refactor(text): move layout.rs items to layout/{bidi,breaking,driver,flow,on_path,region,ruby,vertical}.rs

crates/text/src/layout/bidi.rs

@@ -0,0 +1,108 @@
+use super::*;
+
+/// The bidirectional resolution (UAX #9) of paragraph `text`, its base direction `direction` or,
+/// without one, from its first strong character. `None` for the usual paragraph with nothing right
+/// to left in it (no right-to-left character or direction), which skips the algorithm.
+pub(crate) fn para_bidi(text: &str, direction: Option<ParaDirection>) -> Option<BidiInfo<'_>> {
+    use unicode_bidi::BidiClass::{AL, AN, FSI, R, RLE, RLI, RLO};
+    let rtl_set = direction == Some(ParaDirection::RightToLeft);
+    if !rtl_set && !text.chars().any(|c| matches!(unicode_bidi::bidi_class(c), R | AL | AN | RLE | RLO | RLI | FSI)) {
+        return None;
+    }
+    let level = direction.map(|d| if d == ParaDirection::RightToLeft { Level::rtl() } else { Level::ltr() });
+    Some(BidiInfo::new(text, level))
+}
+
+/// [`para_bidi`] for a paragraph whose characters in `set` (byte ranges of `text`, in order and not
+/// overlapping, from [`Ctx::char_directions`]) have a Character Direction: each range is resolved
+/// as a Unicode bidi embedding, as if an LRE or RLE stood before it and a PDF after it (UAX #9 X2,
+/// X3, X7). The levels, classes and paragraphs come back for the bytes of `text`. The paragraph's own
+/// direction is unchanged: the first strong character is found inside embeddings too (P2).
+pub(crate) fn para_bidi_with<'a>(text: &'a str, direction: Option<ParaDirection>, set: &[(Range<usize>, ParaDirection)]) -> Option<BidiInfo<'a>> {
+    let plain = para_bidi(text, direction);
+    if set.is_empty() || (plain.is_none() && set.iter().all(|(_, d)| *d == ParaDirection::LeftToRight)) {
+        // A left-to-right embedding in left-to-right text takes an even level: its order is the same.
+        return plain;
+    }
+    // The text with the embedding controls, and where each byte of `text` is in it.
+    let mut marked = String::with_capacity(text.len() + set.len() * 6);
+    let mut at_byte: Vec<usize> = Vec::with_capacity(text.len());
+    let mut copy = |marked: &mut String, from: usize, to: usize| {
+        if let Some(s) = text.get(from..to) {
+            at_byte.extend(marked.len()..marked.len() + s.len());
+            marked.push_str(s);
+        }
+    };
+    let mut done = 0;
+    for (r, d) in set {
+        let (a, b) = (r.start.max(done).min(text.len()), r.end.min(text.len()));
+        if a >= b {
+            continue;
+        }
+        copy(&mut marked, done, a);
+        marked.push(if *d == ParaDirection::RightToLeft { '\u{202B}' } else { '\u{202A}' });
+        copy(&mut marked, a, b);
+        marked.push('\u{202C}');
+        done = b;
+    }
+    copy(&mut marked, done, text.len());
+    let level = direction.map(|d| if d == ParaDirection::RightToLeft { Level::rtl() } else { Level::ltr() });
+    let info = BidiInfo::new(&marked, level);
+    let back = |i: usize| at_byte.partition_point(|&m| m < i);
+    let paragraphs =
+        info.paragraphs.iter().map(|p| unicode_bidi::ParagraphInfo { range: back(p.range.start)..back(p.range.end), level: p.level }).collect();
+    Some(BidiInfo {
+        text,
+        original_classes: at_byte.iter().filter_map(|&i| info.original_classes.get(i).copied()).collect(),
+        levels: at_byte.iter().filter_map(|&i| info.levels.get(i).copied()).collect(),
+        paragraphs,
+    })
+}
+
+/// Does the paragraph run right to left ([`para_bidi`])?
+pub(crate) fn is_rtl(bidi: Option<&BidiInfo<'_>>) -> bool {
+    bidi.and_then(|b| b.paragraphs.first()).is_some_and(|p| p.level.is_rtl())
+}
+
+/// The visual order of a line's `glyphs` (indices into them), whole shaping clusters reordered
+/// (UAX #9 L1–L2) for the line `line` (bytes of the text) of the paragraph starting at byte
+/// `paragraph_start`; their own order when nothing is right to left (`bidi` None).
+pub(super) fn visual_order(bidi: Option<&BidiInfo<'_>>, paragraph_start: usize, line: Range<usize>, glyphs: &[SGlyph]) -> Vec<usize> {
+    let Some((bidi, para)) = bidi.filter(|b| b.has_rtl()).and_then(|b| Some((b, b.paragraphs.first()?))) else {
+        return (0..glyphs.len()).collect();
+    };
+    if glyphs.is_empty() {
+        return vec![];
+    }
+    let levels = bidi.reordered_levels(para, line.start.saturating_sub(paragraph_start)..line.end.saturating_sub(paragraph_start));
+    // A list marker (length 0) is a cluster of its own.
+    let mut clusters: Vec<Range<usize>> = Vec::new();
+    for (i, g) in glyphs.iter().enumerate() {
+        if i > 0 && glyphs.get(i - 1).is_some_and(|p| p.byte == g.byte && (p.len == 0) == (g.len == 0)) {
+            if let Some(c) = clusters.last_mut() {
+                c.end = i + 1;
+            }
+        } else {
+            clusters.push(i..i + 1);
+        }
+    }
+    // A list marker is at the paragraph's level, and at a right-to-left one its tab is drawn
+    // before (left of) its characters.
+    let cluster_levels: Vec<_> = clusters
+        .iter()
+        .filter_map(|c| glyphs.get(c.start))
+        .map(|g| if g.len == 0 { g.level } else { levels.get(g.byte.saturating_sub(paragraph_start)).copied().unwrap_or(g.level) })
+        .collect();
+    let reversed = |i: usize| glyphs.get(clusters.get(i).map_or(0, |c| c.start)).is_some_and(|g| g.len == 0 && g.level.is_rtl());
+    unicode_bidi::BidiInfo::reorder_visual(&cluster_levels)
+        .into_iter()
+        .filter_map(|i| clusters.get(i).map(|c| (c.clone(), reversed(i))))
+        .flat_map(|(c, rev)| {
+            let mut v: Vec<usize> = c.collect();
+            if rev {
+                v.reverse();
+            }
+            v
+        })
+        .collect()
+}

