Netscape Gecko Browsers and Plugins

Arun K. Ranganathan, Netscape Communications.  Feedback

Introduction

Contents

• A Definition of Terms
  
• General Recommendations
• Plugin Tips and Strategies For Web Developers
  
• Windows Media Player
• RealPlayer
• QuickTime
  
• Macromedia Flash
• Java
  
• Additional Development Resouces
• Developing your own plugin
• A word on installer technology 
• SmartUpdate vs. XPInstall
• Netscape Gecko's equivalent to ActiveX Controls
  

A Definition of Terms

• A plugin (often "plug-in") is a component that is installed into the browser application plugins directory.  It typically is a small component (on Windows, a DLL) that handles a MIME type and is built using the Netscape Plugin API by companies such as Macromedia, Real, Microsoft, and Adobe.  A plugin allows web developers to play embedded or streaming media content directly in a web browser window, and often the plugin exposes methods of its own to JavaScript (see Scriptability).  A plugin is typically invoked via special HTML tags for that purpose, such as the EMBED tag or the OBJECT tag.  
• Scriptability is the ability of the plugin to interact with JavaScript in web pages.  This feature allows web sites to create streaming media experiences that have DHTML user interfaces to drive plugin events.  An example of this would be JavaScript-driven "Play" and "Pause" buttons in HTML, which would then allow the end user to "Play" or "Pause" active content in a plugin's area by clicking on HTML buttons.  This feature is useful for those wishing to combine DHTML, JavaScript and streaming media to create interactive user experiences.
• A Helper Application is an application that is launched upon encountering a given media format, and "helps" enhance browser functionality by launching a specific application to play the specified content.  Typically, this is media content that is not intended to be embedded within a browser window, but is content that will exist outside the browser's context, unless the application in question is designed to always play the content inside a browser window.  An example is given below for Windows Media Player.  See also a definition of MIME types.
  
  

General Recommendations 

1. All Netscape Gecko browsers (except the standalone Mozilla browser) on Windows ship with RealPlayer 8. This means that on Windows, when installing the latest Netscape browser, you have the choice of installing RealPlayer 8 also. 
2. In Netscape Gecko browsers, RealPlayer 8 and RealOne support scripting between the embedded player (plugin) and web pages at this time.  This is an important feature for those who want DHTML user-interfaces (e.g. JavaScript-driven "Play" and "Pause" buttons) and in general, want scripting of media plugins.  Microsoft's Windows Media Player does not currently support scripting between the player and the Mozilla-based browser.
3. RealPlayer supports a wide variety of codecs and media types.

1. Macromedia's latest Flash player, released in July 2002.  The scriptable versions are Flash 6 r40 and onwards.  Versions before Flash 6 r40 worked with Netscape Gecko browsers, but were not scriptable.  See the section on Flash for more information.
2. Apple's Quicktime 6 player, which is now fully scriptable.  Quicktime 6 and onwards are scriptable in Netscape Gecko browsers, but Quicktime 5.x and before are not scriptable in Netscape Gecko browsers.  See the section on Quicktime for more information.
3. The Viewpoint player, for 3D animation and graphics viewing.  Viewpoint's MetaStream plugin will ship with Netscape 7.0.
4. RealPlayer 8, bundled with Netscape browsers, including Netscape 7.0 PR1 and later.  Note that RealPlayer 8 is considered a legacy product by RealNetworks.
5. RealOne player, which is RealNetworks latest revision to their player.  This version is not bundled with Netscape browsers, but is available for download from http://www.realone.com/ .  In particular, click here to download the free RealOne player .

1. Most of these plugins can be invoked with a unique MIME type that is different from the actual MIME type of the file being deployed.  This unique MIME type is called an invocation MIME type in this article, and is a MIME type determined by the plugin manufacturer.  This means that the MIME type that the type attribute refers to in both the OBJECT and the EMBED tag need not match the MIME type of the source being referred to in the data or src attributes respectively.  This is best seen with some examples for Real and Windows Media Player that are described later in this document.  Invocation MIME types are useful because they allow you to invoke a specific plugin, despite the configuration of the end-user's hard drive.
2. It is possible to use the OBJECT tag with Netscape Gecko browsers (to be W3C compliant in HTML 4.01 and XHTML), and it is recommended that you nest your OBJECT tags for Gecko-based browsers inside the OBJECT tags for IE as shown in the example.  However, the OBJECT tag usage in Netscape Gecko browsers is subject to a few caveats:
• Only recent browsers bearing a bug fix allow the OBJECT tag the ability to retrieve missing plugins via MIME type lookup.
• The use of the data attribute with the OBJECT tag is currently dependent on how the actual plugin is implemented.  This situation will change when the affiliated bug is fixed.  This means that you can invoke a plugin with the OBJECT tag and param tags as a workaround to gain equivalency to the use of the data attribute, as in the case of the Windows Media Player example.
3. It is best to nest your EMBED tag within your OBJECT tag -- this has been the mechanism of invoking both ActiveX controls for IE and Netscape plugins for Netscape browsers ever since the release of Netscape Communicator 4.x
4. You can use JavaScript to determine what plugins are installed in the browser, and what versions of the plugins are installed.  These techniques are mentioned in the section on QuickTime.

