Implement theme styling for `Canvas`

4 files changed, 63 insertions, 37 deletions

diff --git a/graphics/src/widget/canvas.rs b/graphics/src/widget/canvas.rs
index 0de08b01..c3e28e8c 100644
--- a/graphics/src/widget/canvas.rs
+++ b/graphics/src/widget/canvas.rs
@@ -62,10 +62,10 @@ use std::marker::PhantomData;
 /// ```no_run
 /// # mod iced {
 /// #     pub use iced_graphics::canvas;
-/// #     pub use iced_native::{Color, Rectangle};
+/// #     pub use iced_native::{Color, Rectangle, Theme};
 /// # }
 /// use iced::canvas::{self, Canvas, Cursor, Fill, Frame, Geometry, Path, Program};
-/// use iced::{Color, Rectangle};
+/// use iced::{Color, Rectangle, Theme};
 ///
 /// // First, we define the data we need for drawing
 /// #[derive(Debug)]
@@ -75,7 +75,7 @@ use std::marker::PhantomData;
 ///
 /// // Then, we implement the `Program` trait
 /// impl Program<()> for Circle {
-///     fn draw(&self, bounds: Rectangle, _cursor: Cursor) -> Vec<Geometry>{
+///     fn draw(&self, _theme: &Theme, bounds: Rectangle, _cursor: Cursor) -> Vec<Geometry>{
 ///         // We prepare a new `Frame`
 ///         let mut frame = Frame::new(bounds.size());
 ///
@@ -94,14 +94,21 @@ use std::marker::PhantomData;
 /// let canvas = Canvas::new(Circle { radius: 50.0 });
 /// ```
 #[derive(Debug)]
-pub struct Canvas<Message, P: Program<Message>> {
+pub struct Canvas<Message, Theme, P>
+where
+    P: Program<Message, Theme>,
+{
     width: Length,
     height: Length,
     program: P,
     message_: PhantomData<Message>,
+    theme_: PhantomData<Theme>,
 }
 
-impl<Message, P: Program<Message>> Canvas<Message, P> {
+impl<Message, Theme, P> Canvas<Message, Theme, P>
+where
+    P: Program<Message, Theme>,
+{
     const DEFAULT_SIZE: u16 = 100;
 
     /// Creates a new [`Canvas`].
@@ -111,6 +118,7 @@ impl<Message, P: Program<Message>> Canvas<Message, P> {
             height: Length::Units(Self::DEFAULT_SIZE),
             program,
             message_: PhantomData,
+            theme_: PhantomData,
         }
     }
 
@@ -127,9 +135,9 @@ impl<Message, P: Program<Message>> Canvas<Message, P> {
     }
 }
 
-impl<Message, P, B, T> Widget<Message, Renderer<B, T>> for Canvas<Message, P>
+impl<Message, P, B, T> Widget<Message, Renderer<B, T>> for Canvas<Message, T, P>
 where
-    P: Program<Message>,
+    P: Program<Message, T>,
     B: Backend,
 {
     fn width(&self) -> Length {
@@ -204,7 +212,7 @@ where
     fn draw(
         &self,
         renderer: &mut Renderer<B, T>,
-        _theme: &T,
+        theme: &T,
         _style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
@@ -225,7 +233,7 @@ where
             renderer.draw_primitive(Primitive::Group {
                 primitives: self
                     .program
-                    .draw(bounds, cursor)
+                    .draw(theme, bounds, cursor)
                     .into_iter()
                     .map(Geometry::into_primitive)
                     .collect(),
@@ -234,15 +242,16 @@ where
     }
 }
 
