layout/painting/nsDisplayList.cpp
author Botond Ballo <botond@mozilla.com>
Fri, 01 Feb 2019 20:31:10 +0000
changeset 456490 509edb594bdbf3a8dffe7ffeeb31430a89c176e6
parent 456489 eca791db896743b462a82e3808d9f90efb7a2042
child 456492 352baaa37697490a3604e8725610e273b2744a0e
permissions -rw-r--r--
Bug 1521644 - Factor out a helper function to serialize a display list collection into a display list. r=mattwoodrow Differential Revision: https://phabricator.services.mozilla.com/D17852

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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 "nsDisplayList.h"

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

#include "gfxContext.h"
#include "gfxUtils.h"
#include "mozilla/dom/TabChild.h"
#include "mozilla/dom/HTMLCanvasElement.h"
#include "mozilla/dom/KeyframeEffect.h"
#include "mozilla/dom/Selection.h"
#include "mozilla/dom/ServiceWorkerRegistrar.h"
#include "mozilla/dom/ServiceWorkerRegistration.h"
#include "mozilla/dom/SVGElement.h"
#include "mozilla/gfx/2D.h"
#include "mozilla/layers/PLayerTransaction.h"
#include "mozilla/ShapeUtils.h"
#include "nsCSSRendering.h"
#include "nsCSSRenderingGradients.h"
#include "nsISelectionController.h"
#include "nsIPresShell.h"
#include "nsRegion.h"
#include "nsStyleStructInlines.h"
#include "nsStyleTransformMatrix.h"
#include "nsTransitionManager.h"
#include "gfxMatrix.h"
#include "gfxPrefs.h"
#include "nsSVGIntegrationUtils.h"
#include "nsSVGUtils.h"
#include "nsLayoutUtils.h"
#include "nsIScrollableFrame.h"
#include "nsIFrameInlines.h"
#include "nsStyleConsts.h"
#include "BorderConsts.h"
#include "LayerTreeInvalidation.h"
#include "mozilla/MathAlgorithms.h"

#include "imgIContainer.h"
#include "BasicLayers.h"
#include "nsBoxFrame.h"
#include "nsImageFrame.h"
#include "nsSubDocumentFrame.h"
#include "SVGObserverUtils.h"
#include "nsSVGClipPathFrame.h"
#include "GeckoProfiler.h"
#include "nsViewManager.h"
#include "ImageLayers.h"
#include "ImageContainer.h"
#include "nsCanvasFrame.h"
#include "StickyScrollContainer.h"
#include "mozilla/AnimationPerformanceWarning.h"
#include "mozilla/AnimationUtils.h"
#include "mozilla/AutoRestore.h"
#include "mozilla/EffectCompositor.h"
#include "mozilla/EffectSet.h"
#include "mozilla/EventStates.h"
#include "mozilla/LookAndFeel.h"
#include "mozilla/OperatorNewExtensions.h"
#include "mozilla/PendingAnimationTracker.h"
#include "mozilla/Preferences.h"
#include "mozilla/StyleAnimationValue.h"
#include "mozilla/ServoBindings.h"
#include "mozilla/Telemetry.h"
#include "mozilla/UniquePtr.h"
#include "mozilla/Unused.h"
#include "mozilla/ViewportFrame.h"
#include "mozilla/gfx/gfxVars.h"
#include "ActiveLayerTracker.h"
#include "nsPrintfCString.h"
#include "UnitTransforms.h"
#include "LayersLogging.h"
#include "FrameLayerBuilder.h"
#include "mozilla/EventStateManager.h"
#include "nsCaret.h"
#include "nsDOMTokenList.h"
#include "nsCSSProps.h"
#include "nsSVGMaskFrame.h"
#include "nsTableCellFrame.h"
#include "nsTableColFrame.h"
#include "nsTextFrame.h"
#include "nsSliderFrame.h"
#include "ClientLayerManager.h"
#include "mozilla/layers/RenderRootStateManager.h"
#include "mozilla/layers/StackingContextHelper.h"
#include "mozilla/layers/WebRenderBridgeChild.h"
#include "mozilla/layers/WebRenderLayerManager.h"
#include "mozilla/layers/WebRenderMessages.h"
#include "mozilla/layers/WebRenderScrollData.h"

using namespace mozilla;
using namespace mozilla::layers;
using namespace mozilla::dom;
using namespace mozilla::layout;
using namespace mozilla::gfx;

typedef ScrollableLayerGuid::ViewID ViewID;
typedef nsStyleTransformMatrix::TransformReferenceBox TransformReferenceBox;

