IntersectionObserver: second cut.

third_party/WebKit/Source/core/dom/Element.cpp

Index: third_party/WebKit/Source/core/dom/Element.cpp
diff --git a/third_party/WebKit/Source/core/dom/Element.cpp b/third_party/WebKit/Source/core/dom/Element.cpp
index 2351061beffa6fe31b4f88515be7642791eec300..a8274c114e7751aa8995061b300bb852cfe09435 100644
--- a/third_party/WebKit/Source/core/dom/Element.cpp
+++ b/third_party/WebKit/Source/core/dom/Element.cpp
@@ -59,6 +59,7 @@
 #include "core/dom/ExceptionCode.h"
 #include "core/dom/FirstLetterPseudoElement.h"
 #include "core/dom/Fullscreen.h"
+#include "core/dom/IntersectionObserver.h"
 #include "core/dom/LayoutTreeBuilder.h"
 #include "core/dom/MutationObserverInterestGroup.h"
 #include "core/dom/MutationRecord.h"
@@ -105,6 +106,8 @@
 #include "core/html/HTMLTemplateElement.h"
 #include "core/html/parser/HTMLParserIdioms.h"
 #include "core/inspector/InspectorInstrumentation.h"
+#include "core/layout/LayoutInline.h"
+#include "core/layout/LayoutPart.h"
 #include "core/layout/LayoutTextFragment.h"
 #include "core/layout/LayoutView.h"
 #include "core/loader/DocumentLoader.h"
@@ -170,6 +173,8 @@ Element::~Element()
 {
     ASSERT(needsAttach());
 
+    disconnectIntersectionObservations();
+
 #if !ENABLE(OILPAN)
     if (hasRareData()) {
         elementRareData()->clearShadow();
@@ -1449,8 +1454,14 @@ Node::InsertionNotificationRequest Element::insertedInto(ContainerNode* insertio
     if (!insertionPoint->isInTreeScope())
         return InsertionDone;
 
-    if (hasRareData())
-        elementRareData()->clearClassListValueForQuirksMode();
+    if (hasRareData()) {
+        ElementRareData* rareData = elementRareData();
+        rareData->clearClassListValueForQuirksMode();
+        if (rareData->hasIntersectionObservation()) {
+            for (auto& observation: rareData->intersectionObservations())
+                observation->setActive(observation->observer()->isDescendantOfRoot(this));
+        }
+    }
 
     if (isUpgradedCustomElement() && inDocument())
         CustomElement::didAttach(this, document());
@@ -1528,6 +1539,8 @@ void Element::removedFrom(ContainerNode* insertionPoint)
 
         if (ElementAnimations* elementAnimations = data->elementAnimations())
             elementAnimations->cssAnimations().cancel();
+
+        data->deactivateAllIntersectionObservations();
     }
 }
 
@@ -3569,6 +3582,79 @@ bool Element::supportsStyleSharing() const
     return true;
 }
 
+WeakPtr<Element> Element::createWeakPtr()
+{
+    return ensureElementRareData().createWeakPtr(this);
+}
+
+void Element::addIntersectionObservation(IntersectionObservation& observation)
+{
+    ensureElementRareData().intersectionObservations().add(&observation);
+}
+
+void Element::removeIntersectionObservation(IntersectionObservation& observation)
+{
+    if (!hasRareData() || !elementRareData()->hasIntersectionObservation())
+        return;
+    elementRareData()->intersectionObservations().remove(&observation);
+}
+
+void Element::disconnectIntersectionObservations()
+{
+    if (!hasRareData() || !elementRareData()->hasIntersectionObservation())
+        return;
+    HeapVector<Member<IntersectionObservation>> toRemove;
+    for (auto& observation: elementRareData()->intersectionObservations())
+        toRemove.append(observation);
+    for (auto& observation: toRemove) {
+        if (observation->observer()->root() == this)
+            observation->observer()->disconnect();
+        else
+            observation->disconnect();
+    }
+}
+
+bool Element::computeIntersection(Element* root, LayoutRect& targetRect, LayoutRect& rootRect, LayoutRect& intersectionRect)
+{
+    // TODO: support zero-size targetRect
+    intersectionRect = targetRect = toLayoutBoxModelObject(layoutObject())->visualOverflowRect();
+
+    if (root) {
+        ASSERT(root->isInTreeScope());
+        ASSERT(isDescendantOf(root));
+        // TODO: Support SVG
+        if (!root->layoutObject()->isBoxModelObject())
+            return false;
+        rootRect = toLayoutBoxModelObject(root->layoutObject())->visualOverflowRect();
+        layoutObject()->mapRectToPaintInvalidationBacking(toLayoutBoxModelObject(root->layoutObject()), intersectionRect, nullptr);
+
+        // Convert rects to frame coordinates.
+        targetRect.moveBy(LayoutPoint(layoutObject()->localToAbsolute()));
+        LayoutPoint rootOffset = LayoutPoint(root->layoutObject()->localToAbsolute());
+        intersectionRect.moveBy(rootOffset);
+        rootRect.moveBy(rootOffset);
+    } else {
+        Element* target = this;
+        LocalFrame* frame = document().frame();
+        while (target) {
+            targetRect.moveBy(LayoutPoint(target->layoutObject()->localToAbsolute()));
+            Document& document = target->document();
+            LayoutView* layoutView = document.layoutView();
+            ASSERT(layoutView);
+            // TODO: mapRectToPaintInvalidationBacking probably doesn't do exactly the clipping we want,
+            // and it doesn't support rootMargin at all.
+            target->layoutObject()->mapRectToPaintInvalidationBacking(layoutView, intersectionRect, nullptr);
+            frame = document.frame();
+            ASSERT(frame);
+            target = toElement(frame->ownerLayoutObject()->node());
+        }
+        rootRect = LayoutRect(frame->view()->scrollableArea()->visibleContentRect());
+        intersectionRect = intersection(intersectionRect, rootRect);
+    }
+
+    return true;
+}
+
 DEFINE_TRACE(Element)
 {
 #if ENABLE(OILPAN)