Replace catch-all experimental flag with fine-grained boolean preferences initialized from a JSON document.

components/util/prefs.rs

@@ -0,0 +1,50 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use resource_files::resources_dir_path;
+use rustc_serialize::json::Json;
+use std::collections::HashMap;
+use std::fs::File;
+use std::sync::{Arc, Mutex};
+
+lazy_static! {
+    static ref PREFS: Arc<Mutex<HashMap<String, bool>>> = {
+        let prefs = read_prefs().unwrap_or(HashMap::new());
+        Arc::new(Mutex::new(prefs))
+    };
+}
+
+fn read_prefs() -> Result<HashMap<String, bool>, ()> {
+    let mut path = resources_dir_path();
+    path.push("prefs.json");
+
+    let mut file = try!(File::open(path).or_else(|e| {
+        println!("Error opening preferences: {:?}.", e);
+        Err(())
+    }));
+    let json = try!(Json::from_reader(&mut file).or_else(|e| {
+        println!("Ignoring invalid JSON in preferences: {:?}.", e);
+        Err(())
+    }));
+
+    let mut prefs = HashMap::new();
+    if let Some(obj) = json.as_object() {
+        for (name, value) in obj.iter() {
+            if let Some(bool_value) = value.as_boolean() {
+                prefs.insert(name.clone(), bool_value);
+            } else {
+                println!("Ignoring non-boolean preference value for {:?}", name);
+            }
+        }
+    }
+    Ok(prefs)
+}
+
+pub fn get_pref(name: &str, default: bool) -> bool {
+    *PREFS.lock().unwrap().get(name).unwrap_or(&default)
+}
+
+pub fn set_pref(name: String, value: bool) {
+    let _ = PREFS.lock().unwrap().insert(name, value);
+}