Question

Is it possible to create new signals in Python GTK+ ?

I’d like a skeleton code example, please.

Answer 1

An excerpt:

Creating your own signals

The other thing you probably want to
use when subclassing GObject is define
custom signals. You can create your
own signals that can be emitted so
users of your class can connect to
them.

When a signal is emitted a set of
closures will be executed. A closure
is an abstraction of the callback
concept. A closure is the callback
itself (a function pointer), the user
data (it will be the last parameter to
the callback) and another function for
cleanup issues, which will not be
discussed in this document.

For the sake of this article you don’t
really need to know the difference
between a callback and a closure so
both terms will be used. But be
advised that this is not totally
correct.

As we said before, when a signal is
emitted, a set of closures will be
executed. One of them is the same one
for all the instances of this class
and hence its name: the class closure,
and the other ones are custom user
callbacks. Note that not all the
signals need to have a class closure
because it is optional.

From, http://www.pygtk.org/articles/subclassing-gobject/sub-classing-gobject-in-python.htm, hope that helps. There is example code on the site and here , a snippet:

import pygtk
pygtk.require('2.0')
import gobject

class Car(gobject.GObject):
    __gproperties__ = {
        'fuel' : (gobject.TYPE_FLOAT, 'fuel of the car',
                  'amount of fuel that remains in the tank',
                  0, 60, 50, gobject.PARAM_READWRITE)
        }

    __gsignals__ = {
        'engine-started' : (gobject.SIGNAL_RUN_LAST, gobject.TYPE_NONE,
                            (gobject.TYPE_FLOAT,))
        }

    def __init__(self):
        gobject.GObject.__init__(self)
        self.fuel = 50

    def do_get_property(self, property):
        if property.name == 'fuel':
            return self.fuel
        else:
            raise AttributeError, 'unknown property %s' % property.name

    def do_set_property(self, property, value):
        if property.name == 'fuel':
            self.fuel = value
        else:
            raise AttributeError, 'unknown property %s' % property.name

    def do_engine_started(self, remaining_fuel):
        print '***** Beginning of class closure *****'
        print 'The engine is ready and we still have %f of fuel' % self.fuel
        print '***** End of class closure *****'

    def start(self):
        self.emit('engine-started', self.get_property('fuel'))

gobject.type_register(Car)