The fade-in/out animations of the notification-bubbles rendered by notify-osd are indeed explicitly controlled by notify-osd. This way it works under compiz and metacity in the same way, is predictable for the user (from a user-interaction point-of-view) and can be fine-tuned to match all possible corner-cases (from the designers point-of-view). Another fact to note is that some people might have the animation-pluing disabled. What should we do in that case? Relying on external components, apart from desktop-compositing, is not a good idea. This would make implementing the notification spec even harder.
The fade-in/out animations of the notification- bubbles rendered by notify-osd are indeed explicitly controlled by notify-osd. This way it works under compiz and metacity in the same way, is predictable for the user (from a user-interaction point-of-view) and can be fine-tuned to match all possible corner-cases (from the designers point-of-view). Another fact to note is that some people might have the animation-pluing disabled. What should we do in that case? Relying on external components, apart from desktop- compositing, is not a good idea. This would make implementing the notification spec even harder.