GTK+/Gnome应用开发

　　I. Overview

　　The first chapter of the book gives you an overview of GTK+ and Gnome technologies. Chapters 2 and 3 rapidly cover the basics of GTK+ programming. These chapters move very quickly, and give you the information you need to understand the remainder of the book. For a gentler introduction to GTK+, you may wish to read the GTK+ Tutorial or Eric Harlow's book Developing Linux Applications with GTK+ and GDK.

　　Introduction

　　This chapter gives you an overview of the technologies described in this book.

　　What is Gnome?

　　Gnome is a free (or "open source") software development project started in 1997 by Miguel de Icaza of the Mexican Autonomous National University and a small team of programmers from around the world. Inspired by the success of the similar K Desktop Environment (KDE) project, the burgeoning popularity of the GNU/Linux operating system, and and the power of the GTK+ graphical toolkit, Gnome grew quickly --- within a year, hundreds of programmers were involved and many thousands of lines of code had been written. Gnome has become a powerful framework for GUI application development which runs on any modern variety of UNIX.

　　"Gnome" is actually an acronym: GNU Network Object Model Environment. Originally, the project was intended to create a framework for application objects, similar to Microsoft's OLE and COM technologies. However, the scope of the project rapidly expanded; it became clear that substantial groundwork was required before the "network object" part of the name could become reality. The latest development versions of Gnome include an object embedding architecture called Bonobo, and Gnome 1.0 included a fast, light CORBA 2.2 ORB called ORBit.

　　Gnome is a part of the GNU Project, whose overall goal is developing a free operating system (named GNU) plus applications to go with it. GNU stands for "GNU's Not UNIX", a humorous way of saying that the GNU operating system is UNIX-compatible. You can learn more about GNU at http://www.gnu.org.

　　Gnome has two important faces. From the user's perspective, it is an integrated desktop environment and application suite. From the programmer's perspective, it is an application development framework (made up of numerous useful libraries). Applications written with the Gnome libraries run fine even if the user isn't running the desktop environment, but they integrate nicely with the Gnome desktop if it's available.

　　The desktop environment includes a file manager, a "panel" for task switching, launching programs, and docking applets, a "control center" for configuration, and several smaller bells and whistles. These programs hide the traditional UNIX shell behind an easy-to-use graphical interface.

　　Gnome's development framework makes it possible to write consistent, easy-to-use, interoperable applications. The X Window System designers made a deliberate decision not to impose any user interface policy on developers; Gnome adds a "policy layer," creating a consistent look-and-feel. Finished Gnome applications work well with the Gnome desktop, but can also be used "standalone" --- users only need to install Gnome's shared libraries. It's even possible to write Gnome applications which do not rely on the X Window System; you might want to provide a non-graphical CORBA service, for example.

　　This book is about Gnome from a developer's point of view; it describes how to write a Gnome application using the Gnome libraries and tools.

　　glib: Portability and Utility

　　glib is a C portability and utility library for UNIX-like systems and Windows. This chapter covers some of the most commonly-used library features in GTK+ and Gnome applications. glib is simple, and the concepts are familiar; so we'll move quickly. For more complete coverage of glib, see glib.h or the free glib reference manual that comes with the library. (By the way: don't be afraid of using the glib, GTK+, or Gnome header files; they are very clean and easy to read, and are handy as a quick reference. For that matter, don't be afraid to look at the source code, if you have very specific questions about the implementation.)

　　glib's various facilities are intended to have a consistent interface; the coding style is semi-object-oriented, and identifiers are prefixed with "g" to create a kind of namespace.

　　glib has a single header file, glib.h.

　　Basics

　　glib provides substitutes for many standard and commonly-used C language constructs. This section describes glib's fundamental type definitions, macros, memory allocation routines, and string utility functions.

　　Type Definitions

　　Rather than using C's standard types (int, long, etc.) glib defines its own. These serve a variety of purposes. For example, gint32 is guaranteed to be 32 bits wide, something no standard C type can ensure. guint is simply easier to type than unsigned. A few of the typedefs exist only for consistency; for example, gchar is always equivalent to the standard char.