pdf-inspector 1.22.0

//! Geometric underline detection.
//!
//! PDFs have no underline font flag — underlines are drawn as separate
//! graphics: stroked horizontal lines (`l`/`S` operators) or thin filled
//! rectangles (`re`/`f`). This pass correlates those graphics with text
//! items after extraction: an item is underlined when a horizontal
//! line/thin rect sits just below its baseline and covers most of its
//! horizontal extent.
//!
//! Repeated same-span rules are treated as table/form rulings rather than
//! underlines, which avoids marking every cell in ruled tables.

use std::collections::HashSet;

use crate::types::{ItemType, PdfRect, TextItem};

/// Max thickness (pt) for a stroked line / filled rect to count as an
/// underline rule rather than a border or decorative band.
const MAX_RULE_THICKNESS: f32 = 2.0;

/// Fraction of the item's width that the rule must cover horizontally.
const MIN_X_OVERLAP: f32 = 0.6;

/// Same-span rules repeated at this many y-levels are usually table/form
/// rulings, not semantic underlines.
const MIN_REPEATED_RULE_LEVELS: usize = 3;

/// Vertical tolerance for considering two rules to be on the same row edge.
const RULE_Y_DEDUP_EPS: f32 = 2.0;

/// Horizontal span similarity required when clustering repeated rulings.
const RULE_SPAN_OVERLAP_RATIO: f32 = 0.8;
const RULE_SPAN_WIDTH_RATIO: f32 = 1.5;

/// Multiple separated rule segments on one row are usually per-column table
/// header/body separators.
const MIN_SEGMENTED_ROW_RULES: usize = 3;
const MIN_SEGMENTED_ROW_GAPS: usize = 2;
const SEGMENTED_ROW_GAP_MIN: f32 = 12.0;

/// A single rule under several widely separated items is usually a table
/// header/body separator, not a sentence underline.
const MIN_TABULAR_RULE_ITEMS: usize = 3;
const MIN_TABULAR_RULE_GAPS: usize = 2;
const TABULAR_RULE_GAP_EM: f32 = 2.0;

/// Strikeout decorations are text-sized. Diagram connectors, signature
/// lines, and chart rules often cross glyphs too, but extend well beyond the
/// text they happen to intersect.
const STRIKE_OWNER_PAD_EM: f32 = 0.75;
const STRIKE_OWNER_MIN_PAD: f32 = 4.0;
const STRIKE_ROW_Y_TOLERANCE_EM: f32 = 0.15;
const STRIKE_ROW_Y_TOLERANCE_MIN: f32 = 5.0;
const GRAPHIC_CONNECTION_EPS: f32 = 2.0;
const GRAPHIC_CONNECTOR_MAX_THICKNESS: f32 = 4.0;

#[derive(Clone)]
pub(crate) struct UnderlineLine {
    pub(crate) x1: f32,
    pub(crate) y1: f32,
    pub(crate) x2: f32,
    pub(crate) y2: f32,
    pub(crate) stroke_width: f32,
    pub(crate) page: u32,
}

/// A horizontal rule candidate in page coordinates (PDF y-up).
#[derive(Clone)]
struct Rule {
    x1: f32,
    x2: f32,
    y: f32,
}

impl Rule {
    fn width(&self) -> f32 {
        self.x2 - self.x1
    }
}

fn rules_from_graphics(rects: &[PdfRect], lines: &[UnderlineLine], page: u32) -> Vec<Rule> {
    let mut rules: Vec<Rule> = Vec::new();
    for l in lines {
        if l.page != page {
            continue;
        }
        // Horizontal stroked line (tolerate slight skew).
        if l.stroke_width <= MAX_RULE_THICKNESS && (l.y1 - l.y2).abs() <= MAX_RULE_THICKNESS {
            let (x1, x2) = if l.x1 <= l.x2 {
                (l.x1, l.x2)
            } else {
                (l.x2, l.x1)
            };
            if x2 - x1 > 1.0 {
                rules.push(Rule {
                    x1,
                    x2,
                    y: (l.y1 + l.y2) / 2.0,
                });
            }
        }
    }
    for r in rects {
        if r.page != page {
            continue;
        }
        // Thin filled rect used as an underline rule. Extents are
        // normalized first: `re` operands pass through the CTM, so
        // width/height can be negative (flipped axes / negative scale) —
        // without normalization negative-width rules are missed and
        // negative-height bands sneak past the thickness check.
        let (x1, x2) = if r.width >= 0.0 {
            (r.x, r.x + r.width)
        } else {
            (r.x + r.width, r.x)
        };
        if r.height.abs() <= MAX_RULE_THICKNESS && x2 - x1 > 1.0 {
            rules.push(Rule {
                x1,
                x2,
                y: r.y + r.height / 2.0,
            });
        }
    }
    rules
}

fn discard_repeated_ruling_rules(
    rules: Vec<Rule>,
    items: &[TextItem],
    rects: &[PdfRect],
    lines: &[UnderlineLine],
    page: u32,
) -> Vec<Rule> {
    if rules.len() < MIN_REPEATED_RULE_LEVELS {
        return rules;
    }

    rules
        .iter()
        .filter(|rule| {
            // A rule snugly owned by one text line is an underline even when
            // span-similar rules repeat down the page — documents that
            // underline many full-width lines (dense CJK business docs) look
            // exactly like table rulings to the repetition check, which used
            // to discard every one of them. Table rulings fail snugness:
            // row separators extend past their cells' text (or have no text
            // on the baseline above), and multi-column matches are still
            // culled by the tabular filter afterwards.
            // Same-row segmented rules (column-header separators) are
            // always rulings — each segment snugly owns its column label,
            // so snugness must not override that check.
            !is_segmented_row_ruling_rule(rule, &rules)
                && ((has_snug_text_owner(rule, items)
                    && !has_flanking_verticals(rule, rects, lines, page))
                    || !is_repeated_ruling_rule(rule, &rules))
        })
        .cloned()
        .collect()
}

