diff --git a/app/actions/dockable-actions.c b/app/actions/dockable-actions.c
index 03c8bdf2bb..3f7e2f645b 100644
--- a/app/actions/dockable-actions.c
+++ b/app/actions/dockable-actions.c
@@ -341,7 +341,7 @@ dockable_actions_update (GimpActionGroup *group,
   else if (tab_style == GIMP_TAB_STYLE_PREVIEW_NAME)
     SET_ACTIVE ("dockable-tab-style-preview-name", TRUE);
 
-  docked_iface = GIMP_DOCKED_GET_INTERFACE (docked);
+  docked_iface = GIMP_DOCKED_GET_IFACE (docked);
   SET_SENSITIVE ("dockable-tab-style-preview",
                  docked_iface->get_preview);
   SET_SENSITIVE ("dockable-tab-style-preview-name",
diff --git a/app/widgets/gimpcontainertreeview.c b/app/widgets/gimpcontainertreeview.c
index fd49e8538d..18f1743c5a 100644
--- a/app/widgets/gimpcontainertreeview.c
+++ b/app/widgets/gimpcontainertreeview.c
@@ -252,7 +252,7 @@ gimp_container_tree_view_constructed (GObject *object)
                                   "enable-search",   FALSE,
                                   "headers-visible", FALSE,
                                   "has-tooltip",     TRUE,
-                                  "show-expanders",  GIMP_CONTAINER_VIEW_GET_INTERFACE (view)->model_is_tree,
+                                  "show-expanders",  GIMP_CONTAINER_VIEW_GET_IFACE (view)->model_is_tree,
                                   NULL);
 
   gtk_container_add (GTK_CONTAINER (box->scrolled_win),
diff --git a/app/widgets/gimpcontainerview.c b/app/widgets/gimpcontainerview.c
index 52316b0e2b..df2026b711 100644
--- a/app/widgets/gimpcontainerview.c
+++ b/app/widgets/gimpcontainerview.c
@@ -292,7 +292,7 @@ gimp_container_view_get_private (GimpContainerView *view)
     {
       GimpContainerViewInterface *view_iface;
 
-      view_iface = GIMP_CONTAINER_VIEW_GET_INTERFACE (view);
+      view_iface = GIMP_CONTAINER_VIEW_GET_IFACE (view);
 
       private = g_slice_new0 (GimpContainerViewPrivate);
 
@@ -376,7 +376,7 @@ gimp_container_view_set_container (GimpContainerView *view,
 
   if (container != private->container)
     {
-      GIMP_CONTAINER_VIEW_GET_INTERFACE (view)->set_container (view, container);
+      GIMP_CONTAINER_VIEW_GET_IFACE (view)->set_container (view, container);
 
       g_object_notify (G_OBJECT (view), "container");
     }
@@ -454,7 +454,7 @@ gimp_container_view_set_context (GimpContainerView *view,
 
   if (context != private->context)
     {
-      GIMP_CONTAINER_VIEW_GET_INTERFACE (view)->set_context (view, context);
+      GIMP_CONTAINER_VIEW_GET_IFACE (view)->set_context (view, context);
 
       g_object_notify (G_OBJECT (view), "context");
     }
@@ -497,7 +497,7 @@ gimp_container_view_set_selection_mode (GimpContainerView *view,
   g_return_if_fail (mode == GTK_SELECTION_SINGLE ||
                     mode == GTK_SELECTION_MULTIPLE);
 
-  GIMP_CONTAINER_VIEW_GET_INTERFACE (view)->set_selection_mode (view, mode);
+  GIMP_CONTAINER_VIEW_GET_IFACE (view)->set_selection_mode (view, mode);
 }
 
 static void
@@ -546,7 +546,7 @@ gimp_container_view_set_view_size (GimpContainerView *view,
       private->view_size         = view_size;
       private->view_border_width = view_border_width;
 
-      GIMP_CONTAINER_VIEW_GET_INTERFACE (view)->set_view_size (view);
+      GIMP_CONTAINER_VIEW_GET_IFACE (view)->set_view_size (view);
 
       g_object_freeze_notify (G_OBJECT (view));
       g_object_notify (G_OBJECT (view), "view-size");
@@ -800,7 +800,7 @@ gimp_container_view_get_selected (GimpContainerView  *view,
 {
   g_return_val_if_fail (GIMP_IS_CONTAINER_VIEW (view), 0);
 
