fix(formats): classify ODT paragraph styles from short names only

crates/formats/src/odt/styles.rs

@@ -1,6 +1,9 @@
 use super::xml::{Attrs, Ev, events, get, length, local};
 use super::{Align, Arc, Columns, Fmt, HashMap, Kind, Rgb, VAlign, model};
 
+/// Longest style name looked at for a paragraph kind ("Heading 1", "Preformatted Text"…).
+const MAX_KIND_NAME: usize = 256;
+
 // ---------------------------------------------------------------------------------------------
 // Import
 
@@ -346,8 +349,11 @@ impl Styles {
         let mut kind_at = chain.len();
         for (i, (n, s)) in chain.iter().enumerate() {
             kind_at = i;
-            let dn = s.display.as_deref().unwrap_or(n).to_ascii_lowercase().replace("_20_", " ");
-            let nn = n.to_ascii_lowercase().replace("_20_", " ");
+            // The names that give a kind are short: a longer one isn't normalised, so a huge
+            // display name isn't copied again for every paragraph that uses the style.
+            let norm = |v: &str| if v.len() <= MAX_KIND_NAME { v.to_ascii_lowercase().replace("_20_", " ") } else { String::new() };
+            let dn = norm(s.display.as_deref().unwrap_or(n));
+            let nn = norm(n);
             for cand in [dn.as_str(), nn.as_str()] {
                 if let Some(d) = cand.strip_prefix("heading ").and_then(|r| r.trim().parse::<u8>().ok()) {
                     kind = Kind::Heading(d.clamp(1, 6));

crates/formats/src/odt/tests.rs

@@ -1135,3 +1135,18 @@ fn meta_creation_date_timezones_and_fallbacks() {
     assert_eq!(m2.created, "2024-03-05T13:45:00Z");
     assert_eq!(m2.author, "Solo Creator");
 }
+
+#[test]
+fn style_kinds_come_from_short_names_only() {
+    let mut s = styles::Styles::default();
+    let long = "x".repeat(1 << 20);
+    let xml = format!(
+        r#"<office:document-styles xmlns:office="urn:oasis:names:tc:opendocument:xmlns:office:1.0" xmlns:style="urn:oasis:names:tc:opendocument:xmlns:style:1.0"><office:styles><style:style style:name="Heading_20_2" style:display-name="Heading 2" style:family="paragraph"/><style:style style:name="Big" style:display-name="{long}" style:family="paragraph"/></office:styles></office:document-styles>"#
+    );
+    s.read(xml.as_bytes(), false);
+    assert_eq!(s.para("Heading_20_2").0, Kind::Heading(2));
+    // A huge display name isn't normalised (again) for every paragraph that names it.
+    for _ in 0..10_000 {
+        assert_eq!(s.para("Big").0, Kind::Normal);
+    }
+}