[gtk/a11y/atspi-child] a11y: Emit ChildrenChanged for toplevel list changes

[Emmanuele Bassi <ebassi src gnome org>]

commit e45dd771dbf4f3bb20f5269e08f55e3b1e7e9d9a
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Wed Oct 21 15:37:57 2020 +0100

    a11y: Emit ChildrenChanged for toplevel list changes
    
    GtkAtSpiRoot is not a context, which means it needs to emit
    ChildrenChanged events by itself whenever a toplevel is added to, or
    removed from, the list of toplevels.

 gtk/a11y/gtkatspiroot.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
---
diff --git a/gtk/a11y/gtkatspiroot.c b/gtk/a11y/gtkatspiroot.c
index 75290623ea..8c35fb6a29 100644
--- a/gtk/a11y/gtkatspiroot.c
+++ b/gtk/a11y/gtkatspiroot.c
@@ -405,6 +405,46 @@ static const GDBusInterfaceVTable root_accessible_vtable = {
   NULL,
 };
 
+static void
+root_toplevels__items_changed (GtkAtSpiRoot *self,
+                               guint         position,
+                               guint         removed,
+                               guint         added,
+                               GListModel   *toplevels)
+{
+  GtkWidget *window = g_list_model_get_item (self->toplevels, position);
+  GVariant *window_ref = NULL;
+
+  if (window == NULL)
+    {
+      window_ref = gtk_at_spi_null_ref ();
+    }
+  else
+    {
+      GtkATContext *context = gtk_accessible_get_at_context (GTK_ACCESSIBLE (window));
+
+      window_ref = gtk_at_spi_context_to_ref (GTK_AT_SPI_CONTEXT (context));
+    }
+
+  if (added == 1 && removed == 0)
+    gtk_at_spi_emit_children_changed (self->connection,
+                                      self->root_path,
+                                      GTK_ACCESSIBLE_CHILD_STATE_ADDED,
+                                      position,
+                                      gtk_at_spi_root_to_ref (self),
+                                      window_ref);
+  else if (removed == 1 && added == 0)
+    gtk_at_spi_emit_children_changed (self->connection,
+                                      self->root_path,
+                                      GTK_ACCESSIBLE_CHILD_STATE_REMOVED,
+                                      position,
+                                      gtk_at_spi_root_to_ref (self),
+                                      window_ref);
+
+  if (window != NULL)
+    g_object_unref (window);
+}
+
 static void
 on_registration_reply (GObject      *gobject,
                        GAsyncResult *result,
@@ -439,6 +479,9 @@ on_registration_reply (GObject      *gobject,
 
   /* Monitor the top levels */
   self->toplevels = gtk_window_get_toplevels ();
+  g_signal_connect_swapped (self->toplevels, "items-changed",
+                            G_CALLBACK (root_toplevels__items_changed),
+                            self);
 }
 
 static void