Merge pull request #1148 from y-az/fix/page-number-digits

Breaker: keep a page number's digits together

crates/compose/src/breaker.rs

@@ -563,7 +563,11 @@ fn overlong_words(items: &[Item], ig: &[usize], glyphs: &[Glyph], measure: f64)
                     let marks = out.get_or_insert_with(|| vec![false; glyphs.len()]);
                     for i in a..b {
                         let (Some(g), Some(next)) = (glyphs.get(i), glyphs.get(i + 1)) else { continue };
+                        // Glyphs of one source character (an automatic page number's digits, a
+                        // multi-glyph cluster) stay together, as InDesign keeps them.
+                        let one_char = next.byte == g.byte && (next.len == 0 || next.len == g.len);
                         let ok = !g.no_break
+                            && !one_char
                             && g.break_after != Some(false)
                             && next.ch != SOFT_HYPHEN
                             && !is_forced(next.ch)

crates/compose/src/tests.rs

@@ -474,6 +474,23 @@ fn jump_object_keeps_grid_aligned_lines_on_the_grid() {
     assert!((l.baseline - want).abs() < 1e-6, "{} vs {want}", l.baseline);
 }
 
+/// An automatic page number wider than its frame stays on one line and hangs out, as in InDesign
+/// ("136" in a frame made for two digits); breaking it put "13" over "4".
+#[test]
+fn page_number_wider_than_its_frame_stays_whole() {
+    let text = designcraft_doc::story::PAGE_NUMBER.to_string();
+    let (d, sid, _) = doc_with(&text, Rect::new(0.0, 0.0, 10.0, 40.0), ParaAttrs::default());
+    let mut specs = frame_specs(&d, sid);
+    specs[0].page_name = Some("136".into());
+    let cs = compose(&d, d.story(sid).unwrap(), &specs, &ComposeOptions::default());
+    let lines = all_lines(&cs);
+    assert_eq!(lines.len(), 1, "{lines:?}");
+    assert!(!cs.is_overset());
+    // A word of ordinary letters that doesn't fit still breaks where it must.
+    let (d, sid, _) = doc_with("Wordwiderthanframe", Rect::new(0.0, 0.0, 30.0, 200.0), ParaAttrs::default());
+    assert!(all_lines(&compose_story(&d, sid, &ComposeOptions::default())).len() > 1);
+}
+
 #[test]
 fn hostile_wrap_geometry_terminates() {
     let (d, sid) = wrap_doc(ParaAttrs { grid_align: Some(GridAlign::AllLines), ..Default::default() }, &[]);