Add Renderer and Primitive concepts

native/src/widget/button.rs

@@ -7,7 +7,7 @@
 //! [`Class`]: enum.Class.html
 
 use crate::input::{mouse, ButtonState};
-use crate::{Element, Event, Hasher, Layout, MouseCursor, Node, Point, Widget};
+use crate::{Element, Event, Hasher, Layout, Node, Point, Widget};
 use std::hash::Hash;
 
 pub use iced_core::button::*;
@@ -63,7 +63,7 @@ where
         renderer: &mut Renderer,
         layout: Layout<'_>,
         cursor_position: Point,
-    ) -> MouseCursor {
+    ) -> Renderer::Primitive {
         renderer.draw(&self, layout, cursor_position)
     }
 
@@ -81,7 +81,7 @@ where
 ///
 /// [`Button`]: struct.Button.html
 /// [renderer]: ../../renderer/index.html
-pub trait Renderer {
+pub trait Renderer: crate::Renderer {
     /// Creates a [`Node`] for the provided [`Button`].
     ///
     /// [`Node`]: ../../struct.Node.html
@@ -96,7 +96,7 @@ pub trait Renderer {
         button: &Button<'_, Message>,
         layout: Layout<'_>,
         cursor_position: Point,
-    ) -> MouseCursor;
+    ) -> Self::Primitive;
 }
 
 impl<'a, Message, Renderer> From<Button<'a, Message>>

native/src/widget/checkbox.rs

@@ -2,7 +2,7 @@
 use std::hash::Hash;
 
 use crate::input::{mouse, ButtonState};
-use crate::{Element, Event, Hasher, Layout, MouseCursor, Node, Point, Widget};
+use crate::{Element, Event, Hasher, Layout, Node, Point, Widget};
 
 pub use iced_core::Checkbox;
 
@@ -43,7 +43,7 @@ where
         renderer: &mut Renderer,
         layout: Layout<'_>,
         cursor_position: Point,
-    ) -> MouseCursor {
+    ) -> Renderer::Primitive {
         renderer.draw(&self, layout, cursor_position)
     }
 
@@ -59,7 +59,7 @@ where
 ///
 /// [`Checkbox`]: struct.Checkbox.html
 /// [renderer]: ../../renderer/index.html
-pub trait Renderer {
+pub trait Renderer: crate::Renderer {
     /// Creates a [`Node`] for the provided [`Checkbox`].
     ///
     /// [`Node`]: ../../struct.Node.html
@@ -80,7 +80,7 @@ pub trait Renderer {
         checkbox: &Checkbox<Message>,
         layout: Layout<'_>,
         cursor_position: Point,
-    ) -> MouseCursor;
+    ) -> Self::Primitive;
 }
 
 impl<'a, Message, Renderer> From<Checkbox<Message>>

native/src/widget/column.rs

@@ -1,8 +1,6 @@
 use std::hash::Hash;
 
-use crate::{
-    Element, Event, Hasher, Layout, MouseCursor, Node, Point, Style, Widget,
-};
+use crate::{Element, Event, Hasher, Layout, Node, Point, Style, Widget};
 
 /// A container that distributes its contents vertically.
 pub type Column<'a, Message, Renderer> =
@@ -10,6 +8,8 @@ pub type Column<'a, Message, Renderer> =
 
 impl<'a, Message, Renderer> Widget<Message, Renderer>
     for Column<'a, Message, Renderer>
+where
+    Renderer: self::Renderer,
 {
     fn node(&self, renderer: &mut Renderer) -> Node {
         let mut children: Vec<Node> = self
@@ -70,21 +70,8 @@ impl<'a, Message, Renderer> Widget<Message, Renderer>
         renderer: &mut Renderer,
         layout: Layout<'_>,
         cursor_position: Point,
-    ) -> MouseCursor {
-        let mut cursor = MouseCursor::OutOfBounds;
-
-        self.children.iter().zip(layout.children()).for_each(
-            |(child, layout)| {
-                let new_cursor =
-                    child.widget.draw(renderer, layout, cursor_position);
-
-                if new_cursor != MouseCursor::OutOfBounds {
-                    cursor = new_cursor;
-                }
-            },
-        );
-
-        cursor
+    ) -> Renderer::Primitive {
+        renderer.draw(&self, layout, cursor_position)
     }
 
     fn hash_layout(&self, state: &mut Hasher) {
@@ -104,10 +91,19 @@ impl<'a, Message, Renderer> Widget<Message, Renderer>
     }
 }
 
