Draft `Widget::overlay` idempotency

10 files changed, 134 insertions, 131 deletions

diff --git a/native/src/element.rs b/native/src/element.rs
index c881871a..b00f9e55 100644
--- a/native/src/element.rs
+++ b/native/src/element.rs
@@ -273,10 +273,10 @@ where
         self.widget.hash_layout(state);
     }
 
-    pub fn overlay(
-        &mut self,
+    pub fn overlay<'b>(
+        &'b mut self,
         layout: Layout<'_>,
-    ) -> Option<Overlay<'a, Message, Renderer>> {
+    ) -> Option<Overlay<'b, Message, Renderer>> {
         self.widget.overlay(layout)
     }
 }
@@ -366,10 +366,12 @@ where
     fn overlay(
         &mut self,
         layout: Layout<'_>,
-    ) -> Option<Overlay<'a, B, Renderer>> {
+    ) -> Option<Overlay<'_, B, Renderer>> {
+        let mapper = self.mapper.clone();
+
         self.widget
             .overlay(layout)
-            .map(|overlay| overlay.map(self.mapper.clone()))
+            .map(move |overlay| overlay.map(mapper))
     }
 }
 
@@ -450,7 +452,7 @@ where
     fn overlay(
         &mut self,
         layout: Layout<'_>,
-    ) -> Option<Overlay<'a, Message, Renderer>> {
+    ) -> Option<Overlay<'_, Message, Renderer>> {
         self.element.overlay(layout)
     }
 }
diff --git a/native/src/overlay/menu.rs b/native/src/overlay/menu.rs
index 9c180671..2a19e286 100644
--- a/native/src/overlay/menu.rs
+++ b/native/src/overlay/menu.rs
@@ -1,5 +1,5 @@
 use crate::{
-    container, layout, mouse, overlay, scrollable, Clipboard, Container,
+    container, layout, mouse, overlay, scrollable, text, Clipboard, Container,
     Element, Event, Hasher, Layout, Length, Point, Rectangle, Scrollable, Size,
     Vector, Widget,
 };
@@ -39,10 +39,10 @@ where
     pub fn new<T: 'a>(
         state: &'a mut State,
         options: impl Into<Cow<'a, [T]>>,
-        on_selected: Box<dyn Fn(T) -> Message>,
+        on_selected: &'a dyn Fn(T) -> Message,
         width: u16,
         target_height: f32,
-        text_size: u16,
+        text_size: Option<u16>,
         padding: u16,
         style: <Renderer as self::Renderer>::Style,
     ) -> Self
@@ -175,8 +175,8 @@ where
 {
     hovered_option: &'a mut Option<usize>,
     options: Cow<'a, [T]>,
-    on_selected: Box<dyn Fn(T) -> Message>,
-    text_size: u16,
+    on_selected: &'a dyn Fn(T) -> Message,
+    text_size: Option<u16>,
     padding: u16,
     style: <Renderer as self::Renderer>::Style,
 }
@@ -188,8 +188,8 @@ where
     pub fn new(
         hovered_option: &'a mut Option<usize>,
         options: impl Into<Cow<'a, [T]>>,
-        on_selected: Box<dyn Fn(T) -> Message>,
-        text_size: u16,
+        on_selected: &'a dyn Fn(T) -> Message,
+        text_size: Option<u16>,
         padding: u16,
         style: <Renderer as self::Renderer>::Style,
     ) -> Self {
@@ -221,17 +221,18 @@ where
 
     fn layout(
         &self,
-        _renderer: &Renderer,
+        renderer: &Renderer,
         limits: &layout::Limits,
     ) -> layout::Node {
         use std::f32;
 
         let limits = limits.width(Length::Fill).height(Length::Shrink);
+        let text_size = self.text_size.unwrap_or(renderer.default_size());
 
         let size = {
             let intrinsic = Size::new(
                 0.0,
-                f32::from(self.text_size + self.padding * 2)
+                f32::from(text_size + self.padding * 2)
                     * self.options.len() as f32,
             );
 
@@ -253,7 +254,7 @@ where
         layout: Layout<'_>,
         cursor_position: Point,
         messages: &mut Vec<Message>,
-        _renderer: &Renderer,
+        renderer: &Renderer,
         _clipboard: Option<&dyn Clipboard>,
     ) {
         match event {
@@ -270,11 +271,13 @@ where
             }
             Event::Mouse(mouse::Event::CursorMoved { .. }) => {
                 let bounds = layout.bounds();
+                let text_size =
+                    self.text_size.unwrap_or(renderer.default_size());
 
                 if bounds.contains(cursor_position) {
                     *self.hovered_option = Some(
                         ((cursor_position.y - bounds.y)
-                            / f32::from(self.text_size + self.padding * 2))
+                            / f32::from(text_size + self.padding * 2))
                             as usize,
                     );
                 }
@@ -296,14 +299,16 @@ where
             cursor_position,
             &self.options,
             *self.hovered_option,
-            self.text_size,
+            self.text_size.unwrap_or(renderer.default_size()),
             self.padding,
             &self.style,
         )
     }
 }
 
