FOP-3176: Remove unused PDFStructElem

fop-core/src/main/java/org/apache/fop/pdf/PDFDocument.java

@@ -30,6 +30,7 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.Date;
 import java.util.HashMap;
+import java.util.Iterator;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
@@ -389,7 +390,6 @@ public class PDFDocument {
      * Adds the given element to the structure tree.
      */
     public void registerStructureElement(PDFStructElem structElem) {
-        assignObjectNumber(structElem);
         structureTreeElements.add(structElem);
     }
 
@@ -479,6 +479,9 @@ public class PDFDocument {
      * @param obj {@link PDFObject} to add
      */
     public void addObject(PDFObject obj) {
+        if (obj instanceof PDFStructElem) {
+            return;
+        }
         if (obj == null) {
             throw new NullPointerException("obj must not be null");
         }
@@ -1149,6 +1152,14 @@ public class PDFDocument {
                 ? new CompressedTrailerOutputHelper()
                 : new UncompressedTrailerOutputHelper();
         if (structureTreeElements != null) {
+            Iterator<PDFStructElem> structElemIterator = structureTreeElements.iterator();
+            while (structElemIterator.hasNext()) {
+                PDFStructElem structElem = structElemIterator.next();
+                if (!structElem.hasObjectNumber()) {
+                    structElemIterator.remove();
+                    structElem.parentElement.kids.remove(structElem);
+                }
+            }
             trailerOutputHelper.outputStructureTreeElements(stream);
         }
         streamIndirectObjects(trailerObjects, stream);

fop-core/src/main/java/org/apache/fop/pdf/PDFStructElem.java

@@ -51,6 +51,7 @@ public class PDFStructElem extends StructureHierarchyMember
     protected List<PDFObject> kids;
 
     private List<PDFDictionary> attributes;
+    private PDFObject parent;
 
     /**
      * Creates PDFStructElem with no entries.
@@ -68,13 +69,19 @@ public class PDFStructElem extends StructureHierarchyMember
         this(parent);
         this.structureType = structureType;
         put("S", structureType.getName());
-        setParent(parent);
+        if (parent != null) {
+            put("P", null);
+        }
     }
 
     private PDFStructElem(PDFObject parent) {
         if (parent instanceof PDFStructElem) {
             parentElement = (PDFStructElem) parent;
         }
+        this.parent = parent;
+        if (parent != null) {
+            setDocument(parent.getDocument());
+        }
     }
 
     /**
@@ -102,11 +109,22 @@ public class PDFStructElem extends StructureHierarchyMember
     @Override
     public void addKid(PDFObject kid) {
         if (kids == null) {
+            assignObjectNumber();
             kids = new ArrayList<PDFObject>();
         }
         kids.add(kid);
     }
 
+    private void assignObjectNumber() {
+        if (parentElement != null) {
+            parentElement.assignObjectNumber();
+        }
+        if (getDocument() != null && !hasObjectNumber()) {
+            getDocument().assignObjectNumber(this);
+        }
+        setParent(parent);
+    }
+
     /**
      * Sets the given mcid as the kid of this structure element. This element
      * will then add itself to its parent structure element if it has not

fop-core/src/main/java/org/apache/fop/pdf/PDFStructTreeRoot.java

@@ -19,10 +19,14 @@
 
 package org.apache.fop.pdf;
 
+import java.io.Serializable;
+
 /**
  * Class representing a PDF /StructTreeRoot dictionary.
  */
-public class PDFStructTreeRoot extends StructureHierarchyMember {
+public class PDFStructTreeRoot extends StructureHierarchyMember implements Serializable {
+
+    private static final long serialVersionUID = -4102820991473046724L;
 
     /**
      * Creates a new /StructTreeRoot dictionary.

fop-core/src/test/java/org/apache/fop/accessibility/fo/PDFUAWarningTestCase.java

@@ -52,9 +52,12 @@ public class PDFUAWarningTestCase {
     public void nestedTableWarningTestCase() throws IOException {
         ByteArrayOutputStream bos = new ByteArrayOutputStream();
         PDFStructElem emptyElem = new PDFStructElem();
+        emptyElem.setDocument(pdfFactory.getDocument());
         PDFStructElem block  = PDFStructureTreeBuilder.createStructureElement("block", emptyElem,
                 new AttributesImpl(), pdfFactory, null);
-        PDFStructureTreeBuilder.createStructureElement("table", block, new AttributesImpl(), pdfFactory, null);
+        PDFStructElem table =
+                PDFStructureTreeBuilder.createStructureElement("table", block, new AttributesImpl(), pdfFactory, null);
+        pdfFactory.getDocument().assignObjectNumber(table);
         block.output(bos);
         Assert.assertEquals("Div", block.getStructureType().toString());
     }

