Add shellDBus.js which implements Eval(str) and an OverviewActive property

For various reasons I'd like a method which allows evaluation; say
log in from another machine and run "gnome-shell --repl" or something.

Also as a possible solution for the screensaver X grab issue, add
a (read/write) property "OverviewActive".

https://bugzilla.gnome.org/show_bug.cgi?id=596102

js/ui/main.js

@@ -1,6 +1,7 @@
 /* -*- mode: js2; js2-basic-offset: 4; indent-tabs-mode: nil -*- */
 
 const Clutter = imports.gi.Clutter;
+const DBus = imports.dbus;
 const Gdk = imports.gi.Gdk;
 const Gio = imports.gi.Gio;
 const GLib = imports.gi.GLib;
@@ -15,6 +16,7 @@ const Overview = imports.ui.overview;
 const Panel = imports.ui.panel;
 const RunDialog = imports.ui.runDialog;
 const LookingGlass = imports.ui.lookingGlass;
+const ShellDBus = imports.ui.shellDBus;
 const Sidebar = imports.ui.sidebar;
 const Tweener = imports.ui.tweener;
 const WindowManager = imports.ui.windowManager;
@@ -30,6 +32,7 @@ let runDialog = null;
 let lookingGlass = null;
 let wm = null;
 let recorder = null;
+let shellDBusService = null;
 let modalCount = 0;
 let modalActorFocusStack = [];
 
@@ -42,6 +45,12 @@ function start() {
     Gio.DesktopAppInfo.set_desktop_env("GNOME");
 
     global.grab_dbus_service();
+    shellDBusService = new ShellDBus.GnomeShell();
+    // Force a connection now; dbus.js will do this internally
+    // if we use its name acquisition stuff but we aren't right
+    // now; to do so we'd need to convert from its async calls
+    // back into sync ones.
+    DBus.session.flush();
 
     Tweener.init();
 

js/ui/shellDBus.js

@@ -0,0 +1,72 @@
+/* -*- mode: js2; js2-basic-offset: 4; indent-tabs-mode: nil -*- */
+
+const DBus = imports.dbus;
+const Lang = imports.lang;
+const Shell = imports.gi.Shell;
+const Mainloop = imports.mainloop;
+
+const Main = imports.ui.main;
+
+const GnomeShellIface = {
+    name: "org.gnome.Shell",
+    methods: [{ name: "Eval",
+                inSignature: "s",
+                outSignature: "bs"
+              }
+             ],
+    signals: [],
+    properties: [{ name: "OverviewActive",
+                   signature: "b",
+                   access: "readwrite" }]
+};
+
+function GnomeShell() {
+    this._init();
+}
+
+GnomeShell.prototype = {
+    _init: function() {
+        DBus.session.exportObject('/org/gnome/Shell', this);
+    },
+
+    /**
+     * Eval:
+     * @code: A string containing JavaScript code
+     *
+     * This function executes arbitrary code in the main
+     * loop, and returns a boolean success and
+     * JSON representation of the object as a string.
+     *
+     * If evaluation completes without throwing an exception,
+     * then the return value will be [true, JSON.stringify(result)].
+     * If evaluation fails, then the return value will be
+     * [false, JSON.stringify(exception)];
+     *
+     */
+    Eval: function(code) {
+        let returnValue;
+        let success;
+        try {
+            returnValue = JSON.stringify(eval(code));
+            success = true;
+        } catch (e) {
+            returnValue = JSON.stringify(e);
+            success = false;
+        }
+        return [success, returnValue];
+    },
+
+    get OverviewActive() {
+        return Main.overview.visible;
+    },
+
+    set OverviewActive(visible) {
+        if (visible)
+            Main.overview.show();
+        else
+            Main.overview.hide();
+    }
+};
+
+DBus.conformExport(GnomeShell.prototype, GnomeShellIface);
+