Volume 6A: Motif Programming Manual

10 ScrolledWindows and ScrollBars

This chapter describes the ins and outs of scrolling. It pays particular attention to application−defined scrolling, which

is often required when the simple scrolling provided by the ScrolledWindow widget is insufficient.

The ScrolledWindow widget provides a viewing area into another, usually larger, visual object. The viewport may be

adjusted by the user through the use of ScrollBars that are attached to the ScrolledWindow. The Motif MainWindow,

ScrolledList, and ScrolledText objects use ScrolledWindows to implement scrolling for their respective contents. The

ScrolledWindow can also be used independently to provide a viewport into another large object, such as a

DrawingArea or a manager widget that contains a large group of widgets. All of these scenarios are explored in this

chapter.

10.1 The ScrolledWindow Design Model

The user always interacts with a ScrolledWindow through ScrollBars. Internally, however, there are several ways to

implement what the user sees. These methods are based on two different scrolling models: automatic scrolling and

application−defined scrolling. In either case, the application gives the ScrolledWindow a work window that contains

the visual data to be viewed. Although the two models are different, they share many of the same concepts and

features.

In automatic scrolling mode, the ScrolledWindow operates entirely on its own, adjusting the viewport as necessary in

response to ScrollBar activity. The application simply creates the ...