Draft first-class `Theme` support

RFC: https://github.com/iced-rs/rfcs/pull/6

27 files changed, 101 insertions, 16 deletions

diff --git a/pure/src/element.rs b/pure/src/element.rs
index 5450db20..35c68716 100644
--- a/pure/src/element.rs
+++ b/pure/src/element.rs
@@ -25,7 +25,10 @@ pub struct Element<'a, Message, Renderer> {
 
 impl<'a, Message, Renderer> Element<'a, Message, Renderer> {
     /// Creates a new [`Element`] containing the given [`Widget`].
-    pub fn new(widget: impl Widget<Message, Renderer> + 'a) -> Self {
+    pub fn new(widget: impl Widget<Message, Renderer> + 'a) -> Self
+    where
+        Renderer: iced_native::Renderer,
+    {
         Self {
             widget: Box::new(widget),
         }
@@ -278,6 +281,7 @@ where
         &self,
         tree: &Tree,
         renderer: &mut Renderer,
+        theme: &Renderer::Theme,
         style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
@@ -286,6 +290,7 @@ where
         self.widget.draw(
             tree,
             renderer,
+            theme,
             style,
             layout,
             cursor_position,
diff --git a/pure/src/helpers.rs b/pure/src/helpers.rs
index 746b807d..ad6f10b1 100644
--- a/pure/src/helpers.rs
+++ b/pure/src/helpers.rs
@@ -50,7 +50,12 @@ where
 /// [`Button`]: widget::Button
 pub fn button<'a, Message, Renderer>(
     content: impl Into<Element<'a, Message, Renderer>>,
-) -> widget::Button<'a, Message, Renderer> {
+) -> widget::Button<'a, Message, Renderer>
+where
+    Renderer: iced_native::Renderer,
+    Renderer::Theme: widget::button::StyleSheet,
+    <Renderer::Theme as widget::button::StyleSheet>::Variant: Default,
+{
     widget::Button::new(content)
 }
 
diff --git a/pure/src/lib.rs b/pure/src/lib.rs
index fa5fd46f..95aa3098 100644
--- a/pure/src/lib.rs
+++ b/pure/src/lib.rs
@@ -174,7 +174,9 @@ impl State {
     fn diff<Message, Renderer>(
         &mut self,
         new_element: &Element<'_, Message, Renderer>,
-    ) {
+    ) where
+        Renderer: iced_native::Renderer,
+    {
         self.state_tree.diff(new_element);
     }
 }
@@ -224,6 +226,7 @@ where
     fn draw(
         &self,
         renderer: &mut Renderer,
+        theme: &Renderer::Theme,
         style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
@@ -232,6 +235,7 @@ where
         self.element.as_widget().draw(
             &self.state.state_tree,
             renderer,
+            theme,
             style,
             layout,
             cursor_position,
diff --git a/pure/src/overlay.rs b/pure/src/overlay.rs
index fecaa2ac..b82d8a67 100644
--- a/pure/src/overlay.rs
+++ b/pure/src/overlay.rs
@@ -14,7 +14,10 @@ pub fn from_children<'a, Message, Renderer>(
     tree: &'a mut Tree,
     layout: Layout<'_>,
     renderer: &Renderer,
-) -> Option<Element<'a, Message, Renderer>> {
+) -> Option<Element<'a, Message, Renderer>>
+where
+    Renderer: iced_native::Renderer,
+{
     children
         .iter()
         .zip(&mut tree.children)
diff --git a/pure/src/widget.rs b/pure/src/widget.rs
index cc04cc96..ab63f7cc 100644
--- a/pure/src/widget.rs
+++ b/pure/src/widget.rs
@@ -53,7 +53,10 @@ use iced_native::{Clipboard, Length, Point, Rectangle, Shell};
 ///
 /// If you want to build your own widgets, you will need to implement this
 /// trait.
-pub trait Widget<Message, Renderer> {
+pub trait Widget<Message, Renderer>
+where
+    Renderer: iced_native::Renderer,
+{
     /// Returns the width of the [`Widget`].
     fn width(&self) -> Length;
 
