Improve documentation of args.hdf

[stefan-jung]

It is possible to inject code into the HTML header using a hdf file, that can be passed using the args.hdf parameter. A hdf file must be a valid XML file. Therefore it needs to have a root element. So it is not possible to inject multiple elements.

Valid:

<link rel="stylesheet" type="text/css" href="flag-icon.min.css"><!----></link>

Invalid:

<link rel="stylesheet" type="text/css" href="flag-icon.min.css"><!----></link>
<script src="jquery.min.js"><!----></script>

But there is a template in dita2htmlImpl.xsl which unwraps a root <div> element, if it exists.

<!-- For header file processing, pull out the wrapping DIV if one is there -->
<xsl:template match="/div" mode="add-HDF">
  <xsl:apply-templates select="*|comment()|processing-instruction()|text()" mode="add-HDF"/>
</xsl:template>

Valid:

<div>
  <link rel="stylesheet" type="text/css" href="flag-icon.min.css"><!----></link>
  <script src="jquery.min.js"><!----></script>
</div>

Currently this is not explained in the docs, see HTML-based output parameters -> args.hdf.

@infotexture: Could you please explain that in the docs?

[infotexture]

See the updated topic in Development version of the documentation.

[stefan-jung]

Thanks a lot