Finish `clock` example

11 files changed, 202 insertions, 78 deletions

diff --git a/examples/clock/Cargo.toml b/examples/clock/Cargo.toml
index 941e2bd0..308cbfbb 100644
--- a/examples/clock/Cargo.toml
+++ b/examples/clock/Cargo.toml
@@ -9,5 +9,7 @@ publish = false
 canvas = []
 
 [dependencies]
-iced = { path = "../..", features = ["canvas", "async-std"] }
+iced = { path = "../..", features = ["canvas", "async-std", "debug"] }
+iced_native = { path = "../../native" }
 chrono = "0.4"
+async-std = { version = "1.0", features = ["unstable"] }
diff --git a/examples/clock/src/main.rs b/examples/clock/src/main.rs
index 76752d20..1b8d1ee6 100644
--- a/examples/clock/src/main.rs
+++ b/examples/clock/src/main.rs
@@ -1,6 +1,6 @@
 use iced::{
-    canvas, executor, Application, Canvas, Color, Command, Element, Length,
-    Point, Settings,
+    canvas, executor, Application, Canvas, Color, Command, Container, Element,
+    Length, Point, Settings, Subscription, Vector,
 };
 
 pub fn main() {
@@ -53,11 +53,21 @@ impl Application for Clock {
         Command::none()
     }
 
+    fn subscription(&self) -> Subscription<Message> {
+        time::every(std::time::Duration::from_millis(500)).map(Message::Tick)
+    }
+
     fn view(&mut self) -> Element<Message> {
-        Canvas::new()
+        let canvas = Canvas::new()
+            .width(Length::Units(400))
+            .height(Length::Units(400))
+            .push(self.clock.with(&self.now));
+
+        Container::new(canvas)
             .width(Length::Fill)
             .height(Length::Fill)
-            .push(self.clock.with(&self.now))
+            .center_x()
+            .center_y()
             .into()
     }
 }
@@ -85,6 +95,7 @@ impl canvas::layer::Drawable for LocalTime {
     fn draw(&self, frame: &mut canvas::Frame) {
         let center = frame.center();
         let radius = frame.width().min(frame.height()) as f32 / 2.0;
+        let offset = Vector::new(center.x, center.y);
 
         let path = canvas::Path::new(|path| {
             path.arc(canvas::path::Arc {
@@ -104,6 +115,7 @@ impl canvas::layer::Drawable for LocalTime {
             n: u32,
             total: u32,
             length: f32,
+            offset: Vector,
             path: &mut canvas::path::Builder,
         ) {
             let turns = n as f32 / total as f32;
@@ -112,15 +124,15 @@ impl canvas::layer::Drawable for LocalTime {
             let x = length * t.cos();
             let y = length * t.sin();
 
-            path.line_to(Point::new(x, y));
+            path.line_to(Point::new(x, y) + offset);
         }
 
         let path = canvas::Path::new(|path| {
             path.move_to(center);
-            draw_handle(self.hour, 12, 0.6 * radius, path);
+            draw_handle(self.hour, 12, 0.5 * radius, offset, path);
 
             path.move_to(center);
-            draw_handle(self.minute, 60, 0.9 * radius, path)
+            draw_handle(self.minute, 60, 0.8 * radius, offset, path)
         });
 
         frame.stroke(
@@ -135,7 +147,7 @@ impl canvas::layer::Drawable for LocalTime {
 
         let path = canvas::Path::new(|path| {
             path.move_to(center);
-            draw_handle(self.second, 60, 0.9 * radius, path)
+            draw_handle(self.second, 60, 0.8 * radius, offset, path)
         });
 