#ifdef DEBUG
static bool SpammyLayoutWarningsEnabled() {
  static bool sValue = false;
  static bool sValueInitialized = false;

  if (!sValueInitialized) {
    Preferences::GetBool("layout.spammy_warnings.enabled", &sValue);
    sValueInitialized = true;
  }

  return sValue;
}
#endif

#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
void AssertUniqueItem(nsDisplayItem* aItem) {
  nsIFrame::DisplayItemArray* items =
      aItem->Frame()->GetProperty(nsIFrame::DisplayItems());
  if (!items) {
    return;
  }
  for (nsDisplayItem* i : *items) {
    if (i != aItem && !i->HasDeletedFrame() && i->Frame() == aItem->Frame() &&
        i->GetPerFrameKey() == aItem->GetPerFrameKey()) {
      if (i->mPreProcessedItem) {
        continue;
      }
      MOZ_DIAGNOSTIC_ASSERT(false, "Duplicate display item!");
    }
  }
}
#endif

/* static */ bool ActiveScrolledRoot::IsAncestor(
    const ActiveScrolledRoot* aAncestor,
    const ActiveScrolledRoot* aDescendant) {
  if (!aAncestor) {
    // nullptr is the root
    return true;
  }
  if (Depth(aAncestor) > Depth(aDescendant)) {
    return false;
  }
  const ActiveScrolledRoot* asr = aDescendant;
  while (asr) {
    if (asr == aAncestor) {
      return true;
    }
    asr = asr->mParent;
  }
  return false;
}

/* static */ nsCString ActiveScrolledRoot::ToString(
    const ActiveScrolledRoot* aActiveScrolledRoot) {
  nsAutoCString str;
  for (auto* asr = aActiveScrolledRoot; asr; asr = asr->mParent) {
    str.AppendPrintf("<0x%p>", asr->mScrollableFrame);
    if (asr->mParent) {
      str.AppendLiteral(", ");
    }
  }
  return std::move(str);
}

static inline CSSAngle MakeCSSAngle(const nsCSSValue& aValue) {
  return CSSAngle(aValue.GetAngleValue(), aValue.GetUnit());
}

static void AddTransformFunctions(
    const nsCSSValueList* aList, mozilla::ComputedStyle* aStyle,
    nsPresContext* aPresContext, TransformReferenceBox& aRefBox,
    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();
    switch (nsStyleTransformMatrix::TransformFunctionOf(array)) {
      case eCSSKeyword_rotatex: {
        CSSAngle theta = MakeCSSAngle(array->Item(1));
        aFunctions.AppendElement(RotationX(theta));
        break;
      }
      case eCSSKeyword_rotatey: {
        CSSAngle theta = MakeCSSAngle(array->Item(1));
        aFunctions.AppendElement(RotationY(theta));
        break;
      }
      case eCSSKeyword_rotatez: {
        CSSAngle theta = MakeCSSAngle(array->Item(1));
        aFunctions.AppendElement(RotationZ(theta));
        break;
      }
      case eCSSKeyword_rotate: {
        CSSAngle theta = MakeCSSAngle(array->Item(1));
        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();
        CSSAngle theta = MakeCSSAngle(array->Item(4));
        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), &aRefBox, &TransformReferenceBox::Width);
        aFunctions.AppendElement(Translation(x, 0, 0));
        break;
      }
      case eCSSKeyword_translatey: {
        double y = nsStyleTransformMatrix::ProcessTranslatePart(
            array->Item(1), &aRefBox, &TransformReferenceBox::Height);
        aFunctions.AppendElement(Translation(0, y, 0));
        break;
      }
      case eCSSKeyword_translatez: {
        double z = nsStyleTransformMatrix::ProcessTranslatePart(array->Item(1),
                                                                nullptr);
        aFunctions.AppendElement(Translation(0, 0, z));
        break;
      }
      case eCSSKeyword_translate: {
        double x = nsStyleTransformMatrix::ProcessTranslatePart(
            array->Item(1), &aRefBox, &TransformReferenceBox::Width);
        // translate(x) is shorthand for translate(x, 0)
        double y = 0;
        if (array->Count() == 3) {
          y = nsStyleTransformMatrix::ProcessTranslatePart(
              array->Item(2), &aRefBox, &TransformReferenceBox::Height);
        }
        aFunctions.AppendElement(Translation(x, y, 0));
        break;
      }
      case eCSSKeyword_translate3d: {
        double x = nsStyleTransformMatrix::ProcessTranslatePart(
            array->Item(1), &aRefBox, &TransformReferenceBox::Width);
        double y = nsStyleTransformMatrix::ProcessTranslatePart(
            array->Item(2), &aRefBox, &TransformReferenceBox::Height);
        double z = nsStyleTransformMatrix::ProcessTranslatePart(array->Item(3),
                                                                nullptr);

