filter out invisible elements

src/com/dom_distiller/client/FilteringDomVisitor.java

Index: src/com/dom_distiller/client/FilteringDomVisitor.java
diff --git a/src/com/dom_distiller/client/FilteringDomVisitor.java b/src/com/dom_distiller/client/FilteringDomVisitor.java
new file mode 100644
index 0000000000000000000000000000000000000000..8a753a9574580cfe7ff6e13f9d1bf65d0931d9d6
--- /dev/null
+++ b/src/com/dom_distiller/client/FilteringDomVisitor.java
@@ -0,0 +1,60 @@
+// 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.dom.client.Element;
+import com.google.gwt.dom.client.Node;
+import com.google.gwt.dom.client.Style;
+
+import java.util.logging.Logger;
+
+/**
+ * Filters out elements that are to be ignored from the DOM tree, and passes other nodes and
+ * elements on to the actual DOM visitor for processing.
+ */
+public class FilteringDomVisitor implements DomWalker.Visitor {
+    // To log debug information about the filtering of processed elements, set this flag to true.
+    private static final boolean DEBUG = false;
+
+    private static Logger logger = Logger.getLogger("FilteringDomParser");
+    private final DomWalker.Visitor domVisitor;
+
+    FilteringDomVisitor(DomWalker.Visitor v) {
+        domVisitor = v;
+    }
+
+    @Override
+    public boolean visit(Node n) {
+        if (n.getNodeType() == Node.ELEMENT_NODE) {
+            // Skip invisible elements.
+            Element e = Element.as(n);
+            boolean visible = true;
+            Style style = null;
+            if (e.hasAttribute("hidden")) {
+                visible = false;
+            } else {
+                style = DomUtil.getComputedStyle(e);
+                visible = !(style.getDisplay().equals("none") ||
+                            style.getVisibility().equals("hidden"));
+            }
+            logDbgInfo(e, visible, style);
+            if (!visible) return false;
+        }
+        return domVisitor.visit(n);
+    }
+
+    @Override
+    public void exit(Node n) {
+        domVisitor.exit(n);
+    }
+
+    private void logDbgInfo(Element e, boolean visible, Style style) {
+        if (!DEBUG) return;
+        LogUtil.logToConsole((visible ? "KEEP " : "SKIP ") + e.getTagName() + ": id=" + e.getId() +
+                ", hiddenAttr=" + (e.hasAttribute("hidden") ? "yes" : "no") +
+                (style == null ? "" :
+                        (", dsp=" + style.getDisplay() + ", vis=" + style.getVisibility())));
+    }
+}