Plug-ins and HTML

Embedded plug-ins are loaded by Navigator when the user encounters an HTML page with an embedded object with a MIME type registered by a plug-in. When loaded, an embedded plug-in is displayed as part of the HTML document in a rectangular subpart of the page. This is similar to how a GIF or JPEG image is embedded, except that the plug-in can be live and respond to user events (such as mouse clicks).

Plug-in objects are embedded in an HTML page by using the EMBED tag. The syntax of the EMBED tag is:

<EMBED attributes> ... </EMBED> 

• HEIGHT="value" defines the horizontal location of the plug-in in the HTML page. The unit of measurement is optionally defined by the UNITS attribute.

• HIDDEN="value" indicates whether the plug-in is visible on the page. The value can be either true (the default) or false. A value of true overrides the values of HEIGHT and WIDTH, making the plug-in zero-sized. Always explicitly set HIDDEN=true to make an invisible plug-in (rather than simply setting the HEIGHT and WIDTH to zero).

• PALETTE="value" indicates the mode of the plug-in's color palette. The value can be either foreground or background (the default). The palette mode is only relevant on the Windows platform.

• PLUGINSPAGE="URL" indicates the location of instructions on installing the plug-in. The value URL is a standard uniform resource locator. The URL is used by the assisted installation process if the plug-in registered for the MIME type of this EMBED tag is not found.

• SRC="URL" optionally indicates the location of the plug-in data file. The value URL is a standard uniform resource locator. The MIME type of the file (typically based on the file-name suffix) determines which plug-in is loaded to handle this EMBED tag. Either the SRC attribute or the TYPE attribute is required in an EMBED tag.

• TYPE="type" optionally indicates the MIME type of the EMBED tag, which in turn determines which plug-in is loaded to handle this EMBED tag. Either the SRC attribute or the TYPE attribute is required in an EMBED tag. Use TYPE instead of SRC for plug-ins that require no data (for example, a plug-in that draws an analog clock) or plug-ins that fetch all their data dynamically.

• WIDTH="value " optionally defines the vertical location of the plug-in in the HTML page. The unit of measurement is optionally defined by the UNITS attribute.

• UNITS="value" defines the measurement unit used by the HEIGHT and WIDTH attributes. The value can be either pixels (the default) or en (half the point size).

In addition to these standard attributes, plug-ins may optionally have private attributes to communicate specialized information between the HTML page and the plug-in code. Navigator ignores all non-standard attributes when parsing the HTML, but passes all attributes to the plug-in, allowing the plug-in to examine the attribute list for any private attributes that may modify its behavior.

For example, a plug-in that displays video could have private attributes to determine whether the plug-in should automatically start playing the video, and whether the video should automatically loop on playback. Thus an example EMBED tag could be:

Navigator would interpret the SRC tag to load the data file and determine the MIME type of the data, and the WIDTH and HEIGHT tags to size the area of the page handled by the plug-in to be 320 by 200 pixels. Navigator would simply ignore private attributes AUTOSTART and LOOP and pass them to the plug-in with the rest of the attributes. The plug-in could then scan its list of attributes to see if it should automatically start the video and loop it on playback.