Draft custom layout engine based on `druid`

10 files changed, 171 insertions, 74 deletions

diff --git a/native/src/widget/button.rs b/native/src/widget/button.rs
index 882d4a6c..980c2aae 100644
--- a/native/src/widget/button.rs
+++ b/native/src/widget/button.rs
@@ -7,7 +7,7 @@
 //! [`Class`]: enum.Class.html
 
 use crate::input::{mouse, ButtonState};
-use crate::{layout, Element, Event, Hasher, Layout, Point, Widget};
+use crate::{layout, Element, Event, Hasher, Layout, Length, Point, Widget};
 use std::hash::Hash;
 
 pub use iced_core::button::State;
@@ -21,14 +21,18 @@ where
     Renderer: self::Renderer,
     Message: Clone + std::fmt::Debug,
 {
-    fn layout(&self, renderer: &Renderer, limits: &layout::Limits) -> Layout {
+    fn layout(
+        &self,
+        renderer: &Renderer,
+        limits: &layout::Limits,
+    ) -> layout::Node {
         renderer.layout(&self, limits)
     }
 
     fn on_event(
         &mut self,
         event: Event,
-        layout: &Layout,
+        layout: Layout<'_>,
         cursor_position: Point,
         messages: &mut Vec<Message>,
         _renderer: &Renderer,
@@ -66,7 +70,7 @@ where
     fn draw(
         &self,
         renderer: &mut Renderer,
-        layout: &Layout,
+        layout: Layout<'_>,
         cursor_position: Point,
     ) -> Renderer::Output {
         renderer.draw(&self, layout, cursor_position)
@@ -95,7 +99,7 @@ pub trait Renderer: crate::Renderer + Sized {
         &self,
         button: &Button<'_, Message, Self>,
         limits: &layout::Limits,
-    ) -> Layout;
+    ) -> layout::Node;
 
     /// Draws a [`Button`].
     ///
@@ -103,7 +107,7 @@ pub trait Renderer: crate::Renderer + Sized {
     fn draw<Message>(
         &mut self,
         button: &Button<'_, Message, Self>,
-        layout: &Layout,
+        layout: Layout<'_>,
         cursor_position: Point,
     ) -> Self::Output;
 }
diff --git a/native/src/widget/checkbox.rs b/native/src/widget/checkbox.rs
index 12a6a728..a7040e02 100644
--- a/native/src/widget/checkbox.rs
+++ b/native/src/widget/checkbox.rs
@@ -10,14 +10,18 @@ impl<Message, Renderer> Widget<Message, Renderer> for Checkbox<Message>
 where
     Renderer: self::Renderer,
 {
-    fn layout(&self, renderer: &Renderer, limits: &layout::Limits) -> Layout {
+    fn layout(
+        &self,
+        renderer: &Renderer,
+        limits: &layout::Limits,
+    ) -> layout::Node {
         renderer.layout(&self, limits)
     }
 
     fn on_event(
         &mut self,
         event: Event,
-        layout: &Layout,
+        layout: Layout<'_>,
         cursor_position: Point,
         messages: &mut Vec<Message>,
         _renderer: &Renderer,
@@ -40,7 +44,7 @@ where
     fn draw(
         &self,
         renderer: &mut Renderer,
-        layout: &Layout,
+        layout: Layout<'_>,
         cursor_position: Point,
     ) -> Renderer::Output {
         renderer.draw(&self, layout, cursor_position)
@@ -67,7 +71,7 @@ pub trait Renderer: crate::Renderer {
         &self,
         checkbox: &Checkbox<Message>,
         limits: &layout::Limits,
-    ) -> Layout;
+    ) -> layout::Node;
 
     /// Draws a [`Checkbox`].
     ///
@@ -81,7 +85,7 @@ pub trait Renderer: crate::Renderer {
     fn draw<Message>(
         &mut self,
         checkbox: &Checkbox<Message>,
-        layout: &Layout,
+        layout: Layout<'_>,
         cursor_position: Point,
     ) -> Self::Output;
 }
diff --git a/native/src/widget/column.rs b/native/src/widget/column.rs
index d0446ec9..ed8a2b89 100644
--- a/native/src/widget/column.rs
+++ b/native/src/widget/column.rs
@@ -1,6 +1,8 @@
 use std::hash::Hash;
 
