layout/base/nsDisplayList.cpp
author Timothy Nikkel <tnikkel@gmail.com>
Sun, 04 May 2014 23:18:18 -0500
changeset 192244 d7abd8044d615646ff5ef097a5a268c895505720
parent 192208 c0f1a5d2645b480b42d2f759dee15f6f054678b0
permissions -rw-r--r--
Bug 1000423 - Properly convert from appunits/layout device pixels to layer pixels for composition bounds calculation. r=botond, a=lsblakk To get layer pixels (doesn't matter which layer, they are all the same to layout because there is no async transform) you need to multiply by the cumulative resolution. The fact that our units system says that multiplying by the parent resolution will work is a problem with our units system.

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: set ts=2 sw=2 et tw=78:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

/*
 * structures that represent things to be painted (ordered in z-order),
 * used during painting and hit testing
 */

#include "mozilla/dom/TabChild.h"
#include "mozilla/layers/PLayerTransaction.h"

#include "nsDisplayList.h"

#include "nsCSSRendering.h"
#include "nsRenderingContext.h"
#include "nsISelectionController.h"
#include "nsIPresShell.h"
#include "nsRegion.h"
#include "nsStyleStructInlines.h"
#include "nsStyleTransformMatrix.h"
#include "gfxMatrix.h"
#include "nsSVGIntegrationUtils.h"
#include "nsLayoutUtils.h"
#include "nsIScrollableFrame.h"
#include "nsIFrameInlines.h"
#include "nsThemeConstants.h"
#include "LayerTreeInvalidation.h"

#include "imgIContainer.h"
#include "BasicLayers.h"
#include "nsBoxFrame.h"
#include "nsViewportFrame.h"
#include "nsSubDocumentFrame.h"
#include "nsSVGEffects.h"
#include "nsSVGElement.h"
#include "nsSVGClipPathFrame.h"
#include "GeckoProfiler.h"
#include "nsAnimationManager.h"
#include "nsTransitionManager.h"
#include "nsViewManager.h"
#include "ImageLayers.h"
#include "ImageContainer.h"
#include "nsCanvasFrame.h"
#include "StickyScrollContainer.h"
#include "mozilla/LookAndFeel.h"
#include "mozilla/Preferences.h"
#include "ActiveLayerTracker.h"
#include "nsContentUtils.h"
#include "nsPrintfCString.h"
#include "UnitTransforms.h"

#include <stdint.h>
#include <algorithm>

using namespace mozilla;
using namespace mozilla::css;
using namespace mozilla::layers;
using namespace mozilla::dom;
typedef FrameMetrics::ViewID ViewID;

static inline nsIFrame*
GetTransformRootFrame(nsIFrame* aFrame)
{
  return nsLayoutUtils::GetTransformRootFrame(aFrame);
}

static void AddTransformFunctions(nsCSSValueList* aList,
                                  nsStyleContext* aContext,
                                  nsPresContext* aPresContext,
                                  nsRect& aBounds,
                                  float aAppUnitsPerPixel,
                                  InfallibleTArray<TransformFunction>& aFunctions)
{
  if (aList->mValue.GetUnit() == eCSSUnit_None) {
    return;
  }

  for (const nsCSSValueList* curr = aList; curr; curr = curr->mNext) {
    const nsCSSValue& currElem = curr->mValue;
    NS_ASSERTION(currElem.GetUnit() == eCSSUnit_Function,
                 "Stream should consist solely of functions!");
    nsCSSValue::Array* array = currElem.GetArrayValue();
    bool canStoreInRuleTree = true;
    switch (nsStyleTransformMatrix::TransformFunctionOf(array)) {
      case eCSSKeyword_rotatex:
      {
        double theta = array->Item(1).GetAngleValueInRadians();
        aFunctions.AppendElement(RotationX(theta));
        break;
      }
      case eCSSKeyword_rotatey:
      {
        double theta = array->Item(1).GetAngleValueInRadians();
        aFunctions.AppendElement(RotationY(theta));
        break;
      }
      case eCSSKeyword_rotatez:
      {
        double theta = array->Item(1).GetAngleValueInRadians();
        aFunctions.AppendElement(RotationZ(theta));
        break;
      }
      case eCSSKeyword_rotate:
      {
        double theta = array->Item(1).GetAngleValueInRadians();
        aFunctions.AppendElement(Rotation(theta));
        break;
      }
      case eCSSKeyword_rotate3d:
      {
        double x = array->Item(1).GetFloatValue();
        double y = array->Item(2).GetFloatValue();
        double z = array->Item(3).GetFloatValue();
        double theta = array->Item(4).GetAngleValueInRadians();
        aFunctions.AppendElement(Rotation3D(x, y, z, theta));
        break;
      }
      case eCSSKeyword_scalex:
      {
        double x = array->Item(1).GetFloatValue();
        aFunctions.AppendElement(Scale(x, 1, 1));
        break;
      }
      case eCSSKeyword_scaley:
      {
        double y = array->Item(1).GetFloatValue();
        aFunctions.AppendElement(Scale(1, y, 1));
        break;
      }
      case eCSSKeyword_scalez:
      {
        double z = array->Item(1).GetFloatValue();
        aFunctions.AppendElement(Scale(1, 1, z));
        break;
      }
      case eCSSKeyword_scale:
      {
        double x = array->Item(1).GetFloatValue();
        // scale(x) is shorthand for scale(x, x);
        double y = array->Count() == 2 ? x : array->Item(2).GetFloatValue();
        aFunctions.AppendElement(Scale(x, y, 1));
        break;
      }
      case eCSSKeyword_scale3d:
      {
        double x = array->Item(1).GetFloatValue();
        double y = array->Item(2).GetFloatValue();
        double z = array->Item(3).GetFloatValue();
        aFunctions.AppendElement(Scale(x, y, z));
        break;
      }
      case eCSSKeyword_translatex:
      {
        double x = nsStyleTransformMatrix::ProcessTranslatePart(
          array->Item(1), aContext, aPresContext, canStoreInRuleTree,
          aBounds.Width(), aAppUnitsPerPixel);
        aFunctions.AppendElement(Translation(x, 0, 0));
        break;
      }
      case eCSSKeyword_translatey:
      {
        double y = nsStyleTransformMatrix::ProcessTranslatePart(
          array->Item(1), aContext, aPresContext, canStoreInRuleTree,
          aBounds.Height(), aAppUnitsPerPixel);
        aFunctions.AppendElement(Translation(0, y, 0));
        break;
      }
      case eCSSKeyword_translatez:
      {
        double z = nsStyleTransformMatrix::ProcessTranslatePart(
          array->Item(1), aContext, aPresContext, canStoreInRuleTree,
          0, aAppUnitsPerPixel);
        aFunctions.AppendElement(Translation(0, 0, z));
        break;
      }
      case eCSSKeyword_translate:
      {
        double x = nsStyleTransformMatrix::ProcessTranslatePart(
          array->Item(1), aContext, aPresContext, canStoreInRuleTree,
          aBounds.Width(), aAppUnitsPerPixel);
        // translate(x) is shorthand for translate(x, 0)
        double y = 0;
        if (array->Count() == 3) {
           y = nsStyleTransformMatrix::ProcessTranslatePart(
            array->Item(2), aContext, aPresContext, canStoreInRuleTree,
            aBounds.Height(), aAppUnitsPerPixel);
        }
        aFunctions.AppendElement(Translation(x, y, 0));
        break;
      }
      case eCSSKeyword_translate3d:
      {
        double x = nsStyleTransformMatrix::ProcessTranslatePart(
          array->Item(1), aContext, aPresContext, canStoreInRuleTree,
          aBounds.Width(), aAppUnitsPerPixel);
        double y = nsStyleTransformMatrix::ProcessTranslatePart(
          array->Item(2), aContext, aPresContext, canStoreInRuleTree,
          aBounds.Height(), aAppUnitsPerPixel);
        double z = nsStyleTransformMatrix::ProcessTranslatePart(
          array->Item(3), aContext, aPresContext, canStoreInRuleTree,
          0, aAppUnitsPerPixel);

        aFunctions.AppendElement(Translation(x, y, z));
        break;
      }
      case eCSSKeyword_skewx:
      {
        double x = array->Item(1).GetAngleValueInRadians();
        aFunctions.AppendElement(SkewX(x));
        break;
      }
      case eCSSKeyword_skewy:
      {
        double y = array->Item(1).GetAngleValueInRadians();
        aFunctions.AppendElement(SkewY(y));
        break;
      }
      case eCSSKeyword_skew:
      {
        double x = array->Item(1).GetAngleValueInRadians();
        // skew(x) is shorthand for skew(x, 0)
        double y = 0;
        if (array->Count() == 3) {
          y = array->Item(2).GetAngleValueInRadians();
        }
        aFunctions.AppendElement(Skew(x, y));
        break;
      }
      case eCSSKeyword_matrix:
      {
        gfx::Matrix4x4 matrix;
        matrix._11 = array->Item(1).GetFloatValue();
        matrix._12 = array->Item(2).GetFloatValue();
        matrix._13 = 0;
        matrix._14 = 0;
        matrix._21 = array->Item(3).GetFloatValue();
        matrix._22 = array->Item(4).GetFloatValue();
        matrix._23 = 0;
        matrix._24 = 0;
        matrix._31 = 0;
        matrix._32 = 0;
        matrix._33 = 1;
        matrix._34 = 0;
        matrix._41 = array->Item(5).GetFloatValue();
        matrix._42 = array->Item(6).GetFloatValue();
        matrix._43 = 0;
        matrix._44 = 1;
        aFunctions.AppendElement(TransformMatrix(matrix));
        break;
      }
      case eCSSKeyword_matrix3d:
      {
        gfx::Matrix4x4 matrix;
        matrix._11 = array->Item(1).GetFloatValue();
        matrix._12 = array->Item(2).GetFloatValue();
        matrix._13 = array->Item(3).GetFloatValue();
        matrix._14 = array->Item(4).GetFloatValue();
        matrix._21 = array->Item(5).GetFloatValue();
        matrix._22 = array->Item(6).GetFloatValue();
        matrix._23 = array->Item(7).GetFloatValue();
        matrix._24 = array->Item(8).GetFloatValue();
        matrix._31 = array->Item(9).GetFloatValue();
        matrix._32 = array->Item(10).GetFloatValue();
        matrix._33 = array->Item(11).GetFloatValue();
        matrix._34 = array->Item(12).GetFloatValue();
        matrix._41 = array->Item(13).GetFloatValue();
        matrix._42 = array->Item(14).GetFloatValue();
        matrix._43 = array->Item(15).GetFloatValue();
        matrix._44 = array->Item(16).GetFloatValue();
        aFunctions.AppendElement(TransformMatrix(matrix));
        break;
      }
      case eCSSKeyword_interpolatematrix:
      {
        gfx3DMatrix matrix;
        nsStyleTransformMatrix::ProcessInterpolateMatrix(matrix, array,
                                                         aContext,
                                                         aPresContext,
                                                         canStoreInRuleTree,
                                                         aBounds,
                                                         aAppUnitsPerPixel);
        gfx::Matrix4x4 transform;
        gfx::ToMatrix4x4(matrix, transform);
        aFunctions.AppendElement(TransformMatrix(transform));
        break;
      }
      case eCSSKeyword_perspective:
      {
        aFunctions.AppendElement(Perspective(array->Item(1).GetFloatValue()));
        break;
      }
      default:
        NS_ERROR("Function not handled yet!");
    }
  }
}

static TimingFunction
ToTimingFunction(css::ComputedTimingFunction& aCTF)
{
  if (aCTF.GetType() == nsTimingFunction::Function) {
    const nsSMILKeySpline* spline = aCTF.GetFunction();
    return TimingFunction(CubicBezierFunction(spline->X1(), spline->Y1(),
                                              spline->X2(), spline->Y2()));
  }

  uint32_t type = aCTF.GetType() == nsTimingFunction::StepStart ? 1 : 2;
  return TimingFunction(StepFunction(aCTF.GetSteps(), type));
}

static void
AddAnimationsForProperty(nsIFrame* aFrame, nsCSSProperty aProperty,
                         ElementAnimation* ea, Layer* aLayer,
                         AnimationData& aData, bool aPending)
{
  NS_ASSERTION(aLayer->AsContainerLayer(), "Should only animate ContainerLayer");
  nsStyleContext* styleContext = aFrame->StyleContext();
  nsPresContext* presContext = aFrame->PresContext();
  nsRect bounds = nsDisplayTransform::GetFrameBoundsForTransform(aFrame);
  // all data passed directly to the compositor should be in css pixels
  float scale = nsDeviceContext::AppUnitsPerCSSPixel();

  Animation* animation = aPending ? aLayer->AddAnimationForNextTransaction()
                                  : aLayer->AddAnimation();

  animation->startTime() = ea->mStartTime + ea->mDelay;
  animation->duration() = ea->mIterationDuration;
  animation->numIterations() =
    ea->mIterationCount != NS_IEEEPositiveInfinity() ? ea->mIterationCount : -1;
  animation->direction() = ea->mDirection;
  animation->property() = aProperty;
  animation->data() = aData;

  for (uint32_t propIdx = 0; propIdx < ea->mProperties.Length(); propIdx++) {
    AnimationProperty* property = &ea->mProperties[propIdx];

    if (aProperty != property->mProperty) {
      continue;
    }

    for (uint32_t segIdx = 0; segIdx < property->mSegments.Length(); segIdx++) {
      AnimationPropertySegment* segment = &property->mSegments[segIdx];

      AnimationSegment* animSegment = animation->segments().AppendElement();
      if (aProperty == eCSSProperty_transform) {
        animSegment->startState() = InfallibleTArray<TransformFunction>();
        animSegment->endState() = InfallibleTArray<TransformFunction>();

        nsCSSValueSharedList* list = segment->mFromValue.GetCSSValueSharedListValue();
        AddTransformFunctions(list->mHead, styleContext, presContext, bounds, scale,
                              animSegment->startState().get_ArrayOfTransformFunction());

        list = segment->mToValue.GetCSSValueSharedListValue();
        AddTransformFunctions(list->mHead, styleContext, presContext, bounds, scale,
                              animSegment->endState().get_ArrayOfTransformFunction());
      } else if (aProperty == eCSSProperty_opacity) {
        animSegment->startState() = segment->mFromValue.GetFloatValue();
        animSegment->endState() = segment->mToValue.GetFloatValue();
      }

      animSegment->startPortion() = segment->mFromKey;
      animSegment->endPortion() = segment->mToKey;
      animSegment->sampleFn() = ToTimingFunction(segment->mTimingFunction);
    }
  }
}

/* static */ void
nsDisplayListBuilder::AddAnimationsAndTransitionsToLayer(Layer* aLayer,
                                                         nsDisplayListBuilder* aBuilder,
                                                         nsDisplayItem* aItem,
                                                         nsIFrame* aFrame,
                                                         nsCSSProperty aProperty)
{
  // This function can be called in two ways:  from
  // nsDisplay*::BuildLayer while constructing a layer (with all
  // pointers non-null), or from RestyleManager's handling of
  // UpdateOpacityLayer/UpdateTransformLayer hints.
  MOZ_ASSERT(!aBuilder == !aItem,
             "should only be called in two configurations, with both "
             "aBuilder and aItem, or with neither");
  MOZ_ASSERT(!aItem || aFrame == aItem->Frame(), "frame mismatch");

  bool pending = !aBuilder;

  if (pending) {
    aLayer->ClearAnimationsForNextTransaction();
  } else {
    aLayer->ClearAnimations();
  }

  nsIContent* content = aFrame->GetContent();
  if (!content) {
    return;
  }
  ElementTransitions* et =
    nsTransitionManager::GetTransitionsForCompositor(content, aProperty);

  ElementAnimations* ea =
    nsAnimationManager::GetAnimationsForCompositor(content, aProperty);

  if (!ea && !et) {
    return;
  }

  // If the frame is not prerendered, bail out.
  // Do this check only during layer construction; during updating the
  // caller is required to check it appropriately.
  if (aItem && !aItem->CanUseAsyncAnimations(aBuilder)) {
    // AnimationManager or TransitionManager need to know that we refused to
    // run this animation asynchronously so that they will not throttle the
    // main thread animation.
    aFrame->Properties().Set(nsIFrame::RefusedAsyncAnimation(),
                            reinterpret_cast<void*>(intptr_t(true)));

    // We need to schedule another refresh driver run so that AnimationManager
    // or TransitionManager get a chance to unthrottle the animation.
    aFrame->SchedulePaint();
    return;
  }

  mozilla::TimeStamp currentTime =
    aFrame->PresContext()->RefreshDriver()->MostRecentRefresh();
  AnimationData data;
  if (aProperty == eCSSProperty_transform) {
    nsRect bounds = nsDisplayTransform::GetFrameBoundsForTransform(aFrame);
    // all data passed directly to the compositor should be in css pixels
    float scale = nsDeviceContext::AppUnitsPerCSSPixel();
    gfxPoint3D offsetToTransformOrigin =
      nsDisplayTransform::GetDeltaToTransformOrigin(aFrame, scale, &bounds);
    gfxPoint3D offsetToPerspectiveOrigin =
      nsDisplayTransform::GetDeltaToPerspectiveOrigin(aFrame, scale);
    nscoord perspective = 0.0;
    nsStyleContext* parentStyleContext = aFrame->StyleContext()->GetParent();
    if (parentStyleContext) {
      const nsStyleDisplay* disp = parentStyleContext->StyleDisplay();
      if (disp && disp->mChildPerspective.GetUnit() == eStyleUnit_Coord) {
        perspective = disp->mChildPerspective.GetCoordValue();
      }
    }
    nsPoint origin;
    if (aItem) {
      origin = aItem->ToReferenceFrame();
    } else {
      // transform display items used a reference frame computed from
      // their GetTransformRootFrame().
      nsIFrame* referenceFrame =
        nsLayoutUtils::GetReferenceFrame(GetTransformRootFrame(aFrame));
      origin = aFrame->GetOffsetToCrossDoc(referenceFrame);
    }

    data = TransformData(origin, offsetToTransformOrigin,
                         offsetToPerspectiveOrigin, bounds, perspective,
                         aFrame->PresContext()->AppUnitsPerDevPixel());
  } else if (aProperty == eCSSProperty_opacity) {
    data = null_t();
  }

  if (et) {
    for (uint32_t tranIdx = 0; tranIdx < et->mPropertyTransitions.Length(); tranIdx++) {
      ElementPropertyTransition* pt = &et->mPropertyTransitions[tranIdx];
      if (pt->mProperty != aProperty || !pt->IsRunningAt(currentTime)) {
        continue;
      }

      ElementAnimation anim;
      anim.mIterationCount = 1;
      anim.mDirection = NS_STYLE_ANIMATION_DIRECTION_NORMAL;
      anim.mFillMode = NS_STYLE_ANIMATION_FILL_MODE_NONE;
      // Transition mStartTime is end-of-delay; animation mStartTime
      // is start-of-delay, so set delay here to 0.
      anim.mStartTime = pt->mStartTime;
      anim.mDelay = TimeDuration::FromMilliseconds(0);
      anim.mIterationDuration = pt->mDuration;

      AnimationProperty& prop = *anim.mProperties.AppendElement();
      prop.mProperty = pt->mProperty;

      AnimationPropertySegment& segment = *prop.mSegments.AppendElement();
      segment.mFromKey = 0;
      segment.mToKey = 1;
      segment.mFromValue = pt->mStartValue;
      segment.mToValue = pt->mEndValue;
      segment.mTimingFunction = pt->mTimingFunction;

      AddAnimationsForProperty(aFrame, aProperty, &anim,
                               aLayer, data, pending);

      pt->mIsRunningOnCompositor = true;
    }
    aLayer->SetAnimationGeneration(et->mAnimationGeneration);
  }

  if (ea) {
    for (uint32_t animIdx = 0; animIdx < ea->mAnimations.Length(); animIdx++) {
      ElementAnimation* anim = &ea->mAnimations[animIdx];
      if (!(anim->HasAnimationOfProperty(aProperty) &&
            anim->IsRunningAt(currentTime))) {
        continue;
      }
      AddAnimationsForProperty(aFrame, aProperty, anim,
                               aLayer, data, pending);
    }
    aLayer->SetAnimationGeneration(ea->mAnimationGeneration);
  }
}

nsDisplayListBuilder::nsDisplayListBuilder(nsIFrame* aReferenceFrame,
    Mode aMode, bool aBuildCaret)
    : mReferenceFrame(aReferenceFrame),
      mIgnoreScrollFrame(nullptr),
      mLayerEventRegions(nullptr),
      mCurrentTableItem(nullptr),
      mFinalTransparentRegion(nullptr),
      mCachedOffsetFrame(aReferenceFrame),
      mCachedReferenceFrame(aReferenceFrame),
      mCachedOffset(0, 0),
      mGlassDisplayItem(nullptr),
      mMode(aMode),
      mBuildCaret(aBuildCaret),
      mIgnoreSuppression(false),
      mHadToIgnoreSuppression(false),
      mIsAtRootOfPseudoStackingContext(false),
      mIncludeAllOutOfFlows(false),
      mDescendIntoSubdocuments(true),
      mSelectedFramesOnly(false),
      mAccurateVisibleRegions(false),
      mAllowMergingAndFlattening(true),
      mWillComputePluginGeometry(false),
      mInTransform(false),
      mInFixedPos(false),
      mSyncDecodeImages(false),
      mIsPaintingToWindow(false),
      mIsCompositingCheap(false),
      mContainsPluginItem(false),
      mContainsBlendMode(false),
      mAncestorHasTouchEventHandler(false),
      mHaveScrollableDisplayPort(false)
{
  MOZ_COUNT_CTOR(nsDisplayListBuilder);
  PL_InitArenaPool(&mPool, "displayListArena", 1024,
                   std::max(NS_ALIGNMENT_OF(void*),NS_ALIGNMENT_OF(double))-1);

  nsPresContext* pc = aReferenceFrame->PresContext();
  nsIPresShell *shell = pc->PresShell();
  if (pc->IsRenderingOnlySelection()) {
    nsCOMPtr<nsISelectionController> selcon(do_QueryInterface(shell));
    if (selcon) {
      selcon->GetSelection(nsISelectionController::SELECTION_NORMAL,
                           getter_AddRefs(mBoundingSelection));
    }
  }

  nsCSSRendering::BeginFrameTreesLocked();
  PR_STATIC_ASSERT(nsDisplayItem::TYPE_MAX < (1 << nsDisplayItem::TYPE_BITS));
}

static void MarkFrameForDisplay(nsIFrame* aFrame, nsIFrame* aStopAtFrame) {
  for (nsIFrame* f = aFrame; f;
       f = nsLayoutUtils::GetParentOrPlaceholderFor(f)) {
    if (f->GetStateBits() & NS_FRAME_FORCE_DISPLAY_LIST_DESCEND_INTO)
      return;
    f->AddStateBits(NS_FRAME_FORCE_DISPLAY_LIST_DESCEND_INTO);
    if (f == aStopAtFrame) {
      // we've reached a frame that we know will be painted, so we can stop.
      break;
    }
  }
}

void nsDisplayListBuilder::MarkOutOfFlowFrameForDisplay(nsIFrame* aDirtyFrame,
                                                        nsIFrame* aFrame,
                                                        const nsRect& aDirtyRect)
{
  nsRect dirtyRectRelativeToDirtyFrame = aDirtyRect;
  if (nsLayoutUtils::IsFixedPosFrameInDisplayPort(aFrame)) {
    NS_ASSERTION(aDirtyFrame == aFrame->GetParent(), "Dirty frame should be viewport frame");
    // position: fixed items are reflowed into and only drawn inside the
    // viewport, or the scroll position clamping scrollport size, if one is
    // set.
    nsIPresShell* ps = aFrame->PresContext()->PresShell();
    dirtyRectRelativeToDirtyFrame.MoveTo(0, 0);
    if (ps->IsScrollPositionClampingScrollPortSizeSet()) {
      dirtyRectRelativeToDirtyFrame.SizeTo(ps->GetScrollPositionClampingScrollPortSize());
    } else {
      dirtyRectRelativeToDirtyFrame.SizeTo(aDirtyFrame->GetSize());
    }
  }

  nsRect dirty = dirtyRectRelativeToDirtyFrame - aFrame->GetOffsetTo(aDirtyFrame);
  nsRect overflowRect = aFrame->GetVisualOverflowRect();

  if (aFrame->IsTransformed() &&
      nsLayoutUtils::HasAnimationsForCompositor(aFrame->GetContent(),
                                                eCSSProperty_transform)) {
   /**
    * Add a fuzz factor to the overflow rectangle so that elements only just
    * out of view are pulled into the display list, so they can be
    * prerendered if necessary.
    */
    overflowRect.Inflate(nsPresContext::CSSPixelsToAppUnits(32));
  }

  if (!dirty.IntersectRect(dirty, overflowRect))
    return;
  const DisplayItemClip* clip = mClipState.GetClipForContainingBlockDescendants();
  OutOfFlowDisplayData* data = clip ? new OutOfFlowDisplayData(*clip, dirty)
    : new OutOfFlowDisplayData(dirty);
  aFrame->Properties().Set(nsDisplayListBuilder::OutOfFlowDisplayDataProperty(), data);

  MarkFrameForDisplay(aFrame, aDirtyFrame);
}

static void UnmarkFrameForDisplay(nsIFrame* aFrame) {
  nsPresContext* presContext = aFrame->PresContext();
  presContext->PropertyTable()->
    Delete(aFrame, nsDisplayListBuilder::OutOfFlowDisplayDataProperty());

  for (nsIFrame* f = aFrame; f;
       f = nsLayoutUtils::GetParentOrPlaceholderFor(f)) {
    if (!(f->GetStateBits() & NS_FRAME_FORCE_DISPLAY_LIST_DESCEND_INTO))
      return;
    f->RemoveStateBits(NS_FRAME_FORCE_DISPLAY_LIST_DESCEND_INTO);
  }
}

static bool gPrintApzcTree = false;

static bool GetApzcTreePrintPref() {
  static bool initialized = false;
  if (!initialized) {
    Preferences::AddBoolVarCache(&gPrintApzcTree, "apz.printtree", gPrintApzcTree);
    initialized = true;
  }
  return gPrintApzcTree;
}

static void RecordFrameMetrics(nsIFrame* aForFrame,
                               nsIFrame* aScrollFrame,
                               const nsIFrame* aReferenceFrame,
                               ContainerLayer* aRoot,
                               const nsRect& aVisibleRect,
                               const nsRect& aViewport,
                               nsRect* aDisplayPort,
                               nsRect* aCriticalDisplayPort,
                               ViewID aScrollId,
                               bool aIsRoot,
                               const ContainerLayerParameters& aContainerParameters) {
  nsPresContext* presContext = aForFrame->PresContext();
  int32_t auPerDevPixel = presContext->AppUnitsPerDevPixel();
  LayoutDeviceToLayerScale resolution(aContainerParameters.mXScale, aContainerParameters.mYScale);

  nsIntRect visible = aVisibleRect.ScaleToNearestPixels(
    resolution.scale, resolution.scale, auPerDevPixel);
  aRoot->SetVisibleRegion(visible);