-impl<'a, Message, P, B, T> From<Canvas<Message, P>>
+impl<'a, Message, P, B, T> From<Canvas<Message, T, P>>
     for Element<'a, Message, Renderer<B, T>>
 where
     Message: 'static,
-    P: Program<Message> + 'a,
+    P: Program<Message, T> + 'a,
     B: Backend,
+    T: 'a,
 {
     fn from(
-        canvas: Canvas<Message, P>,
+        canvas: Canvas<Message, T, P>,
     ) -> Element<'a, Message, Renderer<B, T>> {
         Element::new(canvas)
     }
diff --git a/graphics/src/widget/canvas/program.rs b/graphics/src/widget/canvas/program.rs
index 85a2f67b..dddc387d 100644
--- a/graphics/src/widget/canvas/program.rs
+++ b/graphics/src/widget/canvas/program.rs
@@ -1,6 +1,8 @@
 use crate::canvas::event::{self, Event};
 use crate::canvas::{Cursor, Geometry};
-use iced_native::{mouse, Rectangle};
+
+use iced_native::mouse;
+use iced_native::Rectangle;
 
 /// The state and logic of a [`Canvas`].
 ///
@@ -8,7 +10,7 @@ use iced_native::{mouse, Rectangle};
 /// application.
 ///
 /// [`Canvas`]: crate::widget::Canvas
-pub trait Program<Message> {
+pub trait Program<Message, Theme = iced_native::Theme> {
     /// Updates the state of the [`Program`].
     ///
     /// When a [`Program`] is used in a [`Canvas`], the runtime will call this
@@ -36,7 +38,12 @@ pub trait Program<Message> {
     ///
     /// [`Frame`]: crate::widget::canvas::Frame
     /// [`Cache`]: crate::widget::canvas::Cache
-    fn draw(&self, bounds: Rectangle, cursor: Cursor) -> Vec<Geometry>;
+    fn draw(
+        &self,
+        theme: &Theme,
+        bounds: Rectangle,
+        cursor: Cursor,
+    ) -> Vec<Geometry>;
 
     /// Returns the current mouse interaction of the [`Program`].
     ///
@@ -53,9 +60,9 @@ pub trait Program<Message> {
     }
 }
 
-impl<T, Message> Program<Message> for &mut T
+impl<T, Message, Theme> Program<Message, Theme> for &mut T
 where
-    T: Program<Message>,
+    T: Program<Message, Theme>,
 {
     fn update(
         &mut self,
@@ -66,8 +73,13 @@ where
         T::update(self, event, bounds, cursor)
     }
 
-    fn draw(&self, bounds: Rectangle, cursor: Cursor) -> Vec<Geometry> {
-        T::draw(self, bounds, cursor)
+    fn draw(
+        &self,
+        theme: &Theme,
+        bounds: Rectangle,
+        cursor: Cursor,
+    ) -> Vec<Geometry> {
+        T::draw(self, theme, bounds, cursor)
     }
 
     fn mouse_interaction(
diff --git a/graphics/src/widget/pure/canvas.rs b/graphics/src/widget/pure/canvas.rs
index d53b20f6..d9c7e66b 100644
--- a/graphics/src/widget/pure/canvas.rs
+++ b/graphics/src/widget/pure/canvas.rs
@@ -30,10 +30,10 @@ use std::marker::PhantomData;
 /// #     pub mod pure {
 /// #         pub use iced_graphics::pure::canvas;
 /// #     }
-/// #     pub use iced_native::{Color, Rectangle};
+/// #     pub use iced_native::{Color, Rectangle, Theme};
 /// # }
 /// use iced::pure::canvas::{self, Canvas, Cursor, Fill, Frame, Geometry, Path, Program};
-/// use iced::{Color, Rectangle};
+/// use iced::{Color, Rectangle, Theme};
 ///
 /// // First, we define the data we need for drawing
 /// #[derive(Debug)]
@@ -45,7 +45,7 @@ use std::marker::PhantomData;
 /// impl Program<()> for Circle {
 ///     type State = ();
 ///
-///     fn draw(&self, _state: &(), bounds: Rectangle, _cursor: Cursor) -> Vec<Geometry>{
+///     fn draw(&self, _state: &(), _theme: &Theme, bounds: Rectangle, _cursor: Cursor) -> Vec<Geometry>{
 ///         // We prepare a new `Frame`
 ///         let mut frame = Frame::new(bounds.size());
 ///
@@ -64,19 +64,20 @@ use std::marker::PhantomData;
 /// let canvas = Canvas::new(Circle { radius: 50.0 });
 /// ```
 #[derive(Debug)]
-pub struct Canvas<Message, P>
+pub struct Canvas<Message, Theme, P>
 where
-    P: Program<Message>,
+    P: Program<Message, Theme>,
 {
     width: Length,
     height: Length,
     program: P,
     message_: PhantomData<Message>,
+    theme_: PhantomData<Theme>,
 }
 
