Merge branch 'storytold:main' into main

crates/a11y/src/alt.rs

@@ -182,17 +182,51 @@ fn union(a: Option<[f64; 4]>, b: [f64; 4]) -> [f64; 4] {
     }
 }
 
-/// Where the marked content `ids` is drawn on a page (images, forms and paths).
-fn content_bbox(doc: &Document, page: &Dict, ids: &HashSet<i64>) -> Option<[f64; 4]> {
+/// An open marked-content sequence while bounds are gathered: its id, when it is one of those asked
+/// for, and the bounds of what has been drawn in it so far.
+struct Mark {
+    id: Option<i64>,
+    drawn: Option<[f64; 4]>,
+}
+
+/// Adds `b` to what the innermost open sequence has drawn.
+fn draw(marks: &mut [Mark], b: [f64; 4]) {
+    if let Some(m) = marks.last_mut() {
+        m.drawn = Some(union(m.drawn, b));
+    }
+}
+
+/// Closes the innermost open sequence: what it drew counts for its id and for the sequence around it.
+fn close(marks: &mut Vec<Mark>, matching: &mut usize, out: &mut HashMap<i64, [f64; 4]>) {
+    let Some(m) = marks.pop() else { return };
+    if m.id.is_some() {
+        *matching = matching.saturating_sub(1);
+    }
+    let Some(b) = m.drawn else { return };
+    if let Some(id) = m.id {
+        let e = out.entry(id).or_insert(b);
+        *e = union(Some(*e), b);
+    }
+    draw(marks, b);
+}
+
+/// Where each of the marked content `ids` is drawn on a page (images, forms and paths), in one pass
+/// over the page. What a sequence draws counts for every sequence of `ids` around it too.
+pub(crate) fn content_bboxes(doc: &Document, page: &Dict, ids: &HashSet<i64>) -> HashMap<i64, [f64; 4]> {
     let res = page.get(b"Resources").map(|r| doc.resolve(r)).and_then(|r| r.as_dict().cloned()).unwrap_or_default();
     let xobjects = res.get(b"XObject").map(|x| doc.resolve(x)).and_then(|x| x.as_dict().cloned()).unwrap_or_default();
     let props = page_properties(doc, page);
+    #[cfg(test)]
+    crate::BOUNDS_PASSES.with(|c| c.set(c.get() + 1));
     let mut ctm = vec![Matrix([1.0, 0.0, 0.0, 1.0, 0.0, 0.0])];
-    let mut marks: Vec<bool> = Vec::new();
-    let mut bbox = None;
+    // The open marked-content sequences, and how many of them are one of `ids`.
+    let mut marks: Vec<Mark> = Vec::new();
+    let mut matching = 0usize;
+    let mut out = HashMap::new();
     let mut path: Vec<(f64, f64)> = Vec::new();
     for op in pdfcraft_content::parse(&page_content(doc, page)).ops {
-        let inside = marks.iter().any(|m| *m);
+        crate::count_mark_reads(1);
+        let inside = matching > 0;
         let top = ctm.last().copied().unwrap_or(Matrix([1.0, 0.0, 0.0, 1.0, 0.0, 0.0]));
         match op.op.as_slice() {
             b"q" => ctm.push(top),
@@ -206,11 +240,13 @@ fn content_bbox(doc: &Document, page: &Dict, ids: &HashSet<i64>) -> Option<[f64;
                     *t = m.then(&top);
                 }
             }
-            b"BMC" => marks.push(false),
-            b"BDC" => marks.push(bdc_mcid(doc, &props, &op).is_some_and(|n| ids.contains(&n))),
-            b"EMC" => {
-                marks.pop();
+            b"BMC" => marks.push(Mark { id: None, drawn: None }),
+            b"BDC" => {
+                let id = bdc_mcid(doc, &props, &op).filter(|n| ids.contains(n));
+                matching += usize::from(id.is_some());
+                marks.push(Mark { id, drawn: None });
             }
+            b"EMC" => close(&mut marks, &mut matching, &mut out),
             b"m" | b"l" => {
                 if let Some([x, y]) = op.nums::<2>() {
                     path.push(top.apply(x, y));
@@ -231,7 +267,7 @@ fn content_bbox(doc: &Document, page: &Dict, ids: &HashSet<i64>) -> Option<[f64;
             b"f" | b"F" | b"f*" | b"B" | b"B*" | b"b" | b"b*" | b"S" | b"s" | b"n" => {
                 if inside && !matches!(op.op.as_slice(), b"n") {
                     for (x, y) in &path {
-                        bbox = Some(union(bbox, [*x, *y, *x, *y]));
+                        draw(&mut marks, [*x, *y, *x, *y]);
                     }
                 }
                 path.clear();
@@ -251,13 +287,16 @@ fn content_bbox(doc: &Document, page: &Dict, ids: &HashSet<i64>) -> Option<[f64;
                     }
                     _ => top.bbox([0.0, 0.0, 1.0, 1.0]),
                 };
-                bbox = Some(union(bbox, unit));
+                draw(&mut marks, unit);
             }
-            b"BI" if inside => bbox = Some(union(bbox, top.bbox([0.0, 0.0, 1.0, 1.0]))),
+            b"BI" if inside => draw(&mut marks, top.bbox([0.0, 0.0, 1.0, 1.0])),
             _ => {}
         }
     }
-    bbox
+    while !marks.is_empty() {
+        close(&mut marks, &mut matching, &mut out);
+    }
+    out
 }
 
