diff options
Diffstat (limited to 'src/documentation/content/xdocs/DnI/rendering.xml')
| -rw-r--r-- | src/documentation/content/xdocs/DnI/rendering.xml | 90 |
1 files changed, 90 insertions, 0 deletions
diff --git a/src/documentation/content/xdocs/DnI/rendering.xml b/src/documentation/content/xdocs/DnI/rendering.xml new file mode 100644 index 000000000..82f3b429c --- /dev/null +++ b/src/documentation/content/xdocs/DnI/rendering.xml @@ -0,0 +1,90 @@ +<?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>Phase 3: Rendering the pages</title> + + <para>It is the task of the rendering phase to describe the area +tree in the target page description language, so that viewers for that +language can render the pages. Rendering is done page by page. For +each page the rendering system is handed a PageViewport, and it walks +the area subtree below it. For each area it retrieves the traits and +data, and generates the required output.</para> + + <para>The layout of a page is not finished until all forward +references on that page have been resolved. As a consequence pages are +finished out of pagination order. Some renderers support out of +order rendering of pages, +<literal>AbstractRenderer.supportsOutOfOrder()</literal>. If a +renderer does, a finished page is handed over to it +immediately. Otherwise, the layout system keeps finished pages until +all preceding pages are also finished and have been handed over to the +renderer. In principle, the PDF renderer supports out of order +rendering. In current FOP (27 June 2004) this has been disabled +because the support is broken.</para> + + <para>This stack at a deep position, rendering a leader in a block +in a flow in the body region, shows some details of rendering. Note +how the hierarchy of the area tree can be recognized. The lower +frames show how the rendering system is called by the layout system: + +<screen> +main[1] where + [1] org.apache.fop.render.pdf.PDFRenderer.renderLeader (PDFRenderer.java:1,266) + [2] org.apache.fop.render.AbstractRenderer.serveVisitor (AbstractRenderer.java:832) + [3] org.apache.fop.area.inline.Leader.acceptVisitor (Leader.java:118) + [4] org.apache.fop.render.AbstractRenderer.renderLineArea (AbstractRenderer.java:610) + [5] org.apache.fop.render.pdf.PDFRenderer.renderLineArea (PDFRenderer.java:830) + [6] org.apache.fop.render.AbstractRenderer.renderBlocks (AbstractRenderer.java:547) + [7] org.apache.fop.render.AbstractRenderer.renderBlock (AbstractRenderer.java:588) + [8] org.apache.fop.render.pdf.PDFRenderer.renderBlock (PDFRenderer.java:513) + [9] org.apache.fop.render.AbstractRenderer.renderBlocks (AbstractRenderer.java:538) + [10] org.apache.fop.render.AbstractRenderer.renderFlow (AbstractRenderer.java:473) + [11] org.apache.fop.render.AbstractRenderer.renderMainReference (AbstractRenderer.java:456) + [12] org.apache.fop.render.AbstractRenderer.renderBodyRegion (AbstractRenderer.java:392) + [13] org.apache.fop.render.AbstractRenderer.renderRegionViewport (AbstractRenderer.java:338) + [14] org.apache.fop.render.AbstractRenderer.renderPageAreas (AbstractRenderer.java:310) + [15] org.apache.fop.render.pdf.PDFRenderer.renderPage (PDFRenderer.java:471) + [16] org.apache.fop.area.RenderPagesModel.addPage (RenderPagesModel.java:117) + [17] org.apache.fop.area.AreaTree.addPage (AreaTree.java:143) + [18] org.apache.fop.layoutmgr.PageLayoutManager.finishPage (PageLayoutManager.java:532) + [19] org.apache.fop.layoutmgr.PageLayoutManager.doLayout (PageLayoutManager.java:231) +</screen></para> + + <para>Obviously there is a lot to be documented about the rendering +system, and about each renderer separately. Because I do not (yet) +know much about the rendering system, I will have to leave that task +to others. I only add the obvious: Rendering requires precise +programming: spacing and progress calculations, saving and restoring +dimensions, etc. It also requires tracking the state in the output +format.</para> + +</chapter> + +<!-- Local Variables: --> +<!-- current-language-environment: UTF-8 --> +<!-- coding: utf-8 --> +<!-- default-input-method: TeX --> +<!-- End: --> |