Draft Canvas types and clock example

wgpu/src/widget/canvas/data.rs

@@ -0,0 +1,20 @@
+#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
+pub struct Data<T> {
+    raw: T,
+    version: usize,
+}
+
+impl<T> Data<T> {
+    pub fn new(data: T) -> Self {
+        Data {
+            raw: data,
+            version: 0,
+        }
+    }
+
+    pub fn update(&mut self, f: impl FnOnce(&mut T)) {
+        f(&mut self.raw);
+
+        self.version += 1;
+    }
+}

wgpu/src/widget/canvas/frame.rs

@@ -0,0 +1,39 @@
+use iced_native::Point;
+
+use crate::{
+    canvas::{Fill, Path, Stroke},
+    triangle,
+};
+
+#[derive(Debug)]
+pub struct Frame {
+    width: u32,
+    height: u32,
+    buffers: lyon::tessellation::VertexBuffers<triangle::Vertex2D, u16>,
+}
+
+impl Frame {
+    pub(crate) fn new(width: u32, height: u32) -> Frame {
+        Frame {
+            width,
+            height,
+            buffers: lyon::tessellation::VertexBuffers::new(),
+        }
+    }
+
+    pub fn width(&self) -> u32 {
+        self.width
+    }
+
+    pub fn height(&self) -> u32 {
+        self.height
+    }
+
+    pub fn center(&self) -> Point {
+        Point::new(self.width as f32 / 2.0, self.height as f32 / 2.0)
+    }
+
+    pub fn fill(&mut self, path: Path, fill: Fill) {}
+
+    pub fn stroke(&mut self, path: Path, stroke: Stroke) {}
+}

wgpu/src/widget/canvas/layer.rs

@@ -0,0 +1,41 @@
+use crate::canvas::Frame;
+
+pub trait Layer: std::fmt::Debug {}
+
+use std::marker::PhantomData;
+use std::sync::{Arc, Weak};
+
+#[derive(Debug)]
+pub struct Cached<T: Drawable> {
+    input: PhantomData<T>,
+}
+
+impl<T> Cached<T>
+where
+    T: Drawable + std::fmt::Debug,
+{
+    pub fn new() -> Self {
+        Cached { input: PhantomData }
+    }
+
+    pub fn clear(&mut self) {}
+
+    pub fn with<'a>(&'a self, input: &'a T) -> impl Layer + 'a {
+        Bind {
+            cache: self,
+            input: input,
+        }
+    }
+}
+
+#[derive(Debug)]
+struct Bind<'a, T: Drawable> {
+    cache: &'a Cached<T>,
+    input: &'a T,
+}
+
+impl<'a, T> Layer for Bind<'a, T> where T: Drawable + std::fmt::Debug {}
+
+pub trait Drawable {
+    fn draw(&self, frame: &mut Frame);
+}

wgpu/src/widget/canvas/path.rs

@@ -0,0 +1,78 @@
+use iced_native::{Point, Vector};
+
+#[allow(missing_debug_implementations)]
+pub struct Path {
+    raw: lyon::path::Builder,
+}
+
+impl Path {
+    pub fn new() -> Path {
+        Path {
+            raw: lyon::path::Path::builder(),
+        }
+    }
+
+    #[inline]
+    pub fn move_to(&mut self, point: Point) {
+        let _ = self.raw.move_to(lyon::math::Point::new(point.x, point.y));
+    }
+
+    #[inline]
+    pub fn line_to(&mut self, point: Point) {
+        let _ = self.raw.line_to(lyon::math::Point::new(point.x, point.y));
+    }
+
+    #[inline]
+    pub fn arc(&mut self, arc: Arc) {
+        self.ellipse(arc.into())
+    }
+
+    #[inline]
+    pub fn ellipse(&mut self, ellipse: Ellipse) {
+        let arc = lyon::geom::Arc {
+            center: lyon::math::Point::new(ellipse.center.x, ellipse.center.y),
+            radii: lyon::math::Vector::new(ellipse.radii.x, ellipse.radii.y),
+            x_rotation: lyon::math::Angle::radians(ellipse.rotation),
+            start_angle: lyon::math::Angle::radians(ellipse.start_angle),
+            sweep_angle: lyon::math::Angle::radians(ellipse.end_angle),
+        };
+
+        arc.for_each_quadratic_bezier(&mut |curve| {
+            let _ = self.raw.quadratic_bezier_to(curve.ctrl, curve.to);
+        });
+    }
+
+    #[inline]
+    pub fn close(&mut self) {
+        self.raw.close()
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+pub struct Arc {
+    pub center: Point,
+    pub radius: f32,
+    pub start_angle: f32,
+    pub end_angle: f32,
+}
+
+#[derive(Debug, Clone, Copy)]
+pub struct Ellipse {
+    pub center: Point,
+    pub radii: Vector,
+    pub rotation: f32,
+    pub start_angle: f32,
+    pub end_angle: f32,
+}
+
+impl From<Arc> for Ellipse {
+    fn from(arc: Arc) -> Ellipse {
+        Ellipse {
+            center: arc.center,
+            radii: Vector::new(arc.radius, arc.radius),
+            rotation: 0.0,
+            start_angle: arc.start_angle,
+            end_angle: arc.end_angle,
+        }
+    }
+}