  FrameMetrics metrics;
  metrics.mViewport = CSSRect::FromAppUnits(aViewport);
  if (aDisplayPort) {
    metrics.mDisplayPort = CSSRect::FromAppUnits(*aDisplayPort);
    if (aCriticalDisplayPort) {
      metrics.mCriticalDisplayPort = CSSRect::FromAppUnits(*aCriticalDisplayPort);
    }
  }

  nsIScrollableFrame* scrollableFrame = nullptr;
  if (aScrollFrame)
    scrollableFrame = aScrollFrame->GetScrollTargetFrame();

  metrics.mScrollableRect = CSSRect::FromAppUnits(
    nsLayoutUtils::CalculateScrollableRectForFrame(scrollableFrame, aForFrame));

  if (scrollableFrame) {
    nsPoint scrollPosition = scrollableFrame->GetScrollPosition();
    metrics.SetScrollOffset(CSSPoint::FromAppUnits(scrollPosition));

    // If the frame was scrolled since the last layers update, and by
    // something other than the APZ code, we want to tell the APZ to update
    // its scroll offset.
    nsIAtom* originOfLastScroll = scrollableFrame->OriginOfLastScroll();
    if (originOfLastScroll && originOfLastScroll != nsGkAtoms::apz) {
      metrics.SetScrollOffsetUpdated(scrollableFrame->CurrentScrollGeneration());
    }
  }

  metrics.mScrollId = aScrollId;
  metrics.mIsRoot = aIsRoot;

  // Only the root scrollable frame for a given presShell should pick up
  // the presShell's resolution. All the other frames are 1.0.
  nsIPresShell* presShell = presContext->GetPresShell();
  if (aScrollFrame == presShell->GetRootScrollFrame()) {
    metrics.mResolution = ParentLayerToLayerScale(presShell->GetXResolution(),
                                                  presShell->GetYResolution());
  } else {
    metrics.mResolution = ParentLayerToLayerScale(1.0f);
  }

  // For the cumulateive resolution, multiply the resolutions of all the
  // presShells back up to the root
  metrics.mCumulativeResolution = LayoutDeviceToLayerScale(1.0f);
  nsIPresShell* curPresShell = presShell;
  while (curPresShell != nullptr) {
    ParentLayerToLayerScale presShellResolution(curPresShell->GetXResolution(),
                                                curPresShell->GetYResolution());
    metrics.mCumulativeResolution.scale *= presShellResolution.scale;
    nsPresContext* parentContext = curPresShell->GetPresContext()->GetParentPresContext();
    curPresShell = parentContext ? parentContext->GetPresShell() : nullptr;
  }

  metrics.mDevPixelsPerCSSPixel = CSSToLayoutDeviceScale(
    (float)nsPresContext::AppUnitsPerCSSPixel() / auPerDevPixel);

  // Initially, AsyncPanZoomController should render the content to the screen
  // at the painted resolution.
  const LayerToScreenScale layerToScreenScale(1.0f);
  metrics.SetZoom(metrics.mCumulativeResolution * metrics.mDevPixelsPerCSSPixel
                  * layerToScreenScale);

  if (presShell) {
    nsIDocument* document = nullptr;
    document = presShell->GetDocument();
    if (document) {
      nsCOMPtr<nsPIDOMWindow> innerWin(document->GetInnerWindow());
      if (innerWin) {
        metrics.mMayHaveTouchListeners = innerWin->HasTouchEventListeners();
      }
    }
  }

  LayoutDeviceToParentLayerScale layoutToParentLayerScale =
    // The ScreenToParentLayerScale should be mTransformScale which is not calculated yet,
    // but we don't yet handle CSS transforms, so we assume it's 1 here.
    metrics.mCumulativeResolution * LayerToScreenScale(1.0) * ScreenToParentLayerScale(1.0);

  // Calculate the composition bounds as the size of the scroll frame and
  // its origin relative to the reference frame.
  // If aScrollFrame is null, we are in a document without a root scroll frame,
  // so it's a xul document. In this case, use the size of the viewport frame.
  nsIFrame* frameForCompositionBoundsCalculation = aScrollFrame ? aScrollFrame : aForFrame;
  nsRect compositionBounds(frameForCompositionBoundsCalculation->GetOffsetToCrossDoc(aReferenceFrame),
                           frameForCompositionBoundsCalculation->GetSize());
  metrics.mCompositionBounds = RoundedToInt(LayoutDeviceRect::FromAppUnits(compositionBounds, auPerDevPixel)
                                            * layoutToParentLayerScale);


  // For the root scroll frame of the root content document, the above calculation
  // will yield the size of the viewport frame as the composition bounds, which
  // doesn't actually correspond to what is visible when
  // nsIDOMWindowUtils::setCSSViewport has been called to modify the visible area of
  // the prescontext that the viewport frame is reflowed into. In that case if our
  // document has a widget then the widget's bounds will correspond to what is
  // visible. If we don't have a widget the root view's bounds correspond to what
  // would be visible because they don't get modified by setCSSViewport.
  bool isRootContentDocRootScrollFrame = presContext->IsRootContentDocument()
                                      && aScrollFrame == presShell->GetRootScrollFrame();
  if (isRootContentDocRootScrollFrame) {
    if (nsIFrame* rootFrame = presShell->GetRootFrame()) {
      if (nsView* view = rootFrame->GetView()) {
        nsRect viewBoundsAppUnits = view->GetBounds() + rootFrame->GetOffsetToCrossDoc(aReferenceFrame);
        ParentLayerIntRect viewBounds = RoundedToInt(LayoutDeviceRect::FromAppUnits(viewBoundsAppUnits, auPerDevPixel)
                                                     * layoutToParentLayerScale);

        // On Android, we need to do things a bit differently to get things
        // right (see bug 983208, bug 988882). We use the bounds of the nearest
        // widget, but clamp the height to the view bounds height. This clamping
        // is done to get correct results for a page where the page is sized to
        // the screen and thus the dynamic toolbar never disappears. In such a
        // case, we want the composition bounds to exclude the toolbar height,
        // but the widget bounds includes it. We don't currently have a good way
        // of knowing about the toolbar height, but clamping to the view bounds
        // height gives the correct answer in the cases we care about.
        nsIWidget* widget =
#ifdef MOZ_WIDGET_ANDROID
            rootFrame->GetNearestWidget();
#else
            view->GetWidget();
#endif
        if (widget) {
          nsIntRect widgetBounds;
          widget->GetBounds(widgetBounds);
          metrics.mCompositionBounds = ViewAs<ParentLayerPixel>(widgetBounds);
#ifdef MOZ_WIDGET_ANDROID
          if (viewBounds.height < metrics.mCompositionBounds.height) {
            metrics.mCompositionBounds.height = viewBounds.height;
          }
#endif
        } else {
          metrics.mCompositionBounds = viewBounds;
        }
      }
    }
  }

  // Adjust composition bounds for the size of scroll bars.
  if (scrollableFrame && !LookAndFeel::GetInt(LookAndFeel::eIntID_UseOverlayScrollbars)) {
    nsMargin sizes = scrollableFrame->GetActualScrollbarSizes();
    // Scrollbars are not subject to scaling, so CSS pixels = layer pixels for them.
    ParentLayerIntMargin boundMargins = RoundedToInt(CSSMargin::FromAppUnits(sizes) * CSSToParentLayerScale(1.0f));
    metrics.mCompositionBounds.Deflate(boundMargins);
  }

  metrics.SetRootCompositionSize(
    nsLayoutUtils::CalculateRootCompositionSize(aScrollFrame ? aScrollFrame : aForFrame,
                                                isRootContentDocRootScrollFrame, metrics));

  if (GetApzcTreePrintPref()) {
    if (nsIContent* content = frameForCompositionBoundsCalculation->GetContent()) {
      nsAutoString contentDescription;
      content->Describe(contentDescription);
      metrics.SetContentDescription(NS_LossyConvertUTF16toASCII(contentDescription).get());
    }
  }

  metrics.mPresShellId = presShell->GetPresShellId();

  // If the scroll frame's content is marked 'scrollgrab', record this
  // in the FrameMetrics so APZ knows to provide the scroll grabbing
  // behaviour.
  if (aScrollFrame && nsContentUtils::HasScrollgrab(aScrollFrame->GetContent())) {
    metrics.mHasScrollgrab = true;
  }

  aRoot->SetFrameMetrics(metrics);
}

nsDisplayListBuilder::~nsDisplayListBuilder() {
  NS_ASSERTION(mFramesMarkedForDisplay.Length() == 0,
               "All frames should have been unmarked");
  NS_ASSERTION(mPresShellStates.Length() == 0,
               "All presshells should have been exited");
  NS_ASSERTION(!mCurrentTableItem, "No table item should be active");

  nsCSSRendering::EndFrameTreesLocked();

  for (uint32_t i = 0; i < mDisplayItemClipsToDestroy.Length(); ++i) {
    mDisplayItemClipsToDestroy[i]->DisplayItemClip::~DisplayItemClip();
  }

  PL_FinishArenaPool(&mPool);
  MOZ_COUNT_DTOR(nsDisplayListBuilder);
}

uint32_t
nsDisplayListBuilder::GetBackgroundPaintFlags() {
  uint32_t flags = 0;
  if (mSyncDecodeImages) {
    flags |= nsCSSRendering::PAINTBG_SYNC_DECODE_IMAGES;
  }
  if (mIsPaintingToWindow) {
    flags |= nsCSSRendering::PAINTBG_TO_WINDOW;
  }
  return flags;
}

void
nsDisplayListBuilder::SubtractFromVisibleRegion(nsRegion* aVisibleRegion,
                                                const nsRegion& aRegion)
{
  if (aRegion.IsEmpty())
    return;

  nsRegion tmp;
  tmp.Sub(*aVisibleRegion, aRegion);
  // Don't let *aVisibleRegion get too complex, but don't let it fluff out
  // to its bounds either, which can be very bad (see bug 516740).
  // Do let aVisibleRegion get more complex if by doing so we reduce its
  // area by at least half.
  if (GetAccurateVisibleRegions() || tmp.GetNumRects() <= 15 ||
      tmp.Area() <= aVisibleRegion->Area()/2) {
    *aVisibleRegion = tmp;
  }
}

nsCaret *
nsDisplayListBuilder::GetCaret() {
  nsRefPtr<nsCaret> caret = CurrentPresShellState()->mPresShell->GetCaret();
  return caret;
}

void
nsDisplayListBuilder::EnterPresShell(nsIFrame* aReferenceFrame,
                                     const nsRect& aDirtyRect) {
  PresShellState* state = mPresShellStates.AppendElement();
  if (!state)
    return;
  state->mPresShell = aReferenceFrame->PresContext()->PresShell();
  state->mCaretFrame = nullptr;
  state->mFirstFrameMarkedForDisplay = mFramesMarkedForDisplay.Length();

  state->mPresShell->UpdateCanvasBackground();

  if (mIsPaintingToWindow) {
    mReferenceFrame->AddPaintedPresShell(state->mPresShell);

    state->mPresShell->IncrementPaintCount();
  }

  bool buildCaret = mBuildCaret;
  if (mIgnoreSuppression || !state->mPresShell->IsPaintingSuppressed()) {
    if (state->mPresShell->IsPaintingSuppressed()) {
      mHadToIgnoreSuppression = true;
    }
    state->mIsBackgroundOnly = false;
  } else {
    state->mIsBackgroundOnly = true;
    buildCaret = false;
  }

  if (!buildCaret)
    return;

  nsRefPtr<nsCaret> caret = state->mPresShell->GetCaret();
  state->mCaretFrame = caret->GetCaretFrame();
  NS_ASSERTION(state->mCaretFrame == caret->GetCaretFrame(),
               "GetCaretFrame() is unstable");

  if (state->mCaretFrame) {
    // Check if the dirty rect intersects with the caret's dirty rect.
    nsRect caretRect =
      caret->GetCaretRect() + state->mCaretFrame->GetOffsetTo(aReferenceFrame);
    if (caretRect.Intersects(aDirtyRect)) {
      // Okay, our rects intersect, let's mark the frame and all of its ancestors.
      mFramesMarkedForDisplay.AppendElement(state->mCaretFrame);
      MarkFrameForDisplay(state->mCaretFrame, nullptr);
    }
  }
}

void
nsDisplayListBuilder::LeavePresShell(nsIFrame* aReferenceFrame,
                                     const nsRect& aDirtyRect) {
  if (CurrentPresShellState()->mPresShell != aReferenceFrame->PresContext()->PresShell()) {
    // Must have not allocated a state for this presshell, presumably due
    // to OOM.
    return;
  }

  ResetMarkedFramesForDisplayList();
  mPresShellStates.SetLength(mPresShellStates.Length() - 1);
}

void
nsDisplayListBuilder::ResetMarkedFramesForDisplayList()
{
  // Unmark and pop off the frames marked for display in this pres shell.
  uint32_t firstFrameForShell = CurrentPresShellState()->mFirstFrameMarkedForDisplay;
  for (uint32_t i = firstFrameForShell;
       i < mFramesMarkedForDisplay.Length(); ++i) {
    UnmarkFrameForDisplay(mFramesMarkedForDisplay[i]);
  }
  mFramesMarkedForDisplay.SetLength(firstFrameForShell);
}

void
nsDisplayListBuilder::MarkFramesForDisplayList(nsIFrame* aDirtyFrame,
                                               const nsFrameList& aFrames,
                                               const nsRect& aDirtyRect) {
  for (nsFrameList::Enumerator e(aFrames); !e.AtEnd(); e.Next()) {
    mFramesMarkedForDisplay.AppendElement(e.get());
    MarkOutOfFlowFrameForDisplay(aDirtyFrame, e.get(), aDirtyRect);
  }
}

void
nsDisplayListBuilder::MarkPreserve3DFramesForDisplayList(nsIFrame* aDirtyFrame, const nsRect& aDirtyRect)
{
  nsAutoTArray<nsIFrame::ChildList,4> childListArray;
  aDirtyFrame->GetChildLists(&childListArray);
  nsIFrame::ChildListArrayIterator lists(childListArray);
  for (; !lists.IsDone(); lists.Next()) {
    nsFrameList::Enumerator childFrames(lists.CurrentList());
    for (; !childFrames.AtEnd(); childFrames.Next()) {
      nsIFrame *child = childFrames.get();
      if (child->Preserves3D()) {
        mFramesMarkedForDisplay.AppendElement(child);
        nsRect dirty = aDirtyRect - child->GetOffsetTo(aDirtyFrame);

        child->Properties().Set(nsDisplayListBuilder::Preserve3DDirtyRectProperty(),
                           new nsRect(dirty));

        MarkFrameForDisplay(child, aDirtyFrame);
      }
    }
  }
}

void*
nsDisplayListBuilder::Allocate(size_t aSize) {
  void *tmp;
  PL_ARENA_ALLOCATE(tmp, &mPool, aSize);
  if (!tmp) {
    NS_RUNTIMEABORT("out of memory");
  }
  return tmp;
}

const DisplayItemClip*
nsDisplayListBuilder::AllocateDisplayItemClip(const DisplayItemClip& aOriginal)
{
  void* p = Allocate(sizeof(DisplayItemClip));
  if (!aOriginal.GetRoundedRectCount()) {
    memcpy(p, &aOriginal, sizeof(DisplayItemClip));
    return static_cast<DisplayItemClip*>(p);
  }

  DisplayItemClip* c = new (p) DisplayItemClip(aOriginal);
  mDisplayItemClipsToDestroy.AppendElement(c);
  return c;
}

void nsDisplayListSet::MoveTo(const nsDisplayListSet& aDestination) const
{
  aDestination.BorderBackground()->AppendToTop(BorderBackground());
  aDestination.BlockBorderBackgrounds()->AppendToTop(BlockBorderBackgrounds());
  aDestination.Floats()->AppendToTop(Floats());
  aDestination.Content()->AppendToTop(Content());
  aDestination.PositionedDescendants()->AppendToTop(PositionedDescendants());
  aDestination.Outlines()->AppendToTop(Outlines());
}

void
nsDisplayList::FlattenTo(nsTArray<nsDisplayItem*>* aElements) {
  nsDisplayItem* item;
  while ((item = RemoveBottom()) != nullptr) {
    if (item->GetType() == nsDisplayItem::TYPE_WRAP_LIST) {
      item->GetSameCoordinateSystemChildren()->FlattenTo(aElements);
      item->~nsDisplayItem();
    } else {
      aElements->AppendElement(item);
    }
  }
}

nsRect
nsDisplayList::GetBounds(nsDisplayListBuilder* aBuilder) const {
  nsRect bounds;
  for (nsDisplayItem* i = GetBottom(); i != nullptr; i = i->GetAbove()) {
    bounds.UnionRect(bounds, i->GetClippedBounds(aBuilder));
  }
  return bounds;
}

bool
nsDisplayList::ComputeVisibilityForRoot(nsDisplayListBuilder* aBuilder,
                                        nsRegion* aVisibleRegion,
                                        nsIFrame* aDisplayPortFrame) {
  PROFILER_LABEL("nsDisplayList", "ComputeVisibilityForRoot");
  nsRegion r;
  r.And(*aVisibleRegion, GetBounds(aBuilder));
  return ComputeVisibilityForSublist(aBuilder, aVisibleRegion,
                                     r.GetBounds(), r.GetBounds(),
                                     aDisplayPortFrame);
}

static nsRegion
TreatAsOpaque(nsDisplayItem* aItem, nsDisplayListBuilder* aBuilder)
{
  bool snap;
  nsRegion opaque = aItem->GetOpaqueRegion(aBuilder, &snap);
  if (aBuilder->IsForPluginGeometry()) {
    // Treat all leaf chrome items as opaque, unless their frames are opacity:0.
    // Since opacity:0 frames generate an nsDisplayOpacity, that item will
    // not be treated as opaque here, so opacity:0 chrome content will be
    // effectively ignored, as it should be.
    // We treat leaf chrome items as opaque to ensure that they cover
    // content plugins, for security reasons.
    // Non-leaf chrome items don't render contents of their own so shouldn't
    // be treated as opaque (and their bounds is just the union of their
    // children, which might be a large area their contents don't really cover).
    nsIFrame* f = aItem->Frame();
    if (f->PresContext()->IsChrome() && !aItem->GetChildren() &&
        f->StyleDisplay()->mOpacity != 0.0) {
      opaque = aItem->GetBounds(aBuilder, &snap);
    }
  }
  if (opaque.IsEmpty()) {
    return opaque;
  }
  nsRegion opaqueClipped;
  nsRegionRectIterator iter(opaque);
  for (const nsRect* r = iter.Next(); r; r = iter.Next()) {
    opaqueClipped.Or(opaqueClipped, aItem->GetClip().ApproximateIntersectInward(*r));
  }
  return opaqueClipped;
}

/* Checks if aPotentialScrollItem is a scroll layer item and aPotentialScrollbarItem
 * is an overlay scrollbar item for the same scroll frame.
 */
static bool
IsScrollLayerItemAndOverlayScrollbarForScrollFrame(
  nsDisplayItem* aPotentialScrollItem, nsDisplayItem* aPotentialScrollbarItem)
{
  if (aPotentialScrollItem->GetType() == nsDisplayItem::TYPE_SCROLL_LAYER &&
      aPotentialScrollbarItem &&
      aPotentialScrollbarItem->GetType() == nsDisplayItem::TYPE_OWN_LAYER &&
      LookAndFeel::GetInt(LookAndFeel::eIntID_UseOverlayScrollbars)) {
    nsDisplayScrollLayer* scrollItem =
      static_cast<nsDisplayScrollLayer*>(aPotentialScrollItem);
    nsDisplayOwnLayer* layerItem =
      static_cast<nsDisplayOwnLayer*>(aPotentialScrollbarItem);
    if ((layerItem->GetFlags() &
         (nsDisplayOwnLayer::VERTICAL_SCROLLBAR |
          nsDisplayOwnLayer::HORIZONTAL_SCROLLBAR)) &&
        layerItem->Frame()->GetParent() == scrollItem->GetScrollFrame()) {
      return true;
    }
  }
  return false;
}

bool
nsDisplayList::ComputeVisibilityForSublist(nsDisplayListBuilder* aBuilder,
                                           nsRegion* aVisibleRegion,
                                           const nsRect& aListVisibleBounds,
                                           const nsRect& aAllowVisibleRegionExpansion,
                                           nsIFrame* aDisplayPortFrame) {
#ifdef DEBUG
  nsRegion r;
  r.And(*aVisibleRegion, GetBounds(aBuilder));
  NS_ASSERTION(r.GetBounds().IsEqualInterior(aListVisibleBounds),
               "bad aListVisibleBounds");
#endif

  mVisibleRect = aListVisibleBounds;
  bool anyVisible = false;

  nsAutoTArray<nsDisplayItem*, 512> elements;
  FlattenTo(&elements);

  bool forceTransparentSurface = false;

  for (int32_t i = elements.Length() - 1; i >= 0; --i) {
    nsDisplayItem* item = elements[i];
    nsDisplayItem* belowItem = i < 1 ? nullptr : elements[i - 1];

    nsDisplayList* list = item->GetSameCoordinateSystemChildren();
    if (aBuilder->AllowMergingAndFlattening()) {
      if (belowItem && item->TryMerge(aBuilder, belowItem)) {
        belowItem->~nsDisplayItem();
        elements.ReplaceElementsAt(i - 1, 1, item);
        continue;
      }

      // If an overlay scrollbar item is between a scroll layer item and the
      // other scroll layer items that we need to merge with just move the
      // scrollbar item up, that way it will be on top of the scrolled content
      // and we can try to merge all the scroll layer items.
      if (IsScrollLayerItemAndOverlayScrollbarForScrollFrame(item, belowItem)) {
        elements[i] = belowItem;
        elements[i-1] = item;
        i++;
        continue;
      }

      if (list && item->ShouldFlattenAway(aBuilder)) {
        // The elements on the list >= i no longer serve any use.
        elements.SetLength(i);
        list->FlattenTo(&elements);
        i = elements.Length();
        item->~nsDisplayItem();
        continue;
      }
    }

    nsRect bounds = item->GetClippedBounds(aBuilder);

    nsRegion itemVisible;
    itemVisible.And(*aVisibleRegion, bounds);
    item->mVisibleRect = itemVisible.GetBounds();

    if (item->ComputeVisibility(aBuilder, aVisibleRegion,
                                aAllowVisibleRegionExpansion.Intersect(bounds))) {
      anyVisible = true;

      // If we're in a displayport, we need to make sure that fixed position
      // items do not subtract from the visible region, as async scrolling
      // may expose these occluded areas.
      // If the item is fixed pos in the same document as the displayport
      // then don't let it occlude this list. The only other case possible
      // is that the fixed pos content is in a child document, in which it
      // would scroll with the rest of the content.
      bool occlude = true;
      if (aDisplayPortFrame && item->IsInFixedPos()) {
        if (item->Frame()->PresContext() == aDisplayPortFrame->PresContext()) {
          occlude = false;
        }
      }

      if (occlude) {
        nsRegion opaque = TreatAsOpaque(item, aBuilder);
        // Subtract opaque item from the visible region
        aBuilder->SubtractFromVisibleRegion(aVisibleRegion, opaque);
      }

      if (aBuilder->NeedToForceTransparentSurfaceForItem(item) ||
          (list && list->NeedsTransparentSurface())) {
        forceTransparentSurface = true;
      }
    }
    AppendToBottom(item);
  }

  mIsOpaque = !aVisibleRegion->Intersects(mVisibleRect);
  mForceTransparentSurface = forceTransparentSurface;
#if defined(DEBUG) || defined(MOZ_DUMP_PAINTING)
  mDidComputeVisibility = true;
#endif
  return anyVisible;
}

void nsDisplayList::PaintRoot(nsDisplayListBuilder* aBuilder,
                              nsRenderingContext* aCtx,
                              uint32_t aFlags) const {
  PROFILER_LABEL("nsDisplayList", "PaintRoot");
  PaintForFrame(aBuilder, aCtx, aBuilder->RootReferenceFrame(), aFlags);
}

/**
 * We paint by executing a layer manager transaction, constructing a
 * single layer representing the display list, and then making it the
 * root of the layer manager, drawing into the ThebesLayers.
 */
void nsDisplayList::PaintForFrame(nsDisplayListBuilder* aBuilder,
                                  nsRenderingContext* aCtx,
                                  nsIFrame* aForFrame,
                                  uint32_t aFlags) const {
  NS_ASSERTION(mDidComputeVisibility,
               "Must call ComputeVisibility before calling Paint");

  nsRefPtr<LayerManager> layerManager;
  bool widgetTransaction = false;
  bool allowRetaining = false;
  bool doBeginTransaction = true;
  nsView *view = nullptr;
  if (aFlags & PAINT_USE_WIDGET_LAYERS) {
    nsIFrame* rootReferenceFrame = aBuilder->RootReferenceFrame();
    view = rootReferenceFrame->GetView();
    NS_ASSERTION(rootReferenceFrame == nsLayoutUtils::GetDisplayRootFrame(rootReferenceFrame),
                 "Reference frame must be a display root for us to use the layer manager");
    nsIWidget* window = rootReferenceFrame->GetNearestWidget();
    if (window) {
      layerManager = window->GetLayerManager(&allowRetaining);
      if (layerManager) {
        doBeginTransaction = !(aFlags & PAINT_EXISTING_TRANSACTION);
        widgetTransaction = true;
      }
    }
  }
  if (!layerManager) {
    if (!aCtx) {
      NS_WARNING("Nowhere to paint into");
      return;
    }
    layerManager = new BasicLayerManager();
  }

  // Store the existing layer builder to reinstate it on return.
  FrameLayerBuilder *oldBuilder = layerManager->GetLayerBuilder();

  FrameLayerBuilder *layerBuilder = new FrameLayerBuilder();
  layerBuilder->Init(aBuilder, layerManager);

  if (aFlags & PAINT_COMPRESSED) {
    layerBuilder->SetLayerTreeCompressionMode();
  }

  if (aFlags & PAINT_FLUSH_LAYERS) {
    FrameLayerBuilder::InvalidateAllLayers(layerManager);
  }

  if (doBeginTransaction) {
    if (aCtx) {
      layerManager->BeginTransactionWithTarget(aCtx->ThebesContext());
    } else {
      layerManager->BeginTransaction();
    }
  }
  if (widgetTransaction) {
    layerBuilder->DidBeginRetainedLayerTransaction(layerManager);
  }

  nsPresContext* presContext = aForFrame->PresContext();
  nsIPresShell* presShell = presContext->GetPresShell();

  NotifySubDocInvalidationFunc computeInvalidFunc =
    presContext->MayHavePaintEventListenerInSubDocument() ? nsPresContext::NotifySubDocInvalidation : 0;
  bool computeInvalidRect = (computeInvalidFunc ||
                             (!layerManager->IsCompositingCheap() && layerManager->NeedsWidgetInvalidation())) &&
                            widgetTransaction;

  nsAutoPtr<LayerProperties> props(computeInvalidRect ? 
                                     LayerProperties::CloneFrom(layerManager->GetRoot()) : 
                                     nullptr);

