piston.rs

use piston_window::context::Context;
use piston_window::ellipse::circle;
use piston_window::{circle_arc, ellipse, line, rectangle, Event, Loop};
use piston_window::{G2d, PistonWindow};

use super::DummyBackendError;
use crate::drawing::backend::{BackendCoord, BackendStyle, DrawingBackend, DrawingErrorKind};
use crate::style::{Color, RGBAColor};

pub struct PistonBackend<'a, 'b> {
    size: (u32, u32),
    scale: f64,
    context: Context,
    graphics: &'b mut G2d<'a>,
}

fn make_piston_rgba(color: &RGBAColor) -> [f32; 4] {
    let (r, g, b) = color.rgb();
    let a = color.alpha();

    [
        r as f32 / 255.0,
        g as f32 / 255.0,
        b as f32 / 255.0,
        a as f32,
    ]
}
fn make_point_pair(a: BackendCoord, b: BackendCoord, scale: f64) -> [f64; 4] {
    [
        a.0 as f64 * scale,
        a.1 as f64 * scale,
        b.0 as f64 * scale,
        b.1 as f64 * scale,
    ]
}

fn make_circle(center: BackendCoord, radius: u32, scale: f64) -> [f64; 4] {
    circle(
        center.0 as f64 * scale,
        center.1 as f64 * scale,
        radius as f64 * scale,
    )
}

impl<'a, 'b> PistonBackend<'a, 'b> {
    pub fn new(size: (u32, u32), scale: f64, context: Context, graphics: &'b mut G2d<'a>) -> Self {
        Self {
            size,
            context,
            graphics,
            scale,
        }
    }
}

impl<'a, 'b> DrawingBackend for PistonBackend<'a, 'b> {
    type ErrorType = DummyBackendError;

    fn get_size(&self) -> (u32, u32) {
        self.size
    }

    fn ensure_prepared(&mut self) -> Result<(), DrawingErrorKind<DummyBackendError>> {
        Ok(())
    }

    fn present(&mut self) -> Result<(), DrawingErrorKind<DummyBackendError>> {
        Ok(())
    }

    fn draw_pixel(
        &mut self,
        point: BackendCoord,
        color: &RGBAColor,
    ) -> Result<(), DrawingErrorKind<Self::ErrorType>> {
        piston_window::rectangle(
            make_piston_rgba(color),
            make_point_pair(point, (1, 1), self.scale),
            self.context.transform,
            self.graphics,
        );
        Ok(())
    }

    fn draw_line<S: BackendStyle>(
        &mut self,
        from: BackendCoord,
        to: BackendCoord,
        style: &S,
    ) -> Result<(), DrawingErrorKind<Self::ErrorType>> {
        line(
            make_piston_rgba(&style.as_color()),
            self.scale,
            make_point_pair(from, to, self.scale),
            self.context.transform,
            self.graphics,
        );
        Ok(())
    }

    fn draw_rect<S: BackendStyle>(
        &mut self,
        upper_left: BackendCoord,
        bottom_right: BackendCoord,
        style: &S,
        fill: bool,
    ) -> Result<(), DrawingErrorKind<Self::ErrorType>> {
        if fill {
            rectangle(
                make_piston_rgba(&style.as_color()),
                make_point_pair(
                    upper_left,
                    (bottom_right.0 - upper_left.0, bottom_right.1 - upper_left.1),
                    self.scale,
                ),
                self.context.transform,
                self.graphics,
            );
        } else {
            let color = make_piston_rgba(&style.as_color());
            let [x0, y0, x1, y1] = make_point_pair(upper_left, bottom_right, self.scale);
            line(
                color,
                self.scale,
                [x0, y0, x0, y1],
                self.context.transform,
                self.graphics,
            );
            line(
                color,
                self.scale,
                [x0, y1, x1, y1],
                self.context.transform,
                self.graphics,
            );
            line(
                color,
                self.scale,
                [x1, y1, x1, y0],
                self.context.transform,
                self.graphics,
            );
            line(
                color,
                self.scale,
                [x1, y0, x0, y0],
                self.context.transform,
                self.graphics,
            );
        }
        Ok(())
    }

    fn draw_circle<S: BackendStyle>(
        &mut self,
        center: BackendCoord,
        radius: u32,
        style: &S,
        fill: bool,
    ) -> Result<(), DrawingErrorKind<Self::ErrorType>> {
        let rect = make_circle(center, radius, self.scale);
        if fill {
            ellipse(
                make_piston_rgba(&style.as_color()),
                rect,
                self.context.transform,
                self.graphics,
            );
        } else {
            circle_arc(
                make_piston_rgba(&style.as_color()),
                self.scale,
                std::f64::consts::PI,
                0.0,
                rect,
                self.context.transform,
                self.graphics,
            );
            circle_arc(
                make_piston_rgba(&style.as_color()),
                self.scale,
                0.0,
                std::f64::consts::PI,
                rect,
                self.context.transform,
                self.graphics,
            );
        }
        Ok(())
    }
}

#[allow(clippy::single_match)]
pub fn draw_piston_window<F: FnOnce(PistonBackend) -> Result<(), Box<dyn std::error::Error>>>(
    window: &mut PistonWindow,
    draw: F,
) -> Option<Event> {
    if let Some(event) = window.next() {
        window.draw_2d(&event, |c, g, _| match event {
            Event::Loop(Loop::Render(arg)) => {
                draw(PistonBackend::new(
                    (arg.draw_size[0], arg.draw_size[1]),
                    arg.window_size[0] / arg.draw_size[0] as f64,
                    c,
                    g,
                ))
                .ok();
            }
            _ => {}
        });
        return Some(event);
    }
    None
}

#[cfg(test)]
mod test {
    use super::*;
    #[test]
    fn test_make_circle() {
        assert_eq!(make_circle((1, 1), 0, 1.0), [1.0, 1.0, 0.0, 0.0]);
        assert_eq!(make_circle((1, 2), 3, 4.0), [-8.0, -4.0, 24.0, 24.0]);
    }
}