Fix default font selection

Author: l4l

src/config.rs

@@ -65,6 +65,10 @@ impl Config {
         self.input_text.password = true;
     }
 
+    pub fn override_font(&mut self, font: String) {
+        self.font = Some(font);
+    }
+
     pub fn is_height_adaptive(&self) -> bool {
         self.adaptive_height
     }

src/font/fdue.rs

@@ -108,9 +108,20 @@ fn index_to_u32(idx: i32) -> Option<u32> {
 
 impl FontBackend for Font {
     fn default() -> Self {
+        for name in ["DejaVu Sans Mono", "monospace"] {
+            if let Ok(font) = Font::font_by_name(name) {
+                return font;
+            }
+        }
+
+        log::info!("no preferred default font found, falling back to any available font");
         let pat = Pattern::new(&FONTCONFIG_CACHE);
         fontconfig::list_fonts(&pat, None)
             .iter()
+            .filter(|pat| {
+                pat.lang_set()
+                    .map_or(false, |mut langs| langs.any(|l| l == "en"))
+            })
             .find_map(|pat| {
                 let path = std::path::Path::new(pat.filename()?);
                 if !path.exists() {
@@ -263,3 +274,19 @@ impl FontBackend for Font {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn fontconfig_has_en_font() {
+        let pat = Pattern::new(&FONTCONFIG_CACHE);
+        let fonts = fontconfig::list_fonts(&pat, None);
+        let has_en = fonts.iter().any(|pat| {
+            pat.lang_set()
+                .map_or(false, |mut langs| langs.any(|l| l == "en"))
+        });
+        assert!(has_en, "no font with English language support found");
+    }
+}