  ContainerLayerParameters containerParameters
    (presShell->GetXResolution(), presShell->GetYResolution());
  nsRefPtr<ContainerLayer> root = layerBuilder->
    BuildContainerLayerFor(aBuilder, layerManager, aForFrame, nullptr, *this,
                           containerParameters, nullptr);

  nsIDocument* document = nullptr;
  if (presShell) {
    document = presShell->GetDocument();
  }

  if (widgetTransaction ||
      // SVG-as-an-image docs don't paint as part of the retained layer tree,
      // but they still need the invalidation state bits cleared in order for
      // invalidation for CSS/SMIL animation to work properly.
      (document && document->IsBeingUsedAsImage())) {
    aForFrame->ClearInvalidationStateBits();
  }

  if (!root) {
    layerManager->SetUserData(&gLayerManagerLayerBuilder, oldBuilder);
    return;
  }
  // Root is being scaled up by the X/Y resolution. Scale it back down.
  root->SetPostScale(1.0f/containerParameters.mXScale,
                     1.0f/containerParameters.mYScale);

  ViewID id = FrameMetrics::NULL_SCROLL_ID;
  bool isRoot = presContext->IsRootContentDocument();

  nsIFrame* rootScrollFrame = presShell->GetRootScrollFrame();
  nsRect displayport, criticalDisplayport;
  bool usingDisplayport = false;
  bool usingCriticalDisplayport = false;
  if (rootScrollFrame) {
    nsIContent* content = rootScrollFrame->GetContent();
    if (content) {
      usingDisplayport = nsLayoutUtils::GetDisplayPort(content, &displayport);
      usingCriticalDisplayport =
        nsLayoutUtils::GetCriticalDisplayPort(content, &criticalDisplayport);

      // If this is the root content document, we want it to have a scroll id.
      if (isRoot) {
        id = nsLayoutUtils::FindOrCreateIDFor(content);
      }
    }
  }

  nsRect viewport(aBuilder->ToReferenceFrame(aForFrame), aForFrame->GetSize());

  RecordFrameMetrics(aForFrame, rootScrollFrame,
                     aBuilder->FindReferenceFrameFor(aForFrame),
                     root, mVisibleRect, viewport,
                     (usingDisplayport ? &displayport : nullptr),
                     (usingCriticalDisplayport ? &criticalDisplayport : nullptr),
                     id, isRoot, containerParameters);
  if (usingDisplayport &&
      !(root->GetContentFlags() & Layer::CONTENT_OPAQUE)) {
    // See bug 693938, attachment 567017
    NS_WARNING("Transparent content with displayports can be expensive.");
  }

  layerManager->SetRoot(root);
  layerBuilder->WillEndTransaction();
  bool temp = aBuilder->SetIsCompositingCheap(layerManager->IsCompositingCheap());
  LayerManager::EndTransactionFlags flags = LayerManager::END_DEFAULT;
  if (layerManager->NeedsWidgetInvalidation()) {
    if (aFlags & PAINT_NO_COMPOSITE) {
      flags = LayerManager::END_NO_COMPOSITE;
    }
  } else {
    // Client layer managers never composite directly, so
    // we don't need to worry about END_NO_COMPOSITE.
    if (aBuilder->WillComputePluginGeometry()) {
      flags = LayerManager::END_NO_REMOTE_COMPOSITE;
    }
  }

  layerManager->EndTransaction(FrameLayerBuilder::DrawThebesLayer,
                               aBuilder, flags);
  aBuilder->SetIsCompositingCheap(temp);
  layerBuilder->DidEndTransaction();

  nsIntRegion invalid;
  if (props) {
    invalid = props->ComputeDifferences(root, computeInvalidFunc);
  } else if (widgetTransaction) {
    LayerProperties::ClearInvalidations(root);
  }

  bool shouldInvalidate = layerManager->NeedsWidgetInvalidation();
  if (view) {
    if (props) {
      if (!invalid.IsEmpty()) {
        nsIntRect bounds = invalid.GetBounds();
        nsRect rect(presContext->DevPixelsToAppUnits(bounds.x),
                    presContext->DevPixelsToAppUnits(bounds.y),
                    presContext->DevPixelsToAppUnits(bounds.width),
                    presContext->DevPixelsToAppUnits(bounds.height));
        if (shouldInvalidate) {
          view->GetViewManager()->InvalidateViewNoSuppression(view, rect);
        }
        presContext->NotifyInvalidation(bounds, 0);
      }
    } else if (shouldInvalidate) {
      view->GetViewManager()->InvalidateView(view);
    }
  }

  if (aFlags & PAINT_FLUSH_LAYERS) {
    FrameLayerBuilder::InvalidateAllLayers(layerManager);
  }

  layerManager->SetUserData(&gLayerManagerLayerBuilder, oldBuilder);
}

uint32_t nsDisplayList::Count() const {
  uint32_t count = 0;
  for (nsDisplayItem* i = GetBottom(); i; i = i->GetAbove()) {
    ++count;
  }
  return count;
}

nsDisplayItem* nsDisplayList::RemoveBottom() {
  nsDisplayItem* item = mSentinel.mAbove;
  if (!item)
    return nullptr;
  mSentinel.mAbove = item->mAbove;
  if (item == mTop) {
    // must have been the only item
    mTop = &mSentinel;
  }
  item->mAbove = nullptr;
  return item;
}

void nsDisplayList::DeleteAll() {
  nsDisplayItem* item;
  while ((item = RemoveBottom()) != nullptr) {
    item->~nsDisplayItem();
  }
}

static bool
GetMouseThrough(const nsIFrame* aFrame)
{
  if (!aFrame->IsBoxFrame())
    return false;

  const nsIFrame* frame = aFrame;
  while (frame) {
    if (frame->GetStateBits() & NS_FRAME_MOUSE_THROUGH_ALWAYS) {
      return true;
    } else if (frame->GetStateBits() & NS_FRAME_MOUSE_THROUGH_NEVER) {
      return false;
    }
    frame = frame->GetParentBox();
  }
  return false;
}

static bool
IsFrameReceivingPointerEvents(nsIFrame* aFrame)
{
  nsSubDocumentFrame* frame = do_QueryFrame(aFrame);
  if (frame && frame->PassPointerEventsToChildren()) {
    return true;
  }
  return NS_STYLE_POINTER_EVENTS_NONE !=
    aFrame->StyleVisibility()->GetEffectivePointerEvents(aFrame);
}

// A list of frames, and their z depth. Used for sorting
// the results of hit testing.
struct FramesWithDepth
{
  FramesWithDepth(float aDepth) :
    mDepth(aDepth)
  {}

  bool operator<(const FramesWithDepth& aOther) const {
    if (mDepth != aOther.mDepth) {
      // We want to sort so that the shallowest item (highest depth value) is first
      return mDepth > aOther.mDepth;
    }
    return this < &aOther;
  }
  bool operator==(const FramesWithDepth& aOther) const {
    return this == &aOther;
  }

  float mDepth;
  nsTArray<nsIFrame*> mFrames;
};

// Sort the frames by depth and then moves all the contained frames to the destination
void FlushFramesArray(nsTArray<FramesWithDepth>& aSource, nsTArray<nsIFrame*>* aDest)
{
  if (aSource.IsEmpty()) {
    return;
  }
  aSource.Sort();
  uint32_t length = aSource.Length();
  for (uint32_t i = 0; i < length; i++) {
    aDest->MoveElementsFrom(aSource[i].mFrames);
  }
  aSource.Clear();
}

void nsDisplayList::HitTest(nsDisplayListBuilder* aBuilder, const nsRect& aRect,
                            nsDisplayItem::HitTestState* aState,
                            nsTArray<nsIFrame*> *aOutFrames) const {
  int32_t itemBufferStart = aState->mItemBuffer.Length();
  nsDisplayItem* item;
  for (item = GetBottom(); item; item = item->GetAbove()) {
    aState->mItemBuffer.AppendElement(item);
  }
  nsAutoTArray<FramesWithDepth, 16> temp;
  for (int32_t i = aState->mItemBuffer.Length() - 1; i >= itemBufferStart; --i) {
    // Pop element off the end of the buffer. We want to shorten the buffer
    // so that recursive calls to HitTest have more buffer space.
    item = aState->mItemBuffer[i];
    aState->mItemBuffer.SetLength(i);

    bool snap;
    nsRect r = item->GetBounds(aBuilder, &snap).Intersect(aRect);
    if (item->GetClip().MayIntersect(r)) {
      nsAutoTArray<nsIFrame*, 16> outFrames;
      item->HitTest(aBuilder, aRect, aState, &outFrames);

      // For 3d transforms with preserve-3d we add hit frames into the temp list
      // so we can sort them later, otherwise we add them directly to the output list.
      nsTArray<nsIFrame*> *writeFrames = aOutFrames;
      if (item->GetType() == nsDisplayItem::TYPE_TRANSFORM &&
          item->Frame()->Preserves3D()) {
        if (outFrames.Length()) {
          nsDisplayTransform *transform = static_cast<nsDisplayTransform*>(item);
          nsPoint point = aRect.TopLeft();
          // A 1x1 rect means a point, otherwise use the center of the rect
          if (aRect.width != 1 || aRect.height != 1) {
            point = aRect.Center();
          }
          temp.AppendElement(FramesWithDepth(transform->GetHitDepthAtPoint(aBuilder, point)));
          writeFrames = &temp[temp.Length() - 1].mFrames;
        }
      } else {
        // We may have just finished a run of consecutive preserve-3d transforms,
        // so flush these into the destination array before processing our frame list.
        FlushFramesArray(temp, aOutFrames);
      }

      for (uint32_t j = 0; j < outFrames.Length(); j++) {
        nsIFrame *f = outFrames.ElementAt(j);
        // Handle the XUL 'mousethrough' feature and 'pointer-events'.
        if (!GetMouseThrough(f) && IsFrameReceivingPointerEvents(f)) {
          writeFrames->AppendElement(f);
        }
      }
    }
  }
  // Clear any remaining preserve-3d transforms.
  FlushFramesArray(temp, aOutFrames);
  NS_ASSERTION(aState->mItemBuffer.Length() == uint32_t(itemBufferStart),
               "How did we forget to pop some elements?");
}

static void Sort(nsDisplayList* aList, int32_t aCount, nsDisplayList::SortLEQ aCmp,
                 void* aClosure) {
  if (aCount < 2)
    return;

  nsDisplayList list1;
  nsDisplayList list2;
  int i;
  int32_t half = aCount/2;
  bool sorted = true;
  nsDisplayItem* prev = nullptr;
  for (i = 0; i < aCount; ++i) {
    nsDisplayItem* item = aList->RemoveBottom();
    (i < half ? &list1 : &list2)->AppendToTop(item);
    if (sorted && prev && !aCmp(prev, item, aClosure)) {
      sorted = false;
    }
    prev = item;
  }
  if (sorted) {
    aList->AppendToTop(&list1);
    aList->AppendToTop(&list2);
    return;
  }

  Sort(&list1, half, aCmp, aClosure);
  Sort(&list2, aCount - half, aCmp, aClosure);

  for (i = 0; i < aCount; ++i) {
    if (list1.GetBottom() &&
        (!list2.GetBottom() ||
         aCmp(list1.GetBottom(), list2.GetBottom(), aClosure))) {
      aList->AppendToTop(list1.RemoveBottom());
    } else {
      aList->AppendToTop(list2.RemoveBottom());
    }
  }
}

static nsIContent* FindContentInDocument(nsDisplayItem* aItem, nsIDocument* aDoc) {
  nsIFrame* f = aItem->Frame();
  while (f) {
    nsPresContext* pc = f->PresContext();
    if (pc->Document() == aDoc) {
      return f->GetContent();
    }
    f = nsLayoutUtils::GetCrossDocParentFrame(pc->PresShell()->GetRootFrame());
  }
  return nullptr;
}

static bool IsContentLEQ(nsDisplayItem* aItem1, nsDisplayItem* aItem2,
                         void* aClosure) {
  nsIContent* commonAncestor = static_cast<nsIContent*>(aClosure);
  // It's possible that the nsIContent for aItem1 or aItem2 is in a subdocument
  // of commonAncestor, because display items for subdocuments have been
  // mixed into the same list. Ensure that we're looking at content
  // in commonAncestor's document.
  nsIDocument* commonAncestorDoc = commonAncestor->OwnerDoc();
  nsIContent* content1 = FindContentInDocument(aItem1, commonAncestorDoc);
  nsIContent* content2 = FindContentInDocument(aItem2, commonAncestorDoc);
  if (!content1 || !content2) {
    NS_ERROR("Document trees are mixed up!");
    // Something weird going on
    return true;
  }
  return nsLayoutUtils::CompareTreePosition(content1, content2, commonAncestor) <= 0;
}

static bool IsZOrderLEQ(nsDisplayItem* aItem1, nsDisplayItem* aItem2,
                        void* aClosure) {
  // Note that we can't just take the difference of the two
  // z-indices here, because that might overflow a 32-bit int.
  int32_t index1 = nsLayoutUtils::GetZIndex(aItem1->Frame());
  int32_t index2 = nsLayoutUtils::GetZIndex(aItem2->Frame());
  return index1 <= index2;
}

void nsDisplayList::SortByZOrder(nsDisplayListBuilder* aBuilder,
                                 nsIContent* aCommonAncestor) {
  Sort(aBuilder, IsZOrderLEQ, aCommonAncestor);
}

void nsDisplayList::SortByContentOrder(nsDisplayListBuilder* aBuilder,
                                       nsIContent* aCommonAncestor) {
  Sort(aBuilder, IsContentLEQ, aCommonAncestor);
}

void nsDisplayList::Sort(nsDisplayListBuilder* aBuilder,
                         SortLEQ aCmp, void* aClosure) {
  ::Sort(this, Count(), aCmp, aClosure);
}

void
nsDisplayItem::AddInvalidRegionForSyncDecodeBackgroundImages(
  nsDisplayListBuilder* aBuilder,
  const nsDisplayItemGeometry* aGeometry,
  nsRegion* aInvalidRegion)
{
  if (aBuilder->ShouldSyncDecodeImages()) {
    if (!nsCSSRendering::AreAllBackgroundImagesDecodedForFrame(mFrame)) {
      bool snap;
      aInvalidRegion->Or(*aInvalidRegion, GetBounds(aBuilder, &snap));
    }
  }
}

/* static */ bool
nsDisplayItem::ForceActiveLayers()
{
  static bool sForce = false;
  static bool sForceCached = false;

  if (!sForceCached) {
    Preferences::AddBoolVarCache(&sForce, "layers.force-active", false);
    sForceCached = true;
  }

  return sForce;
}

/* static */ int32_t
nsDisplayItem::MaxActiveLayers()
{
  static int32_t sMaxLayers = false;
  static bool sMaxLayersCached = false;

  if (!sMaxLayersCached) {
    Preferences::AddIntVarCache(&sMaxLayers, "layers.max-active", -1);
    sMaxLayersCached = true;
  }

  return sMaxLayers;
}

bool
nsDisplayItem::RecomputeVisibility(nsDisplayListBuilder* aBuilder,
                                   nsRegion* aVisibleRegion) {
  nsRect bounds = GetClippedBounds(aBuilder);

  nsRegion itemVisible;
  itemVisible.And(*aVisibleRegion, bounds);
  mVisibleRect = itemVisible.GetBounds();

  // When we recompute visibility within layers we don't need to
  // expand the visible region for content behind plugins (the plugin
  // is not in the layer).
  if (!ComputeVisibility(aBuilder, aVisibleRegion, nsRect()))
    return false;

  nsRegion opaque = TreatAsOpaque(this, aBuilder);
  aBuilder->SubtractFromVisibleRegion(aVisibleRegion, opaque);
  return true;
}

nsRect
nsDisplayItem::GetClippedBounds(nsDisplayListBuilder* aBuilder)
{
  bool snap;
  nsRect r = GetBounds(aBuilder, &snap);
  return GetClip().ApplyNonRoundedIntersection(r);
}

nsRect
nsDisplaySolidColor::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap)
{
  *aSnap = true;
  return mBounds;
}

void
nsDisplaySolidColor::Paint(nsDisplayListBuilder* aBuilder,
                           nsRenderingContext* aCtx)
{
  aCtx->SetColor(mColor);
  aCtx->FillRect(mVisibleRect);
}

#ifdef MOZ_DUMP_PAINTING
void
nsDisplaySolidColor::WriteDebugInfo(nsACString& aTo)
{
  aTo += nsPrintfCString(" (rgba %d,%d,%d,%d)",
                 NS_GET_R(mColor), NS_GET_G(mColor),
                 NS_GET_B(mColor), NS_GET_A(mColor));
}
#endif

static void
RegisterThemeGeometry(nsDisplayListBuilder* aBuilder, nsIFrame* aFrame)
{
  nsIFrame* displayRoot = nsLayoutUtils::GetDisplayRootFrame(aFrame);

  for (nsIFrame* f = aFrame; f; f = f->GetParent()) {
    // Bail out if we're in a transformed subtree
    if (f->IsTransformed())
      return;
    // Bail out if we're not in the displayRoot's document
    if (!f->GetParent() && f != displayRoot)
      return;
  }

  nsRect borderBox(aFrame->GetOffsetTo(displayRoot), aFrame->GetSize());
  aBuilder->RegisterThemeGeometry(aFrame->StyleDisplay()->mAppearance,
      borderBox.ToNearestPixels(aFrame->PresContext()->AppUnitsPerDevPixel()));
}

nsDisplayBackgroundImage::nsDisplayBackgroundImage(nsDisplayListBuilder* aBuilder,
                                                   nsIFrame* aFrame,
                                                   uint32_t aLayer,
                                                   const nsStyleBackground* aBackgroundStyle)
  : nsDisplayImageContainer(aBuilder, aFrame)
  , mBackgroundStyle(aBackgroundStyle)
  , mLayer(aLayer)
{
  MOZ_COUNT_CTOR(nsDisplayBackgroundImage);

  mBounds = GetBoundsInternal(aBuilder);
}

nsDisplayBackgroundImage::~nsDisplayBackgroundImage()
{
#ifdef NS_BUILD_REFCNT_LOGGING
  MOZ_COUNT_DTOR(nsDisplayBackgroundImage);
#endif
}

static nsStyleContext* GetBackgroundStyleContext(nsIFrame* aFrame)
{
  nsStyleContext *sc;
  if (!nsCSSRendering::FindBackground(aFrame, &sc)) {
    // We don't want to bail out if moz-appearance is set on a root
    // node. If it has a parent content node, bail because it's not
    // a root, other wise keep going in order to let the theme stuff
    // draw the background. The canvas really should be drawing the
    // bg, but there's no way to hook that up via css.
    if (!aFrame->StyleDisplay()->mAppearance) {
      return nullptr;
    }

    nsIContent* content = aFrame->GetContent();
    if (!content || content->GetParent()) {
      return nullptr;
    }

    sc = aFrame->StyleContext();
  }
  return sc;
}

/*static*/ bool
nsDisplayBackgroundImage::AppendBackgroundItemsToTop(nsDisplayListBuilder* aBuilder,
                                                     nsIFrame* aFrame,
                                                     nsDisplayList* aList)
{
  nsStyleContext* bgSC = nullptr;
  const nsStyleBackground* bg = nullptr;
  nsPresContext* presContext = aFrame->PresContext();
  bool isThemed = aFrame->IsThemed();
  if (!isThemed) {
    bgSC = GetBackgroundStyleContext(aFrame);
    if (bgSC) {
      bg = bgSC->StyleBackground();
    }
  }

  bool drawBackgroundColor = false;
  nscolor color;
  if (!nsCSSRendering::IsCanvasFrame(aFrame) && bg) {
    bool drawBackgroundImage;
    color =
      nsCSSRendering::DetermineBackgroundColor(presContext, bgSC, aFrame,
                                               drawBackgroundImage, drawBackgroundColor);
  }

  // An auxiliary list is necessary in case we have background blending; if that
  // is the case, background items need to be wrapped by a blend container to
  // isolate blending to the background
  nsDisplayList bgItemList;
  // Even if we don't actually have a background color to paint, we may still need
  // to create an item for hit testing.
  if ((drawBackgroundColor && color != NS_RGBA(0,0,0,0)) ||
      aBuilder->IsForEventDelivery()) {
    bgItemList.AppendNewToTop(
        new (aBuilder) nsDisplayBackgroundColor(aBuilder, aFrame, bg,
                                                drawBackgroundColor ? color : NS_RGBA(0, 0, 0, 0)));
  }

  if (isThemed) {
    nsDisplayThemedBackground* bgItem =
      new (aBuilder) nsDisplayThemedBackground(aBuilder, aFrame);
    bgItemList.AppendNewToTop(bgItem);
    aList->AppendToTop(&bgItemList);
    return true;
  }

  if (!bg) {
    aList->AppendToTop(&bgItemList);
    return false;
  }
 
  bool needBlendContainer = false;

  // Passing bg == nullptr in this macro will result in one iteration with
  // i = 0.
  NS_FOR_VISIBLE_BACKGROUND_LAYERS_BACK_TO_FRONT(i, bg) {
    if (bg->mLayers[i].mImage.IsEmpty()) {
      continue;
    }

    if (bg->mLayers[i].mBlendMode != NS_STYLE_BLEND_NORMAL) {
      needBlendContainer = true;
    }

    nsDisplayBackgroundImage* bgItem =
      new (aBuilder) nsDisplayBackgroundImage(aBuilder, aFrame, i, bg);
    bgItemList.AppendNewToTop(bgItem);
  }

  if (needBlendContainer) {
    bgItemList.AppendNewToTop(
      new (aBuilder) nsDisplayBlendContainer(aBuilder, aFrame, &bgItemList));
  }

  aList->AppendToTop(&bgItemList);
  return false;
}

// Check that the rounded border of aFrame, added to aToReferenceFrame,
// intersects aRect.  Assumes that the unrounded border has already
// been checked for intersection.
static bool
RoundedBorderIntersectsRect(nsIFrame* aFrame,
                            const nsPoint& aFrameToReferenceFrame,
                            const nsRect& aTestRect)
{
  if (!nsRect(aFrameToReferenceFrame, aFrame->GetSize()).Intersects(aTestRect))
    return false;

  nscoord radii[8];
  return !aFrame->GetBorderRadii(radii) ||
         nsLayoutUtils::RoundedRectIntersectsRect(nsRect(aFrameToReferenceFrame,
                                                  aFrame->GetSize()),
                                                  radii, aTestRect);
}

// Returns TRUE if aContainedRect is guaranteed to be contained in
// the rounded rect defined by aRoundedRect and aRadii. Complex cases are
// handled conservatively by returning FALSE in some situations where
// a more thorough analysis could return TRUE.
//
// See also RoundedRectIntersectsRect.
static bool RoundedRectContainsRect(const nsRect& aRoundedRect,
                                    const nscoord aRadii[8],
                                    const nsRect& aContainedRect) {
  nsRegion rgn = nsLayoutUtils::RoundedRectIntersectRect(aRoundedRect, aRadii, aContainedRect);
  return rgn.Contains(aContainedRect);
}

bool
nsDisplayBackgroundImage::IsSingleFixedPositionImage(nsDisplayListBuilder* aBuilder,
                                                     const nsRect& aClipRect,
                                                     gfxRect* aDestRect)
{
  if (!mBackgroundStyle)
    return false;

  if (mBackgroundStyle->mLayers.Length() != 1)
    return false;

  nsPresContext* presContext = mFrame->PresContext();
  uint32_t flags = aBuilder->GetBackgroundPaintFlags();
  nsRect borderArea = nsRect(ToReferenceFrame(), mFrame->GetSize());
  const nsStyleBackground::Layer &layer = mBackgroundStyle->mLayers[mLayer];

  if (layer.mAttachment != NS_STYLE_BG_ATTACHMENT_FIXED)
    return false;

  nsBackgroundLayerState state =
    nsCSSRendering::PrepareBackgroundLayer(presContext,
                                           mFrame,
                                           flags,
                                           borderArea,
                                           aClipRect,
                                           *mBackgroundStyle,
                                           layer);

  nsImageRenderer* imageRenderer = &state.mImageRenderer;
  // We only care about images here, not gradients.
  if (!imageRenderer->IsRasterImage())
    return false;

  int32_t appUnitsPerDevPixel = presContext->AppUnitsPerDevPixel();
  *aDestRect = nsLayoutUtils::RectToGfxRect(state.mFillArea, appUnitsPerDevPixel);

  return true;
}

bool
nsDisplayBackgroundImage::TryOptimizeToImageLayer(LayerManager* aManager,
                                                  nsDisplayListBuilder* aBuilder)
{
  if (!mBackgroundStyle)
    return false;

  nsPresContext* presContext = mFrame->PresContext();
  uint32_t flags = aBuilder->GetBackgroundPaintFlags();
  nsRect borderArea = nsRect(ToReferenceFrame(), mFrame->GetSize());
  const nsStyleBackground::Layer &layer = mBackgroundStyle->mLayers[mLayer];

  if (layer.mClip != NS_STYLE_BG_CLIP_BORDER) {
    return false;
  }
  nscoord radii[8];
  if (mFrame->GetBorderRadii(radii)) {
    return false;
  }

  nsBackgroundLayerState state =
    nsCSSRendering::PrepareBackgroundLayer(presContext,
                                           mFrame,
                                           flags,
                                           borderArea,
                                           borderArea,
                                           *mBackgroundStyle,
                                           layer);

  nsImageRenderer* imageRenderer = &state.mImageRenderer;
  // We only care about images here, not gradients.
  if (!imageRenderer->IsRasterImage())
    return false;

  nsRefPtr<ImageContainer> imageContainer = imageRenderer->GetContainer(aManager);
  // Image is not ready to be made into a layer yet
  if (!imageContainer)
    return false;

  // We currently can't handle tiled or partial backgrounds.
  if (!state.mDestArea.IsEqualEdges(state.mFillArea)) {
    return false;
  }

  // XXX Ignoring state.mAnchor. ImageLayer drawing snaps mDestArea edges to
  // layer pixel boundaries. This should be OK for now.

  int32_t appUnitsPerDevPixel = presContext->AppUnitsPerDevPixel();
  mDestRect = nsLayoutUtils::RectToGfxRect(state.mDestArea, appUnitsPerDevPixel);
  mImageContainer = imageContainer;