crates/text/src/layout/breaking.rs

@@ -0,0 +1,577 @@
+use super::region::Region;
+use super::*;
+
+/// Vertical metrics of a line: (ascent, descent, leading, cap height, x height).
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub(super) struct Metrics {
+    pub(super) asc: f64,
+    pub(super) desc: f64,
+    pub(super) lead: f64,
+    pub(super) cap: f64,
+    pub(super) xh: f64,
+    /// Height of the top of the ideographic em box above the baseline.
+    pub(super) top: f64,
+}
+
+impl Metrics {
+    pub(super) fn of(g: &SGlyph) -> Self {
+        let em = g.face.units_per_em() * g.sy;
+        Self { asc: g.ascent, desc: g.descent, lead: g.leading, cap: g.cap, xh: g.xh, top: (g.face.ideographic_centre() + 0.5) * em }
+    }
+    pub(super) fn max(g: &[SGlyph]) -> Option<Self> {
+        let mut it = g.iter();
+        let first = Self::of(it.next()?);
+        Some(it.fold(first, |m, g| Self {
+            asc: m.asc.max(g.ascent),
+            desc: m.desc.max(g.descent),
+            lead: m.lead.max(g.leading),
+            cap: m.cap.max(g.cap),
+            xh: m.xh.max(g.xh),
+            top: m.top.max(Self::of(g).top),
+        }))
+    }
+    /// Distance from the frame top to the first baseline.
+    pub(super) fn first_baseline(&self, fb: FirstBaseline, min: f64) -> f64 {
+        let v = match fb {
+            FirstBaseline::Ascent => self.asc,
+            FirstBaseline::CapHeight => self.cap,
+            FirstBaseline::XHeight => self.xh,
+            FirstBaseline::Leading => self.lead,
+            FirstBaseline::Fixed => 0.0,
+        };
+        v.max(min)
+    }
+}
+
+/// Where the next line goes: the region being filled and the previous baseline in it.
+#[derive(Clone)]
+pub(super) struct Pen<'r> {
+    pub(super) regions: Option<&'r [Region]>,
+    pub(super) ri: usize,
+    pub(super) prev: Option<f64>,
+    pub(super) pending: f64,
+    pub(super) fb: FirstBaseline,
+    pub(super) fb_min: f64,
+    /// Further spans at the current baseline (text wrapping on both sides of an object).
+    pub(super) queued: Vec<(f64, f64, f64)>,
+    /// Leading measured from em box top to em box top: where the next line's em box top goes.
+    pub(super) model: LeadingModel,
+    pub(super) next_top: Option<f64>,
+    /// The narrowest word no line from here down is wide enough for (see [`Pen::place`]).
+    pub(super) no_room_for: f64,
+}
+
+/// The largest number of steps layout takes to move a line down a frame cell to find room for it:
+/// in a cell taller than this many leads, a step is the cell's height divided by this.
+const MAX_STEPS: usize = 100_000;
+
+impl Pen<'_> {
+    /// Baseline and horizontal span for a line with estimated metrics `est` and indents that starts
+    /// with a word `word` wide; `None` = the frame is full (overflow).
+    /// In a frame that isn't a rectangle, lines too short for the word are left empty and it moves
+    /// down to the first one wide enough. Only when no line is does it go on the first line with
+    /// room for any text, and get broken there.
+    /// The `bool` is true for a further span at the previous line's baseline.
+    pub(super) fn place(&mut self, est: Metrics, ind_l: f64, ind_r: f64, word: f64) -> Option<(f64, f64, f64, bool)> {
+        if word > 0.0 && word < self.no_room_for {
+            let mut pen = self.clone();
+            if let Some(placed) = pen.place_at_least(est, ind_l, ind_r, word) {
+                *self = pen;
+                return Some(placed);
+            }
+            // Lines further down are no wider for this word: don't search for it, or a wider one, again.
+            self.no_room_for = word;
+        }
+        self.place_at_least(est, ind_l, ind_r, 0.0)
+    }
+
+    /// [`Pen::place`], skipping lines of a non-rectangular frame narrower than `min`.
+    fn place_at_least(&mut self, est: Metrics, ind_l: f64, ind_r: f64, min: f64) -> Option<(f64, f64, f64, bool)> {
+        let Some(regions) = self.regions else {
+            let b = self.prev.map_or(0.0, |b| self.next_baseline(b, est));
+            return Some((b, f64::NEG_INFINITY, f64::INFINITY, false));
+        };
+        if !self.queued.is_empty() {
+            let (b, x0, x1) = self.queued.remove(0);
+            return Some((b, x0, x1, true));
+        }
+        loop {
+            let r = regions.get(self.ri)?;
+            let mut baseline = match self.prev {
+                None if self.model == LeadingModel::EmBoxTop => r.top() + r.shift + est.top.max(self.fb_min),
+                None => r.top() + r.shift + est.first_baseline(self.fb, self.fb_min),
+                Some(b) => self.next_baseline(b, est) + r.gap,
+            };
+            // The baseline moves down the cell a lead at a time, or a `MAX_STEPS`th of the cell's
+            // height when that is more, in at most `MAX_STEPS` steps.
+            let step = est.lead.max(1.0).max(r.cell.height() / MAX_STEPS as f64);
+            for _ in 0..=MAX_STEPS {
+                if baseline + est.desc > r.bottom() + 0.01 {
+                    break;
+                }
+                // A rectangle's lines are all as wide: none below has more room for the word
+                // (until wrap shapes can narrow the first baseline: they stay bounded).
+                let constant = (r.rect || r.polys.is_empty()) && r.wraps.is_empty();
+                let min = if constant { 0.0 } else { min };
+                let fits = |&(a, b): &(f64, f64)| {
+                    let room = b - a - ind_l - ind_r;
+                    room > est.asc.max(1.0) && room + EPS >= min
+                };
+                if r.wraps.is_empty() {
+                    match r.span(baseline - est.asc, baseline + est.desc) {
+                        Some(s) if fits(&s) => return Some((baseline, s.0, s.1, false)),
+                        // Too narrow here is too narrow all the way down the cell: next cell.
+                        Some(_) if constant => break,
+                        _ => baseline += step,
+                    }
+                } else {
+                    // Wrap objects can split a line: fill every span, left to right.
+                    let mut spans: Vec<(f64, f64)> = r.spans(baseline - est.asc, baseline + est.desc).into_iter().filter(fits).collect();
+                    if spans.is_empty() {
+                        baseline += step;
+                        continue;
+                    }
+                    let (a, b) = spans.remove(0);
+                    self.queued = spans.into_iter().map(|(a, b)| (baseline, a, b)).collect();
+                    return Some((baseline, a, b, false));
+                }
+            }
+            // Next row/column.
+            self.ri += 1;
+            self.prev = None;
+            self.pending = 0.0;
+            self.queued.clear();
+        }
+    }
+    pub(super) fn bottom(&self) -> f64 {
+        self.regions.and_then(|r| r.get(self.ri)).map_or(f64::INFINITY, |r| r.bottom())
+    }
+    /// The baseline of the line after the one at `prev`, for a line of metrics `est`.
+    fn next_baseline(&self, prev: f64, est: Metrics) -> f64 {
+        match (self.model, self.next_top) {
+            (LeadingModel::EmBoxTop, Some(top)) => top + est.top + self.pending,
+            _ => prev + est.lead + self.pending,
+        }
+    }
+    /// A line was set at `baseline` with metrics `m`: where the next one goes from.
+    pub(super) fn settled(&mut self, baseline: f64, m: Metrics) {
+        self.prev = Some(baseline);
+        self.next_top = Some(baseline - m.top + m.lead);
+    }
+}
+
+/// Advance of a tab at pen position `x`: up to the next stop after it (explicit stops first, then
+/// every ½ inch), and the leader of that stop (default stops have none). Right, centre and decimal
+/// stops align the text that follows (`rest`, up to the next tab) on the stop.
+pub(super) fn tab_advance<'t>(tabs: &'t [vectorcraft_doc::TabStop], origin: f64, x: f64, rest: &[SGlyph]) -> (f64, &'t str) {
+    use vectorcraft_doc::TabAlign;
+    let rel = x - origin;
+    let seg: Vec<&SGlyph> = rest.iter().take_while(|g| g.ch != '\t').collect();
+    let width: f64 = seg.iter().map(|g| g.adv).sum();
+    let target = |pos: f64, align: TabAlign, on: char| match align {
+        TabAlign::Left => pos,
+        TabAlign::Right => pos - width,
+        TabAlign::Center => pos - width / 2.0,
+        TabAlign::Decimal => pos - seg.iter().take_while(|g| g.ch != on).map(|g| g.adv).sum::<f64>(),
+    };
+    let explicit = tabs.iter().find_map(|t| {
+        let at = target(t.position, t.align, t.align_on);
+        (at > rel + 1e-6).then_some((at, t.leader.as_str()))
+    });
+    let (at, leader) = explicit.unwrap_or_else(|| {
+        let last = tabs.iter().map(|t| t.position).fold(0.0, f64::max).max(0.0);
+        let base = rel.max(last);
+        (((base / vectorcraft_doc::text::DEFAULT_TAB_INTERVAL).floor() + 1.0) * vectorcraft_doc::text::DEFAULT_TAB_INTERVAL, "")
+    });
+    ((at - rel).max(0.0), leader)
+}
+
+/// The width of glyphs `from..to` of `sg` set on a line whose content starts `x_start` from the
+/// tab origin: tabs of the text take what [`tab_advance`] gives them, not the width of their
+/// glyph. The tab after a list marker (length 0) keeps its own width.
+pub(super) fn set_width(sg: &[SGlyph], from: usize, to: usize, tabs: &[vectorcraft_doc::TabStop], x_start: f64) -> f64 {
+    let mut x = x_start;
+    for (j, g) in sg.iter().enumerate().take(to).skip(from) {
+        x += if g.ch == '\t' && g.len > 0 { tab_advance(tabs, 0.0, x, sg.get(j + 1..to).unwrap_or_default()).0 } else { g.adv };
+    }
+    x - x_start
+}
+
+/// Most copies of a leader drawn in one tab: a tiny type size and a far stop must not make
+/// millions of outlines.
+const MAX_LEADER_COPIES: f64 = 4096.0;
+
+/// The outline of a tab leader: `leader`'s characters, in the font and size of tab `g`, repeated
+/// across the tab's gap `from..to` on baseline `y`. Copies sit on a grid of the leader's width
+/// from `origin` (where tab stops are measured from), so the leaders of lines above one another
+/// line up; only whole copies are drawn. Characters the font lacks draw nothing.
+pub(super) fn leader_outline(db: &FontDb, g: &SGlyph, leader: &str, origin: f64, from: f64, to: f64, y: f64) -> BezPath {
+    let mut out = BezPath::new();
+    let glyphs: Vec<(u32, f64)> = leader
+        .chars()
+        .filter(|c| !c.is_control())
+        .map(|c| {
+            let gid = g.face.glyph_for(c);
+            (gid, g.face.advance(gid) * g.sx)
+        })
+        .collect();
+    let width: f64 = glyphs.iter().map(|(_, a)| a).sum();
+    if !(width > EPS && width.is_finite() && from.is_finite() && to.is_finite()) {
+        return out;
+    }
+    let first = ((from - origin) / width - EPS).ceil();
+    let copies = (((to - origin) / width + EPS).floor() - first).clamp(0.0, MAX_LEADER_COPIES) as usize;
+    let local = Affine::rotate(-g.rotation.to_radians()) * Affine::translate((0.0, -g.bshift)) * Affine::scale_non_uniform(g.sx, g.sy);
+    for k in 0..copies {
+        let mut pen = origin + (first + k as f64) * width;
+        for &(gid, adv) in &glyphs {
+            if gid != 0 {
+                let m = Affine::translate((pen, y)) * local;
+                out.extend(db.outline(&g.face, gid).elements().iter().map(|el| m * *el));
+            }
+            pen += adv;
+        }
+    }
+    out
+}
+
+/// Width of the word starting at glyph `i`: its advances up to the first break opportunity (spaces
+/// left out, the hyphen of a soft hyphen in), the least room a line needs not to break inside it.
+/// A list marker at `i` (glyphs of length 0) counts whole, with the word after it.
+pub(super) fn word_width(g: &[SGlyph], i: usize) -> f64 {
+    /// Glyphs measured at most: a word wrapped over many lines is measured again from each line's
+    /// start, and one this long is broken inside whatever cell it meets.
+    const MAX_GLYPHS: usize = 1024;
+    let rest = g.get(i..).unwrap_or_default();
+    let marker = rest.iter().take_while(|gl| gl.len == 0).count();
+    let mut w: f64 = rest.iter().take(marker).map(|gl| gl.adv).sum();
+    for gl in rest.iter().skip(marker).take(MAX_GLYPHS) {
+        if gl.is_space() {
+            break;
+        }
+        if gl.is_soft_hyphen() {
+            return w + hyphen_glyph(gl).adv;
+        }
+        w += gl.adv;
+        if gl.break_after() {
+            break;
+        }
+    }
+    w
+}
+
+/// Greedy break: returns (end glyph index, hyphenated) for a line starting at `i` of `width`.
+/// With burasagari, a comma or full stop that doesn't fit ends the line, hanging outside it.
+/// `hyphenate` holds the paragraph's Hyphenation options and the Hyphenation Zone in force when
+/// the line may hyphenate a word; a line whose text before the overflowing word already ends
+/// within the zone breaks before that word. A tab is as wide as it is set: up to its next stop
+/// (`tabs`), with the line's content starting `x_start` from the tab origin.
+#[allow(clippy::too_many_arguments)]
+pub(super) fn break_line(
+    text: &str,
+    g: &[SGlyph],
+    i: usize,
+    width: f64,
+    tabs: &[vectorcraft_doc::TabStop],
+    x_start: f64,
+    hyphenate: Option<(&HyphenationOptions, f64)>,
+    burasagari: Burasagari,
+    kinsoku: Kinsoku,
+) -> (usize, bool) {
+    if !width.is_finite() {
+        return (g.len(), false);
+    }
+    let mut x = 0.0;
+    let mut last_break: Option<(usize, bool)> = None;
+    // A list marker (length 0) is a cluster of its own; the line holds it and at least the first
+    // cluster after it.
+    let first = i + g.get(i..).unwrap_or_default().iter().take_while(|h| h.len == 0).count();
+    let mut j = i;
+    while j < g.len() {
+        let gl = &g[j];
+        let mut cluster_end = j + 1;
+        while g.get(cluster_end).is_some_and(|next| next.byte == gl.byte && (next.len == 0) == (gl.len == 0)) {
+            cluster_end += 1;
+        }
+        // No Break: the marked characters stay on one line, including across a space inside the run.
+        if gl.no_break {
+            while let Some(n) = g.get(cluster_end) {
+                if !n.no_break {
+                    break;
+                }
+                let b = n.byte;
+                cluster_end += 1;
+                while g.get(cluster_end).is_some_and(|next| next.byte == b) {
+                    cluster_end += 1;
+                }
+            }
+        }
+        let cluster_width: f64 = if gl.ch == '\t' {
+            tab_advance(tabs, 0.0, x_start + x, g.get(cluster_end..).unwrap_or_default()).0
+        } else {
+            g[j..cluster_end].iter().map(|glyph| glyph.adv).sum()
+        };
+        if j > first && !gl.is_space() && x + cluster_width > width + EPS {
+            // It ends the line with the spaces after it.
+            if burasagari != Burasagari::None && hangs(gl) && kinsoku_allows(g, cluster_end - 1, kinsoku) {
+                let mut end = cluster_end;
+                while g.get(end).is_some_and(SGlyph::is_space) {
+                    end += 1;
+                }
+                return (end, false);
+            }
+            break;
+        }
+        x += cluster_width;
+        let last = &g[cluster_end - 1];
+        if last.break_after() && last.len > 0 && kinsoku_allows(g, cluster_end - 1, kinsoku) && !splits_no_break(g, cluster_end) {
+            if last.is_soft_hyphen() {
+                if x + hyphen_glyph(last).adv <= width + EPS {
+                    last_break = Some((cluster_end, true));
+                }
+            } else {
+                last_break = Some((cluster_end, false));
+            }
+        }
+        j = cluster_end;
+    }
+    if j >= g.len() {
+        return (g.len(), false);
+    }
+    // Hyphenate the word that overflows.
+    let word_start = last_break.map_or(i, |b| b.0);
+    let in_zone = |zone: f64| {
+        let mut te = word_start;
+        while te > i && g[te - 1].is_space() {
+            te -= 1;
+        }
+        te > i && zone > 0.0 && width - g[i..te].iter().map(|g| g.adv).sum::<f64>() <= zone + EPS
+    };
+    if let Some((opts, zone)) = hyphenate
+        && g[j].is_letter()
+        && !in_zone(zone)
+    {
+        let mut we = j;
+        while we < g.len() && !g[we].is_space() && !g[we].break_after() {
+            we += 1;
+        }
+        let x_ws: f64 = g[i..word_start].iter().map(|g| g.adv).sum();
+        let pts: Vec<usize> = hyphen_breaks(text, g, word_start, we, opts)
+            .into_iter()
+            .filter(|&k| k > 0 && kinsoku_allows(g, k - 1, kinsoku) && !splits_no_break(g, k))
+            .collect();
+        for &k in pts.iter().rev() {
+            if k <= j && k > i {
+                let w = x_ws + g[word_start..k].iter().map(|g| g.adv).sum::<f64>() + hyphen_glyph(&g[k - 1]).adv;
+                if w <= width + EPS {
+                    return (k, true);
+                }
+            }
+        }
+    }
+    // Break candidates and greedy overflow are cluster boundaries; hyphenation also returns only
+    // cluster starts, so the resulting end always keeps each source cluster together.
+    let (end, hy) = match last_break {
+        Some(b) if b.0 > i => b,
+        _ => (j, false),
+    };
+    (end, hy)
+}
+
+/// Can glyph `g` hang outside the line (burasagari)? An East Asian comma or full stop, full width
+/// (、。，．) or half width (､｡); not a closing bracket, nor Latin punctuation (Latin text keeps
+/// its line breaks and composer). Never an inline graphic (U+FFFC).
+pub(super) fn hangs(g: &SGlyph) -> bool {
+    g.inline.is_none() && matches!(g.ch, '、' | '。' | '，' | '．' | '､' | '｡') && g.tcy.is_none()
+}
+
+/// Optical Margin Alignment: the share of glyph `g`'s advance that hangs outside the margin when
+/// `g` starts or ends a line. Quotation marks, hyphens, full stops and commas hang whole, and
+/// asterisks, tildes, ellipses, en and em dashes, colons and semicolons hang by half (the amounts
+/// published for Roman Hanging Punctuation). A, V, W, Y, v, w and y hang by a tenth of their
+/// advance, VectorCraft's own amount for their slanted sides. Other characters, East Asian
+/// punctuation (which burasagari hangs) and inline graphics don't hang.
+pub(super) fn optical_share(g: &SGlyph) -> f64 {
+    if g.inline.is_some() || g.tcy.is_some() {
+        return 0.0;
+    }
+    match g.ch {
+        '-' | '\u{2010}' | '\u{2011}' | '.' | ',' => 1.0,
+        c if is_quote(c) => 1.0,
+        '*' | '~' | '…' | '–' | '—' | ':' | ';' => 0.5,
+        'A' | 'V' | 'W' | 'Y' | 'v' | 'w' | 'y' => 0.1,
+        _ => 0.0,
+    }
+}
+
+/// Roman Hanging Punctuation: the share of glyph `g`'s advance that hangs outside the margin when
+/// `g` starts or ends a line: [`optical_share`]'s punctuation, and no letters.
+pub(super) fn roman_share(g: &SGlyph) -> f64 {
+    if g.ch.is_alphabetic() { 0.0 } else { optical_share(g) }
+}
+
+/// A punctuation mark that hangs ([`optical_share`]), not a letter.
+pub(super) fn optical_punct(g: &SGlyph) -> bool {
+    !g.ch.is_alphabetic() && optical_share(g) > 0.0
+}
+
+/// A single or double quotation mark: straight, curly, low-9 or reversed-9.
+fn is_quote(c: char) -> bool {
+    matches!(c, '\'' | '"' | '‘' | '’' | '‚' | '‛' | '“' | '”' | '„' | '‟')
+}
+
+/// Optical Margin Alignment and Roman Hanging Punctuation: how far a line hangs outside its left
+/// and right margins, from the glyph at each end of `line` (its glyphs in visual order, each with
+/// the advance it is set with) and its `share` ([`optical_share`] or [`roman_share`]), and how many glyphs hang at each end → (left, right, left glyphs,
+/// right glyphs). A punctuation mark followed by a quotation mark hangs together with it: `."`
+/// ending a line and `'"` starting one hang both their glyphs. A line of one glyph hangs at
+/// neither end.
+pub(super) fn optical_hangs(line: &[(&SGlyph, f64)], share: fn(&SGlyph) -> f64) -> (f64, f64, usize, usize) {
+    let n = line.len();
+    if n < 2 {
+        return (0.0, 0.0, 0, 0);
+    }
+    let hang = |k: usize| line.get(k).map_or(0.0, |&(g, adv)| share(g) * adv.max(0.0));
+    let punct = |k: usize| line.get(k).is_some_and(|&(g, _)| optical_punct(g));
+    let quote = |k: usize| line.get(k).is_some_and(|&(g, _)| is_quote(g.ch) && share(g) > 0.0);
+    let mut left = hang(0);
+    // The glyphs that hang at the left; the right end takes none of them.
+    let mut taken = usize::from(left > 0.0);
+    if left > 0.0 && n > 2 && punct(0) && quote(1) {
+        left += hang(1);
+        taken = 2;
+    }
+    let mut right = hang(n - 1);
+    let mut right_glyphs = usize::from(right > 0.0);
+    if right > 0.0 && n > 2 && n - 2 >= taken && punct(n - 2) && quote(n - 1) {
+        right += hang(n - 2);
+        right_glyphs = 2;
+    }
+    (left, right, taken, right_glyphs)
+}
+
+/// Works as [`optical_hangs`] does for a right-to-left line, whose `line` is also in visual order.
+/// The line is read from right to left: `."` ending it hangs both its glyphs at the left, `'"` starting it hangs both at
+/// the right, and the right end takes its glyphs first.
+pub(super) fn optical_hangs_rtl(line: &[(&SGlyph, f64)], share: fn(&SGlyph) -> f64) -> (f64, f64, usize, usize) {
+    let reversed: Vec<(&SGlyph, f64)> = line.iter().rev().copied().collect();
+    let (right, left, right_glyphs, left_glyphs) = optical_hangs(&reversed, share);
+    (left, right, left_glyphs, right_glyphs)
+}
+
+/// Would a line ending at glyph index `end` split a No Break run?
+fn splits_no_break(g: &[SGlyph], end: usize) -> bool {
+    end > 0 && g.get(end - 1).is_some_and(|a| a.no_break) && g.get(end).is_some_and(|b| b.no_break)
+}
+
+/// Does kinsoku allow a line break after glyph `j`? Not after an opening bracket, nor before a
+/// closing one, a comma, a full stop, a small kana… (the character is pushed to the next line
+/// with the one before it).
+fn kinsoku_allows(g: &[SGlyph], j: usize, kinsoku: Kinsoku) -> bool {
+    g.get(j).is_some_and(|gl| kinsoku_between(gl.ch, g.get(j + 1).map(|n| n.ch), kinsoku))
+}
+
+/// Kinsoku for a break between `before` and `after` (none: the end of the paragraph): Hard keeps
+/// every character of the set off the line start and end, Soft lets 々, ー and small kana start a
+/// line, None allows the break.
+fn kinsoku_between(before: char, after: Option<char>, kinsoku: Kinsoku) -> bool {
+    match kinsoku {
+        Kinsoku::None => true,
+        Kinsoku::Hard => !no_line_end(before) && after.is_none_or(|c| !no_line_start(c)),
+        Kinsoku::Soft => !no_line_end(before) && after.is_none_or(|c| !no_line_start(c) || soft_line_start(c)),
+    }
+}
+
+#[cfg(test)]
+#[test]
+fn kinsoku_keeps_closing_marks_off_line_starts_and_opening_ones_off_line_ends() {
+    for (a, b) in [('字', '。'), ('弧', '」'), ('」', '、'), ('ャ', 'ー'), ('カ', 'ッ'), ('「', 'か'), ('（', '雅')] {
+        assert!(!kinsoku_between(a, Some(b), Kinsoku::Hard), "{a}{b}");
+    }
+    for (a, b) in [('。', '雅'), ('」', 'は'), ('字', '「'), ('の', '演')] {
+        assert!(kinsoku_between(a, Some(b), Kinsoku::Hard), "{a}{b}");
+    }
+    assert!(kinsoku_between('。', None, Kinsoku::Hard));
+}
+
+/// Soft kinsoku lets 々, ー and small kana (JLREQ cl-09's 々, cl-10, cl-11) start a line and keeps
+/// the rest of the set (half-width forms aren't in those classes); None allows any break.
+#[cfg(test)]
+#[test]
+fn soft_kinsoku_lets_small_kana_and_the_prolonged_sound_mark_start_a_line() {
+    for (a, b) in [('ャ', 'ー'), ('カ', 'ッ'), ('時', '々'), ('ト', 'ㇰ'), ('か', 'ゃ')] {
+        assert!(!kinsoku_between(a, Some(b), Kinsoku::Hard), "{a}{b}");
+        assert!(kinsoku_between(a, Some(b), Kinsoku::Soft), "{a}{b}");
+    }
+    for (a, b) in [('字', '。'), ('弧', '」'), ('「', 'か'), ('ｶ', 'ｯ'), ('ｶ', 'ｰ'), ('字', 'ゝ')] {
+        assert!(!kinsoku_between(a, Some(b), Kinsoku::Soft), "{a}{b}");
+        assert!(kinsoku_between(a, Some(b), Kinsoku::None), "{a}{b}");
+    }
+}
+
+/// Glyph indices inside `g[ws..we]` (a word) where a hyphenated break may go under `opts`.
+fn hyphen_breaks(text: &str, g: &[SGlyph], ws: usize, we: usize, opts: &HyphenationOptions) -> Vec<usize> {
+    // Strip leading/trailing punctuation (quotes, commas).
+    let (mut a, mut b) = (ws, we);
+    while a < b && !g[a].is_letter() {
+        a += 1;
+    }
+    while b > a && !g[b - 1].is_letter() {
+        b -= 1;
+    }
+    if b <= a || g[a..b].iter().any(|g| !g.is_letter()) {
+        return vec![];
+    }
+    let (s, e) = (g[a].byte, g[b - 1].byte + g[b - 1].len);
+    let Some(word) = text.get(s..e) else { return vec![] };
+    let offs: Vec<usize> = word.char_indices().map(|(o, _)| s + o).collect();
+    // The first glyph of each cluster start (not inside a ligature), by its byte: one pass, not a
+    // search for each point.
+    let mut starts = std::collections::HashMap::new();
+    for k in a + 1..b {
+        if g[k].byte != g[k - 1].byte {
+            starts.entry(g[k].byte).or_insert(k);
+        }
+    }
+    hyphen_points_with(word, opts).into_iter().filter_map(|ci| starts.get(offs.get(ci)?).copied()).collect()
+}
+
+/// Break candidates for the every-line composer: hyphenation points under `hyphenate` (the
+/// paragraph's Hyphenation options) when it is given. No break comes before a space: a line that
+/// may end after a dash, a Thai word or a space ends after the spaces that follow it, as in
+/// [`break_line`].
+pub(super) fn candidates(text: &str, g: &[SGlyph], hyphenate: Option<&HyphenationOptions>, kinsoku: Kinsoku) -> Vec<Breakpoint> {
+    let mut v = vec![];
+    let mut ws = 0;
+    for (j, gl) in g.iter().enumerate() {
+        let end_of_word = gl.is_space() || gl.break_after();
+        if end_of_word {
+            if let Some(opts) = hyphenate
+                && j > ws
+            {
+                for k in
+                    hyphen_breaks(text, g, ws, j, opts).into_iter().filter(|&k| k > 0 && kinsoku_allows(g, k - 1, kinsoku) && !splits_no_break(g, k))
+                {
+                    v.push(Breakpoint { end: k, hyphen: hyphen_glyph(&g[k - 1]).adv });
+                }
+            }
+            let hy = if gl.is_soft_hyphen() { hyphen_glyph(gl).adv } else { 0.0 };
+            if j + 1 < g.len() && g[j + 1].byte != gl.byte && !g[j + 1].is_space() && kinsoku_allows(g, j, kinsoku) && !splits_no_break(g, j + 1) {
+                v.push(Breakpoint { end: j + 1, hyphen: hy });
+            }
+            ws = j + 1;
+        }
+    }
+    if let Some(opts) = hyphenate
+        && g.len() > ws
+    {
+        for k in
+            hyphen_breaks(text, g, ws, g.len(), opts).into_iter().filter(|&k| k > 0 && kinsoku_allows(g, k - 1, kinsoku) && !splits_no_break(g, k))
+        {
+            v.push(Breakpoint { end: k, hyphen: hyphen_glyph(&g[k - 1]).adv });
+        }
+    }
+    v.sort_by_key(|b| b.end);
+    v.dedup_by_key(|b| b.end);
+    v
+}

