Creating Applications with Mozilla

Chapter 8. XPCOM

This chapter provides a high-level introduction to XPCOM component technology. XPCOM can be difficult to master, but after reading this chapter, you should have a good sense of what it is and the important part it plays as Mozilla's core technology. You should be able to find and use existing scriptable components in your own applications and create a simple XPCOM component by using JavaScript or C++.

XPCOM permits a reusable code module to be globally accessible to a Mozilla-based application. You do not need to worry about including external source files in your application distribution and you can distribute components by using XPInstall. This type of architecture makes the development of core application services flexible and entirely modular.

The section Section 8.2.1 lets you create an interface from start to finish -- writing the implementation for that interface, compiling it into a type library, registering it with Mozilla, and then testing the new component. One advantage of using XPCOM is that you can create multiple implementations for a single interface; following the JavaScript component section, we will take the same nsISimple interface and implement it in C++ as well.

The section Section 8.2.5 includes some techniques and programming tasks that are particular to C++ components, such as handling return values and generating header files and useful macros. The section Section 8.2.7 introduces the XPCOM bindings for the Python language (pyXPCOM). First, ...