-use crate::{layout, Element, Event, Hasher, Layout, Point, Rectangle, Widget};
+use crate::{
+    layout, Element, Event, Hasher, Layout, Length, Point, Size, Widget,
+};
 
 /// A container that distributes its contents vertically.
 pub type Column<'a, Message, Renderer> =
@@ -11,20 +13,35 @@ impl<'a, Message, Renderer> Widget<Message, Renderer>
 where
     Renderer: self::Renderer,
 {
-    fn layout(&self, renderer: &Renderer, limits: &layout::Limits) -> Layout {
-        // TODO
-        Layout::new(Rectangle {
-            x: 0.0,
-            y: 0.0,
-            width: 0.0,
-            height: 0.0,
-        })
+    fn width(&self) -> Length {
+        self.width
+    }
+
+    fn layout(
+        &self,
+        renderer: &Renderer,
+        limits: &layout::Limits,
+    ) -> layout::Node {
+        let limits = limits
+            .max_width(self.max_width)
+            .max_height(self.max_height)
+            .width(self.width)
+            .height(self.height);
+
+        layout::flex::resolve(
+            layout::flex::Axis::Vertical,
+            renderer,
+            &limits,
+            self.padding as f32,
+            self.spacing as f32,
+            &self.children,
+        )
     }
 
     fn on_event(
         &mut self,
         event: Event,
-        layout: &Layout,
+        layout: Layout<'_>,
         cursor_position: Point,
         messages: &mut Vec<Message>,
         renderer: &Renderer,
@@ -45,7 +62,7 @@ where
     fn draw(
         &self,
         renderer: &mut Renderer,
-        layout: &Layout,
+        layout: Layout<'_>,
         cursor_position: Point,
     ) -> Renderer::Output {
         renderer.draw(&self, layout, cursor_position)
@@ -72,7 +89,7 @@ pub trait Renderer: crate::Renderer + Sized {
     fn draw<Message>(
         &mut self,
         row: &Column<'_, Message, Self>,
-        layout: &Layout,
+        layout: Layout<'_>,
         cursor_position: Point,
     ) -> Self::Output;
 }
diff --git a/native/src/widget/image.rs b/native/src/widget/image.rs
index b503f95c..abc45d6a 100644
--- a/native/src/widget/image.rs
+++ b/native/src/widget/image.rs
@@ -10,14 +10,18 @@ impl<Message, Renderer> Widget<Message, Renderer> for Image
 where
     Renderer: self::Renderer,
 {
-    fn layout(&self, renderer: &Renderer, limits: &layout::Limits) -> Layout {
+    fn layout(
+        &self,
+        renderer: &Renderer,
+        limits: &layout::Limits,
+    ) -> layout::Node {
         renderer.layout(&self, limits)
     }
 
     fn draw(
         &self,
         renderer: &mut Renderer,
-        layout: &Layout,
+        layout: Layout<'_>,
         _cursor_position: Point,
     ) -> Renderer::Output {
         renderer.draw(&self, layout)
@@ -44,12 +48,12 @@ pub trait Renderer: crate::Renderer {
     ///
     /// [`Node`]: ../../struct.Node.html
     /// [`Image`]: struct.Image.html
-    fn layout(&self, image: &Image, limits: &layout::Limits) -> Layout;
+    fn layout(&self, image: &Image, limits: &layout::Limits) -> layout::Node;
 
     /// Draws an [`Image`].
     ///
     /// [`Image`]: struct.Image.html
-    fn draw(&mut self, image: &Image, layout: &Layout) -> Self::Output;
+    fn draw(&mut self, image: &Image, layout: Layout<'_>) -> Self::Output;
 }
 
 impl<'a, Message, Renderer> From<Image> for Element<'a, Message, Renderer>
diff --git a/native/src/widget/radio.rs b/native/src/widget/radio.rs
index 86d507da..b68919e5 100644
--- a/native/src/widget/radio.rs
+++ b/native/src/widget/radio.rs
@@ -1,6 +1,6 @@
 //! Create choices using radio buttons.
 use crate::input::{mouse, ButtonState};
-use crate::{layout, Element, Event, Hasher, Layout, Point, Widget};
+use crate::{layout, Element, Event, Hasher, Layout, Length, Point, Widget};
 
 use std::hash::Hash;
 