@@ -75,6 +78,7 @@ pub trait Widget<Message, Renderer> {
         &self,
         state: &Tree,
         renderer: &mut Renderer,
+        theme: &Renderer::Theme,
         style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
diff --git a/pure/src/widget/button.rs b/pure/src/widget/button.rs
index 456c2509..45f4a6aa 100644
--- a/pure/src/widget/button.rs
+++ b/pure/src/widget/button.rs
@@ -50,25 +50,34 @@ use button::State;
 ///     disabled_button().on_press(Message::ButtonPressed)
 /// }
 /// ```
-pub struct Button<'a, Message, Renderer> {
+pub struct Button<'a, Message, Renderer>
+where
+    Renderer: iced_native::Renderer,
+    Renderer::Theme: StyleSheet,
+{
     content: Element<'a, Message, Renderer>,
     on_press: Option<Message>,
-    style_sheet: Box<dyn StyleSheet + 'a>,
     width: Length,
     height: Length,
     padding: Padding,
+    variant: <Renderer::Theme as StyleSheet>::Variant,
 }
 
-impl<'a, Message, Renderer> Button<'a, Message, Renderer> {
+impl<'a, Message, Renderer> Button<'a, Message, Renderer>
+where
+    Renderer: iced_native::Renderer,
+    Renderer::Theme: StyleSheet,
+    <Renderer::Theme as StyleSheet>::Variant: Default,
+{
     /// Creates a new [`Button`] with the given content.
     pub fn new(content: impl Into<Element<'a, Message, Renderer>>) -> Self {
         Button {
             content: content.into(),
             on_press: None,
-            style_sheet: Default::default(),
             width: Length::Shrink,
             height: Length::Shrink,
             padding: Padding::new(5),
+            variant: <Renderer::Theme as StyleSheet>::Variant::default(),
         }
     }
 
@@ -98,12 +107,12 @@ impl<'a, Message, Renderer> Button<'a, Message, Renderer> {
         self
     }
 
-    /// Sets the style of the [`Button`].
+    /// Sets the style variant of this [`Button`].
     pub fn style(
         mut self,
-        style_sheet: impl Into<Box<dyn StyleSheet + 'a>>,
+        variant: <Renderer::Theme as StyleSheet>::Variant,
     ) -> Self {
-        self.style_sheet = style_sheet.into();
+        self.variant = variant;
         self
     }
 }
@@ -113,6 +122,8 @@ impl<'a, Message, Renderer> Widget<Message, Renderer>
 where
     Message: 'a + Clone,
     Renderer: 'a + iced_native::Renderer,
+    Renderer::Theme: StyleSheet,
+    <Renderer::Theme as StyleSheet>::Variant: Copy,
 {
     fn tag(&self) -> tree::Tag {
         tree::Tag::of::<State>()
@@ -191,6 +202,7 @@ where
         &self,
         tree: &Tree,
         renderer: &mut Renderer,
+        theme: &Renderer::Theme,
         _style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
@@ -204,13 +216,15 @@ where
             bounds,
             cursor_position,
             self.on_press.is_some(),
-            self.style_sheet.as_ref(),
+            theme,
+            self.variant,
             || tree.state.downcast_ref::<State>(),
         );
 
