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diff --git a/src/documentation/content/xdocs/DnI/overview.xml b/src/documentation/content/xdocs/DnI/overview.xml new file mode 100644 index 000000000..aff1bc6c3 --- /dev/null +++ b/src/documentation/content/xdocs/DnI/overview.xml @@ -0,0 +1,152 @@ +<?xml version="1.0" encoding="utf-8"?> + +<!-- + * Copyright 2004 The Apache Software Foundation. + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + --> + +<!-- $Id$ --> + +<!-- +<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" + "docbookx.dtd"> + --> + + <chapter> + + <title>Overview</title> + + <para>A FOP process has three stages:<orderedlist> + <listitem> + <simpara> building the FO tree,</simpara> + </listitem> + <listitem> + <simpara>building the Area tree,</simpara> + <orderedlist numeration="loweralpha"> + <listitem> + <simpara>The getNextBreakPoss call tree</simpara> + </listitem> + <listitem> + <simpara>The addAreas call tree</simpara> + </listitem> + <listitem> + <simpara>Finishing the page</simpara> + </listitem> + </orderedlist> + </listitem> + <listitem> + <simpara>rendering the pages.</simpara> + </listitem> + </orderedlist></para> + +<para>These stages are preceded by two other stages:<itemizedlist> + <listitem> + <simpara>0. <emphasis>preparation:</emphasis> the objects for +the FOP process are constructed; this phase may be done by FOP (apps +package), or by the calling application;</simpara> + </listitem> + <listitem> + <simpara>X. <emphasis>parsing:</emphasis> this phase is done +by a SAX parser; FOP's own preparation stage uses a JAXP +SAXParserFactory to call an available SAX parser.</simpara> + </listitem> + </itemizedlist></para> + + <para><emphasis>Stage 0.</emphasis> The preparation stage occurs +before the other stages. When it is completed it starts the parsing +stage by calling the parser's <literal>parse</literal> method.</para> + + <para>The parsing stage and stages 1, 2, 3 run concurrently. Each stage +calls into the following stage at appropriate points in its +process. It is feasible that stages 2 and 3 will run in separate +threads.</para> + + <para><emphasis>Stage X.</emphasis> The parser now takes control. +It parses the FO document or walks over the DOM tree. When it +encounters XML events such as the start or end of the document, the +start or end of an XML element, or character data, it makes a call +back into the FO tree builder.</para> + + <para><emphasis>Stage 1.</emphasis> The FO tree builder now takes +control to create or finish the FO node for which the XML event was +fired. When it is done, it returns control to the parser.</para> + + <para>The end events of a few XML elements invoke further actions +of the FO tree builder. When a page-sequence FO node is finished, the +FO tree builder notifies its tree listeners (of which there usually is +only one, the Area tree builder) of this event. Each listener in turn +takes control to process the page sequence.</para> + + <para><emphasis>Stage 2.</emphasis> The Area tree builder (which +is the tree listener) now takes control to lay out the page sequence +and construct the Area tree for it. This stage is divided in three +substages.</para> + + <para><emphasis>Stage 2a.</emphasis> The (pseudo)tree of possible +break points is created. Each node in the FO tree creates a Layout +Manager of the appropriate type. The resulting tree of Layout Managers +is recursed. Each Layout Manager asks each of its child Layout +Managers in turn to return a possible break point, until all child +Layout Managers are finished. This process is started by the Page +Layout Manager, which is tied to the page-sequence FO node that was +just completed in stage 1. Each time when its current child Layout +Manager returns a possible break point, a complete (pseudo)tree of +possible break points for a page has been collected. The next +substage takes control.</para> + + <para><emphasis>Stage 2b.</emphasis> Now the area tree is +created. The (pseudo)tree of possible break points and their Layout +Managers is recursed. Each possible break point may create an area. It +then calls the possible break points of the child LM that fall in this +area, to create and return their area, and adds those areas to its own +area. This process is started by the Page Layout Manager after the +previous substage has finished. When its possible break point returns +its area, the area tree for the flow of the page is complete.</para> + + <para><emphasis>Stage 2c.</emphasis> The Page Layout Manager adds +the static areas and hands the page to the Area tree builder, which +adds it to the root area. The Area tree builder now inspects the set +of complete pages, and fills in forward references to the page just +finished. Pages which are now complete including the forward +references contained in them, are handed over to the renderer, which +now takes control. When the renderer returns control, the Page Layout +Manager starts again in stage 2a to lay out the next page in the page +sequence.</para> + + <para>When all pages of this page sequence are done, this stage +finishes, and the Area tree builder returns control to the FO tree +builder.</para> + + <para><emphasis>Stage 3.</emphasis> The renderer now takes control +to render the finished pages. When it is done with those pages, it +returns control to the Area tree builder.</para> + + <para>This process model is FOP's default process model. It is +completely configurable, through the objects constructed in the +preparation stage. Stage 1 is configured by the content handler that +is registered with the parser. Stage 2 is configured by the listeners +that are registered with the FO tree builder. The layout process in +stage 2 is also configured by the layout strategy that is registered +with the Area tree builder. [It might be more appropriate to say that +stage 2 is controlled by the tree control object. The actual Area tree +builder is assigned by the layout strategy.] Stage 3 is configured by +the selected renderer or output format.</para> + + </chapter> + +<!-- Local Variables: --> +<!-- current-language-environment: UTF-8 --> +<!-- coding: utf-8 --> +<!-- default-input-method: TeX --> +<!-- End: --> |