@@ -11,14 +11,22 @@ where
     Renderer: self::Renderer,
     Message: Clone + std::fmt::Debug,
 {
-    fn layout(&self, renderer: &Renderer, limits: &layout::Limits) -> Layout {
+    fn width(&self) -> Length {
+        Length::Fill
+    }
+
+    fn layout(
+        &self,
+        renderer: &Renderer,
+        limits: &layout::Limits,
+    ) -> layout::Node {
         renderer.layout(&self, limits)
     }
 
     fn on_event(
         &mut self,
         event: Event,
-        layout: &Layout,
+        layout: Layout<'_>,
         cursor_position: Point,
         messages: &mut Vec<Message>,
         _renderer: &Renderer,
@@ -39,7 +47,7 @@ where
     fn draw(
         &self,
         renderer: &mut Renderer,
-        layout: &Layout,
+        layout: Layout<'_>,
         cursor_position: Point,
     ) -> Renderer::Output {
         renderer.draw(&self, layout, cursor_position)
@@ -66,7 +74,7 @@ pub trait Renderer: crate::Renderer {
         &self,
         radio: &Radio<Message>,
         limits: &layout::Limits,
-    ) -> Layout;
+    ) -> layout::Node;
 
     /// Draws a [`Radio`] button.
     ///
@@ -80,7 +88,7 @@ pub trait Renderer: crate::Renderer {
     fn draw<Message>(
         &mut self,
         radio: &Radio<Message>,
-        layout: &Layout,
+        layout: Layout<'_>,
         cursor_position: Point,
     ) -> Self::Output;
 }
diff --git a/native/src/widget/row.rs b/native/src/widget/row.rs
index ca1cda23..7ea54a71 100644
--- a/native/src/widget/row.rs
+++ b/native/src/widget/row.rs
@@ -1,6 +1,6 @@
 use std::hash::Hash;
 
-use crate::{layout, Element, Event, Hasher, Layout, Point, Rectangle, Widget};
+use crate::{layout, Element, Event, Hasher, Layout, Length, Point, Widget};
 
 /// A container that distributes its contents horizontally.
 pub type Row<'a, Message, Renderer> =
@@ -11,20 +11,35 @@ impl<'a, Message, Renderer> Widget<Message, Renderer>
 where
     Renderer: self::Renderer,
 {
-    fn layout(&self, renderer: &Renderer, limits: &layout::Limits) -> Layout {
-        // TODO
-        Layout::new(Rectangle {
-            x: 0.0,
-            y: 0.0,
-            width: 0.0,
-            height: 0.0,
-        })
+    fn width(&self) -> Length {
+        self.width
+    }
+
+    fn layout(
+        &self,
+        renderer: &Renderer,
+        limits: &layout::Limits,
+    ) -> layout::Node {
+        let limits = limits
+            .max_width(self.max_width)
+            .max_height(self.max_height)
+            .width(self.width)
+            .height(self.height);
+
+        layout::flex::resolve(
+            layout::flex::Axis::Horizontal,
+            renderer,
+            &limits,
+            self.padding as f32,
+            self.spacing as f32,
+            &self.children,
+        )
     }
 
     fn on_event(
         &mut self,
         event: Event,
-        layout: &Layout,
+        layout: Layout<'_>,
         cursor_position: Point,
         messages: &mut Vec<Message>,
         renderer: &Renderer,
@@ -45,7 +60,7 @@ where
     fn draw(
         &self,
         renderer: &mut Renderer,
-        layout: &Layout,
+        layout: Layout<'_>,
         cursor_position: Point,
     ) -> Renderer::Output {
         renderer.draw(&self, layout, cursor_position)
@@ -73,7 +88,7 @@ pub trait Renderer: crate::Renderer + Sized {
     fn draw<Message>(
         &mut self,
         row: &Row<'_, Message, Self>,
-        layout: &Layout,
+        layout: Layout<'_>,
         cursor_position: Point,
     ) -> Self::Output;
 }
diff --git a/native/src/widget/scrollable.rs b/native/src/widget/scrollable.rs
index a5eb2f01..775c59db 100644
--- a/native/src/widget/scrollable.rs
+++ b/native/src/widget/scrollable.rs
@@ -1,11 +1,13 @@
 use crate::{
     column,
     input::{mouse, ButtonState},
-    layout, Element, Event, Hasher, Layout, Point, Rectangle, Widget,
+    layout, Element, Event, Hasher, Layout, Length, Point, Rectangle, Size,
+    Widget,
 };
 
 pub use iced_core::scrollable::State;
 
