Index: app/widgets/gimpdockbook.c
===================================================================
--- app/widgets/gimpdockbook.c	(revision 23554)
+++ app/widgets/gimpdockbook.c	(working copy)
@@ -60,6 +60,7 @@ enum
 };
 
 
+static void      gimp_dockbook_dispose          (GObject        *object);
 static void      gimp_dockbook_finalize         (GObject        *object);
 
 static void      gimp_dockbook_style_set        (GtkWidget      *widget,
@@ -83,11 +84,23 @@ static void      gimp_dockbook_tab_drag_
 static void      gimp_dockbook_tab_drag_end     (GtkWidget      *widget,
                                                  GdkDragContext *context,
                                                  GimpDockable   *dockable);
+
+static void      gimp_dockbook_tab_drag_leave   (GtkWidget      *widget,
+                                                 GdkDragContext *context,
+                                                 guint           time,
+                                                 GimpDockable   *dockable);
+static gboolean  gimp_dockbook_tab_drag_motion  (GtkWidget      *widget,
+                                                 GdkDragContext *context,
+                                                 gint            x,
+                                                 gint            y,
+                                                 guint           time,
+                                                 GimpDockable   *dockable);
 static gboolean  gimp_dockbook_tab_drag_drop    (GtkWidget      *widget,
                                                  GdkDragContext *context,
                                                  gint            x,
                                                  gint            y,
                                                  guint           time);
+
 static gboolean  gimp_dockbook_tab_drag_expose  (GtkWidget      *widget,
                                                  GdkEventExpose *event);
 
@@ -140,6 +153,7 @@ gimp_dockbook_class_init (GimpDockbookCl
                   G_TYPE_NONE, 1,
                   GIMP_TYPE_DOCKABLE);
 
+  object_class->dispose     = gimp_dockbook_dispose;
   object_class->finalize    = gimp_dockbook_finalize;
 
   widget_class->style_set   = gimp_dockbook_style_set;
@@ -180,6 +194,21 @@ gimp_dockbook_init (GimpDockbook *dockbo
 }
 
 static void
+gimp_dockbook_dispose (GObject *object)
+{
+  GimpDockbook *dockbook = GIMP_DOCKBOOK (object);
+
+  if (dockbook->tab_hover_timeout)
+    {
+      g_source_remove (dockbook->tab_hover_timeout);
+      dockbook->tab_hover_timeout  = 0;
+      dockbook->tab_hover_dockable = NULL;
+    }
+
+  G_OBJECT_CLASS (parent_class)->dispose (object);
+}
+
+static void
 gimp_dockbook_finalize (GObject *object)
 {
   GimpDockbook *dockbook = GIMP_DOCKBOOK (object);
@@ -359,6 +388,13 @@ gimp_dockbook_remove (GimpDockbook *dock
 
   g_object_ref (dockable);
 
+  if (dockbook->tab_hover_dockable == dockable)
+    {
+      g_source_remove (dockbook->tab_hover_timeout);
+      dockbook->tab_hover_timeout  = 0;
+      dockbook->tab_hover_dockable = NULL;
+    }
+
   dockable->dockbook = NULL;
 
   gimp_dockable_set_context (dockable, NULL);
@@ -479,9 +515,15 @@ gimp_dockbook_get_tab_widget (GimpDockbo
                     dockable);
 
   gtk_drag_dest_set (GTK_WIDGET (tab_widget),
-                     GTK_DEST_DEFAULT_ALL,
+                     GTK_DEST_DEFAULT_DROP,
                      dialog_target_table, G_N_ELEMENTS (dialog_target_table),
                      GDK_ACTION_MOVE);
+  g_signal_connect (tab_widget, "drag-leave",
+                    G_CALLBACK (gimp_dockbook_tab_drag_leave),
+                    dockable);
+  g_signal_connect (tab_widget, "drag-motion",
+                    G_CALLBACK (gimp_dockbook_tab_drag_motion),
+                    dockable);
   g_signal_connect (tab_widget, "drag-drop",
                     G_CALLBACK (gimp_dockbook_tab_drag_drop),
                     dockbook);
@@ -532,6 +574,9 @@ gimp_dockbook_drop_dockable (GimpDockboo
   return FALSE;
 }
 
