From 2d9e537dccd4eeeaa447b639b2071fc668bb2f8b Mon Sep 17 00:00:00 2001
From: aiongg <aiongtaigi@gmail.com>
Date: Mon, 26 Oct 2026 18:17:19 +0000
Subject: [PATCH] refactor(text): move thread.rs tests to thread/tests.rs

---
 crates/text/src/thread.rs       | 341 +-------------------------------
 crates/text/src/thread/tests.rs | 338 +++++++++++++++++++++++++++++++
 2 files changed, 339 insertions(+), 340 deletions(-)
 create mode 100644 crates/text/src/thread/tests.rs

diff --git a/crates/text/src/thread.rs b/crates/text/src/thread.rs
index 0ed8ecd93..27c6a2e70 100644
--- a/crates/text/src/thread.rs
+++ b/crates/text/src/thread.rs
@@ -177,343 +177,4 @@ pub fn distribute_continuing(
 }
 
 #[cfg(test)]
-mod tests {
-    use super::*;
-    use vectorcraft_doc::{CharStyle, Justify, TextKind};
-    use vectorcraft_geom::{Affine, PathData, Rect, shapes};
-
-    fn frame(x: f64) -> TextObject {
-        let mut t = TextObject::point(vectorcraft_geom::Point::ZERO, "", CharStyle::default());
-        t.kind = TextKind::Area { frame: shapes::rectangle(Rect::new(x, 0.0, x + 120.0, 60.0)) };
-        t.xf = Affine::IDENTITY;
-        t
-    }
-
-    /// Type on a straight path `length` long.
-    fn path_frame(length: f64) -> TextObject {
-        let mut t = TextObject::point(vectorcraft_geom::Point::ZERO, "", CharStyle::default());
-        let line = kurbo::Line::new((0.0, 0.0), (length, 0.0));
-        t.kind = TextKind::OnPath { path: PathData::from_bezpath(&kurbo::Shape::to_path(&line, 0.1)), start: 0.0, end: None };
-        t.xf = Affine::IDENTITY;
-        t
-    }
-
-    /// Type on a path that overflows ends its line where its text stops fitting, as area type's
-    /// last line does, so a story flows on from there through area type and type on a path alike.
-    #[test]
-    fn story_flows_across_area_type_and_type_on_a_path() {
-        let db = FontDb::global();
-        let text = "The quick brown fox jumps over the lazy dog. ".repeat(6);
-        let story = vec![TextRun { text: text.clone(), style: CharStyle::default(), inline: None }];
-        let mut path = path_frame(100.0);
-        path.runs = story.clone();
-        let laid = layout(db, &path);
-        let end = laid.lines.first().map_or(0, |l| l.end);
-        assert!(laid.overflow && end > 0 && end < text.len(), "the path's line ends where its text stops: {end}");
-        let (a, b, c) = (frame(0.0), path_frame(100.0), frame(400.0));
-        let parts: Vec<Vec<TextRun>> = distribute(db, &[&a, &b, &c], &story, &[]).into_iter().map(|s| s.runs).collect();
-        let lens: Vec<usize> = parts.iter().map(|p| runs_len(p)).collect();
-        assert!(lens.iter().all(|l| *l > 0), "each frame takes a share: {lens:?}");
-        let joined: String = parts.iter().flatten().map(|r| r.text.as_str()).collect();
-        assert_eq!(joined, text, "no character lost or duplicated");
-        let mut on_path = b.clone();
-        on_path.runs = parts[1].clone();
-        assert!(!layout(db, &on_path).overflow, "the path's share fits it");
-    }
-
-    /// A path that runs out of room at a space holds only what it shows: the space starts the
-    /// next frame, as a space with no room on a path overflows.
-    #[test]
-    fn a_path_that_runs_out_at_a_space_leaves_it_to_the_next_frame() {
-        let db = FontDb::global();
-        let text = "The quick brown fox jumps over the lazy dog. ".repeat(6);
-        let story = vec![TextRun { text: text.clone(), style: CharStyle::default(), inline: None }];
-        let mut at_space = 0;
-        for length in (60..160).step_by(3) {
-            let (a, b) = (path_frame(f64::from(length)), frame(400.0));
-            let parts: Vec<Vec<TextRun>> = distribute(db, &[&a, &b], &story, &[]).into_iter().map(|s| s.runs).collect();
-            let joined: String = parts.iter().flatten().map(|r| r.text.as_str()).collect();
-            assert_eq!(joined, text, "no character lost or duplicated");
-            let mut on_path = a.clone();
-            on_path.runs = parts[0].clone();
-            assert!(!layout(db, &on_path).overflow, "the path's share fits it ({length})");
-            at_space += usize::from(parts[1].iter().map(|r| r.text.as_str()).collect::<String>().starts_with(' '));
-        }
-        assert!(at_space > 0, "some lengths end at a space");
-    }
-
-    /// A right-to-left story flows on from where its text stops fitting a path, in reading order.
-    #[test]
-    fn right_to_left_story_flows_on_from_a_path() {
-        let db = FontDb::global();
-        let text = "שלום עולם ".repeat(8);
-        let story = vec![TextRun { text: text.clone(), style: CharStyle::default(), inline: None }];
-        let (a, b) = (path_frame(100.0), frame(400.0));
-        let parts: Vec<Vec<TextRun>> = distribute(db, &[&a, &b], &story, &[]).into_iter().map(|s| s.runs).collect();
-        let lens: Vec<usize> = parts.iter().map(|p| runs_len(p)).collect();
-        assert!(lens.iter().all(|l| *l > 0), "each frame takes a share: {lens:?}");
-        let joined: String = parts.iter().flatten().map(|r| r.text.as_str()).collect();
-        assert_eq!(joined, text, "no character lost or duplicated");
-        let mut on_path = a.clone();
-        on_path.runs = parts[0].clone();
-        assert!(!layout(db, &on_path).overflow, "the path's share fits it");
-    }
-
-    /// A path with no length holds no text, so the story flows past it.
