use super::exporter::{UNDECODED, address, blend, color, constant_mask, cover, in_range, norm, rects_overlap, rule, to_path, writable, xf};
use super::{
    Affine, AppearanceItem, BezPath, BlendMode, Exporter, Fill, FillRule, LineCap, LineJoin, Mark, Node, NodeKind, NormalizedF32, Paint, Path, Rect,
    Shape, Stroke, StrokeAlign, StrokeDash, StrokeLayer, Surface, WrittenShape, krilla, stroke,
};

/// An object's visual box for leaving out what is off the page. A plain group or layer also holds
/// the boxes of the members it is measured through ([`Node::editing_children`], in order), so that
/// the walk measures them once.
struct Measured {
    bounds: Option<Rect>,
    members: Vec<Measured>,
}

#[cfg(test)]
std::thread_local! {
    /// The objects this thread has measured for the walk and for the links (tests).
    pub(crate) static MEASURES: std::cell::Cell<usize> = const { std::cell::Cell::new(0) };
}

impl Exporter<'_> {
    /// Opacity mask → luminosity soft mask. Outside the art the backdrop is black (clip) or white;
    /// invert is a white Difference rect on top (luminance is linear, so luma(1 − c) = 1 − luma(c)).
    fn soft_mask(&mut self, s: &mut Surface, m: &vectorcraft_doc::OpacityMask, page: Rect) -> Option<krilla::mask::Mask> {
        let mut sb = s.stream_builder();
        let mut ms = sb.surface();
        // An opaque backdrop when it matters: white outside the art (no clip), or black for the
        // inverting Difference pass below to turn white.
        if !m.clip || m.invert {
            cover(&mut ms, page, if m.clip { 0 } else { 255 }, 1.0);
        }
        // Mask art is a picture of its own: it takes no part in a knockout group around the object,
        // and has no inks to overprint.
        let knockout = std::mem::take(&mut self.knockout);
        let overprint = std::mem::take(&mut self.overprint);
        let image_left_out = self.image_left_out.replace(false);
        self.node(&mut ms, &m.art, page, true);
        let incomplete = self.image_left_out.unwrap_or(false);
        self.image_left_out = image_left_out.map(|outer| outer || incomplete);
        (self.knockout, self.overprint) = (knockout, overprint);
        if incomplete {
            return None;
        }
        if m.invert {
            ms.push_blend_mode(krilla::blend::BlendMode::Difference);
            cover(&mut ms, page, 255, 1.0);
            ms.pop();
        }
        ms.finish();
        Some(krilla::mask::Mask::new(sb.finish(), krilla::mask::MaskType::Luminosity))
    }

    /// The children of a group, as the elements of a knockout group when it is one.
    pub(super) fn children(&mut self, s: &mut Surface, children: &[std::sync::Arc<Node>], page: Rect) {
        self.measured_children(s, children, page, &[]);
    }

    /// [`Self::children`] with the boxes of the last members in `measured`.
    fn measured_children(&mut self, s: &mut Surface, children: &[std::sync::Arc<Node>], page: Rect, measured: &[Measured]) {
        if !self.knockout {
            let unmeasured = children.len().saturating_sub(measured.len());
            for (i, c) in children.iter().enumerate() {
                self.measured_node(s, c, page, false, i.checked_sub(unmeasured).and_then(|i| measured.get(i)));
            }
            return;
        }
        // The PDF writer has no knockout groups: each element is drawn through a soft mask of
        // where the elements above it don't paint (the same look for Normal blending). The masks
        // nest, so element i sits inside the masks of elements i+1…n: open them outermost first.
        self.warn("knockout groups are written as soft-masked groups (same look, but not editable as knockout groups)");
        let elements: Vec<_> = Node::knockout_elements(children)
            .into_iter()
            .map(|c| (c, self.measure(c)))
            .filter(|(_, m)| m.bounds.is_some_and(|b| rects_overlap(b.inflate(1.0, 1.0), page)))
            .collect();
        let Some(((first, measured), rest)) = elements.split_first() else { return };
        for (c, m) in rest.iter().rev() {
            let mask = self.knockout_mask(s, c, page, m);
            s.push_mask(mask);
        }
        self.measured_node(s, first, page, false, Some(measured));
        for (c, m) in rest {
            s.pop();
            self.measured_node(s, c, page, false, Some(m));
        }
    }

