Gecko (layout engine)

Gecko offers a rich programming API that makes it suitable for a wide variety of roles in Internet enabled applications, such as web browsers, content presentation and client/server. Primarily it is used for the Mozilla browser derivatives such as Netscape and Mozilla Firefox, but it is used elsewhere as well. Gecko is cross-platform and works on a number of different operating systems, including Microsoft Windows, Linux and Mac OS X

Gecko is generally considered to be the second most-popular layout engine on the Web, after Microsoft's Trident (used by Internet Explorer for Windows), but before KHTML (used by Konqueror and Apple Safari), Opera's Presto and Microsoft's Tasman (used by Internet Explorer for Mac).

Standards support

• HTML 4.0
• XML 1.0
• XHTML 1.1
• MathML
• CSS Level 1 (partial support for CSS 2 and 3)
• DOM Level 1 and 2 (partical support for DOM 3)
• RDF
• JavaScript 1.5

Gecko also has limited support for some non-standard Internet Explorer features, such as the tag and the document.all property (though pages explicitly testing for document.all will be told it is not supported). While this increases compatibility with many documents designed only for Internet Explorer, some purists argue that it harms the cause of standards evangelism.

It appears likely that Gecko will add support for some of the technologies developed by the Web Hypertext Application Technology Working Group in the near future. On April 19, 2005, the support for the HTML canvas element has been checked in [1].

History

Development of the layout engine now known as Gecko began at Netscape in 1997, following the company's purchase of DigitalStyle. The existing Netscape rendering engine, originally written for Netscape Navigator 1.0 and upgraded through the years, was widely considered to be inferior to the one used in Microsoft Internet Explorer. It was slow, did not comply well with W3C standards, had limited support for dynamic HTML and lacked features such as incremental reflow (when the layout engine rearranges elements on the screen as new data is downloaded and added to the page). The new layout engine was developed in parallel with the old, with the intention being to integrate it into Netscape Communicator when it was mature and stable. At least one more major revision of Netscape was expected to be released with the old layout engine before the switch.

After the launch of the Mozilla project in early 1998, the new layout engine code was released under an open-source license. Originally unveiled as Raptor, the name had to be changed to NGLayout (next generation layout) due to trademark problems. Netscape later rebranded NGLayout as Gecko. While mozilla.org (the forerunner of the Mozilla Foundation) initially continued to use the NGLayout name (Gecko was a Netscape trademark)[1], eventually the Gecko branding won out. For a time, Gecko was used to refer to both the old NGLayout layout engine and XPFE (cross-platform front-end) — the new XML-based Mozilla user interface, rendered by NGLayout — but it is now used solely to refer to the layout engine.

In October 1998, Netscape announced that its next browser would use Gecko (then still called NGLayout) rather than the old layout engine, requiring large parts of the application to be rewritten. While this decision was popular with web standards advocates, it was largely unpopular with Netscape developers, who were unhappy with the six month timeframe given for the rewrite. It also meant that most of the work done for Netscape Communicator 5.0 (including development on the Mariner improvements to the old layout engine) had to be abandoned. Netscape 6, the first Netscape release to incorporate Gecko, was released in November 2000 (the name Netscape 5 was never used).

As Gecko development continued, other applications and embedders began to make use of it. America Online, by this time Netscape's parent company, eventually adopted it for use in CompuServe 7.0 and AOL for Mac OS X (these products had previously embedded Internet Explorer). However, with the exception of a few betas, Gecko was never used in the main Windows AOL client.

On July 15 2003, AOL laid off the remaining Gecko developers and the Mozilla Foundation (formed on the same day) became the main steward of Gecko development. Today, Gecko is developed by employees of the Mozilla Foundation, employees of companies that contribute to the Mozilla project and volunteers.

Gecko-based applications

Web browsers

AOL for Mac OS X

Aphrodite**

Beonex Communicator*

Camino for Mac OS X

CompuServe 7.0 for Windows and Mac OS X

DocZilla for Windows and Linux

Epiphany for GNU/Linux

Galeon for Linux

IBM Web Browser for OS/2*

K-Meleon for Windows

Kazehakase for Linux

ManyOne*

Mozilla (also known as the Mozilla Application Suite, Mozilla 1.x or SeaMonkey)*

Mozilla Firefox*

Minimo (web browser for small devices)

Netscape 6.0 and later versions*

Q.BATi for Mac OS X

Salamander for GNU/Linux

Skipstone for GNU/Linux

Other applications

ActiveState Komodo (visual development environment for Perl, Python and more on Windows and Linux) [1] (news aggregator for Linux)

Mozilla ActiveX Control (allows ActiveX developers to easily embed Gecko in applications)

Mozilla Calendar (calendar and personal information manager)*

Mozilla Thunderbird (email/newsgroup client and news aggregator)*

Nvu (web authoring application)*

Gecko# for Windows (.NET Binding for Gecko)[1]*
Also uses Gecko to render its entire user interface via XUL.

See also

List of layout engines

Comparison of layout engines

External links

Mozilla Layout Engine