Firefox Hacks [Electronic resources] نسخه متنی

Hack 90. Identify Reusable Toolkits

Don't code everything from
scratch: reuse bits and pieces of Firefox.

The chrome files supplied with FirefoxXUL, CSS, JavaScript,
and otherscan be reused by your extension or chrome
application project. If you're familiar with these
pieces, you can possibly save yourself a lot of time. At least
you'll save yourself a lot of confusion.

8.8.1. Poking Around Inside toolkit.jar

In the install area, inside the chrome
directory, lies the toolkit.jar
archive. This is the starting point for
all XUL pages and therefore for all extensions and chrome
applications. It consists of a number of pieces.

This toolkit.jar file changed a small amount
when it was updated from the Mozilla Application Suite (1.x) to
Firefox. Because that change involved renaming and was advertised in
a number of influential places, some people assumed that there would
be significant compatibility issues. This is not the case. The most
important files in toolkit.jar have changed very
little, so there is substantial and extensive compatibility with
other Mozilla-based products. There is 100 percent compatibility with
Thunderbird and Nvu, at least. Furthermore, the
toolkit.jar file is just a file, and it is easy
for extensions to specialize or override portions of it with their
own tailored files. There is therefore no reason to consider this
file an immovable requirement. It is just a well-tested and
convenient starting point.

8.8.1.1 The global package

The
global package has special status in the
chrome. It provides default functionality that XUL pages can pick up,
regardless of which theme or locale is the current one. Each new
theme that is created must implement a skin for
the special global package.

The global package also holds
locale and content
information. The locale information is delivered in the default
locale JAR file, such as en-US.jar, but the
content information is in toolkit.jar. This
content information includes all the ultra-generic XUL dialog boxes
that an XUL application might want. Examples include print dialog
boxes, file pickers and savers, and the XUL content
that's displayed when the JavaScript alert() method is called.

These dialogs can also be called from XPCOM components [Hack #82] .

8.8.1.2 The xul.css master XBL stylesheet

A special part of toolkit.jar is
the xul.css file.
This is the place to look for any and all details about the
definition and behavior of XUL tags. This stylesheet is applied to
every XUL document that Firefox displays. It uses the -moz-binding
style property [Hack #69] to
define every XUL tag (and therefore the whole XUL vocabulary).

This file is therefore used in place of a DTD, an XML Schema
definition, or a hardcoded solution (there is also a little bit of
XUL hardcoding). It is therefore the ultimate authority and reference
on XUL. All of the XBL bindings attached to tags using this
stylesheet are also located in toolkit.jar.

Modifying xul.css modifies the look and/or
behavior of all XUL-based extensions and applications.
Don't modify this file directly; extend or override
it with your own if you need to make changes.

8.8.1.3 The mozapps package

Another source of common dialog boxes appears in the
mozapps package, which is also located in
toolkit.jar. Rather than contain generic dialog
boxes, this package contains functionality that represents
"The Mozilla Way." If your chrome
application wants to offer an extension interface, a themes
interface, an update manager, or XPInstall functionality, then
you'll find some generic pieces you can reuse.

8.8.2. Scavenging Application Pieces

The toolkit.jar archive is not the only place to
find useful application pieces. Firefox's
browser.jar chrome archive also contains
some reusable bits. These include the Bookmark Manager and the Cookie
Viewer. There's also the Help system, which is
stored separately in help.jar. In general, any
and all chrome content can contain gems that you can reuse, but as
your application becomes more specific and more specialized, reusable
pieces are harder to find.

8.8.3. Finding Embedded Components

Separate from the chrome proper are the XPCOM components that are
used extensively in chrome scripts. It's not so easy
to determine from scratch which components support which interfaces.

The
cview extension (http://www.hacksrus.com/~rginda/) goes a
little way toward listing all these components and their interfaces.
For a complete set of reports, try the downloadable files from the
book Rapid Application Development with Mozilla
(Prentice Hall PTR). You can find them at the
author's web site, http://www.nigelmcfarlane.com/books/radmoz_supportl.

8.8.4. Reusing Script Libraries

In addition to user-interface pieces, you can speed up your
application by using existing JavaScript libraries. Here are two
examples.

nsDragAndDrop.js

This is a script library supplied with
toolkit.jar that eases the development of
mouse-driven drag-and-drop functionality. Instead of having to
housekeep complex state systems, this script provides a predefined
manager object that you can climb on top of. This particular example
is of medium difficulty to learn, but it's easy to
use.

The jsLib library

The jsLib
library (http://jslib.mozdev.org)
provides wrapper objects that seek to make common tasks like file
handling and RDF datasources easier to use. Although some simplicity
is achieved, the library presents a number of separate objects, and
fitting them all together might not be what you had in mind as a
time-saver. Nevertheless, it provides a medium-level abstraction that
several extensions have deemed worthy of use.