         self.content.as_widget().draw(
             &tree.children[0],
             renderer,
+            theme,
             &renderer::Style {
                 text_color: styling.text_color,
             },
@@ -254,6 +268,8 @@ impl<'a, Message, Renderer> Into<Element<'a, Message, Renderer>>
 where
     Message: Clone + 'a,
     Renderer: iced_native::Renderer + 'a,
+    Renderer::Theme: StyleSheet,
+    <Renderer::Theme as StyleSheet>::Variant: Copy,
 {
     fn into(self) -> Element<'a, Message, Renderer> {
         Element::new(self)
diff --git a/pure/src/widget/checkbox.rs b/pure/src/widget/checkbox.rs
index 98f55a56..a6a6f8de 100644
--- a/pure/src/widget/checkbox.rs
+++ b/pure/src/widget/checkbox.rs
@@ -59,6 +59,7 @@ where
         &self,
         _tree: &Tree,
         renderer: &mut Renderer,
+        theme: &Renderer::Theme,
         style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
@@ -67,6 +68,7 @@ where
         <Self as iced_native::Widget<Message, Renderer>>::draw(
             self,
             renderer,
+            theme,
             style,
             layout,
             cursor_position,
diff --git a/pure/src/widget/column.rs b/pure/src/widget/column.rs
index 7256f474..74d789a1 100644
--- a/pure/src/widget/column.rs
+++ b/pure/src/widget/column.rs
@@ -194,6 +194,7 @@ where
         &self,
         tree: &Tree,
         renderer: &mut Renderer,
+        theme: &Renderer::Theme,
         style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
@@ -208,6 +209,7 @@ where
             child.as_widget().draw(
                 state,
                 renderer,
+                theme,
                 style,
                 layout,
                 cursor_position,
diff --git a/pure/src/widget/container.rs b/pure/src/widget/container.rs
index 91db1f3f..0ec2351a 100644
--- a/pure/src/widget/container.rs
+++ b/pure/src/widget/container.rs
@@ -201,6 +201,7 @@ where
         &self,
         tree: &Tree,
         renderer: &mut Renderer,
+        theme: &Renderer::Theme,
         renderer_style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
@@ -213,6 +214,7 @@ where
         self.content.as_widget().draw(
             &tree.children[0],
             renderer,
+            theme,
             &renderer::Style {
                 text_color: style
                     .text_color
diff --git a/pure/src/widget/image.rs b/pure/src/widget/image.rs
index ef764ec2..c42113dc 100644
--- a/pure/src/widget/image.rs
+++ b/pure/src/widget/image.rs
@@ -38,6 +38,7 @@ where
         &self,
         _tree: &Tree,
         renderer: &mut Renderer,
+        theme: &Renderer::Theme,
         style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
@@ -46,6 +47,7 @@ where
         <Self as iced_native::Widget<Message, Renderer>>::draw(
             self,
             renderer,
+            theme,
             style,
             layout,
             cursor_position,
diff --git a/pure/src/widget/pane_grid.rs b/pure/src/widget/pane_grid.rs
index c532a6de..168fe12b 100644
--- a/pure/src/widget/pane_grid.rs
+++ b/pure/src/widget/pane_grid.rs
@@ -331,6 +331,7 @@ where
         &self,
         tree: &Tree,
         renderer: &mut Renderer,
+        theme: &Renderer::Theme,
         style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
@@ -360,6 +361,7 @@ where
                 content.draw(
                     tree,
                     renderer,
+                    theme,
                     style,
                     layout,
                     cursor_position,
diff --git a/pure/src/widget/pane_grid/content.rs b/pure/src/widget/pane_grid/content.rs
index e66ac40b..5069bd4a 100644
--- a/pure/src/widget/pane_grid/content.rs
+++ b/pure/src/widget/pane_grid/content.rs
@@ -89,6 +89,7 @@ where
         &self,
         tree: &Tree,
         renderer: &mut Renderer,
+        theme: &Renderer::Theme,
         style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
@@ -112,6 +113,7 @@ where
             title_bar.draw(
                 &tree.children[1],
                 renderer,
+                theme,
                 style,
                 title_bar_layout,
                 cursor_position,
@@ -122,6 +124,7 @@ where
             self.body.as_widget().draw(
                 &tree.children[0],
                 renderer,
+                theme,
                 style,
                 body_layout,
                 cursor_position,
@@ -131,6 +134,7 @@ where
             self.body.as_widget().draw(
                 &tree.children[0],
                 renderer,
+                theme,
                 style,
                 layout,
                 cursor_position,