         frame.stroke(
@@ -149,3 +161,40 @@ impl canvas::layer::Drawable for LocalTime {
         );
     }
 }
+
+mod time {
+    use iced::futures;
+
+    pub fn every(
+        duration: std::time::Duration,
+    ) -> iced::Subscription<chrono::DateTime<chrono::Local>> {
+        iced::Subscription::from_recipe(Every(duration))
+    }
+
+    struct Every(std::time::Duration);
+
+    impl<H, I> iced_native::subscription::Recipe<H, I> for Every
+    where
+        H: std::hash::Hasher,
+    {
+        type Output = chrono::DateTime<chrono::Local>;
+
+        fn hash(&self, state: &mut H) {
+            use std::hash::Hash;
+
+            std::any::TypeId::of::<Self>().hash(state);
+            self.0.hash(state);
+        }
+
+        fn stream(
+            self: Box<Self>,
+            _input: futures::stream::BoxStream<'static, I>,
+        ) -> futures::stream::BoxStream<'static, Self::Output> {
+            use futures::stream::StreamExt;
+
+            async_std::stream::interval(self.0)
+                .map(|_| chrono::Local::now())
+                .boxed()
+        }
+    }
+}
diff --git a/wgpu/src/primitive.rs b/wgpu/src/primitive.rs
index 481252ef..823b4b72 100644
--- a/wgpu/src/primitive.rs
+++ b/wgpu/src/primitive.rs
@@ -1,5 +1,5 @@
 use iced_native::{
-    image, svg, Background, Color, Font, HorizontalAlignment, Rectangle,
+    image, svg, Background, Color, Font, HorizontalAlignment, Point, Rectangle,
     Vector, VerticalAlignment,
 };
 
@@ -73,7 +73,13 @@ pub enum Primitive {
     /// A low-level primitive to render a mesh of triangles.
     ///
     /// It can be used to render many kinds of geometry freely.
-    Mesh2D(Arc<triangle::Mesh2D>),
+    Mesh2D {
+        /// The top-left coordinate of the mesh
+        origin: Point,
+
+        /// The vertex and index buffers of the mesh
+        buffers: Arc<triangle::Mesh2D>,
+    },
 }
 
 impl Default for Primitive {
diff --git a/wgpu/src/renderer.rs b/wgpu/src/renderer.rs
index e93090b8..25b2e99a 100644
--- a/wgpu/src/renderer.rs
+++ b/wgpu/src/renderer.rs
@@ -26,7 +26,7 @@ struct Layer<'a> {
     offset: Vector<u32>,
     quads: Vec<Quad>,
     images: Vec<Image>,
-    meshes: Vec<Arc<triangle::Mesh2D>>,
+    meshes: Vec<(Point, Arc<triangle::Mesh2D>)>,
     text: Vec<wgpu_glyph::Section<'a>>,
 }
 
@@ -229,8 +229,8 @@ impl Renderer {
                     scale: [bounds.width, bounds.height],
                 });
             }
-            Primitive::Mesh2D(mesh) => {
-                layer.meshes.push(mesh.clone());
+            Primitive::Mesh2D { origin, buffers } => {
+                layer.meshes.push((*origin, buffers.clone()));
             }
             Primitive::Clip {
                 bounds,
@@ -313,9 +313,10 @@ impl Renderer {
 
         if layer.meshes.len() > 0 {
             let translated = transformation
+                * Transformation::scale(scale_factor, scale_factor)
                 * Transformation::translate(
-                    -(layer.offset.x as f32) * scale_factor,
-                    -(layer.offset.y as f32) * scale_factor,
+                    -(layer.offset.x as f32),
+                    -(layer.offset.y as f32),
                 );
 
             self.triangle_pipeline.draw(
@@ -323,7 +324,6 @@ impl Renderer {
                 encoder,
                 target,
                 translated,
-                scale_factor,
                 &layer.meshes,
                 bounds,
             );
diff --git a/wgpu/src/shader/triangle.vert b/wgpu/src/shader/triangle.vert
index fd86ecd6..1f2c009b 100644
--- a/wgpu/src/shader/triangle.vert
+++ b/wgpu/src/shader/triangle.vert
@@ -7,11 +7,9 @@ layout(location = 0) out vec4 o_Color;
 