    /// A luminosity mask that is 1 − the knockout shape of `c`, whose box is in `measured`: white,
    /// then black through an alpha mask of `c` (at full object opacity without its own mask, unless
    /// those define its shape).
    fn knockout_mask(&mut self, s: &mut Surface, c: &Node, page: Rect, measured: &Measured) -> krilla::mask::Mask {
        let shape = if c.knockout_shape {
            c.clone()
        } else {
            let mut s = c.clone().with_mask(None);
            s.opacity = 1.0;
            s
        };
        let mut sb = s.stream_builder();
        let mut ms = sb.surface();
        cover(&mut ms, page, 255, 1.0);
        let alpha = {
            let mut ab = ms.stream_builder();
            let mut als = ab.surface();
            let overprint = std::mem::take(&mut self.overprint);
            self.measured_node(&mut als, &shape, page, false, Some(measured));
            self.overprint = overprint;
            als.finish();
            krilla::mask::Mask::new(ab.finish(), krilla::mask::MaskType::Alpha)
        };
        ms.push_mask(alpha);
        cover(&mut ms, page, 0, 1.0);
        ms.pop();
        ms.finish();
        krilla::mask::Mask::new(sb.finish(), krilla::mask::MaskType::Luminosity)
    }

    /// The box of `n`, and of the members of a plain group or layer.
    fn measure(&self, n: &Node) -> Measured {
        if !matches!(n.kind, NodeKind::Layer { clip: false, .. } | NodeKind::Group { clip: false, .. }) {
            #[cfg(test)]
            MEASURES.with(|m| m.set(m.get() + 1));
            return Measured { bounds: n.visual_bounds_with(&self.symbols), members: vec![] };
        }
        let members: Vec<_> = n.editing_children().iter().map(|c| self.measure(c)).collect();
        Measured { bounds: n.visual_of_members(members.iter().map(|m| m.bounds)), members }
    }

    pub(super) fn node(&mut self, s: &mut Surface, n: &Node, page: Rect, force: bool) {
        self.measured_node(s, n, page, force, None);
    }

