1. 五花八门的事件

除了上个章节所说的“信号发生处理机制”，“X事件响应机制”里还有一大堆的“事件”：“回调函数”也是用来响应这些事件的。这些事件是：

  event
  button_press_event
  button_release_event
  scroll_event
  motion_notify_event
  delete_event
  destroy_event
  expose_event
  key_press_event
  key_release_event
  enter_notify_event
  leave_notify_event
  configure_event
  focus_in_event
  focus_out_event
  map_event
  unmap_event
  property_notify_event
  selection_clear_event
  selection_request_event
  selection_notify_event
  proximity_in_event
  proximity_out_event
  visibility_notify_event
  client_event
  no_expose_event
  window_state_even

为了使我们的“callback”能够响应这些事件，就要用到connect()，就像上个章节所说的那样，把事件的名称作为name参数传入“callback”。用于响应“事件”的callback和响应“事件信号”的callback是不一样的。

  def callback_func(widget, event, callback_data ):

  def callback_meth(self, widget, event, callback_data ):
  {{{

  GdkEvent是一个python对象，是他的type属性告诉我们到底发生了什么“事件”。“事件”的另外一些属性依赖于type属性。type的值一般有这么一些：
  {{{
    NOTHING
  DELETE
  DESTROY
  EXPOSE
  MOTION_NOTIFY
  BUTTON_PRESS
  _2BUTTON_PRESS
  _3BUTTON_PRESS
  BUTTON_RELEASE
  KEY_PRESS
  KEY_RELEASE
  ENTER_NOTIFY
  LEAVE_NOTIFY
  FOCUS_CHANGE
  CONFIGURE
  MAP
  UNMAP
  PROPERTY_NOTIFY
  SELECTION_CLEAR
  SELECTION_REQUEST
  SELECTION_NOTIFY
  PROXIMITY_IN
  PROXIMITY_OUT
  DRAG_ENTER
  DRAG_LEAVE
  DRAG_MOTION
  DRAG_STATUS
  DROP_START
  DROP_FINISHED
  CLIENT_EVENT
  VISIBILITY_NOTIFY
  NO_EXPOSE
  SCROLL
  WINDOW_STATE
  SETTING

以上这些东东归gtk.gdk管，比如gtk.gtk.DRAG_ENTER。

下面我们把callback和event边起来，就像这样：

button.connect("button_press_event", button_press_callback)

上面的button是一个GtkWidget。这样，当鼠标在这个button按了一下，button_press_callback就被调用了。这个button_press_callback的定义可能是这样的：

def button_press_callback(widget, event, data ):

这个callback的返回值决定了还要不要继续处理其它事件，返回True表示打完收功，而False表示继续standby。想知道更详细，请看这里：Advanced Event and Signal Handling

The GDK selection and drag-and-drop APIs also emit a number of events which are reflected in GTK+ by signals. See Section 22.3.2, “Signals On the Source Widget” and Section 22.3.4, “Signals On the Destination Widget” for details on the signatures of the callback functions for these signals:

selection_received
selection_get
drag_begin_event
drag_end_event
drag_data_delete
drag_motion
drag_drop
drag_data_get
drag_data_received