 /// The figures, in document order.
@@ -266,14 +305,28 @@ pub fn figures(doc: &Document) -> Vec<Figure> {
     let role_map = root.get(b"RoleMap").map(|o| doc.resolve(o)).and_then(|o| o.as_dict().cloned()).unwrap_or_default();
     let pages = pdfcraft_model::pages(doc);
     let index: HashMap<ObjRef, usize> = pages.iter().enumerate().map(|(i, p)| (p.obj, i)).collect();
-    elements(doc)
+    let figures: Vec<(Element, Option<usize>)> = elements(doc)
         .into_iter()
         .filter(|e| e.dict.name(b"S").is_some_and(|s| standard(doc, &role_map, s) == b"Figure"))
         .map(|e| {
             let page = e.page.and_then(|p| index.get(&p).copied());
+            (e, page)
+        })
+        .collect();
+    let mut wanted: HashMap<usize, HashSet<i64>> = HashMap::new();
+    for (e, page) in &figures {
+        if let Some(p) = page {
+            wanted.entry(*p).or_default().extend(mcids(&e.dict));
+        }
+    }
+    let bounds: HashMap<usize, HashMap<i64, [f64; 4]>> =
+        wanted.into_iter().filter_map(|(p, ids)| Some((p, content_bboxes(doc, &pages.get(p)?.dict, &ids)))).collect();
+    figures
+        .into_iter()
+        .map(|(e, page)| {
             let alt = e.dict.get(b"Alt").map(|o| doc.resolve(o)).and_then(|o| o.as_string().map(|s| s.to_text()));
-            let ids: HashSet<i64> = mcids(&e.dict).into_iter().collect();
-            let bbox = page.and_then(|p| content_bbox(doc, &pages[p].dict, &ids));
+            let on_page = page.and_then(|p| bounds.get(&p));
+            let bbox = on_page.and_then(|b| mcids(&e.dict).iter().filter_map(|id| b.get(id)).fold(None, |acc, b| Some(union(acc, *b))));
             Figure { obj: e.object, page, alt, bbox }
         })
         .collect()

crates/a11y/src/headings.rs

@@ -182,6 +182,7 @@ pub(crate) fn mcid_texts(doc: &Document, page: &Dict) -> HashMap<i64, String> {
     let res = sub(doc, page, b"Resources");
     let (fonts, props) = (sub(doc, &res, b"Font"), sub(doc, &res, b"Properties"));
     let mut metrics: HashMap<Vec<u8>, Metrics> = HashMap::new();
+    // The id each open marked-content sequence is in: its own, else the enclosing one's.
     let mut stack: Vec<Option<i64>> = Vec::new();
     let mut out: HashMap<i64, String> = HashMap::new();
     // Where each id's last glyph ended, in user space.
@@ -191,16 +192,20 @@ pub(crate) fn mcid_texts(doc: &Document, page: &Dict) -> HashMap<i64, String> {
     let mut unsaved = 0usize;
     let (mut tm, mut tlm) = (Matrix::IDENTITY, Matrix::IDENTITY);
     for op in pdfcraft_content::parse(&page_content(doc, page)).ops {
-        let id = stack.iter().rev().find_map(|m| *m);
+        crate::count_mark_reads(1);
+        let id = stack.last().copied().flatten();
         match op.op.as_slice() {
-            b"BMC" => stack.push(None),
-            b"BDC" => stack.push(match op.operands.get(1) {
-                Some(Object::Dict(d)) => d.get(b"MCID").and_then(Object::as_int),
-                Some(Object::Name(n)) => {
-                    props.get(n).map(|x| doc.resolve(x)).and_then(|x| x.as_dict().and_then(|d| d.get(b"MCID").and_then(Object::as_int)))
+            b"BMC" => stack.push(id),
+            b"BDC" => stack.push(
+                match op.operands.get(1) {
+                    Some(Object::Dict(d)) => d.get(b"MCID").and_then(Object::as_int),
+                    Some(Object::Name(n)) => {
+                        props.get(n).map(|x| doc.resolve(x)).and_then(|x| x.as_dict().and_then(|d| d.get(b"MCID").and_then(Object::as_int)))
+                    }
+                    _ => None,
                 }
-                _ => None,
-            }),
+                .or(id),
+            ),
             b"EMC" => {
                 stack.pop();
             }
@@ -280,17 +285,17 @@ pub(crate) fn mcid_texts(doc: &Document, page: &Dict) -> HashMap<i64, String> {
             };
             for (code, len) in m.codes(&s.bytes) {
                 let trm = tm.then(&gs.ctm);
+                // A glyph's text is only built while its id still takes more.
                 if let Some(id) = id
+                    && out.get(&id).is_none_or(|t| t.len() < MAX_TITLE * 4)
                     && let Some(glyph) = m.text_of(code)
                 {
                     let text = out.entry(id).or_default();
-                    if text.len() < MAX_TITLE * 4 {
-                        let breaks = ends.get(&id).is_some_and(|end| new_word(&trm, *end, gs.size, gs.scale));
-                        if breaks && !text.is_empty() && !text.ends_with(' ') && !glyph.starts_with(' ') {
-                            text.push(' ');
-                        }
-                        text.push_str(&glyph);
+                    let breaks = ends.get(&id).is_some_and(|end| new_word(&trm, *end, gs.size, gs.scale));
+                    if breaks && !text.is_empty() && !text.ends_with(' ') && !glyph.starts_with(' ') {
+                        text.push(' ');
                     }
+                    text.push_str(&glyph);
                 }
                 let advance = m.width(code) * gs.size + gs.char_spacing + if m.is_space(code, len) { gs.word_spacing } else { 0.0 };
                 tm = Matrix::translate(advance * gs.scale, 0.0).then(&tm);

crates/a11y/src/lib.rs

@@ -21,6 +21,22 @@ mod report;
 mod structure;
 mod tags;
 
+#[cfg(test)]
+thread_local! {
+    /// Marked-content stack entries read to decide which marks enclose an operator, for the tests
+    /// that keep that constant per operator.
+    static MARK_READS: std::cell::Cell<usize> = const { std::cell::Cell::new(0) };
+    /// Page content passes made to find figure bounds.
+    static BOUNDS_PASSES: std::cell::Cell<usize> = const { std::cell::Cell::new(0) };
+}
+
+/// Counts `n` marked-content stack reads (tests only).
+#[inline]
+fn count_mark_reads(_n: usize) {
+    #[cfg(test)]
+    MARK_READS.with(|c| c.set(c.get().saturating_add(_n)));
+}
+
 pub use alt::{AltError, ArtifactError, Figure, figures, mark_decorative, mark_tag_artifact, set_alt};
 pub use autotag::{AutoTagError, AutoTagResult, autotag_text};
 pub use autotag_fields::tag_form_fields;

crates/a11y/src/tests.rs

@@ -1023,6 +1023,67 @@ fn glyph_by_tm(text: &str, size: f64, y: f64) -> String {
     ops + " ET"
 }
 