    /// [`Self::node`] with the box of `n` in `measured`, when its parent measured it.
    fn measured_node(&mut self, s: &mut Surface, n: &Node, page: Rect, force: bool, measured: Option<&Measured>) {
        if self.layers
            && self.in_layer != address(n)
            && let NodeKind::Layer { printable, .. } = n.kind
            && (printable || self.non_printing)
            && let Some(&i) = self.layer_index.get(&address(n))
        {
            // A PDF layer: hidden layers and sublayers are written too (their group is off).
            let enclosing = std::mem::replace(&mut self.in_layer, address(n));
            let paper = self.paper;
            crate::forms::layer_form(s, i, paper, |s| self.node(s, n, page, true));
            self.in_layer = enclosing;
            return;
        }
        if !force && !n.visible {
            return;
        }
        if let NodeKind::Layer { template, printable, .. } = n.kind
            && (template || !(printable || self.non_printing))
        {
            return;
        }
        // A container written whatever its box is has no use for one.
        let own = (measured.is_none() && !(force && n.is_container())).then(|| self.measure(n));
        let measured = measured.or(own.as_ref());
        match measured.map(|m| m.bounds) {
            Some(Some(b)) if !force && !rects_overlap(b.inflate(1.0, 1.0), page) => return,
            Some(None) if !n.is_container() => return,
            _ => {}
        }
        self.warn_raster(&n.appearance.effects, || format!("{} objects", n.kind_label().to_lowercase()));
        let container = n.is_container() && !matches!(n.kind, NodeKind::Compound { .. });
        // Whether this container's children knock each other out (a knockout group is written as a group).
        let knockout = n.knocks_out(self.knockout);
        let enclosing = std::mem::replace(&mut self.knockout, knockout);
        let mut pushes = 0;
        if n.blend != BlendMode::Normal {
            s.push_blend_mode(blend(n.blend));
            pushes += 1;
        }
        if n.opacity < 1.0 || (container && (n.isolate || n.blend != BlendMode::Normal || knockout)) {
            if !n.isolate && n.blends_through() {
                // Not isolated: blending inside reaches the art below the group.
                let alpha = constant_mask(s, page, n.opacity);
                s.push_mask(alpha);
            } else if n.opacity < 1.0 {
                s.push_opacity(norm(n.opacity));
            } else {
                s.push_isolated();
            }
            pushes += 1;
        }
        let mask = n.extras().mask.as_deref().filter(|m| !m.disabled);
        let alpha = match (&n.kind, mask) {
            (NodeKind::Image(im), Some(m)) => self.masked_image(im, m, !n.extras().pixelated),
            _ => None,
        };
        if let Some(m) = mask
            && alpha.is_none()
        {
            let Some(mask) = self.soft_mask(s, m, page) else {
                self.knockout = enclosing;
                for _ in 0..pushes {
                    s.pop();
                }
                return;
            };
            s.push_mask(mask);
            pushes += 1;
        }
        match &n.kind {
            NodeKind::Layer { children, clip: false, .. } | NodeKind::Group { children, clip: false } => {
                self.measured_children(s, children, page, measured.map_or(&[], |m| m.members.as_slice()));
            }
            NodeKind::Group { children, clip: true } | NodeKind::Layer { children, clip: true, .. } => {
                // The region every output clips to; nothing to clip by hides the clipped art. The
                // clipping path's fill paints behind the clipped art and its stroke over it, unclipped.
                if let Some((clip, rest)) = children.split_first()
                    && let Some((p, r)) = vectorcraft_effects::clip_outline(clip).and_then(|(bp, r)| to_path(s, &bp).map(|p| (p, r)))
                {
                    let paint = clip.clip_paint();
                    s.push_clip_path(&p, &rule(r));
                    if let Some(fill) = &paint.fill {
                        self.node(s, fill, page, false);
                    }
                    self.children(s, rest, page);
                    s.pop();
                    if let Some(stroke) = &paint.stroke {
                        self.node(s, stroke, page, false);
                    }
                }
            }
            NodeKind::Path { path, rule, guide, .. } => {
                if !*guide {
                    self.shape(s, n, &path.to_bezpath(), *rule, page);
                }
            }
            NodeKind::Compound { children, rule } => {
                let mut bp = BezPath::new();
                for c in children {
                    if let Some(p) = c.path_data() {
                        bp.extend(p.to_bezpath());
                    }
                }
                self.shape(s, n, &bp, *rule, page);
            }
            NodeKind::Text(t) => self.text(s, n, t, page),
            NodeKind::Image(im) => match n.extras().colorize.as_deref() {
                Some(p @ Paint::Solid { .. }) if self.doc.image_blob(im).is_none_or(vectorcraft_doc::ImageBlob::takes_colorize) => {
                    if writable(s, im.xf, Rect::new(0.0, 0.0, im.width.max(1).into(), im.height.max(1).into())) {
                        if let Some(colorized) = self.colorized_image(im, p, !n.extras().pixelated) {
                            self.image(s, im, Some(colorized), n.extras().pixelated);
                        } else {
                            self.image_left_out = self.image_left_out.map(|_| true);
                            self.warn(UNDECODED);
                        }
                    } else if self.image_left_out.is_some() {
                        self.image_left_out = Some(true);
                        self.warn(super::exporter::UNWRITABLE_IMAGE);
                    }
                }
                _ => self.image(s, im, alpha, n.extras().pixelated),
            },
            NodeKind::SymbolInstance { symbol, xf } => {
                // Within the objects a frame may draw of symbol instances, as on screen: nested
                // instances multiply.
                // Placing through 9-slice guides needs room for the most objects it can make
                // (`NineSliceMap::most_placed`), and the objects it makes count.
                // A dynamic symbol's instance shows its own appearance changes.
                let doc = self.doc;
                if let Some(sym) = doc.symbols.iter().find(|x| &x.name == symbol) {
                    let changed;
                    let art: &Node = if n.extras().symbol_overrides.is_empty() {
                        &sym.art
                    } else {
                        changed = vectorcraft_doc::symbol_overrides::dynamic_art(&sym.art, n);
                        &changed
                    };
                    let count = art.count() as u64;
                    let map = doc.symbol_slice_map(symbol, *xf);
                    let most = map.map_or(count, |m| m.most_placed(art, doc));
                    let placed = vectorcraft_doc::charge_symbol_art(&mut self.symbol_nodes, most, || {
                        let art = match map {
                            Some(m) => m.place(art, doc),
                            None => {
                                let mut a = art.clone();
                                a.transform(*xf, false);
                                a
                            }
                        };
                        // As `most_placed`, placed art counts its opacity-mask art.
                        let count = if map.is_some() { art.count_with_masks() } else { art.count() } as u64;
                        (art, count)
                    });
                    if let Some(art) = placed {
                        self.node(s, &art, page, true);
                    }
                }
            }
            // A gradient mesh is a smooth patch shading where it can be written as one.
            NodeKind::Mesh(m) if self.mesh(s, m) => {}
            // Live blends/envelopes/meshes export their evaluated (expanded) form.
            NodeKind::Blend { .. }
            | NodeKind::Envelope { .. }
            | NodeKind::Mesh(_)
            | NodeKind::Repeat(_)
            | NodeKind::PlacedDocument(_)
            | NodeKind::Intertwine { .. } => {
                let g = vectorcraft_effects::expand_live_deep(Some(self.doc), n);
                for c in g.children().into_iter().flatten() {
                    self.node(s, c, page, false);
                }
            }
        }
        self.knockout = enclosing;
        for _ in 0..pushes {
            s.pop();
        }
    }