-pub trait Renderer: scrollable::Renderer + container::Renderer {
+pub trait Renderer:
+    scrollable::Renderer + container::Renderer + text::Renderer
+{
     type Style: Default + Clone;
 
     fn decorate(
diff --git a/native/src/program/state.rs b/native/src/program/state.rs
index fdc42e8b..ddbbbb59 100644
--- a/native/src/program/state.rs
+++ b/native/src/program/state.rs
@@ -35,7 +35,7 @@ where
         renderer: &mut P::Renderer,
         debug: &mut Debug,
     ) -> Self {
-        let user_interface = build_user_interface(
+        let mut user_interface = build_user_interface(
             &mut program,
             Cache::default(),
             renderer,
@@ -153,7 +153,7 @@ where
                     command
                 }));
 
-            let user_interface = build_user_interface(
+            let mut user_interface = build_user_interface(
                 &mut self.program,
                 temp_cache,
                 renderer,
diff --git a/native/src/user_interface.rs b/native/src/user_interface.rs
index 12cea684..9ec6bb96 100644
--- a/native/src/user_interface.rs
+++ b/native/src/user_interface.rs
@@ -1,4 +1,4 @@
-use crate::{layout, Clipboard, Element, Event, Layout, Overlay, Point, Size};
+use crate::{layout, Clipboard, Element, Event, Layout, Point, Size};
 
 use std::hash::Hasher;
 
@@ -19,13 +19,13 @@ use std::hash::Hasher;
 /// [`UserInterface`]: struct.UserInterface.html
 #[allow(missing_debug_implementations)]
 pub struct UserInterface<'a, Message, Renderer> {
-    base: Layer<Element<'a, Message, Renderer>>,
-    overlay: Option<Layer<Overlay<'a, Message, Renderer>>>,
+    root: Element<'a, Message, Renderer>,
+    base: Layer,
+    overlay: Option<Layer>,
     bounds: Size,
 }
 
-struct Layer<T> {
-    root: T,
+struct Layer {
     layout: layout::Node,
     hash: u64,
 }
@@ -97,9 +97,9 @@ where
         cache: Cache,
         renderer: &mut Renderer,
     ) -> Self {
-        let mut root = root.into();
+        let root = root.into();
 
-        let (base, overlay) = {
+        let base = {
             let hash = {
                 let hasher = &mut crate::Hasher::default();
                 root.hash_layout(hasher);
@@ -115,27 +115,13 @@ where
                 renderer.layout(&root, &layout::Limits::new(Size::ZERO, bounds))
             };
 
-            let overlay = root.overlay(Layout::new(&layout));
-
-            (Layer { root, layout, hash }, overlay)
+            Layer { layout, hash }
         };
 
-        let overlay = overlay.map(|root| {
-            let hash = {
-                let hasher = &mut crate::Hasher::default();
-                root.hash_layout(hasher);
-
-                hasher.finish()
-            };
-
-            let layout = root.layout(&renderer, bounds);
-
-            Layer { root, layout, hash }
-        });
-
         UserInterface {
+            root,
             base,
-            overlay,
+            overlay: None,
             bounds,
         }
     }
@@ -215,35 +201,49 @@ where
     ) -> Vec<Message> {
         let mut messages = Vec::new();
 
-        for event in events {
-            if let Some(overlay) = &mut self.overlay {
-                let base_cursor =
-                    if overlay.layout.bounds().contains(cursor_position) {
-                        // TODO: Encode cursor availability
-                        Point::new(-1.0, -1.0)
-                    } else {
-                        cursor_position
-                    };
+        let base_events = if let Some(mut overlay) =
+            self.root.overlay(Layout::new(&self.base.layout))
+        {
+            let layer = {
+                let new_hash = {
+                    let hasher = &mut crate::Hasher::default();
+                    overlay.hash_layout(hasher);
 