-    #[test]
-    fn story_flows_past_a_path_with_no_length() {
-        let db = FontDb::global();
-        let text = "The quick brown fox jumps over the lazy dog. ".repeat(6);
-        let story = vec![TextRun { text: text.clone(), style: CharStyle::default(), inline: None }];
-        let (a, b, c) = (frame(0.0), path_frame(0.0), frame(400.0));
-        let parts: Vec<Vec<TextRun>> = distribute(db, &[&a, &b, &c], &story, &[]).into_iter().map(|s| s.runs).collect();
-        let lens: Vec<usize> = parts.iter().map(|p| runs_len(p)).collect();
-        assert!(lens[0] > 0 && lens[1] == 0 && lens[2] > 0, "{lens:?}");
-        let joined: String = parts.iter().flatten().map(|r| r.text.as_str()).collect();
-        assert_eq!(joined, text, "no character lost or duplicated");
-    }
-
-    #[test]
-    fn story_flows_across_frames_and_rejoins() {
-        let db = FontDb::global();
-        let (a, b, c) = (frame(0.0), frame(200.0), frame(400.0));
-        let text = "The quick brown fox jumps over the lazy dog. ".repeat(6) + "\nSecond paragraph here.";
-        let story = vec![TextRun { text: text.clone(), style: CharStyle::default(), inline: None }];
-        let parts: Vec<Vec<TextRun>> = distribute(db, &[&a, &b, &c], &story, &[]).into_iter().map(|s| s.runs).collect();
-        let lens: Vec<usize> = parts.iter().map(|p| runs_len(p)).collect();
-        assert!(lens[0] > 0 && lens[1] > 0, "{lens:?}");
-        let joined: String = parts.iter().flatten().map(|r| r.text.as_str()).collect();
-        assert_eq!(joined, text, "no character lost or duplicated");
-        // Each non-last slice fits its frame.
-        for (f, p) in [&a, &b].iter().zip(&parts) {
-            let mut t = (*f).clone();
-            t.runs = p.clone();
-            assert!(!layout(db, &t).overflow);
-        }
-        // Lines never start with the break space.
-        assert!(!parts[1][0].text.starts_with(' '));
-    }
-
-    #[test]
-    fn paragraph_styles_flow_with_their_paragraphs() {
-        let db = FontDb::global();
-        let (a, b) = (frame(0.0), frame(200.0));
-        let text = "The quick brown fox jumps over the lazy dog. ".repeat(4) + "\nSecond paragraph.\nThird.";
-        let story = vec![TextRun { text, style: CharStyle::default(), inline: None }];
-        let style = |j| ParaStyle { justify: j, ..Default::default() };
-        use vectorcraft_doc::Justify::*;
-        let paras = vec![style(Left), style(Center), style(Right)];
-        let parts = distribute(db, &[&a, &b], &story, &paras);
-        assert!(!parts[0].runs.is_empty() && !parts[1].runs.is_empty());
-        // The first paragraph overflows into the second frame: it is in both, with its style.
-        let pa: Vec<Justify> = parts[0].paras.iter().map(|p| p.justify).collect();
-        let pb: Vec<Justify> = parts[1].paras.iter().map(|p| p.justify).collect();
-        assert_eq!(pa, [Left]);
-        assert_eq!(pb, [Left, Center, Right]);
-        // Joined again, the shared paragraph counts once.
-        let mut fa = a.clone();
-        fa.runs = parts[0].runs.clone();
-        fa.set_paragraph_styles(parts[0].paras.clone());
-        let mut fb = b.clone();
-        fb.runs = parts[1].runs.clone();
-        fb.set_paragraph_styles(parts[1].paras.clone());
-        assert_eq!(story_paras(&[&fa, &fb], &[]), paras);
-        // A frame whose shared first paragraph was restyled wins.
-        fb.edit_paras(Some(0..1), |p| p.justify = JustifyAll);
-        assert_eq!(story_paras(&[&fa, &fb], &[false, true])[0].justify, JustifyAll);
-        assert_eq!(story_paras(&[&fa, &fb], &[false, false])[0].justify, Left);
-    }
-
-    /// Numbered list paragraphs count on from one frame to the next: the second frame's first
-    /// whole paragraph takes the next number. A paragraph split between the frames has its number
-    /// in the first frame only, and the paragraph after it takes the next number.
-    #[test]
-    fn numbered_list_paragraphs_count_on_through_the_frames() {
-        use vectorcraft_doc::text::{NumberStyle, ParaList};
-        let db = FontDb::global();
-        let (a, mut b) = (frame(0.0), frame(200.0));
-        b.kind = TextKind::Area { frame: shapes::rectangle(Rect::new(200.0, 0.0, 320.0, 400.0)) };
-        let numbered =
-            ParaStyle { list: Some(ParaList::numbered(NumberStyle::Arabic)), left_indent: 18.0, first_line_indent: -18.0, ..Default::default() };
-        let numbers = |f: &TextObject, s: &Slice| {
-            let mut t = f.clone();
-            t.runs = s.runs.clone();
-            t.set_paragraph_styles(s.paras.clone());
-            t.list_count = s.list_count;
-            t.first_para_continues = s.continues;
-            layout(db, &t).markers.iter().map(|m| m.text.clone()).collect::<Vec<_>>()
-        };
-        // Whole paragraphs: the first frame ends with a paragraph break.
