introspect: Enhance WindowsChanged DBus API

Splits WindowsChanged into 3 signals: WindowAdded, WindowChanged,
WindowRemoved and nclude the window as an argument.  This gives us
the necessary information to tracked each window changed, rather than
requiring continuous calls to GetWindows (returning all windows).

The main consumer of the shell-introspect signals is
xdg-desktop-portal-gnome, so an API break seems reasonable, rather
than introducing a new API.

See: https://gitlab.gnome.org/GNOME/xdg-desktop-portal-gnome/-/merge_requests/93

data/dbus-interfaces/org.gnome.Shell.Introspect.xml

@@ -19,11 +19,26 @@
     <signal name="RunningApplicationsChanged" />
 
     <!--
-        WindowsChanged:
-        @short_description: Notifies when any window opens or closes
+        WindowAdded:
+        @short_description: Notifies when any window opens
     -->
-    <signal name="WindowsChanged" />
-
+    <signal name="WindowAdded">
+      <arg type="a{sv}" name="window" />
+    </signal>
+    <!--
+        WindowChanged:
+        @short_description: Notifies when any window changes
+    -->
+    <signal name="WindowChanged">
+      <arg type="a{sv}" name="window" />
+    </signal>
+    <!--
+        WindowRemoved:
+        @short_description: Notifies when any window closes
+    -->
+    <signal name="WindowRemoved">
+      <arg type="a{sv}" name="window" />
+    </signal>
     <!--
         GetRunningApplications:
         @short_description: Retrieves the description of all running applications

js/misc/introspect.js

@@ -44,7 +44,25 @@ export class IntrospectService {
         });
 
         tracker.connect('tracked-windows-changed',
-            () => this._dbusImpl.emit_signal('WindowsChanged', null));
+            (self, window, app, action) => {
+                if (!this._isEligibleWindow(window))
+                    return;
+                let windowDict = this._getWindowDict(window, app);
+                let windowVariant = new GLib.Variant('(a{sv})', [windowDict]);
+                switch (action) {
+                case Shell.WindowTrackerAction.ADDED:
+                    this._dbusImpl.emit_signal('WindowAdded', windowVariant);
+                    break;
+                case Shell.WindowTrackerAction.CHANGED:
+                    this._dbusImpl.emit_signal('WindowChanged', windowVariant);
+                    break;
+                case Shell.WindowTrackerAction.REMOVED:
+                    this._dbusImpl.emit_signal('WindowRemoved', windowVariant);
+                    break;
+                default:
+                    log(`Incorrect window action ${action}`);
+                }
+            });
 
         this._syncRunningApplications();
 

src/shell-window-tracker.c

@@ -122,7 +122,9 @@ shell_window_tracker_class_init (ShellWindowTrackerClass *klass)
                                                    G_SIGNAL_RUN_LAST,
                                                    0,
                                                    NULL, NULL, NULL,
-                                                   G_TYPE_NONE, 0);
+                                                   G_TYPE_NONE,
+                                                   3, META_TYPE_WINDOW, SHELL_TYPE_APP,
+                                                   G_TYPE_INT);
 }
 
 static gboolean
@@ -529,8 +531,12 @@ on_title_changed (MetaWindow  *window,
                   GParamSpec  *pspec,
                   gpointer     user_data)
 {
+  ShellApp *app;
   ShellWindowTracker *self = SHELL_WINDOW_TRACKER (user_data);
-  g_signal_emit (self, signals[TRACKED_WINDOWS_CHANGED], 0);
+
+  app = get_app_for_window (self, window);
+
+  g_signal_emit (self, signals[TRACKED_WINDOWS_CHANGED], 0, window, app, SHELL_WINDOW_TRACKER_CHANGED);
 }
 
 static void
@@ -569,7 +575,7 @@ track_window (ShellWindowTracker *self,
 
   _shell_app_add_window (app, window);
 
-  g_signal_emit (self, signals[TRACKED_WINDOWS_CHANGED], 0);
+  g_signal_emit (self, signals[TRACKED_WINDOWS_CHANGED], 0, window, app, SHELL_WINDOW_TRACKER_ADDED);
 }
 
 static void
@@ -590,6 +596,7 @@ disassociate_window (ShellWindowTracker   *self,
   if (!app)
     return;
 
+  g_object_ref (window);
   g_object_ref (app);
 
   g_hash_table_remove (self->window_to_app, window);
@@ -600,8 +607,9 @@ disassociate_window (ShellWindowTracker   *self,
   g_signal_handlers_disconnect_by_func (window, G_CALLBACK (on_gtk_application_id_changed), self);
   g_signal_handlers_disconnect_by_func (window, G_CALLBACK (on_window_unmanaged), self);
 
-  g_signal_emit (self, signals[TRACKED_WINDOWS_CHANGED], 0);
+  g_signal_emit (self, signals[TRACKED_WINDOWS_CHANGED], 0, window, app, SHELL_WINDOW_TRACKER_REMOVED);
 
+  g_object_unref (window);
   g_object_unref (app);
 }
 

src/shell-window-tracker.h

@@ -16,6 +16,12 @@ G_BEGIN_DECLS
 G_DECLARE_FINAL_TYPE (ShellWindowTracker, shell_window_tracker,
                       SHELL, WINDOW_TRACKER, GObject)
 
+typedef enum {
+  SHELL_WINDOW_TRACKER_ADDED,
+  SHELL_WINDOW_TRACKER_CHANGED,
+  SHELL_WINDOW_TRACKER_REMOVED
+} ShellWindowTrackerAction;
+
 ShellWindowTracker* shell_window_tracker_get_default(void);
 
 ShellApp *shell_window_tracker_get_window_app (ShellWindowTracker *tracker, MetaWindow *metawin);