[gnome-control-center] background: Fix warning when opening background selection dialog

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 9da8e1b68d39741c0ea2b851a4551d2910dbd541
Author: Robert Ancell <robert ancell canonical com>
Date:   Thu Oct 11 09:42:29 2018 +1300

    background: Fix warning when opening background selection dialog
    
    This was due to the callback occurring before all the widgets had been added to
    the dialog.
    
    Also remove the workaround for the handler occuring during/after dispose by
    using g_signal_connect_object.
    
    The warnings were:
    (gnome-control-center:13048): Gtk-CRITICAL **: 09:42:17.841: gtk_bin_get_child: assertion 'GTK_IS_BIN 
(bin)' failed
    (gnome-control-center:13048): Gtk-CRITICAL **: 09:42:17.841: gtk_icon_view_unselect_all: assertion 
'GTK_IS_ICON_VIEW (icon_view)' failed

 panels/background/cc-background-chooser-dialog.c | 17 ++---------------
 1 file changed, 2 insertions(+), 15 deletions(-)
---
diff --git a/panels/background/cc-background-chooser-dialog.c 
b/panels/background/cc-background-chooser-dialog.c
index 8d7bb675d..81f913ac5 100644
--- a/panels/background/cc-background-chooser-dialog.c
+++ b/panels/background/cc-background-chooser-dialog.c
@@ -87,8 +87,6 @@ static const GtkTargetEntry color_targets[] =
   { "application/x-color", 0, COLOR }
 };
 
-static void on_visible_child_notify (CcBackgroundChooserDialog *chooser);
-
 static void
 cc_background_chooser_dialog_realize (GtkWidget *widget)
 {
@@ -126,18 +124,6 @@ cc_background_chooser_dialog_dispose (GObject *object)
       g_clear_object (&chooser->copy_cancellable);
     }
 
-  /* GtkStack triggers notify::visible-child during dispose and this
-   * means that we have to explicitly disconnect the signal handler
-   * before calling up to the parent implementation, or
-   * on_visible_child_notify() will get called while we're in an
-   * inconsistent state.
-   */
-  if (chooser->stack != NULL)
-    {
-      g_signal_handlers_disconnect_by_func (chooser->stack, on_visible_child_notify, chooser);
-      chooser->stack = NULL;
-    }
-
   g_clear_pointer (&chooser->item_to_focus, gtk_tree_row_reference_free);
   g_clear_object (&chooser->pictures_source);
   g_clear_object (&chooser->colors_source);
@@ -475,7 +461,6 @@ cc_background_chooser_dialog_init (CcBackgroundChooserDialog *chooser)
   gtk_widget_show (chooser->stack);
   gtk_stack_set_homogeneous (GTK_STACK (chooser->stack), TRUE);
   gtk_container_add (GTK_CONTAINER (vbox), chooser->stack);
-  g_signal_connect_swapped (chooser->stack, "notify::visible-child", G_CALLBACK (on_visible_child_notify), 
chooser);
 
   /* Add drag and drop support for bg images */
   gtk_drag_dest_set (chooser->stack, GTK_DEST_DEFAULT_ALL, NULL, 0, GDK_ACTION_COPY);
@@ -566,6 +551,8 @@ cc_background_chooser_dialog_init (CcBackgroundChooserDialog *chooser)
   gtk_dialog_add_button (GTK_DIALOG (chooser), _("_Select"), GTK_RESPONSE_OK);
   gtk_dialog_set_default_response (GTK_DIALOG (chooser), GTK_RESPONSE_OK);
   gtk_dialog_set_response_sensitive (GTK_DIALOG (chooser), GTK_RESPONSE_OK, FALSE);
+
+  g_signal_connect_object (chooser->stack, "notify::visible-child", G_CALLBACK (on_visible_child_notify), 
chooser, G_CONNECT_SWAPPED);
 }
 
 static void