+/// Marked-content stack reads while `f` runs.
+fn mark_reads(f: impl FnOnce()) -> usize {
+    MARK_READS.with(|c| c.set(0));
+    f();
+    MARK_READS.with(|c| c.get())
+}
+
+/// Page content nesting `depth` unmarked `BMC` blocks around a marked one, with `ops` operators inside.
+fn deeply_nested_page(doc: &mut Document, depth: usize, ops: usize) -> pdfcraft_cos::Dict {
+    use pdfcraft_cos::{Dict, Stream};
+    let mut data = "/Figure << /MCID 0 >> BDC ".to_string();
+    data.push_str(&"/X BMC ".repeat(depth));
+    data.push_str(&"0 0 1 1 re f ".repeat(ops));
+    data.push_str(&"EMC ".repeat(depth + 1));
+    let content = doc.add(Stream::flate(Dict::new(), data.as_bytes()));
+    [(b"Contents".to_vec(), Object::Ref(content))].into_iter().collect()
+}
+
+#[test]
+fn marked_text_reads_its_enclosing_id_in_constant_steps() {
+    let mut doc = Document::new_empty();
+    let page = deeply_nested_page(&mut doc, 5_000, 5_000);
+    let reads = mark_reads(|| {
+        crate::headings::mcid_texts(&doc, &page);
+    });
+    // About 15 000 operators; a scan of the stack per operator reads millions of entries.
+    assert!(reads <= 4 * 15_000, "{reads} stack reads");
+}
+
+#[test]
+fn figure_bounds_read_the_marked_content_state_in_constant_steps() {
+    let mut doc = Document::new_empty();
+    let page = deeply_nested_page(&mut doc, 5_000, 5_000);
+    // No mark encloses figure 7, so a scan of the stack per operator reads all of it.
+    let reads = mark_reads(|| {
+        crate::alt::content_bboxes(&doc, &page, &std::collections::HashSet::from([7]));
+    });
+    assert!(reads <= 4 * 15_000, "{reads} stack reads");
+}
+
+#[test]
+fn figure_bounds_take_one_pass_over_each_page() {
+    let n = 50;
+    let content: Vec<String> = (0..n).map(|i| format!("/Figure << /MCID {i} >> BDC {i} 0 1 1 re f EMC")).collect();
+    let kids: Vec<String> = (0..n).map(|i| format!("{} 0 R", 6 + i)).collect();
+    let mut objs: Vec<String> = vec![
+        "<< /Type /Catalog /Pages 2 0 R /StructTreeRoot 5 0 R >>".into(),
+        "<< /Type /Pages /Kids [3 0 R] /Count 1 >>".into(),
+        "<< /Type /Page /Parent 2 0 R /MediaBox [0 0 200 200] /Contents 4 0 R >>".into(),
+        stream(&content.join(" ")),
+        format!("<< /Type /StructTreeRoot /K [{}] >>", kids.join(" ")),
+    ];
+    objs.extend((0..n).map(|i| format!("<< /S /Figure /Pg 3 0 R /K {i} >>")));
+    let doc = pdf(&objs, "");
+    BOUNDS_PASSES.with(|c| c.set(0));
+    let f = figures(&doc);
+    assert_eq!(BOUNDS_PASSES.with(|c| c.get()), 1, "page passes");
+    assert_eq!(f.len(), n);
+    assert!(f.iter().enumerate().all(|(i, f)| f.bbox == Some([i as f64, 0.0, i as f64 + 1.0, 1.0])));
+}
+
 /// One tagged page whose H1 headings show `contents` (one marked-content sequence each).
 fn heading_page(contents: &[String]) -> Document {
     let marked: Vec<String> = contents.iter().enumerate().map(|(i, c)| format!("/H1 << /MCID {i} >> BDC {c} EMC")).collect();

crates/export/src/lib.rs

@@ -8,6 +8,8 @@
 
 #![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)]
 
+use std::collections::HashMap;
+
 mod pptx;
 mod zip;
 
@@ -85,14 +87,33 @@ enum Item<'a> {
     PageBreak,
 }
 
+#[cfg(test)]
+thread_local! {
+    /// Entries read to find a font size's or a colour's slot, for the tests that keep it constant.
+    static LOOKUP_STEPS: std::cell::Cell<usize> = const { std::cell::Cell::new(0) };
+}
+
+/// Counts `n` entries read by a lookup (tests only).
+#[inline]
+fn count_lookup_steps(_n: usize) {
+    #[cfg(test)]
+    LOOKUP_STEPS.with(|c| c.set(c.get().saturating_add(_n)));
+}
+
 /// The body text size: the size most of the document's characters are set in.
 fn body_size(pages: &[Page]) -> f64 {
+    // Sizes in first-seen order (which breaks ties), and where each one is in it.
     let mut by: Vec<(i64, usize)> = Vec::new();
+    let mut slot: HashMap<i64, usize> = HashMap::new();
     for b in pages.iter().flat_map(|p| &p.blocks) {
         let k = (b.size * 2.0).round() as i64;
-        match by.iter_mut().find(|e| e.0 == k) {
-            Some(e) => e.1 += b.text.len(),
-            None => by.push((k, b.text.len())),
+        count_lookup_steps(1);
+        let i = *slot.entry(k).or_insert_with(|| {
+            by.push((k, 0));
+            by.len() - 1
+        });
+        if let Some(e) = by.get_mut(i) {
+            e.1 = e.1.saturating_add(b.text.len());
         }
     }
     by.into_iter().max_by_key(|e| e.1).map_or(11.0, |e| e.0 as f64 / 2.0)
@@ -831,9 +852,12 @@ pub fn rtf(pages: &[Page]) -> String {
     let items = items(pages);
     // The colour table: entry 0 is the default (auto) colour, then each non-black colour once.
     let mut colors: Vec<[u8; 3]> = Vec::new();
+    let mut slot: HashMap<[u8; 3], usize> = HashMap::new();
     let mut note = |c: [f64; 3]| {
         let c = rgb8(c);
-        if c != [0, 0, 0] && !colors.contains(&c) {
+        count_lookup_steps(1);
+        if c != [0, 0, 0] && !slot.contains_key(&c) {
+            slot.insert(c, colors.len());
             colors.push(c);
         }
     };
@@ -847,7 +871,8 @@ pub fn rtf(pages: &[Page]) -> String {
     // `\cfN` for a colour (nothing for black, which keeps the default).
     let cf = |c: [f64; 3]| {
         let c = rgb8(c);
-        colors.iter().position(|e| *e == c).map_or(String::new(), |i| format!("\\cf{}", i + 1))
+        count_lookup_steps(1);
+        slot.get(&c).map_or(String::new(), |i| format!("\\cf{}", i + 1))
     };
     let mut s = String::from("{\\rtf1\\ansi\\deff0{\\fonttbl{\\f0 Helvetica;}}\n");
     if !colors.is_empty() {
@@ -911,6 +936,46 @@ pub fn rtf(pages: &[Page]) -> String {
 mod tests {
     use super::*;
 
