extensionUtils: Use signals rather than callbacks for finding extensions

This allows us to move to a file-monitor based approach in the future.

Since we need signals, we convert the current set of functions to an
object we attach signals too, leading to the new ExtensionFinder object.

https://bugzilla.gnome.org/show_bug.cgi?id=677586

js/extensionPrefs/main.js

@@ -202,24 +202,29 @@ const Application = new Lang.Class({
     },
 
     _scanExtensions: function() {
-        ExtensionUtils.scanExtensions(Lang.bind(this, function(uuid, dir, type) {
-            if (ExtensionUtils.extensions[uuid] !== undefined)
-                return;
-
-            let extension;
-            try {
-                extension = ExtensionUtils.createExtensionObject(uuid, dir, type);
-            } catch(e) {
-                logError(e, 'Could not create extensions object');
-                return;
-            }
-
-            let iter = this._model.append();
-            this._model.set(iter, [0, 1], [uuid, extension.metadata.name]);
-            this._extensionIters[uuid] = iter;
-        }));
+        let finder = new ExtensionUtils.ExtensionFinder();
+        finder.connect('extension-found', Lang.bind(this, this._extensionFound));
+        finder.scanExtensions();
     },
 
+    _extensionFound: function(signals, uuid, dir, type) {
+        if (ExtensionUtils.extensions[uuid] !== undefined)
+            return;
+
+        let extension;
+        try {
+            extension = ExtensionUtils.createExtensionObject(uuid, dir, type);
+        } catch(e) {
+            logError(e, 'Could not create extensions object');
+            return;
+        }
+
+        let iter = this._model.append();
+        this._model.set(iter, [0, 1], [uuid, extension.metadata.name]);
+        this._extensionIters[uuid] = iter;
+    },
+
+
     _onActivate: function() {
         this._window.present();
     },

js/misc/extensionUtils.js

@@ -3,6 +3,9 @@
 // Common utils for the extension system and the extension
 // preferences tool
 
+const Lang = imports.lang;
+const Signals = imports.signals;
+
 const GLib = imports.gi.GLib;
 const Gio = imports.gi.Gio;
 const ShellJS = imports.gi.ShellJS;
@@ -149,36 +152,41 @@ function installImporter(extension) {
     _extension = null;
 }
 
-function scanExtensionsInDirectory(callback, dir, type) {
-    let fileEnum;
-    let file, info;
-    try {
-        fileEnum = dir.enumerate_children('standard::*', Gio.FileQueryInfoFlags.NONE, null);
-    } catch(e) {
-        logError(e, 'Could not enumerate extensions directory');
-        return;
-    }
+const ExtensionFinder = new Lang.Class({
+    Name: 'ExtensionFinder',
 
-    while ((info = fileEnum.next_file(null)) != null) {
-        let fileType = info.get_file_type();
-        if (fileType != Gio.FileType.DIRECTORY)
-            continue;
-        let uuid = info.get_name();
-        let extensionDir = dir.get_child(uuid);
-        callback(uuid, extensionDir, type);
-    }
-    fileEnum.close(null);
-}
+    _scanExtensionsInDirectory: function(dir, type) {
+        let fileEnum;
+        let file, info;
+        try {
+            fileEnum = dir.enumerate_children('standard::*', Gio.FileQueryInfoFlags.NONE, null);
+        } catch(e) {
+            logError(e, 'Could not enumerate extensions directory');
+            return;
+        }
 
-function scanExtensions(callback) {
-    let userExtensionsDir = Gio.File.new_for_path(GLib.build_filenamev([global.userdatadir, 'extensions']));
-    scanExtensionsInDirectory(callback, userExtensionsDir, ExtensionType.PER_USER);
+        while ((info = fileEnum.next_file(null)) != null) {
+            let fileType = info.get_file_type();
+            if (fileType != Gio.FileType.DIRECTORY)
+                continue;
+            let uuid = info.get_name();
+            let extensionDir = dir.get_child(uuid);
+            this.emit('extension-found', uuid, extensionDir, type);
+        }
+        fileEnum.close(null);
+    },
 
-    let systemDataDirs = GLib.get_system_data_dirs();
-    for (let i = 0; i < systemDataDirs.length; i++) {
-        let dirPath = GLib.build_filenamev([systemDataDirs[i], 'gnome-shell', 'extensions']);
-        let dir = Gio.file_new_for_path(dirPath);
-        if (dir.query_exists(null))
-            scanExtensionsInDirectory(callback, dir, ExtensionType.SYSTEM);
+    scanExtensions: function() {
+        let userExtensionsDir = Gio.File.new_for_path(GLib.build_filenamev([global.userdatadir, 'extensions']));
+        this._scanExtensionsInDirectory(userExtensionsDir, ExtensionType.PER_USER);
+
+        let systemDataDirs = GLib.get_system_data_dirs();
+        for (let i = 0; i < systemDataDirs.length; i++) {
+            let dirPath = GLib.build_filenamev([systemDataDirs[i], 'gnome-shell', 'extensions']);
+            let dir = Gio.file_new_for_path(dirPath);
+            if (dir.query_exists(null))
+                this._scanExtensionsInDirectory(dir, ExtensionType.SYSTEM);
+        }
     }
-}
+});
+Signals.addSignalMethods(ExtensionFinder.prototype);

js/ui/extensionSystem.js

@@ -262,8 +262,10 @@ function init() {
 }
 
 function loadExtensions() {
-    ExtensionUtils.scanExtensions(function(uuid, dir, type) {
+    let finder = new ExtensionUtils.ExtensionFinder();
+    finder.connect('extension-found', function(signals, uuid, dir, type) {
         let enabled = enabledExtensions.indexOf(uuid) != -1;
         loadExtension(dir, type, enabled);
     });
+    finder.scanExtensions();
 }