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.

[miu, 2016/11/21 21:07:03]

FWICT, most of this code is moved from IntersectionObservation.cpp, and is not
new code. Can you adjust your git similarity setting and re-upload so we can see
what actually has changed? (`git cl upload --similarity=20` might do the trick,
but you can test this with `git diff -M20% --stat origin/master`)

[xjz, 2016/11/21 23:58:42]

Done. Most of the codes are originally from InterSectionObservation.cpp and
IntersectionObserver.cpp. 

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "core/dom/IntersectionGeometry.h"
+
+#include "core/dom/Element.h"
+#include "core/dom/ElementRareData.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 {
+
+namespace {
+
+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;
+}
+
+static 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) {
+  FloatQuad mappedQuad = document.layoutView()->ancestorToLocalQuad(
+      &layoutObject, FloatQuad(FloatRect(rect)),
+      UseTransforms | ApplyContainerFlip | TraverseDocumentBoundaries);
+  rect = LayoutRect(mappedQuad.boundingBox());
+}
+
+static 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_root && m_target);
+  DCHECK(rootMargin.isEmpty() || rootMargin.size() == 4);
+}
+
+IntersectionGeometry::~IntersectionGeometry() {}
+
+Element* IntersectionGeometry::root() const {
+  if (!m_root->isDocumentNode())
+    return toElement(m_root);
+  return nullptr;
+}
+
+LayoutObject* IntersectionGeometry::getRootLayoutObject() const {
+  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(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(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(m_rootRect, rootLayoutObject, targetDocument);
+  } else {
+    mapRectDownToDocument(m_rootRect, toLayoutBoxModelObject(rootLayoutObject),
+                          targetDocument);
+  }
+
+  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.
+  if (!m_target->isConnected())
+    return;
+  Element* rootElement = root();
+  if (rootElement && !rootElement->isConnected())
+    return;
+
+  LayoutObject* rootLayoutObject = getRootLayoutObject();
+  if (!rootLayoutObject || !rootLayoutObject->isBoxModelObject())
+    return;
+  // TODO(szager): Support SVG
+  LayoutObject* targetLayoutObject = m_target->layoutObject();
+  if (!targetLayoutObject)
+    return;
+  if (!targetLayoutObject->isBoxModelObject() && !targetLayoutObject->isText())
+    return;
+  if (!isContainingBlockChainDescendant(targetLayoutObject, rootLayoutObject))
+    return;
+
+  initializeGeometry();
+
+  clipToRoot();
+
+  mapTargetRectToTargetFrameCoordinates();
+
+  if (m_doesIntersect)
+    mapRootRectToTargetFrameCoordinates();
+  else
+    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();
+}
+
+DEFINE_TRACE(IntersectionGeometry) {
+  visitor->trace(m_root);
+  visitor->trace(m_target);
+}
+
+}  // namespace blink