+    /// A page of `n` one-word blocks, each in its own size and colour.
+    fn varied_page(n: usize) -> Page {
+        let blocks = (0..n)
+            .map(|i| Block {
+                text: "word".into(),
+                rect: [72.0, i as f64, 100.0, i as f64 + 1.0],
+                size: 4.0 + i as f64 * 0.5,
+                bold: false,
+                italic: false,
+                color: [(i % 256) as f64 / 255.0, (i / 256 % 256) as f64 / 255.0, 0.5],
+                rotation: 0.0,
+            })
+            .collect();
+        Page { width: 612.0, height: 792.0, blocks, images: Vec::new(), background: None }
+    }
+
+    fn lookup_steps(f: impl FnOnce()) -> usize {
+        LOOKUP_STEPS.with(|c| c.set(0));
+        f();
+        LOOKUP_STEPS.with(|c| c.get())
+    }
+
+    #[test]
+    fn many_distinct_sizes_are_counted_in_constant_steps_each() {
+        let pages = [varied_page(3000)];
+        let steps = lookup_steps(|| {
+            body_size(&pages);
+        });
+        assert!(steps <= 2 * 3000, "{steps} steps");
+    }
+
+    #[test]
+    fn many_distinct_colours_take_constant_steps_each() {
+        let pages = [varied_page(3000)];
+        let mut out = String::new();
+        let steps = lookup_steps(|| out = rtf(&pages));
+        assert!(steps <= 4 * 3000, "{steps} steps");
+        assert!(out.contains("\\cf3000 ") || out.contains("\\cf3000\\"), "the last colour has the last slot");
+    }
+
     fn page() -> Page {
         let b = |t: &str, y: f64, size: f64, bold: bool| Block {
             text: t.into(),

crates/fonts/src/lib.rs

@@ -88,17 +88,28 @@ pub fn wrap(text: &str, size: f64, width: f64) -> Vec<String> {
 }
 
 /// [`wrap`], measuring with `measure` (for example [`cjk_width`]).
+///
+/// A line measures as the sum of its words, the spaces between them and the characters of a broken
+/// word, each measured once, so the work stays linear in `text` however much fits on a line.
 pub fn wrap_with(text: &str, size: f64, width: f64, measure: impl Fn(&str, f64) -> f64) -> Vec<String> {
     let mut lines = Vec::new();
+    let space = measure(" ", size);
+    let mut buf = [0u8; 4];
     // A CRLF pair is one break, a lone CR or LF is one break each.
     for para in text.replace("\r\n", "\n").split(['\n', '\r']) {
         let mut line = String::new();
+        let mut line_width = 0.0;
         // No word is on the line yet; an empty word (a leading space) still starts it.
         let mut fresh = true;
         for word in para.split(' ') {
-            let candidate = if fresh { word.to_string() } else { format!("{line} {word}") };
-            if measure(&candidate, size) <= width || fresh && measure(word, size) <= width {
-                line = candidate;
+            let word_width = measure(word, size);
+            let candidate = if fresh { word_width } else { line_width + space + word_width };
+            if candidate <= width {
+                if !fresh {
+                    line.push(' ');
+                }
+                line.push_str(word);
+                line_width = candidate;
                 fresh = false;
                 continue;
             }
@@ -108,11 +119,15 @@ pub fn wrap_with(text: &str, size: f64, width: f64, measure: impl Fn(&str, f64)
             } else {
                 lines.push(std::mem::take(&mut line));
             }
+            line_width = 0.0;
             for ch in word.chars() {
-                if !line.is_empty() && measure(&format!("{line}{ch}"), size) > width {
+                let ch_width = measure(ch.encode_utf8(&mut buf), size);
+                if !line.is_empty() && line_width + ch_width > width {
                     lines.push(std::mem::take(&mut line));
+                    line_width = 0.0;
                 }
                 line.push(ch);
+                line_width += ch_width;
             }
             fresh = line.is_empty();
         }
@@ -442,4 +457,20 @@ mod tests {
         let lines = wrap_with("日本語のテキストは文字単位で折り返されます", 10.0, 45.0, cjk_width);
         assert!(lines.len() > 3 && lines.iter().all(|l| cjk_width(l, 10.0) <= 45.0), "{lines:?}");
     }
+
+    /// Wrapping measures each word and character a bounded number of times, however many fit on a line.
+    #[test]
+    fn wrapping_measures_each_word_a_few_times() {
+        let measured = std::cell::Cell::new(0usize);
+        let measure = |s: &str, size: f64| {
+            measured.set(measured.get() + s.len());
+            helvetica_width(s, size)
+        };
+        let text = format!("{} {}", "word ".repeat(5_000), "x".repeat(5_000));
+        let lines = wrap_with(&text, 1.0, 13_000.0, measure);
+        assert_eq!(lines.len(), 2, "the words fit on one line, the long word on another");
+        assert!(measured.get() <= 4 * text.len(), "{} bytes measured", measured.get());
+        let narrow = wrap_with(&text, 10.0, 100.0, helvetica_width);
+        assert!(narrow.iter().all(|l| helvetica_width(l, 10.0) <= 100.0), "{narrow:?}");
+    }
 }