-  return GIMP_CONTAINER_VIEW_GET_INTERFACE (view)->get_selected (view, list);
+  return GIMP_CONTAINER_VIEW_GET_IFACE (view)->get_selected (view, list);
 }
 
 static gint
@@ -934,7 +934,7 @@ gimp_container_view_get_property (GObject    *object,
 static void
 gimp_container_view_clear_items (GimpContainerView *view)
 {
-  GIMP_CONTAINER_VIEW_GET_INTERFACE (view)->clear_items (view);
+  GIMP_CONTAINER_VIEW_GET_IFACE (view)->clear_items (view);
 }
 
 static void
@@ -969,7 +969,7 @@ gimp_container_view_add_container (GimpContainerView *view,
                                    G_CALLBACK (gimp_container_view_name_changed),
                                    view);
 
-      if (GIMP_CONTAINER_VIEW_GET_INTERFACE (view)->expand_item)
+      if (GIMP_CONTAINER_VIEW_GET_IFACE (view)->expand_item)
         {
           private->expanded_changed_handler =
             gimp_tree_handler_connect (container,
@@ -1006,7 +1006,7 @@ gimp_container_view_add_foreach (GimpViewable      *viewable,
   gpointer                    parent_insert_data = NULL;
   gpointer                    insert_data;
 
-  view_iface = GIMP_CONTAINER_VIEW_GET_INTERFACE (view);
+  view_iface = GIMP_CONTAINER_VIEW_GET_IFACE (view);
   private    = GIMP_CONTAINER_VIEW_GET_PRIVATE (view);
 
   parent = gimp_viewable_get_parent (viewable);
@@ -1041,7 +1041,7 @@ gimp_container_view_add (GimpContainerView *view,
   gpointer                    insert_data;
   gint                        index;
 
-  view_iface = GIMP_CONTAINER_VIEW_GET_INTERFACE (view);
+  view_iface = GIMP_CONTAINER_VIEW_GET_IFACE (view);
   private    = GIMP_CONTAINER_VIEW_GET_PRIVATE (view);
 
   index = gimp_container_get_child_index (container,
@@ -1133,7 +1133,7 @@ gimp_container_view_remove (GimpContainerView *view,
 
   if (insert_data)
     {
-      GIMP_CONTAINER_VIEW_GET_INTERFACE (view)->remove_item (view,
+      GIMP_CONTAINER_VIEW_GET_IFACE (view)->remove_item (view,
                                                              viewable,
                                                              insert_data);
 
@@ -1154,7 +1154,7 @@ gimp_container_view_reorder (GimpContainerView *view,
 
   if (insert_data)
     {
-      GIMP_CONTAINER_VIEW_GET_INTERFACE (view)->reorder_item (view,
+      GIMP_CONTAINER_VIEW_GET_IFACE (view)->reorder_item (view,
                                                               viewable,
                                                               new_index,
                                                               insert_data);
@@ -1206,7 +1206,7 @@ gimp_container_view_name_changed (GimpViewable      *viewable,
 
   if (insert_data)
     {
-      GIMP_CONTAINER_VIEW_GET_INTERFACE (view)->rename_item (view,
+      GIMP_CONTAINER_VIEW_GET_IFACE (view)->rename_item (view,
                                                              viewable,
                                                              insert_data);
     }
@@ -1223,7 +1223,7 @@ gimp_container_view_expanded_changed (GimpViewable      *viewable,
 
   if (insert_data)
     {
-      GIMP_CONTAINER_VIEW_GET_INTERFACE (view)->expand_item (view,
+      GIMP_CONTAINER_VIEW_GET_IFACE (view)->expand_item (view,
                                                              viewable,
                                                              insert_data);
     }
diff --git a/app/widgets/gimpcontainerview.h b/app/widgets/gimpcontainerview.h
index bdf3783fd0..154ca2e9c4 100644
--- a/app/widgets/gimpcontainerview.h
+++ b/app/widgets/gimpcontainerview.h
@@ -35,14 +35,10 @@ typedef enum
 } GimpContainerViewProp;
 
