Merge PR #1946: XLSX: keep cell fonts' charset (Arabic 178) and family on save

crates/xlsx/src/styles.rs: family/charset block ported into the dxf.is_none() branch of font_xml (PR #1225 made it take Option<&DxfStated>)
docs/file-format-parity.md: header Change line keeps both sides' clauses

crates/xlsx/src/styles.rs

@@ -57,6 +57,9 @@ fn bool_prop(e: &El, name: &str) -> bool {
     e.child(name).is_some_and(|c| c.flag("val", true))
 }
 
+const DEFAULT_FONT_FAMILY: u8 = 2;
+const MAX_FONT_FAMILY: u8 = 14;
+
 pub fn read_font(e: &El, palette: &[u32]) -> Font {
     let mut f = Font::default();
     if let Some(n) = e.child("name").or_else(|| e.child("rFont")).and_then(|n| n.attr("val")) {
@@ -84,6 +87,12 @@ pub fn read_font(e: &El, palette: &[u32]) -> Font {
             _ => VertAlign::Baseline,
         };
     }
+    f.charset = e.child("charset").and_then(|c| c.attr_u32("val")).and_then(|v| u8::try_from(v).ok());
+    f.family = e
+        .child("family")
+        .and_then(|c| c.attr_u32("val"))
+        .and_then(|v| u8::try_from(v).ok())
+        .filter(|v| *v <= MAX_FONT_FAMILY && *v != DEFAULT_FONT_FAMILY);
     f.color = opt_color(e.child("color"), palette);
     // Text 1 (dk1) is what "automatic" font colour means in practice.
     if f.color == Color::Theme(1, 0) {
@@ -445,7 +454,11 @@ fn font_xml(f: &Font, dxf: Option<&DxfStated>, minor: bool) -> String {
         s.push_str("<color theme=\"1\"/>");
     }
     if dxf.is_none() {
-        let _ = write!(s, "<name val=\"{}\"/><family val=\"2\"/>", esc_attr(&f.name));
+        let family = f.family.filter(|v| *v <= MAX_FONT_FAMILY).unwrap_or(DEFAULT_FONT_FAMILY);
+        let _ = write!(s, "<name val=\"{}\"/><family val=\"{family}\"/>", esc_attr(&f.name));
+        if let Some(charset) = f.charset {
+            let _ = write!(s, "<charset val=\"{charset}\"/>");
+        }
         if minor {
             s.push_str("<scheme val=\"minor\"/>");
         }

crates/xlsx/src/tests/roundtrip.rs

@@ -1128,6 +1128,64 @@ fn default_font_survives_a_round_trip() {
     assert_eq!(font0(&saved), (Some("12".into()), Some("Calibri".into()), Some("2".into()), Some("minor".into())));
 }
 
+fn one_font_workbook(font: &str) -> Vec<u8> {
+    let styles = format!(
+        r#"<styleSheet xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main"><fonts count="1"><font>{font}</font></fonts><fills count="1"><fill><patternFill patternType="none"/></fill></fills><borders count="1"><border><left/><right/><top/><bottom/><diagonal/></border></borders><cellStyleXfs count="1"><xf numFmtId="0" fontId="0" fillId="0" borderId="0"/></cellStyleXfs><cellXfs count="1"><xf numFmtId="0" fontId="0" fillId="0" borderId="0" xfId="0"/></cellXfs><cellStyles count="1"><cellStyle name="Normal" xfId="0" builtinId="0"/></cellStyles></styleSheet>"#
+    );
+    let rels = r#"<Relationship Id="rId2" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/styles" Target="styles.xml"/>"#;
+    super::minimal("<sheetData/>", &[("xl/styles.xml", &styles)], rels, "")
+}
+
+#[test]
+fn font_charset_and_family_roundtrip() {
+    let file = one_font_workbook(r#"<name val="Traditional Arabic"/><family val="1"/><charset val="178"/>"#);
+    let (wb, _) = read_xlsx(&file).unwrap();
+    let saved = write_xlsx(&wb).unwrap();
+    let mut pkg = Package::open(&saved).unwrap();
+    let xml = String::from_utf8(pkg.read("xl/styles.xml").unwrap().unwrap()).unwrap();
+    assert!(xml.contains("<name val=\"Traditional Arabic\"/><family val=\"1\"/><charset val=\"178\"/>"), "{xml}");
+
+    let (back, _) = read_xlsx(&saved).unwrap();
+    let font = &back.styles.get(StyleId::DEFAULT).font;
+    let back_saved = write_xlsx(&back).unwrap();
+    let mut pkg = Package::open(&back_saved).unwrap();
+    let xml = String::from_utf8(pkg.read("xl/styles.xml").unwrap().unwrap()).unwrap();
+    assert!(xml.contains("<name val=\"Traditional Arabic\"/><family val=\"1\"/><charset val=\"178\"/>"), "{xml}");
+    assert_eq!(font.name, "Traditional Arabic");
+    assert_eq!(font.family, Some(1));
+    assert_eq!(font.charset, Some(178));
+}
+
+#[test]
+fn fonts_without_charset_write_unchanged() {
+    let file = one_font_workbook(r#"<name val="Arial"/>"#);
+    let saved = write_xlsx(&read_xlsx(&file).unwrap().0).unwrap();
+    let mut pkg = Package::open(&saved).unwrap();
+    let xml = String::from_utf8(pkg.read("xl/styles.xml").unwrap().unwrap()).unwrap();
+    assert!(xml.contains("<name val=\"Arial\"/><family val=\"2\"/>"), "{xml}");
+    assert!(!xml.contains("<charset"), "{xml}");
+}
+
+#[test]
+fn out_of_range_family_is_ignored() {
+    let file = one_font_workbook(r#"<name val="Arial"/><family val="15"/>"#);
+    let (wb, _) = read_xlsx(&file).unwrap();
+    assert_eq!(wb.styles.get(StyleId::DEFAULT).font.family, None);
+    let saved = write_xlsx(&wb).unwrap();
+    let mut pkg = Package::open(&saved).unwrap();
+    let xml = String::from_utf8(pkg.read("xl/styles.xml").unwrap().unwrap()).unwrap();
+    assert!(xml.contains("<name val=\"Arial\"/><family val=\"2\"/>"), "{xml}");
+
+    let mut set_directly = wb.clone();
+    let wide = set_directly.styles.derive(StyleId::DEFAULT, |st| st.font.family = Some(200));
+    set_directly.sheet_mut(0).unwrap().set_value(CellRef::new(0, 0), Value::text("x"));
+    set_directly.sheet_mut(0).unwrap().set_style(CellRef::new(0, 0), wide);
+    let saved = write_xlsx(&set_directly).unwrap();
+    let mut pkg = Package::open(&saved).unwrap();
+    let xml = String::from_utf8(pkg.read("xl/styles.xml").unwrap().unwrap()).unwrap();
+    assert!(!xml.contains("<family val=\"200\"/>"), "{xml}");
+}
+
 #[test]
 fn solid_data_bar_survives_with_sparklines_and_gradient_neighbours() {
     let mut wb = Workbook::new();