The ViewportField class defines a fixed area within a form that acts as a window for another field. Viewports are useful if the field displayed in the viewport varies in size, but you want to ensure that it always takes up the same space on the form. If the viewed field is bigger than the viewport, the system automatically displays scroll bars. If the viewed object is smaller than the viewport, no scroll bars are displayed.

A ViewportField can contain only one field. To display more than one field in the viewport, combine the fields you want to display into a subform or flexible form.

Typically you do not associate a viewport with a variable, because you generally want direct 4GL access to the field displayed in the viewport. However, if you do associate the viewport with a variable, the field behaves as a reference variable with a single attribute.

For a discussion of using a viewport field in conjunction with a dynamically modified table field, see the Programming Guide.