1. An image forming apparatus comprising: an application on a framework that is separated into a core logic portion handling basic processing and a user interface frame portion handling rendering processing and operates; and a controller that executes the application and the framework, wherein the core logic portion is implemented with an application programming interface defined by the framework, and the application programming interface includes a before-the-fact notification indicative of that a window of the application is changed to a display state as a result that another window in an upper layer is changed to a non-display state.