diff --git a/pure/src/widget/pane_grid/title_bar.rs b/pure/src/widget/pane_grid/title_bar.rs
index 4a7c8c17..28a3d7fc 100644
--- a/pure/src/widget/pane_grid/title_bar.rs
+++ b/pure/src/widget/pane_grid/title_bar.rs
@@ -113,6 +113,7 @@ where
         &self,
         tree: &Tree,
         renderer: &mut Renderer,
+        theme: &Renderer::Theme,
         inherited_style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
@@ -136,6 +137,7 @@ where
         self.content.as_widget().draw(
             &tree.children[0],
             renderer,
+            theme,
             &inherited_style,
             title_layout,
             cursor_position,
@@ -149,6 +151,7 @@ where
                 controls.as_widget().draw(
                     &tree.children[1],
                     renderer,
+                    theme,
                     &inherited_style,
                     controls_layout,
                     cursor_position,
diff --git a/pure/src/widget/pick_list.rs b/pure/src/widget/pick_list.rs
index 255e3681..78302a7d 100644
--- a/pure/src/widget/pick_list.rs
+++ b/pure/src/widget/pick_list.rs
@@ -181,6 +181,7 @@ where
         &self,
         _tree: &Tree,
         renderer: &mut Renderer,
+        _theme: &Renderer::Theme,
         _style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
diff --git a/pure/src/widget/progress_bar.rs b/pure/src/widget/progress_bar.rs
index 3016a81a..47a299ac 100644
--- a/pure/src/widget/progress_bar.rs
+++ b/pure/src/widget/progress_bar.rs
@@ -57,6 +57,7 @@ where
         &self,
         _tree: &Tree,
         renderer: &mut Renderer,
+        theme: &Renderer::Theme,
         style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
@@ -65,6 +66,7 @@ where
         <Self as iced_native::Widget<Message, Renderer>>::draw(
             self,
             renderer,
+            theme,
             style,
             layout,
             cursor_position,
diff --git a/pure/src/widget/radio.rs b/pure/src/widget/radio.rs
index 7c98c937..c92c8dbc 100644
--- a/pure/src/widget/radio.rs
+++ b/pure/src/widget/radio.rs
@@ -60,6 +60,7 @@ where
         &self,
         _tree: &Tree,
         renderer: &mut Renderer,
+        theme: &Renderer::Theme,
         style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
@@ -68,6 +69,7 @@ where
         <Self as iced_native::Widget<Message, Renderer>>::draw(
             self,
             renderer,
+            theme,
             style,
             layout,
             cursor_position,
diff --git a/pure/src/widget/row.rs b/pure/src/widget/row.rs
index 0385b8bd..e747adfc 100644
--- a/pure/src/widget/row.rs
+++ b/pure/src/widget/row.rs
@@ -181,6 +181,7 @@ where
         &self,
         tree: &Tree,
         renderer: &mut Renderer,
+        theme: &Renderer::Theme,
         style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
@@ -195,6 +196,7 @@ where
             child.as_widget().draw(
                 state,
                 renderer,
+                theme,
                 style,
                 layout,
                 cursor_position,
diff --git a/pure/src/widget/rule.rs b/pure/src/widget/rule.rs
index ab8537ae..8e6af58e 100644
--- a/pure/src/widget/rule.rs
+++ b/pure/src/widget/rule.rs
@@ -57,6 +57,7 @@ where
         &self,
         _tree: &Tree,
         renderer: &mut Renderer,
+        theme: &Renderer::Theme,
         style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
@@ -65,6 +66,7 @@ where
         <Self as iced_native::Widget<Message, Renderer>>::draw(
             self,
             renderer,
+            theme,
             style,
             layout,
             cursor_position,
diff --git a/pure/src/widget/scrollable.rs b/pure/src/widget/scrollable.rs
index 70e951ef..a0180dc0 100644
--- a/pure/src/widget/scrollable.rs
+++ b/pure/src/widget/scrollable.rs
@@ -171,6 +171,7 @@ where
         &self,
         tree: &Tree,
         renderer: &mut Renderer,
+        theme: &Renderer::Theme,
         style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
@@ -189,6 +190,7 @@ where
                 self.content.as_widget().draw(
                     &tree.children[0],
                     renderer,
+                    theme,
                     style,
                     layout,
                     cursor_position,
diff --git a/pure/src/widget/slider.rs b/pure/src/widget/slider.rs
index 4d8bbce4..2f934a48 100644
--- a/pure/src/widget/slider.rs
+++ b/pure/src/widget/slider.rs
@@ -195,6 +195,7 @@ where
         &self,
         tree: &Tree,
         renderer: &mut Renderer,
+        theme: &Renderer::Theme,
         _style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
diff --git a/pure/src/widget/space.rs b/pure/src/widget/space.rs
