Imagine you have a preferences window with several different pages, e.g. the MUI preferences with object, frame, image, font, screen, keyboard and system prefs. Instead of one separate window for each group, you could put all pages into a page group and have a cycle gadget for page switching. This will make your program easier to use since the user won't have to handle a lot of windows. However, he will not be able to work with more than one page at the same time.

Sizes are calculated as follows:

The minimum width/height of a page group is the maximum minimum width/height of all its children.

The maximum width/height of a page group is the minimum maximum width/height of all its children.

When the maximum width/height of a child in a page group is smaller than the minimum width/height of the page group (since it contains another child with big minimum width/height), the child be centered.

Page groups are not limited in depth, children of a page group may of course be other page groups.

If you want to have a gadget only visible under certain conditions, you could make a page group containing this gadget and an empty rectangle object.

If you want TAB cycling for the objects in a page group, simply include all objects in the cycle chain (as if they all were visible at the same time).

A special type of page group is created by Register class which generates a series of register tabs for all of its children. See Register class for details.