Gecko and the NGLayout Engine

Monday Feb 8th 1999 by Jeff Rule

Gecko is the code name for the first release of what will become Netscape Communicator 5.

Gecko is the code name for the first release of what will become Netscape Communicator 5. Netscape has taken a new approach to building browsers: Gone are the days of a new browser version every six months. Partly forced by relentless pressure from Microsoft, Netscape has taken a desperate and possibly brilliant gamble in moving its source code into the public domain. At the same time, it created an independent organization, Mozilla, to oversee developers all over the world who wish to work with the code.

The open source model has been successful for two other pieces of software: the Linux operating system and the Apache Web server. Mozilla completes the picture by adding an open source browser. Mozilla itself only has three full-time organizer/managers—the rest of the development is done by people all over the world who contribute their time and energy to create a world-class browser based on open standards.

Netscape contributes nearly 100 developers to the effort and pays their salaries.

In reality, Netscape contributes nearly 100 developers to the effort and pays their salaries. The hope is the eventually Netscape support will be weaned down and the majority of the work will be handled by outside developers. When this open-source browser is complete, Mozilla will release the code to the public and Netscape will use it as the basis for Netscape Communicator 5.0.

The Netscape/AOL merger
The merger of Netscape with AOL has raised a number of questions regarding the future of Mozilla and the development of Gecko and Netscape 5. Even Mozilla employees have expressed fear over the how they will integrate with AOL. But AOL president Steve Case has stated that the online service supports Mozilla and the open source effort and plans to continue funding its development. In reality, one of the reasons that AOL purchased Netscape is to get access to the Next Generation Layout (NGLayout) engine. AOL is unlikely to kill the goose that lays the golden eggs.

NGLayout engine (the heart of Gecko)
So what is it about the NGLayout engine that is so valuable AOL would turn against Microsoft to obtain it? The layout engine is the heart of the browser and makes up the majority of Gecko. It is the software that takes the standards on the Web and translates HTML and other code to the screen. It is the layout engine into which the standards are built. The layout engine also determines how fast pages display once they are downloaded. As you can see in this screen capture of the Gecko browser, the interface is similar to Netscape 4 but will change with later releases.

The NGLayout is a complete rewrite of the layout engine used in Netscape 4. Where Netscape 4 was a huge piece of organically developed software with code dating back to Netscape 1.0, NGLayout is written to be modular, super quick, and take up little memory. In addition, it is written to support all the latest standards. By being modular, the NGLayout engine can be used in other networked devices like handheld PC companions such as the Palm Pilot or set top boxes such as WebTV. Expect to see AOL use the NGLayout engine to produce information appliances as part of its AOL Anywhere campaign to make Web and AOL access both wireless and ubiquitous.

is written to be modular,
super quick, and take up
little memory.

But first, the NGLayout engine is the heart of Netscape Communicator. Communicator’s strength has been that it is available on all platforms. Netscape has not given up on this despite the complete rewrite of the layout engine. The initial release of Netscape Communicator 5 will most likely include versions for Windows 95/98, Windows NT 4 and 5, Linux, Irix, and even the Mac. Other projects are in the works to port to OS/2, Rhapsody, BeOS, Amiga, and Windows 3.1.

Standards support
The NGLayout engine is built from the ground up with standards in mind, especially those from the World Wide Web Consortium (W3C). Netscape has always supported standards, but many believe that Microsoft has done a better job of it in the Version 4.x browsers. Partly because of the time period in which it came out, Internet Explorer has much better support for the Document Object Model (DOM) and Dynamic HTML which results from DOM support. (Netscape released Communicator 4.0 before the release of the W3C standard and only included partial support for the DOM and additionally supported the proprietary <LAYER> tag, which it used for much of its Dynamic HTML.)

The final NGLayout is expected to implement a union of the Communicator 4.0 and W3C Level 1 Document Object Models. Full backward compatibility with Netscape 4 is expected. Dynamic HTML compatibility between Internet Explorer and Netscape has been a major issue in the Version 4 browsers. While both companies have vowed to support the DOM, Level 1 from the W3C compatibility is still in question.

Let’s take a look at Gecko’s support and what the final version of the NGLayout engine in Netscape Communicator 5 will support.

  Gecko Netscape

HTML 4.0



Cascading Style
Sheets 1



Cascading Style
Sheets 2



DOM Level 0
(Netscape 3)



DOM Level 1









As you can see, Gecko’s release of the NGLayout engine has little support for the standards it will eventually adhere to. A sneak preview of sorts is available on Mozilla’s DOM Project page, where you can track the progress of certain projects in the works at Mozilla. You'll see that the projects to make Netscape Communicator 5 a world-class browser for standards support is already underway.

Tailored for the developer
The Gecko browser is a developer’s release. It is not meant to be more than a preview of the capabilities to come. (In all likelihood it was released to maintain parity with Microsoft's stable and nearly complete Internet Explorer 5.0. But Gecko promises to take the browser far beyond its origins on the computer into embedded systems, Net-aware information appliances, and set-top boxes.

Jeff Rule is a principal at RuleWeb Development, specializing in DHTML, SMIL, WebTV, interactive TV, and Java-based multimedia enhancements for advanced media sites.

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