    /// Gradient mesh `m` as one PDF Type 6 (Coons patch) shading filling its outline (ISO 32000-1,
    /// 8.7.4.5.7): each patch blends its corner colours bilinearly, as the canvas draws it, and
    /// the viewer or RIP does so smoothly at its own resolution. Cutting the mesh into flat quads
    /// instead banded, left seams between them, and made files with many meshes very large.
    /// Corner colours are written as [`Self::page_color`] writes any colour; RGB among other
    /// models goes through RGB, as the writer needs one colour space a shading (ink-based ones:
    /// CMYK and grey, merge). `false` when it isn't written so: the caller draws it expanded.
    /// That is a mesh with see-through points (their opacities would be a soft mask of another
    /// patch shading, which a common viewer, Poppler, draws with gaps and too opaque; the quads
    /// carry their own opacity), an invalid mesh, or one beyond the coordinates a file holds.
    fn mesh(&mut self, s: &mut Surface, m: &vectorcraft_doc::live::GradientMesh) -> bool {
        if !m.is_valid() || !m.points.iter().all(|p| p.opacity >= 1.0) {
            return false;
        }
        let Some(bounds) = m.bounds() else { return false };
        if !writable(s, Affine::IDENTITY, bounds) {
            return false;
        }
        let Some(path) = to_path(s, &m.outline().to_bezpath()) else { return false };
        let page: Vec<vectorcraft_color::Color> = m.points.iter().map(|p| self.page_color(&p.color)).collect();
        let mixed = page.windows(2).any(|w| w[0].model() != w[1].model());
        let rgb = page.iter().any(|c| matches!(c, vectorcraft_color::Color::Rgb { .. } | vectorcraft_color::Color::Lab { .. }));
        let colors: Vec<krilla::color::Color> =
            page.iter().map(|c| if mixed && rgb { color(&c.in_model(vectorcraft_color::cms::Model::Rgb)) } else { color(c) }).collect();
        let pt = |p: vectorcraft_geom::Point| (p.x as f32, p.y as f32);
        let mut patches = Vec::with_capacity(m.rows as usize * m.cols as usize);
        for r in 0..m.rows as usize {
            for c in 0..m.cols as usize {
                // The corners in the order a Type 6 shading lists them: down the left edge (v),
                // along the bottom (u), back up the right edge and back along the top.
                let corners = [m.idx(r, c), m.idx(r + 1, c), m.idx(r + 1, c + 1), m.idx(r, c + 1)];
                let (left, bottom, right, top) = (m.edge_v(r, c), m.edge_u(r + 1, c), m.edge_v(r, c + 1), m.edge_u(r, c));
                let points =
                    [left.p0, left.p1, left.p2, left.p3, bottom.p1, bottom.p2, bottom.p3, right.p2, right.p1, right.p0, top.p2, top.p1].map(pt);
                let Some(colors) =
                    corners.iter().map(|&i| colors.get(i).cloned()).collect::<Option<Vec<_>>>().and_then(|v| <[_; 4]>::try_from(v).ok())
                else {
                    return false;
                };
                patches.push(krilla::paint::MeshPatch { points, colors, opacities: [NormalizedF32::ONE; 4] });
            }
        }
        let mesh = krilla::paint::MeshGradient { patches, transform: xf(Affine::IDENTITY), anti_alias: false };
        s.set_stroke(None);
        s.set_fill(Some(Fill { paint: mesh.into(), opacity: NormalizedF32::ONE, rule: krilla::paint::FillRule::NonZero }));
        s.draw_path(&path);
        s.set_fill(None);
        true
    }

