XSL: Preserving line feeds, tabs, and spaces in data while still wrapping text

I had data in XML that had line feeds, spaces, and tabs that I wanted to preserve (so I couldn't use

) but I also wanted the lines to wrap when the side of the screen was reached (so I couldn't use

).

After some research and help from a co-worker (Patricia Eromosele) I made the XSL template below that achieves that. An example of how to call it follows:

    <p>
                    <xsl:call-template name="prewrap">
                      <xsl:with-param name="text" select="text"/>
                    </xsl:call-template>
    </p>

 
 
    <xsl:template name="prewrap">
     <xsl:param name="text" select="."/>
     <xsl:variable name="spaceIndex" select="string-length(substring-before($text, '  '))"/>
     <xsl:variable name="tabIndex" select="string-length(substring-before($text, '&#x09;'))"/>
     <xsl:variable name="lineFeedIndex" select="string-length(substring-before($text, '&#xA;'))"/>
     <xsl:choose>
       <xsl:when test="$spaceIndex = 0 and $tabIndex = 0 and $lineFeedIndex = 0"><!-- no special characters left -->
           <xsl:value-of select="$text"/>
       </xsl:when>
       <xsl:when test="$spaceIndex > $tabIndex and $lineFeedIndex > $tabIndex"><!-- tab -->
         <xsl:value-of select="substring-before($text, '&#x09;')"/>
         <xsl:text disable-output-escaping="yes">&amp;nbsp;</xsl:text>
         <xsl:text disable-output-escaping="yes">&amp;nbsp;</xsl:text>
         <xsl:text disable-output-escaping="yes">&amp;nbsp;</xsl:text>
         <xsl:text disable-output-escaping="yes">&amp;nbsp;</xsl:text>
         <xsl:call-template name="prewrap">
           <xsl:with-param name="text" select="substring-after($text,'&#x09;')"/>
         </xsl:call-template>
       </xsl:when>
       <xsl:when test="$spaceIndex > $lineFeedIndex and $tabIndex > $lineFeedIndex"><!-- line feed -->
         <xsl:value-of select="substring-before($text, '&#xA;')"/>
         <br/>
         <xsl:call-template name="prewrap">
           <xsl:with-param name="text" select="substring-after($text,'&#xA;')"/>
         </xsl:call-template>
       </xsl:when>
       <xsl:when test="$lineFeedIndex > $spaceIndex and $tabIndex > $spaceIndex"><!-- two spaces -->
         <xsl:value-of select="substring-before($text, '  ')"/>
         <xsl:text disable-output-escaping="yes">&amp;nbsp;</xsl:text>
         <xsl:text disable-output-escaping="yes">&amp;nbsp;</xsl:text>
         <xsl:call-template name="prewrap">
           <xsl:with-param name="text" select="substring-after($text,'  ')"/>
         </xsl:call-template>
       </xsl:when>
       <xsl:otherwise><!-- should never happen -->
           <xsl:value-of select="$text"/>
       </xsl:otherwise>
     </xsl:choose>
    </xsl:template>

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Ethical programming

It should be noted that no ethically-trained software engineer would ever consent to write a DestroyBaghdad procedure. Basic professional ethics would instead require him to write a DestroyCity procedure, to which Baghdad could be given as a parameter.

-- Nathaniel Borenstein

(Passed on by Reid Nimz.)