-        let text = (1..=8).map(|i| format!("Item {i}")).collect::<Vec<_>>().join("\n");
-        let story = vec![TextRun { text, style: CharStyle::default(), inline: None }];
-        let parts = distribute(db, &[&a, &b], &story, &vec![numbered.clone(); 8]);
-        let first = numbers(&a, &parts[0]);
-        assert!((2..8).contains(&first.len()), "both frames hold items: {first:?}");
-        assert_eq!(parts.iter().map(|s| s.list_count).collect::<Vec<_>>(), [0, first.len() as u32]);
-        let second = numbers(&b, &parts[1]);
-        let expected: Vec<String> = (first.len() + 1..=8).map(|n| format!("{n}.")).collect();
-        assert_eq!(second, expected, "{first:?}");
-        // A paragraph split between the frames.
-        let text = format!("One\nTwo\n{}\nFour", "The quick brown fox jumps over the lazy dog. ".repeat(4));
-        let story = vec![TextRun { text, style: CharStyle::default(), inline: None }];
-        let parts = distribute(db, &[&a, &b], &story, &vec![numbered; 4]);
-        assert_eq!(parts.iter().map(|s| s.continues).collect::<Vec<_>>(), [false, true]);
-        assert_eq!((numbers(&a, &parts[0]), numbers(&b, &parts[1])), (vec!["1.".to_string(), "2.".into(), "3.".into()], vec!["4.".to_string()]));
-    }
-
-    /// Frame `f` holding slice `p`, laid out.
-    fn laid(db: &FontDb, f: &TextObject, p: &Slice) -> crate::TextLayout {
-        let mut t = f.clone();
-        t.runs = p.runs.clone();
-        t.set_paragraph_styles(p.paras.clone());
-        t.list_count = p.list_count;
-        t.first_para_continues = p.continues;
-        layout(db, &t)
-    }
-
-    /// Where line `k` of `lay` starts: its first glyph that stands for a character.
-    fn line_start(lay: &crate::TextLayout, k: usize) -> f64 {
-        let l = &lay.lines[k];
-        lay.glyphs[l.glyph_start..l.glyph_end].iter().find(|g| g.len > 0).map_or(f64::NAN, |g| g.origin.x)
-    }
-
-    /// A paragraph's first-line indent and bullet belong to its first line: a paragraph that
-    /// continues from one frame into the next starts the next frame at its left indent, without its
-    /// bullet, and every line stays inside its frame. A paragraph that starts at the top of a frame
-    /// keeps both there.
-    #[test]
-    fn a_paragraph_continued_into_the_next_frame_has_no_first_line_indent_or_bullet_there() {
-        use vectorcraft_doc::text::{Bullet, ParaList};
-        let db = FontDb::global();
-        let (a, b, mut c) = (frame(0.0), frame(200.0), frame(400.0));
-        c.kind = TextKind::Area { frame: shapes::rectangle(Rect::new(400.0, 0.0, 520.0, 300.0)) };
-        let bulleted = ParaStyle { left_indent: 18.0, first_line_indent: -18.0, list: Some(ParaList::bulleted(Bullet::Dot)), ..Default::default() };
-        let indented = ParaStyle { first_line_indent: 30.0, ..Default::default() };
-        let long = "The quick brown fox jumps over the lazy dog. ".repeat(9) + "\nSecond paragraph.";
-        for para in [bulleted, indented] {
-            let (left, first) = (para.left_indent, para.left_indent + para.first_line_indent);
-            let list = usize::from(para.list.is_some());
-            let story = vec![TextRun { text: long.clone(), style: CharStyle::default(), inline: None }];
-            let parts = distribute(db, &[&a, &b, &c], &story, &[para.clone(), para.clone()]);
-            assert_eq!(
-                parts.iter().map(|p| p.continues).collect::<Vec<_>>(),
-                [false, true, true],
-                "{:?}",
-                parts.iter().map(|p| runs_len(&p.runs)).collect::<Vec<_>>()
-            );
-            let joined: String = parts.iter().flat_map(|p| &p.runs).map(|r| r.text.as_str()).collect();
-            assert_eq!(joined, long, "no character lost or duplicated");
-            // [`continued`] reads the same marks from the frames' text.
-            assert_eq!(continued(&filled(&[&a, &b, &c], &parts).iter().collect::<Vec<_>>()), [false, true, true]);
-            let lays: Vec<_> = [&a, &b, &c].iter().zip(&parts).map(|(f, p)| laid(db, f, p)).collect();
-            // The first frame: the first line at the first-line indent, after the bullet.
-            assert_eq!(lays[0].markers.len(), list, "{left}");
-            assert!((line_start(&lays[0], 0) - (if list > 0 { left } else { first })).abs() < 1e-6, "{}", line_start(&lays[0], 0));
-            if list > 0 {
-                assert!(lays[0].glyphs[lays[0].markers[0].glyphs.start].origin.x.abs() < 1e-6, "the bullet starts the first frame");
-            }
-            // The frames it continues into: every line at the left indent, no bullet.
-            for (k, (x0, lay)) in [200.0, 400.0].into_iter().zip(&lays[1..]).enumerate() {
-                let on_first = lay.markers.iter().filter(|m| lay.glyphs[m.glyphs.start].line == 0).count();
-                assert_eq!(on_first, 0, "frame {} starts without the bullet", k + 1);
-                assert!((line_start(lay, 0) - x0 - left).abs() < 1e-6, "frame {} starts at {}", k + 1, line_start(lay, 0) - x0);
-                assert!(!lay.overflow, "frame {} holds its share", k + 1);
-                for l in &lay.lines {
-                    assert!(l.x1 <= x0 + 120.0 + 1e-6, "frame {}: a line ends at {}", k + 1, l.x1 - x0);
-                }
-            }
-            // The second paragraph, in the last frame, starts with its own first line.