 layout (set = 0, binding = 0) uniform Globals {
     mat4 u_Transform;
-    float u_Scale;
 };
 
 void main() {
-    vec2 p_Position = i_Position * u_Scale;
-    gl_Position = u_Transform * vec4(p_Position, 0.0, 1.0);
+    gl_Position = u_Transform * vec4(i_Position, 0.0, 1.0);
     o_Color = i_Color;
 }
diff --git a/wgpu/src/shader/triangle.vert.spv b/wgpu/src/shader/triangle.vert.spv
index bc39c451..871f4f55 100644
--- a/wgpu/src/shader/triangle.vert.spv
+++ b/wgpu/src/shader/triangle.vert.spv
diff --git a/wgpu/src/triangle.rs b/wgpu/src/triangle.rs
index 38157d00..6f3adbe4 100644
--- a/wgpu/src/triangle.rs
+++ b/wgpu/src/triangle.rs
@@ -1,6 +1,6 @@
 //! Draw meshes of triangles.
 use crate::Transformation;
-use iced_native::Rectangle;
+use iced_native::{Point, Rectangle};
 use std::{mem, sync::Arc};
 
 #[derive(Debug)]
@@ -128,47 +128,28 @@ impl Pipeline {
         encoder: &mut wgpu::CommandEncoder,
         target: &wgpu::TextureView,
         transformation: Transformation,
-        scale: f32,
-        meshes: &Vec<Arc<Mesh2D>>,
+        meshes: &Vec<(Point, Arc<Mesh2D>)>,
         bounds: Rectangle<u32>,
     ) {
-        let uniforms = Uniforms {
-            transform: transformation.into(),
-            scale,
-        };
-
-        let constants_buffer = device
-            .create_buffer_mapped(1, wgpu::BufferUsage::COPY_SRC)
-            .fill_from_slice(&[uniforms]);
-
-        encoder.copy_buffer_to_buffer(
-            &constants_buffer,
-            0,
-            &self.constants_buffer,
-            0,
-            std::mem::size_of::<Uniforms>() as u64,
-        );
-
-        let mut render_pass =
-            encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
-                color_attachments: &[
-                    wgpu::RenderPassColorAttachmentDescriptor {
-                        attachment: target,
-                        resolve_target: None,
-                        load_op: wgpu::LoadOp::Load,
-                        store_op: wgpu::StoreOp::Store,
-                        clear_color: wgpu::Color {
-                            r: 0.0,
-                            g: 0.0,
-                            b: 0.0,
-                            a: 0.0,
-                        },
-                    },
-                ],
-                depth_stencil_attachment: None,
-            });
+        for (origin, mesh) in meshes {
+            let uniforms = Uniforms {
+                transform: (transformation
+                    * Transformation::translate(origin.x, origin.y))
+                .into(),
+            };
+
+            let constants_buffer = device
+                .create_buffer_mapped(1, wgpu::BufferUsage::COPY_SRC)
+                .fill_from_slice(&[uniforms]);
+
+            encoder.copy_buffer_to_buffer(
+                &constants_buffer,
+                0,
+                &self.constants_buffer,
+                0,
+                std::mem::size_of::<Uniforms>() as u64,
+            );
 
-        for mesh in meshes {
             let vertices_buffer = device
                 .create_buffer_mapped(
                     mesh.vertices.len(),
@@ -183,6 +164,25 @@ impl Pipeline {
                 )
                 .fill_from_slice(&mesh.indices);
 