+pub trait Renderer: crate::Renderer + Sized {
+    fn draw<Message>(
+        &mut self,
+        row: &Column<'_, Message, Self>,
+        layout: Layout<'_>,
+        cursor_position: Point,
+    ) -> Self::Primitive;
+}
+
 impl<'a, Message, Renderer> From<Column<'a, Message, Renderer>>
     for Element<'a, Message, Renderer>
 where
-    Renderer: 'a,
+    Renderer: 'a + self::Renderer,
     Message: 'static,
 {
     fn from(

native/src/widget/image.rs

@@ -20,10 +20,8 @@ where
         renderer: &mut Renderer,
         layout: Layout<'_>,
         _cursor_position: Point,
-    ) -> MouseCursor {
-        renderer.draw(&self, layout);
-
-        MouseCursor::OutOfBounds
+    ) -> Renderer::Primitive {
+        renderer.draw(&self, layout)
     }
 
     fn hash_layout(&self, state: &mut Hasher) {
@@ -40,7 +38,7 @@ where
 ///
 /// [`Image`]: struct.Image.html
 /// [renderer]: ../../renderer/index.html
-pub trait Renderer<I> {
+pub trait Renderer<I>: crate::Renderer {
     /// Creates a [`Node`] for the provided [`Image`].
     ///
     /// You should probably keep the original aspect ratio, if possible.
@@ -52,7 +50,8 @@ pub trait Renderer<I> {
     /// Draws an [`Image`].
     ///
     /// [`Image`]: struct.Image.html
-    fn draw(&mut self, image: &Image<I>, layout: Layout<'_>);
+    fn draw(&mut self, image: &Image<I>, layout: Layout<'_>)
+        -> Self::Primitive;
 }
 
 impl<'a, I, Message, Renderer> From<Image<I>> for Element<'a, Message, Renderer>

native/src/widget/radio.rs

@@ -1,6 +1,6 @@
 //! Create choices using radio buttons.
 use crate::input::{mouse, ButtonState};
-use crate::{Element, Event, Hasher, Layout, MouseCursor, Node, Point, Widget};
+use crate::{Element, Event, Hasher, Layout, Node, Point, Widget};
 
 use std::hash::Hash;
 
@@ -40,7 +40,7 @@ where
         renderer: &mut Renderer,
         layout: Layout<'_>,
         cursor_position: Point,
-    ) -> MouseCursor {
+    ) -> Renderer::Primitive {
         renderer.draw(&self, layout, cursor_position)
     }
 
@@ -56,7 +56,7 @@ where
 ///
 /// [`Radio`]: struct.Radio.html
 /// [renderer]: ../../renderer/index.html
-pub trait Renderer {
+pub trait Renderer: crate::Renderer {
     /// Creates a [`Node`] for the provided [`Radio`].
     ///
     /// [`Node`]: ../../struct.Node.html
@@ -77,7 +77,7 @@ pub trait Renderer {
         radio: &Radio<Message>,
         layout: Layout<'_>,
         cursor_position: Point,
-    ) -> MouseCursor;
+    ) -> Self::Primitive;
 }
 
