7.3 Page Sequence Master Interleave (PSMI)

7.3 Page Sequence Master Interleave (PSMI)

Sometimes it is necessary to change page geometry based on content.

• Consider the need to change the geometry for a lengthy landscaped table.

  • You cannot use a rotated table because the table length is limited by the container.

  • You must switch to a landscape body region so the lengthy table can flow to subsequent pages.

• Consider the need to flow certain figures into double- sized pages.

  • You must selectively choose a geometry with different dimensions.

• The construct may be deep within the structure of the document being processed .

To use XSL-FO, you must package all content for each page geometry into the flow of a page sequence.

• This can involve a difficult and wasteful recursive process

  • finding all information up to the change in geometry,

  • packaging the information into a page sequence,

  • packaging the special constructs into a different page sequence,

  • recursively finding all information up to the next change in geometry.

• This breaks the XSLT model of hierarchical processing.

  • This approach is susceptible to development and maintenance problems.

A two-step process can make this very easy to implement.

• The first step creates the flow with supplemental indications of the need to change geometries.

  • You can come from any depth of processing of the source document.

  • Block-level constructs of a page are the immediate children of the flow.

• The second step repackages flow children in as many sequences as necessary.

  • It recursively checks all flow child constructs for any changes in geometry.

  • It is not necessary to check any depth deeper than the children.

• The resulting document is then processed by a standard XSL-FO engine.

The Page Sequence Master Interleave (PSMI) semantic implements this algorithm.

• The public resource is freely available from Crane Softwrights Ltd.

  • http://www.CraneSoftwrights.com/links/res-dxslfo.htm

• A one-element vocabulary is designed to express the semantic of this two-step intermediate process.

• An XSLT stylesheet implements the semantic for any XSL-FO+PSMI sequence.

Consider the need to flow a landscape table in a portrait page geometry, as shown in Figure 7-6. Here's how this is addressed using the PSMI.

• You could rotate a short table in a block container to present it in landscape orientation.

  • A long table would overflow and not trigger a new page in pagination.

• Using PSMI, you could flow the landscape table into an interleaved page geometry where the body region of that geometry is landscape.

• The PSMI stylesheet reads the XSL-FO+PSMI instance and produces a pure XSL-FO instance where three page sequences are created instead of one.

• A long table in the landscape body region will correctly trigger new pages in pagination.

Figure 7-6. Page Sequence Master Interleave (PSMI)

An example of flow implementing the change in page geometry is shown in Example 7-5.

Example 7-5 PSMI constructs in example

 Line 01   <simple-page-master master-name="frame-portraitbody" ...>      02     <region-body region-name="frame-body" .../>      03     <region-before region-name="frame-before" .../>      04     <region-after region-name="frame-after" .../>      05   </simple-page-master>      06   <simple-page-master master-name="frame-landbody" ...>      07     <region-body region-name="frame-body"       08                  reference-orientation="90deg" .../>      09     <region-before region-name="frame-before" .../>      10     <region-after region-name="frame-after" .../>      11   </simple-page-master>      12 ...      13 <page-sequence master-reference="frame-portraitbody">      14   <flow flow-name="frame-body">      15     <block>Portrait information</block>      16     ...      17     <block>Next is landscaped</block>      18     <psmi:page-sequence master-reference="frame-landbody"      19       xmlns:psmi="http://www.CraneSoftwrights.com/resources/psmi">      20       <flow flow-name="frame-body">      21         <table>      22           <table-body>      23             <table-row>      24               <table-cell border="solid">      25                 <block>This is a test</block>      26                 <block>This is a test</block>      27                 ...      28                 <block>This is a test</block>      29                 <block>This is a test</block>      30               </table-cell>      31             </table-row>      32           </table-body>      33         </table>      34       </flow>      35     </psmi:page-sequence>      36     <block>Back to portrait</block>      37     ...      38   </flow>