This option uses a different ZOOM cursor, a rectangular area drawn
using the midle button of the mouse. Clicking outside the area with the
middle button will resize the rectangle. By keeping the middle button
pressed, the shape will follow the mouse. To drag the shape on another
part of the screen, click with the middle button inside the shape and
keep the button pressed while dragging the shape. Button 1 will perform
the zoom (in an auxiliary zoom window), button 3 exits.