1 files changed, 149 insertions, 0 deletions
diff --git a/wgpu/src/widget/canvas.rs b/wgpu/src/widget/canvas.rs
new file mode 100644
index 00000000..38c1ce62
--- /dev/null
+++ b/wgpu/src/widget/canvas.rs
@@ -0,0 +1,149 @@
+//! Draw 2D graphics for your users.
+//!
+//! A [`Canvas`] widget can be used to draw different kinds of 2D shapes in a
+//! [`Frame`]. It can be used for animation, data visualization, game graphics,
+//! and more!
+//!
+//! [`Canvas`]: struct.Canvas.html
+//! [`Frame`]: struct.Frame.html
+use crate::{Defaults, Primitive, Renderer};
+
+use iced_native::{
+    layout, Element, Hasher, Layout, Length, MouseCursor, Point, Size, Widget,
+};
+use std::hash::Hash;
+
+pub mod layer;
+pub mod path;
+
+mod drawable;
+mod fill;
+mod frame;
+mod stroke;
+
+pub use drawable::Drawable;
+pub use fill::Fill;
+pub use frame::Frame;
+pub use layer::Layer;
+pub use path::Path;
+pub use stroke::{LineCap, LineJoin, Stroke};
+
+/// A widget capable of drawing 2D graphics.
+///
+/// A [`Canvas`] may contain multiple layers. A [`Layer`] is drawn using the
+/// painter's algorithm. In other words, layers will be drawn on top of each in
+/// the same order they are pushed into the [`Canvas`].
+///
+/// [`Canvas`]: struct.Canvas.html
+/// [`Layer`]: layer/trait.Layer.html
+#[derive(Debug)]
+pub struct Canvas<'a> {
+    width: Length,
+    height: Length,
+    layers: Vec<Box<dyn Layer + 'a>>,
+}
+
+impl<'a> Canvas<'a> {
+    const DEFAULT_SIZE: u16 = 100;
+
+    /// Creates a new [`Canvas`] with no layers.
+    ///
+    /// [`Canvas`]: struct.Canvas.html
+    pub fn new() -> Self {
+        Canvas {
+            width: Length::Units(Self::DEFAULT_SIZE),
+            height: Length::Units(Self::DEFAULT_SIZE),
+            layers: Vec::new(),
+        }
+    }
+
+    /// Sets the width of the [`Canvas`].
+    ///
+    /// [`Canvas`]: struct.Canvas.html
+    pub fn width(mut self, width: Length) -> Self {
+        self.width = width;
+        self
+    }
+
+    /// Sets the height of the [`Canvas`].
+    ///
+    /// [`Canvas`]: struct.Canvas.html
+    pub fn height(mut self, height: Length) -> Self {
+        self.height = height;
+        self
+    }
+
+    /// Adds a [`Layer`] to the [`Canvas`].
+    ///
+    /// It will be drawn on top of previous layers.
+    ///
+    /// [`Layer`]: layer/trait.Layer.html
+    /// [`Canvas`]: struct.Canvas.html
+    pub fn push(mut self, layer: impl Layer + 'a) -> Self {
+        self.layers.push(Box::new(layer));
+        self
+    }
+}
+
+impl<'a, Message> Widget<Message, Renderer> for Canvas<'a> {
+    fn width(&self) -> Length {
+        self.width
+    }
+
+    fn height(&self) -> Length {
+        self.height
+    }
+
+    fn layout(
+        &self,
+        _renderer: &Renderer,
+        limits: &layout::Limits,
+    ) -> layout::Node {
+        let limits = limits.width(self.width).height(self.height);
+        let size = limits.resolve(Size::ZERO);
+
+        layout::Node::new(size)
+    }
+
+    fn draw(
+        &self,
+        _renderer: &mut Renderer,
+        _defaults: &Defaults,
+        layout: Layout<'_>,
+        _cursor_position: Point,
+    ) -> (Primitive, MouseCursor) {
+        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) {
+        std::any::TypeId::of::<Canvas<'static>>().hash(state);
+
+        self.width.hash(state);
+        self.height.hash(state);
+    }
+}
+
+impl<'a, Message> From<Canvas<'a>> for Element<'a, Message, Renderer>
+where
+    Message: 'static,
+{
+    fn from(canvas: Canvas<'a>) -> Element<'a, Message, Renderer> {
+        Element::new(canvas)
+    }
+}