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Gtk+/Gnome Application Development
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The GtkWidgetClass Struct

There are a truly huge number of class functions in GtkWidgetClass. Thankfully, in most cases you only have to override a few of them. Here is the code:


typedef struct _GtkWidgetClass GtkWidgetClass;

struct _GtkWidgetClass
{
  GtkObjectClass parent_class;
  
  guint activate_signal;

  guint set_scroll_adjustments_signal;
  
  /* Basics */
  void (* show)                (GtkWidget      *widget);
  void (* show_all)            (GtkWidget      *widget);
  void (* hide)                (GtkWidget      *widget);
  void (* hide_all)            (GtkWidget      *widget);
  void (* map)                 (GtkWidget      *widget);
  void (* unmap)               (GtkWidget      *widget);
  void (* realize)             (GtkWidget      *widget);
  void (* unrealize)           (GtkWidget      *widget);
  void (* draw)                (GtkWidget      *widget,
                                GdkRectangle   *area);
  void (* draw_focus)          (GtkWidget      *widget);
  void (* draw_default)        (GtkWidget      *widget);
  void (* size_request)        (GtkWidget      *widget,
                                GtkRequisition *requisition);
  void (* size_allocate)       (GtkWidget      *widget,
                                GtkAllocation  *allocation);
  void (* state_changed)       (GtkWidget      *widget,
                                GtkStateType    previous_state);
  void (* parent_set)          (GtkWidget      *widget,
                                GtkWidget      *previous_parent);
  void (* style_set)           (GtkWidget      *widget,
                                GtkStyle       *previous_style);
  
  /* Accelerators */
  gint (* add_accelerator)     (GtkWidget      *widget,
                                guint           accel_signal_id,
                                GtkAccelGroup  *accel_group,
                                guint           accel_key,
                                GdkModifierType accel_mods,
                                GtkAccelFlags   accel_flags);
  void (* remove_accelerator)  (GtkWidget      *widget,
                                GtkAccelGroup  *accel_group,
                                guint           accel_key,
                                GdkModifierType accel_mods);

  /* Explicit focus */
  void (* grab_focus)          (GtkWidget      *widget);
  
  /* Events */
  gint (* event)                   (GtkWidget          *widget,
                                    GdkEvent           *event);
  gint (* button_press_event)      (GtkWidget          *widget,
                                    GdkEventButton     *event);
  gint (* button_release_event)    (GtkWidget          *widget,
                                    GdkEventButton     *event);
  gint (* motion_notify_event)     (GtkWidget          *widget,
                                    GdkEventMotion     *event);
  gint (* delete_event)            (GtkWidget          *widget,
                                    GdkEventAny        *event);
  gint (* destroy_event)           (GtkWidget          *widget,
                                    GdkEventAny        *event);
  gint (* expose_event)            (GtkWidget          *widget,
                                    GdkEventExpose     *event);
  gint (* key_press_event)         (GtkWidget          *widget,
                                    GdkEventKey        *event);
  gint (* key_release_event)       (GtkWidget          *widget,
                                    GdkEventKey        *event);
  gint (* enter_notify_event)      (GtkWidget          *widget,
                                    GdkEventCrossing   *event);
  gint (* leave_notify_event)      (GtkWidget          *widget,
                                    GdkEventCrossing   *event);
  gint (* configure_event)         (GtkWidget          *widget,
                                    GdkEventConfigure  *event);
  gint (* focus_in_event)          (GtkWidget          *widget,
                                    GdkEventFocus      *event);
  gint (* focus_out_event)         (GtkWidget          *widget,
                                    GdkEventFocus      *event);
  gint (* map_event)               (GtkWidget          *widget,
                                    GdkEventAny        *event);
  gint (* unmap_event)             (GtkWidget          *widget,
                                    GdkEventAny        *event);
  gint (* property_notify_event)   (GtkWidget          *widget,
                                    GdkEventProperty   *event);
  gint (* selection_clear_event)   (GtkWidget          *widget,
                                    GdkEventSelection  *event);
  gint (* selection_request_event) (GtkWidget          *widget,
                                    GdkEventSelection  *event);
  gint (* selection_notify_event)  (GtkWidget          *widget,
                                    GdkEventSelection  *event);
  gint (* proximity_in_event)      (GtkWidget          *widget,
                                    GdkEventProximity  *event);
  gint (* proximity_out_event)     (GtkWidget          *widget,
                                    GdkEventProximity  *event);
  gint (* visibility_notify_event)  (GtkWidget         *widget,
                                     GdkEventVisibility *event);
  gint (* client_event)            (GtkWidget          *widget,
                                    GdkEventClient     *event);
  gint (* no_expose_event)         (GtkWidget          *widget,
                                    GdkEventAny        *event);

  /* Selection */
  void (* selection_get)           (GtkWidget          *widget,
                                    GtkSelectionData   *selection_data,
                                    guint               info,
                                    guint               time);
  void (* selection_received)      (GtkWidget          *widget,
                                    GtkSelectionData   *selection_data,
                                    guint               time);

  /* Source side drag signals */
  void (* drag_begin)              (GtkWidget          *widget,
                                    GdkDragContext     *context);
  void (* drag_end)                (GtkWidget          *widget,
                                    GdkDragContext     *context);
  void (* drag_data_get)           (GtkWidget          *widget,
                                    GdkDragContext     *context,
                                    GtkSelectionData   *selection_data,
                                    guint               info,
                                    guint               time);
  void (* drag_data_delete)        (GtkWidget          *widget,
                                    GdkDragContext     *context);

  /* Target side drag signals */
  void (* drag_leave)              (GtkWidget          *widget,
                                    GdkDragContext     *context,
                                    guint               time);
  gboolean (* drag_motion)         (GtkWidget          *widget,
                                    GdkDragContext     *context,
                                    gint                x,
                                    gint                y,
                                    guint               time);
  gboolean (* drag_drop)           (GtkWidget          *widget,
                                    GdkDragContext     *context,
                                    gint                x,
                                    gint                y,
                                    guint               time);
  void (* drag_data_received)      (GtkWidget          *widget,
                                    GdkDragContext     *context,
                                    gint                x,
                                    gint                y,
                                    GtkSelectionData   *selection_data,
                                    guint               info,
                                    guint               time);
  
  /* Action signals */
  void (* debug_msg)               (GtkWidget          *widget,
                                    const gchar        *string);

  /* Padding for future expansion */
  GtkFunction pad1;
  GtkFunction pad2;
  GtkFunction pad3;
  GtkFunction pad4;
};
      

Most of the functions in GtkWidgetClass are registered as default handlers for signals. The exceptions are show_all and hide_all, which are class functions only. Of course, GtkWidgetClass inherits the five class functions and single signal ("destroy") from GtkObjectClass. This chapter will describe the important methods in more detail; also, the section called Events in the chapter called GDK Basics is important for understanding the event methods. the section called GtkWidget In Detail describes the default implementation of each method in some detail.

Gtk+/Gnome Application Development
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