-            let last = &lays[2];
-            let shown: String = parts[2].runs.iter().map(|r| r.text.as_str()).collect();
-            let second = last.lines.iter().position(|l| shown.get(l.start..).is_some_and(|s| s.starts_with("Second"))).unwrap();
-            assert!((line_start(last, second) - 400.0 - if list > 0 { left } else { first }).abs() < 1e-6, "{}", line_start(last, second));
-            assert_eq!(last.markers.len(), list, "the second paragraph's bullet");
-
-            // One-line paragraphs: the second frame starts with a paragraph of its own.
-            let lines = "Short line.\n".repeat(12);
-            let story = vec![TextRun { text: lines.clone(), style: CharStyle::default(), inline: None }];
-            let parts = distribute(db, &[&a, &b], &story, std::slice::from_ref(&para));
-            assert_eq!(parts.iter().map(|p| p.continues).collect::<Vec<_>>(), [false, false]);
-            let lay = laid(db, &b, &parts[1]);
-            assert!((line_start(&lay, 0) - 200.0 - if list > 0 { left } else { first }).abs() < 1e-6, "{}", line_start(&lay, 0));
-            if list > 0 {
-                assert_eq!(lay.glyphs[lay.markers[0].glyphs.start].line, 0, "the bullet starts the second frame");
-                assert!((lay.glyphs[lay.markers[0].glyphs.start].origin.x - 200.0).abs() < 1e-6);
-            }
-            assert_eq!(continued(&filled(&[&a, &b], &parts).iter().collect::<Vec<_>>()), [false, false]);
-        }
-    }
-
-    /// A frame that a paragraph continues into holds what fits it laid out that way: its share does
-    /// not overflow it, and the share with the next word added does.
-    #[test]
-    fn a_continued_paragraph_fills_the_frame_it_continues_into() {
-        let db = FontDb::global();
-        let (a, b, mut c) = (frame(0.0), frame(200.0), frame(400.0));
-        c.kind = TextKind::Area { frame: shapes::rectangle(Rect::new(400.0, 0.0, 520.0, 300.0)) };
-        let hanging = ParaStyle { left_indent: 18.0, first_line_indent: -18.0, ..Default::default() };
-        let indented = ParaStyle { first_line_indent: 30.0, ..Default::default() };
-        let mut checked = 0;
-        for para in [hanging, indented] {
-            for k in 0..8 {
-                let text = "a ".repeat(k) + &"The quick brown fox jumps over the lazy dog. ".repeat(9);
-                let story = vec![TextRun { text, style: CharStyle::default(), inline: None }];
-                let parts = distribute(db, &[&a, &b, &c], &story, std::slice::from_ref(&para));
-                assert!(parts[1].continues, "{k}");
-                assert!(!laid(db, &b, &parts[1]).overflow, "the second frame holds its share ({k})");
-                let next: String = parts[2].runs.iter().map(|r| r.text.as_str()).collect();
-                let word = next.split_inclusive(' ').next().unwrap_or_default();
-                let mut more = parts[1].clone();
-                more.runs.push(TextRun { text: word.to_string(), style: CharStyle::default(), inline: None });
-                normalize(&mut more.runs);
-                assert!(laid(db, &b, &more).overflow, "the second frame has no room for {word:?} ({k})");
-                checked += 1;
-            }
-        }
-        assert_eq!(checked, 16);
-    }
-
-    /// `frames` holding the runs of `parts`, for [`continued`].
-    fn filled(frames: &[&TextObject], parts: &[Slice]) -> Vec<TextObject> {
-        frames
-            .iter()
-            .zip(parts)
-            .map(|(f, p)| {
-                let mut t = (*f).clone();
-                t.runs = p.runs.clone();
-                t
-            })
-            .collect()
-    }
-
-    /// A paragraph that continues onto type on a path starts the path without its bullet.
-    #[test]
-    fn a_list_paragraph_continued_onto_a_path_has_no_bullet_there() {
-        use vectorcraft_doc::text::{Bullet, ParaList};
-        let db = FontDb::global();
-        let para = ParaStyle { left_indent: 18.0, first_line_indent: -18.0, list: Some(ParaList::bulleted(Bullet::Dot)), ..Default::default() };
-        let text = "The quick brown fox jumps over the lazy dog. ".repeat(6);
-        let story = vec![TextRun { text: text.clone(), style: CharStyle::default(), inline: None }];
-        let (a, b) = (frame(0.0), path_frame(300.0));
-        let parts = distribute(db, &[&a, &b], &story, std::slice::from_ref(&para));
-        assert_eq!(parts.iter().map(|p| p.continues).collect::<Vec<_>>(), [false, true]);
-        let (la, lb) = (laid(db, &a, &parts[0]), laid(db, &b, &parts[1]));
-        assert_eq!((la.markers.len(), lb.markers.len()), (1, 0));
-        // The same paragraph starting on the path has its bullet there.
