#79 - Refactor accessibility support out to helper class.

openhtmltopdf-pdfbox/src/main/java/com/openhtmltopdf/pdfboxout/PdfBoxAccessibilityHelper.java

@@ -0,0 +1,247 @@
+package com.openhtmltopdf.pdfboxout;
+
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.Deque;
+import java.util.HashMap;
+import java.util.List;
+import org.apache.pdfbox.cos.COSArray;
+import org.apache.pdfbox.cos.COSDictionary;
+import org.apache.pdfbox.cos.COSInteger;
+import org.apache.pdfbox.cos.COSName;
+import org.apache.pdfbox.pdmodel.PDPage;
+import org.apache.pdfbox.pdmodel.common.PDNumberTreeNode;
+import org.apache.pdfbox.pdmodel.documentinterchange.logicalstructure.PDStructureElement;
+import org.apache.pdfbox.pdmodel.documentinterchange.logicalstructure.PDStructureTreeRoot;
+import org.apache.pdfbox.pdmodel.documentinterchange.markedcontent.PDMarkedContent;
+import org.apache.pdfbox.pdmodel.documentinterchange.taggedpdf.PDArtifactMarkedContent;
+import org.apache.pdfbox.pdmodel.documentinterchange.taggedpdf.StandardStructureTypes;
+import org.w3c.dom.Element;
+
+import com.openhtmltopdf.extend.StructureType;
+import com.openhtmltopdf.render.Box;
+
+public class PdfBoxAccessibilityHelper {
+
+    private final Deque<StructureItem> _structureStack = new ArrayDeque<>();
+    private final List<StructureItem> _pageContentItems = new ArrayList<>();
+    private final COSArray _numTree = new COSArray();
+    private final PdfBoxFastOutputDevice _od;
+
+    private int _nextMcid = 0;
+    private int _nextPageIndex;
+
+    private PDPage _page;
+    private PdfContentStreamAdapter _cs;
+
+    public PdfBoxAccessibilityHelper(PdfBoxFastOutputDevice od) {
+        this._od = od;
+    }
+
+    public void finishPdfUa() {
+        COSDictionary dict = new COSDictionary();
+        dict.setItem(COSName.NUMS, _numTree);
+
+        PDNumberTreeNode numberTreeNode = new PDNumberTreeNode(dict, dict.getClass());
+        _od.getWriter().getDocumentCatalog().getStructureTreeRoot().setParentTreeNextKey(_numTree.size());
+        _od.getWriter().getDocumentCatalog().getStructureTreeRoot().setParentTree(numberTreeNode);
+    }
+
+    private static class StructureItem {
+        private final StructureType type;
+        private final Box box;
+
+        private COSDictionary dict;
+        private PDStructureElement elem;
+        private int mcid = -1;
+
+        private StructureItem parent;
+        private List<StructureItem> children = new ArrayList<>();
+
+        private StructureItem(StructureType type, Box box) {
+            this.type = type;
+            this.box = box;
+        }
+
+        @Override
+        public String toString() {
+            return box.toString();
+        }
+    }
+
+    private void finishStructure(StructureItem item) {
+        for (StructureItem child : item.children) {
+            switch (child.type) {
+            case LAYER:
+            case FLOAT:
+            case BLOCK:
+            case INLINE: {
+                System.out.println("Append strcuture: " + child.toString());
+
+                child.elem = new PDStructureElement(COSName.P.getName(), item.elem);
+                child.elem.setPage(_page);
+                child.elem.setLanguage("EN-US"); // TODO: Only set lang if different from parent.
+                child.elem.setParent(item.elem);
+
+                item.elem.appendKid(child.elem);
+
+                finishStructure(child);
+            }
+            break;
+            case TEXT: {
+                System.out.println("Append text: " + child);
+                item.elem.appendKid(new PDMarkedContent(COSName.P, child.dict));
+                _numTree.add(item.elem.getCOSObject());
+            }
+            break;
+            case BACKGROUND: {
+                item.elem.appendKid(new PDArtifactMarkedContent(child.dict));
+                _numTree.add(item.elem.getCOSObject());
+            }
+            break;
+            }
+        }
+    }
+
+    private Element getBoxElement(Box box) {
+        if (box.getElement() != null) {
+            return box.getElement();
+        } else if (box.getParent() != null) {
+            return getBoxElement(box.getParent());
+        } else {
+            return null;
+        }
+    }
+
+    private COSDictionary createMarkedContentDictionary() {
+        COSDictionary dict = new COSDictionary();
+        dict.setInt(COSName.MCID, _nextMcid);
+        _nextMcid++;
+        return dict;
+    }
+
+    public void startStructure(StructureType type, Box box) {
+            System.out.println("Start: " + type);
+            switch (type) {
+            case LAYER:
+            case FLOAT:
+            case BLOCK:
+            case INLINE: {
+                //if (!_structureMap.containsKey(box)) {
+                    StructureItem item = new StructureItem(type, box);
+                    StructureItem parent = _structureStack.getLast();
+
+                    parent.children.add(item);
+                    _structureStack.addLast(item);
+                //}
+                break;
+            }
+            case BACKGROUND: {
+                // TODO: Only create if actually has a background or border.
