Draft new `iced_graphics` crate :tada:

1 files changed, 236 insertions, 0 deletions

diff --git a/graphics/src/widget/canvas.rs b/graphics/src/widget/canvas.rs
new file mode 100644
index 00000000..d393a5c5
--- /dev/null
+++ b/graphics/src/widget/canvas.rs
@@ -0,0 +1,236 @@
+//! 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::{Backend, Defaults, Primitive, Renderer};
+use iced_native::{
+    layout, mouse, Clipboard, Element, Hasher, Layout, Length, Point, Size,
+    Vector, Widget,
+};
+use std::hash::Hash;
+use std::marker::PhantomData;
+
+pub mod path;
+
+mod cache;
+mod cursor;
+mod event;
+mod fill;
+mod frame;
+mod geometry;
+mod program;
+mod stroke;
+mod text;
+
+pub use cache::Cache;
+pub use cursor::Cursor;
+pub use event::Event;
+pub use fill::Fill;
+pub use frame::Frame;
+pub use geometry::Geometry;
+pub use path::Path;
+pub use program::Program;
+pub use stroke::{LineCap, LineJoin, Stroke};
+pub use text::Text;
+
+/// A widget capable of drawing 2D graphics.
+///
+/// [`Canvas`]: struct.Canvas.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.
+/// - [`game_of_life`], an interactive version of the Game of Life, invented by
+/// John Conway.
+/// - [`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/master/examples
+/// [`clock`]: https://github.com/hecrj/iced/tree/master/examples/clock
+/// [`game_of_life`]: https://github.com/hecrj/iced/tree/master/examples/game_of_life
+/// [`solar_system`]: https://github.com/hecrj/iced/tree/master/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_graphics::canvas;
+/// #     pub use iced_native::{Color, Rectangle};
+/// # }
+/// use iced::canvas::{self, Canvas, Cursor, Fill, Frame, Geometry, Path, Program};
+/// use iced::{Color, Rectangle};
+///
+/// // First, we define the data we need for drawing
+/// #[derive(Debug)]
+/// struct Circle {
+///     radius: f32,
+/// }
+///
+/// // Then, we implement the `Program` trait
+/// impl Program<()> for Circle {
+///     fn draw(&self, bounds: Rectangle, _cursor: Cursor) -> Vec<Geometry>{
+///         // We prepare a new `Frame`
+///         let mut frame = Frame::new(bounds.size());
+///
+///         // 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));
+///
+///         // Finally, we produce the geometry
+///         vec![frame.into_geometry()]
+///     }
+/// }
+///
+/// // Finally, we simply use our `Circle` to create the `Canvas`!
+/// let canvas = Canvas::new(Circle { radius: 50.0 });
+/// ```
+#[derive(Debug)]
+pub struct Canvas<Message, P: Program<Message>> {
+    width: Length,
+    height: Length,
+    program: P,
+    phantom: PhantomData<Message>,
+}
+
+impl<Message, P: Program<Message>> Canvas<Message, P> {
+    const DEFAULT_SIZE: u16 = 100;
+
+    /// Creates a new [`Canvas`].
+    ///
+    /// [`Canvas`]: struct.Canvas.html
+    pub fn new(program: P) -> Self {
+        Canvas {
+            width: Length::Units(Self::DEFAULT_SIZE),
+            height: Length::Units(Self::DEFAULT_SIZE),
+            program,
+            phantom: PhantomData,
+        }
+    }
+
+    /// 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, P, B> Widget<Message, Renderer<B>> for Canvas<Message, P>
+where
+    P: Program<Message>,
+    B: Backend,
+{
+    fn width(&self) -> Length {
+        self.width
+    }
+
+    fn height(&self) -> Length {
+        self.height
+    }
+
+    fn layout(
+        &self,
+        _renderer: &Renderer<B>,
+        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<B>,
+        _clipboard: Option<&dyn Clipboard>,
+    ) {
+        let bounds = layout.bounds();
+
+        let canvas_event = match event {
+            iced_native::Event::Mouse(mouse_event) => {
+                Some(Event::Mouse(mouse_event))
+            }
+            _ => None,
+        };
+
+        let cursor = Cursor::from_window_position(cursor_position);
+
+        if let Some(canvas_event) = canvas_event {
+            if let Some(message) =
+                self.program.update(canvas_event, bounds, cursor)
+            {
+                messages.push(message);
+            }
+        }
+    }
+
+    fn draw(
+        &self,
+        _renderer: &mut Renderer<B>,
+        _defaults: &Defaults,
+        layout: Layout<'_>,
+        cursor_position: Point,
+    ) -> (Primitive, mouse::Interaction) {
+        let bounds = layout.bounds();
+        let translation = Vector::new(bounds.x, bounds.y);
+        let cursor = Cursor::from_window_position(cursor_position);
+
+        (
+            Primitive::Translate {
+                translation,
+                content: Box::new(Primitive::Group {
+                    primitives: self
+                        .program
+                        .draw(bounds, cursor)
+                        .into_iter()
+                        .map(Geometry::into_primitive)
+                        .collect(),
+                }),
+            },
+            self.program.mouse_interaction(bounds, cursor),
+        )
+    }
+
+    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, P, B> From<Canvas<Message, P>>
+    for Element<'a, Message, Renderer<B>>
+where
+    Message: 'static,
+    P: Program<Message> + 'a,
+    B: Backend,
+{
+    fn from(canvas: Canvas<Message, P>) -> Element<'a, Message, Renderer<B>> {
+        Element::new(canvas)
+    }
+}