|
|
nglayout project / gecko layout engine
FAQ
Last updated 23 March 1999
In this document:
What is Gecko?
Gecko is Netscape's revolutionary next-generation browser engine based
entirely on open Internet standards such as HTML 4.0, CSS 1/2, XML 1.0,
and the W3C Document Object Model. Gecko also includes a set of complementary
browser components that work alongside the layout engine to form the founding
platform of Netscape's next generation Web browser. Gecko is currently
under development. Gecko has been known previously by the code names "Raptor"
and "NGLayout"; the new name was chosen following a trademark infringement
dispute.
What is the relationship between the
mozilla.org "NGLayout Project" and the "Gecko layout engine"?
mozilla.org's "NGLayout Project" is creating the "Gecko layout engine."
Although the layout engine's name has been changed to Gecko, the project's
name has remained "NGLayout Project" for historical reasons.
What is a layout engine?
Basically, a layout engine takes content (such as HTML, XML, image
files, applets, and so on) and formatting information (such as Cascading
Style Sheets, hard-code HTML tags, etc.) and displays the formatted content
on the screen. It "paints" the browser's content area, which is the blank
area inside the browser window's "chrome."
Formally, a layout engine defines the placement policy for a document
and places content on a page. Gecko's core is a very fast layout engine.
Gecko also offers the ability to parse various document types (HTML, XML,
CSS, etc), advanced rendering capabilities including compositing and tranforms,
and support for embedded JavaScript and applets.
Note: Gecko is so fast and so powerful that it's being
used to create the browser's user interface ("chrome") as well. In other
words, Gecko will not only be displaying the document's content, but it
will also be painting the scroll bars, tool bars, and menus on the screen
as well.
How is a layout
engine like Gecko different from a Web browser?
Gecko provides the foundation needed to display content on the screen,
including a layout engine and a complementary set of browser components.
However, Gecko does not package all of these components alongside other
interface modules in a coherent, user friendly Web browser application
(including menus, tool bars, etc.), such as Netscape Navigator.
mozilla.org will assemble the necessary components into an application
called the Mozilla browser, which will be available for free download from
mozilla.org. Netscape will release its own version of the browser branded
as Netscape Navigator, which will be available for free download from netscape.com.
Third parties such as ISVs and hardware vendors will pick and choose
the components they want to use in their applications or hardware devices.
Certain browser components are not provided as part of Gecko, such as bookmarks,
history, address book, etc. However, the source for all those components
is available for free download from mozilla.org.
Why are we building
a new layout engine?
The original Mozilla browser, first released as Navigator 1.0, was
developed rapidly by a small team that was passionate about creating the
next killer app -- and they succeeded wildly. Now that the web has evolved,
Netscape has assembed the finest team available to redesign and redevelop
the next generation layout engine upon which it will build future products.
Gecko enables a pioneering new class of dynamic content that is more interactive
and offers greater presentation control to Web developers, using open and
recommended Internet standards instead of proprietary APIs. You are encouraged
to join this team by getting
involved.
How is mozilla.org using Gecko?
mozilla.org will assemble the Gecko layout engine and other browser
components into the Mozilla browser application.
How is Netscape planning to use
Gecko?
Gecko lies at the heart of Communicator, powering all of the individual
components including Navigator and Messenger. Gecko technologies will also
power the display of Netcenter, the Web's leading portal site, speedily
delivering more exciting content and services. Gecko's architecture will
serve Netscape well into the future, enabling faster time to market, more
innovation, less costly development, easier distribution and updating,
and better cross platform support.
How can other
companies and organizations use Gecko?
Because Gecko is small, lightweight, and open source, other companies
and organizations can easily reuse it. Many hardware vendors are creating
devices with network access and wish to include web browsing functionality.
Likewise, many software developers want to include Web browsing capability
in their applications, but don't want to independently develop browser
software. These developers can pick and choose the browser components they
want from among those that Gecko offers, and package these components alongside
their own within their finished products.
Which open standards does Gecko
support, and to what extent does it support them?
