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分类： 系统运维
2009-04-03 10:09:14
This page is part of the extension development documentation project.
Ask your questions in . Also .
Note: development documentation is in process of being moved to Mozilla Development Center (MDC).
Two major extension developers' features introduced in Firefox 1.5 were the greatly simplified chrome registration scheme and the . These changes make it even easier to start writing extensions.
This article describes steps needed to get started with extensions development. Last two sections have a few development tips and packaging information. Most of it is targeted at beginners in extension development, although the setup tips should be useful for everybody. This article is concise and doesn't go into discussing the technologies involved; it's more of a crash-course. Another, more detailed tutorial, is available at developer.mozilla.org.
It's a wiki page, so feel free to make improvements to this page and to add your feedback on the Talk page. However questions and requests for help are better suited for the .
Extensions created in this way will only work on Firefox/Thunderbird 1.5 and later, but you should be able to make changes to ensure your extension is compatible with Firefox 1.0 quite easily.
Again, this will work only in Firefox/Thunderbird 1.5 or later, not 1.0.x! Not 1.0.6, 1.0.7 or anything like that. Only 1.5 or later.
Contents[] |
This article focuses on Firefox extensions, although it also applies to other Toolkit applications, such as Thunderbird.
The first thing you need to do is download a recent version of your application. You can get Firefox . As was mentioned above, you need Firefox 1.5 or later, setup tips from this article will not work in earlier versions.
For further instructions, see Setting up extension development environment. Do read that page, it will save you many hours when developing and debugging your extension. In particular, you must set the javascript.options.showInConsole pref to true.
This extension adds an item called 'Hello World!' to the Tools Menu in Firefox. It's a good example of creating an extension that pops up a new window when you activate it.
You should plan what you need for your extension; we will use an example that provides a new menu option that creates a message in a window. The following files are required, choose your own names if you like (but if you change any names remember to update all references to them), except for the folders and files 'chrome.manifest' and 'install.rdf'.
| Filename | Purpose |
|---|---|
| chrome.manifest | Tells Firefox where your chrome files are and what to do with them |
| install.rdf | The description file for your extension ("Install manifest") |
| overlay.xul | The file describing UI elements to add to the browser window |
| overlay.js | The file with scripts to run in the browser window |
| overlay.dtd | Contains translation for text string codes in overlay.xul |
| hello.dtd | Contains translation for the strings in hello.xul |
| overlay.css | Lets you adjust appearance of UI elements with CSS |
| hello.xul | The file describing the UI of the new window |
| helloworld@mozilla.doslash.org | A pointer to your extension files |
As you should already know, extensions usually modify an application's UI ("chrome") and behavior by providing overlays to already existent windows/documents. Those overlays are a part of the extension's content package (content provider). Most extensions also have one or more locales and skins. (If you didn't know that, we advise you to read chapter from XULPlanet's XUL Tutorial and document).
This section describes what directory structure and what files are needed in order to make Firefox register your extension's files.
You can download the with all necessary stub files and appropriate folder structure and skip to Registering your extension in the Extension Manager. It's recommended that you nonetheless read the below subsections, as they explain the function of each file in the package and provide links to other resources.
Below is the folder structure we will use. You may use a different structure, as long as you also update your chrome.manifest (see below) accordingly. Create the following structure in the folder where you intend to develop your project:
helloworld/
chrome.manifest
install.rdf
content/
overlay.js
overlay.xul
hello.xul
locale/
en-US/
overlay.dtd
hello.dtd
skin/
overlay.css
The folders are traditionally named "content", "locale" and "skin", and you should follow the tradition. You may call the files inside those folders whatever you want (except chrome.manifest and install.rdf).
Note: This folder structure is for development, you'll need different folder structure when packaging your extension.
Recent versions of Firefox read a simple plaintext chrome.manifest file (instead of the old and confusing ) to determine what packages and overlays your extension provides. The format of this file is described in the Chrome Registration document. In the following example we'll create a chrome.manifest file for our folder structure.
It looks like this (assuming your extension's package name is "helloworld"):
|
1 |
content helloworld content/ |
|---|
What each line of the file does:
chrome://helloworld/content/ to the content folder.
chrome://browser/content/browser.xul location, allowing you to modify Firefox's main window UI from your overlay.xul file.
chrome://global/content/customizeToolbar.xul document (used, for example, when ). You could instead register an overlay and include the stylesheet in the overlay using the Warning: Don't forget the end slash at the end of the paths : "content/" works, whereas "content" doesn't. Also note that the package name ('helloworld' in this case) has to be all lowercase.
Note: this file will be a bit different when you create an XPI for your extension, see the Packaging section below.
overlay.xul is a simple XUL overlay. You can read more about overlays at and MDC.
A simple overlay looks like this:
|
1 |
|
|---|
What each line of the file does:
As you may know, JavaScript files are used to define application's behavior. Please refer to the list of JavaScript development resources for information on JavaScript in general.
An important issue you should be aware of is that all scripts that are loaded for a given document (the scripts used by the window itself, and scripts loaded from overlays to that document) share the same scope. This means you should use unique names for global identifiers in your extensions to avoid clashing with other extensions. It's usually accomplished by prefixing all global identifiers with the name of your extension or by putting most/all of your variables and functions in an object with an unique name.
Typical JavaScript file for an overlay looks like this:
var Helloworld = {
onLoad: function() {
// initialization code
this.initialized = true;
},
onMenuItemCommand: function() {
window.open("chrome://helloworld/content/hello.xul", "", "chrome");
}
};
window.addEventListener("load", function(e) { Helloworld.onLoad(e); }, false);
DTD files are used to make XUL/XBL/XHTML and other XML files in Mozilla chrome localizable. Basically, instead of hard-coding the strings in your XUL file, you use XML entities, which expand to the values declared in the DTD file referenced at the top of the XUL file.
It makes your extension localizable, because there may be a few different locale providers for your extension, and Mozilla is able to choose between them at run-time.
DTD files used for localization purposes consist of entity declarations like the one below:
This is the file for the new window.
In addition to modifying existing windows, you can create new
windows for your extensions. The UI of your own windows is also
described in XUL files, but unlike overlays, the root element is a
The example package includes file hello.xul, which is used to describe a simple window.
title="&title.label;">
&separate.label;
install.rdf file is used by the Extension Manager when installing an XPI file and when registering an extension at specified location. In Firefox 1.5 and later it's only used to provide EM metadata, such as extension's ID, version, description, author etc. For more information, see article.