WINDOW_VP displays a new portion of the specified viewport.
---->(WINDOW_VP)---|viewport|----|point 1|---|point 2|---->
Two points are specified to define the box. The X and Y values of the points must be in the range 0 to 1. The box may need to be expanded in one direction to fit the shape of the viewport.
If you interrupt this action, the menu button is greyed out until the new operation is complete.
WINDOW_VP "vport1" 100,100 125,125