/// True when a single text item both matches the rule vertically (baseline
/// window) and horizontally contains it: the rule may not extend past the
/// item's span by more than ~0.75em on either side. Underlines are drawn to
/// the width of the text they decorate; table/form rulings span cells or
/// full table width and overshoot any single item.
/// A rule flanked by vertical strokes at its ends is a table/box border
/// row edge, not an underline — underlined text lines have no vertical
/// rules rising from their ends. Checked against raw stroked lines: a
/// near-vertical segment whose x sits at either end of the rule and whose
/// y-range covers the rule's row.
fn has_flanking_verticals(
    rule: &Rule,
    rects: &[PdfRect],
    lines: &[UnderlineLine],
    page: u32,
) -> bool {
    // A drawn rect that CONTAINS the rule vetoes rescue only with GRID
    // EVIDENCE: another drawn rect abutting it vertically (cell rows tile).
    // Height alone can't separate a table cell from a decorative callout
    // panel — genuine underlines live inside isolated filled panels, and
    // multiline table cells can be arbitrarily tall.
    let norm = |r: &PdfRect| {
        let (x_lo, x_hi) = if r.width >= 0.0 {
            (r.x, r.x + r.width)
        } else {
            (r.x + r.width, r.x)
        };
        let (y_lo, y_hi) = if r.height >= 0.0 {
            (r.y, r.y + r.height)
        } else {
            (r.y + r.height, r.y)
        };
        (x_lo, x_hi, y_lo, y_hi)
    };
    let page_rects: Vec<(f32, f32, f32, f32)> = rects
        .iter()
        .filter(|r| r.page == page && r.height.abs() > 6.0)
        .map(norm)
        .collect();
    let rect_flank = page_rects.iter().any(|&(x_lo, x_hi, y_lo, y_hi)| {
        let contains = x_lo <= rule.x1 + 2.0
            && x_hi >= rule.x2 - 2.0
            && y_lo <= rule.y + 2.0
            && y_hi >= rule.y - 2.0;
        if !contains {
            return false;
        }
        // Grid evidence: a vertically abutting neighbor box with x-overlap.
        page_rects.iter().any(|&(nx_lo, nx_hi, ny_lo, ny_hi)| {
            let x_overlap = nx_hi.min(x_hi) - nx_lo.max(x_lo);
            if x_overlap <= 10.0 {
                return false;
            }
            (ny_lo - y_hi).abs() <= 3.0 || (y_lo - ny_hi).abs() <= 3.0
        })
    });
    if rect_flank {
        return true;
    }
    lines.iter().any(|l| {
        if l.page != page || (l.x1 - l.x2).abs() > 2.0 {
            return false;
        }
        let x = (l.x1 + l.x2) / 2.0;
        let near_end = (x - rule.x1).abs() <= 6.0 || (x - rule.x2).abs() <= 6.0;
        if !near_end {
            return false;
        }
        let (y_lo, y_hi) = if l.y1 <= l.y2 {
            (l.y1, l.y2)
        } else {
            (l.y2, l.y1)
        };
        y_lo <= rule.y + 2.0 && y_hi >= rule.y - 2.0
    })
}

fn has_snug_text_owner(rule: &Rule, items: &[TextItem]) -> bool {
    // Underlines are drawn to the width of the text they decorate, but the
    // text may be split into several runs (CJK lines mix scripts and font
    // switches) — so ownership is judged against the UNION of the runs on
    // the rule's baseline row. Table/form rulings overshoot their row's
    // text (row separators span cell padding and empty columns), so they
    // fail either containment or coverage.
    let matched: Vec<&TextItem> = items
        .iter()
        .filter(|item| is_underline_candidate(item) && rule_matches_item(rule, item))
        .collect();
    if matched.is_empty() {
        return false;
    }
    let x1 = matched.iter().map(|i| i.x).fold(f32::INFINITY, f32::min);
    let x2 = matched
        .iter()
        .map(|i| i.x + i.width)
        .fold(f32::NEG_INFINITY, f32::max);
    let max_fs = matched.iter().map(|i| i.font_size).fold(0.0, f32::max);
    let pad = (max_fs * 0.75).max(4.0);
    if rule.x1 < x1 - pad || rule.x2 > x2 + pad {
        return false;
    }
    let covered: f32 = matched.iter().map(|i| i.width).sum();
    if covered < rule.width() * 0.6 {
        return false;
    }
    // A table row also unions to the rule's span — but its cells sit apart.
    // An underlined text line is contiguous runs with word-sized gaps; any
    // column-sized hole between matched runs means this is a row ruling.
    let mut sorted = matched;
    sorted.sort_by(|a, b| a.x.total_cmp(&b.x));
    sorted.windows(2).all(|pair| {
        let gap = pair[1].x - (pair[0].x + pair[0].width);
        gap <= (max_fs * 2.0).max(12.0)
    })
}

fn is_repeated_ruling_rule(rule: &Rule, rules: &[Rule]) -> bool {
    let mut y_levels: Vec<f32> = rules
        .iter()
        .filter(|other| has_similar_span(rule, other))
        .map(|other| other.y)
        .collect();

    y_levels.sort_by(|a, b| a.total_cmp(b));
    y_levels.dedup_by(|a, b| (*a - *b).abs() <= RULE_Y_DEDUP_EPS);
    y_levels.len() >= MIN_REPEATED_RULE_LEVELS
}

fn is_segmented_row_ruling_rule(rule: &Rule, rules: &[Rule]) -> bool {
    let mut row_rules: Vec<&Rule> = rules
        .iter()
        .filter(|other| (other.y - rule.y).abs() <= RULE_Y_DEDUP_EPS)
        .collect();

    if row_rules.len() < MIN_SEGMENTED_ROW_RULES {
        return false;
    }

    row_rules.sort_by(|a, b| a.x1.total_cmp(&b.x1));
    let large_gaps = row_rules
        .windows(2)
        .filter(|pair| pair[1].x1 - pair[0].x2 > SEGMENTED_ROW_GAP_MIN)
        .count();

    large_gaps >= MIN_SEGMENTED_ROW_GAPS
}

fn has_similar_span(a: &Rule, b: &Rule) -> bool {
    let a_width = a.width();
    let b_width = b.width();
    if a_width <= 1.0 || b_width <= 1.0 {
        return false;
    }

    let width_ratio = a_width.max(b_width) / a_width.min(b_width);
    if width_ratio > RULE_SPAN_WIDTH_RATIO {
        return false;
    }

    let overlap = a.x2.min(b.x2) - a.x1.max(b.x1);
    overlap >= a_width.min(b_width) * RULE_SPAN_OVERLAP_RATIO
}

fn tabular_row_separator_rule_indices(rules: &[Rule], items: &[TextItem]) -> HashSet<usize> {
    let mut tabular_rules = HashSet::new();

    for (rule_idx, rule) in rules.iter().enumerate() {
        let mut matched_items: Vec<&TextItem> = items
            .iter()
            .filter(|item| is_underline_candidate(item) && rule_matches_item(rule, item))
            .collect();

        if matched_items.len() < MIN_TABULAR_RULE_ITEMS {
            continue;
        }