        aFunctions.AppendElement(Translation(x, y, z));
        break;
      }
      case eCSSKeyword_skewx: {
        CSSAngle x = MakeCSSAngle(array->Item(1));
        aFunctions.AppendElement(SkewX(x));
        break;
      }
      case eCSSKeyword_skewy: {
        CSSAngle y = MakeCSSAngle(array->Item(1));
        aFunctions.AppendElement(SkewY(y));
        break;
      }
      case eCSSKeyword_skew: {
        CSSAngle x = MakeCSSAngle(array->Item(1));
        // skew(x) is shorthand for skew(x, 0)
        CSSAngle y(0.0f, eCSSUnit_Degree);
        if (array->Count() == 3) {
          y = MakeCSSAngle(array->Item(2));
        }
        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 = ProcessTranslatePart(array->Item(5), &aRefBox,
                                          &TransformReferenceBox::Width);
        matrix._42 = ProcessTranslatePart(array->Item(6), &aRefBox,
                                          &TransformReferenceBox::Height);
        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 = ProcessTranslatePart(array->Item(13), &aRefBox,
                                          &TransformReferenceBox::Width);
        matrix._42 = ProcessTranslatePart(array->Item(14), &aRefBox,
                                          &TransformReferenceBox::Height);
        matrix._43 = ProcessTranslatePart(array->Item(15), &aRefBox, nullptr);
        matrix._44 = array->Item(16).GetFloatValue();
        aFunctions.AppendElement(TransformMatrix(matrix));
        break;
      }
      case eCSSKeyword_interpolatematrix: {
        Matrix4x4 matrix;
        nsStyleTransformMatrix::ProcessInterpolateMatrix(matrix, array,
                                                         aRefBox);
        aFunctions.AppendElement(TransformMatrix(matrix));
        break;
      }
      case eCSSKeyword_accumulatematrix: {
        Matrix4x4 matrix;
        nsStyleTransformMatrix::ProcessAccumulateMatrix(matrix, array, aRefBox);
        aFunctions.AppendElement(TransformMatrix(matrix));
        break;
      }
      case eCSSKeyword_perspective: {
        aFunctions.AppendElement(Perspective(array->Item(1).GetFloatValue()));
        break;
      }
      default:
        NS_ERROR("Function not handled yet!");
    }
  }
}

static void AddTransformFunctions(const nsCSSValueSharedList* aList,
                                  const nsIFrame* aFrame,
                                  TransformReferenceBox& aRefBox,
                                  layers::Animatable& aAnimatable) {
  MOZ_ASSERT(aList->mHead);
  AddTransformFunctions(aList->mHead, aFrame->Style(), aFrame->PresContext(),
                        aRefBox, aAnimatable.get_ArrayOfTransformFunction());
}