crates/fonts/src/pdf.rs

@@ -33,9 +33,9 @@ pub struct Metrics {
     widths: Vec<f64>,
     /// Composite fonts: CID → width, and CID ranges with one width.
     cid_widths: HashMap<u32, f64>,
-    cid_ranges: Vec<(u32, u32, f64)>,
+    cid_ranges: Spans<f64>,
     /// Code → CID for embedded non-identity CMaps (`cidrange` / `cidchar`).
-    cid_map: Vec<(u32, u32, u32)>,
+    cid_map: Spans<u32>,
     default: f64,
     /// Composite fonts with an explicit `/DW`: `/W` may leave out the glyphs that have that
     /// width (Chrome and Skia do), so a CID missing from `/W` is not a missing glyph.
@@ -598,8 +598,8 @@ impl Metrics {
             first: 0,
             widths: Vec::new(),
             cid_widths: HashMap::new(),
-            cid_ranges: Vec::new(),
-            cid_map: Vec::new(),
+            cid_ranges: Spans::default(),
+            cid_map: Spans::default(),
             default: 500.0,
             explicit_default: false,
             std14: Some(crate::Std14::Helvetica),
@@ -685,7 +685,7 @@ impl Metrics {
                 if !spaces.is_empty() {
                     m.codes = Codes::Ranges(spaces);
                 }
-                m.cid_map = cids;
+                m.cid_map = Spans::new(cids);
             }
             let desc = font
                 .get(b"DescendantFonts")
@@ -698,6 +698,7 @@ impl Metrics {
                 m.explicit_default = true;
             }
             if let Some(w) = desc.get(b"W").map(|w| doc.resolve(w)).and_then(|w| w.as_array().cloned()) {
+                let mut ranges = Vec::new();
                 let mut i = 0;
                 while i < w.len() {
                     let Some(c0) = doc.resolve(&w[i]).as_f64().map(|v| v as u32) else { break };
@@ -713,14 +714,17 @@ impl Metrics {
                             i += 2;
                         }
                         Some(c1) => {
-                            if let (Some(c1), Some(v)) = (c1.as_f64(), w.get(i + 2).and_then(|x| doc.resolve(x).as_f64())) {
-                                m.cid_ranges.push((c0, c1 as u32, v));
+                            if let (Some(c1), Some(v)) = (c1.as_f64(), w.get(i + 2).and_then(|x| doc.resolve(x).as_f64()))
+                                && ranges.len() < MAX_CMAP_ENTRIES
+                            {
+                                ranges.push((c0, c1 as u32, v));
                             }
                             i += 3;
                         }
                         None => break,
                     }
                 }
+                m.cid_ranges = Spans::new(ranges);
             }
             descriptor = dict(doc, desc.get(b"FontDescriptor"));
         } else {
@@ -791,14 +795,14 @@ impl Metrics {
         if self.cid_map.is_empty() {
             return code;
         }
-        self.cid_map.iter().find(|(lo, hi, _)| code >= *lo && code <= *hi).map_or(0, |(lo, _, c)| c.saturating_add(code - lo))
+        self.cid_map.find(code).map_or(0, |(lo, _, c)| c.saturating_add(code.saturating_sub(*lo)))
     }
 
     /// The advance of `code` in text space per unit of font size.
     pub fn width(&self, code: u32) -> f64 {
         if self.composite {
             let cid = self.cid(code);
-            let w = self.cid_widths.get(&cid).copied().or_else(|| self.cid_ranges.iter().find(|(a, b, _)| cid >= *a && cid <= *b).map(|r| r.2));
+            let w = self.cid_widths.get(&cid).copied().or_else(|| self.cid_ranges.find(cid).map(|r| r.2));
             return w.unwrap_or(self.default) * self.scale;
         }
         if let Some(w) = code.checked_sub(self.first).and_then(|i| self.widths.get(i as usize)) {
@@ -858,7 +862,7 @@ impl Metrics {
             // A CID /W leaves out takes /DW, and Skia (Chrome) leaves out every CID of that width: for
             // those, only the subset's program says whether the glyph is there.
             return self.cid_widths.contains_key(&cid)
-                || self.cid_ranges.iter().any(|(a, b, _)| cid >= *a && cid <= *b)
+                || self.cid_ranges.find(cid).is_some()
                 || !self.subset
                 || self.outlined_cids.get(cid as usize / 64).is_some_and(|w| (*w >> (cid % 64)) & 1 == 1)
                 // No readable TrueType program to ask (e.g. CFF or missing): an explicit /DW
@@ -905,9 +909,13 @@ impl Metrics {
     }
 }
 
-/// The UTF-16 code units of CMap hex bytes.
+/// Most UTF-16 units kept from one ToUnicode destination: the CMap format allows destinations of up
+/// to 512 bytes, and every glyph a sequential range covers builds its text from the whole of one.
+const MAX_DESTINATION_UNITS: usize = 256;
+
+/// The UTF-16 code units of CMap hex bytes, at most [`MAX_DESTINATION_UNITS`] of them.
 fn code_units(b: &[u8]) -> Vec<u16> {
-    b.chunks(2).map(|c| u16::from_be_bytes([c[0], *c.get(1).unwrap_or(&0)])).collect()
+    b.chunks(2).take(MAX_DESTINATION_UNITS).map(|c| u16::from_be_bytes([c[0], *c.get(1).unwrap_or(&0)])).collect()
 }
 
 /// UTF-16BE (with surrogates) from CMap hex bytes.
@@ -954,16 +962,69 @@ fn add_range(out: &mut Unicode, budget: &mut usize, seq: &mut u32, lo: u32, hi:
     true
 }
 
