Detect change on the intersection of video and viewport.

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

 // Copyright 2016 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.
 
-#include "core/dom/IntersectionObservation.h"
-
+#include "core/dom/IntersectionGeometry.h"
+
+#include "core/dom/Element.h"
 #include "core/dom/ElementRareData.h"
-#include "core/dom/IntersectionObserver.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/layout/LayoutBox.h"
 #include "core/layout/LayoutView.h"
+#include "core/layout/api/LayoutAPIShim.h"
+#include "core/layout/api/LayoutViewItem.h"
 #include "core/paint/PaintLayer.h"
 
 namespace blink {
 
-IntersectionObservation::IntersectionObservation(IntersectionObserver& observer,
-                                                 Element& target,
-                                                 bool shouldReportRootBounds)
-    : m_observer(observer),
-      m_target(&target),
-      m_shouldReportRootBounds(shouldReportRootBounds),
-      m_lastThresholdIndex(0) {}
-
-void IntersectionObservation::applyRootMargin(LayoutRect& rect) const {
-  if (m_shouldReportRootBounds)
-    m_observer->applyRootMargin(rect);
-}
-
-void IntersectionObservation::initializeGeometry(
-    IntersectionGeometry& geometry) const {
-  initializeTargetRect(geometry.targetRect);
-  geometry.intersectionRect = geometry.targetRect;
-  initializeRootRect(geometry.rootRect);
-  geometry.doesIntersect = true;
-}
-
-void IntersectionObservation::initializeTargetRect(LayoutRect& rect) const {
-  DCHECK(m_target);
-  LayoutObject* targetLayoutObject = target()->layoutObject();
-  DCHECK(targetLayoutObject && targetLayoutObject->isBoxModelObject());
-  rect = LayoutRect(
-      toLayoutBoxModelObject(targetLayoutObject)->borderBoundingBox());
-}
-
-void IntersectionObservation::initializeRootRect(LayoutRect& rect) const {
-  LayoutObject* rootLayoutObject = m_observer->rootLayoutObject();
-  if (rootLayoutObject->isLayoutView())
-    rect = LayoutRect(
-        toLayoutView(rootLayoutObject)->frameView()->visibleContentRect());
-  else if (rootLayoutObject->isBox() && rootLayoutObject->hasOverflowClip())
-    rect = LayoutRect(toLayoutBox(rootLayoutObject)->contentBoxRect());
-  else
-    rect = LayoutRect(
-        toLayoutBoxModelObject(rootLayoutObject)->borderBoundingBox());
-  applyRootMargin(rect);
-}
-
-void IntersectionObservation::clipToRoot(IntersectionGeometry& geometry) const {
-  // Map and clip rect into root element coordinates.
-  // TODO(szager): the writing mode flipping needs a test.
-  DCHECK(m_target);
-  LayoutBox* rootLayoutObject = toLayoutBox(m_observer->rootLayoutObject());
-  LayoutObject* targetLayoutObject = target()->layoutObject();
-
-  geometry.doesIntersect = targetLayoutObject->mapToVisualRectInAncestorSpace(
-      rootLayoutObject, geometry.intersectionRect, EdgeInclusive);
-  if (rootLayoutObject->hasOverflowClip())
-    geometry.intersectionRect.move(-rootLayoutObject->scrolledContentOffset());
-
-  if (!geometry.doesIntersect)
-    return;
-  LayoutRect rootClipRect(geometry.rootRect);
-  rootLayoutObject->flipForWritingMode(rootClipRect);
-  geometry.doesIntersect &=
-      geometry.intersectionRect.inclusiveIntersect(rootClipRect);
-}
-
-static void mapRectUpToDocument(LayoutRect& rect,
-                                const LayoutObject& layoutObject,
-                                const Document& document) {
+namespace {
+
+bool isContainingBlockChainDescendant(LayoutObject* descendant,
+                                      LayoutObject* ancestor) {
+  LocalFrame* ancestorFrame = ancestor->document().frame();
+  LocalFrame* descendantFrame = descendant->document().frame();
+
+  if (ancestor->isLayoutView())
+    return descendantFrame && descendantFrame->tree().top() == ancestorFrame;
+
+  if (ancestorFrame != descendantFrame)
+    return false;
+
+  while (descendant && descendant != ancestor)
+    descendant = descendant->containingBlock();
+  return descendant;
+}
+
+void mapRectUpToDocument(LayoutRect& rect,
+                         const LayoutObject& layoutObject,
+                         const Document& document) {
   FloatQuad mappedQuad = layoutObject.localToAbsoluteQuad(
       FloatQuad(FloatRect(rect)), UseTransforms | ApplyContainerFlip);
   rect = LayoutRect(mappedQuad.boundingBox());
 }
 
