filter out invisible elements

src/com/dom_distiller/client/DomToSaxVisitor.java

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package com.dom_distiller.client;
+
+import com.google.gwt.core.client.JsArray;
+import com.google.gwt.dom.client.Element;
+import com.google.gwt.dom.client.Node;
+import com.google.gwt.dom.client.NodeList;
+import com.google.gwt.dom.client.Text;
+
+import org.xml.sax.Attributes;
+import org.xml.sax.AttributesImpl;
+import org.xml.sax.ContentHandler;
+import org.xml.sax.SAXException;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.logging.Logger;
+
+/**
+ * Used to generate sax events from the DOM tree.
+ */
+public class DomToSaxVisitor implements DomWalker.Visitor {
+    private static Logger logger = Logger.getLogger("DomToSaxParser");
+    private static final String sHtmlNamespace = "http://www.w3.org/1999/xhtml";
+    private final ContentHandler handler;
+    private List<Node> textNodes;
+
+    DomToSaxVisitor(ContentHandler h) {
+        handler = h;
+        textNodes = new ArrayList<Node>();
+    }
+
+    /*
+     * @Return A list of the text nodes (in order).
+     */
+    public final List<Node> getTextNodes() { return textNodes; }
+
+    @Override
+    public boolean visit(Node n) {
+        try {
+            switch (n.getNodeType()) {
+                case Node.TEXT_NODE:
+                    textNodes.add(n);
+                    String text = Text.as(n).getData();
+                    handler.characters(text.toCharArray(), 0, text.length());
+                    return false;
+                case Node.ELEMENT_NODE:
+                    Element e = Element.as(n);
+                    Attributes attrs = getSaxAttributes(e);
+                    handler.startElement(sHtmlNamespace, e.getTagName(), e.getTagName(), attrs);
+                    return true;
+                case Node.DOCUMENT_NODE:  // Don't recurse into sub-documents.
+                default:  // This case is for comment nodes.
+                    return false;
+            }
+        } catch (SAXException e) {
+            return false;
+        }
+    }
+
+    @Override
+    public void exit(Node n) {
+        Element e = Element.as(n);
+        try {
+            handler.endElement(sHtmlNamespace, e.getTagName(), e.getTagName());
+        } catch (SAXException ex) {
+            // Intentionally ignored.
+        }
+    }
+
+    /**
+     * @Return The element's attribute list converted to org.xml.sax.Attributes.
+     */
+    public static Attributes getSaxAttributes(Element e) {
+        AttributesImpl attrs = new AttributesImpl();
+
+        JsArray<Node> jsAttrs = DomUtil.getAttributes(e);
+        for (int i = 0; i < jsAttrs.length(); ++i) {
+            final Node jsAttr = jsAttrs.get(i);
+            attrs.addAttribute("", jsAttr.getNodeName(), jsAttr.getNodeName(), "CDATA",
+                               jsAttr.getNodeValue());
+        }
+
+        return attrs;
+    }
+}