glifparser 2.0.1

use skia_safe as skia;
use skia::{Point as SkPoint, Path as SkPath};
use skia::path::{Verb as SkVerb};

use crate::point::{Handle, Point, PointData, PointType};
use crate::{Contour, Outline};

use crate::outline::QuadToCubic;

/// Get an outline from a Skia path. Outline is guaranteed to contain only Curve's, no QCurve's.
pub trait FromSkiaPath {
    fn from_skia_path(skp: &skia::Path) -> Self;
}

// These types should only be used outside this file with care and are shorthand for FromSkiaPath
pub type SkPointTuple = (PointType, Vec<SkPoint>, Option<f32>);
pub type SkContour = Vec<SkPointTuple>;
pub type SkOutline = Vec<SkContour>;

pub trait TryIntoPointType {
    fn try_into_pointtype(&self) -> Option<PointType>;
}

impl TryIntoPointType for SkVerb {
    fn try_into_pointtype(&self) -> Option<PointType> {
        match self {
            SkVerb::Move => Some(PointType::Move),
            SkVerb::Cubic => Some(PointType::Curve),
            SkVerb::Quad | SkVerb::Conic => Some(PointType::QCurve),
            SkVerb::Line => Some(PointType::Line),
            SkVerb::Close | SkVerb::Done => None,
        }
    }
}

pub trait SplitSkiaPath {
    fn split_skia_path(&self) -> SkOutline;
}

impl SplitSkiaPath for skia::Path {
    fn split_skia_path(&self) -> SkOutline {
        // These are iterators over (Verb, Vec<skia_safe::Point>)
        // We need two of them because the for loop consumes `iter`, meaning we can't get the conic
        // weight from it. This is ugly, I know, but converting C API's to Rust often are.
        let iter = skia::path::Iter::new(self, false);
        let mut iter2 = skia::path::Iter::new(self, false);

        let mut skoutline: SkOutline = vec![];
        let mut skcontour: SkContour = vec![];

        // First we're going to split a path into its constituent contours
        for p in iter {
            iter2.next();
            let (verb, point) = p;
            let conic_weight = iter2.conic_weight();
            // This lets us know if the QCurve needs conversion
            let mut holding_conic = false;
            if verb == SkVerb::Done {
                break
            } else if verb == SkVerb::Conic {
                holding_conic = true;
            }
            let ptype = verb.try_into_pointtype();
            if ptype == Some(PointType::Move) {
                if skcontour.len() > 0 {
                    skoutline.push(skcontour.clone());
                }
                skcontour = vec![];
            }
            //eprintln!("Verb: {:?}, Point: {:?}, Conic Weight: {:?}", verb, &point, conic_weight);
            if let Some(pty) = ptype {
                skcontour.push((pty, point, if holding_conic { Some(conic_weight.unwrap()) } else { None }));
            } else {
                debug_assert!(skcontour[0].0 == PointType::Move);
                skcontour.remove(0);
                // drop "off curve" point
            }
        }

        if skcontour.len() > 0 {
            skoutline.push(skcontour);
        }

        skoutline
    }
}

pub trait ConicsToCubics {
    fn conics_to_cubics(self) -> Self;
}

impl ConicsToCubics for SkOutline {
    fn conics_to_cubics(mut self) -> Self {
        // The path could contain conics, so our next task is to resolve conics to quads
        for skc in self.iter_mut() {
            for skp in skc.iter_mut() {
                let skp: &mut SkPointTuple = skp;
                let (_verbs, points, conic_weight) = skp;
                if let Some(cw) = conic_weight {
                    debug_assert_eq!(points.len(), 3);
                    // magic number 5 for pow2 1 from https://fiddle.skia.org/c/@Path_ConvertConicToQuads
                    let mut new_points = vec![SkPoint::default(); 5];
                    //               convert_conic_to_quads(p0: impl Into<Point>, p1: impl Into<Point>, p2: impl Into<Point>, 
                    //                                      w: scalar, pts: &mut [Point], pow2: usize) -> Option<usize>
                    let ok = SkPath::convert_conic_to_quads(points[0], points[1], points[2], 
                                                            *cw, &mut new_points, 1);
                    //      number of quad bezier's == 2
                    debug_assert!(ok.is_some() && ok.unwrap() == 2);
                    // We already changed the verb above by resolving skia::PointType::Conic as our PointType::QCurve
                    // So, we only need to update the points, a quad is already expected.
                    *points = new_points;
                    // We do this to mark the points as changed, so we can panic if it's ever not
                    // infinity
                    *conic_weight = Some(f32::INFINITY);
                }
            }
        }

        // Now we have to change the converted conics to two quads, to match other curves that
        // might be the result of quad_to as opposed to conic_to.
        let mut final_skoutline: SkOutline = vec![];

        for skc in self {
            let mut skcontour: SkContour = vec![];
            for skp in skc.into_iter() {
                let (ptype, points, conic_weight) = skp;
                if ptype == PointType::QCurve {
                    // same magic number as above. we always use a pow2 of 1 to convert conics to
                    // quads, so we get 5 points
                    assert!(points.len() == 3 || points.len() == 5);
                    let new_points_n = if points.len() == 3 { 1 } else { 2 };