 
-#define GIMP_TYPE_CONTAINER_VIEW               (gimp_container_view_get_type ())
-#define GIMP_CONTAINER_VIEW(obj)               (G_TYPE_CHECK_INSTANCE_CAST ((obj), GIMP_TYPE_CONTAINER_VIEW, GimpContainerView))
-#define GIMP_IS_CONTAINER_VIEW(obj)            (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GIMP_TYPE_CONTAINER_VIEW))
-#define GIMP_CONTAINER_VIEW_GET_INTERFACE(obj) (G_TYPE_INSTANCE_GET_INTERFACE ((obj), GIMP_TYPE_CONTAINER_VIEW, GimpContainerViewInterface))
+#define GIMP_TYPE_CONTAINER_VIEW (gimp_container_view_get_type ())
+G_DECLARE_INTERFACE (GimpContainerView, gimp_container_view, GIMP, CONTAINER_VIEW, GtkWidget)
 
 
-typedef struct _GimpContainerViewInterface GimpContainerViewInterface;
-
 struct _GimpContainerViewInterface
 {
   GTypeInterface base_iface;
@@ -98,8 +94,6 @@ struct _GimpContainerViewInterface
 };
 
 
-GType              gimp_container_view_get_type           (void) G_GNUC_CONST;
-
 GimpContainer    * gimp_container_view_get_container      (GimpContainerView  *view);
 void               gimp_container_view_set_container      (GimpContainerView  *view,
                                                            GimpContainer      *container);
diff --git a/app/widgets/gimpdockable.c b/app/widgets/gimpdockable.c
index 8127843a2f..0ab1f14fd0 100644
--- a/app/widgets/gimpdockable.c
+++ b/app/widgets/gimpdockable.c
@@ -398,7 +398,7 @@ gimp_dockable_set_tab_style (GimpDockable *dockable,
 
   child = gtk_bin_get_child (GTK_BIN (dockable));
 
-  if (child && ! GIMP_DOCKED_GET_INTERFACE (child)->get_preview)
+  if (child && ! GIMP_DOCKED_GET_IFACE (child)->get_preview)
     tab_style = gimp_preview_tab_style_to_icon (tab_style);
 
   dockable->p->tab_style = tab_style;
diff --git a/app/widgets/gimpdockcontainer.c b/app/widgets/gimpdockcontainer.c
index f412b622a2..95c829ea2c 100644
--- a/app/widgets/gimpdockcontainer.c
+++ b/app/widgets/gimpdockcontainer.c
@@ -56,7 +56,7 @@ gimp_dock_container_get_docks (GimpDockContainer *container)
 
   g_return_val_if_fail (GIMP_IS_DOCK_CONTAINER (container), NULL);
 
-  iface = GIMP_DOCK_CONTAINER_GET_INTERFACE (container);
+  iface = GIMP_DOCK_CONTAINER_GET_IFACE (container);
 
   if (iface->get_docks)
     return iface->get_docks (container);
@@ -77,7 +77,7 @@ gimp_dock_container_get_dialog_factory (GimpDockContainer *container)
 
   g_return_val_if_fail (GIMP_IS_DOCK_CONTAINER (container), NULL);
 
-  iface = GIMP_DOCK_CONTAINER_GET_INTERFACE (container);
+  iface = GIMP_DOCK_CONTAINER_GET_IFACE (container);
 
   if (iface->get_dialog_factory)
     return iface->get_dialog_factory (container);
@@ -98,7 +98,7 @@ gimp_dock_container_get_ui_manager (GimpDockContainer *container)
 
   g_return_val_if_fail (GIMP_IS_DOCK_CONTAINER (container), NULL);
 
-  iface = GIMP_DOCK_CONTAINER_GET_INTERFACE (container);
+  iface = GIMP_DOCK_CONTAINER_GET_IFACE (container);
 
   if (iface->get_ui_manager)
     return iface->get_ui_manager (container);
@@ -123,7 +123,7 @@ gimp_dock_container_add_dock (GimpDockContainer   *container,
 
   g_return_if_fail (GIMP_IS_DOCK_CONTAINER (container));
 
-  iface = GIMP_DOCK_CONTAINER_GET_INTERFACE (container);
+  iface = GIMP_DOCK_CONTAINER_GET_IFACE (container);
 
   if (iface->add_dock)
     iface->add_dock (container,
@@ -148,7 +148,7 @@ gimp_dock_container_get_dock_side (GimpDockContainer   *container,
 
   g_return_val_if_fail (GIMP_IS_DOCK_CONTAINER (container), -1);
 
