introspect: Add GetWindows method

The `GetWindows` method gives access to the list of windows for each
application with some of their properties, so utilities such as dogtail
can pick the window of their choice to interfere with using the provided
window id.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/326
(cherry picked from commit 0f45b438e2b956d3cf52622db875dedab45e49b9)

js/misc/introspect.js

@@ -14,6 +14,9 @@ const IntrospectDBusIface = '<node> \
     <method name="GetRunningApplications"> \
       <arg name="apps" direction="out" type="a{sa{sv}}" /> \
     </method> \
+    <method name="GetWindows"> \
+      <arg name="windows" direction="out" type="a{ta{sv}}" /> \
+    </method> \
   </interface> \
 </node>';
 
@@ -102,6 +105,17 @@ var IntrospectService = new Lang.Class({
         this._activeApplicationDirty = false;
     },
 
+    _isEligibleWindow(window) {
+        if (window.is_override_redirect())
+            return false;
+
+        let type = window.get_window_type();
+        return (type == Meta.WindowType.NORMAL ||
+                type == Meta.WindowType.DIALOG ||
+                type == Meta.WindowType.MODAL_DIALOG ||
+                type == Meta.WindowType.UTILITY);
+    },
+
     GetRunningApplicationsAsync(params, invocation) {
         if (!this._isIntrospectEnabled() &&
             !this._isSenderWhitelisted(invocation.get_sender())) {
@@ -112,5 +126,49 @@ var IntrospectService = new Lang.Class({
         }
 
         invocation.return_value(new GLib.Variant('(a{sa{sv}})', [this._runningApplications]));
+    },
+
+    GetWindowsAsync(params, invocation) {
+        let focusWindow = global.display.get_focus_window();
+        let apps = this._appSystem.get_running();
+        let windowsList = {};
+
+        if (!this._isIntrospectEnabled()) {
+            invocation.return_error_literal(Gio.DBusError,
+                                            Gio.DBusError.ACCESS_DENIED,
+                                            'App introspection not allowed');
+            return;
+        }
+
+        for (let app of apps) {
+            let windows = app.get_windows();
+            for (let window of windows) {
+
+                if (!this._isEligibleWindow(window))
+                    continue;
+
+                let windowId = window.get_id();
+                let frameRect = window.get_frame_rect();
+                let title = window.get_title();
+                let wmClass = window.get_wm_class();
+
+                windowsList[windowId] = {
+                    'app-id': GLib.Variant.new('s', app.get_id()),
+                    'client-type': GLib.Variant.new('u', window.get_client_type()),
+                    'is-hidden': GLib.Variant.new('b', window.is_hidden()),
+                    'has-focus': GLib.Variant.new('b', (window == focusWindow)),
+                    'width': GLib.Variant.new('u', frameRect.width),
+                    'height': GLib.Variant.new('u', frameRect.height)
+                };
+
+                // These properties may not be available for all windows:
+                if (title != null)
+                    windowsList[windowId]['title'] = GLib.Variant.new('s', title);
+
+                if (wmClass != null)
+                    windowsList[windowId]['wm-class'] = GLib.Variant.new('s', wmClass);
+            }
+        }
+        invocation.return_value(new GLib.Variant('(a{ta{sv}})', [windowsList]));
     }
 });