Don't warn about macOS hidden system fonts such as .SF NS (#1504)

crates/engine/src/fonts.rs

@@ -22,12 +22,14 @@ pub fn install_embedded_fonts(p: &Presentation) {
 }
 
 /// The font families the slides' text is drawn in (theme fonts resolved, bullet fonts included)
-/// that aren't installed or bundled, sorted, without duplicates (case-insensitive).
+/// that aren't installed or bundled, sorted, without duplicates (case-insensitive). Names that
+/// start with a dot are macOS hidden system fonts (`.SF NS`); they never appear in a font list
+/// and can't be installed, so they aren't reported.
 pub fn missing_fonts(p: &Presentation) -> Vec<String> {
     let db = FontDb::global();
     let mut out: Vec<String> = Vec::new();
     for family in used_fonts(p) {
-        if !db.has_family(&family) && !out.iter().any(|f| f.eq_ignore_ascii_case(&family)) {
+        if !family.starts_with('.') && !db.has_family(&family) && !out.iter().any(|f| f.eq_ignore_ascii_case(&family)) {
             out.push(family);
         }
     }

crates/engine/src/tests.rs

@@ -1425,6 +1425,14 @@ fn opening_a_file_lists_the_fonts_it_uses_that_are_missing() {
     assert!(s.doc().unwrap().missing_fonts.is_empty());
 }
 
+#[test]
+fn a_macos_hidden_system_font_is_not_reported_missing() {
+    let mut s = Session::with_new();
+    let r = s.execute("file.openBytes", &json!({"name": "a.pptx", "data": deck_in_font(".SF NS")})).unwrap();
+    assert_eq!(r["missingFonts"], json!([]));
+    assert!(s.doc().unwrap().missing_fonts.is_empty());
+}
+
 #[test]
 fn an_embedded_face_is_used_when_the_machine_lacks_it() {
     let mut p = deckcraft_model::Presentation::default();