Volume 6A: Motif Programming Manual

that is to be made visible. The hor_margin and ver_margin arguments indicate the margins that are used if the

viewport of the ScrolledWindow needs to be adjusted to make the widget visible. In early versions of the Motif 1.2

toolkit, there is a bug in XmScrollVisible() that may cause it to function incorrectly when the margins are set to

any value other than 0. If you run the program in the source code you can use the arrow keys to traverse all of the

widgets in the ScrolledWindow.

10.6 Summary

The ScrolledWindow provides a convenient interface for displaying large amounts of data when you have limited

screen real estate. For most situations, the automatic scrolling mode is all that you really need. In this mode, a

ScrolledWindow requires very little care and feeding. By installing callback routines on the ScrollBars, you can even

monitor the scrolling actions. However, there are some drawbacks to the automatic scrolling mode: all of the data

must be rendered into the work window widget and scrolling occurs in single−pixel increments. If the size of the work

window that you need is prohibitively large or if you need to support scrolling in other than single−pixel increments,

you must use application−defined scrolling.

As demonstrated in the source code there is quite a bit of work involved in supporting real application−defined

scrolling because of the different states in the relationship between the size of the work window and the underlying

data. You must be able to support not only the ...