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+//! 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;
+mod text;
+
+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};
+pub use text::Text;
+
+/// 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
+/// other in the same order they are pushed into the [`Canvas`].
+///
+/// [`Canvas`]: struct.Canvas.html
+/// [`Layer`]: layer/trait.Layer.html
+///
+/// # Examples
+/// The repository has a couple of [examples] showcasing how to use a
+/// [`Canvas`]:
+///
+/// - [`clock`], an application that uses the [`Canvas`] widget to draw a clock
+/// and its hands to display the current time.
+/// - [`solar_system`], an animated solar system drawn using the [`Canvas`] widget
+/// and showcasing how to compose different transforms.
+///
+/// [examples]: https://github.com/hecrj/iced/tree/0.1/examples
+/// [`clock`]: https://github.com/hecrj/iced/tree/0.1/examples/clock
+/// [`solar_system`]: https://github.com/hecrj/iced/tree/0.1/examples/solar_system
+///
+/// ## Drawing a simple circle
+/// If you want to get a quick overview, here's how we can draw a simple circle:
+///
+/// ```no_run
+/// # mod iced {
+/// # pub use iced_wgpu::canvas;
+/// # pub use iced_native::Color;
+/// # }
+/// use iced::canvas::{self, layer, Canvas, Drawable, Fill, Frame, Path};
+/// use iced::Color;
+///
+/// // First, we define the data we need for drawing
+/// #[derive(Debug)]
+/// struct Circle {
+/// radius: f32,
+/// }
+///
+/// // Then, we implement the `Drawable` trait
+/// impl Drawable for Circle {
+/// fn draw(&self, frame: &mut Frame) {
+/// // We create a `Path` representing a simple circle
+/// let circle = Path::new(|p| p.circle(frame.center(), self.radius));
+///
+/// // And fill it with some color
+/// frame.fill(&circle, Fill::Color(Color::BLACK));
+/// }
+/// }
+///
+/// // We can use a `Cache` to avoid unnecessary re-tessellation
+/// let cache: layer::Cache<Circle> = layer::Cache::new();
+///
+/// // Finally, we simply provide the data to our `Cache` and push the resulting
+/// // layer into a `Canvas`
+/// let canvas = Canvas::new()
+/// .push(cache.with(&Circle { radius: 50.0 }));
+/// ```
+#[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::Cached {
+ origin,
+ cache: 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)
+ }
+}