  // Ok, we can turn this into a layer if needed.
  return true;
}

already_AddRefed<ImageContainer>
nsDisplayBackgroundImage::GetContainer(LayerManager* aManager,
                                       nsDisplayListBuilder *aBuilder)
{
  if (!TryOptimizeToImageLayer(aManager, aBuilder)) {
    return nullptr;
  }

  nsRefPtr<ImageContainer> container = mImageContainer;

  return container.forget();
}

LayerState
nsDisplayBackgroundImage::GetLayerState(nsDisplayListBuilder* aBuilder,
                                        LayerManager* aManager,
                                        const ContainerLayerParameters& aParameters)
{
  bool animated = false;
  if (mBackgroundStyle) {
    const nsStyleBackground::Layer &layer = mBackgroundStyle->mLayers[mLayer];
    const nsStyleImage* image = &layer.mImage;
    if (image->GetType() == eStyleImageType_Image) {
      imgIRequest* imgreq = image->GetImageData();
      nsCOMPtr<imgIContainer> image;
      if (NS_SUCCEEDED(imgreq->GetImage(getter_AddRefs(image))) && image) {
        if (NS_FAILED(image->GetAnimated(&animated))) {
          animated = false;
        }
      }
    }
  }

  if (!animated ||
      !nsLayoutUtils::AnimatedImageLayersEnabled()) {
    if (!aManager->IsCompositingCheap() ||
        !nsLayoutUtils::GPUImageScalingEnabled()) {
      return LAYER_NONE;
    }
  }

  if (!TryOptimizeToImageLayer(aManager, aBuilder)) {
    return LAYER_NONE;
  }

  if (!animated) {
    mozilla::gfx::IntSize imageSize = mImageContainer->GetCurrentSize();
    NS_ASSERTION(imageSize.width != 0 && imageSize.height != 0, "Invalid image size!");

    gfxRect destRect = mDestRect;

    destRect.width *= aParameters.mXScale;
    destRect.height *= aParameters.mYScale;

    // Calculate the scaling factor for the frame.
    gfxSize scale = gfxSize(destRect.width / imageSize.width, destRect.height / imageSize.height);

    // If we are not scaling at all, no point in separating this into a layer.
    if (scale.width == 1.0f && scale.height == 1.0f) {
      return LAYER_NONE;
    }

    // If the target size is pretty small, no point in using a layer.
    if (destRect.width * destRect.height < 64 * 64) {
      return LAYER_NONE;
    }
  }

  return LAYER_ACTIVE;
}

already_AddRefed<Layer>
nsDisplayBackgroundImage::BuildLayer(nsDisplayListBuilder* aBuilder,
                                     LayerManager* aManager,
                                     const ContainerLayerParameters& aParameters)
{
  nsRefPtr<ImageLayer> layer = static_cast<ImageLayer*>
    (aManager->GetLayerBuilder()->GetLeafLayerFor(aBuilder, this));
  if (!layer) {
    layer = aManager->CreateImageLayer();
    if (!layer)
      return nullptr;
  }
  layer->SetContainer(mImageContainer);
  ConfigureLayer(layer, aParameters.mOffset);
  return layer.forget();
}

void
nsDisplayBackgroundImage::ConfigureLayer(ImageLayer* aLayer, const nsIntPoint& aOffset)
{
  aLayer->SetFilter(nsLayoutUtils::GetGraphicsFilterForFrame(mFrame));

  mozilla::gfx::IntSize imageSize = mImageContainer->GetCurrentSize();
  NS_ASSERTION(imageSize.width != 0 && imageSize.height != 0, "Invalid image size!");

  gfxPoint p = mDestRect.TopLeft() + aOffset;
  gfx::Matrix transform;
  transform.Translate(p.x, p.y);
  transform.Scale(mDestRect.width/imageSize.width,
                  mDestRect.height/imageSize.height);
  aLayer->SetBaseTransform(gfx::Matrix4x4::From2D(transform));
  aLayer->SetVisibleRegion(nsIntRect(0, 0, imageSize.width, imageSize.height));
}

void
nsDisplayBackgroundImage::HitTest(nsDisplayListBuilder* aBuilder,
                                  const nsRect& aRect,
                                  HitTestState* aState,
                                  nsTArray<nsIFrame*> *aOutFrames)
{
  if (RoundedBorderIntersectsRect(mFrame, ToReferenceFrame(), aRect)) {
    aOutFrames->AppendElement(mFrame);
  }
}

bool
nsDisplayBackgroundImage::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                            nsRegion* aVisibleRegion,
                                            const nsRect& aAllowVisibleRegionExpansion)
{
  if (!nsDisplayItem::ComputeVisibility(aBuilder, aVisibleRegion,
                                        aAllowVisibleRegionExpansion)) {
    return false;
  }

  // Return false if the background was propagated away from this
  // frame. We don't want this display item to show up and confuse
  // anything.
  return mBackgroundStyle;
}

/* static */ nsRegion
nsDisplayBackgroundImage::GetInsideClipRegion(nsDisplayItem* aItem,
                                              nsPresContext* aPresContext,
                                              uint8_t aClip, const nsRect& aRect,
                                              bool* aSnap)
{
  nsRegion result;
  if (aRect.IsEmpty())
    return result;

  nsIFrame *frame = aItem->Frame();

  nscoord radii[8];
  nsRect clipRect;
  bool haveRadii;
  switch (aClip) {
  case NS_STYLE_BG_CLIP_BORDER:
    haveRadii = frame->GetBorderRadii(radii);
    clipRect = nsRect(aItem->ToReferenceFrame(), frame->GetSize());
    break;
  case NS_STYLE_BG_CLIP_PADDING:
    haveRadii = frame->GetPaddingBoxBorderRadii(radii);
    clipRect = frame->GetPaddingRect() - frame->GetPosition() + aItem->ToReferenceFrame();
    break;
  case NS_STYLE_BG_CLIP_CONTENT:
    haveRadii = frame->GetContentBoxBorderRadii(radii);
    clipRect = frame->GetContentRect() - frame->GetPosition() + aItem->ToReferenceFrame();
    break;
  default:
    NS_NOTREACHED("Unknown clip type");
    return result;
  }

  if (haveRadii) {
    *aSnap = false;
    result = nsLayoutUtils::RoundedRectIntersectRect(clipRect, radii, aRect);
  } else {
    result = clipRect.Intersect(aRect);
  }
  return result;
}

nsRegion
nsDisplayBackgroundImage::GetOpaqueRegion(nsDisplayListBuilder* aBuilder,
                                          bool* aSnap) {
  nsRegion result;
  *aSnap = false;

  if (!mBackgroundStyle)
    return result;


  *aSnap = true;

  // For policies other than EACH_BOX, don't try to optimize here, since
  // this could easily lead to O(N^2) behavior inside InlineBackgroundData,
  // which expects frames to be sent to it in content order, not reverse
  // content order which we'll produce here.
  // Of course, if there's only one frame in the flow, it doesn't matter.
  if (mBackgroundStyle->mBackgroundInlinePolicy == NS_STYLE_BG_INLINE_POLICY_EACH_BOX ||
      (!mFrame->GetPrevContinuation() && !mFrame->GetNextContinuation())) {
    const nsStyleBackground::Layer& layer = mBackgroundStyle->mLayers[mLayer];
    if (layer.mImage.IsOpaque() && layer.mBlendMode == NS_STYLE_BLEND_NORMAL) {
      nsPresContext* presContext = mFrame->PresContext();
      result = GetInsideClipRegion(this, presContext, layer.mClip, mBounds, aSnap);
    }
  }

  return result;
}

bool
nsDisplayBackgroundImage::IsUniform(nsDisplayListBuilder* aBuilder, nscolor* aColor) {
  if (!mBackgroundStyle) {
    *aColor = NS_RGBA(0,0,0,0);
    return true;
  }
  return false;
}

bool
nsDisplayBackgroundImage::IsVaryingRelativeToMovingFrame(nsDisplayListBuilder* aBuilder,
                                                         nsIFrame* aFrame)
{
  if (!mBackgroundStyle)
    return false;
  if (!mBackgroundStyle->HasFixedBackground())
    return false;

  // If aFrame is mFrame or an ancestor in this document, and aFrame is
  // not the viewport frame, then moving aFrame will move mFrame
  // relative to the viewport, so our fixed-pos background will change.
  return aFrame->GetParent() &&
    (aFrame == mFrame ||
     nsLayoutUtils::IsProperAncestorFrame(aFrame, mFrame));
}

nsRect
nsDisplayBackgroundImage::GetPositioningArea()
{
  if (!mBackgroundStyle) {
    return nsRect();
  }
  nsIFrame* attachedToFrame;
  return nsCSSRendering::ComputeBackgroundPositioningArea(
      mFrame->PresContext(), mFrame,
      nsRect(ToReferenceFrame(), mFrame->GetSize()),
      *mBackgroundStyle, mBackgroundStyle->mLayers[mLayer],
      &attachedToFrame) + ToReferenceFrame();
}

bool
nsDisplayBackgroundImage::RenderingMightDependOnPositioningAreaSizeChange()
{
  if (!mBackgroundStyle)
    return false;

  nscoord radii[8];
  if (mFrame->GetBorderRadii(radii)) {
    // A change in the size of the positioning area might change the position
    // of the rounded corners.
    return true;
  }

  const nsStyleBackground::Layer &layer = mBackgroundStyle->mLayers[mLayer];
  if (layer.RenderingMightDependOnPositioningAreaSizeChange()) {
    return true;
  }
  return false;
}

static void CheckForBorderItem(nsDisplayItem *aItem, uint32_t& aFlags)
{
  nsDisplayItem* nextItem = aItem->GetAbove();
  while (nextItem && nextItem->GetType() == nsDisplayItem::TYPE_BACKGROUND) {
    nextItem = nextItem->GetAbove();
  }
  if (nextItem && 
      nextItem->Frame() == aItem->Frame() &&
      nextItem->GetType() == nsDisplayItem::TYPE_BORDER) {
    aFlags |= nsCSSRendering::PAINTBG_WILL_PAINT_BORDER;
  }
}

void
nsDisplayBackgroundImage::Paint(nsDisplayListBuilder* aBuilder,
                                nsRenderingContext* aCtx) {
  PaintInternal(aBuilder, aCtx, mVisibleRect, nullptr);
}

void
nsDisplayBackgroundImage::PaintInternal(nsDisplayListBuilder* aBuilder,
                                        nsRenderingContext* aCtx, const nsRect& aBounds,
                                        nsRect* aClipRect) {
  nsPoint offset = ToReferenceFrame();
  uint32_t flags = aBuilder->GetBackgroundPaintFlags();
  CheckForBorderItem(this, flags);

  nsCSSRendering::PaintBackground(mFrame->PresContext(), *aCtx, mFrame,
                                  aBounds,
                                  nsRect(offset, mFrame->GetSize()),
                                  flags, aClipRect, mLayer);

}

void nsDisplayBackgroundImage::ComputeInvalidationRegion(nsDisplayListBuilder* aBuilder,
                                                         const nsDisplayItemGeometry* aGeometry,
                                                         nsRegion* aInvalidRegion)
{
  if (!mBackgroundStyle) {
    return;
  }

  const nsDisplayBackgroundGeometry* geometry = static_cast<const nsDisplayBackgroundGeometry*>(aGeometry);

  bool snap;
  nsRect bounds = GetBounds(aBuilder, &snap);
  nsRect positioningArea = GetPositioningArea();
  if (positioningArea.TopLeft() != geometry->mPositioningArea.TopLeft() ||
      (positioningArea.Size() != geometry->mPositioningArea.Size() &&
       RenderingMightDependOnPositioningAreaSizeChange())) {
    // Positioning area changed in a way that could cause everything to change,
    // so invalidate everything (both old and new painting areas).
    aInvalidRegion->Or(bounds, geometry->mBounds);
    return;
  }
  if (aBuilder->ShouldSyncDecodeImages()) {
    if (mBackgroundStyle &&
        !nsCSSRendering::IsBackgroundImageDecodedForStyleContextAndLayer(mBackgroundStyle, mLayer)) {
      aInvalidRegion->Or(*aInvalidRegion, bounds);
    }
  }
  if (!bounds.IsEqualInterior(geometry->mBounds)) {
    // Positioning area is unchanged, so invalidate just the change in the
    // painting area.
    aInvalidRegion->Xor(bounds, geometry->mBounds);
  }
}

nsRect
nsDisplayBackgroundImage::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap) {
  *aSnap = true;
  return mBounds;
}

nsRect
nsDisplayBackgroundImage::GetBoundsInternal(nsDisplayListBuilder* aBuilder) {
  nsPresContext* presContext = mFrame->PresContext();

  if (!mBackgroundStyle) {
    return nsRect();
  }

  nsRect borderBox = nsRect(ToReferenceFrame(), mFrame->GetSize());
  nsRect clipRect = borderBox;
  if (mFrame->GetType() == nsGkAtoms::canvasFrame) {
    nsCanvasFrame* frame = static_cast<nsCanvasFrame*>(mFrame);
    clipRect = frame->CanvasArea() + ToReferenceFrame();
  }
  const nsStyleBackground::Layer& layer = mBackgroundStyle->mLayers[mLayer];
  return nsCSSRendering::GetBackgroundLayerRect(presContext, mFrame,
                                                borderBox, clipRect,
                                                *mBackgroundStyle, layer,
                                                aBuilder->GetBackgroundPaintFlags());
}

uint32_t
nsDisplayBackgroundImage::GetPerFrameKey()
{
  return (mLayer << nsDisplayItem::TYPE_BITS) |
    nsDisplayItem::GetPerFrameKey();
}

nsDisplayThemedBackground::nsDisplayThemedBackground(nsDisplayListBuilder* aBuilder,
                                                     nsIFrame* aFrame)
  : nsDisplayItem(aBuilder, aFrame)
{
  MOZ_COUNT_CTOR(nsDisplayThemedBackground);

  const nsStyleDisplay* disp = mFrame->StyleDisplay();
  mAppearance = disp->mAppearance;
  mFrame->IsThemed(disp, &mThemeTransparency);

  // Perform necessary RegisterThemeGeometry
  switch (disp->mAppearance) {
    case NS_THEME_MOZ_MAC_UNIFIED_TOOLBAR:
    case NS_THEME_TOOLBAR:
    case NS_THEME_WINDOW_TITLEBAR:
    case NS_THEME_WINDOW_BUTTON_BOX:
    case NS_THEME_MOZ_MAC_FULLSCREEN_BUTTON:
    case NS_THEME_WINDOW_BUTTON_BOX_MAXIMIZED:
      RegisterThemeGeometry(aBuilder, aFrame);
      break;
    case NS_THEME_WIN_BORDERLESS_GLASS:
    case NS_THEME_WIN_GLASS:
      aBuilder->SetGlassDisplayItem(this);
      break;
  }

  mBounds = GetBoundsInternal();
}

nsDisplayThemedBackground::~nsDisplayThemedBackground()
{
#ifdef NS_BUILD_REFCNT_LOGGING
  MOZ_COUNT_DTOR(nsDisplayThemedBackground);
#endif
}

#ifdef MOZ_DUMP_PAINTING
void
nsDisplayThemedBackground::WriteDebugInfo(nsACString& aTo)
{
  aTo += nsPrintfCString(" (themed, appearance:%d)", mAppearance);
}
#endif

void
nsDisplayThemedBackground::HitTest(nsDisplayListBuilder* aBuilder,
                                  const nsRect& aRect,
                                  HitTestState* aState,
                                  nsTArray<nsIFrame*> *aOutFrames)
{
  // Assume that any point in our border rect is a hit.
  if (nsRect(ToReferenceFrame(), mFrame->GetSize()).Intersects(aRect)) {
    aOutFrames->AppendElement(mFrame);
  }
}

nsRegion
nsDisplayThemedBackground::GetOpaqueRegion(nsDisplayListBuilder* aBuilder,
                                           bool* aSnap) {
  nsRegion result;
  *aSnap = false;

  if (mThemeTransparency == nsITheme::eOpaque) {
    result = nsRect(ToReferenceFrame(), mFrame->GetSize());
  }
  return result;
}

bool
nsDisplayThemedBackground::IsUniform(nsDisplayListBuilder* aBuilder, nscolor* aColor) {
  if (mAppearance == NS_THEME_WIN_BORDERLESS_GLASS ||
      mAppearance == NS_THEME_WIN_GLASS) {
    *aColor = NS_RGBA(0,0,0,0);
    return true;
  }
  return false;
}

nsRect
nsDisplayThemedBackground::GetPositioningArea()
{
  return nsRect(ToReferenceFrame(), mFrame->GetSize());
}

void
nsDisplayThemedBackground::Paint(nsDisplayListBuilder* aBuilder,
                                 nsRenderingContext* aCtx)
{
  PaintInternal(aBuilder, aCtx, mVisibleRect, nullptr);
}


void
nsDisplayThemedBackground::PaintInternal(nsDisplayListBuilder* aBuilder,
                                         nsRenderingContext* aCtx, const nsRect& aBounds,
                                         nsRect* aClipRect)
{
  // XXXzw this ignores aClipRect.
  nsPresContext* presContext = mFrame->PresContext();
  nsITheme *theme = presContext->GetTheme();
  nsRect borderArea(ToReferenceFrame(), mFrame->GetSize());
  nsRect drawing(borderArea);
  theme->GetWidgetOverflow(presContext->DeviceContext(), mFrame, mAppearance,
                           &drawing);
  drawing.IntersectRect(drawing, aBounds);
  theme->DrawWidgetBackground(aCtx, mFrame, mAppearance, borderArea, drawing);
}

bool nsDisplayThemedBackground::IsWindowActive()
{
  nsEventStates docState = mFrame->GetContent()->OwnerDoc()->GetDocumentState();
  return !docState.HasState(NS_DOCUMENT_STATE_WINDOW_INACTIVE);
}

void nsDisplayThemedBackground::ComputeInvalidationRegion(nsDisplayListBuilder* aBuilder,
                                                          const nsDisplayItemGeometry* aGeometry,
                                                          nsRegion* aInvalidRegion)
{
  const nsDisplayThemedBackgroundGeometry* geometry = static_cast<const nsDisplayThemedBackgroundGeometry*>(aGeometry);

  bool snap;
  nsRect bounds = GetBounds(aBuilder, &snap);
  nsRect positioningArea = GetPositioningArea();
  if (!positioningArea.IsEqualInterior(geometry->mPositioningArea)) {
    // Invalidate everything (both old and new painting areas).
    aInvalidRegion->Or(bounds, geometry->mBounds);
    return;
  }
  if (!bounds.IsEqualInterior(geometry->mBounds)) {
    // Positioning area is unchanged, so invalidate just the change in the
    // painting area.
    aInvalidRegion->Xor(bounds, geometry->mBounds);
  }
  nsITheme* theme = mFrame->PresContext()->GetTheme();
  if (theme->WidgetAppearanceDependsOnWindowFocus(mAppearance) &&
      IsWindowActive() != geometry->mWindowIsActive) {
    aInvalidRegion->Or(*aInvalidRegion, bounds);
  }
}

nsRect
nsDisplayThemedBackground::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap) {
  *aSnap = true;
  return mBounds;
}

nsRect
nsDisplayThemedBackground::GetBoundsInternal() {
  nsPresContext* presContext = mFrame->PresContext();

  nsRect r(nsPoint(0,0), mFrame->GetSize());
  presContext->GetTheme()->
      GetWidgetOverflow(presContext->DeviceContext(), mFrame,
                        mFrame->StyleDisplay()->mAppearance, &r);
#ifdef XP_MACOSX
  // Bug 748219
  r.Inflate(mFrame->PresContext()->AppUnitsPerDevPixel());
#endif

  return r + ToReferenceFrame();
}

void
nsDisplayBackgroundColor::Paint(nsDisplayListBuilder* aBuilder,
                                nsRenderingContext* aCtx) 
{
  if (mColor == NS_RGBA(0, 0, 0, 0)) {
    return;
  }

  nsPoint offset = ToReferenceFrame();
  uint32_t flags = aBuilder->GetBackgroundPaintFlags();
  CheckForBorderItem(this, flags);
  nsCSSRendering::PaintBackgroundColor(mFrame->PresContext(), *aCtx, mFrame,
                                       mVisibleRect,
                                       nsRect(offset, mFrame->GetSize()),
                                       flags);
}

nsRegion
nsDisplayBackgroundColor::GetOpaqueRegion(nsDisplayListBuilder* aBuilder,
                                          bool* aSnap) 
{
  if (NS_GET_A(mColor) != 255) {
    return nsRegion();
  }

  if (!mBackgroundStyle)
    return nsRegion();

  *aSnap = true;

  const nsStyleBackground::Layer& bottomLayer = mBackgroundStyle->BottomLayer();
  nsRect borderBox = nsRect(ToReferenceFrame(), mFrame->GetSize());
  nsPresContext* presContext = mFrame->PresContext();
  return nsDisplayBackgroundImage::GetInsideClipRegion(this, presContext, bottomLayer.mClip, borderBox, aSnap);
}

bool
nsDisplayBackgroundColor::IsUniform(nsDisplayListBuilder* aBuilder, nscolor* aColor) 
{
  *aColor = mColor;

  if (!mBackgroundStyle)
    return true;

  return (!nsLayoutUtils::HasNonZeroCorner(mFrame->StyleBorder()->mBorderRadius) &&
          mBackgroundStyle->BottomLayer().mClip == NS_STYLE_BG_CLIP_BORDER);
}

void
nsDisplayBackgroundColor::HitTest(nsDisplayListBuilder* aBuilder,
                                  const nsRect& aRect,
                                  HitTestState* aState,
                                  nsTArray<nsIFrame*> *aOutFrames)
{
  if (!RoundedBorderIntersectsRect(mFrame, ToReferenceFrame(), aRect)) {
    // aRect doesn't intersect our border-radius curve.
    return;
  }

  aOutFrames->AppendElement(mFrame);
}

#ifdef MOZ_DUMP_PAINTING
void
nsDisplayBackgroundColor::WriteDebugInfo(nsACString& aTo)
{
  aTo += nsPrintfCString(" (rgba %d,%d,%d,%d)", 
          NS_GET_R(mColor), NS_GET_G(mColor),
          NS_GET_B(mColor), NS_GET_A(mColor));
}
#endif

nsRect
nsDisplayOutline::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap) {
  *aSnap = false;
  return mFrame->GetVisualOverflowRectRelativeToSelf() + ToReferenceFrame();
}

void
nsDisplayOutline::Paint(nsDisplayListBuilder* aBuilder,
                        nsRenderingContext* aCtx) {
  // TODO join outlines together
  nsPoint offset = ToReferenceFrame();
  nsCSSRendering::PaintOutline(mFrame->PresContext(), *aCtx, mFrame,
                               mVisibleRect,
                               nsRect(offset, mFrame->GetSize()),
                               mFrame->StyleContext());
}

bool
nsDisplayOutline::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                    nsRegion* aVisibleRegion,
                                    const nsRect& aAllowVisibleRegionExpansion) {
  if (!nsDisplayItem::ComputeVisibility(aBuilder, aVisibleRegion,
                                        aAllowVisibleRegionExpansion)) {
    return false;
  }

  const nsStyleOutline* outline = mFrame->StyleOutline();
  nsRect borderBox(ToReferenceFrame(), mFrame->GetSize());
  if (borderBox.Contains(aVisibleRegion->GetBounds()) &&
      !nsLayoutUtils::HasNonZeroCorner(outline->mOutlineRadius)) {
    if (outline->mOutlineOffset >= 0) {
      // the visible region is entirely inside the border-rect, and the outline
      // isn't rendered inside the border-rect, so the outline is not visible
      return false;
    }
  }

  return true;
}

void
nsDisplayEventReceiver::HitTest(nsDisplayListBuilder* aBuilder,
                                const nsRect& aRect,
                                HitTestState* aState,
                                nsTArray<nsIFrame*> *aOutFrames)
{
  if (!RoundedBorderIntersectsRect(mFrame, ToReferenceFrame(), aRect)) {
    // aRect doesn't intersect our border-radius curve.
    return;
  }

  aOutFrames->AppendElement(mFrame);
}

void
nsDisplayLayerEventRegions::AddFrame(nsDisplayListBuilder* aBuilder,
                                     nsIFrame* aFrame)
{
  NS_ASSERTION(aBuilder->FindReferenceFrameFor(aFrame) == aBuilder->FindReferenceFrameFor(mFrame),
               "Reference frame mismatch");
  uint8_t pointerEvents = aFrame->StyleVisibility()->mPointerEvents;
  if (pointerEvents == NS_STYLE_POINTER_EVENTS_NONE) {
    return;
  }
  // XXX handle other pointerEvents values for SVG
  // XXX Do something clever here for the common case where the border box
  // is obviously entirely inside mHitRegion.
  nsRect borderBox(aBuilder->ToReferenceFrame(aFrame), aFrame->GetSize());
  const DisplayItemClip* clip = aBuilder->ClipState().GetCurrentCombinedClip(aBuilder);
  bool borderBoxHasRoundedCorners =
    nsLayoutUtils::HasNonZeroCorner(aFrame->StyleBorder()->mBorderRadius);
  if (clip) {
    borderBox = clip->ApplyNonRoundedIntersection(borderBox);
    if (clip->GetRoundedRectCount() > 0) {
      borderBoxHasRoundedCorners = true;
    }
  }
  if (borderBoxHasRoundedCorners ||
      (aFrame->GetStateBits() & NS_FRAME_SVG_LAYOUT)) {
    mMaybeHitRegion.Or(mMaybeHitRegion, borderBox);
  } else {
    mHitRegion.Or(mHitRegion, borderBox);
  }
  if (aBuilder->GetAncestorHasTouchEventHandler()) {
    mDispatchToContentHitRegion.Or(mDispatchToContentHitRegion, borderBox);
  }
}

void
nsDisplayCaret::Paint(nsDisplayListBuilder* aBuilder,
                      nsRenderingContext* aCtx) {
  // Note: Because we exist, we know that the caret is visible, so we don't
  // need to check for the caret's visibility.
  mCaret->PaintCaret(aBuilder, aCtx, mFrame, ToReferenceFrame());
}

bool
nsDisplayBorder::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                   nsRegion* aVisibleRegion,
                                   const nsRect& aAllowVisibleRegionExpansion) {
  if (!nsDisplayItem::ComputeVisibility(aBuilder, aVisibleRegion,
                                        aAllowVisibleRegionExpansion)) {
    return false;
  }

  nsRect paddingRect = mFrame->GetPaddingRect() - mFrame->GetPosition() +
    ToReferenceFrame();
  const nsStyleBorder *styleBorder;
  if (paddingRect.Contains(aVisibleRegion->GetBounds()) &&
      !(styleBorder = mFrame->StyleBorder())->IsBorderImageLoaded() &&
      !nsLayoutUtils::HasNonZeroCorner(styleBorder->mBorderRadius)) {
    // the visible region is entirely inside the content rect, and no part
    // of the border is rendered inside the content rect, so we are not
    // visible
    // Skip this if there's a border-image (which draws a background
    // too) or if there is a border-radius (which makes the border draw
    // further in).
    return false;
  }

  return true;
}
  
nsDisplayItemGeometry* 
nsDisplayBorder::AllocateGeometry(nsDisplayListBuilder* aBuilder)
{
  return new nsDisplayBorderGeometry(this, aBuilder);
}

void
nsDisplayBorder::ComputeInvalidationRegion(nsDisplayListBuilder* aBuilder,
                                           const nsDisplayItemGeometry* aGeometry,
                                           nsRegion* aInvalidRegion)
{
  const nsDisplayBorderGeometry* geometry = static_cast<const nsDisplayBorderGeometry*>(aGeometry);
  bool snap;
  if (!geometry->mBounds.IsEqualInterior(GetBounds(aBuilder, &snap)) ||
      !geometry->mContentRect.IsEqualInterior(GetContentRect())) {
    // We can probably get away with only invalidating the difference
    // between the border and padding rects, but the XUL ui at least
    // is apparently painting a background with this?
    aInvalidRegion->Or(GetBounds(aBuilder, &snap), geometry->mBounds);
  }
}
  
void
nsDisplayBorder::Paint(nsDisplayListBuilder* aBuilder,
                       nsRenderingContext* aCtx) {
  nsPoint offset = ToReferenceFrame();
  nsCSSRendering::PaintBorder(mFrame->PresContext(), *aCtx, mFrame,
                              mVisibleRect,
                              nsRect(offset, mFrame->GetSize()),
                              mFrame->StyleContext(),
                              mFrame->GetSkipSides());
}

nsRect
nsDisplayBorder::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap)
{
  *aSnap = true;
  return CalculateBounds(*mFrame->StyleBorder());
}

nsRect
nsDisplayBorder::CalculateBounds(const nsStyleBorder& aStyleBorder)
{
  nsRect borderBounds(ToReferenceFrame(), mFrame->GetSize());
  if (aStyleBorder.IsBorderImageLoaded()) {
    borderBounds.Inflate(aStyleBorder.GetImageOutset());
    return borderBounds;
  } else {
    nsMargin border = aStyleBorder.GetComputedBorder();
    nsRect result;
    if (border.top > 0) {
      result = nsRect(borderBounds.X(), borderBounds.Y(), borderBounds.Width(), border.top);
    }
    if (border.right > 0) {
      result.UnionRect(result, nsRect(borderBounds.XMost() - border.right, borderBounds.Y(), border.right, borderBounds.Height()));
    }
    if (border.bottom > 0) {
      result.UnionRect(result, nsRect(borderBounds.X(), borderBounds.YMost() - border.bottom, borderBounds.Width(), border.bottom));
    }
    if (border.left > 0) {
      result.UnionRect(result, nsRect(borderBounds.X(), borderBounds.Y(), border.left, borderBounds.Height()));
    }

    return result;
  }
}

// Given a region, compute a conservative approximation to it as a list
// of rectangles that aren't vertically adjacent (i.e., vertically
// adjacent or overlapping rectangles are combined).
// Right now this is only approximate, some vertically overlapping rectangles
// aren't guaranteed to be combined.
static void
ComputeDisjointRectangles(const nsRegion& aRegion,
                          nsTArray<nsRect>* aRects) {
  nscoord accumulationMargin = nsPresContext::CSSPixelsToAppUnits(25);
  nsRect accumulated;
  nsRegionRectIterator iter(aRegion);
  while (true) {
    const nsRect* r = iter.Next();
    if (r && !accumulated.IsEmpty() &&
        accumulated.YMost() >= r->y - accumulationMargin) {
      accumulated.UnionRect(accumulated, *r);
      continue;
    }

    if (!accumulated.IsEmpty()) {
      aRects->AppendElement(accumulated);
      accumulated.SetEmpty();
    }

    if (!r)
      break;

    accumulated = *r;
  }
}

void
nsDisplayBoxShadowOuter::Paint(nsDisplayListBuilder* aBuilder,
                               nsRenderingContext* aCtx) {
  nsPoint offset = ToReferenceFrame();
  nsRect borderRect = mFrame->VisualBorderRectRelativeToSelf() + offset;
  nsPresContext* presContext = mFrame->PresContext();
  nsAutoTArray<nsRect,10> rects;
  ComputeDisjointRectangles(mVisibleRegion, &rects);

