An API and method for processing a user interface event is provided. The user interface event may take place in any environment of a software application, and may result from any type of user or software action. An embodiment also provides a framework for customizing the processing of a user interface event without the need to maintain accountability of computer states. In the method, an application process user interface event is processed using an operating system process. A user interface event is received by the application process by way of a user interface. A software component adapted to process the user interface event is pushed onto a memory stack by the operating system process. The operating system process processes the user interface event using the software component, and pops the software component from the memory stack.