Add extensionSystem

Consumer documentation will live at http://live.gnome.org/GnomeShell/Extensions

In terms of implementation; basically we load extensions from the well-known
directories.  Add a GConf key to disable extensions by uuid.  There is a new
option --create-extension for the gnome-shell script which takes a bit of
interactive input, sets up some sample files, and launches gedit.

No extensions UI in this patch; that will come later.

https://bugzilla.gnome.org/show_bug.cgi?id=599661

js/ui/extensionSystem.js

@@ -0,0 +1,158 @@
+/* -*- mode: js2; js2-basic-offset: 4; indent-tabs-mode: nil -*- */
+
+const GLib = imports.gi.GLib;
+const Gio = imports.gi.Gio;
+const St = imports.gi.St;
+const Shell = imports.gi.Shell;
+
+const ExtensionState = {
+    ENABLED: 1,
+    DISABLED: 2,
+    ERROR: 3,
+    OUT_OF_DATE: 4
+};
+
+const ExtensionType = {
+    SYSTEM: 1,
+    PER_USER: 2
+};
+
+// Maps uuid -> metadata object
+const extensionMeta = {};
+// Maps uuid -> importer object (extension directory tree)
+const extensions = {};
+// Array of uuids
+var disabledExtensions;
+// GFile for user extensions
+var userExtensionsDir = null;
+
+function loadExtension(dir, enabled, type) {
+    let info;
+    let baseErrorString = 'While loading extension from "' + dir.get_parse_name() + '": ';
+
+    let metadataFile = dir.get_child('metadata.json');
+    if (!metadataFile.query_exists(null)) {
+        global.logError(baseErrorString + 'Missing metadata.json');
+        return;
+    }
+
+    let [success, metadataContents, len, etag] = metadataFile.load_contents(null);
+    let meta;
+    try {
+        meta = JSON.parse(metadataContents);
+    } catch (e) {
+        global.logError(baseErrorString + 'Failed to parse metadata.json: ' + e);
+        return;
+    }
+    let requiredProperties = ['uuid', 'name', 'description'];
+    for (let i = 0; i < requiredProperties; i++) {
+        let prop = requiredProperties[i];
+        if (!meta[prop]) {
+            global.logError(baseErrorString + 'missing "' + prop + '" property in metadata.json');
+            return;
+        }
+    }
+    // Encourage people to add this
+    if (!meta['url']) {
+        global.log(baseErrorString + 'Warning: Missing "url" property in metadata.json');
+    }
+
+    let base = dir.get_basename();
+    if (base != meta.uuid) {
+        global.logError(baseErrorString + 'uuid "' + meta.uuid + '" from metadata.json does not match directory name "' + base + '"');
+        return;
+    }
+
+    extensionMeta[meta.uuid] = meta;
+    extensionMeta[meta.uuid].type = type;
+    extensionMeta[meta.uuid].path = dir.get_path();
+    if (!enabled) {
+        extensionMeta[meta.uuid].state = ExtensionState.DISABLED;
+        return;
+    }
+
+    // Default to error, we set success as the last step
+    extensionMeta[meta.uuid].state = ExtensionState.ERROR;
+
+    let extensionJs = dir.get_child('extension.js');
+    if (!extensionJs.query_exists(null)) {
+        global.logError(baseErrorString + 'Missing extension.js');
+        return;
+    }
+    let stylesheetPath = null;
+    let themeContext = St.ThemeContext.get_for_stage(global.stage);
+    let theme = themeContext.get_theme();
+    let stylesheetFile = dir.get_child('stylesheet.css');
+    if (stylesheetFile.query_exists(null)) {
+        try {
+            theme.load_stylesheet(stylesheetFile.get_path());
+        } catch (e) {
+            global.logError(baseErrorString + 'Stylesheet parse error: ' + e);
+            return;
+        }
+    }
+
+    let extensionModule;
+    try {
+        global.add_extension_importer('imports.ui.extensionSystem.extensions', meta.uuid, dir.get_path());
+        extensionModule = extensions[meta.uuid].extension;
+    } catch (e) {
+        if (stylesheetPath != null)
+            theme.unload_stylesheet(stylesheetPath);
+        global.logError(baseErrorString + e);
+        return;
+    }
+    if (!extensionModule.main) {
+        global.logError(baseErrorString + 'missing \'main\' function');
+        return;
+    }
+    try {
+        extensionModule.main();
+    } catch (e) {
+        if (stylesheetPath != null)
+            theme.unload_stylesheet(stylesheetPath);
+        global.logError(baseErrorString + 'Failed to evaluate main function:' + e);
+        return;
+    }
+    extensionMeta[meta.uuid].state = ExtensionState.ENABLED;
+    global.log('Loaded extension ' + meta.uuid);
+}
+
+function init() {
+    let userConfigPath = GLib.get_user_config_dir();
+    let userExtensionsPath = GLib.build_filenamev([userConfigPath, 'gnome-shell', 'extensions']);
+    userExtensionsDir = Gio.file_new_for_path(userExtensionsPath);
+    try {
+        userExtensionsDir.make_directory_with_parents(null);
+    } catch (e) {
+        global.logError(""+e);
+    }
+
+    disabledExtensions = Shell.GConf.get_default().get_string_list('disabled_extensions');
+}
+
+function _loadExtensionsIn(dir, type) {
+    let fileEnum = dir.enumerate_children('standard::*', Gio.FileQueryInfoFlags.NONE, null);
+    let file, info;
+    while ((info = fileEnum.next_file(null)) != null) {
+        let fileType = info.get_file_type();
+        if (fileType != Gio.FileType.DIRECTORY)
+            continue;
+        let name = info.get_name();
+        let enabled = disabledExtensions.indexOf(name) < 0;
+        let child = dir.get_child(name);
+        loadExtension(child, enabled, type);
+    }
+    fileEnum.close(null);
+}
+
+function loadExtensions() {
+    _loadExtensionsIn(userExtensionsDir, ExtensionType.PER_USER);
+    let systemDataDirs = GLib.get_system_data_dirs();
+    for (let i = 0; i < systemDataDirs.length; i++) {
+        let dirPath = systemDataDirs[i] + '/gnome-shell/extensions';
+        let dir = Gio.file_new_for_path(dirPath);
+        if (dir.query_exists(null))
+            _loadExtensionsIn(dir, ExtensionType.SYSTEM);
+    }
+}

js/ui/main.js

@@ -14,6 +14,7 @@ const St = imports.gi.St;
 
 const Chrome = imports.ui.chrome;
 const Environment = imports.ui.environment;
+const ExtensionSystem = imports.ui.extensionSystem;
 const Overview = imports.ui.overview;
 const Panel = imports.ui.panel;
 const PlaceDisplay = imports.ui.placeDisplay;
@@ -129,6 +130,9 @@ function start() {
 
     _relayout();
 
+    ExtensionSystem.init();
+    ExtensionSystem.loadExtensions();
+
     panel.startupAnimation();
 
     let display = global.screen.get_display();