World Library  
Flag as Inappropriate
Email this Article
 

Xul

XUL
Paradigm Declarative (markup language)
Developer Mozilla Foundation
Implementation language C++
Platform Gecko
OS Cross-platform
License MPL
Filename extensions .xul
MIME type: application/vnd.mozilla.xul+xml
Website https://developer.mozilla.org/en-US/XUL
Major implementations
Mozilla
Influenced by
HTML, XML

XUL ( ), which stands for XML User Interface Language, is a user interface markup language that is developed by Mozilla. XUL is implemented as an XML dialect; it allows for graphical user interfaces to be written in a similar manner to Web pages.

XUL can be used to write cross-platform applications such as Mozilla Firefox, where it is interpreted by the layout engine, known as Gecko, which renders Firefox's user interface and Web page display.[1]

In August 2015, Mozilla announced that the use of XUL for creating Firefox add-ons would be deprecated in the future in favour of WebExtensions.[2]

Contents

  • Design 1
  • XUL documents 2
    • XUL elements 2.1
  • XUL applications 3
  • Etymology and 'Ghostbusters' references 4
  • Example 5
  • Similar languages 6
  • See also 7
  • References 8
  • External links 9

Design

XUL relies on multiple existing Web standards and Web technologies, including CSS, JavaScript, and DOM. Such reliance makes XUL relatively easy to learn for people with a background in Web programming and design.

XUL has no formal specification and does not inter-operate with non-Gecko implementations. However, it uses an open-source implementation of Gecko which Mozilla tri-licensed under the GNU GPL, GNU LGPL, and MPL[3] until Gecko changed to GPL-compatible, MPL 2.0.

Mozilla provides experimental XULRunner builds to let developers build their applications on top of the Mozilla application framework and of XUL in particular.

XUL provides a portable definition for common widgets, allowing them to move easily to any platform on which Mozilla applications run.[4]

XUL documents

Programmers typically define a XUL interface as three discrete sets of components:

  1. content: the XUL document(s), whose elements define the layout of the user interface
  2. skin: the CSS and image files, which define the appearance of an application
  3. locale: the files containing user-visible strings for easy software localization

XUL elements

XUL defines a wide range of elements, which roughly belong to the following types:

Top-level elements
window, page, dialog, wizard, etc.
Widgets
label, button, text box, list box, combo box, radio button, check box, tree, menu, toolbar, group box, tab box, colorpicker, spacer, splitter, etc.
Box model
box, grid, stack, deck, etc.
Events and scripts
script, command, key, broadcaster, observer, etc.
Data source
template, rule, etc.
Others
overlay (analogous to SSI, but client-side and more powerful, with higher performance), iframe, browser, editor, etc.

One can use elements from other applications of XML within XUL documents, such as XHTML, SVG, and MathML.

Mozilla added some common widgets — (sometimes called "slider"), (spinbox), time and date pickers — during the Gecko 1.9 development cycle.[5]

XUL applications

While XUL serves primarily for constructing Mozilla applications and their extensions, it may also feature in Web applications transferred over HTTP. The Mozilla Amazon Browser, a former XUL application of this type, provided a rich interface for searching books at Amazon.com.[6]

However, many of the powerful features of Mozilla (such as privileged XPCOM objects) remain unavailable to unprivileged XUL documents unless the script has a digital signature, and unless the user obtains grants of certain privileges to the application. Such documents also suffer from various limitations of the browser, including the inability to load remote XUL, DTD, and RDF documents.

As Gecko provides the only full implementation of XUL, such applications remain inaccessible to users of browsers not based on Mozilla. Mozilla-programmers sometimes refer to XUL applications running locally as chrome.[7]

Other applications using XUL include:

  • The Ample SDK open-source GUI framework provides a cross-browser implementation of XUL in JavaScript.
  • The ActiveState Komodo IDE uses XUL as well as the Open Komodo project announced in 2007.
  • The Songbird music-player and Miro video-player both use built-in XUL.
  • The Elixon WCMS/XUL Content management system uses exclusively remote XUL, thus overcoming some of the aforementioned limits of remote unprivileged XUL documents.
  • The developers of the Celtx media pre-production application used XUL.
  • The Flickr Uploader was built using XUL, and source code is available under GPLv2.[8]
  • Kiwix, the offline WorldHeritage-viewer

With the release of Firefox 4, support for remote XUL was disabled by default, due to security concerns. Loading an XUL page via HTTP would now display an error unless the domain was added to a hidden whitelist.[9]

Etymology and 'Ghostbusters' references

The name "XUL" is a homophonic reference to the cult film Ghostbusters (1984), in which an ancient Sumerian deity called Zuul possesses the character Dana Barrett and declares, "There is no Dana, only Zuul".

Since XUL, like MXML, uses XML to define an interface rather than a document, its developers adopted the slogan "There is no data, there is only XUL". References to this and other elements of the film, such as "Keymaster" and "Gatekeeper", appear in the XUL specification; for instance, the JavaScript debugger component is called Venkman, after the film's character Peter Venkman. Another clear example is the XML namespace URI definition, required at the beginning of every XUL document:

http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul

The linked document displays the slogan in large letters in the center of the screen.

Example

This example shows three buttons stacked on top of each other in a vertical box container:[10]





  
    

Similar languages

Based on HTML, DHTML, and JavaScript, Microsoft's HTML Application resembles XUL as it provides a stand-alone capability to run applications on Windows, outside a Web browser.

The Microsoft Windows Presentation Foundation (WPF) defines XAML, another declarative UI language similar to XUL — it runs on top of the .NET Framework stack.

JavaFX defines FXML as its own declarative UI language like XUL.

See also

References

  1. ^
  2. ^
  3. ^
  4. ^
  5. ^ Firefox 3 for developers
  6. ^
  7. ^
  8. ^ Getting your stuff onto Flickr
  9. ^
  10. ^ The Box Model - XUL | MDN. Developer.mozilla.org (2012-12-16). Retrieved on 2014-03-28.

External links

  • XUL documentation on developer.mozilla.org
  • XUL Periodic Table — Visual demonstration of XUL capabilities (requires a Gecko-based (XUL-enabled) browser such as Mozilla Firefox)
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.