Libraries, Tools, Toolkits, and Widget Sets

Libraries, Tools, Toolkits, and Widget Sets

When you prepare a program to run with the X Window System, you can choose the level of complexity and control that suits you best, depending on how much time you have and how much control you need.

This section looks at different tools and libraries for working with OpenGL in an X Window System environment, moving from easy-to-use toolkits and libraries with less control to the Xlib library, which is more primitive but offers more control. Most application developers usually write at a higher level than Xlib, but you may find it helpful to understand the basic facts about the lower levels discussed in this guide.

Note that the different tools are not mutually exclusive: You may design most of the interface with one of the higher-level tools, then use Xlib to fine-tune a specific aspect or add something that's otherwise unavailable. Figure 1-1 illustrates the layering:

IRIS ViewKit(TM) and Open Inventor(TM) are layered on top of IRIS IM, which is on top of Xlib.
GLX links Xlib and OpenGL.
Open Inventor uses GLX and OpenGL.

Figure 1-1 : How X, OpenGL, and Toolkits are Layered

Note: If you write an application using IRIS Viewkit, OpenInventor, or RapidApp(TM), the graphical user interface will be visually consistent with the Indigo Magic desktop.

RapidApp

RapidApp is a graphical tool, available from Silicon Graphics, that allows developers to interactively design the user-interface portion of their application. It generates C++ code utilizing IRIS ViewKit (see "IRIS ViewKit") for each user-interface component as well as the overall application framework. As with all applications based on ViewKit, IRIS IM (Motif) widgets are the basic building blocks for the user interface. RapidApp is not included in Figure 1-1 because it generates ViewKit and IRIS IM code and is therefore dependent on them in a way different from the rest of the hierarchy.

To speed the development cycle, RapidApp is integrated with a number of the Developer Magic(TM)tools. This allows developers to quickly design, compile, and test object-oriented applications.

RapidApp also provides easy access to Silicon Graphics specific widgets and components. For instance, you can add an OpenGL widget to a program without having to know much about the underlying details of integrating OpenGL and X.

For more information, see the Developer Magic: RapidApp User's Guide, also available online through IRIS InSight.

Open Inventor

The Open Inventor library uses an object-oriented approach to make the creation of interactive 3D graphics applications as easy as possible by letting you use its high-level rendering primitives in a scene graph. It is a useful tool for bypassing the complexity of X and widget sets, as well as many of the complex details of OpenGL.

Open Inventor provides prepackaged tools for viewing, manipulating, and animating 3D objects. It also provides widgets for easy interaction with X and Xt, and a full event-handling system.

In most cases, you use Open Inventor, not the lower-level OpenGL library for rendering from Open Inventor. However, the Open Inventor library provides several widgets for use with X and OpenGL (in subclasses of the SoXtGLWidget class) that you can use if OpenGL rendering is desired. For instance, the SoXtRenderArea widget and its viewer subclasses can all perform OpenGL rendering. SoXtGLWidget is, in turn, a subclass of SoXtComponent, the general Open Inventor class for widgets that perform 3D editing.

Components provide functions to show and hide the associated widgets, set various parameters (such as title and size of the windows), and use callbacks to send data to the calling application. The viewer components based on SoXtRenderArea handle many subsidiary tasks related to viewing 3D objects. Other components handle anything from editing materials and lights in a 3D scene, to copying and pasting 3D objects.

Note that if you're using libInventorXt, you only need to link with libInventorXt (it automatically "exports" all of the routines in libInventor, so you never need to use -lInventorXt -lInventor, you only need -lInventorXt).

For detailed information on Open Inventor, see The Inventor Mentor: Programming Object-Oriented 3D Graphics with Open Inventor,(TM) Release 2, published by Addison-Wesley and available online through IRIS InSight.

IRIS ViewKit

The IRIS ViewKit library is a C++ application framework designed to simplify the task of developing applications based on the IRIS IM widget set. The ViewKit framework promotes consistency by providing a common architecture for applications and improves programmer productivity by providing high-level, and in many cases automatic, support for commonly-needed operations.

When you use Viewkit in conjunction with OpenGL, it provides drawing areas that OpenGL can render to.

For more information, see the IRIS ViewKit Programmer's Guide, available online through IRIS InSight.

The IRIS IM Widget Set

The IRIS IM widget set is an implementation of OSF/Motif provided by Silicon Graphics. You're strongly encouraged to use IRIS IM when writing software for Silicon Graphics systems. IRIS IM integrates your application with the desktop's interface. If you use it, your application conforms to a consistent look and feel for Silicon Graphics applications. See the sources listed in "Background Reading" on page xxv for further details.

The Xlib Library

The X library, Xlib, provides function calls at a lower level than most application developers want to use. Note that while Xlib offers the greatest amount of control, it also requires that you attend to many details you could otherwise ignore. If you do decide to use Xlib, you are responsible for maintaining the Silicon Graphics user interface standards.