    fn shape(&mut self, s: &mut Surface, n: &Node, bp: &BezPath, r: FillRule, page: Rect) {
        let Some(path) = to_path(s, bp) else { return };
        let bounds = bp.bounding_box();
        for item in &n.appearance.items {
            match item {
                AppearanceItem::Fill(fl) => {
                    if !fl.visible || fl.paint.is_none() {
                        continue;
                    }
                    self.warn_raster(&fl.effects, || "fills".into());
                    self.overprinting(s, fl.overprint, &fl.paint, |ex, s| {
                        if ex.area(s, &path, rule(r), &fl.paint, (fl.opacity, fl.blend), bounds, bounds, true) {
                            return;
                        }
                        let Some(paint) = ex.paint(s, &fl.paint, bounds) else { return };
                        let bl = fl.blend != BlendMode::Normal;
                        if bl {
                            s.push_blend_mode(blend(fl.blend));
                        }
                        s.set_stroke(None);
                        s.set_fill(Some(Fill { paint, opacity: norm(fl.opacity), rule: rule(r) }));
                        s.draw_path(&path);
                        if bl {
                            s.pop();
                        }
                    });
                }
                AppearanceItem::Stroke(st) => {
                    if !st.visible || st.paint.is_none() || st.width <= 0.0 {
                        continue;
                    }
                    self.warn_raster(&st.effects, || "strokes".into());
                    self.overprinting(s, st.overprint, &st.paint, |ex, s| ex.stroke(s, bp, &path, r, st, page, bounds));
                }
            }
        }
        s.set_fill(None);
        s.set_stroke(None);
    }

    /// Draw a fill or stroke of `paint` with `draw`: as a form marked to overprint when it
    /// `overprints`, paints and overprints are kept (but not a white one with Discard White
    /// Overprint).
    pub(super) fn overprinting(&mut self, s: &mut Surface, overprints: bool, paint: &Paint, draw: impl FnOnce(&mut Self, &mut Surface)) {
        let white = || self.doc.setup.discard_white_overprint && vectorcraft_doc::overprint::is_white(paint);
        if overprints && self.overprint && !paint.is_none() && !white() {
            self.overprinted = true;
            crate::forms::form(s, Mark::Overprint, |s| draw(self, s));
        } else {
            draw(self, s);
        }
    }

    /// Is `p` a paint PDF has no paint for when it paints a fill (`fill`) or a stroke, which
    /// [`Self::area`] draws as art: a pattern swatch or a gradient drawn as pixels
    /// ([`vectorcraft_color::GradientPaint::draws_as_pixels`]), but not a Perceptual one of spot
    /// inks ([`Self::perceptual_spot`])?
    pub(super) fn area_paint(&self, p: &Paint, fill: bool) -> bool {
        match p {
            Paint::Pattern { pattern, .. } => self.doc.pattern(pattern).is_some(),
            Paint::Gradient(g) => g.draws_as_pixels(fill) && !self.perceptual_spot(g, fill),
            _ => false,
        }
    }

