A graphical region can be the parent of another object; a textual region can be the child (but cannot be the parent) of

another object. In the following graphical region definitions:

 

graphical region Butterfly size 400 400

    at position 200 200

 

graphical region Monarch size 100 100

    at position 50 50 in Butterfly

    move 50 50

    circle radius 50

 

Monarch is the child of Butterfly. The figure below shows Butterfly's window on the left, and Butterfly's viewport on the right:

A region's viewport is part of its ancestor's coordinate space. Therefore, the viewport of the child, Monarch, is portrayed in Butterfly's viewport only as long as it is in the window of Butterfly. If you change the position of Butterfly's window so that Monarch's viewport is entirely outside of it, none of Monarch's viewport is portrayed on the screen. Similarly, if you move Butterfly's window so that only part of Monarch's viewport remains in it, only part is portrayed.