ZIm/crates/gpui/src/path_builder.rs

use anyhow::Error;
use etagere::euclid::Vector2D;
use lyon::geom::Angle;
use lyon::tessellation::{
    BuffersBuilder, FillTessellator, FillVertex, StrokeTessellator, StrokeVertex, VertexBuffers,
};

pub use lyon::math::Transform;
pub use lyon::tessellation::{FillOptions, FillRule, StrokeOptions};

use crate::{point, px, Path, Pixels, Point};

/// Style of the PathBuilder
pub enum PathStyle {
    /// Stroke style
    Stroke(StrokeOptions),
    /// Fill style
    Fill(FillOptions),
}

/// A [`Path`] builder.
pub struct PathBuilder {
    raw: lyon::path::builder::WithSvg<lyon::path::BuilderImpl>,
    transform: Option<lyon::math::Transform>,
    /// PathStyle of the PathBuilder
    pub style: PathStyle,
}

impl From<lyon::path::Builder> for PathBuilder {
    fn from(builder: lyon::path::Builder) -> Self {
        Self {
            raw: builder.with_svg(),
            ..Default::default()
        }
    }
}

impl From<lyon::path::builder::WithSvg<lyon::path::BuilderImpl>> for PathBuilder {
    fn from(raw: lyon::path::builder::WithSvg<lyon::path::BuilderImpl>) -> Self {
        Self {
            raw,
            ..Default::default()
        }
    }
}

impl From<lyon::math::Point> for Point<Pixels> {
    fn from(p: lyon::math::Point) -> Self {
        point(px(p.x), px(p.y))
    }
}

impl From<Point<Pixels>> for lyon::math::Point {
    fn from(p: Point<Pixels>) -> Self {
        lyon::math::point(p.x.0, p.y.0)
    }
}

impl Default for PathBuilder {
    fn default() -> Self {
        Self {
            raw: lyon::path::Path::builder().with_svg(),
            style: PathStyle::Fill(FillOptions::default()),
            transform: None,
        }
    }
}

impl PathBuilder {
    /// Creates a new [`PathBuilder`] to build a Stroke path.
    pub fn stroke(width: Pixels) -> Self {
        Self {
            style: PathStyle::Stroke(StrokeOptions::default().with_line_width(width.0)),
            ..Self::default()
        }
    }

    /// Creates a new [`PathBuilder`] to build a Fill path.
    pub fn fill() -> Self {
        Self::default()
    }

    /// Sets the style of the [`PathBuilder`].
    pub fn with_style(self, style: PathStyle) -> Self {
        Self { style, ..self }
    }

    /// Move the current point to the given point.
    #[inline]
    pub fn move_to(&mut self, to: Point<Pixels>) {
        self.raw.move_to(to.into());
    }

    /// Draw a straight line from the current point to the given point.
    #[inline]
    pub fn line_to(&mut self, to: Point<Pixels>) {
        self.raw.line_to(to.into());
    }

    /// Draw a curve from the current point to the given point, using the given control point.
    #[inline]
    pub fn curve_to(&mut self, to: Point<Pixels>, ctrl: Point<Pixels>) {
        self.raw.quadratic_bezier_to(ctrl.into(), to.into());
    }

    /// Adds a cubic Bézier to the [`Path`] given its two control points
    /// and its end point.
    #[inline]
    pub fn cubic_bezier_to(
        &mut self,
        to: Point<Pixels>,
        control_a: Point<Pixels>,
        control_b: Point<Pixels>,
    ) {
        self.raw
            .cubic_bezier_to(control_a.into(), control_b.into(), to.into());
    }

    /// Close the current sub-path.
    #[inline]
    pub fn close(&mut self) {
        self.raw.close();
    }

    /// Applies a transform to the path.
    #[inline]
    pub fn transform(&mut self, transform: Transform) {
        self.transform = Some(transform);
    }

    /// Applies a translation to the path.
    #[inline]
    pub fn translate(&mut self, to: Point<Pixels>) {
        if let Some(transform) = self.transform {
            self.transform = Some(transform.then_translate(Vector2D::new(to.x.0, to.y.0)));
        } else {
            self.transform = Some(Transform::translation(to.x.0, to.y.0))
        }
    }

    /// Applies a scale to the path.
    #[inline]
    pub fn scale(&mut self, scale: f32) {
        if let Some(transform) = self.transform {
            self.transform = Some(transform.then_scale(scale, scale));
        } else {
            self.transform = Some(Transform::scale(scale, scale));
        }
    }

    /// Applies a rotation to the path.
    ///
    /// The `angle` is in degrees value in the range 0.0 to 360.0.
    #[inline]
    pub fn rotate(&mut self, angle: f32) {
        let radians = angle.to_radians();
        if let Some(transform) = self.transform {
            self.transform = Some(transform.then_rotate(Angle::radians(radians)));
        } else {
            self.transform = Some(Transform::rotation(Angle::radians(radians)));
        }
    }

    /// Builds into a [`Path`].
    #[inline]
    pub fn build(self) -> Result<Path<Pixels>, Error> {
        let path = if let Some(transform) = self.transform {
            self.raw.build().transformed(&transform)
        } else {
            self.raw.build()
        };

        match self.style {
            PathStyle::Stroke(options) => Self::tessellate_stroke(&path, &options),
            PathStyle::Fill(options) => Self::tessellate_fill(&path, &options),
        }
    }

    fn tessellate_fill(
        path: &lyon::path::Path,
        options: &FillOptions,
    ) -> Result<Path<Pixels>, Error> {
        // Will contain the result of the tessellation.
        let mut buf: VertexBuffers<lyon::math::Point, u16> = VertexBuffers::new();
        let mut tessellator = FillTessellator::new();

        // Compute the tessellation.
        tessellator.tessellate_path(
            path,
            options,
            &mut BuffersBuilder::new(&mut buf, |vertex: FillVertex| vertex.position()),
        )?;

        Ok(Self::build_path(buf))
    }

    fn tessellate_stroke(
        path: &lyon::path::Path,
        options: &StrokeOptions,
    ) -> Result<Path<Pixels>, Error> {
        // Will contain the result of the tessellation.
        let mut buf: VertexBuffers<lyon::math::Point, u16> = VertexBuffers::new();
        let mut tessellator = StrokeTessellator::new();

        // Compute the tessellation.
        tessellator.tessellate_path(
            path,
            options,
            &mut BuffersBuilder::new(&mut buf, |vertex: StrokeVertex| vertex.position()),
        )?;

        Ok(Self::build_path(buf))
    }

    /// Builds a [`Path`] from a [`lyon::VertexBuffers`].
    pub fn build_path(buf: VertexBuffers<lyon::math::Point, u16>) -> Path<Pixels> {
        if buf.vertices.is_empty() {
            return Path::new(Point::default());
        }

        let first_point = buf.vertices[0];

        let mut path = Path::new(first_point.into());
        for i in 0..buf.indices.len() / 3 {
            let i0 = buf.indices[i * 3] as usize;
            let i1 = buf.indices[i * 3 + 1] as usize;
            let i2 = buf.indices[i * 3 + 2] as usize;

            let v0 = buf.vertices[i0];
            let v1 = buf.vertices[i1];
            let v2 = buf.vertices[i2];

            path.push_triangle(
                (v0.into(), v1.into(), v2.into()),
                (point(0., 1.), point(0., 1.), point(0., 1.)),
            );
        }

        path
    }
}