8.2 A Quick Example


To give you a good overview of the whole process, let us take a look at a short, quick example. This humble XML document will be the source:

 <mydoc>   <title>Hello world!</title>   <message>I am <emphasis>so</emphasis> clever.</message> </mydoc> 

The first step in using XSL-FO is to write an XSLT stylesheet that will generate a formatting object tree. Example 8-1 is a very simple (for XSL-FO) stylesheet. There are five templates in all. The first creates a page master, an archetype of real pages that will be created as text is poured in, setting up the geometry of content regions . The second template associates a flow object with the page master. The flow is like a baggage handler, throwing suitcases into a compact space that fits the geometry set up in the page master. The rest of the templates create blocks and inlines to be stacked inside the flow.

Example 8-1. An XSLT stylesheet to turn mydoc into a formatting object tree
 <?xml version="1.0"?> <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"                 xmlns:fo="http://www.w3.org/1999/XSL/Format"                 version="1.0" > <xsl:output method="xml"/> <!-- The root node, where we set up a page with a single      region. <layout-master-set> may contain many page masters, but      here we have defined only one. <simple-page-master> sets up a      basic page type with width and height dimensions, margins, and a      name to reference later with a flow. --> <xsl:template match="/">   <fo:root>     <fo:layout-master-set>       <fo:simple-page-master              master-name="the-only-page-type"             page-height="4in" page-width="4in"             margin-top="0.5in" margin-bottom="0.5in"             margin-left="0.5in" margin-right="0.5in">         <fo:region-body/>       </fo:simple-page-master>     </fo:layout-master-set>     <xsl:apply-templates/>   </fo:root> </xsl:template> <!-- The first block element, where we insert the document flow.      <page-sequence> sets up an instance of the page type we defined      above. <flow> contains all the stackable block objects, shaping      them so they fit in the page region we defined. The flow contains      a block that defines font name, size, text alignment, and      surrounds its content in a 0.25 inch buffer of padding. --> <xsl:template match="mydoc">   <fo:page-sequence master-reference="the-only-page-type">     <fo:flow flow-name="xsl-region-body">       <fo:block         font-family="helvetica, sans-serif"         font-size="24pt"         text-align="center"         padding="0.25in"      >         <xsl:apply-templates/>       </fo:block>     </fo:flow>   </fo:page-sequence> </xsl:template> <!-- The second block element, a title, is bold, 10 point type, and       inserts 1 em of space below itself. --> <xsl:template match="title">   <fo:block     font-weight="bold"     font-size="10pt"     space-after="1em"  >     <xsl:apply-templates/>   </fo:block> </xsl:template> <!-- The last block element, a message body element. The padding is      set to 0.25 inches and the border is visible.      --> <xsl:template match="message">   <fo:block     padding="0.25in"     border="solid 1pt black"  >     <xsl:apply-templates/>   </fo:block> </xsl:template> <!-- The inline emphasis element is set to be italic. --> <xsl:template match="emphasis">   <fo:inline     font-style="italic"  >     <xsl:apply-templates/>   </fo:inline> </xsl:template> </xsl:stylesheet> 

Many of the elements created by this stylesheet have attributes that define properties you may recognize from CSS. Names like font-style and border should be familiar to you already. If you remember the display-type property from CSS, you will understand what the block and inline elements do. They are containers that shape their contents, either to fit a rectangular area in a flow, or to follow the inline progression of lines in a block.

Run the transformation on the source document and you will generate this formatting object tree:

 <?xml version="1.0"?> <fo:root xmlns:fo="http://www.w3.org/1999/XSL/Format">   <fo:layout-master-set>     <fo:simple-page-master master-name="the-only-page-type"       page-height="3in" page-width="4in" margin-top="0.5in"       margin-bottom="0.5in" margin-left="0.5in" margin-right="0.5in">     <fo:region-body/>     </fo:simple-page-master>   </fo:layout-master-set>   <fo:page-sequence master-reference="the-only-page-type">     <fo:flow flow-name="xsl-region-body">       <fo:block font-family="helvetica, sans-serif" font-size="24pt"         text-align="center" padding="0.25in">        <fo:block font-weight="bold" font-size="10pt"         space-after="1em">Hello world!</fo:block>       <fo:block padding="0.25in" border="solid 1pt black">I am         <fo:inline font-style="italic">so</fo:inline> clever.</fo:block>       </fo:block>     </fo:flow>   </fo:page-sequence> </fo:root> 

Import this into an XSL formatter and it will generate output shown in Figure 8-1.

Figure 8-2. The message formatted
figs/lx2_0802.gif


Learning XML
Learning XML, Second Edition
ISBN: 0596004206
EAN: 2147483647
Year: 2003
Pages: 139
Authors: Erik T. Ray

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