-        let mut alone = b.clone();
-        alone.runs = story;
-        alone.set_paragraph_styles(vec![para]);
-        assert_eq!(layout(db, &alone).markers.len(), 1);
-    }
-
-    #[test]
-    fn short_story_leaves_later_frames_empty_with_a_style() {
-        let db = FontDb::global();
-        let (a, b) = (frame(0.0), frame(200.0));
-        let st = CharStyle { size: 20.0, ..Default::default() };
-        let parts: Vec<Vec<TextRun>> =
-            distribute(db, &[&a, &b], &[TextRun { text: "Hi".into(), style: st, inline: None }], &[]).into_iter().map(|s| s.runs).collect();
-        assert_eq!(parts[0][0].text, "Hi");
-        assert_eq!((parts[1][0].text.as_str(), parts[1][0].style.size), ("", 20.0));
-    }
-}
+mod tests;
diff --git a/crates/text/src/thread/tests.rs b/crates/text/src/thread/tests.rs
new file mode 100644
index 000000000..cc07dcec1
--- /dev/null
+++ b/crates/text/src/thread/tests.rs
@@ -0,0 +1,338 @@
+use super::*;
+use vectorcraft_doc::{CharStyle, Justify, TextKind};
+use vectorcraft_geom::{Affine, PathData, Rect, shapes};
+
+fn frame(x: f64) -> TextObject {
+    let mut t = TextObject::point(vectorcraft_geom::Point::ZERO, "", CharStyle::default());
+    t.kind = TextKind::Area { frame: shapes::rectangle(Rect::new(x, 0.0, x + 120.0, 60.0)) };
+    t.xf = Affine::IDENTITY;
+    t
+}
+
+/// Type on a straight path `length` long.
+fn path_frame(length: f64) -> TextObject {
+    let mut t = TextObject::point(vectorcraft_geom::Point::ZERO, "", CharStyle::default());
+    let line = kurbo::Line::new((0.0, 0.0), (length, 0.0));
+    t.kind = TextKind::OnPath { path: PathData::from_bezpath(&kurbo::Shape::to_path(&line, 0.1)), start: 0.0, end: None };
+    t.xf = Affine::IDENTITY;
+    t
+}
+
+/// Type on a path that overflows ends its line where its text stops fitting, as area type's
+/// last line does, so a story flows on from there through area type and type on a path alike.
+#[test]
+fn story_flows_across_area_type_and_type_on_a_path() {
+    let db = FontDb::global();
+    let text = "The quick brown fox jumps over the lazy dog. ".repeat(6);
+    let story = vec![TextRun { text: text.clone(), style: CharStyle::default(), inline: None }];
+    let mut path = path_frame(100.0);
+    path.runs = story.clone();
+    let laid = layout(db, &path);
+    let end = laid.lines.first().map_or(0, |l| l.end);
+    assert!(laid.overflow && end > 0 && end < text.len(), "the path's line ends where its text stops: {end}");
+    let (a, b, c) = (frame(0.0), path_frame(100.0), frame(400.0));
+    let parts: Vec<Vec<TextRun>> = distribute(db, &[&a, &b, &c], &story, &[]).into_iter().map(|s| s.runs).collect();
+    let lens: Vec<usize> = parts.iter().map(|p| runs_len(p)).collect();
+    assert!(lens.iter().all(|l| *l > 0), "each frame takes a share: {lens:?}");
+    let joined: String = parts.iter().flatten().map(|r| r.text.as_str()).collect();
+    assert_eq!(joined, text, "no character lost or duplicated");
+    let mut on_path = b.clone();
+    on_path.runs = parts[1].clone();
+    assert!(!layout(db, &on_path).overflow, "the path's share fits it");
+}
+
+/// A path that runs out of room at a space holds only what it shows: the space starts the
+/// next frame, as a space with no room on a path overflows.
+#[test]
+fn a_path_that_runs_out_at_a_space_leaves_it_to_the_next_frame() {
+    let db = FontDb::global();
+    let text = "The quick brown fox jumps over the lazy dog. ".repeat(6);
+    let story = vec![TextRun { text: text.clone(), style: CharStyle::default(), inline: None }];
+    let mut at_space = 0;
+    for length in (60..160).step_by(3) {
+        let (a, b) = (path_frame(f64::from(length)), frame(400.0));
+        let parts: Vec<Vec<TextRun>> = distribute(db, &[&a, &b], &story, &[]).into_iter().map(|s| s.runs).collect();
+        let joined: String = parts.iter().flatten().map(|r| r.text.as_str()).collect();
+        assert_eq!(joined, text, "no character lost or duplicated");
+        let mut on_path = a.clone();
+        on_path.runs = parts[0].clone();
+        assert!(!layout(db, &on_path).overflow, "the path's share fits it ({length})");
+        at_space += usize::from(parts[1].iter().map(|r| r.text.as_str()).collect::<String>().starts_with(' '));
+    }
+    assert!(at_space > 0, "some lengths end at a space");
+}
+
+/// A right-to-left story flows on from where its text stops fitting a path, in reading order.
+#[test]
+fn right_to_left_story_flows_on_from_a_path() {
+    let db = FontDb::global();
+    let text = "שלום עולם ".repeat(8);
+    let story = vec![TextRun { text: text.clone(), style: CharStyle::default(), inline: None }];
+    let (a, b) = (path_frame(100.0), frame(400.0));
+    let parts: Vec<Vec<TextRun>> = distribute(db, &[&a, &b], &story, &[]).into_iter().map(|s| s.runs).collect();
+    let lens: Vec<usize> = parts.iter().map(|p| runs_len(p)).collect();
+    assert!(lens.iter().all(|l| *l > 0), "each frame takes a share: {lens:?}");
+    let joined: String = parts.iter().flatten().map(|r| r.text.as_str()).collect();
+    assert_eq!(joined, text, "no character lost or duplicated");
+    let mut on_path = a.clone();
+    on_path.runs = parts[0].clone();
+    assert!(!layout(db, &on_path).overflow, "the path's share fits it");
+}
+
+/// A path with no length holds no text, so the story flows past it.