-  iface = GIMP_DOCK_CONTAINER_GET_INTERFACE (container);
+  iface = GIMP_DOCK_CONTAINER_GET_IFACE (container);
 
   if (iface->get_dock_side)
     return iface->get_dock_side (container, dock);
diff --git a/app/widgets/gimpdockcontainer.h b/app/widgets/gimpdockcontainer.h
index 0fe9d0d18a..497fd33b48 100644
--- a/app/widgets/gimpdockcontainer.h
+++ b/app/widgets/gimpdockcontainer.h
@@ -22,14 +22,10 @@
 #define __GIMP_DOCK_CONTAINER_H__
 
 
-#define GIMP_TYPE_DOCK_CONTAINER               (gimp_dock_container_get_type ())
-#define GIMP_DOCK_CONTAINER(obj)               (G_TYPE_CHECK_INSTANCE_CAST ((obj), GIMP_TYPE_DOCK_CONTAINER, GimpDockContainer))
-#define GIMP_IS_DOCK_CONTAINER(obj)            (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GIMP_TYPE_DOCK_CONTAINER))
-#define GIMP_DOCK_CONTAINER_GET_INTERFACE(obj) (G_TYPE_INSTANCE_GET_INTERFACE ((obj), GIMP_TYPE_DOCK_CONTAINER, GimpDockContainerInterface))
+#define GIMP_TYPE_DOCK_CONTAINER (gimp_dock_container_get_type ())
+G_DECLARE_INTERFACE (GimpDockContainer, gimp_dock_container, GIMP, DOCK_CONTAINER, GtkWidget)
 
 
-typedef struct _GimpDockContainerInterface GimpDockContainerInterface;
-
 struct _GimpDockContainerInterface
 {
   GTypeInterface base_iface;
@@ -46,8 +42,6 @@ struct _GimpDockContainerInterface
 };
 
 
-GType               gimp_dock_container_get_type           (void) G_GNUC_CONST;
-
 GList             * gimp_dock_container_get_docks          (GimpDockContainer   *container);
 GimpDialogFactory * gimp_dock_container_get_dialog_factory (GimpDockContainer   *container);
 GimpUIManager     * gimp_dock_container_get_ui_manager     (GimpDockContainer   *container);
diff --git a/app/widgets/gimpdocked.c b/app/widgets/gimpdocked.c
index cfcd6b276f..31859804e3 100644
--- a/app/widgets/gimpdocked.c
+++ b/app/widgets/gimpdocked.c
@@ -129,7 +129,7 @@ gimp_docked_set_aux_info (GimpDocked *docked,
 
   g_return_if_fail (GIMP_IS_DOCKED (docked));
 
-  docked_iface = GIMP_DOCKED_GET_INTERFACE (docked);
+  docked_iface = GIMP_DOCKED_GET_IFACE (docked);
 
   if (docked_iface->set_aux_info)
     docked_iface->set_aux_info (docked, aux_info);
@@ -142,7 +142,7 @@ gimp_docked_get_aux_info (GimpDocked *docked)
 
   g_return_val_if_fail (GIMP_IS_DOCKED (docked), NULL);
 
-  docked_iface = GIMP_DOCKED_GET_INTERFACE (docked);
+  docked_iface = GIMP_DOCKED_GET_IFACE (docked);
 
   if (docked_iface->get_aux_info)
     return docked_iface->get_aux_info (docked);
@@ -159,7 +159,7 @@ gimp_docked_get_preview (GimpDocked  *docked,
 
   g_return_val_if_fail (GIMP_IS_DOCKED (docked), NULL);
 
-  docked_iface = GIMP_DOCKED_GET_INTERFACE (docked);
+  docked_iface = GIMP_DOCKED_GET_IFACE (docked);
 
   if (docked_iface->get_preview)
     return docked_iface->get_preview (docked, context, size);
@@ -174,7 +174,7 @@ gimp_docked_get_prefer_icon (GimpDocked *docked)
 
   g_return_val_if_fail (GIMP_IS_DOCKED (docked), FALSE);
 
