Envelope

In many situations, it is favorable to minimize the information to be displayed on the screen. One way of doing this is to replace one or several views with its envelope.

For the subpicture containing the drawing form, the envelope is its main frame and the frames around the tables of the form. For all other subpictures the envelope coincides with the min-max-rectangle of the subpicture in its current size. The benefit of the use of envelopes is:

• It greatly reduces the amount of information on the screen and thus makes the repainting of the picture quicker.

• The system will reject all trials to add information to a subpicture that is blanked out. By having all subpictures blanked out, except the one he intends to add information to, the operator can protect himself against adding information to an unintended subpicture.

When the envelope of a subpicture is displayed, the rest of the information belonging to it is blanked out.