+#[test]
+fn story_flows_past_a_path_with_no_length() {
+    let db = FontDb::global();
+    let text = "The quick brown fox jumps over the lazy dog. ".repeat(6);
+    let story = vec![TextRun { text: text.clone(), style: CharStyle::default(), inline: None }];
+    let (a, b, c) = (frame(0.0), path_frame(0.0), frame(400.0));
+    let parts: Vec<Vec<TextRun>> = distribute(db, &[&a, &b, &c], &story, &[]).into_iter().map(|s| s.runs).collect();
+    let lens: Vec<usize> = parts.iter().map(|p| runs_len(p)).collect();
+    assert!(lens[0] > 0 && lens[1] == 0 && lens[2] > 0, "{lens:?}");
+    let joined: String = parts.iter().flatten().map(|r| r.text.as_str()).collect();
+    assert_eq!(joined, text, "no character lost or duplicated");
+}
+
+#[test]
+fn story_flows_across_frames_and_rejoins() {
+    let db = FontDb::global();
+    let (a, b, c) = (frame(0.0), frame(200.0), frame(400.0));
+    let text = "The quick brown fox jumps over the lazy dog. ".repeat(6) + "\nSecond paragraph here.";
+    let story = vec![TextRun { text: text.clone(), style: CharStyle::default(), inline: None }];
+    let parts: Vec<Vec<TextRun>> = distribute(db, &[&a, &b, &c], &story, &[]).into_iter().map(|s| s.runs).collect();
+    let lens: Vec<usize> = parts.iter().map(|p| runs_len(p)).collect();
+    assert!(lens[0] > 0 && lens[1] > 0, "{lens:?}");
+    let joined: String = parts.iter().flatten().map(|r| r.text.as_str()).collect();
+    assert_eq!(joined, text, "no character lost or duplicated");
+    // Each non-last slice fits its frame.
+    for (f, p) in [&a, &b].iter().zip(&parts) {
+        let mut t = (*f).clone();
+        t.runs = p.clone();
+        assert!(!layout(db, &t).overflow);
+    }
+    // Lines never start with the break space.
+    assert!(!parts[1][0].text.starts_with(' '));
+}
+
+#[test]
+fn paragraph_styles_flow_with_their_paragraphs() {
+    let db = FontDb::global();
+    let (a, b) = (frame(0.0), frame(200.0));
+    let text = "The quick brown fox jumps over the lazy dog. ".repeat(4) + "\nSecond paragraph.\nThird.";
+    let story = vec![TextRun { text, style: CharStyle::default(), inline: None }];
+    let style = |j| ParaStyle { justify: j, ..Default::default() };
+    use vectorcraft_doc::Justify::*;
+    let paras = vec![style(Left), style(Center), style(Right)];
+    let parts = distribute(db, &[&a, &b], &story, &paras);
+    assert!(!parts[0].runs.is_empty() && !parts[1].runs.is_empty());
+    // The first paragraph overflows into the second frame: it is in both, with its style.
+    let pa: Vec<Justify> = parts[0].paras.iter().map(|p| p.justify).collect();
+    let pb: Vec<Justify> = parts[1].paras.iter().map(|p| p.justify).collect();
+    assert_eq!(pa, [Left]);
+    assert_eq!(pb, [Left, Center, Right]);
+    // Joined again, the shared paragraph counts once.
+    let mut fa = a.clone();
+    fa.runs = parts[0].runs.clone();
+    fa.set_paragraph_styles(parts[0].paras.clone());
+    let mut fb = b.clone();
+    fb.runs = parts[1].runs.clone();
+    fb.set_paragraph_styles(parts[1].paras.clone());
+    assert_eq!(story_paras(&[&fa, &fb], &[]), paras);
+    // A frame whose shared first paragraph was restyled wins.
+    fb.edit_paras(Some(0..1), |p| p.justify = JustifyAll);
+    assert_eq!(story_paras(&[&fa, &fb], &[false, true])[0].justify, JustifyAll);
+    assert_eq!(story_paras(&[&fa, &fb], &[false, false])[0].justify, Left);
+}
+
+/// Numbered list paragraphs count on from one frame to the next: the second frame's first
+/// whole paragraph takes the next number. A paragraph split between the frames has its number
+/// in the first frame only, and the paragraph after it takes the next number.
+#[test]
+fn numbered_list_paragraphs_count_on_through_the_frames() {
+    use vectorcraft_doc::text::{NumberStyle, ParaList};
+    let db = FontDb::global();
+    let (a, mut b) = (frame(0.0), frame(200.0));
+    b.kind = TextKind::Area { frame: shapes::rectangle(Rect::new(200.0, 0.0, 320.0, 400.0)) };
+    let numbered =
+        ParaStyle { list: Some(ParaList::numbered(NumberStyle::Arabic)), left_indent: 18.0, first_line_indent: -18.0, ..Default::default() };
+    let numbers = |f: &TextObject, s: &Slice| {
+        let mut t = f.clone();
+        t.runs = s.runs.clone();
+        t.set_paragraph_styles(s.paras.clone());
+        t.list_count = s.list_count;
+        t.first_para_continues = s.continues;
+        layout(db, &t).markers.iter().map(|m| m.text.clone()).collect::<Vec<_>>()
+    };
+    // Whole paragraphs: the first frame ends with a paragraph break.
