
2
The XView Programmer’s Model
XView is intended to simplify application development under the X Window System by pro-
viding the programmer with a set of predefined user interface components. These compo-
nents implement the “look and feel” of the OPEN LOOK Graphical User Interface, developed
by Sun Microsystems, Inc. and AT&T.
This chapter presents a model of XView for the programmer. It is important to understand
this model before you begin writing XView applications. However, you might wish to skim
the concepts presented in this chapter and proceed to Chapter 3, Creating XView Applica-
tions, to examine sample programs.
2.1 Object-oriented Programming
To the programmer, XView is an object-oriented toolkit. XView objects can be considered
building blocks from which the user interface of the application is assembled. Each piece
can be considered an object from a particular package. Each package provides a list of pro-
perties from which you can choose to configure the object. By selecting objects from the
available packages, you can build the user interface for an application.
XView is based on several of the fundamental principles of object-oriented programming:
• Objects are represented in a class hierarchy.
• Objects are opaque data types.
• Objects have attributes which can be set via message passing functions.
• Objects may have callback procedures that are triggered by events.
We will look ...