+#[cfg(test)]
+thread_local! {
+    /// Code span records read by CID and width lookups, for the tests that keep a lookup logarithmic.
+    static SPAN_READS: std::cell::Cell<usize> = const { std::cell::Cell::new(0) };
+}
+
+/// Counts one span record read (tests only).
+#[inline]
+fn count_span_reads() {
+    #[cfg(test)]
+    SPAN_READS.with(|c| c.set(c.get().saturating_add(1)));
+}
+
+/// Code spans `(lo, hi, value)` in declaration order, where the first-declared span covering a code
+/// wins, indexed so that a lookup is one binary search.
+#[derive(Clone, Debug, Default, PartialEq)]
+struct Spans<T> {
+    spans: Vec<(u32, u32, T)>,
+    /// The span covering each stretch of codes; see [`stretches`].
+    cover: Vec<(u64, Option<usize>)>,
+}
+
+impl<T> Spans<T> {
+    fn new(spans: Vec<(u32, u32, T)>) -> Self {
+        let bounds: Vec<(u32, u32)> = spans.iter().map(|s| (s.0, s.1)).collect();
+        Spans { cover: stretches(&bounds, false), spans }
+    }
+
+    fn is_empty(&self) -> bool {
+        self.spans.is_empty()
+    }
+
+    /// The first-declared span covering `code`.
+    fn find(&self, code: u32) -> Option<&(u32, u32, T)> {
+        let step = self.cover.partition_point(|&(start, _)| {
+            count_span_reads();
+            start <= u64::from(code)
+        });
+        let &(_, record) = self.cover.get(step.checked_sub(1)?)?;
+        self.spans.get(record?)
+    }
+}
+
 /// For each stretch of codes, from its first code on, the latest-declared range covering it (`None`
 /// where no range does), sorted by code; a lookup is one binary search over it.
 fn cover_index(ranges: &[BfRange]) -> Vec<(u64, Option<usize>)> {
+    let spans: Vec<(u32, u32)> = ranges.iter().map(|r| (r.lo, r.hi)).collect();
+    stretches(&spans, true)
+}
+
+/// For each stretch of codes, from its first code on, the span `(lo, hi)` covering it (`None` where
+/// none does), sorted by code: the latest-declared one when `later_wins`, else the first-declared.
+/// At most `u32::MAX` spans are indexed.
+fn stretches(spans: &[(u32, u32)], later_wins: bool) -> Vec<(u64, Option<usize>)> {
+    // Heap keys, largest for the winning record; the mapping is its own inverse.
+    let key = |record: u32| if later_wins { record } else { !record };
     // Openings (first code, record) and closings (one past the last code), each in code order. The cover
     // can only change at one of their codes, so the sweep visits those codes in order.
-    let mut opens: Vec<(u32, u32)> = ranges.iter().enumerate().map(|(i, r)| (r.lo, i as u32)).collect();
+    let mut opens: Vec<(u32, u32)> = spans.iter().zip(0..u32::MAX).map(|(&(lo, _), i)| (lo, i)).collect();
     opens.sort_unstable();
-    let mut closes: Vec<u64> = ranges.iter().map(|r| u64::from(r.hi) + 1).collect();
+    let mut closes: Vec<u64> = spans.iter().take(opens.len()).map(|&(_, hi)| u64::from(hi) + 1).collect();
     closes.sort_unstable();
-    // Records that have opened and not yet closed; the top is the latest declared one.
+    // Keys of the records that have opened and not yet closed; the top is the winning one.
     let mut open: BinaryHeap<u32> = BinaryHeap::new();
     let mut cover: Vec<(u64, Option<usize>)> = Vec::new();
     let (mut next_open, mut next_close) = (0, 0);
@@ -977,16 +1038,16 @@ fn cover_index(ranges: &[BfRange]) -> Vec<(u64, Option<usize>)> {
         while let Some(&(lo, record)) = opens.get(next_open)
             && u64::from(lo) <= p
         {
-            open.push(record);
+            open.push(key(record));
             next_open += 1;
         }
         while closes.get(next_close).is_some_and(|&end| end <= p) {
             next_close += 1;
         }
-        while open.peek().is_some_and(|&top| ranges.get(top as usize).is_none_or(|r| u64::from(r.hi) < p)) {
+        while open.peek().is_some_and(|&top| spans.get(key(top) as usize).is_none_or(|&(_, hi)| u64::from(hi) < p)) {
             open.pop();
         }
-        let winner = open.peek().map(|&top| top as usize);
+        let winner = open.peek().map(|&top| key(top) as usize);
         if cover.last().map(|&(_, w)| w) != Some(winner) {
             cover.push((p, winner));
         }
@@ -1262,6 +1323,88 @@ mod tests {
 
     use super::*;
 