fop-core/src/test/java/org/apache/fop/pdf/PDFStructureTreeTestCase.java

@@ -0,0 +1,94 @@
+/*
+ * 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.
+ */
+
+// $Id$
+package org.apache.fop.pdf;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.File;
+import java.io.IOException;
+
+import javax.xml.transform.Result;
+import javax.xml.transform.Source;
+import javax.xml.transform.Transformer;
+import javax.xml.transform.TransformerException;
+import javax.xml.transform.TransformerFactory;
+import javax.xml.transform.sax.SAXResult;
+import javax.xml.transform.stream.StreamSource;
+
+import org.junit.Assert;
+import org.junit.Test;
+import org.xml.sax.SAXException;
+
+import org.apache.fop.apps.FOUserAgent;
+import org.apache.fop.apps.Fop;
+import org.apache.fop.apps.FopFactory;
+import org.apache.fop.apps.MimeConstants;
+
+public class PDFStructureTreeTestCase {
+    @Test
+    public void testRemoveUnusedStructs() throws Exception {
+        String fo = "<fo:root xmlns:fo=\"http://www.w3.org/1999/XSL/Format\">\n"
+                + "  <fo:layout-master-set>\n"
+                + "    <fo:simple-page-master page-width=\"8.5in\" page-height=\"11in\" master-name=\"First\">\n"
+                + "      <fo:region-body region-name=\"Body\"/>\n"
+                + "      <fo:region-before extent=\"1in\" region-name=\"Header\"/>\n"
+                + "    </fo:simple-page-master>\n"
+                + "    <fo:simple-page-master page-width=\"8.5in\" page-height=\"11in\" master-name=\"Rest\">\n"
+                + "      <fo:region-body region-name=\"Body\"/>\n"
+                + "      <fo:region-before extent=\"1in\" region-name=\"Header Rest\"/>\n"
+                + "    </fo:simple-page-master>\n"
+                + "    <fo:page-sequence-master master-name=\"PSM\">\n"
+                + "      <fo:repeatable-page-master-alternatives>\n"
+                + "        <fo:conditional-page-master-reference page-position=\"first\" master-reference=\"First\"/>\n"
+                + "        <fo:conditional-page-master-reference page-position=\"rest\" master-reference=\"Rest\"/>\n"
+                + "      </fo:repeatable-page-master-alternatives>\n"
+                + "    </fo:page-sequence-master>\n"
+                + "  </fo:layout-master-set>\n"
+                + "  <fo:page-sequence master-reference=\"PSM\">\n"
+                + "    <fo:static-content flow-name=\"Header\">\n"
+                + "      <fo:block><fo:external-graphic src=\"test/resources/fop/image/logo.jpg\" /></fo:block>\n"
+                + "    </fo:static-content>\n"
+                + "    <fo:static-content flow-name=\"Header Rest\">\n"
+                + "      <fo:block><fo:external-graphic src=\"test/resources/fop/svg/logo.jpg\" /></fo:block>\n"
+                + "    </fo:static-content>\n"
+                + "    <fo:flow flow-name=\"Body\">\n"
+                + "      <fo:block>test</fo:block>\n"
+                + "    </fo:flow>\n"
+                + "  </fo:page-sequence>\n"
+                + "</fo:root>";
+        ByteArrayOutputStream bos = foToOutput(fo);
+        String pdf = bos.toString();
+        Assert.assertEquals(pdf.split("/S /Figure").length, 2);
+        Assert.assertEquals(pdf.split("/S /").length, 11);
+    }
+
+    private ByteArrayOutputStream foToOutput(String fo)
+            throws IOException, SAXException, TransformerException {
+        FopFactory fopFactory = FopFactory.newInstance(new File(".").toURI());
+        FOUserAgent userAgent = fopFactory.newFOUserAgent();
+        userAgent.setAccessibility(true);
+        ByteArrayOutputStream bos = new ByteArrayOutputStream();
+        Fop fop = fopFactory.newFop(MimeConstants.MIME_PDF, userAgent, bos);
+        Transformer transformer = TransformerFactory.newInstance().newTransformer();
+        Source src = new StreamSource(new ByteArrayInputStream(fo.getBytes("UTF-8")));
+        Result res = new SAXResult(fop.getDefaultHandler());
+        transformer.transform(src, res);
+        return bos;
+    }
+}