Incompatible Changes from GTK+-1.2 to GTK+-2.0:

* gtk_container_get_toplevels() was removed and replaced with
  gtk_window_list_toplevels(), which has different memory management 
  on the return value (gtk_window_list_toplevels() copies the GList
  and also references each widget in the list, so you have to
  g_list_free() the list after first unref'ing each list member).

* The gdk_time* functions have been removed. This functionality
  has been unused since the main loop was moved into GLib
  prior to 1.2. 

* The signature for GtkPrintFunc (used for gtk_item_factory_dump_items)
  has been changed to take a 'const gchar *' instead of 'gchar *', to
  match what we do for glib, and other similar cases.

* The detail arguments in the GtkStyleClass structure are now 'const gchar *'.

* gtk_paned_set_gutter_size() has been removed, since the small handle tab
  has been changed to include the entire area previously occupied by
  the gutter.

* GDK no longer selects OwnerGrabButtonMask for button presses. This means  
  that the automatic grab that occurs when the user presses a button
  will have owner_events = FALSE, so all events are redirected to the
  grab window, even events that would normally go to  other windows of the
  window's owner.

* GtkColorSelectionDialog has now been moved into it's own set of files,
  gtkcolorseldialog.c and gtkcolorseldialog.h.

* gtk_widget_shape_combine_mask() now keeps a reference count on the 
  mask pixmap that is passed in.

* Type system changes:
  - GTK_TYPE_OBJECT is not a fundamental type anymore. Type checks of the
    style (GTK_FUNDAMENTAL_TYPE (some_type) == GTK_TYPE_OBJECT)
    will not work anymore. As a replacement, (GTK_TYPE_IS_OBJECT (some_type))
    can be used now.
  - The following types vanished: GTK_TYPE_ARGS, GTK_TYPE_CALLBACK,
    GTK_TYPE_C_CALLBACK, GTK_TYPE_FOREIGN. The corresponding GtkArg
    fields and field access macros are also gone.
  - The following type aliases vanished: GTK_TYPE_FLAT_FIRST,
    GTK_TYPE_FLAT_LAST, GTK_TYPE_STRUCTURED_FIRST, GTK_TYPE_STRUCTURED_LAST.
  - The type macros GTK_TYPE_MAKE() and GTK_TYPE_SEQNO() vanished, use of
    GTK_FUNDAMENTAL_TYPE() is discouraged. Instead, the corresponding GType
    API should be used: G_TYPE_FUNDAMENTAL(), G_TYPE_DERIVE_ID(),
    G_TYPE_BRANCH_SEQNO(). Note that the GLib type system doesn't build new
    type ids based on a global incremental sequential number anymore, but
    numbers new type ids sequentially per fundamental type branch.
  - The following type functions vanished/were replaced:
    Old Function		 Replacement
    gtk_type_query()		 - being investigated -
    gtk_type_set_varargs_type()	 -
    gtk_type_get_varargs_type()	 -
    gtk_type_check_object_cast() g_type_check_instance_cast()
    gtk_type_check_class_cast()	 g_type_check_class_cast()
    gtk_type_describe_tree()	 -
    gtk_type_describe_heritage() -
    gtk_type_free()		 -
    gtk_type_children_types()	 g_type_children()
    gtk_type_set_chunk_alloc()	 GTypeInfo.n_preallocs
    gtk_type_register_enum()	 g_enum_register_static()
    gtk_type_register_flags()	 g_flags_register_static()
    gtk_type_parent_class()	 g_type_parent() / g_type_class_peek_parent()
    Use of g_type_class_ref() / g_type_class_unref() and g_type_class_peek()
    is recommended over usage of gtk_type_class().
    Use of g_type_register_static() / g_type_register_dynamic() is recommended
    over usage of gtk_type_unique().