+    /// Span records read while `f` runs.
+    fn span_reads(f: impl FnOnce()) -> usize {
+        SPAN_READS.with(|c| c.set(0));
+        f();
+        SPAN_READS.with(|c| c.get())
+    }
+
+    /// A composite font with `encoding` as its CMap, `w` as its widths and `to_unicode`.
+    fn composite(doc: &mut Document, encoding: &str, w: Vec<Object>, to_unicode: &str) -> Dict {
+        let mut desc = Dict::new();
+        desc.set(b"Subtype".to_vec(), Object::name("CIDFontType2"));
+        desc.set(b"W".to_vec(), Object::Array(w));
+        let enc = Object::Ref(doc.add(Object::Stream(Stream::flate(Dict::new(), encoding.as_bytes()))));
+        let tu = Object::Ref(doc.add(Object::Stream(Stream::flate(Dict::new(), to_unicode.as_bytes()))));
+        font(
+            doc,
+            vec![
+                ("Subtype", Object::name("Type0")),
+                ("Encoding", enc),
+                ("DescendantFonts", Object::Array(vec![Object::Dict(desc)])),
+                ("ToUnicode", tu),
+            ],
+        )
+    }
+
+    /// Many `/W` ranges that leave a code out cost a glyph of it a binary search, not a scan of them all.
+    #[test]
+    fn widths_of_a_code_no_range_covers_take_few_steps() {
+        let mut doc = Document::new_empty();
+        let w: Vec<Object> = (1..=10_000i64).flat_map(|k| [Object::Int(2 * k), Object::Int(2 * k), Object::Int(500)]).collect();
+        let f = composite(&mut doc, "", w, "");
+        let m = Metrics::from_dict(&doc, &f);
+        assert_eq!(m.width(4), 0.5);
+        let reads = span_reads(|| {
+            for _ in 0..1000 {
+                assert_eq!(m.width(3), 1.0);
+            }
+        });
+        assert!(reads <= 1000 * 64, "{reads} span reads");
+    }
+
+    /// Where spans overlap, the first-declared one wins, as a scan in declaration order finds it.
+    #[test]
+    fn overlapping_spans_resolve_to_the_first_declared() {
+        let spans = Spans::new(vec![(0, 10, 'a'), (5, 20, 'b'), (3, 3, 'c'), (30, 25, 'd'), (u32::MAX, u32::MAX, 'e')]);
+        let found = |code| spans.find(code).map(|s| s.2);
+        let want = [(0, Some('a')), (3, Some('a')), (10, Some('a')), (11, Some('b')), (20, Some('b')), (21, None), (27, None), (u32::MAX, Some('e'))];
+        for (code, value) in want {
+            assert_eq!(found(code), value, "code {code}");
+        }
+    }
+
+    /// Checking the glyph of every explicit ToUnicode entry looks its code up once in the CID map.
+    #[test]
+    fn many_unicode_entries_look_up_their_cids_in_few_steps() {
+        let n = 2000;
+        let cidchars: String = (0..n).map(|k| format!("<{:04X}> {} ", 0x8000 + k, k + 1)).collect();
+        let encoding = format!("1 begincodespacerange <0000> <FFFF> endcodespacerange {n} begincidchar {cidchars} endcidchar");
+        let bfchars: String = (0..n).map(|k| format!("<{:04X}> <{:04X}> ", 0x1000 + k, 0x4E00 + k)).collect();
+        let to_unicode = format!("{n} beginbfchar {bfchars} endbfchar");
+        let mut doc = Document::new_empty();
+        let f = composite(&mut doc, &encoding, Vec::new(), &to_unicode);
+        let reads = span_reads(|| {
+            Metrics::from_dict(&doc, &f);
+        });
+        assert!(reads <= n * 64, "{reads} span reads");
+    }
+
+    /// Every glyph of a sequential range builds its text from the destination, so a long one is cut
+    /// to the CMap limit once, when it is read.
+    #[test]
+    fn unicode_destinations_are_cut_to_the_cmap_limit() {
+        let long = "0041".repeat(4096);
+        let cmap = format!("2 beginbfrange <0010> <0020> <{long}> <0030> <0030> [<{long}>] endbfrange 1 beginbfchar <0040> <{long}> endbfchar");
+        let mut u = Unicode::default();
+        parse_to_unicode(cmap.as_bytes(), &mut u);
+        for code in [0x10, 0x20, 0x30, 0x40] {
+            let text = u.text(code).unwrap_or_default();
+            assert!(!text.is_empty() && text.len() <= MAX_DESTINATION_UNITS * 3, "code {code:#x}: {} bytes", text.len());
+        }
+    }
+
     /// A font whose ranges cover a few low codes keeps tables that size, not a fixed 64k-entry one.
     #[test]
     fn low_code_tables_end_with_the_last_covered_code() {
@@ -1718,7 +1861,7 @@ mod tests {
         let map = to_unicode(b"1 beginbfrange <0001> <0003> [<0041> <zz> <0043>] endbfrange");
         assert_eq!((map.get(&2), map.get(&3).map(String::as_str)), (None, Some("C")));
         let mut m = Metrics::fallback();
-        (_, m.cid_map) = parse_cmap(b"1 begincidrange <0000> <FFFF> 4294967295 endcidrange");
+        m.cid_map = Spans::new(parse_cmap(b"1 begincidrange <0000> <FFFF> 4294967295 endcidrange").1);
         assert_eq!(m.cid(5), u32::MAX);
         let mut doc = Document::new_empty();
         let mut enc = Dict::new();

crates/optimize/src/fragments.rs

@@ -29,6 +29,19 @@ pub const MIN_FRAGMENTS: usize = 4;
 /// Most pixels a merged image may have (memory).
 const MAX_PIXELS: u64 = 80_000_000;
 
+/// Fragment groups a page's search for runs may read per content operator, and at least. A run
+/// that is not one picture is searched again from each of its groups, so without a limit images
+/// drawn over one another take time quadratic in their number; past it, the rest of the page is
+/// left as it is.
+const SCAN_PER_OP: usize = 16;
+const MIN_SCAN: usize = 1 << 16;
+
+#[cfg(test)]
+thread_local! {
+    /// Fragment groups read, for the test that keeps a page's search linear in its content.
+    static GROUP_READS: std::cell::Cell<usize> = const { std::cell::Cell::new(0) };
+}
+
 /// One fragment: its image, its box in the coordinates the run is drawn in, and its size.
 struct Fragment {
     image: ObjRef,
@@ -40,6 +53,8 @@ struct Fragment {
 /// The ops `q`, one or more `cm`, `Do`, `Q` starting at `i`: the index after them, the matrix
 /// and the name drawn.
 fn group_at(ops: &[Op], i: usize) -> Option<(usize, Matrix, Vec<u8>)> {
+    #[cfg(test)]
+    GROUP_READS.with(|c| c.set(c.get().saturating_add(1)));
     if !ops.get(i)?.is("q") {
         return None;
     }
@@ -226,7 +241,13 @@ fn merge_page(doc: &mut Document, page: ObjRef, report: &mut Report, progress: &
     let ops = parsed.ops;
     let mut out: Vec<Op> = Vec::with_capacity(ops.len());
     let (mut i, mut merged, mut k) = (0, 0, 0);
+    let budget = ops.len().saturating_mul(SCAN_PER_OP).max(MIN_SCAN);
+    let mut scanned = 0usize;
     while i < ops.len() {
+        if scanned > budget {
+            out.extend(ops.get(i..).unwrap_or_default().iter().cloned());
+            break;
+        }
         // The longest run of fragment groups from here with one colour space.
         let mut run = Vec::new();
         let mut kind: Option<(Object, usize)> = None;
@@ -245,10 +266,12 @@ fn merge_page(doc: &mut Document, page: ObjRef, report: &mut Report, progress: &
             run.push(Fragment { image, rect: [e, f, e + a, f + d], width, height });
             j = next;
         }
+        scanned = scanned.saturating_add(run.len()).saturating_add(1);
         // Not one picture as a whole: the rows drawn one under the other from the start may be.
         if run.len() >= MIN_FRAGMENTS && !stacked(&mut run) {
             run = drawn_in_sequence(&ops, i, &xobjects, doc);
             j = run_end(&ops, i, run.len());
+            scanned = scanned.saturating_add(run.len().saturating_mul(2)).saturating_add(2);
         }
         let Some((cs, n)) = kind.filter(|_| run.len() >= MIN_FRAGMENTS && stacked(&mut run)) else {
             // Not a run: keep this op and look again from the next one.
@@ -304,6 +327,8 @@ pub(crate) fn run(doc: &mut Document, pages: &[ObjRef], report: &mut Report, pro
 
