AIX Version 4.3 Differences Guide

• Snap-back scrolling, a feature that allows users to have the scroll bar slider
snap-back to its starting position when the mouse is dragged beyond a certain
distance from the scroll bar area.
8.3.3 The Motif Extensibility Framework
One of the problems Motif developers are facing is the complexity of developing
new widgets for their applications. Subclassing Motif widgets without the source
code of the parent class is a challenge with Motif 1.2. Even developing a new
class from the superclass source code is not always easy. There are four sets of
issues for the widget developer:
• Developing a new widget from scratch can take a significant amount of time.
For its internal widget development, OSF built a library of internal functions
that are commonly used in the widget set. For example, there are functions to
draw 3D shadows. If those functions were available to widget writers, it would
speed up the development process.
• The Motif widget class methods are currently not documented. Widget writers
have to browse into the superclass source to figure out the class methods and
what they do. Documenting the widget class methods of the most frequently
subclassed widgets helps widget development.
• Sometimes, it is not possible to have new widgets behave as expected when
they are managed by a standard parent. One of the key issues is that, in a
number of cases, manager widgets perform tests about the nature of their
children. These tests are typically done by testing the class pointers of the
children. When applied to a custom widget, they fail, and the widget does not
behave properly.
• Motif subclassing requires use of the Xt object framework, implemented in C.
Most C++ application programmers, now a significant number, want to write
subclasses of the Motif widgets directly in C++.
OSF has addressed these issues by developing an extensibility framework for
Motif that will significantly help OSF/Motif widget developers and application
programmers. This framework consists of four parts:
• A new mechanism has been developed on top of intrinsics, called Traits.
• A new set of APIs has been documented by OSF for widget writers.
• A new book hs been published by OSF with documentation on how to correctly
subclass a Motif widget. This documentation is accompanied by a CD-ROM
containing source code illustrations. The book also contains documentation
for the existing class methods that can be re-used by developers.
• A set of C++ base classes has been developed that makes it possible to
derive subclasses of the Motif Manager and Primitive widgets (the most
frequently derived) directly in C++ while retaining the ability to use Motif
functions on those widgets, such as keyboard traversal function
XmProcessTraversal().
8.3.3.1 Traits
The trait abstraction was first introduced by Xerox. A trait is a characteristic of an
object that can be expressed by a set of methods/data applied to, or carried by
the object holding that trait. At a higher level, a trait implements a behavior that
can be shared by different objects of a system without requiring any particular
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