iced-yoda/examples/bezier_tool/src/main.rs

//! This example showcases an interactive `Canvas` for drawing Bézier curves.
use iced::{
    button, Align, Button, Column, Container, Element, Length, Sandbox,
    Settings, Text,
};

pub fn main() {
    Example::run(Settings {
        antialiasing: true,
        ..Settings::default()
    });
}

#[derive(Default)]
struct Example {
    bezier: bezier::State,
    curves: Vec<bezier::Curve>,
    button_state: button::State,
}

#[derive(Debug, Clone, Copy)]
enum Message {
    AddCurve(bezier::Curve),
    Clear,
}

impl Sandbox for Example {
    type Message = Message;

    fn new() -> Self {
        Example::default()
    }

    fn title(&self) -> String {
        String::from("Bezier tool - Iced")
    }

    fn update(&mut self, message: Message) {
        match message {
            Message::AddCurve(curve) => {
                self.curves.push(curve);
                self.bezier.request_redraw();
            }
            Message::Clear => {
                self.bezier = bezier::State::default();
                self.curves.clear();
            }
        }
    }

    fn view(&mut self) -> Element<Message> {
        let content = Column::new()
            .padding(20)
            .spacing(20)
            .align_items(Align::Center)
            .push(
                Text::new("Bezier tool example")
                    .width(Length::Shrink)
                    .size(50),
            )
            .push(self.bezier.view(&self.curves).map(Message::AddCurve))
            .push(
                Button::new(&mut self.button_state, Text::new("Clear"))
                    .padding(8)
                    .on_press(Message::Clear),
            );

        Container::new(content)
            .width(Length::Fill)
            .height(Length::Fill)
            .center_x()
            .center_y()
            .into()
    }
}

mod bezier {
    use iced::{
        canvas::{
            self, Canvas, Drawable, Event, Frame, Geometry, Path, Stroke,
        },
        mouse, ButtonState, Element, Length, Point, Size,
    };

    #[derive(Default)]
    pub struct State {
        pending: Option<Pending>,
        cursor_position: Point,
        cache: canvas::Cache,
    }

    impl State {
        pub fn view<'a>(
            &'a mut self,
            curves: &'a [Curve],
        ) -> Element<'a, Curve> {
            Canvas::new(Bezier {
                state: self,
                curves,
            })
            .width(Length::Fill)
            .height(Length::Fill)
            .into()
        }

        pub fn request_redraw(&mut self) {
            self.cache.clear()
        }
    }

    struct Bezier<'a> {
        state: &'a mut State,
        curves: &'a [Curve],
    }

    impl<'a> canvas::State<Curve> for Bezier<'a> {
        fn update(&mut self, event: Event, _bounds: Size) -> Option<Curve> {
            match event {
                Event::Mouse(mouse_event) => match mouse_event {
                    mouse::Event::CursorMoved { x, y } => {
                        self.state.cursor_position = Point::new(x, y);

                        None
                    }
                    mouse::Event::Input {
                        button: mouse::Button::Left,
                        state: ButtonState::Pressed,
                    } => match self.state.pending {
                        None => {
                            self.state.pending = Some(Pending::One {
                                from: self.state.cursor_position,
                            });
                            None
                        }
                        Some(Pending::One { from }) => {
                            self.state.pending = Some(Pending::Two {
                                from,
                                to: self.state.cursor_position,
                            });

                            None
                        }
                        Some(Pending::Two { from, to }) => {
                            self.state.pending = None;

                            Some(Curve {
                                from,
                                to,
                                control: self.state.cursor_position,
                            })
                        }
                    },
                    _ => None,
                },
            }
        }

        fn draw(&self, bounds: Size) -> Vec<Geometry> {
            let curves = self.state.cache.draw(bounds, &self.curves);

            if let Some(pending) = &self.state.pending {
                let pending_curve =
                    pending.draw(bounds, self.state.cursor_position);

                vec![curves, pending_curve]
            } else {
                vec![curves]
            }
        }
    }

    #[derive(Debug, Clone, Copy)]
    pub struct Curve {
        from: Point,
        to: Point,
        control: Point,
    }

    impl Drawable for Curve {
        fn draw(&self, frame: &mut Frame) {
            let curve = Path::new(|p| {
                p.move_to(self.from);
                p.quadratic_curve_to(self.control, self.to);
            });

            frame.stroke(&curve, Stroke::default().with_width(2.0));
        }
    }

    #[derive(Debug, Clone, Copy)]
    enum Pending {
        One { from: Point },
        Two { from: Point, to: Point },
    }

    impl Pending {
        fn draw(&self, bounds: Size, cursor_position: Point) -> Geometry {
            let mut frame = Frame::new(bounds);

            match *self {
                Pending::One { from } => {
                    let line = Path::line(from, cursor_position);
                    frame.stroke(&line, Stroke::default().with_width(2.0));
                }
                Pending::Two { from, to } => {
                    let curve = Curve {
                        from,
                        to,
                        control: cursor_position,
                    };

                    curve.draw(&mut frame);
                }
            };

            frame.into_geometry()
        }
    }
}