+                StructureItem current = new StructureItem(type, box);
+                StructureItem parent = _structureStack.getLast();
+
+                current.mcid = _nextMcid;
+                current.dict = createMarkedContentDictionary();
+                current.parent = parent;
+
+                _pageContentItems.add(current);
+                parent.children.add(current);
+
+                _cs.beginMarkedContent(COSName.ARTIFACT, current.dict);
+                break;
+            }
+            case TEXT: {
+                StructureItem current = new StructureItem(type, box);
+                StructureItem parent = _structureStack.getLast();
+
+                current.mcid = _nextMcid;
+                current.dict = createMarkedContentDictionary();
+                current.parent = parent;
+
+                _pageContentItems.add(current);
+                parent.children.add(current);
+
+                _cs.beginMarkedContent(COSName.getPDFName(StandardStructureTypes.SPAN), current.dict);
+                break;
+            }
+            default:
+                break;
+            }
+    }
+
+    public void endStructure(StructureType type, Box box) {
+
+            System.out.println("END: " + type);
+            switch (type) {
+            case LAYER:
+            case FLOAT:
+            case BLOCK:
+            case INLINE: {
+                _structureStack.removeLast();
+            }
+            break;
+            case BACKGROUND:
+            case TEXT: {
+                // TODO: Only background if actually has a background or border.
+                _cs.endMarkedContent();
+            }
+            default:
+                break;
+            }
+    }
+
+    public void startPage(PDPage page, PdfContentStreamAdapter cs) {
+        this._page = page;
+        this._cs = cs;
+
+        StructureItem item = new StructureItem(null, null);
+        _structureStack.clear();
+        _structureStack.addLast(item);
+    }
+
+    public void endPage() {
+        StructureItem page = _structureStack.removeLast();
+        PDStructureElement item = new PDStructureElement(StandardStructureTypes.DOCUMENT, null);
+        item.setPage(_page);
+
+        PDStructureTreeRoot root = _od.getWriter().getDocumentCatalog().getStructureTreeRoot();
+        if (root == null) {
+            root = new PDStructureTreeRoot();
+            HashMap<String, String> roleMap = new HashMap<>();
+            roleMap.put("Annotation", "Span");
+            roleMap.put("Artifact", "P");
+            roleMap.put("Bibliography", "BibEntry");
+            roleMap.put("Chart", "Figure");
+            roleMap.put("Diagram", "Figure");
+            roleMap.put("DropCap", "Figure");
+            roleMap.put("EndNote", "Note");
+            roleMap.put("FootNote", "Note");
+            roleMap.put("InlineShape", "Figure");
+            roleMap.put("Outline", "Span");
+            roleMap.put("Strikeout", "Span");
+            roleMap.put("Subscript", "Span");
+            roleMap.put("Superscript", "Span");
+            roleMap.put("Underline", "Span");
+            root.setRoleMap(roleMap);
+            _od.getWriter().getDocumentCatalog().setStructureTreeRoot(root);
+        }
+        root.appendKid(item);
+        page.elem = item;
+
+        finishStructure(page);
+
+        _page.getCOSObject().setItem(COSName.STRUCT_PARENTS, COSInteger.get(_nextPageIndex));
+
+        for (int i = 0; i < _pageContentItems.size(); i++) {
+            System.out.println("NUM TREE: " + i + ", " + _pageContentItems.get(i) + ", " + _pageContentItems.get(i).parent);
+            _numTree.add(COSInteger.get(i));
+            _numTree.add(_pageContentItems.get(i).parent.elem);
+        }
+
+        _nextPageIndex += _pageContentItems.size();
+        _pageContentItems.clear();
+        _nextMcid = 0;
+    }
+
+}