-impl<Message, P> Canvas<Message, P>
+impl<Message, Theme, P> Canvas<Message, Theme, P>
 where
-    P: Program<Message>,
+    P: Program<Message, Theme>,
 {
     const DEFAULT_SIZE: u16 = 100;
 
@@ -87,6 +88,7 @@ where
             height: Length::Units(Self::DEFAULT_SIZE),
             program,
             message_: PhantomData,
+            theme_: PhantomData,
         }
     }
 
@@ -103,9 +105,9 @@ where
     }
 }
 
-impl<Message, P, B, T> Widget<Message, Renderer<B, T>> for Canvas<Message, P>
+impl<Message, P, B, T> Widget<Message, Renderer<B, T>> for Canvas<Message, T, P>
 where
-    P: Program<Message>,
+    P: Program<Message, T>,
     B: Backend,
 {
     fn tag(&self) -> tree::Tag {
@@ -194,7 +196,7 @@ where
         &self,
         tree: &Tree,
         renderer: &mut Renderer<B, T>,
-        _theme: &T,
+        theme: &T,
         _style: &renderer::Style,
         layout: Layout<'_>,
         cursor_position: Point,
@@ -216,7 +218,7 @@ where
             renderer.draw_primitive(Primitive::Group {
                 primitives: self
                     .program
-                    .draw(state, bounds, cursor)
+                    .draw(state, theme, bounds, cursor)
                     .into_iter()
                     .map(Geometry::into_primitive)
                     .collect(),
@@ -225,15 +227,16 @@ where
     }
 }
 
-impl<'a, Message, P, B, T> From<Canvas<Message, P>>
+impl<'a, Message, P, B, T> From<Canvas<Message, T, P>>
     for Element<'a, Message, Renderer<B, T>>
 where
     Message: 'a,
-    P: Program<Message> + 'a,
+    P: Program<Message, T> + 'a,
     B: Backend,
+    T: 'a,
 {
     fn from(
-        canvas: Canvas<Message, P>,
+        canvas: Canvas<Message, T, P>,
     ) -> Element<'a, Message, Renderer<B, T>> {
         Element::new(canvas)
     }
diff --git a/graphics/src/widget/pure/canvas/program.rs b/graphics/src/widget/pure/canvas/program.rs
index 058b364b..20c6406e 100644
--- a/graphics/src/widget/pure/canvas/program.rs
+++ b/graphics/src/widget/pure/canvas/program.rs
@@ -9,7 +9,7 @@ use crate::Rectangle;
 /// application.
 ///
 /// [`Canvas`]: crate::widget::Canvas
-pub trait Program<Message> {
+pub trait Program<Message, Theme = iced_native::Theme> {
     /// The internal state mutated by the [`Program`].
     type State: Default + 'static;
 
@@ -44,6 +44,7 @@ pub trait Program<Message> {
     fn draw(
         &self,
         state: &Self::State,
+        theme: &Theme,
         bounds: Rectangle,
         cursor: Cursor,
     ) -> Vec<Geometry>;
@@ -64,9 +65,9 @@ pub trait Program<Message> {
     }
 }
 
-impl<Message, T> Program<Message> for &T
+impl<Message, Theme, T> Program<Message, Theme> for &T
 where
-    T: Program<Message>,
+    T: Program<Message, Theme>,
 {
     type State = T::State;
 
@@ -83,10 +84,11 @@ where
     fn draw(
         &self,
         state: &Self::State,
+        theme: &Theme,
         bounds: Rectangle,
         cursor: Cursor,
     ) -> Vec<Geometry> {
-        T::draw(self, state, bounds, cursor)
+        T::draw(self, state, theme, bounds, cursor)
     }
 
     fn mouse_interaction(