+    let text = (1..=8).map(|i| format!("Item {i}")).collect::<Vec<_>>().join("\n");
+    let story = vec![TextRun { text, style: CharStyle::default(), inline: None }];
+    let parts = distribute(db, &[&a, &b], &story, &vec![numbered.clone(); 8]);
+    let first = numbers(&a, &parts[0]);
+    assert!((2..8).contains(&first.len()), "both frames hold items: {first:?}");
+    assert_eq!(parts.iter().map(|s| s.list_count).collect::<Vec<_>>(), [0, first.len() as u32]);
+    let second = numbers(&b, &parts[1]);
+    let expected: Vec<String> = (first.len() + 1..=8).map(|n| format!("{n}.")).collect();
+    assert_eq!(second, expected, "{first:?}");
+    // A paragraph split between the frames.
+    let text = format!("One\nTwo\n{}\nFour", "The quick brown fox jumps over the lazy dog. ".repeat(4));
+    let story = vec![TextRun { text, style: CharStyle::default(), inline: None }];
+    let parts = distribute(db, &[&a, &b], &story, &vec![numbered; 4]);
+    assert_eq!(parts.iter().map(|s| s.continues).collect::<Vec<_>>(), [false, true]);
+    assert_eq!((numbers(&a, &parts[0]), numbers(&b, &parts[1])), (vec!["1.".to_string(), "2.".into(), "3.".into()], vec!["4.".to_string()]));
+}
+
+/// Frame `f` holding slice `p`, laid out.
+fn laid(db: &FontDb, f: &TextObject, p: &Slice) -> crate::TextLayout {
+    let mut t = f.clone();
+    t.runs = p.runs.clone();
+    t.set_paragraph_styles(p.paras.clone());
+    t.list_count = p.list_count;
+    t.first_para_continues = p.continues;
+    layout(db, &t)
+}
+
+/// Where line `k` of `lay` starts: its first glyph that stands for a character.
+fn line_start(lay: &crate::TextLayout, k: usize) -> f64 {
+    let l = &lay.lines[k];
+    lay.glyphs[l.glyph_start..l.glyph_end].iter().find(|g| g.len > 0).map_or(f64::NAN, |g| g.origin.x)
+}
+
+/// A paragraph's first-line indent and bullet belong to its first line: a paragraph that
+/// continues from one frame into the next starts the next frame at its left indent, without its
+/// bullet, and every line stays inside its frame. A paragraph that starts at the top of a frame
+/// keeps both there.
+#[test]
+fn a_paragraph_continued_into_the_next_frame_has_no_first_line_indent_or_bullet_there() {
+    use vectorcraft_doc::text::{Bullet, ParaList};
+    let db = FontDb::global();
+    let (a, b, mut c) = (frame(0.0), frame(200.0), frame(400.0));
+    c.kind = TextKind::Area { frame: shapes::rectangle(Rect::new(400.0, 0.0, 520.0, 300.0)) };
+    let bulleted = ParaStyle { left_indent: 18.0, first_line_indent: -18.0, list: Some(ParaList::bulleted(Bullet::Dot)), ..Default::default() };
+    let indented = ParaStyle { first_line_indent: 30.0, ..Default::default() };
+    let long = "The quick brown fox jumps over the lazy dog. ".repeat(9) + "\nSecond paragraph.";
+    for para in [bulleted, indented] {
+        let (left, first) = (para.left_indent, para.left_indent + para.first_line_indent);
+        let list = usize::from(para.list.is_some());
+        let story = vec![TextRun { text: long.clone(), style: CharStyle::default(), inline: None }];
+        let parts = distribute(db, &[&a, &b, &c], &story, &[para.clone(), para.clone()]);
+        assert_eq!(
+            parts.iter().map(|p| p.continues).collect::<Vec<_>>(),
+            [false, true, true],
+            "{:?}",
+            parts.iter().map(|p| runs_len(&p.runs)).collect::<Vec<_>>()
+        );
+        let joined: String = parts.iter().flat_map(|p| &p.runs).map(|r| r.text.as_str()).collect();
+        assert_eq!(joined, long, "no character lost or duplicated");
+        // [`continued`] reads the same marks from the frames' text.
+        assert_eq!(continued(&filled(&[&a, &b, &c], &parts).iter().collect::<Vec<_>>()), [false, true, true]);
+        let lays: Vec<_> = [&a, &b, &c].iter().zip(&parts).map(|(f, p)| laid(db, f, p)).collect();
+        // The first frame: the first line at the first-line indent, after the bullet.
+        assert_eq!(lays[0].markers.len(), list, "{left}");
+        assert!((line_start(&lays[0], 0) - (if list > 0 { left } else { first })).abs() < 1e-6, "{}", line_start(&lays[0], 0));
+        if list > 0 {
+            assert!(lays[0].glyphs[lays[0].markers[0].glyphs.start].origin.x.abs() < 1e-6, "the bullet starts the first frame");
+        }
+        // The frames it continues into: every line at the left indent, no bullet.
+        for (k, (x0, lay)) in [200.0, 400.0].into_iter().zip(&lays[1..]).enumerate() {
+            let on_first = lay.markers.iter().filter(|m| lay.glyphs[m.glyphs.start].line == 0).count();
+            assert_eq!(on_first, 0, "frame {} starts without the bullet", k + 1);
+            assert!((line_start(lay, 0) - x0 - left).abs() < 1e-6, "frame {} starts at {}", k + 1, line_start(lay, 0) - x0);
+            assert!(!lay.overflow, "frame {} holds its share", k + 1);
+            for l in &lay.lines {
+                assert!(l.x1 <= x0 + 120.0 + 1e-6, "frame {}: a line ends at {}", k + 1, l.x1 - x0);
+            }
+        }
+        // The second paragraph, in the last frame, starts with its own first line.
