org.apache.fop.render.pdf.PDFLogicalStructureHandler Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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: PDFLogicalStructureHandler.java 1873293 2020-01-29 10:15:14Z ssteiner $ */
package org.apache.fop.render.pdf;
import org.apache.fop.pdf.PDFArray;
import org.apache.fop.pdf.PDFDictionary;
import org.apache.fop.pdf.PDFDocument;
import org.apache.fop.pdf.PDFLink;
import org.apache.fop.pdf.PDFName;
import org.apache.fop.pdf.PDFPage;
import org.apache.fop.pdf.PDFParentTree;
import org.apache.fop.pdf.PDFStructElem;
/**
* Handles the creation of the logical structure in the PDF document.
*/
public class PDFLogicalStructureHandler {
private static final PDFName MCR = new PDFName("MCR");
private static final PDFName OBJR = new PDFName("OBJR");
private static final MarkedContentInfo ARTIFACT = new MarkedContentInfo(null, -1, null);
private final PDFDocument pdfDoc;
private final PDFParentTree parentTree = new PDFParentTree();
private int parentTreeKey;
private PDFPage currentPage;
/**
* The array of references, from marked-content sequences in the current
* page, to their parent structure elements. This will be a value in the
* structure parent tree, whose corresponding key will be the page's
* StructParents entry.
*/
private PDFArray pageParentTreeArray;
/**
* Class providing the necessary information for bracketing content
* associated to a structure element as a marked-content sequence.
*/
static final class MarkedContentInfo {
/**
* A value that can be used for the tag operand of a marked-content
* operator. This is the structure type of the corresponding structure
* element.
*/
final String tag;
/**
* The value for the MCID entry of the marked-content sequence's property list.
*/
final int mcid;
private final PDFStructElem parent;
private MarkedContentInfo(String tag, int mcid, PDFStructElem parent) {
this.tag = tag;
this.mcid = mcid;
this.parent = parent;
}
}
/**
* Creates a new instance for handling the logical structure of the given document.
*
* @param pdfDoc a document
*/
PDFLogicalStructureHandler(PDFDocument pdfDoc) {
this.pdfDoc = pdfDoc;
}
public PDFArray getPageParentTree() {
return this.pageParentTreeArray;
}
public PDFParentTree getParentTree() {
return parentTree;
}
public int getNextParentTreeKey() {
return parentTreeKey++;
}
/**
* Receive notification of the beginning of a new page.
*
* @param page the page that will be rendered in PDF
*/
void startPage(PDFPage page) {
currentPage = page;
currentPage.setStructParents(getNextParentTreeKey());
pageParentTreeArray = new PDFArray();
}
/**
* Receive notification of the end of the current page.
*/
void endPage() {
// TODO
// Values in a number tree must be indirect references to the PDF
// objects associated to the keys. To enforce that the array is
// registered to the PDF document. Unfortunately that can't be done
// earlier since a call to PDFContentGenerator.flushPDFDoc can be made
// before the array is complete, which would result in only part of it
// being output to the PDF.
// This should really be handled by PDFNumsArray
pdfDoc.registerObject(pageParentTreeArray);
parentTree.addToNums(currentPage.getStructParents(), pageParentTreeArray);
}
private MarkedContentInfo addToParentTree(PDFStructElem structureTreeElement) {
PDFStructElem parent = structureTreeElement;
while (parent instanceof PDFStructElem.Placeholder) {
parent = parent.getParentStructElem();
}
pageParentTreeArray.add(parent);
String type = parent.getStructureType().getName().toString();
int mcid = pageParentTreeArray.length() - 1;
return new MarkedContentInfo(type, mcid, structureTreeElement);
}
/**
* Adds a content item corresponding to text into the structure tree, if
* there is a structure element associated to it.
*
* @param structElem the parent structure element of the piece of text
* @return the necessary information for bracketing the content as a
* marked-content sequence. If there is no element in the structure tree
* associated to that content, returns an instance whose
* {@link MarkedContentInfo#tag} value is null. The content
* must then be treated as an artifact.
*/
MarkedContentInfo addTextContentItem(PDFStructElem structElem) {
if (structElem == null) {
return ARTIFACT;
} else {
MarkedContentInfo mci = addToParentTree(structElem);
PDFDictionary contentItem = new PDFDictionary();
contentItem.put("Type", MCR);
contentItem.put("Pg", this.currentPage);
contentItem.put("MCID", mci.mcid);
mci.parent.addKid(contentItem);
return mci;
}
}
/**
* Adds a content item corresponding to an image into the structure tree, if
* there is a structure element associated to it.
*
* @param structElem the parent structure element of the image
* @return the necessary information for bracketing the content as a
* marked-content sequence. If there is no element in the structure tree
* associated to that image, returns an instance whose
* {@link MarkedContentInfo#tag} value is null. The image must
* then be treated as an artifact.
*/
MarkedContentInfo addImageContentItem(PDFStructElem structElem) {
if (structElem == null) {
return ARTIFACT;
} else {
MarkedContentInfo mci = addToParentTree(structElem);
PDFDictionary contentItem = new PDFDictionary();
contentItem.put("Type", MCR);
contentItem.put("Pg", this.currentPage);
contentItem.put("MCID", mci.mcid);
mci.parent.addKid(contentItem);
return mci;
}
}
/**
* Adds a content item corresponding to the given link into the structure
* tree.
*
* @param link a link
* @param structureTreeElement its parent structure element
*/
void addLinkContentItem(PDFLink link, PDFStructElem structureTreeElement) {
int structParent = getNextParentTreeKey();
link.setStructParent(structParent);
PDFDictionary contentItem = new PDFDictionary();
contentItem.put("Type", OBJR);
contentItem.put("Pg", this.currentPage);
contentItem.put("Obj", link);
parentTree.addToNums(structParent, structureTreeElement);
structureTreeElement.addKid(contentItem);
}
}