iced/wgpu/src/widget/canvas.rs

//! 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::{
    input::mouse, layout, Clipboard, Element, Hasher, Layout, Length,
    MouseCursor, Point, Size, Vector, Widget,
};
use std::hash::Hash;

pub mod path;

mod cache;
mod drawable;
mod event;
mod fill;
mod frame;
mod geometry;
mod state;
mod stroke;
mod text;

pub use cache::Cache;
pub use drawable::Drawable;
pub use event::Event;
pub use fill::Fill;
pub use frame::Frame;
pub use geometry::Geometry;
pub use path::Path;
pub use state::State;
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, Cache, 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::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 = Cache::new();
///
/// // Finally, we simply use our `Cache` to create the `Canvas`!
/// let canvas = Canvas::new(cache.with(Circle { radius: 50.0 }));
/// ```
#[derive(Debug)]
pub struct Canvas<S: State> {
    width: Length,
    height: Length,
    state: S,
}

impl<S: State> Canvas<S> {
    const DEFAULT_SIZE: u16 = 100;

    /// Creates a new [`Canvas`] with no layers.
    ///
    /// [`Canvas`]: struct.Canvas.html
    pub fn new(state: S) -> Self {
        Canvas {
            width: Length::Units(Self::DEFAULT_SIZE),
            height: Length::Units(Self::DEFAULT_SIZE),
            state,
        }
    }

    /// 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
    }
}

impl<Message, S: State> Widget<Message, Renderer> for Canvas<S> {
    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 on_event(
        &mut self,
        event: iced_native::Event,
        layout: Layout<'_>,
        cursor_position: Point,
        _messages: &mut Vec<Message>,
        _renderer: &Renderer,
        _clipboard: Option<&dyn Clipboard>,
    ) {
        let bounds = layout.bounds();

        let canvas_event = match event {
            iced_native::Event::Mouse(mouse_event) => {
                Some(Event::Mouse(match mouse_event {
                    mouse::Event::CursorMoved { .. } => {
                        mouse::Event::CursorMoved {
                            x: cursor_position.x - bounds.x,
                            y: cursor_position.y - bounds.y,
                        }
                    }
                    _ => mouse_event,
                }))
            }
            _ => None,
        };

        if let Some(canvas_event) = canvas_event {
            self.state.update(canvas_event, bounds.size())
        }
    }

    fn draw(
        &self,
        _renderer: &mut Renderer,
        _defaults: &Defaults,
        layout: Layout<'_>,
        _cursor_position: Point,
    ) -> (Primitive, MouseCursor) {
        let bounds = layout.bounds();
        let translation = Vector::new(bounds.x, bounds.y);
        let size = Size::new(bounds.width, bounds.height);

        (
            Primitive::Translate {
                translation,
                content: Box::new(Primitive::Group {
                    primitives: self
                        .state
                        .draw(size)
                        .into_iter()
                        .map(Geometry::into_primitive)
                        .collect(),
                }),
            },
            MouseCursor::Idle,
        )
    }

    fn hash_layout(&self, state: &mut Hasher) {
        struct Marker;
        std::any::TypeId::of::<Marker>().hash(state);

        self.width.hash(state);
        self.height.hash(state);
    }
}

impl<'a, Message, S: State + 'a> From<Canvas<S>>
    for Element<'a, Message, Renderer>
where
    Message: 'static,
{
    fn from(canvas: Canvas<S>) -> Element<'a, Message, Renderer> {
        Element::new(canvas)
    }
}