-static void mapRectDownToDocument(LayoutRect& rect,
-                                  LayoutBoxModelObject& layoutObject,
-                                  const Document& document) {
+void mapRectDownToDocument(LayoutRect& rect,
+                           LayoutBoxModelObject& layoutObject,
+                           const Document& document) {
   FloatQuad mappedQuad = document.layoutView()->ancestorToLocalQuad(
       &layoutObject, FloatQuad(FloatRect(rect)),
       UseTransforms | ApplyContainerFlip | TraverseDocumentBoundaries);
   rect = LayoutRect(mappedQuad.boundingBox());
 }
 
-void IntersectionObservation::mapTargetRectToTargetFrameCoordinates(
-    LayoutRect& rect) const {
-  LayoutObject& targetLayoutObject = *target()->layoutObject();
-  Document& targetDocument = target()->document();
+LayoutUnit computeMargin(const Length& length, LayoutUnit referenceLength) {
+  if (length.type() == Percent) {
+    return LayoutUnit(
+        static_cast<int>(referenceLength.toFloat() * length.percent() / 100.0));
+  }
+  DCHECK_EQ(length.type(), Fixed);
+  return LayoutUnit(length.intValue());
+}
+
+}  // namespace
+
+IntersectionGeometry::IntersectionGeometry(Node* root,
+                                           Element* target,
+                                           const Vector<Length>& rootMargin,
+                                           bool shouldReportRootBounds)
+    : m_root(root),
+      m_target(target),
+      m_rootMargin(rootMargin),
+      m_shouldReportRootBounds(shouldReportRootBounds) {
+  DCHECK(m_target);
+  DCHECK(rootMargin.isEmpty() || rootMargin.size() == 4);
+}
+
+IntersectionGeometry::~IntersectionGeometry() {}
+
+Element* IntersectionGeometry::root() const {
+  if (m_root && !m_root->isDocumentNode())
+    return toElement(m_root);
+  return nullptr;
+}
+
+LayoutObject* IntersectionGeometry::getRootLayoutObject() const {
+  DCHECK(m_root);
+  if (m_root->isDocumentNode()) {
+    return LayoutAPIShim::layoutObjectFrom(
+        toDocument(m_root)->layoutViewItem());
+  }
+  return toElement(m_root)->layoutObject();
+}
+
+void IntersectionGeometry::initializeGeometry() {
+  initializeTargetRect();
+  m_intersectionRect = m_targetRect;
+  initializeRootRect();
+  m_doesIntersect = true;
+}
+
+void IntersectionGeometry::initializeTargetRect() {
+  LayoutObject* targetLayoutObject = m_target->layoutObject();
+  DCHECK(targetLayoutObject && targetLayoutObject->isBoxModelObject());
+  m_targetRect = LayoutRect(
+      toLayoutBoxModelObject(targetLayoutObject)->borderBoundingBox());
+}
+
+void IntersectionGeometry::initializeRootRect() {
+  LayoutObject* rootLayoutObject = getRootLayoutObject();
+  if (rootLayoutObject->isLayoutView()) {
+    m_rootRect = LayoutRect(
+        toLayoutView(rootLayoutObject)->frameView()->visibleContentRect());
+  } else if (rootLayoutObject->isBox() && rootLayoutObject->hasOverflowClip()) {
+    m_rootRect = LayoutRect(toLayoutBox(rootLayoutObject)->contentBoxRect());
+  } else {
+    m_rootRect = LayoutRect(
+        toLayoutBoxModelObject(rootLayoutObject)->borderBoundingBox());
+  }
+  applyRootMargin();
+}
+
+void IntersectionGeometry::applyRootMargin() {
+  if (m_rootMargin.isEmpty())
+    return;
+
+  // TODO(szager): Make sure the spec is clear that left/right margins are
+  // resolved against width and not height.
+  LayoutUnit topMargin = computeMargin(m_rootMargin[0], m_rootRect.height());
+  LayoutUnit rightMargin = computeMargin(m_rootMargin[1], m_rootRect.width());
+  LayoutUnit bottomMargin = computeMargin(m_rootMargin[2], m_rootRect.height());
+  LayoutUnit leftMargin = computeMargin(m_rootMargin[3], m_rootRect.width());
+
+  m_rootRect.setX(m_rootRect.x() - leftMargin);
+  m_rootRect.setWidth(m_rootRect.width() + leftMargin + rightMargin);
+  m_rootRect.setY(m_rootRect.y() - topMargin);
+  m_rootRect.setHeight(m_rootRect.height() + topMargin + bottomMargin);
+}
+
+void IntersectionGeometry::clipToRoot() {
+  // Map and clip rect into root element coordinates.
+  // TODO(szager): the writing mode flipping needs a test.
+  LayoutBox* rootLayoutObject = toLayoutBox(getRootLayoutObject());
+  LayoutObject* targetLayoutObject = m_target->layoutObject();
+
+  m_doesIntersect = targetLayoutObject->mapToVisualRectInAncestorSpace(
+      rootLayoutObject, m_intersectionRect, EdgeInclusive);
+  if (rootLayoutObject->hasOverflowClip())
+    m_intersectionRect.move(-rootLayoutObject->scrolledContentOffset());
+
+  if (!m_doesIntersect)
+    return;
+  LayoutRect rootClipRect(m_rootRect);
+  rootLayoutObject->flipForWritingMode(rootClipRect);
+  m_doesIntersect &= m_intersectionRect.inclusiveIntersect(rootClipRect);
+}
+
+void IntersectionGeometry::mapTargetRectToTargetFrameCoordinates() {
+  LayoutObject& targetLayoutObject = *m_target->layoutObject();
+  Document& targetDocument = m_target->document();
   LayoutSize scrollPosition = LayoutSize(targetDocument.view()->scrollOffset());
-  mapRectUpToDocument(rect, targetLayoutObject, targetDocument);
-  rect.move(-scrollPosition);
-}
-
-void IntersectionObservation::mapRootRectToRootFrameCoordinates(
-    LayoutRect& rect) const {
-  LayoutObject& rootLayoutObject = *m_observer->rootLayoutObject();
+  mapRectUpToDocument(m_targetRect, targetLayoutObject, targetDocument);
+  m_targetRect.move(-scrollPosition);
+}
+
+void IntersectionGeometry::mapRootRectToRootFrameCoordinates() {
+  LayoutObject& rootLayoutObject = *getRootLayoutObject();
   Document& rootDocument = rootLayoutObject.document();
   LayoutSize scrollPosition = LayoutSize(rootDocument.view()->scrollOffset());
-  mapRectUpToDocument(rect, rootLayoutObject, rootLayoutObject.document());
-  rect.move(-scrollPosition);
-}
-
-void IntersectionObservation::mapRootRectToTargetFrameCoordinates(
-    LayoutRect& rect) const {
-  LayoutObject& rootLayoutObject = *m_observer->rootLayoutObject();
-  Document& targetDocument = target()->document();
+  mapRectUpToDocument(m_intersectionRect, rootLayoutObject,
+                      rootLayoutObject.document());
+  m_intersectionRect.move(-scrollPosition);
+}
+
+void IntersectionGeometry::mapRootRectToTargetFrameCoordinates() {
+  LayoutObject& rootLayoutObject = *getRootLayoutObject();
+  Document& targetDocument = m_target->document();
   LayoutSize scrollPosition = LayoutSize(targetDocument.view()->scrollOffset());
 