index b408153b..7d95ebd7 100644
--- a/pure/src/widget/space.rs
+++ b/pure/src/widget/space.rs
@@ -56,6 +56,7 @@ where
         &self,
         _tree: &Tree,
         renderer: &mut Renderer,
+        theme: &Renderer::Theme,
         style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
@@ -64,6 +65,7 @@ where
         <Self as iced_native::Widget<Message, Renderer>>::draw(
             self,
             renderer,
+            theme,
             style,
             layout,
             cursor_position,
diff --git a/pure/src/widget/svg.rs b/pure/src/widget/svg.rs
index 14180097..501d9bfa 100644
--- a/pure/src/widget/svg.rs
+++ b/pure/src/widget/svg.rs
@@ -36,6 +36,7 @@ where
         &self,
         _tree: &Tree,
         renderer: &mut Renderer,
+        theme: &Renderer::Theme,
         style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
@@ -44,6 +45,7 @@ where
         <Self as iced_native::Widget<Message, Renderer>>::draw(
             self,
             renderer,
+            theme,
             style,
             layout,
             cursor_position,
diff --git a/pure/src/widget/text.rs b/pure/src/widget/text.rs
index 58a939c1..0a51b628 100644
--- a/pure/src/widget/text.rs
+++ b/pure/src/widget/text.rs
@@ -34,6 +34,7 @@ where
         &self,
         _tree: &Tree,
         renderer: &mut Renderer,
+        theme: &Renderer::Theme,
         style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
@@ -42,6 +43,7 @@ where
         <Self as iced_native::Widget<Message, Renderer>>::draw(
             self,
             renderer,
+            theme,
             style,
             layout,
             cursor_position,
diff --git a/pure/src/widget/text_input.rs b/pure/src/widget/text_input.rs
index 57ad26d9..7d768513 100644
--- a/pure/src/widget/text_input.rs
+++ b/pure/src/widget/text_input.rs
@@ -190,6 +190,7 @@ where
         &self,
         tree: &Tree,
         renderer: &mut Renderer,
+        theme: &Renderer::Theme,
         _style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
diff --git a/pure/src/widget/toggler.rs b/pure/src/widget/toggler.rs
index b9c5ec02..e08b5f47 100644
--- a/pure/src/widget/toggler.rs
+++ b/pure/src/widget/toggler.rs
@@ -38,6 +38,7 @@ where
         &self,
         _state: &Tree,
         renderer: &mut Renderer,
+        theme: &Renderer::Theme,
         style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
@@ -46,6 +47,7 @@ where
         <Self as iced_native::Widget<Message, Renderer>>::draw(
             self,
             renderer,
+            theme,
             style,
             layout,
             cursor_position,
diff --git a/pure/src/widget/tooltip.rs b/pure/src/widget/tooltip.rs
index 3887732a..15aa32fe 100644
--- a/pure/src/widget/tooltip.rs
+++ b/pure/src/widget/tooltip.rs
@@ -157,6 +157,7 @@ where
         &self,
         tree: &Tree,
         renderer: &mut Renderer,
+        theme: &Renderer::Theme,
         inherited_style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
@@ -165,6 +166,7 @@ where
         self.content.as_widget().draw(
             &tree.children[0],
             renderer,
+            theme,
             inherited_style,
             layout,
             cursor_position,
@@ -191,6 +193,7 @@ where
                     tooltip,
                     &Tree::empty(),
                     renderer,
+                    theme,
                     defaults,
                     layout,
                     cursor_position,
diff --git a/pure/src/widget/tree.rs b/pure/src/widget/tree.rs
index 0bb3107a..2f876523 100644
--- a/pure/src/widget/tree.rs
+++ b/pure/src/widget/tree.rs
@@ -31,7 +31,10 @@ impl Tree {
     /// Creates a new [`Tree`] for the provided [`Element`].
     pub fn new<'a, Message, Renderer>(
         widget: impl Borrow<dyn Widget<Message, Renderer> + 'a>,
-    ) -> Self {
+    ) -> Self
+    where
+        Renderer: iced_native::Renderer,
+    {
         let widget = widget.borrow();
 
         Self {
@@ -52,7 +55,9 @@ impl Tree {
     pub fn diff<'a, Message, Renderer>(
         &mut self,
         new: impl Borrow<dyn Widget<Message, Renderer> + 'a>,
-    ) {
+    ) where
+        Renderer: iced_native::Renderer,
+    {
         if self.tag == new.borrow().tag() {
             new.borrow().diff(self)
         } else {
@@ -64,7 +69,9 @@ impl Tree {
     pub fn diff_children<'a, Message, Renderer>(
         &mut self,
         new_children: &[impl Borrow<dyn Widget<Message, Renderer> + 'a>],
-    ) {
+    ) where
+        Renderer: iced_native::Renderer,
+    {
         self.diff_children_custom(
             new_children,
             |tree, widget| tree.diff(widget.borrow()),