-                overlay.root.on_event(
+                    hasher.finish()
+                };
+
+                let layout = match self.overlay.take() {
+                    Some(Layer { hash, layout }) if new_hash == hash => layout,
+                    _ => overlay.layout(&renderer, self.bounds),
+                };
+
+                Layer {
+                    layout,
+                    hash: new_hash,
+                }
+            };
+
+            for event in events {
+                overlay.on_event(
                     event.clone(),
-                    Layout::new(&overlay.layout),
+                    Layout::new(&layer.layout),
                     cursor_position,
                     &mut messages,
                     renderer,
                     clipboard,
                 );
+            }
 
-                self.base.root.widget.on_event(
-                    event,
-                    Layout::new(&self.base.layout),
-                    base_cursor,
-                    &mut messages,
-                    renderer,
-                    clipboard,
-                );
-            } else {
-                self.base.root.widget.on_event(
+            self.overlay = Some(layer);
+
+            None
+        } else {
+            Some(events)
+        };
+
+        if let Some(events) = base_events {
+            for event in events {
+                self.root.widget.on_event(
                     event,
                     Layout::new(&self.base.layout),
                     cursor_position,
@@ -327,12 +327,12 @@ where
     /// }
     /// ```
     pub fn draw(
-        &self,
+        &mut self,
         renderer: &mut Renderer,
         cursor_position: Point,
     ) -> Renderer::Output {
-        if let Some(overlay) = &self.overlay {
-            let overlay_bounds = overlay.layout.bounds();
+        if let Some(layer) = &self.overlay {
+            let overlay_bounds = layer.layout.bounds();
 
             let base_cursor = if overlay_bounds.contains(cursor_position) {
                 Point::new(-1.0, -1.0)
@@ -340,27 +340,33 @@ where
                 cursor_position
             };
 
-            let base_primitives = self.base.root.widget.draw(
+            let base_primitives = self.root.widget.draw(
                 renderer,
                 &Renderer::Defaults::default(),
                 Layout::new(&self.base.layout),
                 base_cursor,
             );
 
-            let overlay_primitives = overlay.root.draw(
-                renderer,
-                &Renderer::Defaults::default(),
-                Layout::new(&overlay.layout),
-                cursor_position,
-            );
+            if let Some(overlay) =
+                self.root.overlay(Layout::new(&self.base.layout))
+            {
+                let overlay_primitives = overlay.draw(
+                    renderer,
+                    &Renderer::Defaults::default(),
+                    Layout::new(&layer.layout),
+                    cursor_position,
+                );
 
-            renderer.overlay(
-                base_primitives,
-                overlay_primitives,
-                overlay_bounds,
-            )
+                renderer.overlay(
+                    base_primitives,
+                    overlay_primitives,
+                    overlay_bounds,
+                )
+            } else {
+                base_primitives
+            }
         } else {
-            self.base.root.widget.draw(
+            self.root.widget.draw(
                 renderer,
                 &Renderer::Defaults::default(),
                 Layout::new(&self.base.layout),
diff --git a/native/src/widget.rs b/native/src/widget.rs
index 664a0cfd..4bca7722 100644
--- a/native/src/widget.rs
+++ b/native/src/widget.rs
@@ -179,10 +179,10 @@ where
     ) {
     }
 
