Event @ GTK + 2.0 Chinese tutorial serialization

Event

In addition to the signal mechanism described above, there is also a setEvents
Reflects x event mechanisms. Callback functions can be connected to these events. These events are:

• Event
  
• Button_press_event
  
• Button_release_event
  
• Scroll_event
  
• Motion_policy_event
  
• Delete_event
  
• Destroy_event
  
• Expose_event
  
• Key_press_event
  
• Key_release_event
  
• Enter_policy_event
  
• Leave_policy_event
  
• Configure_event
  
• Focus_in_event
  
• Focus_out_event
  
• Map_event
  
• Unmap_event
  
• Property_policy_event
  
• Selection_clear_event
  
• Selection_request_event
  
• Selection_policy_event
  
• Proximity_in_event
  
• Proximity_out_event
  
• Visibility_policy_event
  
• Client_event
  
• No_expose_event
  
• Window_state_event
  

To connect a callback function to one of these events, you use the g_signal_connect () function, as described earlier, using one of the above event namesName
Parameters. The Event Callback Function is slightly different from the signal callback function:

gint callback_func( GtkWidget *widget, GdkEvent *event, gpointer callback_data );

Gdkevent is a CUnion
Structure. Its type depends on the event in the preceding event. Each possible type hasType
Members. The rest of the event structure depends on the event type. Possible values of the type include:

GDK_NOTHING GDK_DELETE GDK_DESTROY GDK_EXPOSE GDK_MOTION_NOTIFY GDK_BUTTON_PRESS GDK_2BUTTON_PRESS GDK_3BUTTON_PRESS GDK_BUTTON_RELEASE GDK_KEY_PRESS GDK_KEY_RELEASE GDK_ENTER_NOTIFY GDK_LEAVE_NOTIFY GDK_FOCUS_CHANGE GDK_CONFIGURE GDK_MAP GDK_UNMAP GDK_PROPERTY_NOTIFY GDK_SELECTION_CLEAR GDK_SELECTION_REQUEST GDK_SELECTION_NOTIFY GDK_PROXIMITY_IN GDK_PROXIMITY_OUT GDK_DRAG_ENTER GDK_DRAG_LEAVE GDK_DRAG_MOTION GDK_DRAG_STATUS GDK_DROP_START GDK_DROP_FINISHED GDK_CLIENT_EVENT GDK_VISIBILITY_NOTIFY GDK_NO_EXPOSE GDK_SCROLL GDK_WINDOW_STATE GDK_SETTING

Therefore, to connect a callback function to one of these events, we will use:

g_signal_connect (G_OBJECT (button), "button_press_event", G_CALLBACK (button_press_callback), NULL);

It is assumed thatButton
Is a button component. The button_press_callback () function is called when the mouse is placed on the button and clicked. This function should be declared:

static gint button_press_callback( GtkWidget *widget, GdkEventButton *event, gpointer data );

Note that we can declare the second parameter typeGdkeventbutton
Because we know which type of event will happen.

The return value of this function indicates whether the event should be further transmitted by the GTK event processor. Returns true to indicate that the event has been processed and should not be further propagated. Returns false to continue normal event processing. For details, see
Advanced event and signal processing
This chapter.

For details about gdkevent data types, see Appendix gdk event types
.

The gdk selection area and drag-and-drop interface functions also issue many events, which are reflected by signals in GTK. For details about the following signals, see the signals on the source component.
And signal on the target component
These two chapters:

• Selection_received
• Selection_get
• Drag_begin_event
• Drag_end_event
• Drag_data_delete
• Drag_motion
• Drag_drop
• Drag_data_get
• Drag_data_received

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