  PROFILER_LABEL("nsDisplayBoxShadowOuter", "Paint");
  for (uint32_t i = 0; i < rects.Length(); ++i) {
    aCtx->PushState();
    aCtx->IntersectClip(rects[i]);
    nsCSSRendering::PaintBoxShadowOuter(presContext, *aCtx, mFrame,
                                        borderRect, rects[i], mOpacity);
    aCtx->PopState();
  }
}

nsRect
nsDisplayBoxShadowOuter::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap) {
  *aSnap = false;
  return mBounds;
}

nsRect
nsDisplayBoxShadowOuter::GetBoundsInternal() {
  return nsLayoutUtils::GetBoxShadowRectForFrame(mFrame, mFrame->GetSize()) +
         ToReferenceFrame();
}

bool
nsDisplayBoxShadowOuter::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                           nsRegion* aVisibleRegion,
                                           const nsRect& aAllowVisibleRegionExpansion) {
  if (!nsDisplayItem::ComputeVisibility(aBuilder, aVisibleRegion,
                                        aAllowVisibleRegionExpansion)) {
    return false;
  }

  // Store the actual visible region
  mVisibleRegion.And(*aVisibleRegion, mVisibleRect);

  nsPoint origin = ToReferenceFrame();
  nsRect visibleBounds = aVisibleRegion->GetBounds();
  nsRect frameRect(origin, mFrame->GetSize());
  if (!frameRect.Contains(visibleBounds))
    return true;

  // the visible region is entirely inside the border-rect, and box shadows
  // never render within the border-rect (unless there's a border radius).
  nscoord twipsRadii[8];
  bool hasBorderRadii = mFrame->GetBorderRadii(twipsRadii);
  if (!hasBorderRadii)
    return false;

  return !RoundedRectContainsRect(frameRect, twipsRadii, visibleBounds);
}

void
nsDisplayBoxShadowOuter::ComputeInvalidationRegion(nsDisplayListBuilder* aBuilder,
                                                   const nsDisplayItemGeometry* aGeometry,
                                                   nsRegion* aInvalidRegion)
{
  const nsDisplayItemGenericGeometry* geometry =
    static_cast<const nsDisplayItemGenericGeometry*>(aGeometry);
  bool snap;
  if (!geometry->mBounds.IsEqualInterior(GetBounds(aBuilder, &snap)) ||
      !geometry->mBorderRect.IsEqualInterior(GetBorderRect())) {
    nsRegion oldShadow, newShadow;
    nscoord dontCare[8];
    bool hasBorderRadius = mFrame->GetBorderRadii(dontCare);
    if (hasBorderRadius) {
      // If we have rounded corners then we need to invalidate the frame area
      // too since we paint into it.
      oldShadow = geometry->mBounds;
      newShadow = GetBounds(aBuilder, &snap);
    } else {
      oldShadow = oldShadow.Sub(geometry->mBounds, geometry->mBorderRect);
      newShadow = newShadow.Sub(GetBounds(aBuilder, &snap), GetBorderRect());
    }
    aInvalidRegion->Or(oldShadow, newShadow);
  }
}


void
nsDisplayBoxShadowInner::Paint(nsDisplayListBuilder* aBuilder,
                               nsRenderingContext* aCtx) {
  nsPoint offset = ToReferenceFrame();
  nsRect borderRect = nsRect(offset, mFrame->GetSize());
  nsPresContext* presContext = mFrame->PresContext();
  nsAutoTArray<nsRect,10> rects;
  ComputeDisjointRectangles(mVisibleRegion, &rects);

  PROFILER_LABEL("nsDisplayBoxShadowInner", "Paint");
  for (uint32_t i = 0; i < rects.Length(); ++i) {
    aCtx->PushState();
    aCtx->IntersectClip(rects[i]);
    nsCSSRendering::PaintBoxShadowInner(presContext, *aCtx, mFrame,
                                        borderRect, rects[i]);
    aCtx->PopState();
  }
}

bool
nsDisplayBoxShadowInner::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                           nsRegion* aVisibleRegion,
                                           const nsRect& aAllowVisibleRegionExpansion) {
  if (!nsDisplayItem::ComputeVisibility(aBuilder, aVisibleRegion,
                                        aAllowVisibleRegionExpansion)) {
    return false;
  }

  // Store the actual visible region
  mVisibleRegion.And(*aVisibleRegion, mVisibleRect);
  return true;
}

nsDisplayWrapList::nsDisplayWrapList(nsDisplayListBuilder* aBuilder,
                                     nsIFrame* aFrame, nsDisplayList* aList)
  : nsDisplayItem(aBuilder, aFrame) {
  mList.AppendToTop(aList);
  UpdateBounds(aBuilder);

  if (!aFrame || !aFrame->IsTransformed()) {
    return;
  }

  // If the frame is a preserve-3d parent, then we will create transforms
  // inside this list afterwards (see WrapPreserve3DList in nsFrame.cpp).
  // In this case we will always be outside of the transform, so share
  // our parents reference frame.
  if (aFrame->Preserves3DChildren()) {
    mReferenceFrame = 
      aBuilder->FindReferenceFrameFor(GetTransformRootFrame(aFrame));
    mToReferenceFrame = aFrame->GetOffsetToCrossDoc(mReferenceFrame);
    return;
  }

  // If we're a transformed frame, then we need to find out if we're inside
  // the nsDisplayTransform or outside of it. Frames inside the transform
  // need mReferenceFrame == mFrame, outside needs the next ancestor
  // reference frame.
  // If we're inside the transform, then the nsDisplayItem constructor
  // will have done the right thing.
  // If we're outside the transform, then we should have only one child
  // (since nsDisplayTransform wraps all actual content), and that child
  // will have the correct reference frame set (since nsDisplayTransform
  // handles this explictly).
  //
  // Preserve-3d can cause us to have multiple nsDisplayTransform
  // children.
  nsDisplayItem *i = mList.GetBottom();
  if (i && (!i->GetAbove() || i->GetType() == TYPE_TRANSFORM) && 
      i->Frame() == mFrame) {
    mReferenceFrame = i->ReferenceFrame();
    mToReferenceFrame = i->ToReferenceFrame();
  }
}

nsDisplayWrapList::nsDisplayWrapList(nsDisplayListBuilder* aBuilder,
                                     nsIFrame* aFrame, nsDisplayItem* aItem)
  : nsDisplayItem(aBuilder, aFrame) {
  mList.AppendToTop(aItem);
  UpdateBounds(aBuilder);
  
  if (!aFrame || !aFrame->IsTransformed()) {
    return;
  }

  if (aFrame->Preserves3DChildren()) {
    mReferenceFrame = 
      aBuilder->FindReferenceFrameFor(GetTransformRootFrame(aFrame));
    mToReferenceFrame = aFrame->GetOffsetToCrossDoc(mReferenceFrame);
    return;
  }

  // See the previous nsDisplayWrapList constructor
  if (aItem->Frame() == aFrame) {
    mReferenceFrame = aItem->ReferenceFrame();
    mToReferenceFrame = aItem->ToReferenceFrame();
  }
}

nsDisplayWrapList::nsDisplayWrapList(nsDisplayListBuilder* aBuilder,
                                     nsIFrame* aFrame, nsDisplayItem* aItem,
                                     const nsIFrame* aReferenceFrame,
                                     const nsPoint& aToReferenceFrame)
  : nsDisplayItem(aBuilder, aFrame, aReferenceFrame, aToReferenceFrame) {
  mList.AppendToTop(aItem);
  mBounds = mList.GetBounds(aBuilder);
}

nsDisplayWrapList::~nsDisplayWrapList() {
  mList.DeleteAll();
}

void
nsDisplayWrapList::HitTest(nsDisplayListBuilder* aBuilder, const nsRect& aRect,
                           HitTestState* aState, nsTArray<nsIFrame*> *aOutFrames) {
  mList.HitTest(aBuilder, aRect, aState, aOutFrames);
}

nsRect
nsDisplayWrapList::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap) {
  *aSnap = false;
  return mBounds;
}

bool
nsDisplayWrapList::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                     nsRegion* aVisibleRegion,
                                     const nsRect& aAllowVisibleRegionExpansion) {
  // Convert the passed in visible region to our appunits.
  nsRegion visibleRegion;
  // mVisibleRect has been clipped to GetClippedBounds
  visibleRegion.And(*aVisibleRegion, mVisibleRect);
  nsRegion originalVisibleRegion = visibleRegion;

  bool retval =
    mList.ComputeVisibilityForSublist(aBuilder, &visibleRegion,
                                      mVisibleRect,
                                      aAllowVisibleRegionExpansion);

  nsRegion removed;
  // removed = originalVisibleRegion - visibleRegion
  removed.Sub(originalVisibleRegion, visibleRegion);
  // aVisibleRegion = aVisibleRegion - removed (modulo any simplifications
  // SubtractFromVisibleRegion does)
  aBuilder->SubtractFromVisibleRegion(aVisibleRegion, removed);

  return retval;
}

nsRegion
nsDisplayWrapList::GetOpaqueRegion(nsDisplayListBuilder* aBuilder,
                                   bool* aSnap) {
  *aSnap = false;
  nsRegion result;
  if (mList.IsOpaque()) {
    // Everything within GetBounds that's visible is opaque.
    result = GetBounds(aBuilder, aSnap);
  }
  return result;
}

bool nsDisplayWrapList::IsUniform(nsDisplayListBuilder* aBuilder, nscolor* aColor) {
  // We could try to do something but let's conservatively just return false.
  return false;
}

bool nsDisplayWrapList::IsVaryingRelativeToMovingFrame(nsDisplayListBuilder* aBuilder,
                                                         nsIFrame* aFrame) {
  NS_WARNING("nsDisplayWrapList::IsVaryingRelativeToMovingFrame called unexpectedly");
  // We could try to do something but let's conservatively just return true.
  return true;
}

void nsDisplayWrapList::Paint(nsDisplayListBuilder* aBuilder,
                              nsRenderingContext* aCtx) {
  NS_ERROR("nsDisplayWrapList should have been flattened away for painting");
}

static LayerState
RequiredLayerStateForChildrenInternal(nsDisplayListBuilder* aBuilder,
                                      LayerManager* aManager,
                                      const ContainerLayerParameters& aParameters,
                                      const nsDisplayList& aList,
                                      nsIFrame* aAnimatedGeometryRoot)
{
  LayerState result = LAYER_INACTIVE;
  for (nsDisplayItem* i = aList.GetBottom(); i; i = i->GetAbove()) {
    nsIFrame* f = i->Frame();
    if (result == LAYER_INACTIVE &&
        nsLayoutUtils::GetAnimatedGeometryRootFor(f) != aAnimatedGeometryRoot) {
      result = LAYER_ACTIVE;
    }

    LayerState state = i->GetLayerState(aBuilder, aManager, aParameters);
    if ((state == LAYER_ACTIVE || state == LAYER_ACTIVE_FORCE) &&
        state > result) {
      result = state;
    }
    if (state == LAYER_ACTIVE_EMPTY && state > result) {
      result = LAYER_ACTIVE_FORCE;
    }
    if (state == LAYER_NONE) {
      nsDisplayList* list = i->GetSameCoordinateSystemChildren();
      if (list) {
        LayerState childState =
          RequiredLayerStateForChildrenInternal(aBuilder, aManager, aParameters, *list,
              aAnimatedGeometryRoot);
        if (childState > result) {
          result = childState;
        }
      }
    }
  }
  return result;
}

LayerState
nsDisplayWrapList::RequiredLayerStateForChildren(nsDisplayListBuilder* aBuilder,
                                                 LayerManager* aManager,
                                                 const ContainerLayerParameters& aParameters,
                                                 const nsDisplayList& aList,
                                                 nsIFrame* aItemFrame)
{
  return RequiredLayerStateForChildrenInternal(
      aBuilder, aManager, aParameters, aList,
      nsLayoutUtils::GetAnimatedGeometryRootFor(aItemFrame));
}

nsRect nsDisplayWrapList::GetComponentAlphaBounds(nsDisplayListBuilder* aBuilder)
{
  nsRect bounds;
  for (nsDisplayItem* i = mList.GetBottom(); i; i = i->GetAbove()) {
    bounds.UnionRect(bounds, i->GetComponentAlphaBounds(aBuilder));
  }
  return bounds;
}

static nsresult
WrapDisplayList(nsDisplayListBuilder* aBuilder, nsIFrame* aFrame,
                nsDisplayList* aList, nsDisplayWrapper* aWrapper) {
  if (!aList->GetTop())
    return NS_OK;
  nsDisplayItem* item = aWrapper->WrapList(aBuilder, aFrame, aList);
  if (!item)
    return NS_ERROR_OUT_OF_MEMORY;
  // aList was emptied
  aList->AppendToTop(item);
  return NS_OK;
}

static nsresult
WrapEachDisplayItem(nsDisplayListBuilder* aBuilder,
                    nsDisplayList* aList, nsDisplayWrapper* aWrapper) {
  nsDisplayList newList;
  nsDisplayItem* item;
  while ((item = aList->RemoveBottom())) {
    item = aWrapper->WrapItem(aBuilder, item);
    if (!item)
      return NS_ERROR_OUT_OF_MEMORY;
    newList.AppendToTop(item);
  }
  // aList was emptied
  aList->AppendToTop(&newList);
  return NS_OK;
}

nsresult nsDisplayWrapper::WrapLists(nsDisplayListBuilder* aBuilder,
    nsIFrame* aFrame, const nsDisplayListSet& aIn, const nsDisplayListSet& aOut)
{
  nsresult rv = WrapListsInPlace(aBuilder, aFrame, aIn);
  NS_ENSURE_SUCCESS(rv, rv);

  if (&aOut == &aIn)
    return NS_OK;
  aOut.BorderBackground()->AppendToTop(aIn.BorderBackground());
  aOut.BlockBorderBackgrounds()->AppendToTop(aIn.BlockBorderBackgrounds());
  aOut.Floats()->AppendToTop(aIn.Floats());
  aOut.Content()->AppendToTop(aIn.Content());
  aOut.PositionedDescendants()->AppendToTop(aIn.PositionedDescendants());
  aOut.Outlines()->AppendToTop(aIn.Outlines());
  return NS_OK;
}

nsresult nsDisplayWrapper::WrapListsInPlace(nsDisplayListBuilder* aBuilder,
    nsIFrame* aFrame, const nsDisplayListSet& aLists)
{
  nsresult rv;
  if (WrapBorderBackground()) {
    // Our border-backgrounds are in-flow
    rv = WrapDisplayList(aBuilder, aFrame, aLists.BorderBackground(), this);
    NS_ENSURE_SUCCESS(rv, rv);
  }
  // Our block border-backgrounds are in-flow
  rv = WrapDisplayList(aBuilder, aFrame, aLists.BlockBorderBackgrounds(), this);
  NS_ENSURE_SUCCESS(rv, rv);
  // The floats are not in flow
  rv = WrapEachDisplayItem(aBuilder, aLists.Floats(), this);
  NS_ENSURE_SUCCESS(rv, rv);
  // Our child content is in flow
  rv = WrapDisplayList(aBuilder, aFrame, aLists.Content(), this);
  NS_ENSURE_SUCCESS(rv, rv);
  // The positioned descendants may not be in-flow
  rv = WrapEachDisplayItem(aBuilder, aLists.PositionedDescendants(), this);
  NS_ENSURE_SUCCESS(rv, rv);
  // The outlines may not be in-flow
  return WrapEachDisplayItem(aBuilder, aLists.Outlines(), this);
}

nsDisplayOpacity::nsDisplayOpacity(nsDisplayListBuilder* aBuilder,
                                   nsIFrame* aFrame, nsDisplayList* aList)
    : nsDisplayWrapList(aBuilder, aFrame, aList) {
  MOZ_COUNT_CTOR(nsDisplayOpacity);
}

#ifdef NS_BUILD_REFCNT_LOGGING
nsDisplayOpacity::~nsDisplayOpacity() {
  MOZ_COUNT_DTOR(nsDisplayOpacity);
}
#endif

nsRegion nsDisplayOpacity::GetOpaqueRegion(nsDisplayListBuilder* aBuilder,
                                           bool* aSnap) {
  *aSnap = false;
  // We are never opaque, if our opacity was < 1 then we wouldn't have
  // been created.
  return nsRegion();
}

// nsDisplayOpacity uses layers for rendering
already_AddRefed<Layer>
nsDisplayOpacity::BuildLayer(nsDisplayListBuilder* aBuilder,
                             LayerManager* aManager,
                             const ContainerLayerParameters& aContainerParameters) {
  if (mFrame->StyleDisplay()->mOpacity == 0 && mFrame->GetContent() &&
      !nsLayoutUtils::HasAnimations(mFrame->GetContent(), eCSSProperty_opacity)) {
    return nullptr;
  }
  nsRefPtr<Layer> container = aManager->GetLayerBuilder()->
    BuildContainerLayerFor(aBuilder, aManager, mFrame, this, mList,
                           aContainerParameters, nullptr);
  if (!container)
    return nullptr;

  container->SetOpacity(mFrame->StyleDisplay()->mOpacity);
  nsDisplayListBuilder::AddAnimationsAndTransitionsToLayer(container, aBuilder,
                                                           this, mFrame,
                                                           eCSSProperty_opacity);
  return container.forget();
}

/**
 * This doesn't take into account layer scaling --- the layer may be
 * rendered at a higher (or lower) resolution, affecting the retained layer
 * size --- but this should be good enough.
 */
static bool
IsItemTooSmallForActiveLayer(nsDisplayItem* aItem)
{
  nsIntRect visibleDevPixels = aItem->GetVisibleRect().ToOutsidePixels(
          aItem->Frame()->PresContext()->AppUnitsPerDevPixel());
  static const int MIN_ACTIVE_LAYER_SIZE_DEV_PIXELS = 16;
  return visibleDevPixels.Size() <
    nsIntSize(MIN_ACTIVE_LAYER_SIZE_DEV_PIXELS, MIN_ACTIVE_LAYER_SIZE_DEV_PIXELS);
}

bool
nsDisplayOpacity::NeedsActiveLayer()
{
  if (ActiveLayerTracker::IsStyleAnimated(mFrame, eCSSProperty_opacity) &&
      !IsItemTooSmallForActiveLayer(this))
    return true;
  if (mFrame->GetContent()) {
    if (nsLayoutUtils::HasAnimationsForCompositor(mFrame->GetContent(),
                                                  eCSSProperty_opacity)) {
      return true;
    }
  }
  return false;
}

bool
nsDisplayOpacity::ShouldFlattenAway(nsDisplayListBuilder* aBuilder)
{
  if (NeedsActiveLayer())
    return false;

  nsDisplayItem* child = mList.GetBottom();
  // Only try folding our opacity down if we have a single
  // child. We could potentially do this also if we had multiple
  // children as long as they don't overlap.
  if (!child || child->GetAbove()) {
    return false;
  }

  return child->ApplyOpacity(aBuilder, mFrame->StyleDisplay()->mOpacity, mClip);
}

nsDisplayItem::LayerState
nsDisplayOpacity::GetLayerState(nsDisplayListBuilder* aBuilder,
                                LayerManager* aManager,
                                const ContainerLayerParameters& aParameters) {
  if (NeedsActiveLayer())
    return LAYER_ACTIVE;

  return RequiredLayerStateForChildren(aBuilder, aManager, aParameters, mList, mFrame);
}

bool
nsDisplayOpacity::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                    nsRegion* aVisibleRegion,
                                    const nsRect& aAllowVisibleRegionExpansion) {
  // Our children are translucent so we should not allow them to subtract
  // area from aVisibleRegion. We do need to find out what is visible under
  // our children in the temporary compositing buffer, because if our children
  // paint our entire bounds opaquely then we don't need an alpha channel in
  // the temporary compositing buffer.
  nsRect bounds = GetClippedBounds(aBuilder);
  nsRegion visibleUnderChildren;
  visibleUnderChildren.And(*aVisibleRegion, bounds);
  nsRect allowExpansion = bounds.Intersect(aAllowVisibleRegionExpansion);
  return
    nsDisplayWrapList::ComputeVisibility(aBuilder, &visibleUnderChildren,
                                         allowExpansion);
}

bool nsDisplayOpacity::TryMerge(nsDisplayListBuilder* aBuilder, nsDisplayItem* aItem) {
  if (aItem->GetType() != TYPE_OPACITY)
    return false;
  // items for the same content element should be merged into a single
  // compositing group
  // aItem->GetUnderlyingFrame() returns non-null because it's nsDisplayOpacity
  if (aItem->Frame()->GetContent() != mFrame->GetContent())
    return false;
  if (aItem->GetClip() != GetClip())
    return false;
  MergeFromTrackingMergedFrames(static_cast<nsDisplayOpacity*>(aItem));
  return true;
}

#ifdef MOZ_DUMP_PAINTING
void
nsDisplayOpacity::WriteDebugInfo(nsACString& aTo)
{
  aTo += nsPrintfCString(" (opacity %f)", mFrame->StyleDisplay()->mOpacity);
}
#endif

nsDisplayMixBlendMode::nsDisplayMixBlendMode(nsDisplayListBuilder* aBuilder,
                                             nsIFrame* aFrame, nsDisplayList* aList,
                                             uint32_t aFlags)
: nsDisplayWrapList(aBuilder, aFrame, aList) {
  MOZ_COUNT_CTOR(nsDisplayMixBlendMode);
}

#ifdef NS_BUILD_REFCNT_LOGGING
nsDisplayMixBlendMode::~nsDisplayMixBlendMode() {
  MOZ_COUNT_DTOR(nsDisplayMixBlendMode);
}
#endif

nsRegion nsDisplayMixBlendMode::GetOpaqueRegion(nsDisplayListBuilder* aBuilder,
                                                bool* aSnap) {
  *aSnap = false;
  // We are never considered opaque
  return nsRegion();
}

// nsDisplayMixBlendMode uses layers for rendering
already_AddRefed<Layer>
nsDisplayMixBlendMode::BuildLayer(nsDisplayListBuilder* aBuilder,
                                  LayerManager* aManager,
                                  const ContainerLayerParameters& aContainerParameters) {
  ContainerLayerParameters newContainerParameters = aContainerParameters;
  newContainerParameters.mDisableSubpixelAntialiasingInDescendants = true;

  nsRefPtr<Layer> container = aManager->GetLayerBuilder()->
  BuildContainerLayerFor(aBuilder, aManager, mFrame, this, mList,
                         newContainerParameters, nullptr);
  if (!container) {
    return nullptr;
  }

  container->DeprecatedSetMixBlendMode(nsCSSRendering::GetGFXBlendMode(mFrame->StyleDisplay()->mMixBlendMode));

  return container.forget();
}

bool nsDisplayMixBlendMode::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                              nsRegion* aVisibleRegion,
                                              const nsRect& aAllowVisibleRegionExpansion) {
  // Our children are need their backdrop so we should not allow them to subtract
  // area from aVisibleRegion. We do need to find out what is visible under
  // our children in the temporary compositing buffer, because if our children
  // paint our entire bounds opaquely then we don't need an alpha channel in
  // the temporary compositing buffer.
  nsRect bounds = GetClippedBounds(aBuilder);
  nsRegion visibleUnderChildren;
  visibleUnderChildren.And(*aVisibleRegion, bounds);
  nsRect allowExpansion = bounds.Intersect(aAllowVisibleRegionExpansion);
  return
  nsDisplayWrapList::ComputeVisibility(aBuilder, &visibleUnderChildren,
                                       allowExpansion);
}

bool nsDisplayMixBlendMode::TryMerge(nsDisplayListBuilder* aBuilder, nsDisplayItem* aItem) {
  if (aItem->GetType() != TYPE_MIX_BLEND_MODE)
    return false;
  // items for the same content element should be merged into a single
  // compositing group
  // aItem->GetUnderlyingFrame() returns non-null because it's nsDisplayOpacity
  if (aItem->Frame()->GetContent() != mFrame->GetContent())
    return false;
  if (aItem->GetClip() != GetClip())
    return false;
  MergeFromTrackingMergedFrames(static_cast<nsDisplayMixBlendMode*>(aItem));
  return true;
}

nsDisplayBlendContainer::nsDisplayBlendContainer(nsDisplayListBuilder* aBuilder,
                                                 nsIFrame* aFrame, nsDisplayList* aList,
                                                 uint32_t aFlags)
    : nsDisplayWrapList(aBuilder, aFrame, aList) {
  MOZ_COUNT_CTOR(nsDisplayBlendContainer);
}

