Deletion of an output window.
clear_window deletes all entries in the current output window. The window (background and edge) is reset to its original state. Parameters assigned to this window (e.g. with set_color, set_paint, etc.) remain unmodified. If the corresponding window is not active yet, you may activate it by set_window before calling clear_window.
clear_window(:::).
If an ouput window is active, then clear_window returns TRUE. If necessary an exception is raised.
open_window, open_textwindow, set_window
clear_rectangle, disp_rectangle1
open_window, open_textwindow, set_window