Fix hyphenation outside of words (#4498)

3 files changed, 57 insertions, 41 deletions

diff --git a/crates/typst/src/layout/inline/linebreak.rs b/crates/typst/src/layout/inline/linebreak.rs
index dbaa9c59..9deaa92a 100644
--- a/crates/typst/src/layout/inline/linebreak.rs
+++ b/crates/typst/src/layout/inline/linebreak.rs
@@ -1,6 +1,6 @@
 use std::ops::{Add, Sub};
 
-use icu_properties::maps::CodePointMapData;
+use icu_properties::maps::{CodePointMapData, CodePointMapDataBorrowed};
 use icu_properties::sets::CodePointSetData;
 use icu_properties::LineBreak;
 use icu_provider::AsDeserializingBufferProvider;
@@ -8,6 +8,7 @@ use icu_provider_adapters::fork::ForkByKeyProvider;
 use icu_provider_blob::BlobDataProvider;
 use icu_segmenter::LineSegmenter;
 use once_cell::sync::Lazy;
+use unicode_segmentation::UnicodeSegmentation;
 
 use super::*;
 use crate::engine::Engine;
@@ -630,7 +631,7 @@ fn raw_cost(
 /// This is an internal instead of an external iterator because it makes the
 /// code much simpler and the consumers of this function don't need the
 /// composability and flexibility of external iteration anyway.
-fn breakpoints<'a>(p: &'a Preparation<'a>, mut f: impl FnMut(usize, Breakpoint)) {
+fn breakpoints(p: &Preparation, mut f: impl FnMut(usize, Breakpoint)) {
     let text = p.text;
 
     // Single breakpoint at the end for empty text.
@@ -661,7 +662,7 @@ fn breakpoints<'a>(p: &'a Preparation<'a>, mut f: impl FnMut(usize, Breakpoint))
             }
         }
 
-        // Get the UAX #14 linebreak opportunities.
+        // Get the next UAX #14 linebreak opportunity.
         let Some(point) = iter.next() else { break };
 
         // Skip breakpoint if there is no char before it. icu4x generates one
@@ -686,46 +687,13 @@ fn breakpoints<'a>(p: &'a Preparation<'a>, mut f: impl FnMut(usize, Breakpoint))
         };
 
         // Hyphenate between the last and current breakpoint.
-        'hyphenate: {
-            if !hyphenate {
-                break 'hyphenate;
-            }
-
-            // Extract a hyphenatable "word".
-            let word = &text[last..point].trim_end_matches(|c: char| !c.is_alphabetic());
-            if word.is_empty() {
-                break 'hyphenate;
-            }
-
-            let end = last + word.len();
+        if hyphenate {
             let mut offset = last;
-
-            // Determine the language to hyphenate this word in.
-            let Some(lang) = lang_at(p, last) else { break 'hyphenate };
-
-            for syllable in hypher::hyphenate(word, lang) {
-                // Don't hyphenate after the final syllable.
-                offset += syllable.len();
-                if offset == end {
-                    continue;
+            for segment in text[last..point].split_word_bounds() {
+                if !segment.is_empty() && segment.chars().all(char::is_alphabetic) {
+                    hyphenations(p, &lb, offset, segment, &mut f);
                 }
-
-                // Filter out hyphenation opportunities where hyphenation was
-                // actually disabled.
-                if !hyphenate_at(p, offset) {
-                    continue;
-                }
-
-                // Filter out forbidden hyphenation opportunities.
-                if matches!(
-                    syllable.chars().next_back().map(|c| lb.get(c)),
-                    Some(LineBreak::Glue | LineBreak::WordJoiner | LineBreak::ZWJ)
-                ) {
-                    continue;
-                }
-
-                // Call `f` for the word-internal hyphenation opportunity.
-                f(offset, Breakpoint::Hyphen);
+                offset += segment.len();
             }
         }
 
@@ -736,6 +704,44 @@ fn breakpoints<'a>(p: &'a Preparation<'a>, mut f: impl FnMut(usize, Breakpoint))
     }
 }
 
+/// Generate breakpoints for hyphenations within a word.
+fn hyphenations(
+    p: &Preparation,
+    lb: &CodePointMapDataBorrowed<LineBreak>,
+    mut offset: usize,
+    word: &str,
+    mut f: impl FnMut(usize, Breakpoint),
+) {
+    let Some(lang) = lang_at(p, offset) else { return };
+    let end = offset + word.len();
+
+    for syllable in hypher::hyphenate(word, lang) {
+        offset += syllable.len();
+
+        // Don't hyphenate after the final syllable.
+        if offset == end {
+            continue;
+        }
+
+        // Filter out hyphenation opportunities where hyphenation was actually
+        // disabled.
+        if !hyphenate_at(p, offset) {
+            continue;
+        }
+
+        // Filter out forbidden hyphenation opportunities.
+        if matches!(
+            syllable.chars().next_back().map(|c| lb.get(c)),
+            Some(LineBreak::Glue | LineBreak::WordJoiner | LineBreak::ZWJ)
+        ) {
+            continue;
+        }
+
+        // Call `f` for the word-internal hyphenation opportunity.
+        f(offset, Breakpoint::Hyphen);
+    }
+}
+
 /// Produce linebreak opportunities for a link.
 fn linebreak_link(link: &str, mut f: impl FnMut(usize)) {
     #[derive(PartialEq)]
diff --git a/tests/ref/hyphenate-outside-of-words.png b/tests/ref/hyphenate-outside-of-words.png
new file mode 100644
index 00000000..57b11ed8
--- /dev/null
+++ b/tests/ref/hyphenate-outside-of-words.png
diff --git a/tests/suite/layout/inline/hyphenate.typ b/tests/suite/layout/inline/hyphenate.typ
index c366b38f..debce1da 100644
--- a/tests/suite/layout/inline/hyphenate.typ
+++ b/tests/suite/layout/inline/hyphenate.typ
@@ -50,6 +50,16 @@ It's a #emph[Tree]beard.
 #set text(hyphenate: true)
 #h(6pt) networks, the rest.
 
+--- hyphenate-outside-of-words ---
+// More tests for hyphenation of non-words.
+#set text(hyphenate: true)
+#block(width: 0pt, "doesn't")
+#block(width: 0pt, "(OneNote)")
+#block(width: 0pt, "(present)")
+
+#set text(lang: "de")
+#block(width: 0pt, "(bzw.)")
+
 --- hyphenate-pt-repeat-hyphen-natural-word-breaking ---
 // The word breaker naturally breaks arco-da-velha at arco-/-da-velha,
 // so we shall repeat the hyphen, even that hyphenate is set to false.