-  docked_iface = GIMP_DOCKED_GET_INTERFACE (docked);
+  docked_iface = GIMP_DOCKED_GET_IFACE (docked);
 
   if (docked_iface->get_prefer_icon)
     return docked_iface->get_prefer_icon (docked);
@@ -193,7 +193,7 @@ gimp_docked_get_menu (GimpDocked     *docked,
   g_return_val_if_fail (ui_path != NULL, NULL);
   g_return_val_if_fail (popup_data != NULL, NULL);
 
-  docked_iface = GIMP_DOCKED_GET_INTERFACE (docked);
+  docked_iface = GIMP_DOCKED_GET_IFACE (docked);
 
   if (docked_iface->get_menu)
     return docked_iface->get_menu (docked, ui_path, popup_data);
@@ -208,7 +208,7 @@ gimp_docked_get_title (GimpDocked *docked)
 
   g_return_val_if_fail (GIMP_IS_DOCKED (docked), NULL);
 
-  docked_iface = GIMP_DOCKED_GET_INTERFACE (docked);
+  docked_iface = GIMP_DOCKED_GET_IFACE (docked);
 
   if (docked_iface->get_title)
     return docked_iface->get_title (docked);
@@ -225,7 +225,7 @@ gimp_docked_set_context (GimpDocked  *docked,
   g_return_if_fail (GIMP_IS_DOCKED (docked));
   g_return_if_fail (context == NULL || GIMP_IS_CONTEXT (context));
 
-  docked_iface = GIMP_DOCKED_GET_INTERFACE (docked);
+  docked_iface = GIMP_DOCKED_GET_IFACE (docked);
 
   if (docked_iface->set_context)
     docked_iface->set_context (docked, context);
@@ -238,7 +238,7 @@ gimp_docked_has_button_bar (GimpDocked *docked)
 
   g_return_val_if_fail (GIMP_IS_DOCKED (docked), FALSE);
 
-  docked_iface = GIMP_DOCKED_GET_INTERFACE (docked);
+  docked_iface = GIMP_DOCKED_GET_IFACE (docked);
 
   if (docked_iface->has_button_bar)
     return docked_iface->has_button_bar (docked);
@@ -254,7 +254,7 @@ gimp_docked_set_show_button_bar (GimpDocked *docked,
 
   g_return_if_fail (GIMP_IS_DOCKED (docked));
 
-  docked_iface = GIMP_DOCKED_GET_INTERFACE (docked);
+  docked_iface = GIMP_DOCKED_GET_IFACE (docked);
 
   if (docked_iface->set_show_button_bar)
     docked_iface->set_show_button_bar (docked, show ? TRUE : FALSE);
@@ -267,7 +267,7 @@ gimp_docked_get_show_button_bar (GimpDocked *docked)
 
   g_return_val_if_fail (GIMP_IS_DOCKED (docked), FALSE);
 
-  docked_iface = GIMP_DOCKED_GET_INTERFACE (docked);
+  docked_iface = GIMP_DOCKED_GET_IFACE (docked);
 
   if (docked_iface->get_show_button_bar)
     return docked_iface->get_show_button_bar (docked);
diff --git a/app/widgets/gimpdocked.h b/app/widgets/gimpdocked.h
index 2a5fa22122..ae6433282f 100644
--- a/app/widgets/gimpdocked.h
+++ b/app/widgets/gimpdocked.h
@@ -22,14 +22,10 @@
 #define __GIMP_DOCKED_H__
 
 
-#define GIMP_TYPE_DOCKED               (gimp_docked_get_type ())
-#define GIMP_IS_DOCKED(obj)            (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GIMP_TYPE_DOCKED))
-#define GIMP_DOCKED(obj)               (G_TYPE_CHECK_INSTANCE_CAST ((obj), GIMP_TYPE_DOCKED, GimpDocked))
-#define GIMP_DOCKED_GET_INTERFACE(obj) (G_TYPE_INSTANCE_GET_INTERFACE ((obj), GIMP_TYPE_DOCKED, GimpDockedInterface))
+#define GIMP_TYPE_DOCKED (gimp_docked_get_type ())
+G_DECLARE_INTERFACE (GimpDocked, gimp_docked, GIMP, DOCKED, GtkWidget)
 
 
-typedef struct _GimpDockedInterface GimpDockedInterface;
-
 /**
  * GimpDockedInterface:
  *
@@ -66,8 +62,6 @@ struct _GimpDockedInterface
 };
 