#ifdef NS_BUILD_REFCNT_LOGGING
nsDisplayBlendContainer::~nsDisplayBlendContainer() {
  MOZ_COUNT_DTOR(nsDisplayBlendContainer);
}
#endif

// nsDisplayBlendContainer uses layers for rendering
already_AddRefed<Layer>
nsDisplayBlendContainer::BuildLayer(nsDisplayListBuilder* aBuilder,
                                    LayerManager* aManager,
                                    const ContainerLayerParameters& aContainerParameters) {
  // turn off anti-aliasing in the parent stacking context because it changes
  // how the group is initialized.
  ContainerLayerParameters newContainerParameters = aContainerParameters;
  newContainerParameters.mDisableSubpixelAntialiasingInDescendants = true;

  nsRefPtr<Layer> container = aManager->GetLayerBuilder()->
  BuildContainerLayerFor(aBuilder, aManager, mFrame, this, mList,
                         newContainerParameters, nullptr);
  if (!container) {
    return nullptr;
  }
  
  container->SetForceIsolatedGroup(true);
  return container.forget();
}

bool nsDisplayBlendContainer::TryMerge(nsDisplayListBuilder* aBuilder, nsDisplayItem* aItem) {
  if (aItem->GetType() != TYPE_BLEND_CONTAINER)
    return false;
  // items for the same content element should be merged into a single
  // compositing group
  // aItem->GetUnderlyingFrame() returns non-null because it's nsDisplayOpacity
  if (aItem->Frame()->GetContent() != mFrame->GetContent())
    return false;
  if (aItem->GetClip() != GetClip())
    return false;
  MergeFromTrackingMergedFrames(static_cast<nsDisplayBlendContainer*>(aItem));
  return true;
}

nsDisplayOwnLayer::nsDisplayOwnLayer(nsDisplayListBuilder* aBuilder,
                                     nsIFrame* aFrame, nsDisplayList* aList,
                                     uint32_t aFlags, ViewID aScrollTarget)
    : nsDisplayWrapList(aBuilder, aFrame, aList)
    , mFlags(aFlags)
    , mScrollTarget(aScrollTarget) {
  MOZ_COUNT_CTOR(nsDisplayOwnLayer);
}

#ifdef NS_BUILD_REFCNT_LOGGING
nsDisplayOwnLayer::~nsDisplayOwnLayer() {
  MOZ_COUNT_DTOR(nsDisplayOwnLayer);
}
#endif

// nsDisplayOpacity uses layers for rendering
already_AddRefed<Layer>
nsDisplayOwnLayer::BuildLayer(nsDisplayListBuilder* aBuilder,
                              LayerManager* aManager,
                              const ContainerLayerParameters& aContainerParameters) {
  nsRefPtr<ContainerLayer> layer = aManager->GetLayerBuilder()->
    BuildContainerLayerFor(aBuilder, aManager, mFrame, this, mList,
                           aContainerParameters, nullptr);
  if (mFlags & VERTICAL_SCROLLBAR) {
    layer->SetScrollbarData(mScrollTarget, Layer::ScrollDirection::VERTICAL);
  }
  if (mFlags & HORIZONTAL_SCROLLBAR) {
    layer->SetScrollbarData(mScrollTarget, Layer::ScrollDirection::HORIZONTAL);
  }

  if (mFlags & GENERATE_SUBDOC_INVALIDATIONS) {
    mFrame->PresContext()->SetNotifySubDocInvalidationData(layer);
  }
  return layer.forget();
}

nsDisplaySubDocument::nsDisplaySubDocument(nsDisplayListBuilder* aBuilder,
                                           nsIFrame* aFrame, nsDisplayList* aList,
                                           uint32_t aFlags)
    : nsDisplayOwnLayer(aBuilder, aFrame, aList, aFlags) {
  MOZ_COUNT_CTOR(nsDisplaySubDocument);
}

#ifdef NS_BUILD_REFCNT_LOGGING
nsDisplaySubDocument::~nsDisplaySubDocument() {
  MOZ_COUNT_DTOR(nsDisplaySubDocument);
}
#endif

already_AddRefed<Layer>
nsDisplaySubDocument::BuildLayer(nsDisplayListBuilder* aBuilder,
                                 LayerManager* aManager,
                                 const ContainerLayerParameters& aContainerParameters) {
  nsRefPtr<Layer> layer = nsDisplayOwnLayer::BuildLayer(
    aBuilder, aManager, aContainerParameters);

  if (!(mFlags & GENERATE_SCROLLABLE_LAYER)) {
    return layer.forget();
  }

  NS_ASSERTION(layer->AsContainerLayer(), "nsDisplayOwnLayer should have made a ContainerLayer");
  if (ContainerLayer* container = layer->AsContainerLayer()) {
    nsPresContext* presContext = mFrame->PresContext();
    nsIFrame* rootScrollFrame = presContext->PresShell()->GetRootScrollFrame();
    bool isRootContentDocument = presContext->IsRootContentDocument();

    bool usingDisplayport = false;
    bool usingCriticalDisplayport = false;
    nsRect displayport, criticalDisplayport;
    ViewID scrollId = FrameMetrics::NULL_SCROLL_ID;
    if (rootScrollFrame) {
      nsIContent* content = rootScrollFrame->GetContent();
      if (content) {
        usingDisplayport = nsLayoutUtils::GetDisplayPort(content, &displayport);
        usingCriticalDisplayport =
          nsLayoutUtils::GetCriticalDisplayPort(content, &criticalDisplayport);

        if (isRootContentDocument) {
          scrollId = nsLayoutUtils::FindOrCreateIDFor(content);
        } else {
          nsLayoutUtils::FindIDFor(content, &scrollId);
        }
      }
    }

    nsRect viewport = mFrame->GetRect() -
                      mFrame->GetPosition() +
                      mFrame->GetOffsetToCrossDoc(ReferenceFrame());

    RecordFrameMetrics(mFrame, rootScrollFrame, ReferenceFrame(),
                       container, mList.GetVisibleRect(), viewport,
                       (usingDisplayport ? &displayport : nullptr),
                       (usingCriticalDisplayport ? &criticalDisplayport : nullptr),
                       scrollId, isRootContentDocument, aContainerParameters);
  }

  return layer.forget();
}

nsRect
nsDisplaySubDocument::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap)
{
  bool usingDisplayPort =
    nsLayoutUtils::ViewportHasDisplayPort(mFrame->PresContext());

  if ((mFlags & GENERATE_SCROLLABLE_LAYER) && usingDisplayPort) {
    *aSnap = false;
    return mFrame->GetRect() + aBuilder->ToReferenceFrame(mFrame);
  }

  return nsDisplayOwnLayer::GetBounds(aBuilder, aSnap);
}

bool
nsDisplaySubDocument::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                        nsRegion* aVisibleRegion,
                                        const nsRect& aAllowVisibleRegionExpansion)
{
  nsRect displayport;
  bool usingDisplayPort =
    nsLayoutUtils::ViewportHasDisplayPort(mFrame->PresContext(), &displayport);

  if (!(mFlags & GENERATE_SCROLLABLE_LAYER) || !usingDisplayPort) {
    return nsDisplayWrapList::ComputeVisibility(aBuilder, aVisibleRegion,
                                                aAllowVisibleRegionExpansion);
  }

  nsRegion childVisibleRegion;
  // The visible region for the children may be much bigger than the hole we
  // are viewing the children from, so that the compositor process has enough
  // content to asynchronously pan while content is being refreshed.
  childVisibleRegion = displayport + mFrame->GetOffsetToCrossDoc(ReferenceFrame());

  nsRect boundedRect =
    childVisibleRegion.GetBounds().Intersect(mList.GetBounds(aBuilder));
  nsRect allowExpansion = boundedRect.Intersect(aAllowVisibleRegionExpansion);
  bool visible = mList.ComputeVisibilityForSublist(
    aBuilder, &childVisibleRegion, boundedRect, allowExpansion,
    usingDisplayPort ? mFrame : nullptr);
  // We don't allow this computation to influence aVisibleRegion, on the
  // assumption that the layer can be asynchronously scrolled so we'll
  // definitely need all the content under it.

  return visible;
}

bool
nsDisplaySubDocument::ShouldBuildLayerEvenIfInvisible(nsDisplayListBuilder* aBuilder)
{
  bool usingDisplayPort =
    nsLayoutUtils::ViewportHasDisplayPort(mFrame->PresContext());

  if ((mFlags & GENERATE_SCROLLABLE_LAYER) && usingDisplayPort) {
    return true;
  }

  return nsDisplayOwnLayer::ShouldBuildLayerEvenIfInvisible(aBuilder);
}

nsRegion
nsDisplaySubDocument::GetOpaqueRegion(nsDisplayListBuilder* aBuilder, bool* aSnap)
{
  bool usingDisplayPort =
    nsLayoutUtils::ViewportHasDisplayPort(mFrame->PresContext());

  if ((mFlags & GENERATE_SCROLLABLE_LAYER) && usingDisplayPort) {
    *aSnap = false;
    return nsRegion();
  }

  return nsDisplayOwnLayer::GetOpaqueRegion(aBuilder, aSnap);
}

nsDisplayResolution::nsDisplayResolution(nsDisplayListBuilder* aBuilder,
                                         nsIFrame* aFrame, nsDisplayList* aList,
                                         uint32_t aFlags)
    : nsDisplaySubDocument(aBuilder, aFrame, aList, aFlags) {
  MOZ_COUNT_CTOR(nsDisplayResolution);
}

#ifdef NS_BUILD_REFCNT_LOGGING
nsDisplayResolution::~nsDisplayResolution() {
  MOZ_COUNT_DTOR(nsDisplayResolution);
}
#endif

already_AddRefed<Layer>
nsDisplayResolution::BuildLayer(nsDisplayListBuilder* aBuilder,
                                LayerManager* aManager,
                                const ContainerLayerParameters& aContainerParameters) {
  nsIPresShell* presShell = mFrame->PresContext()->PresShell();
  ContainerLayerParameters containerParameters(
    presShell->GetXResolution(), presShell->GetYResolution(), nsIntPoint(),
    aContainerParameters);

  nsRefPtr<Layer> layer = nsDisplaySubDocument::BuildLayer(
    aBuilder, aManager, containerParameters);
  layer->SetPostScale(1.0f / presShell->GetXResolution(),
                      1.0f / presShell->GetYResolution());
  return layer.forget();
}

nsDisplayStickyPosition::nsDisplayStickyPosition(nsDisplayListBuilder* aBuilder,
                                                 nsIFrame* aFrame,
                                                 nsDisplayList* aList)
  : nsDisplayOwnLayer(aBuilder, aFrame, aList)
{
  MOZ_COUNT_CTOR(nsDisplayStickyPosition);
}

#ifdef NS_BUILD_REFCNT_LOGGING
nsDisplayStickyPosition::~nsDisplayStickyPosition() {
  MOZ_COUNT_DTOR(nsDisplayStickyPosition);
}
#endif

already_AddRefed<Layer>
nsDisplayStickyPosition::BuildLayer(nsDisplayListBuilder* aBuilder,
                                    LayerManager* aManager,
                                    const ContainerLayerParameters& aContainerParameters) {
  nsRefPtr<Layer> layer =
    nsDisplayOwnLayer::BuildLayer(aBuilder, aManager, aContainerParameters);

  StickyScrollContainer* stickyScrollContainer = StickyScrollContainer::
    GetStickyScrollContainerForFrame(mFrame);
  if (!stickyScrollContainer) {
    return layer.forget();
  }

  nsIFrame* scrollFrame = do_QueryFrame(stickyScrollContainer->ScrollFrame());
  nsPresContext* presContext = scrollFrame->PresContext();

  // Sticky position frames whose scroll frame is the root scroll frame are
  // reflowed into the scroll-port size if one has been set.
  nsSize scrollFrameSize = scrollFrame->GetSize();
  if (scrollFrame == presContext->PresShell()->GetRootScrollFrame() &&
      presContext->PresShell()->IsScrollPositionClampingScrollPortSizeSet()) {
    scrollFrameSize = presContext->PresShell()->
      GetScrollPositionClampingScrollPortSize();
  }

  nsLayoutUtils::SetFixedPositionLayerData(layer, scrollFrame,
    nsRect(scrollFrame->GetOffsetToCrossDoc(ReferenceFrame()), scrollFrameSize),
    mFrame, presContext, aContainerParameters);

  ViewID scrollId = nsLayoutUtils::FindOrCreateIDFor(
    stickyScrollContainer->ScrollFrame()->GetScrolledFrame()->GetContent());

  float factor = presContext->AppUnitsPerDevPixel();
  nsRect outer;
  nsRect inner;
  stickyScrollContainer->GetScrollRanges(mFrame, &outer, &inner);
  LayerRect stickyOuter(NSAppUnitsToFloatPixels(outer.x, factor) *
                          aContainerParameters.mXScale,
                        NSAppUnitsToFloatPixels(outer.y, factor) *
                          aContainerParameters.mYScale,
                        NSAppUnitsToFloatPixels(outer.width, factor) *
                          aContainerParameters.mXScale,
                        NSAppUnitsToFloatPixels(outer.height, factor) *
                          aContainerParameters.mYScale);
  LayerRect stickyInner(NSAppUnitsToFloatPixels(inner.x, factor) *
                          aContainerParameters.mXScale,
                        NSAppUnitsToFloatPixels(inner.y, factor) *
                          aContainerParameters.mYScale,
                        NSAppUnitsToFloatPixels(inner.width, factor) *
                          aContainerParameters.mXScale,
                        NSAppUnitsToFloatPixels(inner.height, factor) *
                          aContainerParameters.mYScale);
  layer->SetStickyPositionData(scrollId, stickyOuter, stickyInner);

  return layer.forget();
}

bool nsDisplayStickyPosition::TryMerge(nsDisplayListBuilder* aBuilder, nsDisplayItem* aItem) {
  if (aItem->GetType() != TYPE_STICKY_POSITION)
    return false;
  // Items with the same fixed position frame can be merged.
  nsDisplayStickyPosition* other = static_cast<nsDisplayStickyPosition*>(aItem);
  if (other->mFrame != mFrame)
    return false;
  if (aItem->GetClip() != GetClip())
    return false;
  MergeFromTrackingMergedFrames(other);
  return true;
}

nsDisplayScrollLayer::nsDisplayScrollLayer(nsDisplayListBuilder* aBuilder,
                                           nsDisplayList* aList,
                                           nsIFrame* aForFrame,
                                           nsIFrame* aScrolledFrame,
                                           nsIFrame* aScrollFrame)
  : nsDisplayWrapList(aBuilder, aForFrame, aList)
  , mScrollFrame(aScrollFrame)
  , mScrolledFrame(aScrolledFrame)
{
#ifdef NS_BUILD_REFCNT_LOGGING
  MOZ_COUNT_CTOR(nsDisplayScrollLayer);
#endif

  NS_ASSERTION(mScrolledFrame && mScrolledFrame->GetContent(),
               "Need a child frame with content");
}

nsDisplayScrollLayer::nsDisplayScrollLayer(nsDisplayListBuilder* aBuilder,
                                           nsDisplayItem* aItem,
                                           nsIFrame* aForFrame,
                                           nsIFrame* aScrolledFrame,
                                           nsIFrame* aScrollFrame)
  : nsDisplayWrapList(aBuilder, aForFrame, aItem)
  , mScrollFrame(aScrollFrame)
  , mScrolledFrame(aScrolledFrame)
{
#ifdef NS_BUILD_REFCNT_LOGGING
  MOZ_COUNT_CTOR(nsDisplayScrollLayer);
#endif

  NS_ASSERTION(mScrolledFrame && mScrolledFrame->GetContent(),
               "Need a child frame with content");
}

nsDisplayScrollLayer::nsDisplayScrollLayer(nsDisplayListBuilder* aBuilder,
                                           nsIFrame* aForFrame,
                                           nsIFrame* aScrolledFrame,
                                           nsIFrame* aScrollFrame)
  : nsDisplayWrapList(aBuilder, aForFrame)
  , mScrollFrame(aScrollFrame)
  , mScrolledFrame(aScrolledFrame)
{
#ifdef NS_BUILD_REFCNT_LOGGING
  MOZ_COUNT_CTOR(nsDisplayScrollLayer);
#endif

  NS_ASSERTION(mScrolledFrame && mScrolledFrame->GetContent(),
               "Need a child frame with content");
}

#ifdef NS_BUILD_REFCNT_LOGGING
nsDisplayScrollLayer::~nsDisplayScrollLayer()
{
  MOZ_COUNT_DTOR(nsDisplayScrollLayer);
}
#endif

nsRect
nsDisplayScrollLayer::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap)
{
  nsIScrollableFrame* sf = do_QueryFrame(mScrollFrame);
  if (sf) {
    *aSnap = false;
    return sf->GetScrollPortRect() + aBuilder->ToReferenceFrame(mScrollFrame);
  }
  return nsDisplayWrapList::GetBounds(aBuilder, aSnap);
}

already_AddRefed<Layer>
nsDisplayScrollLayer::BuildLayer(nsDisplayListBuilder* aBuilder,
                                 LayerManager* aManager,
                                 const ContainerLayerParameters& aContainerParameters) {
  nsRefPtr<ContainerLayer> layer = aManager->GetLayerBuilder()->
    BuildContainerLayerFor(aBuilder, aManager, mFrame, this, mList,
                           aContainerParameters, nullptr);

  // Get the already set unique ID for scrolling this content remotely.
  // Or, if not set, generate a new ID.
  nsIContent* content = mScrolledFrame->GetContent();
  ViewID scrollId = nsLayoutUtils::FindOrCreateIDFor(content);

  nsRect viewport = mScrollFrame->GetRect() -
                    mScrollFrame->GetPosition() +
                    mScrollFrame->GetOffsetToCrossDoc(ReferenceFrame());

  bool usingDisplayport = false;
  bool usingCriticalDisplayport = false;
  nsRect displayport, criticalDisplayport;
  if (content) {
    usingDisplayport = nsLayoutUtils::GetDisplayPort(content, &displayport);
    usingCriticalDisplayport =
      nsLayoutUtils::GetCriticalDisplayPort(content, &criticalDisplayport);
  }
  RecordFrameMetrics(mScrolledFrame, mScrollFrame, ReferenceFrame(), layer,
                     mList.GetVisibleRect(), viewport,
                     (usingDisplayport ? &displayport : nullptr),
                     (usingCriticalDisplayport ? &criticalDisplayport : nullptr),
                     scrollId, false, aContainerParameters);

  return layer.forget();
}

bool
nsDisplayScrollLayer::ShouldBuildLayerEvenIfInvisible(nsDisplayListBuilder* aBuilder)
{
  if (nsLayoutUtils::GetDisplayPort(mScrolledFrame->GetContent(), nullptr)) {
    return true;
  }

  return nsDisplayWrapList::ShouldBuildLayerEvenIfInvisible(aBuilder);
}

bool
nsDisplayScrollLayer::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                        nsRegion* aVisibleRegion,
                                        const nsRect& aAllowVisibleRegionExpansion)
{
  nsRect displayport;
  bool usingDisplayPort =
    nsLayoutUtils::GetDisplayPort(mScrolledFrame->GetContent(), &displayport);
  nsRegion childVisibleRegion;
  if (usingDisplayPort) {
    // The visible region for the children may be much bigger than the hole we
    // are viewing the children from, so that the compositor process has enough
    // content to asynchronously pan while content is being refreshed.
    childVisibleRegion = displayport + mScrollFrame->GetOffsetToCrossDoc(ReferenceFrame());
  } else {
    bool snap;
    childVisibleRegion = GetBounds(aBuilder, &snap);
  }

  nsRect boundedRect =
    childVisibleRegion.GetBounds().Intersect(mList.GetBounds(aBuilder));
  nsRect allowExpansion = boundedRect.Intersect(aAllowVisibleRegionExpansion);
  bool visible = mList.ComputeVisibilityForSublist(
    aBuilder, &childVisibleRegion, boundedRect, allowExpansion,
    usingDisplayPort ? mScrollFrame : nullptr);
  // We don't allow this computation to influence aVisibleRegion, on the
  // assumption that the layer can be asynchronously scrolled so we'll
  // definitely need all the content under it.

  return visible;
}

LayerState
nsDisplayScrollLayer::GetLayerState(nsDisplayListBuilder* aBuilder,
                                    LayerManager* aManager,
                                    const ContainerLayerParameters& aParameters)
{
  // Force this as a layer so we can scroll asynchronously.
  // This causes incorrect rendering for rounded clips!
  return LAYER_ACTIVE_FORCE;
}

// Check if we are going to clip an abs pos item that we don't contain.
// Root scroll frames clip all their descendants, so we don't need to worry
// about them.
bool
WouldCauseIncorrectClippingOnAbsPosItem(nsDisplayListBuilder* aBuilder,
                                        nsDisplayScrollLayer* aItem)
{
  nsIFrame* scrollFrame = aItem->GetScrollFrame();
  nsIPresShell* presShell = scrollFrame->PresContext()->PresShell();
  if (scrollFrame == presShell->GetRootScrollFrame()) {
    return false;
  }
  nsIFrame* scrolledFrame = aItem->GetScrolledFrame();
  nsIFrame* frame = aItem->Frame();
  if (frame == scrolledFrame || !frame->IsAbsolutelyPositioned() ||
      nsLayoutUtils::IsAncestorFrameCrossDoc(scrollFrame, frame, presShell->GetRootFrame())) {
    return false;
  }
  if (!aItem->GetClip().IsRectAffectedByClip(aItem->GetChildren()->GetBounds(aBuilder))) {
    return false;
  }
  return true;
}

bool
nsDisplayScrollLayer::TryMerge(nsDisplayListBuilder* aBuilder,
                               nsDisplayItem* aItem)
{
  if (aItem->GetType() != TYPE_SCROLL_LAYER) {
    return false;
  }
  nsDisplayScrollLayer* other = static_cast<nsDisplayScrollLayer*>(aItem);
  if (other->mScrolledFrame != this->mScrolledFrame) {
    return false;
  }
  if (aItem->GetClip() != GetClip()) {
    return false;
  }

  if (WouldCauseIncorrectClippingOnAbsPosItem(aBuilder, this) ||
      WouldCauseIncorrectClippingOnAbsPosItem(aBuilder, other)) {
    return false;
  }

  NS_ASSERTION(other->mReferenceFrame == mReferenceFrame,
               "Must have the same reference frame!");

  FrameProperties props = mScrolledFrame->Properties();
  props.Set(nsIFrame::ScrollLayerCount(),
    reinterpret_cast<void*>(GetScrollLayerCount() - 1));

  // Swap frames with the other item before doing MergeFrom.
  // XXX - This ensures that the frame associated with a scroll layer after
  // merging is the first, rather than the last. This tends to change less,
  // ensuring we're more likely to retain the associated gfx layer.
  // See Bug 729534 and Bug 731641.
  nsIFrame* tmp = mFrame;
  mFrame = other->mFrame;
  other->mFrame = tmp;
  MergeFromTrackingMergedFrames(other);
  return true;
}

void
PropagateClip(nsDisplayListBuilder* aBuilder, const DisplayItemClip& aClip,
              nsDisplayList* aList)
{
  for (nsDisplayItem* i = aList->GetBottom(); i != nullptr; i = i->GetAbove()) {
    DisplayItemClip clip(i->GetClip());
    clip.IntersectWith(aClip);
    i->SetClip(aBuilder, clip);
    nsDisplayList* list = i->GetSameCoordinateSystemChildren();
    if (list) {
      PropagateClip(aBuilder, aClip, list);
    }
  }
}

bool
nsDisplayScrollLayer::ShouldFlattenAway(nsDisplayListBuilder* aBuilder)
{
  bool badAbsPosClip = WouldCauseIncorrectClippingOnAbsPosItem(aBuilder, this);
  if (GetScrollLayerCount() > 1 || badAbsPosClip) {
    // Propagate our clip to our children. The clip for the scroll frame is
    // on this item, but not our child items so that they can draw non-visible
    // parts of the display port. But if we are flattening we failed and can't
    // draw the extra content, so it needs to be clipped.
    // But don't induce our clip on abs pos frames that we shouldn't be clipping.
    if (!badAbsPosClip) {
      PropagateClip(aBuilder, GetClip(), &mList);
    }
    return true;
  }
  if (mFrame != mScrolledFrame) {
    mMergedFrames.AppendElement(mFrame);
    mFrame = mScrolledFrame;
  }
  return false;
}

intptr_t
nsDisplayScrollLayer::GetScrollLayerCount()
{
  FrameProperties props = mScrolledFrame->Properties();
#ifdef DEBUG
  bool hasCount = false;
  intptr_t result = reinterpret_cast<intptr_t>(
    props.Get(nsIFrame::ScrollLayerCount(), &hasCount));
  // If this aborts, then the property was either not added before scroll
  // layers were created or the property was deleted to early. If the latter,
  // make sure that nsDisplayScrollInfoLayer is on the bottom of the list so
  // that it is processed last.
  NS_ABORT_IF_FALSE(hasCount, "nsDisplayScrollLayer should always be defined");
  return result;
#else
  return reinterpret_cast<intptr_t>(props.Get(nsIFrame::ScrollLayerCount()));
#endif
}

