#762: one system fallback helper for scripts and shortcut glyphs, a face added once; the glyph test skips when this machine's fonts lack some

crates/ui-egui/src/bidi.rs

@@ -274,8 +274,9 @@ fn word_at(text: &str, i: usize) -> (usize, usize) {
     (a, b)
 }
 
-/// Faces the UI adds for scripts its own fonts lack (desktop: from the system), as egui font data.
-pub fn script_fallbacks(have: &dyn Fn(char) -> bool) -> Vec<(String, egui::FontData)> {
+/// Faces the UI adds for scripts its own fonts lack (desktop: from the system), as egui font data;
+/// `taken` as for [`crate::theme::system_fallbacks`].
+pub fn script_fallbacks(have: &dyn Fn(char) -> bool, taken: &mut Vec<Arc<figcraft_text::Face>>) -> Vec<(String, egui::FontData)> {
     // Hebrew, Arabic letters, Arabic presentation forms (what joined names are drawn with).
     const SAMPLES: [char; 3] = ['\u{05D0}', '\u{0628}', '\u{FE91}'];
     const FAMILIES: [&str; 11] = [
@@ -291,17 +292,7 @@ pub fn script_fallbacks(have: &dyn Fn(char) -> bool) -> Vec<(String, egui::FontD
         "FreeSans",
         "Noto Sans",
     ];
-    let mut out: Vec<(String, egui::FontData)> = Vec::new();
-    let mut taken: Vec<Arc<figcraft_text::Face>> = Vec::new();
-    for c in SAMPLES {
-        if have(c) || taken.iter().any(|f| f.has_char(c)) {
-            continue;
-        }
-        let Some(face) = figcraft_text::face_with_char(c, &FAMILIES) else { continue };
-        out.push((format!("system-{}-{}", face.family, face.style), crate::theme::font_data(&face)));
-        taken.push(face);
-    }
-    out
+    crate::theme::system_fallbacks(SAMPLES, &FAMILIES, have, taken)
 }
 
 #[cfg(test)]

crates/ui-egui/src/theme.rs

@@ -273,8 +273,9 @@ pub fn install_fonts(ctx: &Context, system: bool, cjk: u8) {
                 .filter_map(|f| figcraft_text::find_face(f, "Regular"))
                 .any(|x| x.has_char(c))
         };
-        extra.extend(crate::bidi::script_fallbacks(&embedded));
-        extra.extend(key_symbol_fallbacks(&embedded));
+        let mut taken = Vec::new();
+        extra.extend(crate::bidi::script_fallbacks(&embedded, &mut taken));
+        extra.extend(key_symbol_fallbacks(&embedded, &mut taken));
         extra.extend(crate::cjk::faces(cjk, lang, &embedded).iter().map(|f| (format!("system-{}-{}", f.family, f.style), font_data(f))));
     }
     extra.extend(craft(true));
@@ -291,18 +292,30 @@ pub fn install_fonts(ctx: &Context, system: bool, cjk: u8) {
 
 /// The glyphs macOS shortcuts are written with ([`figcraft_engine::keymap::display`]).
 const KEY_SYMBOLS: &str = "⌃⌥⇧⌘⌫↵⇥⇞⇟←→↑↓";
+/// System families that have them, in order of preference.
+const KEY_FAMILIES: [&str; 6] = ["Lucida Grande", "Apple Symbols", "Segoe UI Symbol", "DejaVu Sans", "Noto Sans Symbols 2", "FreeSans"];
 
 /// System faces for the shortcut glyphs the UI's own fonts lack (egui's default face has ⌘ but
-/// not ⌥ or ↵).
-fn key_symbol_fallbacks(have: &dyn Fn(char) -> bool) -> Vec<(String, FontData)> {
-    const FAMILIES: [&str; 6] = ["Lucida Grande", "Apple Symbols", "Segoe UI Symbol", "DejaVu Sans", "Noto Sans Symbols 2", "FreeSans"];
+/// not ⌥ or ↵); `taken` as for [`system_fallbacks`].
+fn key_symbol_fallbacks(have: &dyn Fn(char) -> bool, taken: &mut Vec<Arc<figcraft_text::Face>>) -> Vec<(String, FontData)> {
+    system_fallbacks(KEY_SYMBOLS.chars(), &KEY_FAMILIES, have, taken)
+}
+
+/// System faces, the first of `families` that has each, for the `samples` neither the UI's own
+/// fonts (`have`) nor the faces already `taken` draw. Each face found joins `taken`, so a face that
+/// several lists name is added once.
+pub(crate) fn system_fallbacks(
+    samples: impl IntoIterator<Item = char>,
+    families: &[&str],
+    have: &dyn Fn(char) -> bool,
+    taken: &mut Vec<Arc<figcraft_text::Face>>,
+) -> Vec<(String, FontData)> {
     let mut out = Vec::new();
-    let mut taken: Vec<Arc<figcraft_text::Face>> = Vec::new();
-    for c in KEY_SYMBOLS.chars() {
+    for c in samples {
         if have(c) || taken.iter().any(|f| f.has_char(c)) {
             continue;
         }
-        let Some(face) = figcraft_text::face_with_char(c, &FAMILIES) else { continue };
+        let Some(face) = figcraft_text::face_with_char(c, families) else { continue };
         out.push((format!("system-{}-{}", face.family, face.style), font_data(&face)));
         taken.push(face);
     }
@@ -360,8 +373,9 @@ mod tests {
     #[test]
     fn ui_font_draws_every_mac_shortcut_glyph() {
         figcraft_text::scan_system_fonts();
-        if key_symbol_fallbacks(&|_| false).is_empty() {
-            eprintln!("no system face with shortcut glyphs; skipping");
+        let lacking: String = KEY_SYMBOLS.chars().filter(|c| figcraft_text::face_with_char(*c, &KEY_FAMILIES).is_none()).collect();
+        if !lacking.is_empty() {
+            eprintln!("no system face here draws {lacking}; skipping");
             return;
         }
         let ctx = Context::default();