+            let mut render_pass =
+                encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
+                    color_attachments: &[
+                        wgpu::RenderPassColorAttachmentDescriptor {
+                            attachment: target,
+                            resolve_target: None,
+                            load_op: wgpu::LoadOp::Load,
+                            store_op: wgpu::StoreOp::Store,
+                            clear_color: wgpu::Color {
+                                r: 0.0,
+                                g: 0.0,
+                                b: 0.0,
+                                a: 0.0,
+                            },
+                        },
+                    ],
+                    depth_stencil_attachment: None,
+                });
+
             render_pass.set_pipeline(&self.pipeline);
             render_pass.set_bind_group(0, &self.constants, &[]);
             render_pass.set_index_buffer(&indices_buffer, 0);
@@ -203,14 +203,12 @@ impl Pipeline {
 #[derive(Debug, Clone, Copy)]
 struct Uniforms {
     transform: [f32; 16],
-    scale: f32,
 }
 
 impl Default for Uniforms {
     fn default() -> Self {
         Self {
             transform: *Transformation::identity().as_ref(),
-            scale: 1.0,
         }
     }
 }
diff --git a/wgpu/src/widget/canvas.rs b/wgpu/src/widget/canvas.rs
index 6bfeed9a..c984fee9 100644
--- a/wgpu/src/widget/canvas.rs
+++ b/wgpu/src/widget/canvas.rs
@@ -68,7 +68,6 @@ impl<'a, Message> Widget<Message, Renderer> for Canvas<'a> {
         limits: &layout::Limits,
     ) -> layout::Node {
         let limits = limits.width(self.width).height(self.height);
-
         let size = limits.resolve(Size::ZERO);
 
         layout::Node::new(size)
@@ -78,10 +77,26 @@ impl<'a, Message> Widget<Message, Renderer> for Canvas<'a> {
         &self,
         _renderer: &mut Renderer,
         _defaults: &Defaults,
-        _layout: Layout<'_>,
+        layout: Layout<'_>,
         _cursor_position: Point,
     ) -> (Primitive, MouseCursor) {
-        (Primitive::None, MouseCursor::Idle)
+        let bounds = layout.bounds();
+        let origin = Point::new(bounds.x, bounds.y);
+        let size = Size::new(bounds.width, bounds.height);
+
+        (
+            Primitive::Group {
+                primitives: self
+                    .layers
+                    .iter()
+                    .map(|layer| Primitive::Mesh2D {
+                        origin,
+                        buffers: layer.draw(size),
+                    })
+                    .collect(),
+            },
+            MouseCursor::Idle,
+        )
     }
 
     fn hash_layout(&self, state: &mut Hasher) {
diff --git a/wgpu/src/widget/canvas/frame.rs b/wgpu/src/widget/canvas/frame.rs
index 82ff526b..3c667426 100644
--- a/wgpu/src/widget/canvas/frame.rs
+++ b/wgpu/src/widget/canvas/frame.rs
@@ -7,13 +7,13 @@ use crate::{
 
 #[derive(Debug)]
 pub struct Frame {
-    width: u32,
-    height: u32,
+    width: f32,
+    height: f32,
     buffers: lyon::tessellation::VertexBuffers<triangle::Vertex2D, u16>,
 }
 
 impl Frame {
-    pub(crate) fn new(width: u32, height: u32) -> Frame {
+    pub fn new(width: f32, height: f32) -> Frame {
         Frame {
             width,
             height,
@@ -21,16 +21,16 @@ impl Frame {
         }
     }
 
-    pub fn width(&self) -> u32 {
+    pub fn width(&self) -> f32 {
         self.width
     }
 
-    pub fn height(&self) -> u32 {
+    pub fn height(&self) -> f32 {
         self.height
     }
 
     pub fn center(&self) -> Point {
-        Point::new(self.width as f32 / 2.0, self.height as f32 / 2.0)
+        Point::new(self.width / 2.0, self.height / 2.0)
     }
 
     pub fn fill(&mut self, path: &Path, fill: Fill) {
@@ -74,6 +74,13 @@ impl Frame {
             .tessellate_path(path.raw(), &options, &mut buffers)
             .expect("Stroke path");
     }
+
+    pub fn into_mesh(self) -> triangle::Mesh2D {
+        triangle::Mesh2D {
+            vertices: self.buffers.vertices,
+            indices: self.buffers.indices,
+        }
+    }
 }
 
 struct FillVertex([f32; 4]);
diff --git a/wgpu/src/widget/canvas/layer.rs b/wgpu/src/widget/canvas/layer.rs
index f97634e4..c239a254 100644
--- a/wgpu/src/widget/canvas/layer.rs
+++ b/wgpu/src/widget/canvas/layer.rs
@@ -1,13 +1,28 @@
-use crate::canvas::Frame;
+use crate::{canvas::Frame, triangle};
 