-    fn overlay(
-        &mut self,
+    fn overlay<'b>(
+        &'b mut self,
         _layout: Layout<'_>,
-    ) -> Option<Overlay<'a, Message, Renderer>> {
+    ) -> Option<Overlay<'b, Message, Renderer>> {
         None
     }
 }
diff --git a/native/src/widget/column.rs b/native/src/widget/column.rs
index 9a6dbdb3..e83ef93d 100644
--- a/native/src/widget/column.rs
+++ b/native/src/widget/column.rs
@@ -208,7 +208,7 @@ where
     fn overlay(
         &mut self,
         layout: Layout<'_>,
-    ) -> Option<Overlay<'a, Message, Renderer>> {
+    ) -> Option<Overlay<'_, Message, Renderer>> {
         self.children
             .iter_mut()
             .zip(layout.children())
diff --git a/native/src/widget/combo_box.rs b/native/src/widget/combo_box.rs
index df2a530a..4a509354 100644
--- a/native/src/widget/combo_box.rs
+++ b/native/src/widget/combo_box.rs
@@ -10,7 +10,7 @@ pub struct ComboBox<'a, T, Message, Renderer: self::Renderer>
 where
     [T]: ToOwned<Owned = Vec<T>>,
 {
-    internal: Option<Internal<'a, T, Message>>,
+    internal: Internal<'a, T, Message>,
     options: Cow<'a, [T]>,
     selected: Option<T>,
     width: Length,
@@ -42,10 +42,10 @@ where
         on_selected: impl Fn(T) -> Message + 'static,
     ) -> Self {
         Self {
-            internal: Some(Internal {
+            internal: Internal {
                 menu: &mut state.menu,
                 on_selected: Box::new(on_selected),
-            }),
+            },
             options: options.into(),
             selected,
             width: Length::Shrink,
@@ -180,16 +180,14 @@ where
     ) {
         match event {
             Event::Mouse(mouse::Event::ButtonPressed(mouse::Button::Left)) => {
-                if let Some(internal) = &mut self.internal {
-                    if layout.bounds().contains(cursor_position) {
-                        let selected = self.selected.as_ref();
-
-                        internal.menu.open(
-                            self.options
-                                .iter()
-                                .position(|option| Some(option) == selected),
-                        );
-                    }
+                if layout.bounds().contains(cursor_position) {
+                    let selected = self.selected.as_ref();
+
+                    self.internal.menu.open(
+                        self.options
+                            .iter()
+                            .position(|option| Some(option) == selected),
+                    );
                 }
             }
             _ => {}
@@ -217,33 +215,23 @@ where
     fn overlay(
         &mut self,
         layout: Layout<'_>,
-    ) -> Option<Overlay<'a, Message, Renderer>> {
-        let is_open = self
-            .internal
-            .as_ref()
-            .map(|internal| internal.menu.is_open())
-            .unwrap_or(false);
-
-        if is_open {
-            if let Some(Internal { menu, on_selected }) = self.internal.take() {
-                let bounds = layout.bounds();
-
-                Some(Overlay::new(
-                    layout.position(),
-                    Box::new(Menu::new(
-                        menu,
-                        self.options.clone(),
-                        on_selected,
-                        bounds.width.round() as u16,
-                        bounds.height,
-                        self.text_size.unwrap_or(20),
-                        self.padding,
-                        Renderer::menu_style(&self.style),
-                    )),
-                ))
-            } else {
-                None
-            }
+    ) -> Option<Overlay<'_, Message, Renderer>> {
+        if self.internal.menu.is_open() {
+            let bounds = layout.bounds();
+
+            Some(Overlay::new(
+                layout.position(),
+                Box::new(Menu::new(
+                    self.internal.menu,
+                    self.options.clone(),
+                    &self.internal.on_selected,
+                    bounds.width.round() as u16,
+                    bounds.height,
+                    self.text_size,
+                    self.padding,
+                    Renderer::menu_style(&self.style),
+                )),
+            ))
         } else {
             None
         }
diff --git a/native/src/widget/container.rs b/native/src/widget/container.rs
index 3bdb1a27..4ab10837 100644
--- a/native/src/widget/container.rs
+++ b/native/src/widget/container.rs
@@ -218,7 +218,7 @@ where
     fn overlay(
         &mut self,
         layout: Layout<'_>,
-    ) -> Option<Overlay<'a, Message, Renderer>> {
+    ) -> Option<Overlay<'_, Message, Renderer>> {
         self.content.overlay(layout.children().next().unwrap())
     }
 }
diff --git a/native/src/widget/row.rs b/native/src/widget/row.rs
index 25bd641f..1cfe2d66 100644
--- a/native/src/widget/row.rs
+++ b/native/src/widget/row.rs
@@ -210,7 +210,7 @@ where
     fn overlay(
         &mut self,
         layout: Layout<'_>,
-    ) -> Option<Overlay<'a, Message, Renderer>> {
+    ) -> Option<Overlay<'_, Message, Renderer>> {
         self.children
             .iter_mut()
             .zip(layout.children())
diff --git a/native/src/widget/scrollable.rs b/native/src/widget/scrollable.rs
index 92e5265a..87871e28 100644
--- a/native/src/widget/scrollable.rs
+++ b/native/src/widget/scrollable.rs
@@ -319,14 +319,16 @@ where
     fn overlay(
         &mut self,
         layout: Layout<'_>,
-    ) -> Option<Overlay<'a, Message, Renderer>> {
-        self.content
+    ) -> Option<Overlay<'_, Message, Renderer>> {
+        let Self { content, state, .. } = self;
+
+        content
             .overlay(layout.children().next().unwrap())
             .map(|overlay| {
                 let bounds = layout.bounds();
                 let content_layout = layout.children().next().unwrap();
                 let content_bounds = content_layout.bounds();
-                let offset = self.state.offset(bounds, content_bounds);
+                let offset = state.offset(bounds, content_bounds);
 
                 overlay.translate(Vector::new(0.0, -(offset as f32)))
             })