Triggered by Victor's comments on the Session/Document division, I have been thinking about layout issues in a general way, focussed on my feeling that the processing of the Flow Objects needs to be driven by the Area tree processing; i.e. that the FO processing needs to be pulled by the demands of area layout. I have three diagrams illustrating the preliminary ideas. Because of size constraints associated with mailers, I will post these in three messages.
The first, attached concerns Document level. In terms of alt.design's pull parser, Document will be responsible for setting up the SAX parser and the FoXmlEvents buffer as separate threads. It pulls through and processes the layout-master-set and declarations subtrees, creating Declarations and LayoutMasterSet objects. One of the methods of the LayoutMasterSet is pageFactory(), however named, for providing a new Page object meeting particular constraints.
When these are done, the DocumentLayout process (which may or may not be a separate object) starts a loop comprising getPageSequence and layout PageSequence methods. GetPageSequence interrogates the FoXmlEvents buffer for new page-sequences.
LayoutPageSequence is illustrated in the following message.
Peter -- Peter B. West http://www.powerup.com.au/~pbwest/resume.html
<<inline: DocumentLevel.png>>
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