        matched_items.sort_by(|a, b| a.x.total_cmp(&b.x));
        let large_gaps = matched_items
            .windows(2)
            .filter(|pair| {
                let left = pair[0];
                let right = pair[1];
                let gap = right.x - (left.x + left.width);
                let font_size = left.font_size.max(right.font_size).max(1.0);
                gap > font_size * TABULAR_RULE_GAP_EM
            })
            .count();

        if large_gaps >= MIN_TABULAR_RULE_GAPS {
            tabular_rules.insert(rule_idx);
        }
    }

    tabular_rules
}

fn is_underline_candidate(item: &TextItem) -> bool {
    // Rule geometry below assumes a horizontal baseline: a vertical run's
    // box bottom is a run end, not a baseline, and a table border under a
    // rotated header would otherwise read as an underline. Level runs qualify
    // — upright or upside-down, within a scan's few degrees of skew — and
    // `baseline_and_up` tells the windows where each one's baseline is and
    // which way its glyphs rise; an oblique callout has no horizontal rule.
    // An estimated box (font without widths) says nothing about where the
    // glyphs end, so it cannot own a rule either — as when it was zero-width.
    matches!(item.item_type, ItemType::Text)
        && !item.text.trim().is_empty()
        && item.width > 0.0
        && item.advance_known
        && has_level_baseline(item)
}

/// Decoration rules are horizontal, so only a run whose baseline is level
/// can own one: upright or upside-down, allowing the few degrees of skew a
/// scanned page's text layer carries.
fn has_level_baseline(item: &TextItem) -> bool {
    const SKEW_TOLERANCE_DEG: f32 = 5.0;
    let r = item.rotation;
    r <= SKEW_TOLERANCE_DEG
        || r >= 360.0 - SKEW_TOLERANCE_DEG
        || (r - 180.0).abs() <= SKEW_TOLERANCE_DEG
}

/// Baseline of a horizontal run and the page-y direction its glyphs rise
/// in: an upright run sits on `y` and rises towards +y; a 180° run hangs
/// from its box top, `y + height`, and rises towards -y.
fn baseline_and_up(item: &TextItem) -> (f32, f32) {
    if item.is_upside_down() {
        (item.y + item.height, -1.0)
    } else {
        (item.y, 1.0)
    }
}

/// True when `rule_y` lies between `lo` and `hi` points from the item's
/// baseline, measured in the direction its glyphs rise — so a negative
/// offset is on the far side of the baseline from the glyphs, whichever
/// way they face.
fn rule_in_glyph_band(rule_y: f32, item: &TextItem, lo: f32, hi: f32) -> bool {
    let (base, up) = baseline_and_up(item);
    let a = base + up * lo;
    let b = base + up * hi;
    rule_y >= a.min(b) && rule_y <= a.max(b)
}

fn rule_matches_item(rule: &Rule, item: &TextItem) -> bool {
    // Vertical window: underlines sit at or slightly below the baseline.
    // Latin fonts draw them at roughly 5-15% of the em below; CJK layouts
    // put them under the full em box, measured up to ~0.67em below the
    // baseline (text_dense__underline). Allow 0.72em (min 3pt) below and
    // 1pt above for rounding.
    let below = (item.font_size * 0.72).max(3.0);
    if !rule_in_glyph_band(rule.y, item, -below, 1.0) {
        return false;
    }

    let ix1 = item.x;
    let ix2 = item.x + item.width;
    let min_overlap = item.width * MIN_X_OVERLAP;
    let overlap = rule.x2.min(ix2) - rule.x1.max(ix1);
    overlap >= min_overlap
}

/// Strikeout window: a rule crossing the glyphs. Strikethroughs sit at
/// roughly 20-35% of the em above the baseline (about half the x-height);
/// accept a band well inside the glyph body so baseline underlines and
/// overlines never qualify.
fn rule_strikes_item(rule: &Rule, item: &TextItem) -> bool {
    if !rule_in_glyph_band(rule.y, item, item.font_size * 0.12, item.font_size * 0.55) {
        return false;
    }

    let ix1 = item.x;
    let ix2 = item.x + item.width;
    let min_overlap = item.width * MIN_X_OVERLAP;
    let overlap = rule.x2.min(ix2) - rule.x1.max(ix1);
    overlap >= min_overlap
}

fn is_bare_list_marker(text: &str) -> bool {
    matches!(
        text.trim(),
        "•" | "◦" | "▪" | "▫" | "‣" | "⁃" | "●" | "○" | "■" | "□" | "-" | "*"
    )
}

fn same_strike_row(left: &TextItem, right: &TextItem) -> bool {
    let font_size = left.font_size.max(right.font_size);
    let tolerance = (font_size * STRIKE_ROW_Y_TOLERANCE_EM).max(STRIKE_ROW_Y_TOLERANCE_MIN);
    // Same orientation, compared at the baseline: 180° fragments of different
    // sizes hang from one baseline while their box bottoms differ.
    left.is_upside_down() == right.is_upside_down()
        && (baseline_and_up(left).0 - baseline_and_up(right).0).abs() <= tolerance
}

fn is_inline_script(rule: &Rule, candidate: &TextItem, parent: &TextItem) -> bool {
    // Script attachment reads left-to-right from an upright parent; a 180°
    // run's scripts would trail to its left, which the row walk below does
    // not model, so only upright pairs are joined.
    if !candidate.is_upright()
        || !parent.is_upright()
        || !is_underline_candidate(candidate)
        || is_bare_list_marker(&candidate.text)
        || candidate.font_size <= 0.0
        || candidate.font_size >= parent.font_size * 0.75
        || candidate.text.len() > 4
        || !candidate.text.chars().all(|c| c.is_ascii_digit())
        || (candidate.y - parent.y).abs() > 5.0
    {
        return false;
    }

    let parent_ends_with_letter = parent.text.chars().last().is_some_and(char::is_alphabetic);
    if !parent_ends_with_letter {
        return false;
    }

    let parent_right = parent.x + parent.width;
    let gap = candidate.x - parent_right;
    if gap >= parent.font_size * 0.2 || gap <= -parent.font_size * 0.3 {
        return false;
    }

    let overlap = rule.x2.min(candidate.x + candidate.width) - rule.x1.max(candidate.x);
    overlap >= candidate.width * MIN_X_OVERLAP
}

