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

js/misc/introspect.js

@@ -0,0 +1,111 @@
+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 { loadInterfaceXML } = imports.misc.fileUtils;
+
+const IntrospectDBusIface = loadInterfaceXML('org.gnome.Shell.Introspect');
+
+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]));
+    }
+});