+use std::f32;
 use std::hash::Hash;
 
 /// A scrollable [`Column`].
@@ -19,15 +21,31 @@ impl<'a, Message, Renderer> Widget<Message, Renderer>
 where
     Renderer: self::Renderer + column::Renderer,
 {
-    fn layout(&self, renderer: &Renderer, limits: &layout::Limits) -> Layout {
-        // TODO
-        self.content.layout(renderer, limits)
+    fn layout(
+        &self,
+        renderer: &Renderer,
+        limits: &layout::Limits,
+    ) -> layout::Node {
+        let limits = limits
+            .max_height(self.max_height)
+            .width(Length::Fill)
+            .height(self.height);
+
+        let child_limits = layout::Limits::new(
+            Size::new(limits.min().width, 0.0),
+            Size::new(limits.max().width, f32::INFINITY),
+        );
+
+        let content = self.content.layout(renderer, &child_limits);
+        let size = limits.resolve(content.size());
+
+        layout::Node::with_children(size, vec![content])
     }
 
     fn on_event(
         &mut self,
         event: Event,
-        layout: &Layout,
+        layout: Layout<'_>,
         cursor_position: Point,
         messages: &mut Vec<Message>,
         renderer: &Renderer,
@@ -130,7 +148,7 @@ where
     fn draw(
         &self,
         renderer: &mut Renderer,
-        layout: &Layout,
+        layout: Layout<'_>,
         cursor_position: Point,
     ) -> Renderer::Output {
         let bounds = layout.bounds();
@@ -168,7 +186,7 @@ pub trait Renderer: crate::Renderer + Sized {
         &mut self,
         scrollable: &Scrollable<'_, Message, Self>,
         bounds: Rectangle,
-        content_layout: &Layout,
+        content_layout: Layout<'_>,
         cursor_position: Point,
     ) -> Self::Output;
 }
diff --git a/native/src/widget/slider.rs b/native/src/widget/slider.rs
index be4ed564..3a998c40 100644
--- a/native/src/widget/slider.rs
+++ b/native/src/widget/slider.rs
@@ -7,7 +7,7 @@
 use std::hash::Hash;
 
 use crate::input::{mouse, ButtonState};
-use crate::{layout, Element, Event, Hasher, Layout, Point, Widget};
+use crate::{layout, Element, Event, Hasher, Layout, Length, Point, Widget};
 
 pub use iced_core::slider::*;
 
@@ -15,14 +15,22 @@ impl<'a, Message, Renderer> Widget<Message, Renderer> for Slider<'a, Message>
 where
     Renderer: self::Renderer,
 {
-    fn layout(&self, renderer: &Renderer, limits: &layout::Limits) -> Layout {
+    fn width(&self) -> Length {
+        self.width
+    }
+
+    fn layout(
+        &self,
+        renderer: &Renderer,
+        limits: &layout::Limits,
+    ) -> layout::Node {
         renderer.layout(&self, limits)
     }
 
     fn on_event(
         &mut self,
         event: Event,
-        layout: &Layout,
+        layout: Layout<'_>,
         cursor_position: Point,
         messages: &mut Vec<Message>,
         _renderer: &Renderer,
@@ -70,7 +78,7 @@ where
     fn draw(
         &self,
         renderer: &mut Renderer,
-        layout: &Layout,
+        layout: Layout<'_>,
         cursor_position: Point,
     ) -> Renderer::Output {
         renderer.draw(&self, layout, cursor_position)
@@ -97,7 +105,7 @@ pub trait Renderer: crate::Renderer {
         &self,
         slider: &Slider<'_, Message>,
         limits: &layout::Limits,
-    ) -> Layout;
+    ) -> layout::Node;
 