/// Return the items owned by a snug mid-glyph rule.
///
/// Real strikeout decorations track the width of the deleted text, including
/// runs split by font/style changes and adjacent numeric super/subscripts.
/// Non-text graphics can cross the same vertical window, but arrow shafts,
/// signature lines, fraction bars, and chart rules extend materially beyond
/// the intersected glyphs. Requiring the rule to stay within a small em-sized
/// pad of a contiguous matched row separates those cases without relying on
/// document-specific fonts or coordinates.
///
/// Ownership is computed once per rule. This keeps the strikeout pass at the
/// same rule-by-item scale as underline detection instead of rescanning the
/// whole page for every matching item.
fn snug_strike_owner_indices(rule: &Rule, items: &[TextItem]) -> Vec<usize> {
    let mut struck_indices: Vec<usize> = items
        .iter()
        .enumerate()
        .filter_map(|(index, candidate)| {
            (is_underline_candidate(candidate)
                && !is_bare_list_marker(&candidate.text)
                && rule_strikes_item(rule, candidate))
            .then_some(index)
        })
        .collect();
    if struck_indices.is_empty() {
        return Vec::new();
    }
    struck_indices.sort_by(|&left, &right| {
        baseline_and_up(&items[left])
            .0
            .total_cmp(&baseline_and_up(&items[right]).0)
    });

    let mut rows: Vec<Vec<usize>> = Vec::new();
    for index in struck_indices {
        if let Some(row) = rows
            .last_mut()
            .filter(|row| same_strike_row(&items[row[0]], &items[index]))
        {
            row.push(index);
        } else {
            rows.push(vec![index]);
        }
    }

    let mut owned_indices = Vec::new();
    for mut row in rows {
        row.sort_by(|&left, &right| items[left].x.total_cmp(&items[right].x));

        // Underline detection runs before the extractor's script-merging
        // pass. Include the same tightly adjacent numeric script shape here
        // when the rule spans it, so the owner width and semantic mark both
        // survive that later merge.
        let scripts: Vec<usize> = items
            .iter()
            .enumerate()
            .filter_map(|(index, candidate)| {
                let parent_pos =
                    row.partition_point(|&row_index| items[row_index].x <= candidate.x);
                let parent_index = parent_pos.checked_sub(1).map(|pos| row[pos])?;
                is_inline_script(rule, candidate, &items[parent_index]).then_some(index)
            })
            .collect();
        row.extend(scripts);
        row.sort_by(|&left, &right| items[left].x.total_cmp(&items[right].x));
        row.dedup();

        let x1 = row
            .iter()
            .map(|&index| items[index].x)
            .fold(f32::INFINITY, f32::min);
        let x2 = row
            .iter()
            .map(|&index| items[index].x + items[index].width)
            .fold(f32::NEG_INFINITY, f32::max);
        let max_font_size = row
            .iter()
            .map(|&index| items[index].font_size)
            .fold(0.0, f32::max);
        let pad = (max_font_size * STRIKE_OWNER_PAD_EM).max(STRIKE_OWNER_MIN_PAD);

        if rule.x1 < x1 - pad || rule.x2 > x2 + pad {
            continue;
        }

        let contiguous = row.windows(2).all(|pair| {
            let gap = items[pair[1]].x - (items[pair[0]].x + items[pair[0]].width);
            gap <= (max_font_size * 2.0).max(12.0)
        });
        if contiguous {
            owned_indices.extend(row);
        }
    }

    owned_indices.sort_unstable();
    owned_indices.dedup();
    owned_indices
}

/// Diagram and table rules participate in larger path geometry. A vertical
/// or diagonal segment meeting the candidate rule is strong evidence that
/// the horizontal segment is a connector, border, arrow, or symbol rather
/// than an isolated text decoration.
fn has_connected_nonhorizontal_segment(rule: &Rule, lines: &[UnderlineLine], page: u32) -> bool {
    lines.iter().any(|line| {
        if line.page != page {
            return false;
        }

        let dx = line.x2 - line.x1;
        let dy = line.y2 - line.y1;
        if dy.abs() <= MAX_RULE_THICKNESS {
            return false;
        }

        let y_min = line.y1.min(line.y2) - GRAPHIC_CONNECTION_EPS;
        let y_max = line.y1.max(line.y2) + GRAPHIC_CONNECTION_EPS;
        if rule.y < y_min || rule.y > y_max {
            return false;
        }

        let t = (rule.y - line.y1) / dy;
        if !(-0.05..=1.05).contains(&t) {
            return false;
        }
        let intersection_x = line.x1 + t * dx;
        intersection_x >= rule.x1 - GRAPHIC_CONNECTION_EPS
            && intersection_x <= rule.x2 + GRAPHIC_CONNECTION_EPS
    })
}

/// Filled diagrams often build connectors from intersecting thin rectangles
/// instead of stroked path segments. Treat only narrow, vertically elongated
/// rectangles as connector geometry; broad fills can legitimately sit behind
/// struck text and must not veto its decoration.
fn has_connected_nonhorizontal_rect(rule: &Rule, rects: &[PdfRect], page: u32) -> bool {
    rects.iter().any(|rect| {
        if rect.page != page {
            return false;
        }

        let (x1, x2) = if rect.width >= 0.0 {
            (rect.x, rect.x + rect.width)
        } else {
            (rect.x + rect.width, rect.x)
        };
        let (y1, y2) = if rect.height >= 0.0 {
            (rect.y, rect.y + rect.height)
        } else {
            (rect.y + rect.height, rect.y)
        };
        let width = x2 - x1;
        let height = y2 - y1;

        width > 0.0
            && width <= GRAPHIC_CONNECTOR_MAX_THICKNESS
            && height > width * 2.0
            && rule.y >= y1 - GRAPHIC_CONNECTION_EPS
            && rule.y <= y2 + GRAPHIC_CONNECTION_EPS
            && x2 >= rule.x1 - GRAPHIC_CONNECTION_EPS
            && x1 <= rule.x2 + GRAPHIC_CONNECTION_EPS
    })
}

/// Mark `is_underline` on text items that have a horizontal rule just
/// below their baseline, and `is_strikeout` on items whose glyphs a rule
/// crosses at mid x-height. `items`, `rects`, and `lines` are a single
/// page's extraction output (all in PDF coordinates, y-up, where
/// `TextItem::y` is the text baseline of an upright run; a 180° run hangs
/// from `y + height`).
pub(crate) fn mark_underlined_items(
    items: &mut [TextItem],
    rects: &[PdfRect],
    lines: &[UnderlineLine],
    page: u32,
) {
    let rules = discard_repeated_ruling_rules(
        rules_from_graphics(rects, lines, page),
        items,
        rects,
        lines,
        page,
    );
    if rules.is_empty() {
        return;
    }
    let tabular_rules = tabular_row_separator_rule_indices(&rules, items);

