Although I do not know your exact scenario, the
Stock Trader Reference Implementation
has some similar functionality. Basically, when you click on the Buy/Sell buttons, a new view is added to an empty region (we will call it Region0) in the
Shell. This view has nothing more than a Region (we will call it Region1) and two buttons. Region0 becomes visible when a view has to be added to Region1, and stops showing it when Region1 is emptied of views.
You can check the OrdersController class to see how this is done.
Perhaps, with a similar approach but using an animation you could be able to achieve your requirement.
Another approach could be using a region Behavior. As you probably know, there is no out-of-the-box way to be aware in the
Shell (which is the control that has the regions usually), when a view has been added/removed from a region. Therefore, as you mentioned, you could create a custom
RegionBehavior that enables you to do this.
The following article in the Prism-v2 documentation provides more details about
RegionBehaviors and how to create custom ones:
Please let me know if this helps.