Class StackingResource

source code

object --+    
         |    
  Resource --+
             |
            StackingResource

A stacking resource is a special kind of resource that can preempt the current owner. Resources are assigned to clients in order of arrival, this is, a new client attempting to grab will produce the former owner to be released. However, when the current owner released ownership will be passed back to the last owner.

This, clients are organised in a stack, where grabbing puts the client at the top, and releasing removes from wherever the client is in the stack. Because ownership can change even a client does not release, a client should not use the resource based on the result of the grab() method but instead use whatever indirect API the concrete resource provides to assign ownership.

Clients of a stacking resource can be prioritised to prevent preemption from a client with less priority. (For example, a modal dialog should not loose focus because of a normal window appearing.)