Trident

Trident (also known as MSHTML) is the name of the layout engine for the Microsoft Windows version of Internet Explorer. It was first introduced with the release of Internet Explorer version 4.0 in October 1997; it has been steadily upgraded and remains in use today. For versions 7 and 8 of Internet Explorer, Microsoft made significant changes to the Trident layout engine to improve compliance with web standards and add support for new technologies.^{[citation needed]}

Use in software development

Trident was designed as a software component to allow software developers to easily add web browsing functionality to their own applications. It presents a COM interface for accessing and editing web pages in any COM-supported environment, like C++ and .NET. For instance, a web browser control can be added to a C++ program and Trident can then be used to access the page currently displayed in the web browser and retrieve element values. Events from the web browser control can also be captured. Trident functionality becomes available by linking the file mshtml.dll to the software project.

Versions

Internet Explorer 8 is the first version to include the Trident version in the user agent string. Before that, the Trident engines weren't independently versioned.

Trident-based applications

All versions of Internet Explorer for Windows from 4.0 onwards use Trident, and it is also used by various other web browsers and software components (see Internet Explorer shells). In Windows 98, Windows Me, and Windows 2000, it is also used for the Windows file manager/shell, Windows Explorer. The Add/Remove Programs tool in Windows 2000 and Windows XP uses Trident to render the list of installed programs and in Windows XP, it is also used for the User Accounts Control Panel, which is an HTML Application. Trident however was not used by the Internet Explorer for Mac (which uses Tasman), nor by Internet Explorer Mobile.

Some other Trident-based applications include:

• AOL Instant Messenger 6.x, which uses Trident to render conversation and profile windows, and advertisement panels
• Ares Galaxy
• Avant Browser
• EA Link, incompatible with Trident as of Internet Explorer 7 RC2
• Google Talk, which uses Trident to render chat windows and profile cards
• IE Tab, a Firefox add-on used to render pages with Trident within the Firefox chrome
• LimeWire, which renders the page 'New@Lime'
• Lunascape, developed by Lunascape Corporation
• Maxthon, which uses the Trident engine while adding features not built into IE7
• Microsoft Compiled HTML Help
• Microsoft Encarta and related products
• Microsoft InfoPath
• Microsoft Outlook which uses Trident to render HTML Messages (prior to Outlook 2007) and the "Outlook Today" screen
• Microsoft Outlook Express, which uses Trident to render HTML Messages
• MSN Messenger, which uses it to produce Flash-based "winks" and games, and for all advertisements shown in the advertisement banner
• Netscape Browser (Netscape 8), which used Trident to render web pages in IE mode
• Pyjamas, a python Widget set Toolkit. Embedding IWebBrowser2 as an Active-X component and accessing the COM interface, Pyjamas uses Trident for the Desktop version, through the python win32 "comtypes" library.
• RealNetworks
• Sleipnir, a web browser
• Teega
• TomeRaider
• Valve's Steam client, which uses Trident to render the "Store", "Update News" and "Community" sections as well as the Steam in-game browser and MOTD screens in Valve games
• Windows Media Player, which uses Trident to render the "Media Information" pages; other media players, such as Winamp and RealPlayer, have similar features.

Standards compliance

Although each version of IE has improved standards support, including the introduction of a "standards-compliant mode" in version 6, the core standards that are used to build web pages (HTML and CSS) are sometimes implemented in an incomplete fashion. For example, there was no support for the <abbr> element which is part of the HTML 4.01 standard prior to IE 8. There are also some CSS attributes missing from Trident, like min-height, etc. as of IE 6. As of Internet Explorer 8 CSS 2.1 will be fully supported as well as some CSS 3.0 attributes.^[3] .Trident also does not pass the Acid3 test, with a score of 20/100.

Microsoft alternatives

Apart from Trident, Microsoft also has several other layout engines. One of them, known as Tasman, was used in Internet Explorer 5 for Mac. Development of Internet Explorer for Mac was halted in roughly 2003, but development of Tasman continued to a limited extent, and was later included in Office 2004 for Mac. Microsoft's new web design product, Expression Web does not use Internet Explorer's Trident engine, but rather its own engine, which Microsoft claims is more standards-compliant than Trident.^[4]

See also

• List of layout engines
• Comparison of layout engines
• Internet Explorer shell

References

External links

• MSDN - MSHTML Reference
• On Internet Explorer misrendering