Example: Creating a simple PDF plug-in

This scenario walks through the process of creating a very simple plug-in (com.example.print-pdf) that creates a new transformation type: print-pdf.

The print-pdf transformation has the following characteristics:

Uses A4 paper
Renders figures with a title at the top and a description at the bottom
Use em dashes as the symbols for unordered lists
In the plugins directory, create a directory named com.example.print-pdf.
In the new com.example.print-pdf directory, create a plug-in configuration file (plugin.xml) that declares the new print-pdf transformation and its dependencies.

``` <?xml version="1.0" encoding="UTF-8"?> <?xml-model href="https://www.dita-ot.org/rng/plugin.rnc" type="application/relax-ng-compact-syntax"?>

```
Add an Ant script (integrator.xml) to define the transformation type.

<?xml version='1.0' encoding='UTF-8'?> <project> <target name="dita2print-pdf" depends="dita2print-pdf.init, dita2pdf2"/> <target name="dita2print-pdf.init"> <property name="customization.dir" location="${dita.plugin.com.example.print-pdf.dir}/cfg"/> </target> </project>
In the new plug-in directory, add a cfg/catalog.xml file that specifies the custom XSLT style sheets.

<?xml version="1.0" encoding="UTF-8"?> <catalog prefer="system" xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"> <uri name="cfg:fo/attrs/custom.xsl" uri="fo/attrs/custom.xsl"/> <uri name="cfg:fo/xsl/custom.xsl" uri="fo/xsl/custom.xsl"/> </catalog>
Create the cfg/fo/attrs/custom.xsl file, and add attribute and variable overrides to it.

For example, add the following variables to change the page size to A4.

<?xml version="1.0" encoding="UTF-8"?> <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="2.0">  <xsl:variable name="page-width">210mm</xsl:variable> <xsl:variable name="page-height">297mm</xsl:variable> </xsl:stylesheet>
Create the cfg/fo/xsl/custom.xsl file, and add XSLT overrides to it.

For example, the following code changes the rendering of figure elements.

<?xml version="1.0" encoding="UTF-8"?> <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:fo="http://www.w3.org/1999/XSL/Format" version="2.0">  <xsl:template match="*[contains(@class,' topic/fig ')]"> <fo:block xsl:use-attribute-sets="fig"> <xsl:call-template name="commonattributes"/> <xsl:if test="not(@id)"> <xsl:attribute name="id"> <xsl:call-template name="get-id"/> </xsl:attribute> </xsl:if> <xsl:apply-templates select="*[contains(@class,' topic/title ')]"/> <xsl:apply-templates select="*[not(contains(@class,' topic/title ') or contains(@class,' topic/desc '))]"/> <xsl:apply-templates select="*[contains(@class,' topic/desc ')]"/> </fo:block> </xsl:template> </xsl:stylesheet>
Create an English-language variable-definition file (cfg/common/vars/en.xml) and make any necessary modifications to it.

For example, the following code removes the period after the number for an ordered-list item; it also specifies that the bullet for an unordered list item should be an em dash.

<?xml version="1.0" encoding="UTF-8"?> <variables>  <variable id="Ordered List Number"> <param ref-name="number"/> </variable>  <variable id="Unordered List bullet">—</variable> </variables>

Tip: The files for this sample plug-in are included in the DITA-OT installation directory under docsrc/samples/plugins/com.example.print-pdf/ and on GitHub.

The plug-in directory has the following layout and files:

com.example.print-pdf
├── cfg
│   ├── catalog.xml
│   ├── common
│   │   └── vars
│   │       └── en.xml
│   └── fo
│       ├── attrs
│       │   └── custom.xsl
│       └── xsl
│           └── custom.xsl
├── integrator.xml
└── plugin.xml

Run dita --install to install the plug-in and make the print-pdf transformation available.
Build output with the new transformation type to verify that the plug-in works as intended.

dita --input=my.ditamap --format=print-pdf

Related information

Installing plug-ins