 #[cfg(test)]
 mod tests {
+    use pdfcraft_cos::{Dict, Document, Object, Stream};
+
     use super::*;
 
     #[test]
@@ -318,4 +343,34 @@ mod tests {
         ];
         assert!(merge(&Document::new_empty(), &run, 3).is_none());
     }
+
+    /// Many images drawn on top of each other are not one picture; looking for runs among them reads
+    /// a bounded number of groups per operator, not the rest of the page from every group.
+    #[test]
+    fn rejected_runs_read_a_bounded_number_of_groups() {
+        let mut doc = Document::new_empty();
+        let mut image = Dict::new();
+        for (k, v) in
+            [("Subtype", Object::name("Image")), ("Width", Object::Int(1)), ("Height", Object::Int(1)), ("BitsPerComponent", Object::Int(8))]
+        {
+            image.set(k.as_bytes().to_vec(), v);
+        }
+        image.set(b"ColorSpace".to_vec(), Object::name("DeviceGray"));
+        let image = doc.add(Object::Stream(Stream::from_raw(image, vec![0])));
+        let groups = 4000;
+        let content = doc.add(Object::Stream(Stream::flate(Dict::new(), "q 10 0 0 10 0 0 cm /Im Do Q\n".repeat(groups).as_bytes())));
+        let mut xobjects = Dict::new();
+        xobjects.set(b"Im".to_vec(), Object::Ref(image));
+        let mut resources = Dict::new();
+        resources.set(b"XObject".to_vec(), Object::Dict(xobjects));
+        let mut page = Dict::new();
+        page.set(b"Contents".to_vec(), Object::Ref(content));
+        page.set(b"Resources".to_vec(), Object::Dict(resources));
+        let page = doc.add(Object::Dict(page));
+        GROUP_READS.with(|c| c.set(0));
+        let merged = merge_page(&mut doc, page, &mut Report::default(), &mut |_| true);
+        assert_eq!(merged.ok(), Some(0));
+        let reads = GROUP_READS.with(|c| c.get());
+        assert!(reads <= 40 * 4 * groups, "{reads} group reads");
+    }
 }

crates/optimize/src/images.rs

@@ -227,6 +227,19 @@ fn is_dct(s: &Stream) -> Option<bool> {
     }
 }
 
+#[cfg(test)]
+thread_local! {
+    /// Pixels decoded from JPEG data, for the test that keeps a mismatched JPEG from decoding.
+    static DECODED_PIXELS: std::cell::Cell<u64> = const { std::cell::Cell::new(0) };
+}
+
+/// Counts `n` decoded pixels (tests only).
+#[inline]
+fn count_decoded(_n: u64) {
+    #[cfg(test)]
+    DECODED_PIXELS.with(|c| c.set(c.get().saturating_add(_n)));
+}
+
 /// 8-bit samples of an image (`n` components), decoded.
 pub(crate) fn pixels(s: &Stream, n: usize) -> Option<Vec<u8>> {
     let (w, h) = (u32::try_from(s.dict.int(b"Width")?).ok()?, u32::try_from(s.dict.int(b"Height")?).ok()?);
@@ -235,7 +248,15 @@ pub(crate) fn pixels(s: &Stream, n: usize) -> Option<Vec<u8>> {
     }
     let bytes = usize::try_from(w).ok()?.checked_mul(usize::try_from(h).ok()?)?.checked_mul(n)?;
     if is_dct(s)? {
-        let img = image::load_from_memory_with_format(&s.raw, image::ImageFormat::Jpeg).ok()?;
+        use image::ImageDecoder as _;
+        // The JPEG's own size is what gets decoded: one other than the dictionary's is refused from
+        // its header, before any pixels are.
+        let decoder = image::codecs::jpeg::JpegDecoder::new(std::io::Cursor::new(&s.raw[..])).ok()?;
+        if decoder.dimensions() != (w, h) {
+            return None;
+        }
+        let img = image::DynamicImage::from_decoder(decoder).ok()?;
+        count_decoded(u64::from(img.width()) * u64::from(img.height()));
         // Adobe CMYK/YCCK JPEGs aren't handled (the colour space check excludes them).
         let v = if n == 1 { img.into_luma8().into_raw() } else { img.into_rgb8().into_raw() };
         (v.len() == bytes).then_some(v)
@@ -432,4 +453,21 @@ mod dimension_tests {
         let stream = Stream::from_raw(dict, vec![1, 2, 3, 4, 5]);
         assert_eq!(pixels(&stream, 1), Some(vec![1, 2, 3, 4]));
     }
+
+    /// A JPEG larger than its dictionary says is refused from its header, before its pixels are decoded.
+    #[test]
+    fn a_jpeg_of_another_size_than_its_dictionary_is_not_decoded() {
+        let data = jpeg(&vec![128; 1000 * 1000], 1, 1000, 1000, 50).unwrap_or_default();
+        let stream = |w: i64, h: i64| {
+            let mut dict = Dict::new();
+            dict.set(b"Width".to_vec(), Object::Int(w));
+            dict.set(b"Height".to_vec(), Object::Int(h));
+            dict.set(b"Filter".to_vec(), Object::name("DCTDecode"));
+            Stream::from_raw(dict, data.clone())
+        };
+        DECODED_PIXELS.with(|c| c.set(0));
+        assert!(pixels(&stream(10, 10), 1).is_none());
+        assert_eq!(DECODED_PIXELS.with(|c| c.get()), 0, "pixels decoded");
+        assert_eq!(pixels(&stream(1000, 1000), 1).map(|p| p.len()), Some(1000 * 1000));
+    }
 }