Use fallback list via dyn trait in FontSystem

src/font/fallback/other.rs

@@ -2,17 +2,40 @@
 
 use unicode_script::Script;
 
+use super::Fallback;
+
+/// An empty platform-specific font fallback list.
+pub struct PlatformFallback;
+
+impl Fallback for PlatformFallback {
+    fn common_fallback(&self) -> &'static [&'static str] {
+        common_fallback()
+    }
+
+    fn forbidden_fallback(&self) -> &'static [&'static str] {
+        forbidden_fallback()
+    }
+
+    fn script_fallback(
+        &self,
+        script: unicode_script::Script,
+        locale: &str,
+    ) -> &'static [&'static str] {
+        script_fallback(script, locale)
+    }
+}
+
 // Fallbacks to use after any script specific fallbacks
-pub fn common_fallback() -> &'static [&'static str] {
+fn common_fallback() -> &'static [&'static str] {
     &[]
 }
 
 // Fallbacks to never use
-pub fn forbidden_fallback() -> &'static [&'static str] {
+fn forbidden_fallback() -> &'static [&'static str] {
     &[]
 }
 
 // Fallbacks to use per script
-pub fn script_fallback(_script: Script, _locale: &str) -> &'static [&'static str] {
+fn script_fallback(_script: Script, _locale: &str) -> &'static [&'static str] {
     &[]
 }