    // Math fraction bars are short horizontal lines with the numerator just
    // above AND the denominator just below — underline geometry from above,
    // but no underline has text hanging directly beneath it at fraction
    // distance. Only narrow rules qualify: real underlines under short
    // labels have their next text line a full line-pitch away.
    let fraction_rules: HashSet<usize> = rules
        .iter()
        .enumerate()
        .filter(|(_, rule)| {
            rule.width() <= 60.0
                && items.iter().any(|item| {
                    // Denominator geometry is upright-only: it hangs below
                    // the bar with its glyph tops at `y + height`.
                    if !is_underline_candidate(item) || !item.is_upright() {
                        return false;
                    }
                    // A denominator HUGS the bar (fraction typesetting
                    // leaves ~0.1-0.2em) and is bar-sized. Both bounds
                    // matter: a short last-line of a paragraph at normal
                    // leading sits further below, and a full next text
                    // line is far wider than the rule.
                    let dy = rule.y - (item.y + item.height);
                    let overlap = rule.x2.min(item.x + item.width) - rule.x1.max(item.x);
                    dy > 0.0
                        && dy <= item.font_size * 0.3
                        && overlap > rule.width() * 0.5
                        && item.width <= rule.width() * 1.5
                })
        })
        .map(|(i, _)| i)
        .collect();

    let mut strikeout_items = vec![false; items.len()];
    for (rule_idx, rule) in rules.iter().enumerate() {
        if tabular_rules.contains(&rule_idx)
            || has_connected_nonhorizontal_segment(rule, lines, page)
            || has_connected_nonhorizontal_rect(rule, rects, page)
        {
            continue;
        }
        for item_idx in snug_strike_owner_indices(rule, items) {
            strikeout_items[item_idx] = true;
        }
    }

    let underlined_items: HashSet<usize> = items
        .iter()
        .enumerate()
        .filter(|(_, item)| {
            is_underline_candidate(item)
                && rules.iter().enumerate().any(|(rule_idx, rule)| {
                    !tabular_rules.contains(&rule_idx)
                        && !fraction_rules.contains(&rule_idx)
                        && rule_matches_item(rule, item)
                })
        })
        .map(|(item_idx, _)| item_idx)
        .collect();

    for (item_idx, item) in items.iter_mut().enumerate() {
        if !is_underline_candidate(item) {
            continue;
        }

        if strikeout_items[item_idx] {
            item.is_strikeout = true;
        }
        if underlined_items.contains(&item_idx) {
            item.is_underline = true;
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::types::ItemType;

    fn item(text: &str, x: f32, y: f32, width: f32, font_size: f32) -> TextItem {
        TextItem {
            text: text.to_string(),
            x,
            y,
            width,
            height: font_size,
            font: "F1".to_string(),
            font_tag: String::new(),
            legacy_symbol_rewrite: false,
            font_size,
            page: 1,
            is_bold: false,
            is_italic: false,
            font_weight: None,
            bold_source: None,
            fixed_pitch: None,
            is_underline: false,
            is_strikeout: false,
            rotation: 0.0,
            advance_known: true,
            item_type: ItemType::Text,
            mcid: None,
            baseline_shift: 0.0,
        }
    }

    fn hline(x1: f32, x2: f32, y: f32) -> UnderlineLine {
        UnderlineLine {
            x1,
            y1: y,
            x2,
            y2: y,
            stroke_width: 1.0,
            page: 1,
        }
    }

    fn cell_rect(x: f32, y: f32, width: f32, height: f32) -> PdfRect {
        PdfRect {
            x,
            y,
            width,
            height,
            page: 1,
        }
    }

    fn thin_rect(x: f32, y: f32, width: f32) -> PdfRect {
        PdfRect {
            x,
            y,
            width,
            height: 0.8,
            page: 1,
        }
    }

    #[test]
    fn stroked_line_under_baseline_marks_underline() {
        let mut items = vec![item("underlined", 100.0, 500.0, 60.0, 10.0)];
        let lines = vec![hline(99.0, 161.0, 498.5)];
        mark_underlined_items(&mut items, &[], &lines, 1);
        assert!(items[0].is_underline);
    }

    #[test]
    fn thin_filled_rect_under_baseline_marks_underline() {
        let mut items = vec![item("underlined", 100.0, 500.0, 60.0, 10.0)];
        let rects = vec![thin_rect(100.0, 497.8, 60.0)];
        mark_underlined_items(&mut items, &rects, &[], 1);
        assert!(items[0].is_underline);
    }

    #[test]
    fn long_rule_under_multiple_items_marks_each() {
        // One underline drawn under a whole sentence: every overlapped
        // item gets the flag.
        let mut items = vec![
            item("first", 100.0, 500.0, 40.0, 10.0),
            item("second", 145.0, 500.0, 50.0, 10.0),
        ];
        let lines = vec![hline(98.0, 200.0, 498.0)];
        mark_underlined_items(&mut items, &[], &lines, 1);
        assert!(items[0].is_underline);
        assert!(items[1].is_underline);
    }

    #[test]
    fn line_far_below_baseline_is_not_an_underline() {
        // A horizontal rule 30pt below (section divider) must not mark.
        let mut items = vec![item("text", 100.0, 500.0, 60.0, 10.0)];
        let lines = vec![hline(90.0, 300.0, 470.0)];
        mark_underlined_items(&mut items, &[], &lines, 1);
        assert!(!items[0].is_underline);
    }

    #[test]
    fn thick_stroked_line_is_not_an_underline() {
        let mut items = vec![item("text", 100.0, 500.0, 60.0, 10.0)];
        let mut line = hline(99.0, 161.0, 498.5);
        line.stroke_width = 4.0;

        mark_underlined_items(&mut items, &[], &[line], 1);

        assert!(!items[0].is_underline);
    }

    #[test]
    fn mid_glyph_rule_marks_strikeout_not_underline() {
        // Rule at ~30% of the em above the baseline crosses the glyphs.
        let mut items = vec![item("struck out", 100.0, 500.0, 60.0, 10.0)];
        let lines = vec![hline(99.0, 161.0, 503.0)];
        mark_underlined_items(&mut items, &[], &lines, 1);
        assert!(items[0].is_strikeout);
        assert!(!items[0].is_underline);
    }

