Stepping Through the Example

Careful readers will note that the first thing we see is a $t specification for <ulink> tags, and you'll also note that the included docbook_tags.xps contains a specification for <ulink>. The reason is to override the default behaviour for ulink tags in the print version of my articles to contain a reference that we can use later in a list of links. We can also see that this specification uses a testcode parameter that we haven't encountered before. We'll see how and why that's used later in The Template Hash.

Next we see the findvalue() function used exactly as we already saw in Extracting Values.

Then we have a section with a comment marked: "display Title/TOC page". This uses the apply_templates() function with an XPath expression. Note that rather than use the <%= %> delimiters around the apply_templates() call, we simply use the print function. This has the same effect, and is used here to show the flexibility in this approach.

The main part of the code loops through all sect1 tags, and calls apply_templates on those nodes. Note how this is another demonstration of Perl's TMTOWTDI (There's More Than One Way To Do It) approach - the same code could have been written:

<%= apply_templates("/article/sect1") %>

Finally, because this is the print version of our article, we provide a list of links so that people viewing a printed version of this article can type in those links, and they can also refer to the link by reference number, as we saw earlier. We use the hash of links in the %links variable that we built in the testcode handler for our ulink template.

The other file, docbook_tags.xps, is included only in part here, to demonstrate a few of the transformations we're applying to various docbook article tags. We can see that we're turning <para> tags into <p> tags, and doing some more complex processing with testcode to <title> tags. We'll see in The Template Hash exactly what testcode allows us to achieve.