Add app introspection API

Add a D-Bus API that allows the API user to introspect the application
state of the shell. Currently the only exposed information is list of
running applications and which one is active (i.e. has focus).

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/326
(cherry picked from commit 10c68c6b952959d105c3126fc61f22a199e8e848)

js/js-resources.gresource.xml

@@ -19,6 +19,7 @@
     <file>misc/history.js</file>
     <file>misc/ibusManager.js</file>
     <file>misc/inputMethod.js</file>
+    <file>misc/introspect.js</file>
     <file>misc/jsParse.js</file>
     <file>misc/keyboardManager.js</file>
     <file>misc/loginManager.js</file>

js/misc/introspect.js

@@ -0,0 +1,116 @@
+const Gio = imports.gi.Gio;
+const GLib = imports.gi.GLib;
+const Lang = imports.lang;
+const Meta = imports.gi.Meta;
+const Shell = imports.gi.Shell;
+
+const INTROSPECT_SCHEMA = 'org.gnome.shell';
+const INTROSPECT_KEY = 'introspect';
+const APP_WHITELIST = ['org.freedesktop.impl.portal.desktop.gtk'];
+
+const IntrospectDBusIface = '<node> \
+  <interface name="org.gnome.Shell.Introspect"> \
+    <signal name="RunningApplicationsChanged" /> \
+    <method name="GetRunningApplications"> \
+      <arg name="apps" direction="out" type="a{sa{sv}}" /> \
+    </method> \
+  </interface> \
+</node>';
+
+var IntrospectService = new Lang.Class({
+    Name: 'IntrospectService',
+
+    _init() {
+        this._dbusImpl = Gio.DBusExportedObject.wrapJSObject(IntrospectDBusIface,
+                                                             this);
+        this._dbusImpl.export(Gio.DBus.session, '/org/gnome/Shell/Introspect');
+        Gio.DBus.session.own_name('org.gnome.Shell.Introspect',
+                                  Gio.BusNameOwnerFlags.REPLACE,
+                                  null, null);
+
+        this._runningApplications = {};
+        this._runningApplicationsDirty = true;
+        this._activeApplication = null;
+        this._activeApplicationDirty = true;
+
+        this._appSystem = Shell.AppSystem.get_default();
+        this._appSystem.connect('app-state-changed',
+                                () => {
+                                    this._runningApplicationsDirty = true;
+                                    this._syncRunningApplications();
+                                });
+
+        this._settings = new Gio.Settings({ schema_id: INTROSPECT_SCHEMA });
+
+        let tracker = Shell.WindowTracker.get_default();
+        tracker.connect('notify::focus-app',
+                        () => {
+                            this._activeApplicationDirty = true;
+                            this._syncRunningApplications();
+                        });
+
+        this._syncRunningApplications();
+    },
+
+    _isStandaloneApp(app) {
+        let windows = app.get_windows();
+
+        return app.get_windows().some(w => w.transient_for == null);
+    },
+
+    _isIntrospectEnabled() {
+       return this._settings.get_boolean(INTROSPECT_KEY);
+    },
+
+    _isSenderWhitelisted(sender) {
+       return APP_WHITELIST.includes(sender);
+    },
+
+    _syncRunningApplications() {
+        let tracker = Shell.WindowTracker.get_default();
+        let apps = this._appSystem.get_running();
+        let seatName = "seat0";
+        let newRunningApplications = {};
+
+        let newActiveApplication = null;
+        let focusedApp = tracker.focus_app;
+
+        for (let app of apps) {
+            let appInfo = {};
+            let isAppActive = (focusedApp == app);
+
+            if (!this._isStandaloneApp(app))
+                continue;
+
+            if (isAppActive) {
+                appInfo['active-on-seats'] = new GLib.Variant('as', [seatName]);
+                newActiveApplication = app.get_id();
+            }
+
+            newRunningApplications[app.get_id()] = appInfo;
+        }
+
+        if (this._runningApplicationsDirty ||
+            (this._activeApplicationDirty &&
+             this._activeApplication != newActiveApplication)) {
+            this._runningApplications = newRunningApplications;
+            this._activeApplication = newActiveApplication;
+
+            this._dbusImpl.emit_signal('RunningApplicationsChanged', null);
+        }
+        this._runningApplicationsDirty = false;
+        this._activeApplicationDirty = false;
+    },
+
+    GetRunningApplicationsAsync(params, invocation) {
+        if (!this._isIntrospectEnabled() &&
+            !this._isSenderWhitelisted(invocation.get_sender())) {
+            invocation.return_error_literal(Gio.DBusError,
+                                            Gio.DBusError.ACCESS_DENIED,
+                                            'App introspection not allowed');
+            return;
+        }
+
+        invocation.return_value(new GLib.Variant('(a{sa{sv}})', [this._runningApplications]));
+    }
+});

js/ui/main.js

@@ -20,6 +20,7 @@ const Environment = imports.ui.environment;
 const ExtensionSystem = imports.ui.extensionSystem;
 const ExtensionDownloader = imports.ui.extensionDownloader;
 const InputMethod = imports.misc.inputMethod;
+const Introspect = imports.misc.introspect;
 const Keyboard = imports.ui.keyboard;
 const MessageTray = imports.ui.messageTray;
 const ModalDialog = imports.ui.modalDialog;
@@ -82,6 +83,7 @@ var keyboard = null;
 var layoutManager = null;
 var kbdA11yDialog = null;
 var inputMethod = null;
+var introspectService = null;
 let _startDate;
 let _defaultCssStylesheet = null;
 let _cssStylesheet = null;
@@ -187,6 +189,8 @@ function _initializeUI() {
     windowAttentionHandler = new WindowAttentionHandler.WindowAttentionHandler();
     componentManager = new Components.ComponentManager();
 
+    introspectService = new Introspect.IntrospectService();
+
     layoutManager.init();
     overview.init();