-  if (&targetDocument == &rootLayoutObject.document())
-    mapRectUpToDocument(rect, rootLayoutObject, targetDocument);
-  else
-    mapRectDownToDocument(rect, toLayoutBoxModelObject(rootLayoutObject),
+  if (&targetDocument == &rootLayoutObject.document()) {
+    mapRectUpToDocument(m_rootRect, rootLayoutObject, targetDocument);
+  } else {
+    mapRectDownToDocument(m_rootRect, toLayoutBoxModelObject(rootLayoutObject),
                           targetDocument);
-
-  rect.move(-scrollPosition);
-}
-
-static bool isContainingBlockChainDescendant(LayoutObject* descendant,
-                                             LayoutObject* ancestor) {
-  LocalFrame* ancestorFrame = ancestor->document().frame();
-  LocalFrame* descendantFrame = descendant->document().frame();
-
-  if (ancestor->isLayoutView())
-    return descendantFrame && descendantFrame->tree().top() == ancestorFrame;
-
-  if (ancestorFrame != descendantFrame)
-    return false;
-
-  while (descendant && descendant != ancestor)
-    descendant = descendant->containingBlock();
-  return descendant;
-}
-
-bool IntersectionObservation::computeGeometry(
-    IntersectionGeometry& geometry) const {
+  }
+
+  m_rootRect.move(-scrollPosition);
+}
+
+void IntersectionGeometry::computeGeometry() {
   // In the first few lines here, before initializeGeometry is called, "return
   // true" effectively means "if the previous observed state was that root and
   // target were intersecting, then generate a notification indicating that they
   // are no longer intersecting."  This happens, for example, when root or
   // target is removed from the DOM tree and not reinserted before the next
   // frame is generated, or display:none is set on the root or target.
-  Element* targetElement = target();
-  if (!targetElement)
-    return false;
-  if (!targetElement->isConnected())
-    return true;
-  DCHECK(m_observer);
-  Element* rootElement = m_observer->root();
+  if (!m_target->isConnected())
+    return;
+  Element* rootElement = root();
   if (rootElement && !rootElement->isConnected())
-    return true;
-
-  LayoutObject* rootLayoutObject = m_observer->rootLayoutObject();
+    return;
+
+  LayoutObject* rootLayoutObject = getRootLayoutObject();
   if (!rootLayoutObject || !rootLayoutObject->isBoxModelObject())
-    return true;
+    return;
   // TODO(szager): Support SVG
-  LayoutObject* targetLayoutObject = targetElement->layoutObject();
+  LayoutObject* targetLayoutObject = m_target->layoutObject();
   if (!targetLayoutObject)
-    return true;
+    return;
   if (!targetLayoutObject->isBoxModelObject() && !targetLayoutObject->isText())
-    return true;
+    return;
   if (!isContainingBlockChainDescendant(targetLayoutObject, rootLayoutObject))
-    return true;
-
-  initializeGeometry(geometry);
-
-  clipToRoot(geometry);
-
-  mapTargetRectToTargetFrameCoordinates(geometry.targetRect);
-
-  if (geometry.doesIntersect)
-    mapRootRectToTargetFrameCoordinates(geometry.intersectionRect);
+    return;
+
+  initializeGeometry();
+
+  clipToRoot();
+
+  mapTargetRectToTargetFrameCoordinates();
+
+  if (m_doesIntersect)
+    mapRootRectToTargetFrameCoordinates();
   else
-    geometry.intersectionRect = LayoutRect();
+    m_intersectionRect = LayoutRect();
 
