window ->redraw: [area]Redraw the entire window or some area of it. This method is normally
invoked automatically if the window is opened on the display or part of
it is exposed after it has been obscured by other windows.
PCE is designed to take care of all visual side-effects
automatically, so the user should never have to invoke methods
explicitly. An exception on this rule are the decorations (scrollbars
and label) of the window. If these are changed this method needs to be
called explicitly to update the window.