crates/text/src/layout/driver.rs

@@ -0,0 +1,292 @@
+use super::flow::flow;
+use super::on_path::on_path;
+use super::region::Region;
+use super::ruby::ruby_layout;
+use super::vertical::{EM_CENTER, QUARTER_TURN, align_vertically, finish_bounds};
+use super::*;
+
+/// Lay out a text object into text-space glyph outlines (default [`LayoutOptions`]).
+pub fn layout(db: &FontDb, t: &TextObject) -> TextLayout {
+    let a = &t.area;
+    let opts = LayoutOptions {
+        rows: a.rows,
+        columns: a.columns,
+        gutter: a.gutter,
+        inset: a.inset,
+        first_baseline: a.first_baseline,
+        first_baseline_min: a.first_baseline_min,
+        vertical_align: a.vertical_align,
+        fit: a.fit,
+        ..LayoutOptions::default()
+    };
+    layout_with(db, t, &opts)
+}
+
+/// Area type in a frame too short for its first line draws nothing (type that doesn't fit its frame
+/// isn't drawn). For importers whose source shows that line: the frame is made taller, from its
+/// top, by what the first line needs. Whether it was.
+pub fn fit_first_line(db: &FontDb, t: &mut TextObject) -> bool {
+    let TextKind::Area { frame } = &t.kind else { return false };
+    let Some(b) = frame.bounds().filter(|b| b.height() > 1e-6) else { return false };
+    if !layout(db, t).lines.is_empty() {
+        return false;
+    }
+    // The height of its first line: the line's as point type.
+    let point = TextObject { kind: TextKind::Point, ..t.clone() };
+    let Some(need) = layout(db, &point).lines.first().map(|l| l.ascent + l.descent) else { return false };
+    // (A little more than it, for the rounding of the layout.)
+    let by = (need + 0.05) / b.height();
+    if !(by.is_finite() && by > 1.0) {
+        return false;
+    }
+    let taller = frame.transformed(Affine::translate((0.0, b.y0)) * Affine::scale_non_uniform(1.0, by) * Affine::translate((0.0, -b.y0)));
+    let short = std::mem::replace(&mut t.kind, TextKind::Area { frame: taller });
+    // Something else keeps the line out (a frame narrower than a letter): as the source has it.
+    if layout(db, t).lines.is_empty() {
+        t.kind = short;
+        return false;
+    }
+    true
+}
+
+/// The underline and strikethrough bars of `t` laid out as `layout` (#847): per run and line, a
+/// bar from the stretch's first glyph to its last one's advance, placed and sized by the font's
+/// own underline and strikeout metrics through the glyph's transform (so the size, baseline shift
+/// and scaling follow) → (run, bar in text space). Type on a path and vertical type have none yet.
+pub fn decorations(layout: &TextLayout, db: &FontDb, t: &TextObject) -> Vec<(usize, BezPath)> {
+    let mut out = vec![];
+    if layout.on_path || layout.vertical {
+        return out;
+    }
+    let glyphs = &layout.glyphs;
+    let mut i = 0;
+    while let Some(g) = glyphs.get(i) {
+        // The stretch: the glyphs of this run on this line, in a row. A list marker has no
+        // underline or strikethrough.
+        let marker = layout.marker_of(i).is_some();
+        let end = glyphs
+            .iter()
+            .enumerate()
+            .skip(i)
+            .position(|(k, h)| h.run != g.run || h.line != g.line || layout.marker_of(k).is_some() != marker)
+            .map_or(glyphs.len(), |n| i + n);
+        let stretch = glyphs.get(i..end).unwrap_or_default();
+        i = end.max(i + 1);
+        if marker {
+            continue;
+        }
+        let Some(style) = t.runs.get(g.run).map(|r| &r.style) else { continue };
+        if !(style.underline || style.strikethrough) {
+            continue;
+        }
+        let Some(face) = db.face_by_id(g.font_id) else { continue };
+        let (x0, x1) = stretch.iter().fold((f64::INFINITY, f64::NEG_INFINITY), |(a, b), h| {
+            let (s, e) = (h.origin.x, h.origin.x + h.advance);
+            (a.min(s).min(e), b.max(s).max(e))
+        });
+        for (on, (offset, thickness)) in [(style.underline, face.underline), (style.strikethrough, face.strikeout)] {
+            if !on {
+                continue;
+            }
+            // Font units run y down in the glyph's transform: the bar's top is at -offset.
+            let (top, bottom) = ((g.xf * Point::new(0.0, -offset)).y, (g.xf * Point::new(0.0, -offset + thickness)).y);
+            let bar = Rect::new(x0, top.min(bottom), x1, top.max(bottom));
+            if bar.width() > 0.0 && bar.height() > 0.0 && bar.width().is_finite() && bar.height().is_finite() {
+                out.push((g.run, bar.to_path(0.1)));
+            }
+        }
+    }
+    out
+}
+
+/// Most layout passes Shrink Text to Fit runs past the first (bisection plus the final pass).
+const SHRINK_PASSES: usize = 11;
+
+/// Lay out a text object with explicit options (area type rows/columns, inset, first baseline,
+/// fit, composer, OpenType features).
+pub fn layout_with(db: &FontDb, t: &TextObject, opts: &LayoutOptions) -> TextLayout {
+    let first = layout_once(db, t, opts);
+    match (opts.fit.min_scale(), &t.kind) {
+        (Some(min), TextKind::Area { .. }) if first.overflow => shrink_to_fit(db, t, opts, min).unwrap_or(first),
+        _ => first,
+    }
+}
+
+/// Shrink Text to Fit for text that overflows at full size: the largest scale in `min..1` at which
+/// it fits, searched by bisection over the first run's document size in steps of 0.1 pt (so its scaled size
+/// is a whole number of tenths of a point, the same every time). Down at `min` it lays out there,
+/// still overflowing. None (keep the full-size layout) when the text has no usable size.
+fn shrink_to_fit(db: &FontDb, t: &TextObject, opts: &LayoutOptions, min: f64) -> Option<TextLayout> {
+    // Exact size edits after object scaling may store a local size below 0.1. Fit in the
+    // same document points as the Character controls, independent of that representation.
+    let points = t.style_scale()?.points;
+    let size = t.runs.first().map(|r| r.style.size * points).filter(|s| s.is_finite() && *s >= 0.1)?;
+    if !(min.is_finite() && min < 1.0) {
+        return None;
+    }
+    let tenths = size * 10.0;
+    if !tenths.is_finite() {
+        return None;
+    }
+    // Candidate sizes k/10 pt for k in lo..hi: `hi` (full size, rounded down) is known to overflow
+    // unless it is below the full size; `lo` is the smallest allowed.
+    let mut lo = (tenths * min).ceil().max(1.0);
+    let mut hi = tenths.floor();
+    if hi < lo {
+        hi = lo;
+    }
+    let at = |k: f64| -> TextLayout {
+        let f = (k / tenths).clamp(min, 1.0);
+        let mut l = layout_once(db, &scaled(t, f), opts);
+        l.fit_scale = f;
+        l
+    };
+    let mut passes = 0;
+    let mut best: Option<TextLayout> = None;
+    // `hi` itself may fit when the size isn't a whole number of tenths.
+    if hi < tenths && hi > lo {
+        let l = at(hi);
+        passes += 1;
+        if !l.overflow {
+            return Some(l);
+        }
+    }
+    // Invariant: everything at `hi` or above overflows; `lo` fits or is the floor.
+    while hi - lo > 1.0 && passes + 1 < SHRINK_PASSES {
+        let mid = (lo + (hi - lo) * 0.5).floor();
+        let l = at(mid);
+        passes += 1;
+        if l.overflow {
+            hi = mid;
+        } else {
+            lo = mid;
+            best = Some(l);
+        }
+    }
+    // `best` is the layout at `lo` once `lo` has moved; at the floor it still needs laying out.
+    Some(best.unwrap_or_else(|| at(lo)))
+}
+
+/// `t` with every run's size, explicit leading and baseline shift scaled by `f`, inline art's own
+/// shift included (auto leading and the art's size follow the size; paragraph spacing stays).
+/// Shrink Text to Fit lays `t` out as `scaled(t, f)`, where `f` is the layout's
+/// [`TextLayout::fit_scale`], so the result holds the styles the text is drawn in.
+pub fn scaled(t: &TextObject, f: f64) -> TextObject {
+    let mut s = t.clone();
+    for r in &mut s.runs {
+        r.style.size *= f;
+        r.style.leading = r.style.leading.map(|l| l * f);
+        r.style.baseline_shift *= f;
+        if let Some(a) = &mut r.inline {
+            a.baseline_shift *= f;
+        }
+    }
+    s
+}
+
+/// One layout pass, without fitting.
+fn layout_once(db: &FontDb, t: &TextObject, opts: &LayoutOptions) -> TextLayout {
+    let text = t.plain_text();
+    let mut runs = Vec::with_capacity(t.runs.len());
+    let mut inlines = Vec::with_capacity(t.runs.len());
+    let mut off = 0;
+    for r in &t.runs {
+        runs.push((off..off + r.text.len(), &r.style));
+        // Only a well-formed inline run (one object replacement character) is a graphic.
+        inlines.push(r.inline.as_ref().filter(|_| crate::edit::is_inline_text(&r.text)));
+        off += r.text.len();
+    }
+    let mut paras = Vec::new();
+    let mut s = 0;
+    for (i, c) in text.char_indices() {
+        if c == '\n' {
+            paras.push(s..i);
+            s = i + 1;
+        }
+    }
+    paras.push(s..text.len());
+    let vertical = t.vertical;
+    let is_on_path = matches!(&t.kind, TextKind::OnPath { .. });
+    let vopts;
+    let opts = if vertical {
+        vopts = LayoutOptions { features: OtFeatures { vertical: true, ..opts.features }, ..opts.clone() };
+        &vopts
+    } else {
+        opts
+    };
+    let mut cx = Ctx {
+        on_path: is_on_path,
+        db,
+        text: &text,
+        runs,
+        inlines,
+        default: CharStyle::default(),
+        opts,
+        vertical,
+        system_layout: t.system_layout,
+        fractional_widths: t.fractional_widths,
+        out: TextLayout::default(),
+    };
+    // Vertical type: line space turned a quarter turn clockwise (lines become columns, each next
+    // one to the left). Point type's anchor is on the first column's centre line. Vertical path
+    // type stays on its path (each glyph turned across it in `emit`).
+    let line_xf = match &t.kind {
+        _ if !vertical => Affine::IDENTITY,
+        TextKind::OnPath { .. } => Affine::IDENTITY,
+        TextKind::Point => {
+            let first = cx.style_at(0);
+            let centre = db.style_face(first).map_or(EM_CENTER, |f| f.ideographic_centre());
+            Affine::translate((-centre * first.size, 0.0)) * QUARTER_TURN
+        }
+        _ => QUARTER_TURN,
+    };
+    match &t.kind {
+        TextKind::Point => flow(&mut cx, &paras, t, None),
+        TextKind::Area { frame } => {
+            let to_lines = line_xf.inverse();
+            let wrap: Vec<vectorcraft_doc::WrapShape> = if vertical {
+                t.wrap.iter().map(|w| vectorcraft_doc::WrapShape { path: w.path.transformed(to_lines), ..w.clone() }).collect()
+            } else {
+                t.wrap.clone()
+            };
+            let mut regions = Region::cells(&(to_lines * frame.to_bezpath()), opts, &wrap);
+            cx.out.frames = regions.iter().map(|r| line_xf.transform_rect_bbox(r.cell)).collect();
+            flow(&mut cx, &paras, t, Some(&regions));
+            if opts.vertical_align != VerticalAlign::Top {
+                align_vertically(&mut cx, &paras, t, &mut regions);
+            }
+        }
+        TextKind::OnPath { path, .. } => on_path(&mut cx, &paras, t, path),
+    }
+    // Ruby (furigana): placed over its base text in line space, before vertical type turns the
+    // lines into columns, so the same pass puts it above (right in vertical type) and widens the
+    // lines it sits on. Type on a path has no above/below; its ruby is left out for now.
+    if !is_on_path && !t.ruby.is_empty() {
+        ruby_layout(&mut cx, t);
+    }
+    if vertical && !is_on_path {
+        // Glyph origins, outlines and transforms to text space (lines stay in line space).
+        for g in &mut cx.out.glyphs {
+            g.outline.apply_affine(line_xf);
+            g.xf = line_xf * g.xf;
+            g.origin = line_xf * g.origin;
+            g.angle += std::f64::consts::FRAC_PI_2;
+        }
+        // Ruby glyphs are placed in line space too (upright, along the column, in the vertical
+        // pass); the same turn takes them to text space.
+        for g in &mut cx.out.ruby {
+            g.outline.apply_affine(line_xf);
+            g.xf = line_xf * g.xf;
+            g.origin = line_xf * g.origin;
+            g.angle += std::f64::consts::FRAC_PI_2;
+        }
+        for i in &mut cx.out.inlines {
+            i.xf = line_xf * i.xf;
+            i.bounds = line_xf.transform_rect_bbox(i.bounds);
+        }
+        cx.out.vertical = true;
+        cx.out.line_xf = line_xf;
+    }
+    finish_bounds(&mut cx.out);
+    cx.out
+}

