To catch mouse release, you must enable gtk.gdk.BUTTON_RELEASE_MASK but also gtk.gdk.BUTTON_PRESS_MASK !

So

mywidget.add_events(gtk.gdk.BUTTON_RELEASE_MASK)
mywidget.connect("button_release_event", self.smart_function)

won't do, while

mywidget.add_events(gtk.gdk.BUTTON_RELEASE_MASK | gtk.gdk.BUTTON_PRESS_MASK)
mywidget.connect("button_release_event", self.smart_function)

will.

According to the laconic official documentation and on the tutorial, the goal of gtk.gdk.POINTER_MOTION_HINT_MASK is to send you a motion event and then not send another until you call mywidget.get_pointer(), so that events don't keep queuing waiting for you to handle them.

However, this is plainly false in pygtk 2.13.0, where instead:

• if you only add gtk.gdk.POINTER_MOTION_HINT_MASK to your event mask, you handler for “motion_notify_event” is never called,
• if you instead add gtk.gdk.POINTER_MOTION_HINT_MASK | gtk.gdk.POINTER_MOTION_MASK , your handler is called lots of times, even if you don't call get_pointer()

There are 3 possible explanations:

1. pygtk looks if you are calling get_pointer into you handler, but if you don't and the handler ends execution, assumes that you are just ready for a new event (quite arbitrary and useless, since then pygtk could just
2. documentation is wrong/outdated
3. recent pygtk versions are buggy

I see 2 or 3 as more probable, because the widget provided in this article currently doesn't work.