Intersection Observer first draft

Source/core/layout/LayoutView.cpp

Index: Source/core/layout/LayoutView.cpp
diff --git a/Source/core/layout/LayoutView.cpp b/Source/core/layout/LayoutView.cpp
index 6d382e74a7b20b63b47724a53c4b8287df0b300c..fd4835706135395a6ef99b3e9817c5f903b67289 100644
--- a/Source/core/layout/LayoutView.cpp
+++ b/Source/core/layout/LayoutView.cpp
@@ -23,6 +23,7 @@
 
 #include "core/dom/Document.h"
 #include "core/dom/Element.h"
+#include "core/dom/IntersectionObserver.h"
 #include "core/editing/FrameSelection.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Settings.h"
@@ -1012,4 +1013,36 @@ void LayoutView::willBeDestroyed()
     m_compositor.clear();
 }
 
+void LayoutView::addIntersectionObserverTarget(LayoutObject* obj)
+{
+    m_intersectionObserverTargets.add(obj, IntRect());
+}
+
+void LayoutView::removeIntersectionObserverTarget(LayoutObject* obj)
+{
+    m_intersectionObserverTargets.remove(obj);
+}
+
+void LayoutView::computeIntersectionObservations(const FloatRect& viewport)
+{
+    for (auto& obj : m_intersectionObserverTargets) {
+        LayoutObject* layoutObect = obj.key;

[ojan, 2015/09/21 03:49:09]

Typo: layoutObect

[MikeB, 2015/09/24 19:04:04]

Done.

+        Node* node = layoutObect->node();
+        if (!node || !node->isElementNode())
+            continue;
+        FloatRect bounds = layoutObect->absoluteBoundingBoxFloatRect();

[ojan, 2015/09/21 03:49:09]

I don't think this handles clipping from ancestor scrollers, does it? Vollick,
what's the right way to get an elements bounding box intersected with all its
ancestor clips? At the moment, the spec just says overflow clips, but we can
consider changing it to include clip-path, etc if that makes more sense.

+        bounds.intersect(viewport);
+        const FloatRect& oldBounds = obj.value;
+        if (oldBounds == bounds)
+            continue;
+        obj.value = bounds;
+        Element* element = toElement(node);
+        Vector<FloatRect> quads;
+        quads.append(bounds);
+        for (auto& observer : element->intersectionObservers()) {
+            observer->enqueueIntersectionObserverEntry(IntersectionObserverEntry::create(0, quads, viewport, element));
+        }
+    }
+}
+
 } // namespace blink