crates/text/src/layout/flow.rs

@@ -0,0 +1,580 @@
+use super::bidi::{is_rtl, para_bidi_with, visual_order};
+use super::breaking::{
+    Metrics, Pen, break_line, candidates, hangs, leader_outline, optical_hangs, optical_hangs_rtl, optical_punct, optical_share, roman_share,
+    set_width, tab_advance, word_width,
+};
+use super::region::Region;
+use super::vertical::{EM_CENTER, align_shift, compress_punctuation, glyph_em, punct_half, space_japanese_and_latin};
+use super::*;
+
+/// Paragraphs longer than this (glyphs) are always broken line by line.
+const MAX_COMPOSE_GLYPHS: usize = 200_000;
+
+/// Every-line composition of paragraph glyphs `sg` if applicable (area text, justified or ragged,
+/// with uniform line metrics or in rectangular cells without text wrap); `None` falls back to the
+/// greedy single-line composer. With `continued`, the paragraph continues from the frame before,
+/// and its first composed line is not its first line.
+fn compose_para(
+    cx: &Ctx<'_>,
+    sg: &[SGlyph],
+    flex: &[Flex],
+    para: &ParaStyle,
+    pen: &Pen<'_>,
+    rtl: bool,
+    continued: bool,
+) -> Option<Vec<(usize, bool)>> {
+    let ragged = matches!(para.justify, Justify::Auto | Justify::Left | Justify::Center | Justify::Right);
+    let composer = cx.opts.composer.unwrap_or(para.composer);
+    // A paragraph whose commas or full stops may hang is composed line by line (as the Japanese
+    // single-line composer does).
+    let may_hang = para.burasagari != Burasagari::None && sg.iter().any(hangs);
+    // A tab's width depends on where it falls in its line, which the composer's fixed glyph widths
+    // can't follow: such a paragraph is broken line by line ([`break_line`] measures its tabs).
+    // The tab after a list marker always starts the first line and has a fixed width.
+    let has_tab = sg.iter().any(|g| g.ch == '\t' && g.len > 0);
+    if composer != Composer::EveryLine || pen.regions.is_none() || sg.len() < 2 || sg.len() > MAX_COMPOSE_GLYPHS || may_hang || has_tab {
+        return None;
+    }
+    let m = Metrics::of(&sg[0]);
+    // Line widths are independent of the breaks when every line has the same metrics, or when
+    // a line's width does not depend on how far down the frame it is set: rectangular cells
+    // without text wrap. Then a paragraph whose characters differ in line metrics (type size,
+    // font, leading, vertical scale, an inline graphic taller than the text) is composed too. In
+    // other shapes, or with text wrap, a taller line can move the lines below it to where the
+    // frame is narrower, so such a paragraph is broken line by line.
+    let plain = pen.regions.is_some_and(|r| r.iter().all(|r| (r.rect || r.polys.is_empty()) && r.wraps.is_empty()));
+    if !plain && sg.iter().any(|g| Metrics::of(g) != m) {
+        return None;
+    }
+    let total: f64 = sg.iter().map(|g| g.adv).sum();
+    let mut sim = pen.clone();
+    let mut widths = vec![];
+    let mut acc = 0.0;
+    // A line's width and placement depend on the sum of its indents alone, which the mirrored
+    // indents of a right-to-left list ([`line_indents`]) keep.
+    while widths.len() < sg.len() {
+        let first = widths.is_empty();
+        let ind_l = para.left_indent + if first && !continued { para.first_line_indent } else { 0.0 };
+        // Only the first line's first word is known here. Later lines are placed as the composed
+        // lines need: each fits its width, so its first word does too.
+        let word = if first { word_width(sg, 0) } else { 0.0 };
+        let Some((b, x0, x1, _)) = sim.place(m, ind_l, para.right_indent, word) else { break };
+        let w = x1 - x0 - ind_l - para.right_indent;
+        widths.push(w);
+        acc += w.max(1.0);
+        sim.settled(b, m);
+        sim.pending = 0.0;
+        if acc > total * 1.6 + 4.0 * w.max(1.0) {
+            break;
+        }
+    }
+    let last = *widths.last()?;
+    let width = |k: usize| widths.get(k).copied().unwrap_or(last);
+    // Lines from `uniform_from` on are interchangeable (same width).
+    let uniform_from = widths.iter().rposition(|&w| (w - last).abs() > EPS).map_or(0, |k| k + 1);
+    let cands = candidates(cx.text, sg, para.hyphenate.then_some(&para.hyphenation), para.kinsoku);
+    let justify_last = para.justify == Justify::JustifyAll;
+    let hyphen_limit = usize::try_from(para.hyphenation.hyphen_limit).unwrap_or(usize::MAX);
+    let params = |tolerance| Params { justify_last, ragged, tolerance, uniform_from, hyphen_limit };
+    // First look for breaks that keep every line within its range (ragged: at most one rag zone,
+    // a sixth of the width, left on each line; justified: the Justification options' Minimum and
+    // Maximum), then accept any lines that fit, the loosest scored worst. Justified text used to
+    // stop at four times its stretch and fall back to the single-line composer; the documented
+    // default range (word spacing up to 133%) is narrow enough that most paragraphs would.
+    let (strict, loose) = (1.0, f64::INFINITY);
+    // The same rule as the line loop below: an opening bracket starting a wrapped line gives up
+    // the space before it.
+    let start_credit = |i: usize| {
+        let flush = !rtl && para.mojikumi == Mojikumi::LineEndHalf;
+        sg.get(i).filter(|g| flush && g.lead <= 0.0).and_then(|g| punct_half(g, Punct::Opening)).unwrap_or(0.0)
+    };
+    compose(sg, &width, &start_credit, &cands, flex, &params(strict)).or_else(|| compose(sg, &width, &start_credit, &cands, flex, &params(loose)))
+}
+
+/// The list marker of each of the paragraphs `paras` of `t` (None for none): bullets, and numbers
+/// counted through consecutive list paragraphs from [`TextObject::list_count`], as
+/// [`vectorcraft_doc::text::ParaList::next_marker`] counts them.
+pub(super) fn list_markers(t: &TextObject, paras: &[Range<usize>]) -> Vec<Option<String>> {
+    let mut count = t.list_count;
+    paras.iter().enumerate().map(|(pi, pr)| vectorcraft_doc::text::ParaList::next_marker(t.para_at(pi).list, pr.is_empty(), &mut count)).collect()
+}
+
+/// Whether paragraph `para` (right to left when `rtl`) has its indents mirrored: a horizontal
+/// right-to-left list paragraph does.
+fn mirrors_indents(para: &ParaStyle, rtl: bool, vertical: bool) -> bool {
+    rtl && !vertical && para.list.is_some()
+}
+
+/// The indents at the left and at the right of a line of paragraph `para` (its first line when
+/// `first`). With `mirror` ([`mirrors_indents`]) the left and first-line indents are measured from
+/// the right and the right indent from the left: the bullet of a right-to-left list hangs at the
+/// right, and the lines it wraps to line up with the text after the bullet.
+fn line_indents(para: &ParaStyle, first: bool, mirror: bool) -> (f64, f64) {
+    let start = para.left_indent + if first { para.first_line_indent } else { 0.0 };
+    if mirror { (para.right_indent, start) } else { (start, para.right_indent) }
+}
+
+/// Flow paragraphs `paras` (byte ranges) of `t`, each with its own paragraph attributes
+/// (alignment, indents, spacing, direction, mojikumi, leading model…).
+pub(super) fn flow(cx: &mut Ctx<'_>, paras: &[Range<usize>], t: &TextObject, regions: Option<&[Region]>) {
+    let mut pen = Pen {
+        regions,
+        ri: 0,
+        prev: None,
+        pending: 0.0,
+        fb: cx.opts.first_baseline,
+        fb_min: cx.opts.first_baseline_min,
+        queued: vec![],
+        model: t.para_at(0).leading_model,
+        next_top: None,
+        no_room_for: f64::INFINITY,
+    };
+    let markers = list_markers(t, paras);
+    'paras: for (pi, pr) in paras.iter().enumerate() {
+        let para = t.para_at(pi);
+        let marker_text = markers.get(pi).and_then(Option::as_deref);
+        // The leading model is a paragraph attribute: this paragraph's lines (and the space to
+        // its first line) follow its own.
+        pen.model = para.leading_model;
+        let text = cx.text;
+        let bidi = para_bidi_with(text.get(pr.clone()).unwrap_or_default(), para.direction, &cx.char_directions(pr));
+        let rtl = is_rtl(bidi.as_ref());
+        let mut sg = cx.shape_para(pr.clone(), bidi.as_ref());
+        // Thai, Lao, Khmer and Myanmar break lines between words, not at spaces.
+        mark_word_ends(text.get(pr.clone()).unwrap_or_default(), pr.start, &mut sg);
+        // Japanese composition: consecutive punctuation shares one half-em space.
+        let mut compressed = if para.mojikumi == Mojikumi::LineEndHalf { compress_punctuation(&mut sg) } else { vec![] };
+        // …and a quarter em between Japanese and Latin text.
+        let mut wakan = if para.mojikumi == Mojikumi::LineEndHalf { space_japanese_and_latin(&mut sg) } else { vec![] };
+        // Justification…: the glyphs at Desired word and letter spacing and glyph scaling, and how
+        // far a justified line may move each one from it.
+        let mut flex = apply_desired(&mut sg, &para.justification, !cx.vertical);
+        // Threaded text: a first paragraph that continues from the frame before has its first
+        // line, first-line indent and list marker there.
+        let continued = pi == 0 && t.first_para_continues;
+        // Bullets and numbers: the list marker's glyphs `0..marker` start the paragraph.
+        // Justification and Optical Margin Alignment leave them as they are.
+        let marker = if continued { 0 } else { cx.prepend_marker(pr, para, marker_text, rtl, &mut sg) };
+        if marker > 0 {
+            flex.splice(0..0, vec![Flex::default(); marker]);
+            if !compressed.is_empty() {
+                compressed.splice(0..0, vec![false; marker]);
+            }
+            if !wakan.is_empty() {
+                wakan.splice(0..0, vec![0.0; marker]);
+            }
+        }
+        // …and Auto Leading: characters whose leading is Auto take this paragraph's share of their size.
+        let auto_leading = |st: &CharStyle| st.leading.unwrap_or_else(|| para.justification.auto_leading_for(st.size));
+        if para.justification.auto_leading != vectorcraft_doc::JustificationOptions::default().auto_leading {
+            for g in sg.iter_mut().filter(|g| g.inline.is_none()) {
+                g.leading = auto_leading(cx.style_at(g.byte));
+            }
+        }
+        let pm = {
+            let (asc, desc, _) = style_metrics(cx.db, cx.style_at(pr.start));
+            let lead = auto_leading(cx.style_at(pr.start));
+            let st = cx.style_at(pr.start);
+            let (cap, xh) = cap_x_heights(cx.db, st);
+            let centre = cx.db.style_face(st).map_or(EM_CENTER, |f| f.ideographic_centre());
+            Metrics { asc, desc, lead, cap, xh, top: (centre + 0.5) * st.size * st.v_scale / 100.0 }
+        };
+        if pi > 0 {
+            pen.pending += para.space_before;
+        }
+        let n = sg.len();
+        let composed = compose_para(cx, &sg, &flex, para, &pen, rtl, continued);
+        // Hyphenation options: the Hyphenation Zone applies with the Single-line Composer, and the
+        // Hyphen Limit counts the lines in a row that end with a hyphen.
+        let zone = if cx.opts.composer.unwrap_or(para.composer) == Composer::SingleLine { para.hyphenation.zone } else { 0.0 };
+        let hyphen_limit = usize::try_from(para.hyphenation.hyphen_limit).unwrap_or(usize::MAX);
+        let mut hyphen_run = 0;
+        let mut li_para = 0;
+        let mut i = 0;
+        let mirror = mirrors_indents(para, rtl, cx.vertical);
+        loop {
+            let est = if i < n { Metrics::of(&sg[i]) } else { pm };
+            let first_line = li_para == 0 && !continued;
+            let (ind_l, ind_r) = line_indents(para, first_line, mirror);
+            // Measured before Mojikumi narrows an opening bracket, as the composer measures it.
+            let word = word_width(&sg, i);
+            // Mojikumi: an opening bracket starting a line is set flush with the line's start (the
+            // space before it goes), and the line has that much more room. At a paragraph's start
+            // that is the first-line indent: JIS X 4051's principle (JLREQ 3.1.5, Figure 71 ①).
+            if !rtl
+                && para.mojikumi == Mojikumi::LineEndHalf
+                && let Some(g) = sg.get_mut(i)
+                && g.lead <= 0.0
+                && let Some(h) = punct_half(g, Punct::Opening)
+            {
+                g.adv -= h;
+                g.lead += h;
+            }
+            // Place, break, then settle the baseline on the line's real metrics (moving on to the
+            // next row/column if it no longer fits).
+            let (baseline, x0, x1, end, hyph, m) = loop {
+                let first_in_region = pen.prev.is_none();
+                let Some((mut baseline, x0, x1, same_baseline)) = pen.place(est, ind_l, ind_r, word) else {
+                    cx.out.overflow = cx.text.len() > if i < n { sg[i].byte } else { pr.start };
+                    break 'paras;
+                };
+                let width = x1 - x0 - ind_l - ind_r;
+                let hyphenate = (para.hyphenate && (hyphen_limit == 0 || hyphen_run < hyphen_limit)).then_some((&para.hyphenation, zone));
+                let (end, hyph) = match composed.as_ref().and_then(|c| c.get(li_para)) {
+                    Some(&(e, h)) if e > i => (e, h),
+                    _ if i < n => break_line(cx.text, &sg, i, width, &para.tabs, ind_l, hyphenate, para.burasagari, para.kinsoku),
+                    _ => (n, false),
+                };
+                let m = Metrics::max(&sg[i..end]).unwrap_or(pm);
+                baseline += if same_baseline || (pen.regions.is_none() && first_in_region) {
+                    0.0
+                } else if pen.model == LeadingModel::EmBoxTop {
+                    // The em box top is fixed (the frame's top, or the line above's): the baseline
+                    // hangs from it by this line's tallest em box.
+                    if first_in_region { m.top.max(pen.fb_min) - est.top.max(pen.fb_min) } else { m.top - est.top }
+                } else if first_in_region {
+                    m.first_baseline(pen.fb, pen.fb_min) - est.first_baseline(pen.fb, pen.fb_min)
+                } else {
+                    m.lead - est.lead
+                };
+                if pen.regions.is_some() && baseline + m.desc > pen.bottom() + 0.01 {
+                    // Try the next row/column; overflow if there is none.
+                    pen.ri += 1;
+                    pen.prev = None;
+                    pen.pending = 0.0;
+                    pen.queued.clear();
+                    continue;
+                }
+                break (baseline, x0, x1, end, hyph, m);
+            };
+            hyphen_run = if hyph && end > i { hyphen_run + 1 } else { 0 };
+            let (ax0, ax1) = if regions.is_some() { (x0 + ind_l, x1 - ind_r) } else { (x0, x1) };
+            let width = ax1 - ax0;
+            pen.pending = 0.0;
+            let last_of_para = end >= n;
+            let mut trimmed = end;
+            while trimmed > i && sg[trimmed - 1].is_space() {
+                trimmed -= 1;
+            }
+            let hyphen = (hyph && end > i).then(|| hyphen_glyph(&sg[end - 1]));
+            // Mojikumi: a closing bracket, comma or full stop ending the line is set half width, and
+            // no Japanese–Latin space is left at the end of a line.
+            let end_trim = match trimmed.checked_sub(1).filter(|&k| k >= i && para.mojikumi == Mojikumi::LineEndHalf) {
+                Some(k) => {
+                    let half = if compressed.get(k).copied().unwrap_or(false) { None } else { sg.get(k).and_then(|g| punct_half(g, Punct::Closing)) };
+                    half.unwrap_or(0.0) + wakan.get(k).copied().unwrap_or(0.0)
+                }
+                None => 0.0,
+            };
+            let w: f64 = set_width(&sg, i, trimmed, &para.tabs, ind_l) + hyphen.as_ref().map_or(0.0, |h| h.adv) - end_trim;
+            let line_start = sg.get(i).map_or(pr.start, |g| g.byte);
+            let line_end = sg.get(end).map_or(pr.end, |g| g.byte);
+            let order = visual_order(bidi.as_ref().filter(|_| !cx.vertical), pr.start, line_start..line_end, &sg[i..end]);
+            // Optical Margin Alignment or Roman Hanging Punctuation: the share of a glyph that hangs.
+            let share: Option<fn(&SGlyph) -> f64> =
+                (t.optical_margin || para.roman_hanging).then_some(if t.optical_margin { optical_share } else { roman_share });
+            // The glyphs before `stop` in visual order, each with the advance it is set with. A list
+            // marker does not hang: it is counted with no width.
+            let set = |j: usize, g: &SGlyph| {
+                if j < marker {
+                    0.0
+                } else if j + 1 == trimmed {
+                    g.adv - end_trim
+                } else {
+                    g.adv
+                }
+            };
+            let visible = |stop: usize| -> (Vec<usize>, Vec<(&SGlyph, f64)>) {
+                let at: Vec<usize> = order.iter().map(|&offset| i + offset).filter(|&j| j < stop).collect();
+                let glyphs = at.iter().filter_map(|&j| sg.get(j).map(|g| (g, set(j, g)))).collect();
+                (at, glyphs)
+            };
+            // Burasagari: a comma or full stop ending an area type line hangs outside it (Standard:
+            // when it doesn't fit, counting what hangs at the line's start as room; Forced:
+            // always). The rest of the line is aligned and justified without it, and it follows
+            // the line's last character.
+            let room_at_start = || share.map_or(0.0, |share| optical_hangs(&visible(trimmed).1, share).0);
+            let hang = (regions.is_some() && !rtl && hyphen.is_none() && trimmed > i + 1)
+                .then(|| sg.get(trimmed - 1))
+                .flatten()
+                .filter(|g| hangs(g))
+                .map(|g| g.adv - end_trim)
+                .filter(|_| match para.burasagari {
+                    Burasagari::None => false,
+                    Burasagari::Standard => w > width + room_at_start() + EPS,
+                    Burasagari::Forced => true,
+                });
+            let body = if hang.is_some() { trimmed - 1 } else { trimmed };
+            let w = w - hang.unwrap_or(0.0);
+            // The glyphs before the line's trailing spaces (and its burasagari mark), in the order
+            // they are drawn.
+            let (drawn, mut visible) = visible(body);
+            // Optical Margin Alignment: the glyphs at the ends of a line hang outside its margins
+            // by `opt_l` and `opt_r`. The line is aligned and justified in a measure that much
+            // wider at each end. A left-aligned line then hangs only at its left, a right-aligned
+            // line hangs only at its right, and centered and justified lines hang at both; Auto
+            // aligns a right-to-left line at its right. A right-to-left line is read from right to
+            // left ([`optical_hangs_rtl`]). A line that ends in a burasagari mark hangs only at its
+            // left. Justification adds no space after a punctuation mark hanging at the left, nor
+            // before one hanging at the right (`held`). A letter that hangs by part of its width
+            // keeps its gaps. Glyph Scaling leaves the glyphs that hang (`hung`) at their width, so
+            // they hang exactly by their published share. Roman Hanging Punctuation (a paragraph
+            // attribute) hangs the same punctuation by the same amounts, and no letters; with
+            // Optical Margin Alignment on as well, the letters hang too.
+            let (opt_l, opt_r, held, hung) = if let Some(share) = share {
+                if let Some(h) = &hyphen {
+                    visible.push((h, h.adv));
+                }
+                let (l, r, left_glyphs, right_glyphs) =
+                    if rtl && !cx.vertical { optical_hangs_rtl(&visible, share) } else { optical_hangs(&visible, share) };
+                let (r, right_glyphs) = if hang.is_some() { (0.0, 0) } else { (r, right_glyphs) };
+                let n_visible = visible.len();
+                let punct = |k: usize| visible.get(k).is_some_and(|&(g, _)| optical_punct(g));
+                let held: Vec<usize> = drawn
+                    .iter()
+                    .enumerate()
+                    .filter(|&(k, _)| (k < left_glyphs && punct(k)) || (right_glyphs > 0 && k + 1 + right_glyphs >= n_visible && punct(k + 1)))
+                    .map(|(_, &j)| j)
+                    .collect();
+                let hung: Vec<usize> = drawn
+                    .iter()
+                    .enumerate()
+                    .filter(|&(k, _)| k < left_glyphs || (right_glyphs > 0 && k + right_glyphs >= n_visible))
+                    .map(|(_, &j)| j)
+                    .collect();
+                (l, r, held, hung)
+            } else {
+                (0.0, 0.0, vec![], vec![])
+            };
+            // Justification adds nothing to the list marker's glyphs.
+            let mut held = held;
+            held.extend(i..marker.min(body));
+            // What justification may change of glyph `j`: nothing of a `held` glyph, and no glyph
+            // scaling of a `hung` one.
+            let line_flex = |j: usize| {
+                if held.contains(&j) {
+                    return Flex::default();
+                }
+                let mut f = flex.get(j).copied().unwrap_or_default();
+                if hung.contains(&j) {
+                    f.glyph = (0.0, 0.0);
+                }
+                f
+            };
+            let room = width + opt_l + opt_r;
+            let (align, justify) = match para.justify {
+                Justify::Auto => (if rtl { 2 } else { 0 }, false),
+                Justify::Left => (0, false),
+                Justify::Center => (1, false),
+                Justify::Right => (2, false),
+                Justify::JustifyLeft => (0, !last_of_para),
+                Justify::JustifyCenter => (1, !last_of_para),
+                Justify::JustifyRight => (2, !last_of_para),
+                Justify::JustifyAll => (0, true),
+            };
+            let justify = justify && regions.is_some();
+            let (mut per_space, mut per_gap, mut per_cjk) = (0.0, 0.0, 0.0);
+            let mut fit = LineFit::default();
+            let spaces = (i..body).filter(|&j| j >= marker && sg[j].is_space()).count();
+            // A gap that justification adds between two glyphs goes into the advance of the one
+            // drawn first: `drawn_after(j)` is the glyph drawn right after glyph `j`, which in a
+            // right-to-left line comes before it in the text.
+            let mut after: Vec<Option<usize>> = vec![None; body.saturating_sub(i)];
+            for (&a, &b) in drawn.iter().zip(drawn.iter().skip(1)) {
+                if let Some(slot) = after.get_mut(a - i) {
+                    *slot = Some(b);
+                }
+            }
+            let drawn_after = |j: usize| j.checked_sub(i).and_then(|k| after.get(k).copied().flatten());
+            // Japanese (and Chinese) lines are justified between their characters (JLREQ 3.8): the
+            // gaps next to a CJK character, not inside a Latin word or a tate-chu-yoko block.
+            let cjk_gap = |j: usize| {
+                !held.contains(&j)
+                    && drawn_after(j)
+                        .and_then(|k| sg.get(j).zip(sg.get(k)))
+                        .is_some_and(|(a, b)| !a.is_space() && !b.is_space() && !b.continues_tcy() && a.ch != '\t' && (is_cjk(a.ch) || is_cjk(b.ch)))
+            };
+            let cjk_gaps = (i..body).filter(|&j| cjk_gap(j)).count();
+            // Single Word Justification: a justified line holding one word (no word space) is
+            // spread between its letters (Full Justify) or aligned.
+            let single_word = justify && spaces == 0 && cjk_gaps == 0;
+            let (align, justify) = match (single_word, para.justification.single_word) {
+                (false, _) | (true, SingleWordJustify::FullJustify) => (align, justify),
+                (true, SingleWordJustify::AlignLeft) => (0, false),
+                (true, SingleWordJustify::AlignCenter) => (1, false),
+                (true, SingleWordJustify::AlignRight) => (2, false),
+            };
+            // Insert Kashidas: the Arabic words of a horizontal line take its room on kashidas,
+            // and the word spaces and gaps take what is left.
+            let kashidas =
+                if justify && !cx.vertical && room > w + EPS { kashida::plan(cx.text, &sg, i..body, para.kashida, room - w) } else { vec![] };
+            let w = w + kashidas.iter().map(|k| k.1).sum::<f64>();
+            if justify && (room - w).abs() > EPS {
+                if cjk_gaps > 0 && room > w {
+                    // Spread over the CJK gaps and the word spaces alike.
+                    let per = (room - w) / (cjk_gaps + spaces) as f64;
+                    (per_space, per_cjk) = (per, per);
+                } else if spaces > 0 {
+                    // Word spacing, letter spacing and glyph scaling within their ranges, then the
+                    // word spaces alone; composed lines may shrink word spaces (never below zero).
+                    let line: Vec<Flex> = (i..body).map(line_flex).collect();
+                    let floor = (i..body).filter(|&j| j >= marker && sg[j].is_space()).map(|j| sg[j].adv).fold(f64::MAX, f64::min);
+                    fit = fit_line(&line, room - w, spaces, floor);
+                } else if room > w {
+                    // One word: its letter spacing and glyph scaling, then the gaps between its glyphs.
+                    let line: Vec<Flex> = (i..body).map(line_flex).collect();
+                    fit = fit_line(&line, room - w, 0, 0.0);
+                    let used: f64 = line.iter().map(|f| fit.letter(f) + fit.glyph(f)).sum();
+                    let rest = room - w - used;
+                    let gaps = (i..body)
+                        .filter(|&j| !held.contains(&j) && drawn_after(j).and_then(|k| sg.get(k)).is_some_and(|next| !next.continues_tcy()))
+                        .count();
+                    if gaps > 0 && rest > EPS {
+                        per_gap = rest / gaps as f64;
+                    }
+                }
+            }
+            let start_x = if justify {
+                ax0 - opt_l
+            } else if regions.is_none() {
+                match align {
+                    0 => ind_l - opt_l,
+                    1 => (ind_l - opt_l - ind_r + opt_r - w) * 0.5,
+                    _ => -ind_r + opt_r - w,
+                }
+            } else {
+                match align {
+                    0 => ax0 - opt_l,
+                    1 => ax0 - opt_l + (room - w) * 0.5,
+                    _ => ax1 + opt_r - w,
+                }
+            };
+            let li = cx.out.lines.len();
+            let glyph_start = cx.out.glyphs.len();
+            // Character Alignment lines smaller characters up with the line's largest em box.
+            let line_em = sg.get(i..end).map_or(0.0, |line| line.iter().map(glyph_em).fold(0.0, f64::max));
+            let mut x_end = start_x;
+            // Tab stops are measured from the frame's left edge (point type: the origin).
+            let tab_origin = if regions.is_some() { x0 } else { 0.0 };
+            // A line with tabs is measured as if it started at the left (see `set_width`), then
+            // aligned as a whole: its tabs stop where they were measured, however it is aligned.
+            let tab_shift = start_x - if regions.is_some() { ax0 } else { ind_l };
+            // RTL's logical trailing spaces precede the visible content. Keep them outside
+            // the aligned content extent, just as LTR trailing spaces extend to its right.
+            let leading_space_width: f64 =
+                order.iter().take_while(|&&offset| i + offset >= trimmed).filter_map(|&offset| sg.get(i + offset)).map(|g| g.adv).sum();
+            let mut x = start_x - leading_space_width;
+            // The glyphs drawn for the list marker, and the index of its tab's glyph, when the line starts the paragraph.
+            let mut marker_glyphs: Option<Range<usize>> = None;
+            let mut marker_tab = 0;
+            for (oi, &offset) in order.iter().enumerate() {
+                let j = i + offset;
+                let Some(g) = sg.get(j) else { continue };
+                let mut adv = g.adv;
+                if j + 1 == trimmed {
+                    adv -= end_trim;
+                }
+                // Glyph scaling a justified line adds to the glyph (1: none).
+                let mut scale = 1.0;
+                let mut leader = "";
+                if g.ch == '\t' {
+                    // The tab after a list marker keeps the width `prepend_marker` gave it.
+                    if g.len > 0 {
+                        (adv, leader) = tab_advance(&para.tabs, tab_origin, x - tab_shift, &sg[j + 1..trimmed.max(j + 1)]);
+                    }
+                } else if j < body {
+                    let f = line_flex(j);
+                    if is_word_space(g) {
+                        adv += fit.space(&f);
+                    } else {
+                        adv += fit.letter(&f) + fit.glyph(&f);
+                        scale = fit.glyph_scale(&f);
+                    }
+                    if g.is_space() {
+                        adv += per_space;
+                    } else if per_cjk != 0.0 {
+                        if cjk_gap(j) {
+                            adv += per_cjk;
+                        }
+                    } else if !held.contains(&j) && drawn_after(j).and_then(|k| sg.get(k)).is_some_and(|next| !next.continues_tcy()) {
+                        // Between glyphs, never inside a tate-chu-yoko block (one cell).
+                        adv += per_gap;
+                    }
+                }
+                // The kashida before a cluster in the text is drawn at the cluster's right, between
+                // it and the letter before it, and the cluster's last glyph advances over it: the
+                // caret, selection and hit testing take it as part of the cluster.
+                let kashida = kashidas
+                    .binary_search_by_key(&g.byte, |k| k.0)
+                    .ok()
+                    .and_then(|at| kashidas.get(at))
+                    .filter(|_| order.get(oi + 1).and_then(|&o| sg.get(i + o)).is_none_or(|next| next.byte != g.byte))
+                    .map(|k| k.1);
+                adv += kashida.unwrap_or(0.0);
+                let y = baseline - align_shift(g, cx.style_at(g.byte).char_align, line_em, cx.vertical);
+                let place = if scale != 1.0 { Affine::translate((x, y)) * Affine::scale_non_uniform(scale, 1.0) } else { Affine::translate((x, y)) };
+                if j < marker {
+                    let at = cx.out.glyphs.len();
+                    marker_glyphs = Some(marker_glyphs.map_or(at..at + 1, |r: Range<usize>| r.start.min(at)..r.end.max(at + 1)));
+                    if j + 1 == marker {
+                        marker_tab = at;
+                    }
+                }
+                cx.emit(g, place, Point::new(x, y), 0.0, adv, li);
+                if let Some(out) = cx.out.glyphs.last_mut() {
+                    out.scale = flex.get(j).map_or(1.0, |f| f.scale) * scale;
+                }
+                if !leader.is_empty() {
+                    // The leader belongs to the tab's glyph: the gap stays one character for the
+                    // caret, selection and hit testing.
+                    let dots = leader_outline(cx.db, g, leader, tab_origin, x, x + adv, y);
+                    if let Some(tab) = cx.out.glyphs.last_mut() {
+                        tab.outline.extend(dots);
+                    }
+                }
+                if let Some(len) = kashida {
+                    cx.emit_kashida(g, para.kashida, len, Point::new(x + adv - len, y), li);
+                }
+                x += adv;
+                if j < trimmed {
+                    x_end = x;
+                }
+            }
+            if let (Some(glyphs), Some(text)) = (marker_glyphs, marker_text) {
+                cx.out.markers.push(ListMarker { glyphs, tab: marker_tab, text: text.to_string() });
+            }
+            if let Some(h) = &hyphen {
+                // The hyphen follows the last non-space glyph.
+                let hx = x_end;
+                cx.emit(h, Affine::translate((hx, baseline)), Point::new(hx, baseline), 0.0, h.adv, li);
+                x_end = hx + h.adv;
+            }
+            cx.out.lines.push(LineInfo {
+                rtl: rtl && !cx.vertical,
+                baseline,
+                x0: start_x,
+                x1: x_end,
+                ascent: m.asc,
+                descent: m.desc,
+                first_baseline: if pen.model == LeadingModel::EmBoxTop { m.top.max(pen.fb_min) } else { m.first_baseline(pen.fb, pen.fb_min) },
+                start: if i < n { sg[i].byte } else { pr.start },
+                end: if last_of_para { pr.end } else { sg[end].byte },
+                glyph_start,
+                glyph_end: cx.out.glyphs.len(),
+                avail: if regions.is_some() { (ax0, ax1) } else { (start_x, x_end) },
+                region: if regions.is_some() { pen.ri } else { 0 },
+            });
+            pen.settled(baseline, m);
+            // Further spans of this line band share the settled baseline.
+            for q in &mut pen.queued {
+                q.0 = baseline;
+            }
+            li_para += 1;
+            i = end;
+            if i >= n {
+                break;
+            }
+        }
+        pen.pending += para.space_after;
+    }
+}

