;
 
 /// A set of interactive graphical elements with a specific [`Layout`].
 ///