 
-GType           gimp_docked_get_type            (void) G_GNUC_CONST;
-
 void            gimp_docked_title_changed       (GimpDocked   *docked);
 
 void            gimp_docked_set_aux_info        (GimpDocked   *docked,
diff --git a/app/widgets/gimpsessionmanaged.c b/app/widgets/gimpsessionmanaged.c
index 95e02ae2f3..9c750e970f 100644
--- a/app/widgets/gimpsessionmanaged.c
+++ b/app/widgets/gimpsessionmanaged.c
@@ -56,7 +56,7 @@ gimp_session_managed_get_aux_info (GimpSessionManaged *session_managed)
 
   g_return_val_if_fail (GIMP_IS_SESSION_MANAGED (session_managed), NULL);
 
-  iface = GIMP_SESSION_MANAGED_GET_INTERFACE (session_managed);
+  iface = GIMP_SESSION_MANAGED_GET_IFACE (session_managed);
 
   if (iface->get_aux_info)
     return iface->get_aux_info (session_managed);
@@ -80,7 +80,7 @@ gimp_session_managed_set_aux_info (GimpSessionManaged *session_managed,
 
   g_return_if_fail (GIMP_IS_SESSION_MANAGED (session_managed));
 
-  iface = GIMP_SESSION_MANAGED_GET_INTERFACE (session_managed);
+  iface = GIMP_SESSION_MANAGED_GET_IFACE (session_managed);
 
   if (iface->set_aux_info)
     iface->set_aux_info (session_managed, aux_info);
diff --git a/app/widgets/gimpsessionmanaged.h b/app/widgets/gimpsessionmanaged.h
index dfe675d9ad..ddb040e260 100644
--- a/app/widgets/gimpsessionmanaged.h
+++ b/app/widgets/gimpsessionmanaged.h
@@ -22,14 +22,10 @@
 #define __GIMP_SESSION_MANAGED_H__
 
 
-#define GIMP_TYPE_SESSION_MANAGED               (gimp_session_managed_get_type ())
-#define GIMP_SESSION_MANAGED(obj)               (G_TYPE_CHECK_INSTANCE_CAST ((obj), GIMP_TYPE_SESSION_MANAGED, GimpSessionManaged))
-#define GIMP_IS_SESSION_MANAGED(obj)            (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GIMP_TYPE_SESSION_MANAGED))
-#define GIMP_SESSION_MANAGED_GET_INTERFACE(obj) (G_TYPE_INSTANCE_GET_INTERFACE ((obj), GIMP_TYPE_SESSION_MANAGED, GimpSessionManagedInterface))
+#define GIMP_TYPE_SESSION_MANAGED (gimp_session_managed_get_type ())
+G_DECLARE_INTERFACE (GimpSessionManaged, gimp_session_managed, GIMP, SESSION_MANAGED, GtkWidget)
 
 
-typedef struct _GimpSessionManagedInterface GimpSessionManagedInterface;
-
 struct _GimpSessionManagedInterface
 {
   GTypeInterface base_iface;
@@ -41,8 +37,6 @@ struct _GimpSessionManagedInterface
 };
 
 
-GType              gimp_session_managed_get_type     (void) G_GNUC_CONST;
-
 GList            * gimp_session_managed_get_aux_info (GimpSessionManaged *session_managed);
 void               gimp_session_managed_set_aux_info (GimpSessionManaged *session_managed,
                                                       GList              *aux_info);
diff --git a/app/widgets/gimpwindowstrategy.c b/app/widgets/gimpwindowstrategy.c
index 5105133937..f721d7ca68 100644
--- a/app/widgets/gimpwindowstrategy.c
+++ b/app/widgets/gimpwindowstrategy.c
@@ -53,7 +53,7 @@ gimp_window_strategy_show_dockable_dialog (GimpWindowStrategy *strategy,
 
   g_return_val_if_fail (GIMP_IS_WINDOW_STRATEGY (strategy), NULL);
 
-  iface = GIMP_WINDOW_STRATEGY_GET_INTERFACE (strategy);
+  iface = GIMP_WINDOW_STRATEGY_GET_IFACE (strategy);
 
   if (iface->show_dockable_dialog)
     return iface->show_dockable_dialog (strategy,
diff --git a/app/widgets/gimpwindowstrategy.h b/app/widgets/gimpwindowstrategy.h
index 0c1b37aa81..f916bb157a 100644
--- a/app/widgets/gimpwindowstrategy.h
+++ b/app/widgets/gimpwindowstrategy.h
@@ -22,14 +22,10 @@
 #define __GIMP_WINDOW_STRATEGY_H__
 
