Variable lists present a challenge for formatting because the term hanging out to the left can be of any width. There are several methods for setting the term width, which is effectively the indent width of the listitem paragraphs. Here is the list of methods, with highest priority first.

The first two methods put each varlistentry into a pair of fo:blocks with the term block preceding the list item block. This has the effect of stacking the term above the paragraph, permitting the term to be of any length. The paragraph is indented a small fixed amount. The use of the variablelist.as.blocks parameter turns this behavior on globally for all variablelists. The processing instruction turns it on for one list. The following is an example.

<variablelist>  
<?dbfo list-presentation="blocks"?> 
  <varlistentry>
    <term>Left button</term>
    <listitem><para>Blah blah</para></listitem>
  </varlistentry>
  ...
</variablelist>

Although the variablelist.as.blocks parameter is a global setting, you can override it for individual lists with a <?dbfo list-presentation="list"?> processing instruction. Then you can also specify a term width.

If the list is not formatted as blocks, then the list is formatted using a fo:list-block, which puts the list item text side-by-side with the term. Then the term width can be set by either a processing instruction or an attribute value. Following is an example of that processing instruction.

<variablelist>  
<?dbfo term-width=".75in"?> 
  <varlistentry>
    <term>Left button</term>
    <listitem><para>Blah blah</para></listitem>
  </varlistentry>
  ...
</variablelist>

The term-width value can be a plain number also, in which case it is assumed to be in em units. The termlength attribute of variablelist can be set in a similar manner if the processing instruction is not used.

If you don't set a term width with any of the above methods, then the XSL-FO stylesheet counts the characters in all the term elements and uses the largest, up to some maximum value. Starting with version 1.62 of the stylesheets, the maximum indent width is controlled by the variablelist.max.termlength stylesheet parameter. The default value is 24, roughly 24 character widths. Enter a different integer to change the maximum indent. Any terms that are longer will line wrap. If this default behavior does not produce satisfactory results in a given list, then adjust the indent with one of the methods described above.

Variable lists present a challenge for formatting in HTML because the standard DL list in HTML doesn't let set the indent width. The DocBook XSL stylesheets support a set of processing instructions (PIs) to enable you to control how a given variablelist is formatted in HTML. For HTML output, the list can be put into a two-column HTML TABLE element to control formatting. Following is an annotated example:

<variablelist>  
<?dbhtml list-presentation="table"?> 
<?dbhtml term-width="15%"  list-width="85%" ?>  
<?dbhtml term-presentation="bold" ?>  
<?dbhtml term-separator=":" ?>  
<?dbhtml table-summary="mouse buttons described" ?>  
  <varlistentry>
    <term>Left button</term>
    <listitem><para>Blah blah</para></listitem>
  </varlistentry>
  ...
</variablelist>

	Put the processing instructions somewhere inside the variablelist element. You can put them all into one PI, or make separate PIs for each.
	This PI enables the formatting PIs to work. It tells the stylesheet to use an HTML TABLE instead of a DL list for this variable list. If you want to always output tables for variablelists, then you can instead set the stylesheet parameter variablelist.as.table to 1. Then you can omit this PI, except when you want to force a particular list to use DL, in which case you use <?dbhtml list-presentation="list" ?>.
	This PI sets the table left column width (term-width) and the overall table width (list-width). Use percentages for the values. If you omit both, you get the default HTML table formatting.
	This PI lets you change the font style for all the terms in a variablelist. The choices are bold, italic, bold-italic. In general, such formats should be applied with a CSS stylesheet, but this can be useful for a list that needs different formatting.
	This PI lets you add some punctuation or any other text after every term in the list. In this example, each term will be followed by a colon.
	You can supply a text string that is put into the HTML table's summary attribute.