* Object system changes:
  GtkObject derives from GObject, so is not the basic object type anymore.
  This imposes the following source incompatible changes:
  - GtkObject has no klass field anymore, an object's class can be retrived
    with the object's coresponding GTK_<OBJECT>_GET_CLASS (object) macro.
  - GtkObjectClass has no type field anymore, a class's type can be retrived
    with the GTK_CLASS_TYPE (class) macro.
  - GtkObjectClass does not introduce the finalize() and shutdown() methods
    anymore. While shutdown() is intended for GTK+ internal use only, finalize()
    is required by a variety of object implementations. GObjectClass.finalize
    should be overriden here, e.g.:
    static void gtk_label_finalize (GObject *gobject)
    {
      GtkLabel *label = GTK_LABEL (gobject);
      
      G_OBJECT_CLASS (parent_class)->finalize (object);
    }
    static void gtk_label_class_init (GtkLabelClass *class)
    {
      GObjectClass *gobject_class = G_OBJECT_CLASS (class);
      
      gobject_class->finalize = gtk_label_finalize;
    }

  - the GtkObject::destroy signal can now be emitted multiple times on an object.
    ::destroy implementations should check that make sure that they take this
    into account, by checking to make sure that resources are there before
    freeing them. For example:
    if (object->foo_data)
      { 
        g_free (object->foo_data);
        object->foo_data = NULL;
      }

    Also, ::destroy implementations have to release object references that
    the object holds. Code in finalize implementations such as:
    if (object->adjustment)
      {
        gtk_object_unref (object->adjustment);
        object->adjustment = NULL;
      }
    have to be moved into the ::destroy implementations. The reason for doing
    this is that all object reference cycles should be broken at destruction 
    time.
    
* Signal system changes:
  The Gtk 2.0 signal merly proxies the GSignal system now.
  For future usage, direct use of the GSignal API is recommended,
  this avoids significant performance hits where GtkArg structures
  have to be converted into GValues. For language bindings,
  GSignal+GClosure provide a much more flexible and convenient
  mechanism to hook into signal emissions or install class default
  handlers, so the old GtkSignal API for language bindings is not
  supported anymore.
  Functions that got removed in the Gtk signal API:
  gtk_signal_n_emissions(), gtk_signal_n_emissions_by_name(),
  gtk_signal_set_funcs(), gtk_signal_handler_pending_by_id(),
  gtk_signal_add_emission_hook(), gtk_signal_add_emission_hook_full(),
  gtk_signal_remove_emission_hook(), gtk_signal_query().
  gtk_signal_add_emission_hook(), gtk_signal_remove_emission_hook().
  Also, the GtkCallbackMarshal argument to gtk_signal_connect_full() is
  not supported anymore.
  For many of the removed functions, similar variants are available
  in the g_signal_* namespace.

- Inserting and deleting text in GtkEntry though functions such
  as gtk_entry_insert_text() now leave the cursor at its original
  position in the text instead of moving it to the location of
  the insertion/deletion.

- The ->label field of GtkFrame widgets has been removed. (As part of
  a change to allow the arbitrary widgets in the title position.) The
  text can now be retrieved with the new function gtk_frame_get_text().

- The 'font' and 'font_set' declarations in RC files are now ignored. There
  is a new 'font_name' field that holds the string form of a Pango font

- A number of types in GDK have become subclasses of GObject. For the
  most part, this should not break anyone's code. However, it's now 
  possible/encouraged to use g_object_ref()/g_object_unref() and other
  GObject features with these GDK types. The converted types are:
  GdkWindow, GdkDrawable, GdkPixmap, GdkImage, GdkGC, GdkDragContext,
  GdkColormap

- All drawables including pixmaps used to have a type tag, the 
  GdkWindowType enumeration, which included GDK_WINDOW_PIXMAP.
  GdkWindowType is now a property of GdkWindow _only_, and there is
  no GDK_WINDOW_PIXMAP. You can use the GDK_IS_PIXMAP() macro to see 
  if you have a pixmap, if you need to know that.

- GtkStyle and GtkRcStyle are now subclasses of GObject as well.  This
  requires fairly extensive changes to theme engines quite badly, but
  shouldn't affect most other code.

- xthickness/ythickness have moved from GtkStyleClass to GtkStyle
  (from class to instance). This gives themes a bit more flexibility
  and is generally more of the Right Thing. You can trivially fix
  your code with s/style->klass->xthickness/style->xthickness/g and 
  same for ythickness.

- If you were using private GDK types, they have been rearranged
  significantly. You shouldn't use private types. ;-) 

- The visual for a widget, and also the default visual is now derived
  from the colormap for the widget and the default colormap. 
  gtk_widget_set_visual(), gtk_widget_set_default_visual(), gtk_widget_push_visual() 
  and gtk_widget_pop_visual() now do nothing. Since the visual always
  had to match that of the colormap, it is safe to simply delete
  all references to these functions.

