A computer is operated by displaying a window on a display device, where the window is an opaque window overlaid on the entirety of a system desktop that includes graphical representations of system controls and application controls. The window displays user interface elements of an application program executing on the computer, and also includes a portal region displaying an image of the system desktop including counterparts of the system controls and application controls. The computer provides user-controlled operation of the system controls and application controls based on simulated user interaction with the counterparts of the system controls and application controls in the portal region. The application program can effectively coordinate the use of the display by itself and by the system and other applications using the system desktop, relieving the user of this task.