#ifdef MOZ_DUMP_PAINTING
void
nsDisplayScrollLayer::WriteDebugInfo(nsACString& aTo)
{
  aTo += nsPrintfCString(" (scrollframe %p scrolledframe %p)",
                         mScrollFrame, mScrolledFrame);
}
#endif

nsDisplayScrollInfoLayer::nsDisplayScrollInfoLayer(
  nsDisplayListBuilder* aBuilder,
  nsIFrame* aScrolledFrame,
  nsIFrame* aScrollFrame)
  : nsDisplayScrollLayer(aBuilder, aScrollFrame, aScrolledFrame, aScrollFrame)
{
#ifdef NS_BUILD_REFCNT_LOGGING
  MOZ_COUNT_CTOR(nsDisplayScrollInfoLayer);
#endif
}

nsDisplayScrollInfoLayer::~nsDisplayScrollInfoLayer()
{
  FrameProperties props = mScrolledFrame->Properties();
  props.Remove(nsIFrame::ScrollLayerCount());
  MOZ_COUNT_DTOR(nsDisplayScrollInfoLayer);
}

nsRect
nsDisplayScrollInfoLayer::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap)
{
  return nsDisplayWrapList::GetBounds(aBuilder, aSnap);
}

LayerState
nsDisplayScrollInfoLayer::GetLayerState(nsDisplayListBuilder* aBuilder,
                                        LayerManager* aManager,
                                        const ContainerLayerParameters& aParameters)
{
  return LAYER_ACTIVE_EMPTY;
}

bool
nsDisplayScrollInfoLayer::TryMerge(nsDisplayListBuilder* aBuilder,
                                   nsDisplayItem* aItem)
{
  return false;
}

bool
nsDisplayScrollInfoLayer::ShouldFlattenAway(nsDisplayListBuilder* aBuilder)
{
  // Layer metadata for a particular scroll frame needs to be unique. Only
  // one nsDisplayScrollLayer (with rendered content) or one
  // nsDisplayScrollInfoLayer (with only the metadata) should survive the
  // visibility computation.
  return GetScrollLayerCount() == 1;
}

nsDisplayZoom::nsDisplayZoom(nsDisplayListBuilder* aBuilder,
                             nsIFrame* aFrame, nsDisplayList* aList,
                             int32_t aAPD, int32_t aParentAPD,
                             uint32_t aFlags)
    : nsDisplaySubDocument(aBuilder, aFrame, aList, aFlags)
    , mAPD(aAPD), mParentAPD(aParentAPD) {
  MOZ_COUNT_CTOR(nsDisplayZoom);
}

#ifdef NS_BUILD_REFCNT_LOGGING
nsDisplayZoom::~nsDisplayZoom() {
  MOZ_COUNT_DTOR(nsDisplayZoom);
}
#endif

nsRect nsDisplayZoom::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap)
{
  nsRect bounds = nsDisplaySubDocument::GetBounds(aBuilder, aSnap);
  *aSnap = false;
  return bounds.ConvertAppUnitsRoundOut(mAPD, mParentAPD);
}

void nsDisplayZoom::HitTest(nsDisplayListBuilder *aBuilder,
                            const nsRect& aRect,
                            HitTestState *aState,
                            nsTArray<nsIFrame*> *aOutFrames)
{
  nsRect rect;
  // A 1x1 rect indicates we are just hit testing a point, so pass down a 1x1
  // rect as well instead of possibly rounding the width or height to zero.
  if (aRect.width == 1 && aRect.height == 1) {
    rect.MoveTo(aRect.TopLeft().ConvertAppUnits(mParentAPD, mAPD));
    rect.width = rect.height = 1;
  } else {
    rect = aRect.ConvertAppUnitsRoundOut(mParentAPD, mAPD);
  }
  mList.HitTest(aBuilder, rect, aState, aOutFrames);
}

void nsDisplayZoom::Paint(nsDisplayListBuilder* aBuilder,
                          nsRenderingContext* aCtx)
{
  mList.PaintForFrame(aBuilder, aCtx, mFrame, nsDisplayList::PAINT_DEFAULT);
}

bool nsDisplayZoom::ComputeVisibility(nsDisplayListBuilder *aBuilder,
                                      nsRegion *aVisibleRegion,
                                      const nsRect& aAllowVisibleRegionExpansion)
{
  // Convert the passed in visible region to our appunits.
  nsRegion visibleRegion;
  // mVisibleRect has been clipped to GetClippedBounds
  visibleRegion.And(*aVisibleRegion, mVisibleRect);
  visibleRegion = visibleRegion.ConvertAppUnitsRoundOut(mParentAPD, mAPD);
  nsRegion originalVisibleRegion = visibleRegion;

  nsRect transformedVisibleRect =
    mVisibleRect.ConvertAppUnitsRoundOut(mParentAPD, mAPD);
  nsRect allowExpansion =
    aAllowVisibleRegionExpansion.ConvertAppUnitsRoundIn(mParentAPD, mAPD);
  bool retval;
  // If we are to generate a scrollable layer we call
  // nsDisplaySubDocument::ComputeVisibility to make the necessary adjustments
  // for ComputeVisibility, it does all it's calculations in the child APD.
  bool usingDisplayPort =
    nsLayoutUtils::ViewportHasDisplayPort(mFrame->PresContext());
  if (!(mFlags & GENERATE_SCROLLABLE_LAYER) || !usingDisplayPort) {
    retval =
      mList.ComputeVisibilityForSublist(aBuilder, &visibleRegion,
                                        transformedVisibleRect,
                                        allowExpansion);
  } else {
    retval =
      nsDisplaySubDocument::ComputeVisibility(aBuilder, &visibleRegion,
                                              allowExpansion);
  }

  nsRegion removed;
  // removed = originalVisibleRegion - visibleRegion
  removed.Sub(originalVisibleRegion, visibleRegion);
  // Convert removed region to parent appunits.
  removed = removed.ConvertAppUnitsRoundIn(mAPD, mParentAPD);
  // aVisibleRegion = aVisibleRegion - removed (modulo any simplifications
  // SubtractFromVisibleRegion does)
  aBuilder->SubtractFromVisibleRegion(aVisibleRegion, removed);

  return retval;
}

///////////////////////////////////////////////////
// nsDisplayTransform Implementation
//

// Write #define UNIFIED_CONTINUATIONS here to have the transform property try
// to transform content with continuations as one unified block instead of
// several smaller ones.  This is currently disabled because it doesn't work
// correctly, since when the frames are initially being reflowed, their
// continuations all compute their bounding rects independently of each other
// and consequently get the wrong value.  Write #define DEBUG_HIT here to have
// the nsDisplayTransform class dump out a bunch of information about hit
// detection.
#undef  UNIFIED_CONTINUATIONS
#undef  DEBUG_HIT

/* Returns the bounds of a frame as defined for transforms.  If
 * UNIFIED_CONTINUATIONS is not defined, this is simply the frame's bounding
 * rectangle, translated to the origin. Otherwise, returns the smallest
 * rectangle containing a frame and all of its continuations.  For example, if
 * there is a <span> element with several continuations split over several
 * lines, this function will return the rectangle containing all of those
 * continuations.  This rectangle is relative to the origin of the frame's local
 * coordinate space.
 */
#ifndef UNIFIED_CONTINUATIONS

nsRect
nsDisplayTransform::GetFrameBoundsForTransform(const nsIFrame* aFrame)
{
  NS_PRECONDITION(aFrame, "Can't get the bounds of a nonexistent frame!");

  if (aFrame->GetStateBits() & NS_FRAME_SVG_LAYOUT) {
    // TODO: SVG needs to define what percentage translations resolve against.
    return nsRect();
  }

  return nsRect(nsPoint(0, 0), aFrame->GetSize());
}

#else

nsRect
nsDisplayTransform::GetFrameBoundsForTransform(const nsIFrame* aFrame)
{
  NS_PRECONDITION(aFrame, "Can't get the bounds of a nonexistent frame!");

  nsRect result;

  if (aFrame->GetStateBits() & NS_FRAME_SVG_LAYOUT) {
    // TODO: SVG needs to define what percentage translations resolve against.
    return result;
  }

  /* Iterate through the continuation list, unioning together all the
   * bounding rects.
   */
  for (const nsIFrame *currFrame = aFrame->FirstContinuation();
       currFrame != nullptr;
       currFrame = currFrame->GetNextContinuation())
    {
      /* Get the frame rect in local coordinates, then translate back to the
       * original coordinates.
       */
      result.UnionRect(result, nsRect(currFrame->GetOffsetTo(aFrame),
                                      currFrame->GetSize()));
    }

  return result;
}

#endif

nsDisplayTransform::nsDisplayTransform(nsDisplayListBuilder* aBuilder, nsIFrame *aFrame,
                                       nsDisplayList *aList, ComputeTransformFunction aTransformGetter, 
                                       uint32_t aIndex) 
  : nsDisplayItem(aBuilder, aFrame)
  , mStoredList(aBuilder, aFrame, aList)
  , mTransformGetter(aTransformGetter)
  , mIndex(aIndex)
{
  MOZ_COUNT_CTOR(nsDisplayTransform);
  NS_ABORT_IF_FALSE(aFrame, "Must have a frame!");
  NS_ABORT_IF_FALSE(!aFrame->IsTransformed(), "Can't specify a transform getter for a transformed frame!");
  mStoredList.SetClip(aBuilder, DisplayItemClip::NoClip());
}

nsDisplayTransform::nsDisplayTransform(nsDisplayListBuilder* aBuilder, nsIFrame *aFrame,
                                       nsDisplayList *aList, uint32_t aIndex) 
  : nsDisplayItem(aBuilder, aFrame)
  , mStoredList(aBuilder, aFrame, aList)
  , mTransformGetter(nullptr)
  , mIndex(aIndex)
{
  MOZ_COUNT_CTOR(nsDisplayTransform);
  NS_ABORT_IF_FALSE(aFrame, "Must have a frame!");
  mReferenceFrame = 
    aBuilder->FindReferenceFrameFor(GetTransformRootFrame(aFrame));
  mToReferenceFrame = aFrame->GetOffsetToCrossDoc(mReferenceFrame);
  mStoredList.SetClip(aBuilder, DisplayItemClip::NoClip());
}

nsDisplayTransform::nsDisplayTransform(nsDisplayListBuilder* aBuilder, nsIFrame *aFrame,
                                       nsDisplayItem *aItem, uint32_t aIndex)
  : nsDisplayItem(aBuilder, aFrame)
  , mStoredList(aBuilder, aFrame, aItem)
  , mTransformGetter(nullptr)
  , mIndex(aIndex)
{
  MOZ_COUNT_CTOR(nsDisplayTransform);
  NS_ABORT_IF_FALSE(aFrame, "Must have a frame!");
  mReferenceFrame =
    aBuilder->FindReferenceFrameFor(GetTransformRootFrame(aFrame));
  mToReferenceFrame = aFrame->GetOffsetToCrossDoc(mReferenceFrame);
  mStoredList.SetClip(aBuilder, DisplayItemClip::NoClip());
}

/* Returns the delta specified by the -moz-transform-origin property.
 * This is a positive delta, meaning that it indicates the direction to move
 * to get from (0, 0) of the frame to the transform origin.  This function is
 * called off the main thread.
 */
/* static */ gfxPoint3D
nsDisplayTransform::GetDeltaToTransformOrigin(const nsIFrame* aFrame,
                                              float aAppUnitsPerPixel,
                                              const nsRect* aBoundsOverride)
{
  NS_PRECONDITION(aFrame, "Can't get delta for a null frame!");
  NS_PRECONDITION(aFrame->IsTransformed() || aFrame->StyleDisplay()->BackfaceIsHidden(),
                  "Shouldn't get a delta for an untransformed frame!");

  if (!aFrame->IsTransformed()) {
    return gfxPoint3D();
  }

  /* For both of the coordinates, if the value of -moz-transform is a
   * percentage, it's relative to the size of the frame.  Otherwise, if it's
   * a distance, it's already computed for us!
   */
  const nsStyleDisplay* display = aFrame->StyleDisplay();
  nsRect boundingRect = (aBoundsOverride ? *aBoundsOverride :
                         nsDisplayTransform::GetFrameBoundsForTransform(aFrame));

  /* Allows us to access named variables by index. */
  float coords[3];
  const nscoord* dimensions[2] =
    {&boundingRect.width, &boundingRect.height};

  for (uint8_t index = 0; index < 2; ++index) {
    /* If the -moz-transform-origin specifies a percentage, take the percentage
     * of the size of the box.
     */
    const nsStyleCoord &coord = display->mTransformOrigin[index];
    if (coord.GetUnit() == eStyleUnit_Calc) {
      const nsStyleCoord::Calc *calc = coord.GetCalcValue();
      coords[index] =
        NSAppUnitsToFloatPixels(*dimensions[index], aAppUnitsPerPixel) *
          calc->mPercent +
        NSAppUnitsToFloatPixels(calc->mLength, aAppUnitsPerPixel);
    } else if (coord.GetUnit() == eStyleUnit_Percent) {
      coords[index] =
        NSAppUnitsToFloatPixels(*dimensions[index], aAppUnitsPerPixel) *
        coord.GetPercentValue();
    } else {
      NS_ABORT_IF_FALSE(coord.GetUnit() == eStyleUnit_Coord, "unexpected unit");
      coords[index] =
        NSAppUnitsToFloatPixels(coord.GetCoordValue(), aAppUnitsPerPixel);
    }
    if ((aFrame->GetStateBits() & NS_FRAME_SVG_LAYOUT) &&
        coord.GetUnit() != eStyleUnit_Percent) {
      // <length> values represent offsets from the origin of the SVG element's
      // user space, not the top left of its bounds, so we must adjust for that:
      nscoord offset =
        (index == 0) ? aFrame->GetPosition().x : aFrame->GetPosition().y;
      coords[index] -= NSAppUnitsToFloatPixels(offset, aAppUnitsPerPixel);
    }
  }

  coords[2] = NSAppUnitsToFloatPixels(display->mTransformOrigin[2].GetCoordValue(),
                                      aAppUnitsPerPixel);
  /* Adjust based on the origin of the rectangle. */
  coords[0] += NSAppUnitsToFloatPixels(boundingRect.x, aAppUnitsPerPixel);
  coords[1] += NSAppUnitsToFloatPixels(boundingRect.y, aAppUnitsPerPixel);

  return gfxPoint3D(coords[0], coords[1], coords[2]);
}

/* Returns the delta specified by the -moz-perspective-origin property.
 * This is a positive delta, meaning that it indicates the direction to move
 * to get from (0, 0) of the frame to the perspective origin. This function is
 * called off the main thread.
 */
/* static */ gfxPoint3D
nsDisplayTransform::GetDeltaToPerspectiveOrigin(const nsIFrame* aFrame,
                                                float aAppUnitsPerPixel)
{
  NS_PRECONDITION(aFrame, "Can't get delta for a null frame!");
  NS_PRECONDITION(aFrame->IsTransformed() || aFrame->StyleDisplay()->BackfaceIsHidden(),
                  "Shouldn't get a delta for an untransformed frame!");

  if (!aFrame->IsTransformed()) {
    return gfxPoint3D();
  }

  /* For both of the coordinates, if the value of -moz-perspective-origin is a
   * percentage, it's relative to the size of the frame.  Otherwise, if it's
   * a distance, it's already computed for us!
   */

  //TODO: Should this be using our bounds or the parent's bounds?
  // How do we handle aBoundsOverride in the latter case?
  nsIFrame* parent = aFrame->GetParentStyleContextFrame();
  if (!parent) {
    return gfxPoint3D();
  }
  const nsStyleDisplay* display = parent->StyleDisplay();
  nsRect boundingRect = nsDisplayTransform::GetFrameBoundsForTransform(parent);

  /* Allows us to access named variables by index. */
  gfxPoint3D result;
  result.z = 0.0f;
  gfxFloat* coords[2] = {&result.x, &result.y};
  const nscoord* dimensions[2] =
    {&boundingRect.width, &boundingRect.height};

  for (uint8_t index = 0; index < 2; ++index) {
    /* If the -moz-transform-origin specifies a percentage, take the percentage
     * of the size of the box.
     */
    const nsStyleCoord &coord = display->mPerspectiveOrigin[index];
    if (coord.GetUnit() == eStyleUnit_Calc) {
      const nsStyleCoord::Calc *calc = coord.GetCalcValue();
      *coords[index] =
        NSAppUnitsToFloatPixels(*dimensions[index], aAppUnitsPerPixel) *
          calc->mPercent +
        NSAppUnitsToFloatPixels(calc->mLength, aAppUnitsPerPixel);
    } else if (coord.GetUnit() == eStyleUnit_Percent) {
      *coords[index] =
        NSAppUnitsToFloatPixels(*dimensions[index], aAppUnitsPerPixel) *
        coord.GetPercentValue();
    } else {
      NS_ABORT_IF_FALSE(coord.GetUnit() == eStyleUnit_Coord, "unexpected unit");
      *coords[index] =
        NSAppUnitsToFloatPixels(coord.GetCoordValue(), aAppUnitsPerPixel);
    }
  }

  nsPoint parentOffset = aFrame->GetOffsetTo(parent);
  gfxPoint3D gfxOffset(
               NSAppUnitsToFloatPixels(parentOffset.x, aAppUnitsPerPixel),
               NSAppUnitsToFloatPixels(parentOffset.y, aAppUnitsPerPixel),
               0.0f);

  return result - gfxOffset;
}

nsDisplayTransform::FrameTransformProperties::FrameTransformProperties(const nsIFrame* aFrame,
                                                                       float aAppUnitsPerPixel,
                                                                       const nsRect* aBoundsOverride)
  : mFrame(aFrame)
  , mTransformList(aFrame->StyleDisplay()->mSpecifiedTransform)
  , mToTransformOrigin(GetDeltaToTransformOrigin(aFrame, aAppUnitsPerPixel, aBoundsOverride))
  , mToPerspectiveOrigin(GetDeltaToPerspectiveOrigin(aFrame, aAppUnitsPerPixel))
  , mChildPerspective(0)
{
  const nsStyleDisplay* parentDisp = nullptr;
  nsStyleContext* parentStyleContext = aFrame->StyleContext()->GetParent();
  if (parentStyleContext) {
    parentDisp = parentStyleContext->StyleDisplay();
  }
  if (parentDisp && parentDisp->mChildPerspective.GetUnit() == eStyleUnit_Coord) {
    mChildPerspective = parentDisp->mChildPerspective.GetCoordValue();
  }
}

/* Wraps up the -moz-transform matrix in a change-of-basis matrix pair that
 * translates from local coordinate space to transform coordinate space, then
 * hands it back.
 */
gfx3DMatrix
nsDisplayTransform::GetResultingTransformMatrix(const FrameTransformProperties& aProperties,
                                                const nsPoint& aOrigin,
                                                float aAppUnitsPerPixel,
                                                const nsRect* aBoundsOverride,
                                                nsIFrame** aOutAncestor)
{
  return GetResultingTransformMatrixInternal(aProperties, aOrigin, aAppUnitsPerPixel,
                                             aBoundsOverride, aOutAncestor);
}
 
gfx3DMatrix
nsDisplayTransform::GetResultingTransformMatrix(const nsIFrame* aFrame,
                                                const nsPoint& aOrigin,
                                                float aAppUnitsPerPixel,
                                                const nsRect* aBoundsOverride,
                                                nsIFrame** aOutAncestor)
{
  FrameTransformProperties props(aFrame,
                                 aAppUnitsPerPixel,
                                 aBoundsOverride);

  return GetResultingTransformMatrixInternal(props, aOrigin, aAppUnitsPerPixel, 
                                             aBoundsOverride, aOutAncestor);
}

gfx3DMatrix
nsDisplayTransform::GetResultingTransformMatrixInternal(const FrameTransformProperties& aProperties,
                                                        const nsPoint& aOrigin,
                                                        float aAppUnitsPerPixel,
                                                        const nsRect* aBoundsOverride,
                                                        nsIFrame** aOutAncestor)
{
  const nsIFrame *frame = aProperties.mFrame;

  if (aOutAncestor) {
    *aOutAncestor = nsLayoutUtils::GetCrossDocParentFrame(frame);
  }

  /* Account for the -moz-transform-origin property by translating the
   * coordinate space to the new origin.
   */
  gfxPoint3D newOrigin =
    gfxPoint3D(NSAppUnitsToFloatPixels(aOrigin.x, aAppUnitsPerPixel),
               NSAppUnitsToFloatPixels(aOrigin.y, aAppUnitsPerPixel),
               0.0f);

  /* Get the underlying transform matrix.  This requires us to get the
   * bounds of the frame.
   */
  nsRect bounds = (aBoundsOverride ? *aBoundsOverride :
                   nsDisplayTransform::GetFrameBoundsForTransform(frame));

  /* Get the matrix, then change its basis to factor in the origin. */
  bool dummy;
  gfx3DMatrix result;
  // Call IsSVGTransformed() regardless of the value of
  // disp->mSpecifiedTransform, since we still need any transformFromSVGParent.
  mozilla::gfx::Matrix svgTransform, transformFromSVGParent;
  bool hasSVGTransforms =
    frame && frame->IsSVGTransformed(&svgTransform, &transformFromSVGParent);
  /* Transformed frames always have a transform, or are preserving 3d (and might still have perspective!) */
  if (aProperties.mTransformList) {
    result = nsStyleTransformMatrix::ReadTransforms(aProperties.mTransformList->mHead,
                                                    frame ? frame->StyleContext() : nullptr,
                                                    frame ? frame->PresContext() : nullptr,
                                                    dummy, bounds, aAppUnitsPerPixel);
  } else if (hasSVGTransforms) {
    // Correct the translation components for zoom:
    float pixelsPerCSSPx = frame->PresContext()->AppUnitsPerCSSPixel() /
                             aAppUnitsPerPixel;
    svgTransform._31 *= pixelsPerCSSPx;
    svgTransform._32 *= pixelsPerCSSPx;
    result = gfx3DMatrix::From2D(ThebesMatrix(svgTransform));
  }

  if (hasSVGTransforms && !transformFromSVGParent.IsIdentity()) {
    // Correct the translation components for zoom:
    float pixelsPerCSSPx = frame->PresContext()->AppUnitsPerCSSPixel() /
                             aAppUnitsPerPixel;
    transformFromSVGParent._31 *= pixelsPerCSSPx;
    transformFromSVGParent._32 *= pixelsPerCSSPx;
    result = result * gfx3DMatrix::From2D(ThebesMatrix(transformFromSVGParent));
  }

  if (aProperties.mChildPerspective > 0.0) {
    gfx3DMatrix perspective;
    perspective._34 =
      -1.0 / NSAppUnitsToFloatPixels(aProperties.mChildPerspective, aAppUnitsPerPixel);
    /* At the point when perspective is applied, we have been translated to the transform origin.
     * The translation to the perspective origin is the difference between these values.
     */
    result = result * nsLayoutUtils::ChangeMatrixBasis(aProperties.mToPerspectiveOrigin - aProperties.mToTransformOrigin, perspective);
  }

  gfxPoint3D rounded(hasSVGTransforms ? newOrigin.x : NS_round(newOrigin.x),
                     hasSVGTransforms ? newOrigin.y : NS_round(newOrigin.y),
                     0);

  if (frame && frame->Preserves3D()) {
      // Include the transform set on our parent
      NS_ASSERTION(frame->GetParent() &&
                   frame->GetParent()->IsTransformed() &&
                   frame->GetParent()->Preserves3DChildren(),
                   "Preserve3D mismatch!");
      FrameTransformProperties props(frame->GetParent(),
                                     aAppUnitsPerPixel,
                                     nullptr);
      gfx3DMatrix parent =
        GetResultingTransformMatrixInternal(props,
                                            aOrigin - frame->GetPosition(),
                                            aAppUnitsPerPixel, nullptr, aOutAncestor);
      return nsLayoutUtils::ChangeMatrixBasis(rounded + aProperties.mToTransformOrigin, result) * parent;
  }

  return nsLayoutUtils::ChangeMatrixBasis
    (rounded + aProperties.mToTransformOrigin, result);
}

bool
nsDisplayOpacity::CanUseAsyncAnimations(nsDisplayListBuilder* aBuilder)
{
  if (ActiveLayerTracker::IsStyleAnimated(mFrame, eCSSProperty_opacity)) {
    return true;
  }

  if (nsLayoutUtils::IsAnimationLoggingEnabled()) {
    nsCString message;
    message.AppendLiteral("Performance warning: Async animation disabled because frame was not marked active for opacity animation");
    CommonElementAnimationData::LogAsyncAnimationFailure(message,
                                                         Frame()->GetContent());
  }
  return false;
}

bool
nsDisplayTransform::CanUseAsyncAnimations(nsDisplayListBuilder* aBuilder)
{
  return ShouldPrerenderTransformedContent(aBuilder,
                                           Frame(),
                                           nsLayoutUtils::IsAnimationLoggingEnabled());
}

/* static */ bool
nsDisplayTransform::ShouldPrerenderTransformedContent(nsDisplayListBuilder* aBuilder,
                                                      nsIFrame* aFrame,
                                                      bool aLogAnimations)
{
  // Elements whose transform has been modified recently, or which
  // have a compositor-animated transform, can be prerendered. An element
  // might have only just had its transform animated in which case
  // nsChangeHint_UpdateTransformLayer will not be present yet.
  if (!ActiveLayerTracker::IsStyleAnimated(aFrame, eCSSProperty_transform) &&
      (!aFrame->GetContent() ||
       !nsLayoutUtils::HasAnimationsForCompositor(aFrame->GetContent(),
                                                  eCSSProperty_transform))) {
    if (aLogAnimations) {
      nsCString message;
      message.AppendLiteral("Performance warning: Async animation disabled because frame was not marked active for transform animation");
      CommonElementAnimationData::LogAsyncAnimationFailure(message,
                                                           aFrame->GetContent());
    }
    return false;
  }

  nsSize refSize = aBuilder->RootReferenceFrame()->GetSize();
  // Only prerender if the transformed frame's size (in the reference
  // frames coordinate space) is <= the reference frame size (~viewport),
  // allowing a 1/8th fuzz factor for shadows, borders, etc.
  refSize += nsSize(refSize.width / 8, refSize.height / 8);
  nsRect frameRect = aFrame->GetVisualOverflowRectRelativeToSelf();

  frameRect =
    nsLayoutUtils::TransformFrameRectToAncestor(aFrame, frameRect,
                                                aBuilder->RootReferenceFrame());

  if (frameRect.Size() <= refSize) {
    return true;
  }

  if (aLogAnimations) {
    nsCString message;
    message.AppendLiteral("Performance warning: Async animation disabled because frame size (");
    message.AppendInt(nsPresContext::AppUnitsToIntCSSPixels(frameRect.width));
    message.AppendLiteral(", ");
    message.AppendInt(nsPresContext::AppUnitsToIntCSSPixels(frameRect.height));
    message.AppendLiteral(") is bigger than the viewport (");
    message.AppendInt(nsPresContext::AppUnitsToIntCSSPixels(refSize.width));
    message.AppendLiteral(", ");
    message.AppendInt(nsPresContext::AppUnitsToIntCSSPixels(refSize.height));
    message.AppendLiteral(")");
    CommonElementAnimationData::LogAsyncAnimationFailure(message,
                                                         aFrame->GetContent());
  }
  return false;
}