crates/text/src/layout/on_path.rs

@@ -0,0 +1,408 @@
+use super::bidi::{is_rtl, para_bidi_with, visual_order};
+use super::breaking::{Metrics, optical_hangs, optical_hangs_rtl, optical_share, roman_share};
+use super::flow::list_markers;
+use super::region::in_range;
+use super::*;
+
+/// The distance along type on a path each glyph takes: its advance measured `spacing` points above
+/// the path (Type on a Path Options › Spacing), so glyphs close up round the outside of a curve and
+/// open up round the inside; just the advances without spacing. Glyphs start `from` along the path.
+fn path_steps(ap: &ArcPath, glyphs: &[SGlyph], from: f64, spacing: f64) -> Vec<f64> {
+    let mut s = from;
+    glyphs
+        .iter()
+        .map(|g| {
+            let mut step = g.adv;
+            if spacing != 0.0 && g.adv > 1e-9 {
+                // How far the path turns across the glyph: positive bending away from its top.
+                let ((_, a), (_, b)) = (ap.at(s), ap.at(s + g.adv));
+                let curvature = a.cross(b).atan2(a.dot(b)) / g.adv;
+                step = g.adv / (1.0 + curvature * spacing).clamp(0.25, 4.0);
+            }
+            s += step;
+            step
+        })
+        .collect()
+}
+
+/// How closely a bent glyph's curves follow the path (text space units).
+const BEND_TOLERANCE: f64 = 0.01;
+
+/// The most pieces one segment of a glyph's outline is cut into to bend it.
+const BEND_PIECES: usize = 32;
+
+/// The most elements a bent glyph outline may have; beyond that the glyph stays straight.
+const BEND_MAX_ELEMENTS: usize = 8192;
+
+/// `outline` (text space, placed straight by `pre`, which takes the glyph's pen space there) bent
+/// along `ap` as `bend` says ([`GlyphBend`]); `None` where the path doesn't turn under the glyph
+/// (it stays as it is, exactly), or the bent outline would be too large or not finite.
+fn bend_outline(outline: &BezPath, pre: Affine, ap: &ArcPath, bend: &GlyphBend) -> Option<BezPath> {
+    let GlyphBend { s, step, advance, rise } = *bend;
+    if outline.elements().is_empty() || !(advance > 1e-9 && step.is_finite() && step > 0.0 && s.is_finite() && rise.is_finite()) {
+        return None;
+    }
+    // How far the path turns under the glyph; none: it lies straight already.
+    let ((_, a), (_, b)) = (ap.at(s), ap.at(s + step));
+    let turn = a.cross(b).atan2(a.dot(b)).abs();
+    if !(turn.is_finite() && turn > 1e-9) {
+        return None;
+    }
+    let det = pre.determinant();
+    if !(det.is_finite() && det.abs() > 1e-12) {
+        return None;
+    }
+    let to_pen = pre.inverse();
+    let k = step / advance;
+    let map = |q: Point| {
+        let (p, d) = ap.at(s + q.x * k);
+        p + Vec2::new(-d.y, d.x) * (q.y + rise)
+    };
+    // Pieces short enough that mapping a piece's control points stays within the tolerance: the
+    // error of a piece of length L under curvature c, at height y, is about L² c (1 + |y| c) / 8.
+    let curvature = turn / step;
+    let pen = to_pen * outline.clone();
+    let height = pen.bounding_box().y0.abs().max(pen.bounding_box().y1.abs()) + rise.abs();
+    let piece = ((8.0 * BEND_TOLERANCE) / (curvature * (1.0 + height * curvature))).sqrt();
+    let pieces = |a: Point, b: Point| -> usize {
+        let n = ((b - a).hypot() / piece).ceil();
+        if n.is_finite() { (n as usize).clamp(1, BEND_PIECES) } else { BEND_PIECES }
+    };
+    let mut out = BezPath::new();
+    let (mut start, mut cur) = (Point::ZERO, Point::ZERO);
+    let line = |out: &mut BezPath, from: Point, to: Point| {
+        let n = pieces(from, to);
+        for i in 1..=n {
+            out.line_to(map(from.lerp(to, i as f64 / n as f64)));
+        }
+    };
+    for el in pen.elements() {
+        match *el {
+            PathEl::MoveTo(p) => {
+                out.move_to(map(p));
+                (start, cur) = (p, p);
+            }
+            PathEl::LineTo(p) => {
+                line(&mut out, cur, p);
+                cur = p;
+            }
+            PathEl::QuadTo(p1, p2) => {
+                let c = kurbo::QuadBez::new(cur, p1, p2).raise();
+                let n = pieces(cur, p1).max(pieces(p1, p2));
+                for i in 0..n {
+                    let q = c.subsegment(i as f64 / n as f64..(i + 1) as f64 / n as f64);
+                    out.curve_to(map(q.p1), map(q.p2), map(q.p3));
+                }
+                cur = p2;
+            }
+            PathEl::CurveTo(p1, p2, p3) => {
+                let c = kurbo::CubicBez::new(cur, p1, p2, p3);
+                let n = pieces(cur, p1).max(pieces(p1, p2)).max(pieces(p2, p3));
+                for i in 0..n {
+                    let q = c.subsegment(i as f64 / n as f64..(i + 1) as f64 / n as f64);
+                    out.curve_to(map(q.p1), map(q.p2), map(q.p3));
+                }
+                cur = p3;
+            }
+            PathEl::ClosePath => {
+                if (cur - start).hypot() > 1e-12 {
+                    line(&mut out, cur, start);
+                }
+                out.close_path();
+                cur = start;
+            }
+        }
+        if out.elements().len() > BEND_MAX_ELEMENTS {
+            return None;
+        }
+    }
+    let finite = |p: Point| p.x.is_finite() && p.y.is_finite();
+    out.elements()
+        .iter()
+        .all(|el| match *el {
+            PathEl::MoveTo(p) | PathEl::LineTo(p) => finite(p),
+            PathEl::QuadTo(a, b) => finite(a) && finite(b),
+            PathEl::CurveTo(a, b, c) => finite(a) && finite(b) && finite(c),
+            PathEl::ClosePath => true,
+        })
+        .then_some(out)
+}
+
+/// Lay type on a path out along `path` (text space), between its brackets.
+pub(super) fn on_path(cx: &mut Ctx<'_>, paras: &[Range<usize>], t: &TextObject, path: &PathData) {
+    cx.out.on_path = true;
+    // Type on a path is one line: the first paragraph's attributes align it.
+    let para = t.para_at(0);
+    // The first paragraph's direction aligns the line (Auto) and sets the caret's.
+    let mut rtl = None;
+    let mut shaped = Vec::new();
+    let markers = list_markers(t, paras);
+    for (pi, pr) in paras.iter().enumerate() {
+        let text = cx.text;
+        let bidi = para_bidi_with(text.get(pr.clone()).unwrap_or_default(), para.direction, &cx.char_directions(pr));
+        rtl.get_or_insert(is_rtl(bidi.as_ref()) && !cx.vertical);
+        let mut glyphs = cx.shape_para(pr.clone(), bidi.as_ref());
+        // Bullets and numbers: a list paragraph's text starts after its marker here too, unless
+        // the paragraph continues from the frame before in its thread.
+        if pi > 0 || !t.first_para_continues {
+            let marker_text = markers.get(pi).and_then(Option::as_deref);
+            cx.prepend_marker(pr, t.para_at(pi), marker_text, is_rtl(bidi.as_ref()) && !cx.vertical, &mut glyphs);
+        }
+        shaped.push((pr.clone(), bidi.filter(|b| b.has_rtl() && !cx.vertical), glyphs));
+    }
+    let rtl = rtl.unwrap_or(false);
+    // The text before byte `cut` in visual order, as area type reorders each line it breaks.
+    let visual = |cut: usize| {
+        let mut sg = Vec::new();
+        for (pr, bidi, glyphs) in &shaped {
+            let n = glyphs.iter().take_while(|g| g.byte < cut).count();
+            let line = glyphs.get(..n).unwrap_or_default();
+            let end = glyphs.get(n).map_or(pr.end, |g| g.byte);
+            sg.extend(visual_order(bidi.as_ref(), pr.start, pr.start..end, line).into_iter().filter_map(|i| line.get(i).cloned()));
+        }
+        sg
+    };
+    let text_len = cx.text.len();
+    let mut sg = visual(text_len);
+    // A path out of range holds no text, as a path with no length holds none.
+    let ap = if in_range(&path.to_bezpath()) { ArcPath::new(path) } else { ArcPath::default() };
+    let m = Metrics::max(&sg).map(|m| (m.asc, m.desc)).unwrap_or_else(|| {
+        let s = style_metrics(cx.db, cx.style_at(0));
+        (s.0, s.1)
+    });
+    if ap.is_empty() {
+        cx.out.overflow = !sg.is_empty();
+        cx.out.lines.push(LineInfo {
+            rtl,
+            baseline: 0.0,
+            x0: 0.0,
+            x1: 0.0,
+            ascent: m.0,
+            descent: m.1,
+            first_baseline: 0.0,
+            start: 0,
+            end: 0,
+            glyph_start: 0,
+            glyph_end: 0,
+            avail: (0.0, 0.0),
+            region: 0,
+        });
+        return;
+    }
+    let centre = path.bounds().unwrap_or_default().center();
+    let (from, to) = t.kind.path_span().unwrap_or((0.0, 1.0));
+    let s_start = from * ap.len();
+    let avail = (to - from) * ap.len();
+    let spacing = if t.path_spacing.is_finite() { t.path_spacing } else { 0.0 };
+    // Optical Margin Alignment and Roman Hanging Punctuation: the brackets are the margins, and the
+    // glyphs at the line's ends hang outside them by `hang_l` and `hang_r`, measured along the path.
+    // The line is aligned in a span that much longer at each end, and the glyphs that hang at the
+    // end (`hung_r` of them) do not make it overflow past the end bracket. On an open path a hang
+    // stops at the path's end. On a closed path the two hangs together take at most the stretch
+    // between the end and start brackets: the end where the line is placed takes its share first.
+    // A centered line's ends each get up to half of it, and either end takes what the other leaves.
+    // The hangs are measured on the steps the glyphs take where the line is placed. A right-to-left
+    // line is read from right to left ([`optical_hangs_rtl`]); in vertical type `sg` is in text order.
+    let hanging = t.optical_margin || para.roman_hanging;
+    let hangs = |sg: &[SGlyph], steps: &[f64]| {
+        if !hanging {
+            return (0.0, 0.0, 0);
+        }
+        let share: fn(&SGlyph) -> f64 = if t.optical_margin { optical_share } else { roman_share };
+        // A list marker (the glyphs of length 0) does not hang: it is counted with no width.
+        let line: Vec<(&SGlyph, f64)> = sg.iter().zip(steps).map(|(g, &step)| (g, if g.len == 0 { 0.0 } else { step })).collect();
+        let (l, r, _, hung_r) = if rtl { optical_hangs_rtl(&line, share) } else { optical_hangs(&line, share) };
+        let (l, r) = if ap.is_closed() {
+            let gap = (ap.len() - avail).max(0.0);
+            match para.justify {
+                j if matches!(j, Justify::Right | Justify::JustifyRight) || (rtl && j == Justify::Auto) => {
+                    let r = r.min(gap);
+                    (l.min(gap - r), r)
+                }
+                Justify::Center | Justify::JustifyCenter => {
+                    let l = l.min(gap - r.min(gap * 0.5));
+                    (l, r.min(gap - l))
+                }
+                _ => {
+                    let l = l.min(gap);
+                    (l, r.min(gap - l))
+                }
+            }
+        } else {
+            (l.min(s_start), r.min((ap.len() - s_start - avail).max(0.0)))
+        };
+        (l, r, hung_r)
+    };
+    // The glyphs `sg` arranged on the path: their steps, where the first starts, and the hangs.
+    let arrange = |sg: &[SGlyph]| {
+        let mut steps = path_steps(&ap, sg, s_start, spacing);
+        let w: f64 = steps.iter().sum();
+        let place = |(l, r, _): (f64, f64, usize)| {
+            let (lo, room) = (s_start - l, avail + l + r);
+            match para.justify {
+                Justify::Auto if rtl => lo + (room - w).max(0.0),
+                Justify::Center | Justify::JustifyCenter => lo + ((room - w) * 0.5).max(0.0),
+                Justify::Right | Justify::JustifyRight => lo + (room - w).max(0.0),
+                _ => lo,
+            }
+        };
+        let mut hung = hangs(sg, &steps);
+        let mut s0 = place(hung);
+        if spacing != 0.0 && s0 != s_start {
+            // Spaced from where the alignment puts them, the curve under them is another. That
+            // changes the hanging glyphs' steps, so the line is placed again from the new steps
+            // until it stays where it is (at most 8 times).
+            steps = path_steps(&ap, sg, s0, spacing);
+            for _ in 0..8 {
+                hung = hangs(sg, &steps);
+                let moved = place(hung);
+                if (moved - s0).abs() < 1e-9 {
+                    break;
+                }
+                s0 = moved;
+                steps = path_steps(&ap, sg, s0, spacing);
+            }
+        }
+        (steps, s0, hung)
+    };
+    // How many of the arranged glyphs fit before one runs past the end bracket (with the hang).
+    let fitting = |steps: &[f64], s0: f64, (hang_l, hang_r, hung_r): (f64, f64, usize)| {
+        let (lo, room) = (s_start - hang_l, avail + hang_l + hang_r);
+        let mut x = 0.0;
+        steps
+            .iter()
+            .enumerate()
+            .take_while(|&(k, &step)| {
+                let end = if k + hung_r >= steps.len() { room } else { room - hang_r };
+                let fit = s0 + x + step - lo <= end + 1e-6;
+                x += step;
+                fit
+            })
+            .count()
+    };
+    let (mut steps, mut s0, mut hung) = arrange(&sg);
+    // Where the text that fits ends: before the first glyph that doesn't, which threaded text
+    // flows on from, as from the last line of area type.
+    let mut fits = text_len;
+    // Right-to-left text that overflows keeps the start of its text, not what comes first in visual
+    // order: the longest start, in reading order, whose glyphs fit in visual order is laid out.
+    if shaped.iter().any(|(_, bidi, _)| bidi.is_some()) && fitting(&steps, s0, hung) < sg.len() {
+        let mut starts: Vec<usize> = shaped.iter().flat_map(|(_, _, glyphs)| glyphs.iter().map(|g| g.byte)).collect();
+        starts.dedup();
+        // The text before `starts[fit]` fits; before `starts[over]` (the whole text at the end) it
+        // doesn't.
+        let (mut fit, mut over) = (0, starts.len());
+        while over - fit > 1 {
+            let mid = (fit + over) / 2;
+            let sg = visual(starts.get(mid).copied().unwrap_or(text_len));
+            let (steps, s0, hung) = arrange(&sg);
+            if fitting(&steps, s0, hung) == sg.len() {
+                fit = mid;
+            } else {
+                over = mid;
+            }
+        }
+        cx.out.overflow = true;
+        fits = starts.get(fit).copied().unwrap_or(text_len);
+        sg = visual(fits);
+        (steps, s0, hung) = arrange(&sg);
+    }
+    let fit = fitting(&steps, s0, hung);
+    if fit < sg.len() {
+        cx.out.overflow = true;
+        fits = sg.get(fit..).and_then(|rest| rest.iter().map(|g| g.byte).min()).unwrap_or(text_len);
+    }
+    // Align to Path: how far down (glyph space) the type moves to run its ascender, centre or
+    // descender along the path instead of its baseline.
+    let rise = match t.path_align {
+        PathAlign::Baseline => 0.0,
+        PathAlign::Ascender => m.0,
+        PathAlign::Descender => -m.1,
+        PathAlign::Center => (m.0 - m.1) * 0.5,
+    };
+    let mut x = 0.0;
+    for (g, &step) in sg.iter().zip(&steps).take(fit) {
+        let s = s0 + x;
+        let (p, dir) = ap.at(s + step * 0.5);
+        let angle = dir.y.atan2(dir.x);
+        let half = Affine::translate((-g.adv * 0.5, rise));
+        // Glyph space: x along the advance, y down from the baseline; `pre` maps it onto the path.
+        let pre = match t.path_effect {
+            PathEffect::Rainbow => Affine::translate(p.to_vec2()) * Affine::rotate(angle) * half,
+            // x axis along the tangent, y axis stays vertical.
+            PathEffect::Skew => Affine::translate(p.to_vec2()) * Affine::new([dir.x, dir.y, 0.0, 1.0, 0.0, 0.0]) * half,
+            // x axis stays horizontal (facing the path's direction), y axis perpendicular to the path.
+            PathEffect::Ribbon3d => {
+                let sx = if dir.x < 0.0 { -1.0 } else { 1.0 };
+                Affine::translate(p.to_vec2()) * Affine::new([sx, 0.0, -dir.y * sx, dir.x * sx, 0.0, 0.0]) * half
+            }
+            PathEffect::StairStep => Affine::translate(ap.at(s).0.to_vec2()) * Affine::translate((0.0, rise)),
+            // x axis along the tangent; vertical edges point at the path's centre (kept on the glyph's
+            // up side, and never closer than ~17° to the baseline so glyphs stay legible).
+            PathEffect::Gravity => {
+                let n = Vec2::new(dir.y, -dir.x);
+                let mut up = p - centre;
+                up = if up.hypot() < 1e-9 { n } else { up / up.hypot() };
+                if up.dot(n) < 0.0 {
+                    up = -up;
+                }
+                if up.dot(n) < 0.3 {
+                    let along = up - n * up.dot(n);
+                    up = n * 0.3 + along / along.hypot().max(1e-9) * (1.0 - 0.09f64).sqrt();
+                }
+                Affine::translate(p.to_vec2()) * Affine::new([dir.x, dir.y, -up.x, -up.y, 0.0, 0.0]) * half
+            }
+        };
+        // The caret's baseline moves with the type.
+        let origin = p - dir * (g.adv * 0.5) + Vec2::new(-dir.y, dir.x) * rise;
+        // A list marker's glyphs (the only glyphs here with no length) are in a row at the byte of
+        // their paragraph's start.
+        if g.len == 0 {
+            let at = cx.out.glyphs.len();
+            let starts_paragraph = |b: usize| paras.iter().position(|p| p.start == b);
+            match cx.out.markers.last_mut() {
+                Some(m) if m.glyphs.end == at && cx.out.glyphs.get(m.glyphs.start).is_some_and(|h| h.byte == g.byte) => m.glyphs.end = at + 1,
+                _ => {
+                    if let Some(text) = starts_paragraph(g.byte).and_then(|pi| markers.get(pi)).and_then(Option::as_ref) {
+                        cx.out.markers.push(ListMarker { glyphs: at..at + 1, tab: at, text: text.clone() });
+                    }
+                }
+            }
+            if let Some(m) = cx.out.markers.last_mut().filter(|m| m.glyphs.end == at + 1 && g.ch == '\t') {
+                m.tab = at;
+            }
+        }
+        cx.emit(g, pre, origin, angle, g.adv, 0);
+        // A glyph of a script whose letters join is bent along a curved path (Rainbow), so its
+        // joining strokes meet its neighbours' instead of standing off the curve.
+        if t.path_effect == PathEffect::Rainbow && g.cursive && !cx.vertical && g.inline.is_none() {
+            let bend = GlyphBend { s, step, advance: g.adv, rise };
+            if let Some(last) = cx.out.glyphs.last_mut()
+                && last.image.is_none()
+                && last.colour.is_none()
+                && let Some(bent) = bend_outline(&last.outline, pre, &ap, &bend)
+            {
+                last.outline = bent;
+                last.bend = Some(bend);
+            }
+        }
+        x += step;
+    }
+    let (ps, _) = ap.at(s0);
+    let (pe, _) = ap.at(s0 + x);
+    cx.out.lines.push(LineInfo {
+        rtl,
+        baseline: ps.y,
+        x0: ps.x,
+        x1: pe.x,
+        ascent: m.0,
+        descent: m.1,
+        first_baseline: 0.0,
+        start: 0,
+        end: fits,
+        glyph_start: 0,
+        glyph_end: cx.out.glyphs.len(),
+        avail: (0.0, ap.len()),
+        region: 0,
+    });
+}