 
-#define GIMP_TYPE_WINDOW_STRATEGY               (gimp_window_strategy_get_type ())
-#define GIMP_WINDOW_STRATEGY(obj)               (G_TYPE_CHECK_INSTANCE_CAST ((obj), GIMP_TYPE_WINDOW_STRATEGY, GimpWindowStrategy))
-#define GIMP_IS_WINDOW_STRATEGY(obj)            (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GIMP_TYPE_WINDOW_STRATEGY))
-#define GIMP_WINDOW_STRATEGY_GET_INTERFACE(obj) (G_TYPE_INSTANCE_GET_INTERFACE ((obj), GIMP_TYPE_WINDOW_STRATEGY, GimpWindowStrategyInterface))
+#define GIMP_TYPE_WINDOW_STRATEGY (gimp_window_strategy_get_type ())
+G_DECLARE_INTERFACE (GimpWindowStrategy, gimp_window_strategy, GIMP, WINDOW_STRATEGY, GObject)
 
 
-typedef struct _GimpWindowStrategyInterface GimpWindowStrategyInterface;
-
 struct _GimpWindowStrategyInterface
 {
   GTypeInterface base_iface;
@@ -43,8 +39,6 @@ struct _GimpWindowStrategyInterface
 };
 
 
-GType       gimp_window_strategy_get_type             (void) G_GNUC_CONST;
-
 GtkWidget * gimp_window_strategy_show_dockable_dialog (GimpWindowStrategy *strategy,
                                                        Gimp               *gimp,
                                                        GimpDialogFactory  *factory,
diff --git a/devel-docs/app/app-sections.txt b/devel-docs/app/app-sections.txt
index 4eab07841c..5ccb9a4736 100644
--- a/devel-docs/app/app-sections.txt
+++ b/devel-docs/app/app-sections.txt
@@ -7749,7 +7749,7 @@ GIMP_CONTAINER_VIEW
 GIMP_IS_CONTAINER_VIEW
 GIMP_TYPE_CONTAINER_VIEW
 gimp_container_view_interface_get_type
-GIMP_CONTAINER_VIEW_GET_INTERFACE
+GIMP_CONTAINER_VIEW_GET_IFACE
 </SECTION>
 
 <SECTION>
@@ -8139,7 +8139,7 @@ gimp_window_strategy_show_dockable_dialog
 GIMP_IS_WINDOW_STRATEGY
 GIMP_TYPE_WINDOW_STRATEGY
 GIMP_WINDOW_STRATEGY
-GIMP_WINDOW_STRATEGY_GET_INTERFACE
+GIMP_WINDOW_STRATEGY_GET_IFACE
 gimp_window_strategy_interface_get_type
 </SECTION>
 
@@ -8262,7 +8262,7 @@ gimp_dock_container_get_docks
 gimp_dock_container_get_ui_manager
 <SUBSECTION Standard>
 GIMP_DOCK_CONTAINER
-GIMP_DOCK_CONTAINER_GET_INTERFACE
+GIMP_DOCK_CONTAINER_GET_IFACE
 GIMP_IS_DOCK_CONTAINER
 GIMP_TYPE_DOCK_CONTAINER
 gimp_dock_container_interface_get_type
@@ -8370,7 +8370,7 @@ GIMP_DOCKED
 GIMP_IS_DOCKED
 GIMP_TYPE_DOCKED
 gimp_docked_interface_get_type
-GIMP_DOCKED_GET_INTERFACE
+GIMP_DOCKED_GET_IFACE
 </SECTION>
 
 <SECTION>
@@ -9662,7 +9662,7 @@ gimp_session_managed_set_aux_info
 <SUBSECTION Standard>
 GIMP_IS_SESSION_MANAGED
 GIMP_SESSION_MANAGED
-GIMP_SESSION_MANAGED_GET_INTERFACE
+GIMP_SESSION_MANAGED_GET_IFACE
 GIMP_TYPE_SESSION_MANAGED
 gimp_session_managed_interface_get_type
 </SECTION>