graphics-shapes 0.5.1

Shapes for graphics
Documentation 
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use crate::Coord;

/// Scale `points` (move them towards or away) around the `center` by `factor`
///
/// The resulting points distance will be `points[x].distance(center) * factor` but at the same angle
#[must_use]
pub fn scale_points(center: Coord, points: &[Coord], factor: f32) -> Vec<Coord> {
    let mut output = vec![];
    for point in points {
        let angle = center.angle_to(*point);
        let dist = center.distance(*point) as f32 * factor;
        output.push(Coord::from_angle(
            center,
            dist.round().max(0.0) as usize,
            angle,
        ));
    }
    output
}

/// Rotate `points` around the `center` by `degrees`
///
/// The resulting points at the same distance but at +degrees angle
#[must_use]
pub fn rotate_points(center: Coord, points: &[Coord], degrees: isize) -> Vec<Coord> {
    let mut output = vec![];
    for point in points {
        let starting_angle = center.angle_to(*point);
        let dist = center.distance(*point);
        output.push(Coord::from_angle(center, dist, starting_angle + degrees));
    }
    output
}

#[cfg(test)]
mod test {
    use crate::rotate_points;

    #[test]
    fn one_point_rotation() {
        let center = coord!(20, 20);
        let initial = coord!(30, 20);
        let no_rotation = rotate_points(center, &[initial], 0);
        let quarter_rotation = rotate_points(center, &[initial], 90);
        let half_rotation = rotate_points(center, &[initial], 180);
        let three_quarter_rotation = rotate_points(center, &[initial], 270);
        let full_rotation = rotate_points(center, &[initial], 360);
        assert_eq!(no_rotation, vec![coord!(30, 20)]);
        assert_eq!(quarter_rotation, vec![coord!(20, 30)]);
        assert_eq!(half_rotation, vec![coord!(10, 20)]);
        assert_eq!(three_quarter_rotation, vec![coord!(20, 10)]);
        assert_eq!(full_rotation, vec![coord!(30, 20)]);
        let one_degree = rotate_points(center, &[initial], 1);
        assert_eq!(one_degree, vec![coord!(30, 20)]);
        let eighth_degree = rotate_points(center, &[initial], 45);
        assert_eq!(eighth_degree, vec![coord!(27, 27)]);
    }
}