The first release of Gecko will support the following recommended open
Internet standards completely (100%) unless specifically noted:
-
HTML 4.0 - complete support except for bidirectional text layout, which
is only used in Hebrew and Arabic
-
Style Sheets
-
CSS 1 - complete support
-
CSS 2 - partial support is expected and has already been built into Gecko,
but no specific level of support has been committed
-
DOM
-
Level 0
-
Level 1 Core
-
Level 1 HTML
-
XML 1.0
-
JavaScript 1.5, including ECMA-262 (ECMAscript) compliance
-
Transfer protocols: HTTP, FTP, Gopher
-
SSL
-
Unicode
-
OJI (Open Java Interface)
-
Image formats
How will Gecko format XML documents?
Gecko will support the use of CSS1 to format XML documents.
For XML formatting, why is Gecko supporting
CSS rather than XSL in the first release?
Simple: CSS1 is a finished, fully adopted, and mature two-year-old standard;
XSL isn't done yet. As Tim Bray, the coeditor of the XML standard, has
written:
"Microsoft's XSL efforts are very impressive, but (readers
will pardon us being something of a broken record on this subject) XSL
is in the future. We are convinced that from the point of view of the largest
number of users, the most important things that Microsoft could do in IE
5 would be:
1.Ensure interoperability of XML and stylesheets with other browsers,
and
2.Build in conformance to existing, stable, well-understood standards
such as CSS 1.0.
Innovation, of course, is fine and necessary, and we salute Microsoft's
leadership in this area. But innovation needs to be built on a foundation
of interoperability and playing by existing well-understood rules." He
further adds that "It seems obvious to me that for anyone who wants to
deploy XML in production mode right now, XML + CSS is the way to go …"
("Microsoft Outlines XML Support in IE5 Beta 2" at
http://www.xml.com/xml/pub/98/10/ie5-2.html)
How does Gecko help content developers?
Content developers are sick and tired of developing and testing every
single web page multiple times in order to support the different, incompatible,
proprietary DOMs of browsers from different vendors. They have been demanding
that all vendors fully support the W3C DOM and the other standards listed
above so that they can (1) have a rich, powerful formatting system and
object model at their disposal, and (2) "write once, view anywhere." Gecko's
full support of HTML 4.0, CSS1, DOM1, XML, XML+CSS1, and RDF will make
Gecko the content platform of choice for content developers worldwide.
Are Gecko's APIs based on
ActiveX? COM? JavaBeans?
Gecko is reusable on all platforms thanks to XPCOM, a subset of COM
that works across platforms. COM, developed by Digital and later adopted
by Microsoft, is the de facto standard for modular interfaces on Windows
platforms. Additionally, on the Windows platform, Gecko's XPCOM interfaces
are wrapped in an ActiveX control that VB developers can utilize (ActiveX
wrappers are not available on other platforms because ActiveX is a Windows-only
technology). A JavaBean wrapper is not currently under development, but
there is nothing in Gecko's architecture that precludes such development
in the future. Source code and documentation for these interfaces are available
through mozilla.org.
Are Gecko's APIs compatible
with Microsoft's Trident APIs?
Gecko's XPCOM interfaces are different than Microsoft's. The most important
differences between the two models involve reflection of the Document Object
Model (DOM) in the interfaces. Microsoft's Trident interfaces reflect the
DOM in a proprietary API, whereas Gecko exposes the DOM according to the
W3C's recommended standard. Other incompatibilities exist. Adam Lock is
creating a partial compatibility layer that may enable developers to easily
migrate from Microsoft's engine to the NGLayout engine.
Which platforms does Gecko run on?
Gecko runs today on Win32 (Windows 95, Windows 98, Windows NT 4, Windows
NT 5), PowerMac, and Linux. OEMs and contributors from the Net participating
in mozilla.org will port Gecko to other platforms. Such porting efforts
are underway for Solaris, Irix, OS/2, and BeOS, among others.
What are the components
of Gecko?
Gecko includes the following components:
-
Document parser (handles HTML, XML, and arbitrary document types)
-
Layout engine with content model
-
Style system (handles CSS, etc.)
-
JavaScript runtime
-
Image rendering library
-
Networking library
-
Platform-specific graphics rendering and widget sets for Win32, X, and
Mac
-
User preferences library
-
Navigator plug-in interface
-
Open Java Interface (OJI), with Sun Java 1.2 JVM
-
RDF hypertree back end
-
Font library *
-
Security library *
-
Cache management system *
Components marked with an asterisk are currently being extracted from the
5.0 codebase and given XPCOM interfaces and haven't yet landed in the Gecko
tree.
|