/* If the matrix is singular, or a hidden backface is shown, the frame won't be visible or hit. */
static bool IsFrameVisible(nsIFrame* aFrame, const gfx3DMatrix& aMatrix)
{
  if (aMatrix.IsSingular()) {
    return false;
  }
  if (aFrame->StyleDisplay()->mBackfaceVisibility == NS_STYLE_BACKFACE_VISIBILITY_HIDDEN &&
      aMatrix.IsBackfaceVisible()) {
    return false;
  }
  return true;
}

const gfx3DMatrix&
nsDisplayTransform::GetTransform()
{
  if (mTransform.IsIdentity()) {
    float scale = mFrame->PresContext()->AppUnitsPerDevPixel();
    gfxPoint3D newOrigin =
      gfxPoint3D(NSAppUnitsToFloatPixels(mToReferenceFrame.x, scale),
                 NSAppUnitsToFloatPixels(mToReferenceFrame.y, scale),
                  0.0f);
    if (mTransformGetter) {
      mTransform = mTransformGetter(mFrame, scale);
      mTransform = nsLayoutUtils::ChangeMatrixBasis(newOrigin, mTransform);
    } else {
      mTransform =
        GetResultingTransformMatrix(mFrame, ToReferenceFrame(), scale);

      /**
       * Shift the coorindates to be relative to our reference frame instead of relative to this frame.
       *  When we have preserve-3d, our reference frame is already guaranteed to be an ancestor of the
       * preserve-3d chain, so we only need to do this once.
       */
      bool hasSVGTransforms = mFrame->IsSVGTransformed();
      gfxPoint3D rounded(hasSVGTransforms ? newOrigin.x : NS_round(newOrigin.x), 
                         hasSVGTransforms ? newOrigin.y : NS_round(newOrigin.y), 
                         0);
      mTransform.Translate(rounded);
    }
  }
  return mTransform;
}

bool
nsDisplayTransform::ShouldBuildLayerEvenIfInvisible(nsDisplayListBuilder* aBuilder)
{
  return ShouldPrerenderTransformedContent(aBuilder, mFrame, false);
}

already_AddRefed<Layer> nsDisplayTransform::BuildLayer(nsDisplayListBuilder *aBuilder,
                                                       LayerManager *aManager,
                                                       const ContainerLayerParameters& aContainerParameters)
{
  const gfx3DMatrix& newTransformMatrix = GetTransform();

  if (mFrame->StyleDisplay()->mBackfaceVisibility == NS_STYLE_BACKFACE_VISIBILITY_HIDDEN &&
      newTransformMatrix.IsBackfaceVisible()) {
    return nullptr;
  }

  uint32_t flags = ShouldPrerenderTransformedContent(aBuilder, mFrame, false) ?
    FrameLayerBuilder::CONTAINER_NOT_CLIPPED_BY_ANCESTORS : 0;
  nsRefPtr<ContainerLayer> container = aManager->GetLayerBuilder()->
    BuildContainerLayerFor(aBuilder, aManager, mFrame, this, *mStoredList.GetChildren(),
                           aContainerParameters, &newTransformMatrix, flags);

  if (!container) {
    return nullptr;
  }

  // Add the preserve-3d flag for this layer, BuildContainerLayerFor clears all flags,
  // so we never need to explicitely unset this flag.
  if (mFrame->Preserves3D() || mFrame->Preserves3DChildren()) {
    container->SetContentFlags(container->GetContentFlags() | Layer::CONTENT_PRESERVE_3D);
  } else {
    container->SetContentFlags(container->GetContentFlags() & ~Layer::CONTENT_PRESERVE_3D);
  }

  nsDisplayListBuilder::AddAnimationsAndTransitionsToLayer(container, aBuilder,
                                                           this, mFrame,
                                                           eCSSProperty_transform);
  if (ShouldPrerenderTransformedContent(aBuilder, mFrame, false)) {
    container->SetUserData(nsIFrame::LayerIsPrerenderedDataKey(),
                           /*the value is irrelevant*/nullptr);
    container->SetContentFlags(container->GetContentFlags() | Layer::CONTENT_MAY_CHANGE_TRANSFORM);
  } else {
    container->RemoveUserData(nsIFrame::LayerIsPrerenderedDataKey());
    container->SetContentFlags(container->GetContentFlags() & ~Layer::CONTENT_MAY_CHANGE_TRANSFORM);
  }
  return container.forget();
}

nsDisplayItem::LayerState
nsDisplayTransform::GetLayerState(nsDisplayListBuilder* aBuilder,
                                  LayerManager* aManager,
                                  const ContainerLayerParameters& aParameters) {
  // If the transform is 3d, or the layer takes part in preserve-3d sorting
  // then we *always* want this to be an active layer.
  if (!GetTransform().Is2D() || mFrame->Preserves3D()) {
    return LAYER_ACTIVE_FORCE;
  }
  // Here we check if the *post-transform* bounds of this item are big enough
  // to justify an active layer.
  if (ActiveLayerTracker::IsStyleAnimated(mFrame, eCSSProperty_transform) &&
      !IsItemTooSmallForActiveLayer(this))
    return LAYER_ACTIVE;
  if (mFrame->GetContent()) {
    if (nsLayoutUtils::HasAnimationsForCompositor(mFrame->GetContent(),
                                                  eCSSProperty_transform)) {
      return LAYER_ACTIVE;
    }
  }

  const nsStyleDisplay* disp = mFrame->StyleDisplay();
  if ((disp->mWillChangeBitField & NS_STYLE_WILL_CHANGE_TRANSFORM)) {
    return LAYER_ACTIVE;
  }

  return mStoredList.RequiredLayerStateForChildren(aBuilder,
                                                   aManager,
                                                   aParameters,
                                                   *mStoredList.GetChildren(),
                                                   mFrame);
}

bool nsDisplayTransform::ComputeVisibility(nsDisplayListBuilder *aBuilder,
                                             nsRegion *aVisibleRegion,
                                             const nsRect& aAllowVisibleRegionExpansion)
{
  /* As we do this, we need to be sure to
   * untransform the visible rect, since we want everything that's painting to
   * think that it's painting in its original rectangular coordinate space.
   * If we can't untransform, take the entire overflow rect */
  nsRect untransformedVisibleRect;
  if (ShouldPrerenderTransformedContent(aBuilder, mFrame) ||
      !UntransformVisibleRect(aBuilder, &untransformedVisibleRect))
  {
    untransformedVisibleRect = mFrame->GetVisualOverflowRectRelativeToSelf();
  }
  nsRegion untransformedVisible = untransformedVisibleRect;
  // Call RecomputeVisiblity instead of ComputeVisibility since
  // nsDisplayItem::ComputeVisibility should only be called from
  // nsDisplayList::ComputeVisibility (which sets mVisibleRect on the item)
  mStoredList.RecomputeVisibility(aBuilder, &untransformedVisible);
  return true;
}

#ifdef DEBUG_HIT
#include <time.h>
#endif

/* HitTest does some fun stuff with matrix transforms to obtain the answer. */
void nsDisplayTransform::HitTest(nsDisplayListBuilder *aBuilder,
                                 const nsRect& aRect,
                                 HitTestState *aState,
                                 nsTArray<nsIFrame*> *aOutFrames)
{
  /* Here's how this works:
   * 1. Get the matrix.  If it's singular, abort (clearly we didn't hit
   *    anything).
   * 2. Invert the matrix.
   * 3. Use it to transform the rect into the correct space.
   * 4. Pass that rect down through to the list's version of HitTest.
   */
  // GetTransform always operates in dev pixels.
  float factor = mFrame->PresContext()->AppUnitsPerDevPixel();
  gfx3DMatrix matrix = GetTransform();

  if (!IsFrameVisible(mFrame, matrix)) {
    return;
  }

  /* We want to go from transformed-space to regular space.
   * Thus we have to invert the matrix, which normally does
   * the reverse operation (e.g. regular->transformed)
   */
  bool snap;
  nsRect childBounds = mStoredList.GetBounds(aBuilder, &snap);
  gfxRect childGfxBounds(NSAppUnitsToFloatPixels(childBounds.x, factor),
                         NSAppUnitsToFloatPixels(childBounds.y, factor),
                         NSAppUnitsToFloatPixels(childBounds.width, factor),
                         NSAppUnitsToFloatPixels(childBounds.height, factor));

  /* Now, apply the transform and pass it down the channel. */
  nsRect resultingRect;
  if (aRect.width == 1 && aRect.height == 1) {
    // Magic width/height indicating we're hit testing a point, not a rect
    gfxPoint point;
    if (!matrix.UntransformPoint(gfxPoint(NSAppUnitsToFloatPixels(aRect.x, factor),
                                          NSAppUnitsToFloatPixels(aRect.y, factor)),
                                 childGfxBounds,
                                 &point)) {
      return;
    }

    resultingRect = nsRect(NSFloatPixelsToAppUnits(float(point.x), factor),
                           NSFloatPixelsToAppUnits(float(point.y), factor),
                           1, 1);

  } else {
    gfxRect originalRect(NSAppUnitsToFloatPixels(aRect.x, factor),
                         NSAppUnitsToFloatPixels(aRect.y, factor),
                         NSAppUnitsToFloatPixels(aRect.width, factor),
                         NSAppUnitsToFloatPixels(aRect.height, factor));

    gfxRect rect = matrix.UntransformBounds(originalRect, childGfxBounds);

    resultingRect = nsRect(NSFloatPixelsToAppUnits(float(rect.X()), factor),
                           NSFloatPixelsToAppUnits(float(rect.Y()), factor),
                           NSFloatPixelsToAppUnits(float(rect.Width()), factor),
                           NSFloatPixelsToAppUnits(float(rect.Height()), factor));
  }

  if (resultingRect.IsEmpty()) {
    return;
  }


#ifdef DEBUG_HIT
  printf("Frame: %p\n", dynamic_cast<void *>(mFrame));
  printf("  Untransformed point: (%f, %f)\n", resultingRect.X(), resultingRect.Y());
  uint32_t originalFrameCount = aOutFrames.Length();
#endif

  mStoredList.HitTest(aBuilder, resultingRect, aState, aOutFrames);

#ifdef DEBUG_HIT
  if (originalFrameCount != aOutFrames.Length())
    printf("  Hit! Time: %f, first frame: %p\n", static_cast<double>(clock()),
           dynamic_cast<void *>(aOutFrames.ElementAt(0)));
  printf("=== end of hit test ===\n");
#endif

}

float
nsDisplayTransform::GetHitDepthAtPoint(nsDisplayListBuilder* aBuilder, const nsPoint& aPoint)
{
  // GetTransform always operates in dev pixels.
  float factor = mFrame->PresContext()->AppUnitsPerDevPixel();
  gfx3DMatrix matrix = GetTransform();

  NS_ASSERTION(IsFrameVisible(mFrame, matrix), "We can't have hit a frame that isn't visible!");

  bool snap;
  nsRect childBounds = mStoredList.GetBounds(aBuilder, &snap);
  gfxRect childGfxBounds(NSAppUnitsToFloatPixels(childBounds.x, factor),
                         NSAppUnitsToFloatPixels(childBounds.y, factor),
                         NSAppUnitsToFloatPixels(childBounds.width, factor),
                         NSAppUnitsToFloatPixels(childBounds.height, factor));

  gfxPoint point;
  DebugOnly<bool> result = matrix.UntransformPoint(gfxPoint(NSAppUnitsToFloatPixels(aPoint.x, factor),
                                                            NSAppUnitsToFloatPixels(aPoint.y, factor)),
                                                   childGfxBounds,
                                                   &point);
  NS_ASSERTION(result, "Why are we trying to get the depth for a point we didn't hit?");

  gfxPoint3D transformed = matrix.Transform3D(gfxPoint3D(point.x, point.y, 0));
  return transformed.z;
}

/* The bounding rectangle for the object is the overflow rectangle translated
 * by the reference point.
 */
nsRect nsDisplayTransform::GetBounds(nsDisplayListBuilder *aBuilder, bool* aSnap)
{
  nsRect untransformedBounds =
    ShouldPrerenderTransformedContent(aBuilder, mFrame) ?
    mFrame->GetVisualOverflowRectRelativeToSelf() :
    mStoredList.GetBounds(aBuilder, aSnap);
  *aSnap = false;
  // GetTransform always operates in dev pixels.
  float factor = mFrame->PresContext()->AppUnitsPerDevPixel();
  return nsLayoutUtils::MatrixTransformRect(untransformedBounds,
                                            GetTransform(),
                                            factor);
}

/* The transform is opaque iff the transform consists solely of scales and
 * translations and if the underlying content is opaque.  Thus if the transform
 * is of the form
 *
 * |a c e|
 * |b d f|
 * |0 0 1|
 *
 * We need b and c to be zero.
 *
 * We also need to check whether the underlying opaque content completely fills
 * our visible rect. We use UntransformRect which expands to the axis-aligned
 * bounding rect, but that's OK since if
 * mStoredList.GetVisibleRect().Contains(untransformedVisible), then it
 * certainly contains the actual (non-axis-aligned) untransformed rect.
 */
nsRegion nsDisplayTransform::GetOpaqueRegion(nsDisplayListBuilder *aBuilder,
                                             bool* aSnap)
{
  *aSnap = false;
  nsRect untransformedVisible;
  // If we're going to prerender all our content, pretend like we
  // don't have opqaue content so that everything under us is rendered
  // as well.  That will increase graphics memory usage if our frame
  // covers the entire window, but it allows our transform to be
  // updated extremely cheaply, without invalidating any other
  // content.
  if (ShouldPrerenderTransformedContent(aBuilder, mFrame) ||
      !UntransformVisibleRect(aBuilder, &untransformedVisible)) {
      return nsRegion();
  }

  const gfx3DMatrix& matrix = GetTransform();

  nsRegion result;
  gfxMatrix matrix2d;
  bool tmpSnap;
  if (matrix.Is2D(&matrix2d) &&
      matrix2d.PreservesAxisAlignedRectangles() &&
      mStoredList.GetOpaqueRegion(aBuilder, &tmpSnap).Contains(untransformedVisible)) {
    result = mVisibleRect;
  }
  return result;
}

/* The transform is uniform if it fills the entire bounding rect and the
 * wrapped list is uniform.  See GetOpaqueRegion for discussion of why this
 * works.
 */
bool nsDisplayTransform::IsUniform(nsDisplayListBuilder *aBuilder, nscolor* aColor)
{
  nsRect untransformedVisible;
  if (!UntransformVisibleRect(aBuilder, &untransformedVisible)) {
    return false;
  }
  const gfx3DMatrix& matrix = GetTransform();

  gfxMatrix matrix2d;
  return matrix.Is2D(&matrix2d) &&
         matrix2d.PreservesAxisAlignedRectangles() &&
         mStoredList.GetVisibleRect().Contains(untransformedVisible) &&
         mStoredList.IsUniform(aBuilder, aColor);
}

/* If UNIFIED_CONTINUATIONS is defined, we can merge two display lists that
 * share the same underlying content.  Otherwise, doing so results in graphical
 * glitches.
 */
#ifndef UNIFIED_CONTINUATIONS

bool
nsDisplayTransform::TryMerge(nsDisplayListBuilder *aBuilder,
                             nsDisplayItem *aItem)
{
  return false;
}

#else

bool
nsDisplayTransform::TryMerge(nsDisplayListBuilder *aBuilder,
                             nsDisplayItem *aItem)
{
  NS_PRECONDITION(aItem, "Why did you try merging with a null item?");
  NS_PRECONDITION(aBuilder, "Why did you try merging with a null builder?");

  /* Make sure that we're dealing with two transforms. */
  if (aItem->GetType() != TYPE_TRANSFORM)
    return false;

  /* Check to see that both frames are part of the same content. */
  if (aItem->Frame()->GetContent() != mFrame->GetContent())
    return false;

  if (aItem->GetClip() != GetClip())
    return false;

  /* Now, move everything over to this frame and signal that
   * we merged things!
   */
  mStoredList.MergeFrom(&static_cast<nsDisplayTransform*>(aItem)->mStoredList);
  return true;
}

#endif

/* TransformRect takes in as parameters a rectangle (in app space) and returns
 * the smallest rectangle (in app space) containing the transformed image of
 * that rectangle.  That is, it takes the four corners of the rectangle,
 * transforms them according to the matrix associated with the specified frame,
 * then returns the smallest rectangle containing the four transformed points.
 *
 * @param aUntransformedBounds The rectangle (in app units) to transform.
 * @param aFrame The frame whose transformation should be applied.
 * @param aOrigin The delta from the frame origin to the coordinate space origin
 * @param aBoundsOverride (optional) Force the frame bounds to be the
 *        specified bounds.
 * @return The smallest rectangle containing the image of the transformed
 *         rectangle.
 */
nsRect nsDisplayTransform::TransformRect(const nsRect &aUntransformedBounds,
                                         const nsIFrame* aFrame,
                                         const nsPoint &aOrigin,
                                         const nsRect* aBoundsOverride)
{
  NS_PRECONDITION(aFrame, "Can't take the transform based on a null frame!");

  float factor = aFrame->PresContext()->AppUnitsPerDevPixel();
  return nsLayoutUtils::MatrixTransformRect
    (aUntransformedBounds,
     GetResultingTransformMatrix(aFrame, aOrigin, factor, aBoundsOverride),
     factor);
}

nsRect nsDisplayTransform::TransformRectOut(const nsRect &aUntransformedBounds,
                                            const nsIFrame* aFrame,
                                            const nsPoint &aOrigin,
                                            const nsRect* aBoundsOverride)
{
  NS_PRECONDITION(aFrame, "Can't take the transform based on a null frame!");

  float factor = aFrame->PresContext()->AppUnitsPerDevPixel();
  return nsLayoutUtils::MatrixTransformRectOut
    (aUntransformedBounds,
     GetResultingTransformMatrix(aFrame, aOrigin, factor, aBoundsOverride),
     factor);
}

bool nsDisplayTransform::UntransformRect(const nsRect &aTransformedBounds,
                                         const nsRect &aChildBounds,
                                         const nsIFrame* aFrame,
                                         const nsPoint &aOrigin,
                                         nsRect *aOutRect)
{
  NS_PRECONDITION(aFrame, "Can't take the transform based on a null frame!");

  float factor = aFrame->PresContext()->AppUnitsPerDevPixel();

  gfx3DMatrix transform = GetResultingTransformMatrix(aFrame, aOrigin, factor, nullptr);
  if (transform.IsSingular()) {
    return false;
  }

  gfxRect result(NSAppUnitsToFloatPixels(aTransformedBounds.x, factor),
                 NSAppUnitsToFloatPixels(aTransformedBounds.y, factor),
                 NSAppUnitsToFloatPixels(aTransformedBounds.width, factor),
                 NSAppUnitsToFloatPixels(aTransformedBounds.height, factor));

  gfxRect childGfxBounds(NSAppUnitsToFloatPixels(aChildBounds.x, factor),
                         NSAppUnitsToFloatPixels(aChildBounds.y, factor),
                         NSAppUnitsToFloatPixels(aChildBounds.width, factor),
                         NSAppUnitsToFloatPixels(aChildBounds.height, factor));

  result = transform.UntransformBounds(result, childGfxBounds);
  *aOutRect = nsLayoutUtils::RoundGfxRectToAppRect(result, factor);
  return true;
}

bool nsDisplayTransform::UntransformVisibleRect(nsDisplayListBuilder* aBuilder,
                                                nsRect *aOutRect)
{
  const gfx3DMatrix& matrix = GetTransform();
  if (matrix.IsSingular())
    return false;

  // GetTransform always operates in dev pixels.
  float factor = mFrame->PresContext()->AppUnitsPerDevPixel();
  gfxRect result(NSAppUnitsToFloatPixels(mVisibleRect.x, factor),
                 NSAppUnitsToFloatPixels(mVisibleRect.y, factor),
                 NSAppUnitsToFloatPixels(mVisibleRect.width, factor),
                 NSAppUnitsToFloatPixels(mVisibleRect.height, factor));

  bool snap;
  nsRect childBounds = mStoredList.GetBounds(aBuilder, &snap);
  gfxRect childGfxBounds(NSAppUnitsToFloatPixels(childBounds.x, factor),
                         NSAppUnitsToFloatPixels(childBounds.y, factor),
                         NSAppUnitsToFloatPixels(childBounds.width, factor),
                         NSAppUnitsToFloatPixels(childBounds.height, factor));

  /* We want to untransform the matrix, so invert the transformation first! */
  result = matrix.UntransformBounds(result, childGfxBounds);

  *aOutRect = nsLayoutUtils::RoundGfxRectToAppRect(result, factor);

  return true;
}

nsDisplaySVGEffects::nsDisplaySVGEffects(nsDisplayListBuilder* aBuilder,
                                         nsIFrame* aFrame, nsDisplayList* aList)
    : nsDisplayWrapList(aBuilder, aFrame, aList),
      mEffectsBounds(aFrame->GetVisualOverflowRectRelativeToSelf())
{
  MOZ_COUNT_CTOR(nsDisplaySVGEffects);
}

#ifdef NS_BUILD_REFCNT_LOGGING
nsDisplaySVGEffects::~nsDisplaySVGEffects()
{
  MOZ_COUNT_DTOR(nsDisplaySVGEffects);
}
#endif

nsRegion nsDisplaySVGEffects::GetOpaqueRegion(nsDisplayListBuilder* aBuilder,
                                              bool* aSnap)
{
  *aSnap = false;
  return nsRegion();
}

void
nsDisplaySVGEffects::HitTest(nsDisplayListBuilder* aBuilder, const nsRect& aRect,
                             HitTestState* aState, nsTArray<nsIFrame*> *aOutFrames)
{
  nsPoint rectCenter(aRect.x + aRect.width / 2, aRect.y + aRect.height / 2);
  if (nsSVGIntegrationUtils::HitTestFrameForEffects(mFrame,
      rectCenter - ToReferenceFrame())) {
    mList.HitTest(aBuilder, aRect, aState, aOutFrames);
  }
}

void
nsDisplaySVGEffects::PaintAsLayer(nsDisplayListBuilder* aBuilder,
                                  nsRenderingContext* aCtx,
                                  LayerManager* aManager)
{
  nsSVGIntegrationUtils::PaintFramesWithEffects(aCtx, mFrame,
                                                mVisibleRect,
                                                aBuilder, aManager);
}

LayerState
nsDisplaySVGEffects::GetLayerState(nsDisplayListBuilder* aBuilder,
                                   LayerManager* aManager,
                                   const ContainerLayerParameters& aParameters)
{
  return LAYER_SVG_EFFECTS;
}

already_AddRefed<Layer>
nsDisplaySVGEffects::BuildLayer(nsDisplayListBuilder* aBuilder,
                                LayerManager* aManager,
                                const ContainerLayerParameters& aContainerParameters)
{
  const nsIContent* content = mFrame->GetContent();
  bool hasSVGLayout = (mFrame->GetStateBits() & NS_FRAME_SVG_LAYOUT);
  if (hasSVGLayout) {
    nsISVGChildFrame *svgChildFrame = do_QueryFrame(mFrame);
    if (!svgChildFrame || !mFrame->GetContent()->IsSVG()) {
      NS_ASSERTION(false, "why?");
      return nullptr;
    }
    if (!static_cast<const nsSVGElement*>(content)->HasValidDimensions()) {
      return nullptr; // The SVG spec says not to draw filters for this
    }
  }

  float opacity = mFrame->StyleDisplay()->mOpacity;
  if (opacity == 0.0f)
    return nullptr;

  nsIFrame* firstFrame =
    nsLayoutUtils::FirstContinuationOrIBSplitSibling(mFrame);
  nsSVGEffects::EffectProperties effectProperties =
    nsSVGEffects::GetEffectProperties(firstFrame);

  bool isOK = effectProperties.HasNoFilterOrHasValidFilter();
  effectProperties.GetClipPathFrame(&isOK);
  effectProperties.GetMaskFrame(&isOK);

  if (!isOK) {
    return nullptr;
  }

  ContainerLayerParameters newContainerParameters = aContainerParameters;
  if (effectProperties.HasValidFilter()) {
    newContainerParameters.mDisableSubpixelAntialiasingInDescendants = true;
  }

  nsRefPtr<ContainerLayer> container = aManager->GetLayerBuilder()->
    BuildContainerLayerFor(aBuilder, aManager, mFrame, this, mList,
                           newContainerParameters, nullptr);

  return container.forget();
}

bool nsDisplaySVGEffects::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                              nsRegion* aVisibleRegion,
                                              const nsRect& aAllowVisibleRegionExpansion) {
  nsPoint offset = ToReferenceFrame();
  nsRect dirtyRect =
    nsSVGIntegrationUtils::GetRequiredSourceForInvalidArea(mFrame,
                                                           mVisibleRect - offset) +
    offset;

  // Our children may be made translucent or arbitrarily deformed so we should
  // not allow them to subtract area from aVisibleRegion.
  nsRegion childrenVisible(dirtyRect);
  nsRect r = dirtyRect.Intersect(mList.GetBounds(aBuilder));
  mList.ComputeVisibilityForSublist(aBuilder, &childrenVisible, r, nsRect());
  return true;
}

bool nsDisplaySVGEffects::TryMerge(nsDisplayListBuilder* aBuilder, nsDisplayItem* aItem)
{
  if (aItem->GetType() != TYPE_SVG_EFFECTS)
    return false;
  // items for the same content element should be merged into a single
  // compositing group
  // aItem->GetUnderlyingFrame() returns non-null because it's nsDisplaySVGEffects
  if (aItem->Frame()->GetContent() != mFrame->GetContent())
    return false;
  if (aItem->GetClip() != GetClip())
    return false;
  nsDisplaySVGEffects* other = static_cast<nsDisplaySVGEffects*>(aItem);
  MergeFromTrackingMergedFrames(other);
  mEffectsBounds.UnionRect(mEffectsBounds,
    other->mEffectsBounds + other->mFrame->GetOffsetTo(mFrame));
  return true;
}

#ifdef MOZ_DUMP_PAINTING
void
nsDisplaySVGEffects::PrintEffects(nsACString& aTo)
{
  nsIFrame* firstFrame =
    nsLayoutUtils::FirstContinuationOrIBSplitSibling(mFrame);
  nsSVGEffects::EffectProperties effectProperties =
    nsSVGEffects::GetEffectProperties(firstFrame);
  bool isOK = true;
  nsSVGClipPathFrame *clipPathFrame = effectProperties.GetClipPathFrame(&isOK);
  bool first = true;
  aTo += " effects=(";
  if (mFrame->StyleDisplay()->mOpacity != 1.0f) {
    first = false;
    aTo += nsPrintfCString("opacity(%f)", mFrame->StyleDisplay()->mOpacity);
  }
  if (clipPathFrame) {
    if (!first) {
      aTo += ", ";
    }
    aTo += nsPrintfCString("clip(%s)", clipPathFrame->IsTrivial() ? "trivial" : "non-trivial");
    first = false;
  }
  if (effectProperties.HasValidFilter()) {
    if (!first) {
      aTo += ", ";
    }
    aTo += "filter";
    first = false;
  }
  if (effectProperties.GetMaskFrame(&isOK)) {
    if (!first) {
      aTo += ", ";
    }
    aTo += "mask";
  }
  aTo += ")";
}
#endif