Jump to content

XUL

From Wikipedia, the free encyclopedia

This is an old revision of this page, as edited by Minghong (talk | contribs) at 12:35, 4 March 2005 (→‎Film references: Typo). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

XUL (XML User Interface Language) is a proprietary standard developed to support Mozilla applications like Mozilla Firefox and Mozilla Thunderbird. Like UIML, it is an application of XML that describes user interfaces. The initialism can be pronounced as zool (to rhyme with "cool").

While XUL is not a public standard, it reuses many existing standards and technologies, including CSS, JavaScript, DTD and RDF, which makes it relatively easy to learn for people with background of web programming and design.

The main benefit of XUL is that it provides a simple and portable definition of common widgets. This reduces the software development effort in a way analogous to the savings offered by 4GL tools.

Einführung

An XUL interface is typically defined as three discrete sets of components:

Content
The XUL documents, which define the layout of the user interface.
Skin
The CSS and image files, which define the appearance of an application.
Locale
The DTD documents, which define entities for easy software localization.

For an example, see a "Hello World!" program written in XUL.

XUL elements

The XUL specification covers a wide range of elements, which roughly belong to the following types:

Top-level elements
e.g. window, page, dialog, wizard, etc.
Widgets
e.g. label, button, text box, listbox, radio button, check box, tree, menu, toolbar, group box, tab box, color picker, spacer, splitter, etc.
Box model
e.g. box, grid, stack, deck, etc.
Events and Scripts
e.g. script, command, key, broadcaster, observer, etc.
Data source
e.g. template, rule, etc.
Others
e.g. overlay (analagous to SSI, but client side), iframe, browser, editor, etc.

It is possible to use elements from other applications of XML within XUL documents, such as XHTML and MathML.

Some common widgets - such as spinbox, slider, and canvas - are not available in the current XUL specification, but are on the XUL 2.0 to-do list [1].

Usage

While XUL is mostly used for creating the Mozilla application itself and its extensions, it is possible to use it for web applications transferred over HTTP. One of the most well-known XUL applications of this type is the Mozilla Amazon Browser, which provides a rich interface for searching books at Amazon.com. However, many of the powerful features of Mozilla, like privileged XPCOM objects, are not available to remote XUL documents, and such documents also suffer from various limitation of the browser, such as the inability to load remote XUL, DTD and RDF documents.

Film references

The XUL name is a reference to the film Ghostbusters, in which a ghost called Zuul possesses a character named Dana (played by Sigourney Weaver) and declares "There is no Dana, only Zuul". Since XUL is unusual in using XML to define an interface, rather than a document, its developers adopted the slogan "There is no data, only XUL", as can be seen from the document pointed by the XML namespace URI (http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul). When viewed with an XUL-capable application, it renders something like this:

THERE IS NO DATA.
THERE IS ONLY XUL.

"Keymaster" and "gatekeeper" are also references to the same plotline. This is not the only reference to Ghostbusters within Mozilla - for instance, the JavaScript debugger component is called Venkman, one of the main characters in the film.

See also

Retrieved from "https://en.wikipedia.org/w/index.php?title=XUL&oldid=10766987"