2.3. Events
In addition to the signal mechanism described
above, there is a set of events that reflect the X event mechanism.
Callbacks may also be attached to these events. These events are:
- event
- button_press_event
- button_release_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
- drag_begin_event
- drag_request_event
- drag_end_event
- drop_enter_event
- drop_leave_event
- drop_data_available_event
- other_event
In order to connect a callback function to
one of these events you use the method connect()
, as described above, using one of the above event names as the name
parameter. The callback function (or method) for events has a slightly different
form than that for signals:
def callback_func(widget, event, callback_data ):
def callback_meth(self, widget, event, callback_data ):
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GdkEvent is a python object type whose type
attribute will indicate which of the above events has occurred. The other
attributes of the event will depend upon the type of the event. Possible values
for the type are:
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_BEGIN
DRAG_REQUEST
DROP_ENTER
DROP_LEAVE
DROP_DATA_AVAIL
CLIENT_EVENT
VISIBILITY_NOTIFY
NO_EXPOSE
OTHER_EVENT # Deprecated, use filters instead
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These values are defined in the GDK.py module; use "import GDK" to access
these definitions. (And don't forget to specify the GDK. prefix.)
So, to connect a callback function to one
of these events we would use something like:
button.connect("button_press_event", button_press_callback)
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This assumes that button is a GtkButton
widget. Now, when the mouse is over the button and a mouse button is pressed,
the function button_press_callback will be called. This function
may be defined as:
def button_press_callback(widget, event, data ):
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The value returned from this function indicates
whether the event should be propagated further by the GTK event handling
mechanism. Returning gtk.TRUE indicates that the event has been handled,
and that it should not propagate further. Returning gtk.FALSE continues the
normal event handling. See the section on
Advanced Event and Signal Handling
for more details on this propagation process.