Volume 6A: Motif Programming Manual

Obviously, the automatic scrolling mechanism provided by the ScrolledWindow is much simpler than the

application−defined mechanism and it requires much less application intervention. However, there are some

drawbacks in the implementation of automatic scrolling. Automatic ScrolledWindows only scroll in single−pixel

increments. If other scrolling behavior is required, you must use application−defined scrolling. And while

application−defined scrolling is far more complicated, the advantage is that it provides more flexibility in the ways

that the object is scrolled.

10.2 Creating a ScrolledWindow

Creating a ScrolledWindow is no different from creating other kinds of Motif widgets. Applications that wish to use

ScrolledWindows must include the header file <Xm/ScrolledW.h>. The process of creating a ScrolledWindow is

shown in the following code fragment:

Widget scrollw;

scrollw = XtVaCreateManagedWidget ("name",

xmScrolledWindowWidgetClass, parent,

resource−value−list,

NULL);

The parent can be a Shell or any manager widget. The ScrolledWindow can be created as a managed widget, since

the addition of its child does not cause it to renegotiate its size. (See Chapter 8, Manager Widgets, for a discussion of

when manager widgets should be created as managed or unmanaged widgets.) The resource−value pairs control the

behavior of the ScrolledWindow, as well as its visual effects. The most important resources are

XmN-scrollingPolicy, XmN-visualPolicy, and XmN-scrollBarDisplayPolicy. The value for

XmNscrollingPolicy ...