    /// Paint the area `clip` (filled by `rule`; bounds `area`) with `p` at `transparency` (opacity,
    /// blend mode) when it is an [area paint](Self::area_paint) of a fill (`fill`) or a stroke: a
    /// pattern's [tiling pattern](Self::tiling) (else its tile instances covering it), or an image
    /// of a gradient drawn as pixels placed on `bounds` (the painted object's box, as on the
    /// canvas), clipped to it. False (nothing drawn) for other paints.
    #[allow(clippy::too_many_arguments)]
    pub(super) fn area(
        &mut self,
        s: &mut Surface,
        clip: &Path,
        rule: krilla::paint::FillRule,
        p: &Paint,
        transparency: (f32, BlendMode),
        bounds: Rect,
        area: Rect,
        fill: bool,
    ) -> bool {
        if !self.area_paint(p, fill) {
            return false;
        }
        let (opacity, mode) = transparency;
        let tiling = match p {
            Paint::Pattern { pattern, xf } => self.tiling(s, pattern, *xf),
            _ => None,
        };
        let mut pushes = 0;
        if mode != BlendMode::Normal {
            s.push_blend_mode(blend(mode));
            pushes += 1;
        }
        if let Some(paint) = tiling {
            s.set_stroke(None);
            s.set_fill(Some(Fill { paint, opacity: norm(opacity), rule }));
            s.draw_path(clip);
            s.set_fill(None);
        } else {
            s.push_clip_path(clip, &rule);
            pushes += 1;
            if opacity < 1.0 {
                s.push_opacity(norm(opacity));
                pushes += 1;
            }
            let doc = self.doc;
            match p {
                Paint::Pattern { pattern, xf } => {
                    if let Some(def) = doc.pattern(pattern) {
                        self.warn("pattern fills nested more than 4 patterns deep, or with tiles too large for PDF, are written as their tiles");
                        for inst in def.instances_in(*xf, area) {
                            self.node(s, &inst, area, true);
                        }
                    }
                }
                Paint::Gradient(g) => self.field_image(s, g, bounds, area, fill),
                _ => {}
            }
        }
        for _ in 0..pushes {
            s.pop();
        }
        true
    }