Popular Plugins

RealPlayer

Recommendations:

• RealPlayer 8 and RealOne support a variety of popular audio and video formats, and can be invoked to handle these as either plugins or helper applications, depending on how a user has configured their RealPlayer:
• Audio: mp1, mp2, and mp3, ra files (RealPlayer only), wav, midi, aiff, au
• Video: rv files (RealPlayer only), rm or ram files (RealPlayer only), mpeg, avi

• In certain situations, although RealPlayer 8 (or RealOne) can handle the media type, the plugin may not automatically handle the MIME type associated with that media type.  This depends entirely on how the media player is configured. Fortunately, by way of invocation MIME types it is possible to invoke the RealPlayer 8 (or RealOne player) as a plugin regardless of how the end-user's machine is configured.  Here are some markup examples using the EMBED tag:
• Audio WAV files: <embed type="audio/x-pn-realaudio-plugin" width="200" height="200" src="http://www.student.oulu.fi/%7esairwas/object-test/audio/test.wav"> 
• Audio MIDI files: <embed type="audio/x-pn-realaudio-plugin" width="200" height="200" src="http://www.mozilla.org/quality/browser/front-end/testcases/plugins/bcosofu.mid"> 
• Video (AVI) files:  (right click to play):
  <embed controls="ImageWindow" type="audio/x-pn-realaudio-plugin" width="400" height="400" src="http://www.geocities.com/MotorCity/Pit/3571/martial/mikemookjong2.avi">

Windows Media Player 

• Launch as a helper app.  Applications on your PC are configured to handle certain types of files.  If, for example, I configure Windows Media Player to handle AVI files, and then send the browser an AVI file over HTTP (e.g. by having the user click on a URL that links to an AVI file), then the user will be shown a dialog box with the following choices:
• To open the file with avifile, a component inside Windows Media Player, OR
• To Save the File to Disk, which is always an option in case the user wants to save the file and retrieve it later.
• Here's an example of this: http://www.geocities.com/MotorCity/Pit/3571/martial/mikemookjong2.avi .  Clicking on this URL should spawn the helper application that is the default handler for AVI.  Chances are, it is either QuickTime, RealPlayer, or Windows Media Player.

• Embed plugin on a web page.   Here are two ways of doing this:
• Using OBJECT tag:   <object type="application/x-mplayer2" height="500" width="500"> <param name="src"        
  value="http://www.geocities.com/MotorCity/Pit/3571/martial/mikemookjong2.avi">
  </object>

• Using EMBED tag: <embed type="application/x-mplayer2" height="500" width="500" height="500" src="http://www.geocities.com/MotorCity/Pit/3571/martial/mikemookjong2.avi" pluginspage="http://www.microsoft.com/windows/windowsmedia/download/default.asp"></embed>

• Scriptability of controls: Microsoft has not updated the Windows Media Player to enable JavaScripting between an embedded plugin and a web page. (We hope they will upgrade their functionality in the future.) To workaround this limitation, we recommend:
1. Offering RealPlayer as an option.
2. Detecting that the browser is a Netscape Gecko browser, and embedding Windows Media Player with player determined controls.  The attributes of the EMBED tag determine how to show and mask the control panel for the embedded player.  In particular, there are custom attributes that can be used to show or hide the control panel, or to determine if the content should loop.  Determine whether the vendor provides custom attributes that can accomplish the user-interface effect you are seeking, in lieu of using JavaScript.
   
   
• AVI file handing with the video/avi MIME Type.  The Netscape-style plugin made by Windows Media Player will handle AVI MIME Types, so in order to force Windows Media Player to handle AVI, you will need to use an invocation MIME type as outlined above. 
  

QuickTime

• Launch the QuickTime standalone application.
• Go to Edit | Preferences | QuickTime preferences from the menu.
• Choose Browser plug-in from the drop down list, and click on MIME settings.

Recommendations:

• You can deploy scriptable content if you wish, since QuickTime 6 is fully scriptable and available for download.  It is a good test bed to test against.  You can detect whether your content is running against non-scriptable versions of QuickTime by looking at the plugins array and determining the version.  Versions less than "6" are not scriptable.
• You can offer a QuickTime option in addition to your Windows Media Player or RealPlayer options, and you can restrict users to QuickTime 6 if you wish, once again, by determining the version.
  