    #[test]
    fn long_connector_crossing_text_is_not_a_strikeout() {
        let mut items = vec![item("diagram label", 160.0, 500.0, 60.0, 10.0)];
        let lines = vec![hline(100.0, 280.0, 503.0)];

        mark_underlined_items(&mut items, &[], &lines, 1);

        assert!(!items[0].is_strikeout);
    }

    #[test]
    fn chart_rule_ending_inside_short_label_is_not_a_strikeout() {
        let mut items = vec![item("T 18", 300.0, 500.0, 20.0, 10.0)];
        let lines = vec![hline(100.0, 315.0, 503.0)];

        mark_underlined_items(&mut items, &[], &lines, 1);

        assert!(!items[0].is_strikeout);
    }

    #[test]
    fn connected_diagram_segment_is_not_a_strikeout() {
        let mut items = vec![item("V8", 100.0, 500.0, 12.0, 10.0)];
        let lines = vec![
            hline(99.0, 113.0, 503.0),
            UnderlineLine {
                x1: 106.0,
                y1: 496.0,
                x2: 109.0,
                y2: 510.0,
                stroke_width: 1.0,
                page: 1,
            },
        ];

        mark_underlined_items(&mut items, &[], &lines, 1);

        assert!(!items[0].is_strikeout);
    }

    #[test]
    fn connected_filled_rect_is_not_a_strikeout() {
        let mut items = vec![item("V8", 100.0, 500.0, 12.0, 10.0)];
        let rects = vec![
            thin_rect(99.0, 502.6, 14.0),
            PdfRect {
                x: 106.0,
                y: 496.0,
                width: 2.0,
                height: 14.0,
                page: 1,
            },
        ];

        mark_underlined_items(&mut items, &rects, &[], 1);

        assert!(!items[0].is_strikeout);
    }

    #[test]
    fn broad_fill_behind_text_does_not_block_strikeout() {
        let mut items = vec![item("deleted", 100.0, 500.0, 40.0, 10.0)];
        let rects = vec![
            thin_rect(99.0, 502.6, 42.0),
            PdfRect {
                x: 90.0,
                y: 490.0,
                width: 100.0,
                height: 20.0,
                page: 1,
            },
        ];

        mark_underlined_items(&mut items, &rects, &[], 1);

        assert!(items[0].is_strikeout);
    }

    #[test]
    fn list_bullet_is_not_a_strikeout() {
        for marker in ["•", "-", "*"] {
            let mut items = vec![item(marker, 100.0, 500.0, 6.0, 10.0)];
            let lines = vec![hline(99.0, 107.0, 503.0)];

            mark_underlined_items(&mut items, &[], &lines, 1);

            assert!(!items[0].is_strikeout, "marker {marker:?}");
        }
    }

    #[test]
    fn snug_rule_marks_adjacent_split_runs_as_strikeout() {
        let mut items = vec![
            item("deleted", 100.0, 500.0, 40.0, 10.0),
            item("text", 142.0, 500.0, 25.0, 10.0),
        ];
        let lines = vec![hline(99.0, 168.0, 503.0)];

        mark_underlined_items(&mut items, &[], &lines, 1);

        assert!(items.iter().all(|item| item.is_strikeout));
    }

    #[test]
    fn snug_rule_groups_split_runs_with_baseline_drift() {
        let mut items = vec![
            item("deleted", 100.0, 500.0, 40.0, 10.0),
            item("text", 142.0, 498.0, 25.0, 10.0),
        ];
        let lines = vec![hline(99.0, 168.0, 503.0)];

        mark_underlined_items(&mut items, &[], &lines, 1);

        assert!(items.iter().all(|item| item.is_strikeout));
    }

    #[test]
    fn snug_rule_keeps_inline_superscript_in_strike_owner() {
        let mut items = vec![
            item("deleted", 100.0, 500.0, 40.0, 10.0),
            item("2", 140.5, 503.0, 4.0, 6.0),
        ];
        let lines = vec![hline(99.0, 145.0, 503.0)];

        mark_underlined_items(&mut items, &[], &lines, 1);

        assert!(items.iter().all(|item| item.is_strikeout));
    }

    #[test]
    fn snug_rule_keeps_inline_subscript_in_strike_owner() {
        let mut items = vec![
            item("deleted", 100.0, 500.0, 40.0, 10.0),
            item("2", 140.5, 497.0, 4.0, 6.0),
        ];
        let lines = vec![hline(99.0, 145.0, 503.0)];

        mark_underlined_items(&mut items, &[], &lines, 1);

        assert!(items.iter().all(|item| item.is_strikeout));
    }

    #[test]
    fn baseline_rule_marks_underline_not_strikeout() {
        let mut items = vec![item("underlined", 100.0, 500.0, 60.0, 10.0)];
        let lines = vec![hline(99.0, 161.0, 498.5)];
        mark_underlined_items(&mut items, &[], &lines, 1);
        assert!(items[0].is_underline);
        assert!(!items[0].is_strikeout);
    }

    #[test]
    fn overline_is_neither_underline_nor_strikeout() {
        // Rule just above the cap height (overline / next line's rule).
        let mut items = vec![item("text", 100.0, 500.0, 60.0, 10.0)];
        let lines = vec![hline(99.0, 161.0, 507.0)];
        mark_underlined_items(&mut items, &[], &lines, 1);
        assert!(!items[0].is_underline);
        assert!(!items[0].is_strikeout);
    }

    #[test]
    fn thin_filled_rect_at_mid_glyph_marks_strikeout() {
        let mut items = vec![item("struck out", 100.0, 500.0, 60.0, 10.0)];
        let rects = vec![thin_rect(100.0, 502.6, 60.0)];
        mark_underlined_items(&mut items, &rects, &[], 1);
        assert!(items[0].is_strikeout);
        assert!(!items[0].is_underline);
    }

    #[test]
    fn line_above_baseline_is_not_an_underline() {
        // Strikethrough / overline geometry must not mark.
        let mut items = vec![item("text", 100.0, 500.0, 60.0, 10.0)];
        let lines = vec![hline(90.0, 300.0, 505.0)];
        mark_underlined_items(&mut items, &[], &lines, 1);
        assert!(!items[0].is_underline);
    }

    #[test]
    fn insufficient_horizontal_overlap_is_not_an_underline() {
        // Rule under only a quarter of the item (e.g. neighboring cell
        // border) must not mark.
        let mut items = vec![item("wide text item", 100.0, 500.0, 100.0, 10.0)];
        let lines = vec![hline(100.0, 125.0, 498.5)];
        mark_underlined_items(&mut items, &[], &lines, 1);
        assert!(!items[0].is_underline);
    }