    /// Paint stroke `st` of the shape `bp` (`path`), whose geometric bounds `bounds` place its
    /// unplaced gradients.
    #[allow(clippy::too_many_arguments)]
    pub(super) fn stroke(&mut self, s: &mut Surface, bp: &BezPath, path: &Path, r: FillRule, st: &StrokeLayer, page: Rect, bounds: Rect) {
        if !stroke::is_plain(st) && self.brush_art(s, bp, st, page) {
            return;
        }
        if self.area_paint(&st.paint, false) && st.path_gradient().is_none() {
            // The area the stroke paints (dashes, caps, joins, profile, arrowheads, alignment), as
            // Outline Stroke makes it, painted with the pattern's tiles or the gradient's image (a
            // gradient along or across the stroke is written as slices below).
            let region = stroke::outline_region(&vectorcraft_geom::PathData::from_bezpath(bp), r, st).to_bezpath();
            if let Some(clip) = to_path(s, &region) {
                let area = region.bounding_box();
                self.area(s, &clip, krilla::paint::FillRule::NonZero, &st.paint, (st.opacity, st.blend), st.paint_bounds(bounds), area, false);
            }
            return;
        }
        let Some(paint) = self.paint(s, &st.paint, st.paint_bounds(bounds)) else { return };
        let w = stroke::for_writer(bp, st);
        // A stroke whose width, caps or miter spikes reach beyond [`MAX_COORD`] is left out.
        if !writable(s, Affine::IDENTITY, w.reach(st, bp.control_box()).inflate(1.0, 1.0)) {
            return;
        }
        let mut pushes = 0;
        if st.blend != BlendMode::Normal {
            s.push_blend_mode(blend(st.blend));
            pushes += 1;
        }
        match w.side {
            Some(StrokeAlign::Inside) => {
                s.push_clip_path(path, &rule(r));
                pushes += 1;
            }
            Some(StrokeAlign::Outside) => {
                // Clip to everything outside the path: a frame around all the stroke reaches
                // (miter spikes included) plus the path, even-odd.
                let mut outside = w.reach(st, bounds).inflate(1.0, 1.0).to_path(0.1);
                outside.extend(bp.iter());
                if let Some(p) = to_path(s, &outside) {
                    s.push_clip_path(&p, &krilla::paint::FillRule::EvenOdd);
                    pushes += 1;
                }
            }
            _ => {}
        }
        match &w.shape {
            WrittenShape::Stroke { width } => {
                let dash = st.dash.as_ref().filter(|d| d.is_dashed()).map(|d| {
                    let mut pat: Vec<f32> = d.pattern.iter().map(|v| *v as f32).collect();
                    if pat.len() % 2 == 1 {
                        pat.extend(pat.clone());
                    }
                    // An offset beyond [`MAX_COORD`] is written as its remainder after whole
                    // periods of the pattern.
                    let period: f64 = pat.iter().copied().map(f64::from).sum();
                    let offset = if in_range(&[d.offset]) { d.offset } else { d.offset.rem_euclid(period) };
                    StrokeDash { array: pat, offset: if offset.is_finite() { offset as f32 } else { 0.0 } }
                });
                s.set_fill(None);
                s.set_stroke(Some(Stroke {
                    paint,
                    width: *width as f32,
                    miter_limit: st.miter_limit.max(1.0) as f32,
                    line_cap: match st.cap {
                        LineCap::Butt => krilla::paint::LineCap::Butt,
                        LineCap::Round => krilla::paint::LineCap::Round,
                        LineCap::Square => krilla::paint::LineCap::Square,
                    },
                    line_join: match st.join {
                        LineJoin::Miter => krilla::paint::LineJoin::Miter,
                        LineJoin::Round => krilla::paint::LineJoin::Round,
                        LineJoin::Bevel => krilla::paint::LineJoin::Bevel,
                    },
                    opacity: norm(st.opacity),
                    dash,
                }));
                s.draw_path(path);
                s.set_stroke(None);
            }
            WrittenShape::Fill(outlines) if st.path_gradient().is_some() => {
                // A gradient along or across the stroke: slices clipped to its outlines, under
                // the stroke's opacity as a group.
                if let Some(ws) = stroke::written_slices(bp, r, st, outlines)
                    && let Some(clip) = to_path(s, &ws.clip)
                {
                    self.warn("gradients along or across strokes are exported as slices of linear gradients");
                    if st.opacity < 1.0 {
                        s.push_opacity(norm(st.opacity));
                        pushes += 1;
                    }
                    s.push_clip_path(&clip, &krilla::paint::FillRule::NonZero);
                    s.set_stroke(None);
                    for (shape, paint) in &ws.slices {
                        let b = shape.bounding_box();
                        if let (Some(paint), Some(p)) = (self.paint(s, paint, b), to_path(s, shape)) {
                            s.set_fill(Some(Fill { paint, opacity: NormalizedF32::ONE, rule: krilla::paint::FillRule::NonZero }));
                            s.draw_path(&p);
                        }
                    }
                    s.set_fill(None);
                    s.pop();
                }
            }
            WrittenShape::Fill(outlines) => {
                // The line and its arrowheads overlap: they take the opacity once, as a group.
                let grouped = outlines.len() > 1 && st.opacity < 1.0;
                if grouped {
                    s.push_opacity(norm(st.opacity));
                    pushes += 1;
                }
                let opacity = if grouped { NormalizedF32::ONE } else { norm(st.opacity) };
                s.set_stroke(None);
                s.set_fill(Some(Fill { paint, opacity, rule: krilla::paint::FillRule::NonZero }));
                for outline in outlines {
                    if let Some(p) = to_path(s, outline) {
                        s.draw_path(&p);
                    }
                }
                s.set_fill(None);
            }
        }
        for _ in 0..pushes {
            s.pop();
        }
    }

    /// Paint stroke `st` of the shape `bp` with its brush art (the stroke's opacity and blend mode
    /// over all of it). False when it has no known brush.
    fn brush_art(&mut self, s: &mut Surface, bp: &BezPath, st: &StrokeLayer, page: Rect) -> bool {
        let doc = self.doc;
        let brushes = self.brushes.get_or_insert_with(|| vectorcraft_brush::library(doc));
        let Some(b) = st.brush.as_deref().and_then(|name| brushes.iter().find(|b| b.name == name)) else { return false };
        let art = vectorcraft_brush::stroke_pieces(doc, b, bp, st);
        let mut pushes = 0;
        if st.blend != BlendMode::Normal {
            s.push_blend_mode(blend(st.blend));
            pushes += 1;
        }
        if st.opacity < 1.0 {
            s.push_opacity(norm(st.opacity));
            pushes += 1;
        }
        for piece in &art {
            self.node(s, piece, page, false);
        }
        for _ in 0..pushes {
            s.pop();
        }
        true
    }
}