How to Style Codeblocks with a Zebra Effect

A possible requirement for your <codeblock> elements could be to alternate the background color on each line. Some advantages of this technique is that you can clearly see when text from the <codeblock> is wrapped.

This effect can be done by altering the HTML5 output, creating a div for each line from the code block, then styling them.

To add this functionality using an Oxygen Publishing Template, follow these steps:

1. If you have not already created a Publishing Template, you need to create one. For details, see How to Create a Publishing Template.
2. Link the folder associated with the publishing template to your current project in the Project view.
3. Using the Project view, create an xslt folder inside the project root folder.
4. In this folder, create an XSL file (for example, named merged2html5Extension.xsl) with the following content:

   <?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"
     exclude-result-prefixes="xs"
     version="2.0">
   
     <xsl:template match="*[contains(@class, ' pr-d/codeblock ')]">
       <xsl:variable name="nm">
         <xsl:next-match/>
       </xsl:variable>
       <xsl:apply-templates select="$nm" mode="zebra"/>
     </xsl:template>
   
     <xsl:template match="node() | @*" mode="zebra">
       <xsl:copy>
         <xsl:apply-templates select="node() | @*" mode="#current"/>
       </xsl:copy>
     </xsl:template>
   
     <xsl:template match="*[contains(@class, ' pr-d/codeblock ')]" mode="zebra">
       <xsl:element name="{name()}">
         <xsl:copy-of select="@*"/>
         <xsl:attribute name="class" select="concat(@class, ' zebra')"/>
         <xsl:analyze-string regex="\n" select=".">
           <xsl:matching-substring/>
           <xsl:non-matching-substring>
             <div>
               <xsl:value-of select="."/>
             </div>
           </xsl:non-matching-substring>
         </xsl:analyze-string>
       </xsl:element>
     </xsl:template>
   
   </xsl:stylesheet>

5. Open the template descriptor file associated with your publishing template (the .opt file) and set the XSLT stylesheet created in the previous step with the com.oxygenxml.pdf.css.xsl.merged2html5 XSLT extension point:

   <publishing-template>
     ...
     <pdf>
       ...        
       <xslt>
         <extension 
           id="com.oxygenxml.pdf.css.xsl.merged2html5"
           file="xslt/merged2html5Extension.xsl"/>
       </xslt>

6. Create a css folder in the publishing template directory. In this directory, save a custom CSS file with rules that style the <codeblock> structure. For example:

   .zebra {
     padding: 0;
   }
   
   .zebra > *:nth-of-type(odd) {
     background-color: lightgray;
   }

7. Open the template descriptor file associated with your publishing template (the .opt file) and reference your custom CSS file in the resources element:

   <publishing-template>
     ...
     <pdf>
       ...                
       <resources>            
         <css file="css/custom.css"/>
       </resources> 

8. Edit the DITA Map PDF - based on HTML5 & CSS transformation scenario.
9. In the Templates tab, click the Choose Custom Publishing Template link and select your template.
10. Click OK to save the changes and run the transformation scenario.