    #[test]
    fn negative_width_rect_is_normalized_and_marks_underline() {
        // A CTM with negative x-scale (or negative `re` operands) produces
        // rects whose width is negative; the rule extents must normalize.
        let mut items = vec![item("underlined", 100.0, 500.0, 60.0, 10.0)];
        let rects = vec![PdfRect {
            x: 160.0,
            y: 497.8,
            width: -60.0,
            height: 0.8,
            page: 1,
        }];
        mark_underlined_items(&mut items, &rects, &[], 1);
        assert!(items[0].is_underline);
    }

    #[test]
    fn negative_height_band_is_not_an_underline() {
        // A 14pt band expressed with negative height must not pass the
        // thickness check via sign trickery.
        let mut items = vec![item("text", 100.0, 500.0, 60.0, 10.0)];
        let rects = vec![PdfRect {
            x: 95.0,
            y: 509.0,
            width: 80.0,
            height: -14.0,
            page: 1,
        }];
        mark_underlined_items(&mut items, &rects, &[], 1);
        assert!(!items[0].is_underline);
    }

    #[test]
    fn thick_band_is_not_an_underline() {
        // A highlight bar / filled cell background (tall rect) must not mark.
        let mut items = vec![item("text", 100.0, 500.0, 60.0, 10.0)];
        let rects = vec![PdfRect {
            x: 95.0,
            y: 495.0,
            width: 80.0,
            height: 14.0,
            page: 1,
        }];
        mark_underlined_items(&mut items, &rects, &[], 1);
        assert!(!items[0].is_underline);
    }

    #[test]
    fn vertical_line_is_not_an_underline() {
        let mut items = vec![item("text", 100.0, 500.0, 60.0, 10.0)];
        let lines = vec![UnderlineLine {
            x1: 120.0,
            y1: 498.0,
            x2: 120.0,
            y2: 400.0,
            stroke_width: 1.0,
            page: 1,
        }];
        mark_underlined_items(&mut items, &[], &lines, 1);
        assert!(!items[0].is_underline);
    }

    #[test]
    fn other_pages_graphics_do_not_mark() {
        let mut items = vec![item("text", 100.0, 500.0, 60.0, 10.0)];
        let mut line = hline(99.0, 161.0, 498.5);
        line.page = 2;
        mark_underlined_items(&mut items, &[], &[line], 1);
        assert!(!items[0].is_underline);
    }

    #[test]
    fn repeated_table_row_rules_do_not_mark_cell_text() {
        let mut items = vec![
            item("A", 110.0, 500.0, 20.0, 10.0),
            item("B", 110.0, 480.0, 20.0, 10.0),
            item("C", 110.0, 460.0, 20.0, 10.0),
        ];
        let lines = vec![
            hline(100.0, 150.0, 498.0),
            hline(100.0, 150.0, 478.0),
            hline(100.0, 150.0, 458.0),
        ];

        mark_underlined_items(&mut items, &[], &lines, 1);

        assert!(items.iter().all(|item| !item.is_underline));
    }

    #[test]
    fn row_separator_under_spaced_column_labels_is_not_an_underline() {
        let mut items = vec![
            item("Date", 100.0, 500.0, 25.0, 10.0),
            item("Rate", 200.0, 500.0, 25.0, 10.0),
            item("Yield", 300.0, 500.0, 30.0, 10.0),
        ];
        let lines = vec![hline(90.0, 340.0, 498.0)];

        mark_underlined_items(&mut items, &[], &lines, 1);

        assert!(items.iter().all(|item| !item.is_underline));
    }

    #[test]
    fn repeated_snug_underlines_survive_ruling_filter() {
        // Dense docs underline many full-width lines: span-similar rules at
        // 3+ y-levels used to be discarded wholesale as table rulings.
        // Each rule here snugly matches one text line, so all must mark.
        let mut items = vec![
            item("first underlined line of text", 50.0, 700.0, 300.0, 11.0),
            item("second underlined line here", 50.0, 650.0, 300.0, 11.0),
            item("third underlined line as well", 50.0, 600.0, 300.0, 11.0),
        ];
        let lines = vec![
            hline(50.0, 350.0, 697.0),
            hline(50.0, 350.0, 647.0),
            hline(50.0, 350.0, 597.0),
        ];

        mark_underlined_items(&mut items, &[], &lines, 1);

        assert!(items.iter().all(|item| item.is_underline));
    }

    #[test]
    fn snug_rescue_spans_split_runs_on_one_line() {
        // A single underlined line is often split into several runs (script
        // or font switches). The union of touching runs owns the rule.
        let mut items = vec![
            item("run one", 50.0, 700.0, 100.0, 11.0),
            item("run two", 150.5, 700.0, 100.0, 11.0),
            item("run three", 251.0, 700.0, 99.0, 11.0),
            item("other a", 50.0, 650.0, 300.0, 11.0),
            item("other b", 50.0, 600.0, 300.0, 11.0),
        ];
        let lines = vec![
            hline(50.0, 350.0, 697.0),
            hline(50.0, 350.0, 647.0),
            hline(50.0, 350.0, 597.0),
        ];

        mark_underlined_items(&mut items, &[], &lines, 1);

        assert!(items[0].is_underline && items[1].is_underline && items[2].is_underline);
    }

    #[test]
    fn snug_rescue_denied_for_row_with_cell_gaps() {
        // A full-width rule whose baseline row is several items separated by
        // column-sized gaps is a table row separator, not an underline —
        // even when span-similar rules repeat down the page.
        let mut items = vec![
            item("cell a", 50.0, 700.0, 60.0, 11.0),
            item("cell b", 190.0, 700.0, 60.0, 11.0),
            item("cell c", 330.0, 700.0, 70.0, 11.0),
            item("cell d", 50.0, 650.0, 60.0, 11.0),
            item("cell e", 190.0, 650.0, 60.0, 11.0),
            item("cell f", 330.0, 650.0, 70.0, 11.0),
        ];
        let lines = vec![
            hline(50.0, 400.0, 697.0),
            hline(50.0, 400.0, 647.0),
            hline(50.0, 400.0, 597.0),
        ];

        mark_underlined_items(&mut items, &[], &lines, 1);

        assert!(items.iter().all(|item| !item.is_underline));
    }

    #[test]
    fn snug_rescue_denied_inside_cell_box() {
        // A rule snugly under one text line but enclosed by a drawn cell
        // box that TILES with vertical neighbors (grid evidence) is a row
        // ruling of a rect-grid table. Isolated boxes (callout panels) do
        // not veto — see repeated_snug_underlines_survive_ruling_filter.
        let mut items = vec![
            item("one wide cell row", 50.0, 700.0, 300.0, 11.0),
            item("second wide cell", 50.0, 650.0, 300.0, 11.0),
            item("third wide cell", 50.0, 600.0, 300.0, 11.0),
        ];
        let lines = vec![
            hline(50.0, 350.0, 697.0),
            hline(50.0, 350.0, 647.0),
            hline(50.0, 350.0, 597.0),
        ];
        let boxes = vec![
            cell_rect(45.0, 690.0, 320.0, 50.0),
            cell_rect(45.0, 640.0, 320.0, 50.0),
            cell_rect(45.0, 590.0, 320.0, 50.0),
        ];