+
+/*  tab DND source side  */
+
 static void
 gimp_dockbook_tab_drag_begin (GtkWidget      *widget,
                               GdkDragContext *context,
@@ -604,6 +649,100 @@ gimp_dockbook_tab_drag_end (GtkWidget   
   gtk_widget_set_sensitive (GTK_WIDGET (dockable), TRUE);
 }
 
+
+/*  tab DND target side  */
+
+static void
+gimp_dockbook_tab_drag_leave (GtkWidget      *widget,
+                              GdkDragContext *context,
+                              guint           time,
+                              GimpDockable   *dockable)
+{
+  GimpDockbook *dockbook = dockable->dockbook;
+
+  if (dockbook->tab_hover_timeout)
+    {
+      g_source_remove (dockbook->tab_hover_timeout);
+      dockbook->tab_hover_timeout  = 0;
+      dockbook->tab_hover_dockable = NULL;
+    }
+
+  gtk_drag_unhighlight (widget);
+}
+
+static gboolean
+gimp_dockbook_tab_hover_timeout (GimpDockbook *dockbook)
+{
+  gint page_num;
+
+  page_num = gtk_notebook_page_num (GTK_NOTEBOOK (dockbook),
+                                    GTK_WIDGET (dockbook->tab_hover_dockable));
+  gtk_notebook_set_current_page (GTK_NOTEBOOK (dockbook), page_num);
+
+  dockbook->tab_hover_timeout  = 0;
+  dockbook->tab_hover_dockable = NULL;
+
+  return FALSE;
+}
+
+static gboolean
+gimp_dockbook_tab_drag_motion (GtkWidget      *widget,
+                               GdkDragContext *context,
+                               gint            x,
+                               gint            y,
+                               guint           time,
+                               GimpDockable   *dockable)
+{
+  GimpDockbook  *dockbook = dockable->dockbook;
+  GtkTargetList *target_list;
+  GdkAtom        target_atom;
+  guint          unused;
+
+  if (! dockbook->tab_hover_timeout ||
+      dockbook->tab_hover_dockable != dockable)
+    {
+      gint page_num;
+
+      if (dockbook->tab_hover_timeout)
+        {
+          g_source_remove (dockbook->tab_hover_timeout);
+          dockbook->tab_hover_timeout  = 0;
+          dockbook->tab_hover_dockable = NULL;
+        }
+
+      page_num = gtk_notebook_page_num (GTK_NOTEBOOK (dockbook),
+                                        GTK_WIDGET (dockable));
+
+      if (page_num != gtk_notebook_get_current_page (GTK_NOTEBOOK (dockbook)))
+        {
+          dockbook->tab_hover_timeout =
+            g_timeout_add (500, (GSourceFunc) gimp_dockbook_tab_hover_timeout,
+                           dockbook);
+          dockbook->tab_hover_dockable = dockable;
+        }
+    }
+
+  target_list = gtk_drag_dest_get_target_list (widget);
+  target_atom = gtk_drag_dest_find_target (widget, context, target_list);
+
+#ifdef __GNUC__
+#warning Remove "unused" as soon as we depend on GTK+ >= 2.12.1
+#endif
+  if (gtk_target_list_find (target_list, target_atom, &unused))
+    {
+      gdk_drag_status (context, GDK_ACTION_MOVE, time);
+      gtk_drag_highlight (widget);
+    }
+  else
+    {
+      gdk_drag_status (context, 0, time);
+      gtk_drag_unhighlight (widget);
+    }
+
+  /*  always return TRUE so drag_leave() is called  */
+  return TRUE;
+}
+
 static gboolean
 gimp_dockbook_tab_drag_drop (GtkWidget      *widget,
                              GdkDragContext *context,
Index: app/widgets/gimpdockbook.h
===================================================================
--- app/widgets/gimpdockbook.h	(revision 23554)
+++ app/widgets/gimpdockbook.h	(working copy)
@@ -42,6 +42,9 @@ struct _GimpDockbook
 
   GimpDock      *dock;
   GimpUIManager *ui_manager;
+
+  guint          tab_hover_timeout;
+  GimpDockable  *tab_hover_dockable;
 };
 
 struct _GimpDockbookClass