-pub trait Layer: std::fmt::Debug {}
+use iced_native::Size;
+use std::cell::RefCell;
+use std::sync::Arc;
+
+pub trait Layer: std::fmt::Debug {
+    fn draw(&self, bounds: Size) -> Arc<triangle::Mesh2D>;
+}
 
 use std::marker::PhantomData;
-use std::sync::{Arc, Weak};
 
 #[derive(Debug)]
 pub struct Cached<T: Drawable> {
     input: PhantomData<T>,
+    cache: RefCell<Cache>,
+}
+
+#[derive(Debug)]
+enum Cache {
+    Empty,
+    Filled {
+        mesh: Arc<triangle::Mesh2D>,
+        bounds: Size,
+    },
 }
 
 impl<T> Cached<T>
@@ -15,14 +30,19 @@ where
     T: Drawable + std::fmt::Debug,
 {
     pub fn new() -> Self {
-        Cached { input: PhantomData }
+        Cached {
+            input: PhantomData,
+            cache: RefCell::new(Cache::Empty),
+        }
     }
 
-    pub fn clear(&mut self) {}
+    pub fn clear(&mut self) {
+        *self.cache.borrow_mut() = Cache::Empty;
+    }
 
     pub fn with<'a>(&'a self, input: &'a T) -> impl Layer + 'a {
         Bind {
-            cache: self,
+            layer: self,
             input: input,
         }
     }
@@ -30,11 +50,38 @@ where
 
 #[derive(Debug)]
 struct Bind<'a, T: Drawable> {
-    cache: &'a Cached<T>,
+    layer: &'a Cached<T>,
     input: &'a T,
 }
 
-impl<'a, T> Layer for Bind<'a, T> where T: Drawable + std::fmt::Debug {}
+impl<'a, T> Layer for Bind<'a, T>
+where
+    T: Drawable + std::fmt::Debug,
+{
+    fn draw(&self, current_bounds: Size) -> Arc<triangle::Mesh2D> {
+        use std::ops::Deref;
+
+        if let Cache::Filled { mesh, bounds } =
+            self.layer.cache.borrow().deref()
+        {
+            if *bounds == current_bounds {
+                return mesh.clone();
+            }
+        }
+
+        let mut frame = Frame::new(current_bounds.width, current_bounds.height);
+        self.input.draw(&mut frame);
+
+        let mesh = Arc::new(frame.into_mesh());
+
+        *self.layer.cache.borrow_mut() = Cache::Filled {
+            mesh: mesh.clone(),
+            bounds: current_bounds,
+        };
+
+        mesh
+    }
+}
 
 pub trait Drawable {
     fn draw(&self, frame: &mut Frame);
diff --git a/wgpu/src/widget/canvas/path.rs b/wgpu/src/widget/canvas/path.rs
index 96206256..c8ba10e1 100644
--- a/wgpu/src/widget/canvas/path.rs
+++ b/wgpu/src/widget/canvas/path.rs
@@ -58,6 +58,8 @@ impl Builder {
             sweep_angle: lyon::math::Angle::radians(ellipse.end_angle),
         };
 
+        let _ = self.raw.move_to(arc.sample(0.0));
+
         arc.for_each_quadratic_bezier(&mut |curve| {
             let _ = self.raw.quadratic_bezier_to(curve.ctrl, curve.to);
         });