Implement elementsFromPoint

Source/core/dom/TreeScope.cpp

 /*
  * Copyright (C) 2011 Google Inc. All Rights Reserved.
  * Copyright (C) 2012 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 223 matching lines @@
         return 0;
     if (!m_imageMapsByName)
         return 0;
     size_t hashPos = url.find('#');
     String name = hashPos == kNotFound ? url : url.substring(hashPos + 1);
     if (rootNode().document().isHTMLDocument())
         return toHTMLMapElement(m_imageMapsByName->getElementByLowercasedMapName(AtomicString(name.lower()), this));
     return toHTMLMapElement(m_imageMapsByName->getElementByMapName(AtomicString(name), this));
 }
 
-HitTestResult hitTestInDocument(const Document* document, int x, int y)
+HitTestResult hitTestInDocument(const Document* document, int x, int y, HitTestRequest request)
 {
     LocalFrame* frame = document->frame();
 
     if (!frame)
         return HitTestResult();
     FrameView* frameView = frame->view();
     if (!frameView)
         return HitTestResult();
 
     float scaleFactor = frame->pageZoomFactor();
     IntPoint point = roundedIntPoint(FloatPoint(x * scaleFactor  + frameView->scrollX(), y * scaleFactor + frameView->scrollY()));
 
     if (!frameView->visibleContentRect().contains(point))
         return HitTestResult();
 
-    HitTestRequest request(HitTestRequest::ReadOnly | HitTestRequest::Active);
     HitTestResult result(point);
     document->renderView()->hitTest(request, result);
     return result;
 }
 
 Element* TreeScope::elementFromPoint(int x, int y) const
 {
-    HitTestResult result = hitTestInDocument(&rootNode().document(), x, y);
+    HitTestRequest request(HitTestRequest::ReadOnly | HitTestRequest::Active);
+    HitTestResult result = hitTestInDocument(&rootNode().document(), x, y, request);
     Node* node = result.innerNode();
     if (!node || node->isDocumentNode())
         return 0;
     if (node->isPseudoElement() || node->isTextNode())
         node = node->parentOrShadowHostNode();
     ASSERT(!node || node->isElementNode() || node->isShadowRoot());
     node = ancestorInThisScope(node);
     if (!node || !node->isElementNode())
         return 0;
     return toElement(node);
 }
 
+Vector<Element*> TreeScope::elementsFromPoint(int x, int y) const
+{
+    Vector<Element*> elements;
+
+    HitTestRequest request(HitTestRequest::ReadOnly | HitTestRequest::Active | HitTestRequest::ListBased | HitTestRequest::Penetrating);
+    HitTestResult result = hitTestInDocument(&rootNode().document(), x, y, request);
+
+    Node* lastNode = nullptr;
+    for (const auto rectBasedNode : result.listBasedTestResult()) {
+        Node* node = rectBasedNode.get();
+        if (!node || !node->isElementNode() || node->isDocumentNode())
+            continue;
+
+        if (node->isPseudoElement() || node->isTextNode())
+            node = node->parentOrShadowHostNode();
+        node = ancestorInThisScope(node);
+
+        // Prune duplicate entries. A pseduo ::before content above its parent
+        // node should only result in a single entry.

[Rick Byers, 2015/02/04 10:34:03]

are duplicate notes guaranteed to be adjacent, or should we really be using a
set to track all the nodes we've seen?

[pdr., 2015/02/17 04:10:13]

This is a good question. Because result.listBasedTestResult() above is a
ListHashSet, we'll only have unique nodes in the hit test list. Because some of
the nodes are pseudo or text, we can end up with duplicate entries. For example:

listBasedTestResult: [NodeA, NodeAText, NodeB, NodeAPseudo]

When iterating through this list we end up converting the text and pseudo nodes
to their parent, so effectively the list becomes:

[NodeA, NodeA, NodeB, NodeA]

To match the spec we really do want to have NodeA in the list before and after
NodeB, but we don't want to have NodeA listed twice in a row. The above
algorithm prunes the adjacent NodeA's so we get:

[NodeA, NodeB, NodeA]

This matches IE as well.

+        if (node == lastNode)
+            continue;
+
+        if (node && node->isElementNode()) {
+            elements.append(toElement(node));
+            lastNode = node;
+        }
+    }
+    return elements;
+}
+
 void TreeScope::addLabel(const AtomicString& forAttributeValue, HTMLLabelElement* element)
 {
     ASSERT(m_labelsByForAttribute);
     m_labelsByForAttribute->add(forAttributeValue, element);
 }
 
 void TreeScope::removeLabel(const AtomicString& forAttributeValue, HTMLLabelElement* element)
 {
     ASSERT(m_labelsByForAttribute);
     m_labelsByForAttribute->remove(forAttributeValue, element);
@@ skipping 229 matching lines @@
     visitor->trace(m_parentTreeScope);
     visitor->trace(m_idTargetObserverRegistry);
     visitor->trace(m_selection);
     visitor->trace(m_elementsById);
     visitor->trace(m_imageMapsByName);
     visitor->trace(m_labelsByForAttribute);
     visitor->trace(m_scopedStyleResolver);
 }
 
 } // namespace blink