Macromedia Flash

Recommendations:

• Scripting Flash animation: You may wish to deploy content that scripts the Flash plugin, in which case you ought to detect the presence of Flash 6 r40 by looking at the plugins array description field.  If you are bound to using the scriptability or the FSCommands capabilities of the Flash plugin, look for Flash 6 r40 and above.  You can determine version increments as those being greater than '40' in the Flash 6 series, or greater than '6.'  The best way to keep abreast of Macromedia's "dot-releases" is to look at the Macromedia homepage.
  
  
• Known Flash 6 / Netscape Gecko bugs:
• One of the top issues is a persistent CPU drainage discussed extensively in an entry in the Bugzilla open source bug database.  Macromedia has resolved to fix this soon.
  

Java

Recommendations and Caveats:

• Although the APPLET element is deprecated in the current HTML DTD, you may choose to use it.  Using EMBED and OBJECT are not necessary, unless your use of OBJECT is for full XHTML validation or HTML 4.01 compliance.  You may invoke the Java Plugin using the OBJECT tag in two of the following possible ways:
• You can use the classid attribute of the OBJECT tag: <object classid="java:MyClassName.class"....> .  This is the only classid that Netscape Gecko browsers support, since most classid attributes used with OBJECT tags in the web today refer to the UUIDs associated with IE's ActiveX controls.  Netscape Gecko does not support ActiveX.
• You can use the type attribute to refer to a known Java MIME type: <object type="application/x-java-applet;jpi-version=1.4.0_01" data=MyClassName.class"....>
  

• Always fully test your Java application using the latest JRE provided by Sun.
  

• Be aware of the change in security model.  Sun's JVM does not use the Netscape Communicator 4.x Capabilities API for security model.  Instead, the Java Virtual Machine uses Sun's Java 2 Security Model (and policy files).  
  

Additional Development Resources

Building Your Own Netscape-style Plugin

• LiveConnect, or the JRI | JNI Bridge to script plugins in Netscape Communicator 4.x, is no longer supported in Netscape Gecko-based browsers.  If you want to expose your plugin to JavaScript, you'll want to read this article.
• Similarly, if you want your plugin to be able to access the Web page's JavaScript, read this article.
  
• Since LiveConnect is no longer supported as the architecture to script plugins, the old Communicator 4.x Plugin API documentation has been upgraded to include the subset of material that only Netscape Gecko supports.  We will publish this API soon -- for the time being, it lives here.
• The central reference area for plugin development is the Plugins Project Page on mozilla.org .

Installing Your Plugin

SmartUpdate vs. XPInstall

• XPInstall has a JavaScript API and uses JavaScript as the install logic.
• XPI packages are ZIP packages, and in fact are used by mozilla.org to install browser components such as chrome.

• Although the CompuServe browser is based on Netscape Gecko, the CompuServe browser does not support XPInstall.  Other AOL Time Warner browsers such as Netscape 6.x and 7.0 do support XPInstall, and the AOL beta provides support for it as well.
• Unlike SmartUpdate, XPInstall in its current iteration is not a signed technology.  There are no digital signatures affiliated with XPI packages.  Instead, the end-user is asked whether they want to download and install the package from a given URL or not.  The dialog box looks like this:  

Netscape Gecko's Equivalent to ActiveX Controls

Equivalent Mechanisms in Netscape Gecko-based browsers

• Netscape Plugin API (NPAPI) --  technically, major "ActiveX-only" or "ActiveX-optimized" components such as Windows Media Player and b3d Projector can be rewritten using the Netscape Plugin API.  Components can  be made scriptable and there is some "open source" support for  making Netscape-style plugins work in IE 6 and up, which do not support the NPAPI .    


• Signed JavaScript is another option.  Signed JavaScript is "vouched for" by a third-party Certificate Authority, so users can trust it, and it can be used to do a variety of "native application" type tasks -- open files, open network connections, write to the disk, etc.  One of the ways this is accomplished is via XPConnect and the UniversalXPConnect privilege, which calls upon the known XPCOM environment to do various  tasks that ordinary web-delivered JavaScript can not do. The DevEdge Security Central provides an aggregate of information about how to extend the browser's capabilities beyond "the sandbox."

• chrome:// and XUL are windowing toolkit technologies which can create compelling applications outside the context of DHTML and a webpage. Using XUL/JavaScript and jar files deployed with a suitable XPInstall, you can really enhance the features of the browser.  

• Java Applets have traditionally been juxtaposed with ActiveX.  Example: MSN's chat client is an ActiveX component (for IE) and a plugin for Netscape 4.x.  CompuServe uses Java for chat applications.