     /// Draws a [`Slider`].
     ///
@@ -114,7 +122,7 @@ pub trait Renderer: crate::Renderer {
     fn draw<Message>(
         &mut self,
         slider: &Slider<'_, Message>,
-        layout: &Layout,
+        layout: Layout<'_>,
         cursor_position: Point,
     ) -> Self::Output;
 }
diff --git a/native/src/widget/text.rs b/native/src/widget/text.rs
index da8563a4..10d892a3 100644
--- a/native/src/widget/text.rs
+++ b/native/src/widget/text.rs
@@ -1,5 +1,5 @@
 //! Write some text for your users to read.
-use crate::{layout, Element, Hasher, Layout, Point, Widget};
+use crate::{layout, Element, Hasher, Layout, Length, Point, Widget};
 
 use std::hash::Hash;
 
@@ -9,14 +9,22 @@ impl<Message, Renderer> Widget<Message, Renderer> for Text
 where
     Renderer: self::Renderer,
 {
-    fn layout(&self, renderer: &Renderer, limits: &layout::Limits) -> Layout {
+    fn width(&self) -> Length {
+        self.width
+    }
+
+    fn layout(
+        &self,
+        renderer: &Renderer,
+        limits: &layout::Limits,
+    ) -> layout::Node {
         renderer.layout(&self, limits)
     }
 
     fn draw(
         &self,
         renderer: &mut Renderer,
-        layout: &Layout,
+        layout: Layout<'_>,
         _cursor_position: Point,
     ) -> Renderer::Output {
         renderer.draw(&self, layout)
@@ -49,7 +57,7 @@ pub trait Renderer: crate::Renderer {
     /// [`Style`]: ../../struct.Style.html
     /// [`Text`]: struct.Text.html
     /// [`Node::with_measure`]: ../../struct.Node.html#method.with_measure
-    fn layout(&self, text: &Text, limits: &layout::Limits) -> Layout;
+    fn layout(&self, text: &Text, limits: &layout::Limits) -> layout::Node;
 
     /// Draws a [`Text`] fragment.
     ///
@@ -64,7 +72,7 @@ pub trait Renderer: crate::Renderer {
     /// [`Text`]: struct.Text.html
     /// [`HorizontalAlignment`]: enum.HorizontalAlignment.html
     /// [`VerticalAlignment`]: enum.VerticalAlignment.html
-    fn draw(&mut self, text: &Text, layout: &Layout) -> Self::Output;
+    fn draw(&mut self, text: &Text, layout: Layout<'_>) -> Self::Output;
 }
 
 impl<'a, Message, Renderer> From<Text> for Element<'a, Message, Renderer>
diff --git a/native/src/widget/text_input.rs b/native/src/widget/text_input.rs
index ca72801d..7e81e257 100644
--- a/native/src/widget/text_input.rs
+++ b/native/src/widget/text_input.rs
@@ -1,6 +1,7 @@
 use crate::{
     input::{keyboard, mouse, ButtonState},
-    layout, Element, Event, Hasher, Layout, Point, Rectangle, Widget,
+    layout, Element, Event, Hasher, Layout, Length, Point, Rectangle, Size,
+    Widget,
 };
 
 pub use iced_core::{text_input::State, TextInput};
@@ -10,20 +11,30 @@ where
     Renderer: self::Renderer,
     Message: Clone + std::fmt::Debug,
 {
-    fn layout(&self, renderer: &Renderer, limits: &layout::Limits) -> Layout {
-        // TODO
-        Layout::new(Rectangle {
-            x: 0.0,
-            y: 0.0,
-            width: 0.0,
-            height: 0.0,
-        })
+    fn layout(
+        &self,
+        renderer: &Renderer,
+        limits: &layout::Limits,
+    ) -> layout::Node {
+        let padding = self.padding as f32;
+        let text_size = self.size.unwrap_or(renderer.default_size());
+
+        let limits = limits
+            .pad(padding)
+            .width(self.width)
+            .height(Length::Units(text_size));
+
+        let mut text = layout::Node::new(limits.resolve(Size::ZERO));
+        text.bounds.x = padding;
+        text.bounds.y = padding;
+
+        layout::Node::with_children(text.size().pad(padding), vec![text])
     }
 
     fn on_event(
         &mut self,
         event: Event,
-        layout: &Layout,
+        layout: Layout<'_>,
         cursor_position: Point,
         messages: &mut Vec<Message>,
         _renderer: &Renderer,
@@ -95,7 +106,7 @@ where
     fn draw(
         &self,
         renderer: &mut Renderer,
-        layout: &Layout,
+        layout: Layout<'_>,
         cursor_position: Point,
     ) -> Renderer::Output {
         let bounds = layout.bounds();