+        let last = &lays[2];
+        let shown: String = parts[2].runs.iter().map(|r| r.text.as_str()).collect();
+        let second = last.lines.iter().position(|l| shown.get(l.start..).is_some_and(|s| s.starts_with("Second"))).unwrap();
+        assert!((line_start(last, second) - 400.0 - if list > 0 { left } else { first }).abs() < 1e-6, "{}", line_start(last, second));
+        assert_eq!(last.markers.len(), list, "the second paragraph's bullet");
+
+        // One-line paragraphs: the second frame starts with a paragraph of its own.
+        let lines = "Short line.\n".repeat(12);
+        let story = vec![TextRun { text: lines.clone(), style: CharStyle::default(), inline: None }];
+        let parts = distribute(db, &[&a, &b], &story, std::slice::from_ref(&para));
+        assert_eq!(parts.iter().map(|p| p.continues).collect::<Vec<_>>(), [false, false]);
+        let lay = laid(db, &b, &parts[1]);
+        assert!((line_start(&lay, 0) - 200.0 - if list > 0 { left } else { first }).abs() < 1e-6, "{}", line_start(&lay, 0));
+        if list > 0 {
+            assert_eq!(lay.glyphs[lay.markers[0].glyphs.start].line, 0, "the bullet starts the second frame");
+            assert!((lay.glyphs[lay.markers[0].glyphs.start].origin.x - 200.0).abs() < 1e-6);
+        }
+        assert_eq!(continued(&filled(&[&a, &b], &parts).iter().collect::<Vec<_>>()), [false, false]);
+    }
+}
+
+/// A frame that a paragraph continues into holds what fits it laid out that way: its share does
+/// not overflow it, and the share with the next word added does.
+#[test]
+fn a_continued_paragraph_fills_the_frame_it_continues_into() {
+    let db = FontDb::global();
+    let (a, b, mut c) = (frame(0.0), frame(200.0), frame(400.0));
+    c.kind = TextKind::Area { frame: shapes::rectangle(Rect::new(400.0, 0.0, 520.0, 300.0)) };
+    let hanging = ParaStyle { left_indent: 18.0, first_line_indent: -18.0, ..Default::default() };
+    let indented = ParaStyle { first_line_indent: 30.0, ..Default::default() };
+    let mut checked = 0;
+    for para in [hanging, indented] {
+        for k in 0..8 {
+            let text = "a ".repeat(k) + &"The quick brown fox jumps over the lazy dog. ".repeat(9);
+            let story = vec![TextRun { text, style: CharStyle::default(), inline: None }];
+            let parts = distribute(db, &[&a, &b, &c], &story, std::slice::from_ref(&para));
+            assert!(parts[1].continues, "{k}");
+            assert!(!laid(db, &b, &parts[1]).overflow, "the second frame holds its share ({k})");
+            let next: String = parts[2].runs.iter().map(|r| r.text.as_str()).collect();
+            let word = next.split_inclusive(' ').next().unwrap_or_default();
+            let mut more = parts[1].clone();
+            more.runs.push(TextRun { text: word.to_string(), style: CharStyle::default(), inline: None });
+            normalize(&mut more.runs);
+            assert!(laid(db, &b, &more).overflow, "the second frame has no room for {word:?} ({k})");
+            checked += 1;
+        }
+    }
+    assert_eq!(checked, 16);
+}
+
+/// `frames` holding the runs of `parts`, for [`continued`].
+fn filled(frames: &[&TextObject], parts: &[Slice]) -> Vec<TextObject> {
+    frames
+        .iter()
+        .zip(parts)
+        .map(|(f, p)| {
+            let mut t = (*f).clone();
+            t.runs = p.runs.clone();
+            t
+        })
+        .collect()
+}
+
+/// A paragraph that continues onto type on a path starts the path without its bullet.
+#[test]
+fn a_list_paragraph_continued_onto_a_path_has_no_bullet_there() {
+    use vectorcraft_doc::text::{Bullet, ParaList};
+    let db = FontDb::global();
+    let para = ParaStyle { left_indent: 18.0, first_line_indent: -18.0, list: Some(ParaList::bulleted(Bullet::Dot)), ..Default::default() };
+    let text = "The quick brown fox jumps over the lazy dog. ".repeat(6);
+    let story = vec![TextRun { text: text.clone(), style: CharStyle::default(), inline: None }];
+    let (a, b) = (frame(0.0), path_frame(300.0));
+    let parts = distribute(db, &[&a, &b], &story, std::slice::from_ref(&para));
+    assert_eq!(parts.iter().map(|p| p.continues).collect::<Vec<_>>(), [false, true]);
+    let (la, lb) = (laid(db, &a, &parts[0]), laid(db, &b, &parts[1]));
+    assert_eq!((la.markers.len(), lb.markers.len()), (1, 0));
+    // The same paragraph starting on the path has its bullet there.
+    let mut alone = b.clone();
+    alone.runs = story;
+    alone.set_paragraph_styles(vec![para]);
+    assert_eq!(layout(db, &alone).markers.len(), 1);
+}
+
+#[test]
+fn short_story_leaves_later_frames_empty_with_a_style() {
+    let db = FontDb::global();
+    let (a, b) = (frame(0.0), frame(200.0));
+    let st = CharStyle { size: 20.0, ..Default::default() };
+    let parts: Vec<Vec<TextRun>> =
+        distribute(db, &[&a, &b], &[TextRun { text: "Hi".into(), style: st, inline: None }], &[]).into_iter().map(|s| s.runs).collect();
+    assert_eq!(parts[0][0].text, "Hi");
+    assert_eq!((parts[1][0].text.as_str(), parts[1][0].style.size), ("", 20.0));
+}