Abstract: An application programming interface is provided by an operating system that includes a direct composition engine. The composition engine maintains a data structure that represents the display objects to be rendered on a desktop display. The application programming interface allows an application to write data to the data structure to update the display object, such as a window, for the application. Thus, multiple applications can update their respective display objects in this data structure. The direct composition engine is an operating system level process, presented to user-level processes as a service of the operating system. By having an operating system level process, performance standards can be maintained. The application programming interface also allows applications to provide display information that can be rendered more efficiently by the operating system than by the application.