- A number of functions in GDK have been renamed for consistency and
  clarity. #defines to provide backwards compatibility have been
  included, but can be disabled by defineing GDK_DISABLE_COMPAT_H.

  #define gdk_draw_pixmap                gdk_draw_drawable
  #define gdk_draw_bitmap                gdk_draw_drawable

  #define gdk_window_get_size            gdk_drawable_get_size
  #define gdk_window_get_type            gdk_window_get_window_type
  #define gdk_window_get_colormap        gdk_drawable_get_colormap
  #define gdk_window_set_colormap        gdk_drawable_set_colormap
  #define gdk_window_get_visual          gdk_drawable_get_visual

  #define gdk_window_ref                 gdk_drawable_ref
  #define gdk_window_unref               gdk_drawable_unref
  #define gdk_bitmap_ref                 gdk_drawable_ref
  #define gdk_bitmap_unref               gdk_drawable_unref
  #define gdk_pixmap_ref                 gdk_drawable_ref
  #define gdk_pixmap_unref               gdk_drawable_unref

  #define gdk_gc_destroy                 gdk_gc_unref
  #define gdk_image_destroy              gdk_image_unref
  #define gdk_cursor_destroy             gdk_cursor_unref

  (Note that g_object_ref() and g_object_unref() may be used for all of
  the above.)

  #define gdk_window_copy_area(drawable,gc,x,y,source_drawable,source_x,source_y,width,height) \
     gdk_draw_pixmap(drawable,gc,source_drawable,source_x,source_y,x,y,width,height)

  #define gdk_rgb_get_cmap               gdk_rgb_get_colormap

- gdk_pixmap_foreign_new() no longer calls XFreePixmap() on the 
  pixmap when the GdkPixmap is finalized. This change corresponds
  to the behavior of gdk_window_foreign_new(), and fixes a lot
  of problems with code where the pixmap wasn't supposed to be
  freed. If XFreePixmap() is needed, it can be done using the
  destroy-notification facilities of g_object_set_data().

-  GtkProgress/GtkProgressBar had serious problems in GTK 1.2.
 
  - Only 3 or 4 functions are really needed for 95% of progress  
    interfaces; GtkProgress[Bar] had about 25 functions, and 
    didn't even include these 3 or 4.
  - In activity mode, the API involves setting the adjustment 
    to any random value, just to have the side effect of 
    calling the progress bar update function - the adjustment
    is totally ignored in activity mode
  - You set the activity step as a pixel value, which means to 
    set the activity step you basically need to connect to 
    size_allocate
  - There are ctree_set_expander_style()-functions, to randomly 
    change look-and-feel for no good reason
  - The split between GtkProgress and GtkProgressBar makes no sense 
    to me whatsoever.
  
 This was a big wart on GTK and made people waste lots of time,
 both learning and using the interface.
 
 So, we have added what we feel is the correct API, and marked all the
 rest deprecated. However, the changes are 100% backward-compatible and
 should break no existing code.

 The following 5 functions are the new programming interface and you 
 should consider changing your code to use them:
 
  void       gtk_progress_bar_pulse                (GtkProgressBar *pbar);
  void       gtk_progress_bar_set_text             (GtkProgressBar *pbar,
                                                    const gchar    *text);
  void       gtk_progress_bar_set_fraction         (GtkProgressBar *pbar,
                                                    gfloat          fraction);

  void       gtk_progress_bar_set_pulse_step       (GtkProgressBar *pbar,
                                                    gfloat          fraction);
  void       gtk_progress_bar_set_orientation      (GtkProgressBar *pbar,
						    GtkProgressBarOrientation orientation);


- GtkMenuPositionFunc has a new parameter push_in which controls how
  menus placed outside the screen is handled. If this is set to true and
  part of the menu is outside the screen then Gtk+ pushes it into the visible
  area. Otherwise the menu is cut of at the end of the visible screen area.

  Regardles of what happens to the size of the menu, the result is always
  that the items are placed in the same place as if the menu was placed
  outside the screen, using menu scrolling if necessary.
  
  
 