   // Small optimization: if we're not going to report root bounds, don't bother
   // transforming them to the frame.
   if (m_shouldReportRootBounds)
-    mapRootRectToRootFrameCoordinates(geometry.rootRect);
-
-  return true;
-}
-
-void IntersectionObservation::computeIntersectionObservations(
-    DOMHighResTimeStamp timestamp) {
-  IntersectionGeometry geometry;
-  if (!computeGeometry(geometry))
-    return;
-
-  // Some corner cases for threshold index:
-  //   - If target rect is zero area, because it has zero width and/or zero
-  //     height,
-  //     only two states are recognized:
-  //     - 0 means not intersecting.
-  //     - 1 means intersecting.
-  //     No other threshold crossings are possible.
-  //   - Otherwise:
-  //     - If root and target do not intersect, the threshold index is 0.
-  //     - If root and target intersect but the intersection has zero-area
-  //       (i.e., they have a coincident edge or corner), we consider the
-  //       intersection to have "crossed" a zero threshold, but not crossed
-  //       any non-zero threshold.
-  unsigned newThresholdIndex;
-  float newVisibleRatio = 0;
-  if (geometry.targetRect.isEmpty()) {
-    newThresholdIndex = geometry.doesIntersect ? 1 : 0;
-  } else if (!geometry.doesIntersect) {
-    newThresholdIndex = 0;
-  } else {
-    float intersectionArea =
-        geometry.intersectionRect.size().width().toFloat() *
-        geometry.intersectionRect.size().height().toFloat();
-    float targetArea = geometry.targetRect.size().width().toFloat() *
-                       geometry.targetRect.size().height().toFloat();
-    newVisibleRatio = intersectionArea / targetArea;
-    newThresholdIndex = observer().firstThresholdGreaterThan(newVisibleRatio);
-  }
-  if (m_lastThresholdIndex != newThresholdIndex) {
-    IntRect snappedRootBounds = pixelSnappedIntRect(geometry.rootRect);
-    IntRect* rootBoundsPointer =
-        m_shouldReportRootBounds ? &snappedRootBounds : nullptr;
-    IntersectionObserverEntry* newEntry = new IntersectionObserverEntry(
-        timestamp, newVisibleRatio, pixelSnappedIntRect(geometry.targetRect),
-        rootBoundsPointer, pixelSnappedIntRect(geometry.intersectionRect),
-        target());
-    observer().enqueueIntersectionObserverEntry(*newEntry);
-    setLastThresholdIndex(newThresholdIndex);
-  }
-}
-
-void IntersectionObservation::disconnect() {
-  IntersectionObserver* observer = m_observer;
-  clearRootAndRemoveFromTarget();
-  observer->removeObservation(*this);
-}
-
-void IntersectionObservation::clearRootAndRemoveFromTarget() {
-  if (m_target)
-    target()->ensureIntersectionObserverData().removeObservation(observer());
-  m_observer.clear();
-}
-
-DEFINE_TRACE(IntersectionObservation) {
-  visitor->trace(m_observer);
+    mapRootRectToRootFrameCoordinates();
+}
+
+DEFINE_TRACE(IntersectionGeometry) {
+  visitor->trace(m_root);
   visitor->trace(m_target);
 }
 
 }  // namespace blink