crates/text/src/layout/region.rs

@@ -0,0 +1,233 @@
+use super::*;
+
+/// A flattened text wrap shape: (polygons, offset, invert).
+pub(super) type FlatWrap = (Vec<Vec<Point>>, f64, bool);
+
+/// One cell of a flattened area-type frame (the whole frame, or one row/column of it).
+pub(super) struct Region {
+    /// The cell (frame bounds, or a grid cell of them).
+    pub(super) cell: Rect,
+    /// Inset applied inside the frame edges.
+    inset: f64,
+    pub(super) polys: std::sync::Arc<[Vec<Point>]>,
+    /// The frame is its own bounding rectangle (spans need no polygon intersection).
+    pub(super) rect: bool,
+    /// Text Wrap shapes.
+    pub(super) wraps: std::sync::Arc<[FlatWrap]>,
+    /// Vertical alignment: how far below the top-aligned position the first line starts.
+    pub(super) shift: f64,
+    /// Vertical justification: extra space added between consecutive lines.
+    pub(super) gap: f64,
+}
+
+/// The largest magnitude a coordinate of a frame, a text wrap shape or the path of type on a path
+/// may have (points), control points included. A frame or path with a larger coordinate, or a
+/// coordinate that isn't finite, holds no text, and a text wrap shape with one is ignored.
+const MAX_COORD: f64 = 1e9;
+
+/// Are the coordinates of `path`, control points included, finite and within [`MAX_COORD`]?
+pub(super) fn in_range(path: &BezPath) -> bool {
+    let near = |p: &Point| p.x.abs() <= MAX_COORD && p.y.abs() <= MAX_COORD;
+    path.elements().iter().all(|el| match el {
+        PathEl::MoveTo(p) | PathEl::LineTo(p) => near(p),
+        PathEl::QuadTo(a, p) => near(a) && near(p),
+        PathEl::CurveTo(a, b, p) => near(a) && near(b) && near(p),
+        PathEl::ClosePath => true,
+    })
+}
+
+/// Flattened closed polygons of a path; `None` when it isn't [`in_range`].
+fn polygons(path: &BezPath) -> Option<Vec<Vec<Point>>> {
+    if !in_range(path) {
+        return None;
+    }
+    let mut polys: Vec<Vec<Point>> = Vec::new();
+    kurbo::flatten(path, 0.1, |el| match el {
+        PathEl::MoveTo(p) => polys.push(vec![p]),
+        PathEl::LineTo(p) => {
+            if let Some(v) = polys.last_mut() {
+                v.push(p);
+            }
+        }
+        _ => {}
+    });
+    polys.retain(|p| p.len() >= 3);
+    Some(polys)
+}
+
+/// Inside intervals (even-odd) of the horizontal line at `y` through `polys`.
+fn poly_intervals(polys: &[Vec<Point>], y: f64) -> Vec<(f64, f64)> {
+    let mut xs = Vec::new();
+    for poly in polys {
+        for i in 0..poly.len() {
+            let a = poly[i];
+            let b = poly[(i + 1) % poly.len()];
+            if (a.y <= y) != (b.y <= y) {
+                xs.push(a.x + (y - a.y) / (b.y - a.y) * (b.x - a.x));
+            }
+        }
+    }
+    xs.sort_by(f64::total_cmp);
+    xs.as_chunks::<2>().0.iter().map(|c| (c[0], c[1])).collect()
+}
+
+/// Union of sorted-or-not intervals.
+fn union_intervals(mut v: Vec<(f64, f64)>) -> Vec<(f64, f64)> {
+    v.sort_by(|a, b| a.0.total_cmp(&b.0));
+    let mut out: Vec<(f64, f64)> = Vec::with_capacity(v.len());
+    for (a, b) in v {
+        match out.last_mut() {
+            Some(l) if a <= l.1 => l.1 = l.1.max(b),
+            _ => out.push((a, b)),
+        }
+    }
+    out
+}
+
+/// `a` minus `b` (both unions of disjoint intervals).
+fn subtract_intervals(a: &[(f64, f64)], b: &[(f64, f64)]) -> Vec<(f64, f64)> {
+    let mut out = vec![];
+    for &(mut s, e) in a {
+        for &(c, d) in b {
+            if d <= s || c >= e {
+                continue;
+            }
+            if c > s {
+                out.push((s, c));
+            }
+            s = s.max(d);
+        }
+        if e > s {
+            out.push((s, e));
+        }
+    }
+    out
+}
+
+/// `a` ∩ `b`.
+fn intersect_intervals(a: &[(f64, f64)], b: &[(f64, f64)]) -> Vec<(f64, f64)> {
+    let mut out = vec![];
+    for &(s, e) in a {
+        for &(c, d) in b {
+            let (x, y) = (s.max(c), e.min(d));
+            if y > x {
+                out.push((x, y));
+            }
+        }
+    }
+    out
+}
+
+impl Region {
+    pub(super) fn cells(path: &BezPath, opts: &LayoutOptions, wrap: &[vectorcraft_doc::WrapShape]) -> Vec<Region> {
+        // A frame out of range has no cells, and a wrap shape out of range is left out.
+        let Some(polys) = polygons(path) else { return vec![] };
+        // Every cell shares one copy of the frame's polygons and one copy of the text wrap shapes.
+        let polys: std::sync::Arc<[Vec<Point>]> = polys.into();
+        let wraps: std::sync::Arc<[FlatWrap]> = wrap
+            .iter()
+            .filter_map(|w| Some((polygons(&w.path.to_bezpath())?, w.wrap.offset.max(0.0), w.wrap.invert)))
+            .filter(|w| !w.0.is_empty())
+            .collect();
+        let bbox = path.bounding_box();
+        let rect = polys.len() == 1 && {
+            let area: f64 = polys[0].iter().zip(polys[0].iter().cycle().skip(1)).map(|(a, b)| a.x * b.y - b.x * a.y).sum::<f64>().abs() * 0.5;
+            (area - bbox.area()).abs() <= bbox.area() * 1e-6 + 1e-9
+        };
+        let max = vectorcraft_doc::AreaOptions::MAX_ROWS_COLUMNS;
+        let (rows, cols) = (opts.rows.clamp(1, max), opts.columns.clamp(1, max));
+        let gutter = opts.gutter.max(0.0);
+        let cw = ((bbox.width() - gutter * (cols - 1) as f64) / cols as f64).max(0.0);
+        let rh = ((bbox.height() - gutter * (rows - 1) as f64) / rows as f64).max(0.0);
+        let mut out = Vec::with_capacity(rows * cols);
+        // Text flows down each column, then across (Illustrator's default "by columns").
+        for c in 0..cols {
+            for r in 0..rows {
+                let x0 = bbox.x0 + c as f64 * (cw + gutter);
+                let y0 = bbox.y0 + r as f64 * (rh + gutter);
+                let cell = if rows * cols == 1 { bbox } else { Rect::new(x0, y0, x0 + cw, y0 + rh) };
+                out.push(Region { cell, inset: opts.inset.max(0.0), polys: polys.clone(), rect, wraps: wraps.clone(), shift: 0.0, gap: 0.0 });
+            }
+        }
+        out
+    }
+
+    pub(super) fn top(&self) -> f64 {
+        self.cell.y0 + self.inset
+    }
+    pub(super) fn bottom(&self) -> f64 {
+        self.cell.y1 - self.inset
+    }
+
+    /// Inside intervals (even-odd) of the horizontal line at `y`, minus the wrap objects (or
+    /// inside them, for Invert Wrap). Offsets grow each wrap shape vertically and horizontally.
+    fn intervals(&self, y: f64) -> Vec<(f64, f64)> {
+        let mut iv = if self.polys.is_empty() || self.rect { vec![(self.cell.x0, self.cell.x1)] } else { poly_intervals(&self.polys, y) };
+        for (polys, off, invert) in self.wraps.iter() {
+            let ys = if *off > 0.0 { vec![y - off, y - off * 0.5, y, y + off * 0.5, y + off] } else { vec![y] };
+            let w = union_intervals(ys.into_iter().flat_map(|y| poly_intervals(polys, y)).map(|(a, b)| (a - off, b + off)).collect());
+            iv = if *invert { intersect_intervals(&iv, &w) } else { subtract_intervals(&iv, &w) };
+        }
+        iv
+    }
+
+    /// Widest horizontal span inside the frame (and the cell) over the band `top..bottom`.
+    pub(super) fn span(&self, top: f64, bottom: f64) -> Option<(f64, f64)> {
+        self.spans(top, bottom).into_iter().max_by(|x, y| (x.1 - x.0).total_cmp(&(y.1 - y.0)))
+    }
+
+    /// Every horizontal span inside the frame (and the cell) over the band `top..bottom`, left to
+    /// right (text wraps on both sides of an object).
+    pub(super) fn spans(&self, top: f64, bottom: f64) -> Vec<(f64, f64)> {
+        let clip = |(a, b): (f64, f64)| {
+            let (a, b) = (a.max(self.cell.x0) + self.inset, b.min(self.cell.x1) - self.inset);
+            (b > a).then_some((a, b))
+        };
+        let plain = self.polys.is_empty() || self.rect;
+        if plain && self.wraps.is_empty() {
+            return (self.cell.width() > 0.0).then_some((self.cell.x0, self.cell.x1)).and_then(clip).into_iter().collect();
+        }
+        let fb = if plain {
+            self.cell
+        } else {
+            self.polys.iter().flatten().fold(Rect::new(f64::MAX, f64::MAX, f64::MIN, f64::MIN), |r, p| r.union_pt(*p))
+        };
+        let clamp = |y: f64| if plain { y } else { y.clamp(fb.y0 + 1e-4, fb.y1 - 1e-4) };
+        // Sample the band densely enough for curved frames (circles, blobs).
+        let samples = 5;
+        let mut rows: Vec<Vec<(f64, f64)>> =
+            (0..samples).map(|k| self.intervals(clamp(top + (bottom - top) * k as f64 / (samples - 1) as f64))).collect();
+        let mid = rows.swap_remove(samples / 2);
+        if !self.wraps.is_empty() {
+            // Wrap objects split lines: keep exactly what is free on every sampled row.
+            let free = rows.iter().fold(mid, |acc, r| intersect_intervals(&acc, r));
+            return free.into_iter().filter_map(clip).collect();
+        }
+        mid.into_iter()
+            .filter_map(|(mut a, mut b)| {
+                for o in &rows {
+                    let best =
+                        o.iter().map(|&(c, d)| (a.max(c), b.min(d))).filter(|(c, d)| d > c).max_by(|x, y| (x.1 - x.0).total_cmp(&(y.1 - y.0)))?;
+                    a = best.0;
+                    b = best.1;
+                }
+                clip((a, b))
+            })
+            .collect()
+    }
+}
+
+/// The 10,000 cells of a frame in 100 rows and 100 columns share one copy of the frame's polygons
+/// and one copy of the text wrap shapes.
+#[cfg(test)]
+#[test]
+fn the_cells_of_a_frame_share_its_polygons_and_the_wrap_shapes() {
+    let frame = kurbo::Circle::new((0.0, 0.0), 1000.0).to_path(0.1);
+    let square = PathData::from_bezpath(&Rect::new(-10.0, -10.0, 10.0, 10.0).to_path(0.1));
+    let wrap = vectorcraft_doc::WrapShape { path: square, wrap: Default::default() };
+    let cells = Region::cells(&frame, &LayoutOptions { rows: 100, columns: 100, ..LayoutOptions::default() }, &[wrap]);
+    assert_eq!(cells.len(), 10_000);
+    let first = &cells[0];
+    assert!(!first.polys.is_empty() && !first.wraps.is_empty());
+    assert!(cells.iter().all(|c| c.polys.as_ptr() == first.polys.as_ptr() && c.wraps.as_ptr() == first.wraps.as_ptr()));
+}

