leave_notify_event and enter_notify_event emitted on left click of button?

[Tim Flechtner <timf trdlnk com>]

hello,
 i'm trying to debug a problem i'm having, and i noticed that when i 
left click on a Gtk::Button, the leave_notify_event and 
enter_notify_event are emitted.  this seems odd to me.  does anyone know 
if this is intentional (and if so, why)?

thanks!
-tim