 impl<'a, Message, Renderer> From<Radio<Message>>

native/src/widget/row.rs

@@ -10,6 +10,8 @@ pub type Row<'a, Message, Renderer> =
 
 impl<'a, Message, Renderer> Widget<Message, Renderer>
     for Row<'a, Message, Renderer>
+where
+    Renderer: self::Renderer,
 {
     fn node(&self, renderer: &mut Renderer) -> Node {
         let mut children: Vec<Node> = self
@@ -70,21 +72,8 @@ impl<'a, Message, Renderer> Widget<Message, Renderer>
         renderer: &mut Renderer,
         layout: Layout<'_>,
         cursor_position: Point,
-    ) -> MouseCursor {
-        let mut cursor = MouseCursor::OutOfBounds;
-
-        self.children.iter().zip(layout.children()).for_each(
-            |(child, layout)| {
-                let new_cursor =
-                    child.widget.draw(renderer, layout, cursor_position);
-
-                if new_cursor != MouseCursor::OutOfBounds {
-                    cursor = new_cursor;
-                }
-            },
-        );
-
-        cursor
+    ) -> Renderer::Primitive {
+        renderer.draw(&self, layout, cursor_position)
     }
 
     fn hash_layout(&self, state: &mut Hasher) {
@@ -105,10 +94,19 @@ impl<'a, Message, Renderer> Widget<Message, Renderer>
     }
 }
 
+pub trait Renderer: crate::Renderer + Sized {
+    fn draw<Message>(
+        &mut self,
+        row: &Row<'_, Message, Self>,
+        layout: Layout<'_>,
+        cursor_position: Point,
+    ) -> Self::Primitive;
+}
+
 impl<'a, Message, Renderer> From<Row<'a, Message, Renderer>>
     for Element<'a, Message, Renderer>
 where
-    Renderer: 'a,
+    Renderer: 'a + self::Renderer,
     Message: 'static,
 {
     fn from(row: Row<'a, Message, Renderer>) -> Element<'a, Message, Renderer> {

native/src/widget/slider.rs

@@ -71,7 +71,7 @@ where
         renderer: &mut Renderer,
         layout: Layout<'_>,
         cursor_position: Point,
-    ) -> MouseCursor {
+    ) -> Renderer::Primitive {
         renderer.draw(&self, layout, cursor_position)
     }
 
@@ -87,7 +87,7 @@ where
 ///
 /// [`Slider`]: struct.Slider.html
 /// [renderer]: ../../renderer/index.html
-pub trait Renderer {
+pub trait Renderer: crate::Renderer {
     /// Creates a [`Node`] for the provided [`Radio`].
     ///
     /// [`Node`]: ../../struct.Node.html
@@ -111,7 +111,7 @@ pub trait Renderer {
         slider: &Slider<'_, Message>,
         layout: Layout<'_>,
         cursor_position: Point,
-    ) -> MouseCursor;
+    ) -> Self::Primitive;
 }
 
 impl<'a, Message, Renderer> From<Slider<'a, Message>>

native/src/widget/text.rs

@@ -1,5 +1,5 @@
 //! Write some text for your users to read.
-use crate::{Element, Hasher, Layout, MouseCursor, Node, Point, Widget};
+use crate::{Element, Hasher, Layout, Node, Point, Widget};
 
 use std::hash::Hash;
 
@@ -18,10 +18,8 @@ where
         renderer: &mut Renderer,
         layout: Layout<'_>,
         _cursor_position: Point,
-    ) -> MouseCursor {
-        renderer.draw(&self, layout);
-
-        MouseCursor::OutOfBounds
+    ) -> Renderer::Primitive {
+        renderer.draw(&self, layout)
     }
 
     fn hash_layout(&self, state: &mut Hasher) {
@@ -40,7 +38,7 @@ where
 /// [`Text`]: struct.Text.html
 /// [renderer]: ../../renderer/index.html
 /// [`UserInterface`]: ../../struct.UserInterface.html
-pub trait Renderer {
+pub trait Renderer: crate::Renderer {
     /// Creates a [`Node`] with the given [`Style`] for the provided [`Text`]
     /// contents and size.
     ///
@@ -66,7 +64,7 @@ pub trait Renderer {
     /// [`Text`]: struct.Text.html
     /// [`HorizontalAlignment`]: enum.HorizontalAlignment.html
     /// [`VerticalAlignment`]: enum.VerticalAlignment.html
-    fn draw(&mut self, text: &Text, layout: Layout<'_>);
+    fn draw(&mut self, text: &Text, layout: Layout<'_>) -> Self::Primitive;
 }
 
 impl<'a, Message, Renderer> From<Text> for Element<'a, Message, Renderer>