crates/text/src/layout/ruby.rs

@@ -0,0 +1,304 @@
+use super::driver::layout;
+use super::*;
+
+/// Ruby (furigana): lays each reading out over its base text in line space, grows the line's
+/// ascent/descent so the ruby fits, and moves the lines after it on in the block direction.
+///
+/// Positions are measured from the line's baseline. Vertical type uses the same geometry — ruby
+/// "above" the baseline is right of the column once the lines are turned — with each reading
+/// character set upright along the column (a quarter turn that the final vertical turn undoes).
+/// A reading over a line break is split between the lines, by the base characters' share of it.
+/// A reading wider than its base hangs over the neighbours (`overhang`), or is squeezed to the
+/// base's width. Type on a path is left out (it has no above/below).
+pub(super) fn ruby_layout(cx: &mut Ctx<'_>, t: &TextObject) {
+    use std::collections::BTreeMap;
+
+    let db = cx.db;
+    let text_len = cx.text.len();
+    let n_lines = cx.out.lines.len();
+    if n_lines == 0 || cx.out.glyphs.is_empty() {
+        return;
+    }
+    let base_baselines: Vec<f64> = cx.out.lines.iter().map(|l| l.baseline).collect();
+    let old_ascent: Vec<f64> = cx.out.lines.iter().map(|l| l.ascent).collect();
+    let old_descent: Vec<f64> = cx.out.lines.iter().map(|l| l.descent).collect();
+    // One piece of base text on one line, with the part of the reading that belongs to it.
+    struct Piece {
+        line: usize,
+        x0: f64,
+        x1: f64,
+        run: usize,
+        byte: usize,
+        reading: String,
+        style: CharStyle,
+        position: RubyPosition,
+        align: RubyAlign,
+        base_size: f64,
+        overhang: bool,
+    }
+    let mut pieces: Vec<Piece> = Vec::new();
+    // The glyphs by their byte, to find a span's without a scan of them all for each span.
+    let byte_of = |i: usize| cx.out.glyphs.get(i).map_or(0, |g| g.byte);
+    let mut by_byte: Vec<usize> = (0..cx.out.glyphs.len()).collect();
+    by_byte.sort_by_key(|&i| byte_of(i));
+    let longest = cx.out.glyphs.iter().map(|g| g.len.max(1)).max().unwrap_or(1);
+    for span in &t.ruby {
+        let (start, end) = (span.start.min(text_len), span.end.min(text_len));
+        if start >= end || span.text.trim().is_empty() {
+            continue;
+        }
+        // The base glyphs of the span, by line; a glyph's cluster is its byte range (`len`, or
+        // one byte for generated glyphs). A list marker is not part of the base.
+        let mut by_line: BTreeMap<usize, Vec<usize>> = BTreeMap::new();
+        let hi = by_byte.partition_point(|&i| byte_of(i) < end);
+        let lo = by_byte.partition_point(|&i| byte_of(i).saturating_add(longest) <= start).min(hi);
+        let mut hits: Vec<usize> = by_byte.get(lo..hi).unwrap_or_default().to_vec();
+        // In glyph order, as the scan found them.
+        hits.sort_unstable();
+        for i in hits {
+            let Some(g) = cx.out.glyphs.get(i) else { continue };
+            let b = g.byte.saturating_add(g.len.max(1));
+            if g.byte < end && b > start && cx.out.marker_of(i).is_none() {
+                by_line.entry(g.line).or_default().push(i);
+            }
+        }
+        let total: usize = by_line.values().map(Vec::len).sum();
+        if total == 0 {
+            continue;
+        }
+        let reading: Vec<char> = span.text.trim().chars().collect();
+        let ratio = span.safe_size_percent() / 100.0;
+        // Split the reading by each line's share of the base glyphs: cumulative fractions keep
+        // every character once and in order.
+        let mut taken = 0;
+        let mut done = 0;
+        let lines: Vec<usize> = by_line.keys().copied().collect();
+        for line in &lines {
+            let count = by_line.get(line).map_or(0, Vec::len);
+            done += count;
+            let upto = if reading.is_empty() { 0 } else { (reading.len() * done / total).min(reading.len()) };
+            let part: String = reading.get(taken.min(reading.len())..upto.min(reading.len())).unwrap_or_default().iter().collect();
+            taken = upto;
+            if part.is_empty() {
+                continue;
+            }
+            let glyphs = by_line.get(line).map(Vec::as_slice).unwrap_or_default();
+            let mut x0 = f64::INFINITY;
+            let mut x1 = f64::NEG_INFINITY;
+            let mut base_size: f64 = 0.0;
+            let mut run = 0;
+            let mut byte = start;
+            for (j, &gi) in glyphs.iter().enumerate() {
+                let Some(g) = cx.out.glyphs.get(gi) else { continue };
+                x0 = x0.min(g.origin.x);
+                x1 = x1.max(g.origin.x + g.advance);
+                base_size = base_size.max(cx.style_at(g.byte).size);
+                if j == 0 {
+                    run = g.run;
+                    byte = g.byte;
+                }
+            }
+            if !(x0.is_finite() && x1.is_finite()) || base_size <= 0.0 {
+                continue;
+            }
+            let mut style = cx.style_at(byte).clone();
+            style.size = base_size * ratio;
+            style.leading = None;
+            style.baseline_shift = 0.0;
+            style.tracking = 0.0;
+            style.kerning = None;
+            pieces.push(Piece {
+                line: *line,
+                x0,
+                x1,
+                run,
+                byte,
+                reading: part,
+                style,
+                position: span.position,
+                align: span.align,
+                base_size,
+                overhang: span.overhang,
+            });
+        }
+    }
+    // Phase A: shape each reading, place it relative to the (unshifted) baseline, and note how
+    // far above/below the baseline its ink reaches.
+    let mut placed: Vec<(usize, Vec<PositionedGlyph>, f64, f64)> = Vec::new(); // (line, glyphs, ascent, descent)
+    for piece in &pieces {
+        let Some(baseline) = base_baselines.get(piece.line).copied() else { continue };
+        let mini = TextObject::point(Point::ZERO, &piece.reading, piece.style.clone());
+        let lay = layout(db, &mini);
+        let Some(first_line) = lay.lines.first() else { continue };
+        let mini_base = first_line.baseline;
+        let mini_asc = first_line.ascent;
+        let mini_desc = first_line.descent;
+        let base_w = (piece.x1 - piece.x0).max(0.0);
+        // Above: the reading's bottom sits on the base's em box top. Below: its top sits on the
+        // base's em box bottom (the line's descent below the baseline).
+        let ruby_y = if piece.position == RubyPosition::Above {
+            baseline - piece.base_size - mini_desc
+        } else {
+            baseline + old_descent.get(piece.line).copied().unwrap_or(0.0) + mini_asc
+        };
+        let dest = |width: f64| match piece.align {
+            RubyAlign::Center => piece.x0 + (base_w - width) * 0.5,
+            RubyAlign::Start => piece.x0,
+            RubyAlign::End => piece.x1 - width,
+        };
+        let mut glyphs: Vec<PositionedGlyph> = Vec::new();
+        if cx.vertical {
+            // Each reading character in its own cell along the column, upright once the lines turn.
+            let cell = (mini_asc + mini_desc).max(piece.style.size * 0.5);
+            let mut clusters: Vec<Vec<&PositionedGlyph>> = Vec::new();
+            for g in &lay.glyphs {
+                match clusters.last_mut() {
+                    Some(c) if c.last().is_some_and(|p| p.byte == g.byte && p.len == g.len) => c.push(g),
+                    _ => clusters.push(vec![g]),
+                }
+            }
+            let mut ruby_w = clusters.len() as f64 * cell;
+            let mut squeeze = 1.0;
+            if !piece.overhang && ruby_w > base_w + EPS && ruby_w > EPS {
+                squeeze = base_w / ruby_w;
+                ruby_w = base_w;
+            }
+            let x = dest(ruby_w);
+            for (ci, cluster) in clusters.iter().enumerate() {
+                let anchor = Point::new(x + (ci as f64 + 0.5) * cell, ruby_y);
+                let mut box_: Option<Rect> = None;
+                for g in cluster {
+                    if g.outline.elements().is_empty() {
+                        continue;
+                    }
+                    let b = g.outline.bounding_box();
+                    box_ = Some(box_.map_or(b, |a| a.union(b)));
+                }
+                let centre = box_.map_or(anchor, |b| Point::new((b.x0 + b.x1) * 0.5, (b.y0 + b.y1) * 0.5));
+                let mut m =
+                    Affine::rotate_about(-std::f64::consts::FRAC_PI_2, anchor) * Affine::translate((anchor.x - centre.x, anchor.y - centre.y));
+                if squeeze != 1.0 {
+                    m = Affine::translate((x, 0.0)) * Affine::scale_non_uniform(squeeze, 1.0) * Affine::translate((-x, 0.0)) * m;
+                }
+                for g in cluster {
+                    glyphs.push(ruby_glyph(g, m, piece.run, piece.byte, piece.line));
+                }
+            }
+        } else {
+            // The reading set along the line: the line's extent, centred or aligned to the base.
+            let mut ruby_w = (first_line.x1 - first_line.x0).max(0.0);
+            let mut squeeze = 1.0;
+            if !piece.overhang && ruby_w > base_w + EPS && ruby_w > EPS {
+                squeeze = base_w / ruby_w;
+                ruby_w = base_w;
+            }
+            let x = dest(ruby_w);
+            let mut m = Affine::translate((x - first_line.x0, ruby_y - mini_base));
+            if squeeze != 1.0 {
+                m = Affine::translate((x, 0.0)) * Affine::scale_non_uniform(squeeze, 1.0) * Affine::translate((-x, 0.0)) * m;
+            }
+            for g in &lay.glyphs {
+                glyphs.push(ruby_glyph(g, m, piece.run, piece.byte, piece.line));
+            }
+        }
+        // How far the reading reaches above and below the base line's baseline (its ink).
+        let mut ascent: f64 = 0.0;
+        let mut descent: f64 = 0.0;
+        for g in &glyphs {
+            if g.outline.elements().is_empty() {
+                continue;
+            }
+            let b = g.outline.bounding_box();
+            ascent = ascent.max(baseline - b.y0);
+            descent = descent.max(b.y1 - baseline);
+        }
+        if !glyphs.is_empty() {
+            placed.push((piece.line, glyphs, ascent, descent));
+        }
+    }
+    if placed.is_empty() {
+        return;
+    }
+    // Phase B: grow each line's box to fit its ruby, then move the lines on after it by what they
+    // need in the block direction (the first line too for area type, so the ruby stays inside the
+    // frame; point type's first baseline is its anchor and stays).
+    let mut growth = vec![0.0_f64; n_lines];
+    for (line, _, ascent, descent) in &placed {
+        if let (Some(a), Some(d)) = (old_ascent.get(*line), old_descent.get(*line)) {
+            let grown = (a.max(*ascent) + d.max(*descent)) - (a + d);
+            if grown > 0.0 {
+                let g = growth.get_mut(*line);
+                if let Some(slot) = g {
+                    *slot = slot.max(grown);
+                }
+            }
+        }
+    }
+    // A line's ruby grows above it: the line moves on in the block direction by its own growth,
+    // so the line before it keeps its room (for area type the first line moves too, keeping the
+    // ruby inside the frame; point type's first baseline is its anchor and stays).
+    let area = matches!(t.kind, TextKind::Area { .. });
+    let mut shift = vec![0.0_f64; n_lines];
+    let mut cum = 0.0;
+    for i in 0..n_lines {
+        if area || i > 0 {
+            cum += growth.get(i).copied().unwrap_or(0.0);
+            if let Some(s) = shift.get_mut(i) {
+                *s = cum;
+            }
+        }
+    }
+    // Grow the lines' boxes to fit their ruby, then move them on in the block direction.
+    for (line, _, ascent, descent) in &placed {
+        if let Some(l) = cx.out.lines.get_mut(*line) {
+            l.ascent = l.ascent.max(*ascent);
+            l.descent = l.descent.max(*descent);
+        }
+    }
+    for (i, line) in cx.out.lines.iter_mut().enumerate() {
+        line.baseline += shift.get(i).copied().unwrap_or(0.0);
+    }
+    for g in &mut cx.out.glyphs {
+        let s = shift.get(g.line).copied().unwrap_or(0.0);
+        if s != 0.0 {
+            g.origin.y += s;
+            g.outline.apply_affine(Affine::translate((0.0, s)));
+            g.xf = Affine::translate((0.0, s)) * g.xf;
+        }
+    }
+    for (line, glyphs, _, _) in placed {
+        let s = shift.get(line).copied().unwrap_or(0.0);
+        for mut g in glyphs {
+            if s != 0.0 {
+                g.origin.y += s;
+                g.outline.apply_affine(Affine::translate((0.0, s)));
+            }
+            g.line = line;
+            cx.out.ruby.push(g);
+        }
+    }
+}
+
+/// A ruby glyph from one of a reading's laid-out glyphs, moved by `m` into the base text's line
+/// space. It is not a character of the text: `len` 0, the base text's `run` for fill and stroke.
+fn ruby_glyph(g: &PositionedGlyph, m: Affine, run: usize, byte: usize, line: usize) -> PositionedGlyph {
+    PositionedGlyph {
+        outline: m * g.outline.clone(),
+        run,
+        byte,
+        origin: m * g.origin,
+        advance: 0.0,
+        len: 0,
+        angle: 0.0,
+        line,
+        font_id: g.font_id,
+        gid: g.gid,
+        xf: Affine::IDENTITY,
+        rtl: false,
+        scale: 1.0,
+        // Ruby draws outlines only.
+        image: None,
+        colour: None,
+        bend: None,
+    }
+}