                    // We don't want any quads, despite all the work we've done to get them. Skia
                    // doesn't have a function like convert_conic_to_cubics, only to_quads, so now
                    // that we have the quads we can make cubics.
                    skcontour.push((PointType::Curve, [points[0], points[1], points[2]].quad_to_cubic().to_vec(), None));
                    if new_points_n == 2 {
                        skcontour.push((PointType::Curve, [points[2], points[3], points[4]].quad_to_cubic().to_vec(), None));
                    }
                } else {
                    skcontour.push((ptype, points, conic_weight));
                }
            }
            final_skoutline.push(skcontour);
        }

        //eprintln!("{:#?}", &final_skoutline);

        final_skoutline
    }
}

// This is a complex conversion. I documented it as best I could, and left around old debug
// eprintln's in case you find a broken case. It's quite complicated and takes multiple passes
// because Skia path's can contain conics and quads, both of which we want to upconvert to cubics.
impl<PD: PointData> FromSkiaPath for Outline<PD> {
    fn from_skia_path(skp: &skia::Path) -> Outline<PD> {
        Outline::from_skoutline(skp.split_skia_path().conics_to_cubics())
    }
}

pub trait FromSkOutline {
    fn from_skoutline(skoutline: SkOutline) -> Self;
}

impl<PD: PointData> FromSkOutline for Outline<PD> {
    fn from_skoutline(mut skoutline: SkOutline) -> Self {
        // Now we know that we have no conics, and no quads. In Skia terms, we only have the verbs
        // Move, Line, Cubic, Close, and Done.
        //
        // We can now convert to a cubic Bézier-backed glifparser Outline.
        let mut ret: Outline<PD> = Outline::new();

        for skc in skoutline.iter_mut() {
            let skc_len = skc.len();
            let mut contour: Contour<PD> = Contour::new();
            let first_points: &SkPointTuple = &skc[0];
            let mut prev_points;
            for (i, skp) in skc.iter().enumerate() {
                let (ptype, points, conic_weights) = skp;
                debug_assert!(conic_weights.iter().all(|c|!c.is_finite()));

                if i != 0 {
                    prev_points = &skc[i-1];
                } else {
                    prev_points = &skc[skc_len - 1];
                }

                let mut point = Point::<PD> {
                    name: None,
                    data: None,
                    x: points[0].x,
                    y: points[0].y,
                    smooth: false,
                    // These will be fixed below, if needed
                    a: Handle::Colocated,
                    b: Handle::Colocated,
                    ptype: *ptype,
                };

                match ptype {
                    PointType::Move => {},
                    PointType::Curve => {
                        point.a = Handle::At(points[1].x, points[1].y);
                        if prev_points.0 == PointType::Curve {
                            point.b = Handle::At(prev_points.1[2].x, prev_points.1[2].y);
                        }

                        if i == skc_len-1 {
                            if first_points.0 == PointType::Curve {
                                contour[0].a = Handle::At(first_points.1[1].x, first_points.1[1].y);
                            }
                            contour[0].b = Handle::At(points[2].x, points[2].y);
                        }
                    },
                    PointType::Line => {
                        if i != 0 && prev_points.0 == PointType::Curve {
                            // Lines aren't allowed to have off-curve points in glif format
                            point.ptype = PointType::Curve;
                            point.b = Handle::At(prev_points.1[2].x, prev_points.1[2].y);
                        }
                    },
                    _ => unreachable!("")
                }
                contour.push(point);
            }

            if contour.first().map(|p|p.ptype == PointType::Move).unwrap_or(false) {
                fixup_skia_open_contour(&mut contour, &skc);
            }

            ret.push(contour);
        }

        ret
    }
}

fn fixup_skia_open_contour<PD: PointData>(contour: &mut Contour<PD>, skc: &SkContour) {
    // Skia doesn't put a last point like we expect for open contours
    let skc_len = skc.len();
    let first = contour.first().unwrap().clone();
    let last = contour.last().unwrap();
    if last.ptype == PointType::Curve || last.ptype == PointType::Line {
        let ptype = match skc[skc_len-1].1.len() {
            2 => PointType::Line,
            4 => PointType::Curve,
            _ => {unreachable!()}
        };
        let p = match ptype {
            PointType::Line => {
                skc[skc_len-1].1[1]
            },
            PointType::Curve => {
                skc[skc_len-1].1[3]
            },
            _ => {unreachable!()}
        };
        let mut glifl: Point<PD> = Point::from_x_y_type((p.x, p.y), ptype);
        if ptype == PointType::Curve {
            let h_prev = skc[skc_len-1].1[2];
            if p != h_prev {
                glifl.b = Handle::At(h_prev.x, h_prev.y);
            }
        }
        contour.push(glifl);
    }

    // Skia adds Move followed by Line at same spot, .glif format only needs the Move
    if contour.len() >= 2 && contour[1].x == first.x && contour[1].y == first.y {
        contour[0].a = contour[1].a;
        contour[0].b = contour[1].b;
        contour.remove(1);
    }
}