        mark_underlined_items(&mut items, &boxes, &lines, 1);

        assert!(items.iter().all(|item| !item.is_underline));
    }

    #[test]
    fn same_row_spaced_rule_segments_do_not_mark_column_labels() {
        let mut items = vec![
            item("Date", 100.0, 500.0, 25.0, 10.0),
            item("Rate", 200.0, 500.0, 25.0, 10.0),
            item("Yield", 300.0, 500.0, 30.0, 10.0),
        ];
        let lines = vec![
            hline(98.0, 128.0, 498.0),
            hline(198.0, 228.0, 498.0),
            hline(298.0, 333.0, 498.0),
        ];

        mark_underlined_items(&mut items, &[], &lines, 1);

        assert!(items.iter().all(|item| !item.is_underline));
    }

    #[test]
    fn vertical_run_is_never_underlined_by_a_rule_under_its_box() {
        // A rotated table header sitting on its cell's bottom border: the
        // rule spans the run's em-wide box right under it. The identical
        // geometry is an underline for a horizontal run, so orientation is
        // the only thing keeping the border from marking the header.
        let mut vertical = item("Header", 100.0, 500.0, 10.0, 10.0);
        vertical.height = 60.0;
        vertical.rotation = 90.0;
        let horizontal = item("Header", 100.0, 500.0, 10.0, 10.0);
        let lines = vec![hline(98.0, 112.0, 498.5)];

        let mut items = vec![vertical];
        mark_underlined_items(&mut items, &[], &lines, 1);
        assert!(!items[0].is_underline);

        let mut items = vec![horizontal];
        mark_underlined_items(&mut items, &[], &lines, 1);
        assert!(items[0].is_underline);

        // Upside-down (180°): the box bottom is the glyph tops, so a rule
        // under it is an overline in text space, not an underline.
        let mut flipped = item("Header", 100.0, 500.0, 10.0, 10.0);
        flipped.rotation = 180.0;
        let mut items = vec![flipped];
        mark_underlined_items(&mut items, &[], &lines, 1);
        assert!(!items[0].is_underline);
        assert!(!items[0].is_strikeout);
    }

    #[test]
    fn upside_down_run_is_underlined_by_a_rule_over_its_box() {
        // A 180° run hangs from y + height = 510; its underline is drawn on
        // the far side of that baseline from the glyphs, i.e. just ABOVE the
        // box in page coordinates. The same rule over an upright run with the
        // same box is nowhere near its baseline.
        let mut flipped = item("Header", 100.0, 500.0, 10.0, 10.0);
        flipped.rotation = 180.0;
        let upright = item("Header", 100.0, 500.0, 10.0, 10.0);
        let lines = vec![hline(98.0, 112.0, 511.5)];

        let mut items = vec![flipped];
        mark_underlined_items(&mut items, &[], &lines, 1);
        assert!(items[0].is_underline);
        assert!(!items[0].is_strikeout);

        let mut items = vec![upright];
        mark_underlined_items(&mut items, &[], &lines, 1);
        assert!(!items[0].is_underline);
        assert!(!items[0].is_strikeout);
    }

    #[test]
    fn oblique_run_is_never_decorated_by_a_horizontal_rule() {
        // A 30° callout has no horizontal rule to match: the rule under its
        // box start would read as an underline, and one through the box as a
        // strikeout, if the windows were measured from a level baseline.
        let mut oblique = item("Callout", 100.0, 500.0, 40.0, 10.0);
        oblique.rotation = 30.0;
        oblique.height = 30.0;
        let under = vec![hline(99.0, 141.0, 498.5)];
        let mut items = vec![oblique.clone()];
        mark_underlined_items(&mut items, &[], &under, 1);
        assert!(!items[0].is_underline && !items[0].is_strikeout);
        let through = vec![hline(100.0, 140.0, 503.0)];
        let mut items = vec![oblique];
        mark_underlined_items(&mut items, &[], &through, 1);
        assert!(!items[0].is_underline && !items[0].is_strikeout);

        // A scanned page's text layer sits a couple of degrees off level and
        // keeps its decorations.
        let mut skewed = item("Header", 100.0, 500.0, 40.0, 10.0);
        skewed.rotation = 2.0;
        let mut items = vec![skewed];
        mark_underlined_items(&mut items, &[], &under, 1);
        assert!(items[0].is_underline);
    }

    #[test]
    fn upside_down_fragments_of_different_sizes_share_a_strike_row() {
        // Two 180° fragments hang from the same baseline (510) while their
        // box bottoms differ by 8pt; grouped at the baseline they form one
        // row that the rule spans snugly, so both are struck.
        let mut small = item("Deleted", 100.0, 500.0, 40.0, 10.0);
        small.rotation = 180.0;
        let mut large = item("text", 145.0, 492.0, 40.0, 18.0);
        large.rotation = 180.0;
        let lines = vec![hline(100.0, 185.0, 507.0)];
        let mut items = vec![small, large];
        mark_underlined_items(&mut items, &[], &lines, 1);
        assert!(items[0].is_strikeout, "{items:?}");
        assert!(items[1].is_strikeout, "{items:?}");
    }

    #[test]
    fn upside_down_run_is_struck_by_a_rule_through_its_glyphs() {
        // Mid x-height of a 180° run lies below its baseline (y + height) in
        // page coordinates: 10pt glyphs hanging from 510 are crossed at 507,
        // where an upright run of the same box has only ascenders.
        let mut flipped = item("Deleted", 100.0, 500.0, 40.0, 10.0);
        flipped.rotation = 180.0;
        let upright = item("Deleted", 100.0, 500.0, 40.0, 10.0);
        let lines = vec![hline(100.0, 140.0, 507.0)];

        let mut items = vec![flipped];
        mark_underlined_items(&mut items, &[], &lines, 1);
        assert!(items[0].is_strikeout);
        assert!(!items[0].is_underline);

        let mut items = vec![upright];
        mark_underlined_items(&mut items, &[], &lines, 1);
        assert!(!items[0].is_strikeout);
        assert!(!items[0].is_underline);
    }
}