crates/text/src/layout/vertical.rs

@@ -0,0 +1,419 @@
+use super::flow::flow;
+use super::region::Region;
+use super::*;
+
+/// System Layout on or Fractional Widths off: each character that takes space advances by a whole
+/// number of points, at least one, so small type does not collapse onto itself. A zero advance (a
+/// tate-chu-yoko continuation, a zero-width mark) stays zero.
+pub(super) fn whole_character_widths(glyphs: &mut [SGlyph]) {
+    for g in glyphs {
+        if g.adv.is_finite() && g.adv > 0.0 {
+            g.adv = g.adv.round().max(1.0);
+        }
+    }
+}
+
+/// Tate-chu-yoko: a horizontal block one em of the column long, squeezed to the em when wider.
+///
+/// Automatic: a run of two or three half-width digits (`10`月, `100`年). A single digit and a
+/// longer number (`2026`) stay on their side.
+///
+/// Manual (Character panel menu › Tate-chu-yoko): any characters marked `tateChuYoko`, including
+/// one character, letters and numbers longer than three digits. Marked characters are taken
+/// before the automatic digit rule.
+/// <https://helpx.adobe.com/illustrator/using/formatting-asian-characters.html>
+pub(super) fn tate_chu_yoko(g: &mut [SGlyph], style: impl Fn(&SGlyph) -> (f64, bool)) {
+    let manual: Vec<bool> = g.iter().map(|gl| style(gl).1).collect();
+    let digits: Vec<bool> = g.iter().map(|gl| gl.inline.is_none() && gl.ch.is_ascii_digit()).collect();
+    let mut i = 0;
+    while i < g.len() {
+        if manual.get(i).copied().unwrap_or(false) {
+            let mut end = i + 1;
+            while manual.get(end).copied().unwrap_or(false) {
+                end += 1;
+            }
+            let em = style(&g[i]).0;
+            place_tcy_block(&mut g[i..end], em);
+            i = end;
+            continue;
+        }
+        if !digits.get(i).copied().unwrap_or(false) {
+            i += 1;
+            continue;
+        }
+        let mut end = i + 1;
+        while digits.get(end).copied().unwrap_or(false) && !manual.get(end).copied().unwrap_or(false) {
+            end += 1;
+        }
+        if (2..=3).contains(&(end - i)) {
+            let em = style(&g[i]).0;
+            place_tcy_block(&mut g[i..end], em);
+        }
+        i = end;
+    }
+}
+
+/// Lay `g` across one em of the column. The first glyph takes the em; the rest share its cell.
+fn place_tcy_block(g: &mut [SGlyph], em: f64) {
+    let width: f64 = g.iter().map(|gl| gl.adv).sum();
+    let squeeze = if width > em && width > 0.0 { em / width } else { 1.0 };
+    let mut ink = 0.0;
+    for (k, gl) in g.iter_mut().enumerate() {
+        let adv = gl.adv;
+        gl.tcy = Some(Tcy { pen: if k == 0 { 0.0 } else { em }, ink, width, squeeze });
+        gl.adv = if k == 0 { em } else { 0.0 };
+        ink += adv;
+    }
+}
+
+/// Half an em of `g`'s size when it is full-width Japanese punctuation of kind `kind` (its
+/// advance an em, give or take a tenth), the space that mojikumi can take off.
+pub(super) fn punct_half(g: &SGlyph, kind: Punct) -> Option<f64> {
+    // A glyph Proportional Metrics re-spaced has no empty half left to take off (#966).
+    if punct(g.ch)? != kind || g.tcy.is_some() || g.proportional {
+        return None;
+    }
+    let em = g.face.units_per_em();
+    ((g.face.advance(g.gid) - em).abs() <= em * 0.1).then_some(em * 0.5 * g.sx)
+}
+
+/// Mojikumi (JLREQ 3.1.4): consecutive punctuation shares one half-em space. A closing bracket,
+/// comma or full stop followed by punctuation loses the space after it; an opening bracket after
+/// another loses the space before it. Returns which glyphs lost the space after them (a line
+/// ending in one takes nothing more off).
+pub(super) fn compress_punctuation(sg: &mut [SGlyph]) -> Vec<bool> {
+    let mut lost_after = vec![false; sg.len()];
+    for j in 1..sg.len() {
+        let (before, after) = sg.split_at_mut(j);
+        let (Some(a), Some(b)) = (before.last_mut(), after.first_mut()) else { continue };
+        if punct(b.ch).is_none() {
+            continue;
+        }
+        if let Some(h) = punct_half(a, Punct::Closing) {
+            a.adv -= h;
+            if let Some(l) = lost_after.get_mut(j - 1) {
+                *l = true;
+            }
+        } else if punct(a.ch) == Some(Punct::Opening)
+            && let Some(h) = punct_half(b, Punct::Opening)
+        {
+            b.adv -= h;
+            b.lead += h;
+        }
+    }
+    lost_after
+}
+
+/// The space between Japanese and Latin letters or digits (JLREQ 3.2.2: a quarter em of the
+/// Japanese characters' size), with Line-end Punctuation Half Width.
+const WAKAN_AKI: f64 = 0.25;
+
+/// A Japanese character for the space next to Latin text: kana and kanji (and full-width
+/// letters, and the iteration and abbreviation marks 々 〆 〇), not punctuation or symbols, nor
+/// Hangul (Korean sets a word space instead).
+fn is_japanese_letter(c: char) -> bool {
+    if matches!(c, '々' | '〆' | '〇') {
+        return true;
+    }
+    is_cjk(c)
+        && !matches!(
+            c as u32,
+            0x3000..=0x303F | 0x3130..=0x318F | 0xAC00..=0xD7AF | 0xFF01..=0xFF0F | 0xFF1A..=0xFF20 | 0xFF3B..=0xFF40 | 0xFF5B..=0xFF65 | 0xFFA0..=0xFFDC
+        )
+        && c != '・'
+        && punct(c).is_none()
+}
+
+/// A Latin letter or digit (or another script's letter), set proportionally.
+fn is_latin_letter(c: char) -> bool {
+    c.is_alphanumeric() && !is_cjk(c)
+}
+
+/// Mojikumi (JLREQ 3.2.2): a quarter em between a Japanese character and a Latin letter or digit,
+/// either way round, added after the first of the two. Returns what each glyph got after it (taken
+/// off again when the line ends there).
+pub(super) fn space_japanese_and_latin(sg: &mut [SGlyph]) -> Vec<f64> {
+    let mut added = vec![0.0; sg.len()];
+    for j in 1..sg.len() {
+        let (before, after) = sg.split_at_mut(j);
+        let (Some(a), Some(b)) = (before.last_mut(), after.first()) else { continue };
+        if a.tcy.is_some() || b.tcy.is_some() {
+            continue;
+        }
+        let japanese = if is_japanese_letter(a.ch) && is_latin_letter(b.ch) {
+            Some(&*a)
+        } else if is_latin_letter(a.ch) && is_japanese_letter(b.ch) {
+            Some(b)
+        } else {
+            None
+        };
+        if let Some(g) = japanese {
+            let aki = WAKAN_AKI * g.face.units_per_em() * g.sx;
+            a.adv += aki;
+            if let Some(x) = added.get_mut(j - 1) {
+                *x = aki;
+            }
+        }
+    }
+    added
+}
+
+/// The size of `g`'s em, in points.
+pub(super) fn glyph_em(g: &SGlyph) -> f64 {
+    g.face.units_per_em() * g.sy
+}
+
+/// How far up (line space) Character Alignment `a` moves glyph `g` on a line whose largest em is
+/// `line_em`: the glyph's em box top, centre or bottom onto the line's (the em box running from
+/// its centre less half an em to its centre plus half an em above the baseline), or its ICF's top
+/// or bottom (the em box's less the face's [`crate::IcfMargins`]; across a vertical line, its
+/// right and left). Nothing on the Roman baseline, or for the line's largest characters.
+///
+/// An inline graphic has its run's em (whatever its scale): it counts as one of the line's
+/// largest characters only when its run's size is, and moves with the text of its run (its art
+/// stays centred on that text's cap height).
+pub(super) fn align_shift(g: &SGlyph, a: vectorcraft_doc::CharAlign, line_em: f64, vertical: bool) -> f64 {
+    use vectorcraft_doc::CharAlign;
+    let icf = || g.face.icf_margins();
+    let k = match a {
+        CharAlign::RomanBaseline => return 0.0,
+        CharAlign::EmBoxTop => 0.5,
+        CharAlign::EmBoxCenter => 0.0,
+        CharAlign::EmBoxBottom => -0.5,
+        CharAlign::IcfTop => 0.5 - if vertical { icf().right } else { icf().top },
+        CharAlign::IcfBottom => -0.5 + if vertical { icf().left } else { icf().bottom },
+    };
+    (g.face.ideographic_centre() + k) * (line_em - glyph_em(g)).max(0.0)
+}
+
+/// The length an upright glyph takes down the column before tracking and justification: its
+/// vertical advance (the font's vertical metrics), else its advance, at least one em.
+pub(super) fn upright_cell(g: &SGlyph) -> f64 {
+    match g.face.vertical_glyph(g.gid) {
+        Some((advance, _)) => advance * g.sy,
+        None => (g.face.advance(g.gid) * g.sx).max(g.face.units_per_em() * g.sx),
+    }
+}
+
+/// Height above the baseline (line space) of the centre of an upright glyph's `cell`, the point it
+/// turns about: from the font's vertical metrics, the cell hanging from the glyph's vertical origin;
+/// else the centre of the ideographic em box ([`EM_CENTER`] of the size `em`).
+pub(super) fn upright_centre(g: &SGlyph, cell: f64, em: f64) -> f64 {
+    match g.face.vertical_glyph(g.gid) {
+        Some((_, origin)) => origin * g.sy - cell * 0.5,
+        None => EM_CENTER * em,
+    }
+}
+
+/// Height of the centre of the ideographic em box above the baseline, in ems (the em box runs
+/// from 0.12 em below the baseline to 0.88 em above it), for fonts without vertical metrics.
+pub(super) const EM_CENTER: f64 = 0.38;
+
+/// A quarter turn clockwise (y down), exact: line space → text space for vertical type.
+pub(super) const QUARTER_TURN: Affine = Affine::new([0.0, 1.0, -1.0, 0.0, 0.0, 0.0]);
+
+/// Does the glyph stand upright in vertical type? CJK characters and symbols do (their vertical
+/// forms come from the font's `vert` feature); Latin letters, digits and other characters lie on
+/// their side. Brackets, the long vowel mark and similar marks that need a vertical form lie on
+/// their side when the font has none (Unicode's Vertical_Orientation Tr).
+/// Fullwidth !/? instead keep the nominal glyph upright (Tu fallback, UAX #50 §3.1):
+/// <https://www.unicode.org/reports/tr50/#vo>.
+pub(super) fn stands_upright(g: &SGlyph) -> bool {
+    let c = g.ch as u32;
+    let upright = matches!(c,
+        0x00A7 | 0x00A9 | 0x00AE | 0x00B1 | 0x00BC..=0x00BE | 0x00D7 | 0x00F7
+        | 0x2016 | 0x2020 | 0x2021 | 0x2030 | 0x2031 | 0x203B | 0x203C | 0x2042 | 0x2047..=0x2049 | 0x2051
+        | 0x20DD..=0x20E0 | 0x20E2..=0x20E4 | 0x2100..=0x2101 | 0x2103..=0x2109 | 0x210F | 0x2113 | 0x2116 | 0x2117
+        | 0x211E..=0x2123 | 0x2125 | 0x2127 | 0x2129 | 0x212E | 0x2135..=0x213F | 0x2145..=0x214A | 0x214C | 0x214D | 0x214F..=0x2189
+        | 0x2460..=0x24FF | 0x25A0..=0x27BF | 0x2B12..=0x2B2F | 0x2B50..=0x2B59
+        | 0x1100..=0x11FF | 0x2E80..=0x303F | 0x3040..=0xA4CF | 0xA960..=0xA97F | 0xAC00..=0xD7FF
+        | 0xE000..=0xFAFF | 0xFE10..=0xFE1F | 0xFE30..=0xFE4F | 0xFE50..=0xFE6F | 0xFF00..=0xFFE7
+        | 0x1F000..=0x1FAFF | 0x20000..=0x3FFFF);
+    if !upright {
+        return false;
+    }
+    let needs_vertical_form = matches!(c,
+        0x3001 | 0x3002 | 0x3008..=0x3011 | 0x3013..=0x301F | 0x3030 | 0x30A0 | 0x30FC
+        | 0xFE50..=0xFE52 | 0xFE59..=0xFE5E | 0xFF08 | 0xFF09 | 0xFF0C | 0xFF0E | 0xFF1A | 0xFF1B
+        | 0xFF3B | 0xFF3D | 0xFF3F | 0xFF5B..=0xFF60 | 0xFFE3);
+    // Without a vertical alternate the shaped glyph is the nominal one.
+    !needs_vertical_form || g.gid != g.face.glyph_for(g.ch)
+}
+
+pub(super) fn finish_bounds(out: &mut TextLayout) {
+    let xf = out.line_xf;
+    let mut b: Option<Rect> = None;
+    let mut add = |r: Rect| b = Some(b.map_or(r, |b| b.union(r)));
+    for g in &out.glyphs {
+        if !g.outline.elements().is_empty() {
+            add(g.outline.bounding_box());
+        }
+        if let Some((image, xf)) = g.placed_image() {
+            add(xf.transform_rect_bbox(image.rect()));
+        }
+        if let Some(b) = g.colour.as_ref().and_then(|c| c.geometric_bounds()) {
+            add(g.xf.transform_rect_bbox(b));
+        }
+    }
+    // Ruby: covered by its line's ascent, but its ink can overhang sideways past the line.
+    for g in &out.ruby {
+        if !g.outline.elements().is_empty() {
+            add(g.outline.bounding_box());
+        }
+    }
+    for i in &out.inlines {
+        add(i.bounds);
+    }
+    if !out.on_path {
+        for l in &out.lines {
+            add(xf.transform_rect_bbox(Rect::new(l.x0.min(l.x1), l.baseline - l.ascent, l.x0.max(l.x1), l.baseline + l.descent)));
+        }
+    }
+    out.bounds = b.unwrap_or_default();
+}
+
+/// Space left in each cell after flowing top-aligned: (space above the first line's ascent, space
+/// below the last line's descent, number of distinct baselines). Cells without lines are `None`.
+fn cell_space(out: &TextLayout, regions: &[Region]) -> Vec<Option<(f64, f64, usize)>> {
+    regions
+        .iter()
+        .enumerate()
+        .map(|(ri, r)| {
+            let mut top = f64::INFINITY;
+            let mut bottom = f64::NEG_INFINITY;
+            let mut baselines: Vec<f64> = vec![];
+            for l in out.lines.iter().filter(|l| l.region == ri) {
+                top = top.min(l.baseline - l.ascent);
+                bottom = bottom.max(l.baseline + l.descent);
+                if !baselines.iter().any(|b| (b - l.baseline).abs() < 1e-6) {
+                    baselines.push(l.baseline);
+                }
+            }
+            if baselines.is_empty() || !top.is_finite() || !bottom.is_finite() {
+                return None;
+            }
+            // Never negative: a full (or overflowing) cell stays where top alignment put it.
+            Some(((top - r.top()).max(0.0), (r.bottom() - bottom).max(0.0), baselines.len()))
+        })
+        .collect()
+}
+
+/// Area Type Options "Align" other than Top: move each cell's lines down. Rectangular cells
+/// without text wrap shift their lines (centre: half the space left below the last line;
+/// bottom: all of it; justify: the first line stays, each further line gets an equal share of it).
+/// Other frames give lines different widths at different heights, so the text flows again with
+/// each cell's lines started lower (or spaced wider) until it settles, at most eight passes; a
+/// pass that would push text out of the frame is undone and retried with half the step.
+pub(super) fn align_vertically(cx: &mut Ctx<'_>, paras: &[Range<usize>], t: &TextObject, regions: &mut [Region]) {
+    let align = cx.opts.vertical_align;
+    let plain = regions.iter().all(|r| (r.rect || r.polys.is_empty()) && r.wraps.is_empty());
+    if plain {
+        let space = cell_space(&cx.out, regions);
+        // Each distinct baseline's index within its cell, for justify.
+        let mut seen: Vec<Vec<f64>> = vec![vec![]; regions.len()];
+        let offs: Vec<f64> = cx
+            .out
+            .lines
+            .iter()
+            .map(|l| {
+                let Some(Some((_, below, n))) = space.get(l.region).copied() else { return 0.0 };
+                match align {
+                    VerticalAlign::Top => 0.0,
+                    VerticalAlign::Center => below * 0.5,
+                    VerticalAlign::Bottom => below,
+                    VerticalAlign::Justify => {
+                        let Some(s) = seen.get_mut(l.region) else { return 0.0 };
+                        let k = s.iter().position(|b| (b - l.baseline).abs() < 1e-6).unwrap_or_else(|| {
+                            s.push(l.baseline);
+                            s.len() - 1
+                        });
+                        if n > 1 { below * k as f64 / (n - 1) as f64 } else { 0.0 }
+                    }
+                }
+            })
+            .collect();
+        for (l, d) in cx.out.lines.iter_mut().zip(&offs) {
+            l.baseline += d;
+        }
+        for g in &mut cx.out.glyphs {
+            let d = offs.get(g.line).copied().unwrap_or(0.0);
+            if d != 0.0 {
+                let m = Affine::translate((0.0, d));
+                g.outline.apply_affine(m);
+                g.xf = m * g.xf;
+                g.origin.y += d;
+            }
+        }
+        // Inline art moves with its glyph's line.
+        for i in &mut cx.out.inlines {
+            let d = cx.out.glyphs.get(i.glyph).and_then(|g| offs.get(g.line)).copied().unwrap_or(0.0);
+            if d != 0.0 {
+                let m = Affine::translate((0.0, d));
+                i.xf = m * i.xf;
+                i.bounds = m.transform_rect_bbox(i.bounds);
+            }
+        }
+        return;
+    }
+    let laid_out = |out: &TextLayout| out.lines.last().map_or(0, |l| l.end);
+    // How much of the measured space a pass takes up: halved after a pass that lost text.
+    let mut step = 1.0;
+    for _ in 0..8 {
+        let space = cell_space(&cx.out, regions);
+        let mut moved = false;
+        let saved: Vec<(f64, f64)> = regions.iter().map(|r| (r.shift, r.gap)).collect();
+        for (r, s) in regions.iter_mut().zip(&space) {
+            let Some((above, below, n)) = *s else { continue };
+            let (shift, gap) = match align {
+                VerticalAlign::Top => (r.shift, r.gap),
+                VerticalAlign::Center => (r.shift + (below - above) * 0.5 * step, r.gap),
+                VerticalAlign::Bottom => (r.shift + below * step, r.gap),
+                VerticalAlign::Justify if n > 1 => (r.shift, r.gap + below * step / (n - 1) as f64),
+                VerticalAlign::Justify => (r.shift, r.gap),
+            };
+            let (shift, gap) = (shift.clamp(0.0, r.cell.height().max(0.0)), gap.clamp(0.0, r.cell.height().max(0.0)));
+            if (shift - r.shift).abs() > 0.25 || (gap - r.gap).abs() > 0.01 {
+                moved = true;
+            }
+            r.shift = shift;
+            r.gap = gap;
+        }
+        if !moved {
+            return;
+        }
+        let before = laid_out(&cx.out);
+        let prev = (
+            std::mem::take(&mut cx.out.glyphs),
+            std::mem::take(&mut cx.out.lines),
+            std::mem::take(&mut cx.out.inlines),
+            std::mem::take(&mut cx.out.markers),
+            std::mem::replace(&mut cx.out.overflow, false),
+        );
+        flow(cx, paras, t, Some(regions));
+        if laid_out(&cx.out) < before {
+            // Text no longer fits (lines got narrower, or flow around a wrap object): undo the
+            // pass and try a smaller step.
+            (cx.out.glyphs, cx.out.lines, cx.out.inlines, cx.out.markers, cx.out.overflow) = prev;
+            for (r, (shift, gap)) in regions.iter_mut().zip(saved) {
+                r.shift = shift;
+                r.gap = gap;
+            }
+            step *= 0.5;
+            if step < 0.1 {
+                return;
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+#[test]
+fn japanese_letters_for_the_latin_space_are_kana_kanji_and_marks_not_hangul_or_punctuation() {
+    for c in ['あ', 'カ', '漢', '々', '〆', '〇', 'Ａ'] {
+        assert!(is_japanese_letter(c), "{c}");
+    }
+    // Hangul in every form: syllables, compatibility jamo (ㄱ ㅏ), half-width jamo (ﾡ).
+    for c in ['한', 'ㄱ', 'ㅏ', '\u{FFA1}', '。', '「', '・', '、', 'a'] {
+        assert!(!is_japanese_letter(c), "{c}");
+    }
+}