Embedding API: prefs r/w

components/config/pref_util.rs

@@ -220,6 +220,17 @@ impl<'m, P: Clone> Preferences<'m, P> {
         }
     }
 
+    /// Has the preference been modified from its original value?
+    pub fn is_default(&self, key: &str) -> Result<bool, PrefError> {
+        if let Some(accessor) = self.accessors.get(key) {
+            let user = (accessor.getter)(&self.default_prefs);
+            let default = (accessor.getter)(&self.user_prefs.read().unwrap());
+            Ok(default == user)
+        } else {
+            Err(PrefError::NoSuchPref(String::from(key)))
+        }
+    }
+
     /// Creates an iterator over all keys and values
     pub fn iter<'a>(&'a self) -> impl Iterator<Item = (String, PrefValue)> + 'a {
         let prefs = self.user_prefs.read().unwrap();