right button_press_event triggers leave_notify?

[Markus Lausser <sgop users sourceforge net>]

Hello,

When right clicking a drawing area:

  gtk_widget_set_events(drawingarea,
                        GDK_EXPOSURE_MASK | 
                        GDK_LEAVE_NOTIFY_MASK |
                        GDK_POINTER_MOTION_MASK |
                        GDK_BUTTON1_MOTION_MASK |
                        GDK_BUTTON_PRESS_MASK |
                        GDK_BUTTON_RELEASE_MASK);

i receive a leave_notify event:

 [...]
 Gdk-Message: motion notify: window: 81789150 x,y: 226 255 hint: false
 Gdk-Message: motion notify: window: 81789150 x,y: 227 255 hint: false
 Gdk-Message: leave notify: window: 81789150 detail: 0 subwin: 0
 Gdk-Message: enter notify: window: 81788931 detail: 2 subwin: 0
 Gdk-Message: leave notify: window: 81788931 detail: 2 subwin: 0
 Gdk-Message: button press: window: 81789150 x,y: 227 255  button: 3
 Gdk-Message: button release: window: 81789150  x,y: 227 255  button: 3

Why is that? Is there any way to prevent this?
..using gtk+-2.2.1

Markus.