static TimingFunction ToTimingFunction(
    const Maybe<ComputedTimingFunction>& aCTF) {
  if (aCTF.isNothing()) {
    return TimingFunction(null_t());
  }

  if (aCTF->HasSpline()) {
    const SMILKeySpline* spline = aCTF->GetFunction();
    return TimingFunction(CubicBezierFunction(spline->X1(), spline->Y1(),
                                              spline->X2(), spline->Y2()));
  }

  return TimingFunction(StepFunction(
      aCTF->GetSteps().mSteps, static_cast<uint8_t>(aCTF->GetSteps().mPos)));
}

static void SetAnimatable(nsCSSPropertyID aProperty,
                          const AnimationValue& aAnimationValue,
                          nsIFrame* aFrame, TransformReferenceBox& aRefBox,
                          layers::Animatable& aAnimatable) {
  MOZ_ASSERT(aFrame);

  if (aAnimationValue.IsNull()) {
    aAnimatable = null_t();
    return;
  }

  switch (aProperty) {
    case eCSSProperty_background_color: {
      // We don't support color animation on the compositor yet so that we can
      // resolve currentColor at this moment.
      nscolor foreground;
      if (aFrame->Style()->RelevantLinkVisited()) {
        if (ComputedStyle* styleIfVisited =
                aFrame->Style()->GetStyleIfVisited()) {
          foreground = styleIfVisited->StyleColor()->mColor;
        } else {
          foreground = aFrame->Style()->StyleColor()->mColor;
        }
      } else {
        foreground = aFrame->Style()->StyleColor()->mColor;
      }
      aAnimatable = aAnimationValue.GetColor(foreground);
      break;
    }
    case eCSSProperty_opacity:
      aAnimatable = aAnimationValue.GetOpacity();
      break;
    case eCSSProperty_transform: {
      aAnimatable = InfallibleTArray<TransformFunction>();
      MOZ_ASSERT(aAnimationValue.mServo);
      RefPtr<nsCSSValueSharedList> list;
      Servo_AnimationValue_GetTransform(aAnimationValue.mServo, &list);
      AddTransformFunctions(list, aFrame, aRefBox, aAnimatable);
      break;
    }
    default:
      MOZ_ASSERT_UNREACHABLE("Unsupported property");
  }
}

enum class Send {
  NextTransaction,
  Immediate,
};
static void AddAnimationForProperty(nsIFrame* aFrame,
                                    const AnimationProperty& aProperty,
                                    dom::Animation* aAnimation,
                                    AnimationInfo& aAnimationInfo,
                                    AnimationData& aData, Send aSendFlag) {
  MOZ_ASSERT(aAnimation->GetEffect(),
             "Should not be adding an animation without an effect");
  MOZ_ASSERT(!aAnimation->GetCurrentOrPendingStartTime().IsNull() ||
                 !aAnimation->IsPlaying() ||
                 (aAnimation->GetTimeline() &&
                  aAnimation->GetTimeline()->TracksWallclockTime()),
             "If the animation has an unresolved start time it should either"
             " be static (so we don't need a start time) or else have a"
             " timeline capable of converting TimeStamps (so we can calculate"
             " one later");

  layers::Animation* animation =
      (aSendFlag == Send::NextTransaction)
          ? aAnimationInfo.AddAnimationForNextTransaction()
          : aAnimationInfo.AddAnimation();

  const TimingParams& timing = aAnimation->GetEffect()->SpecifiedTiming();

  // If we are starting a new transition that replaces an existing transition
  // running on the compositor, it is possible that the animation on the
  // compositor will have advanced ahead of the main thread. If we use as
  // the starting point of the new transition, the current value of the
  // replaced transition as calculated on the main thread using the refresh
  // driver time, the new transition will jump when it starts. Instead, we
  // re-calculate the starting point of the new transition by applying the
  // current TimeStamp to the parameters of the replaced transition.
  //
  // We need to do this here, rather than when we generate the new transition,
  // since after generating the new transition other requestAnimationFrame
  // callbacks may run that introduce further lag between the main thread and
  // the compositor.
  if (aAnimation->AsCSSTransition() && aAnimation->GetEffect() &&
      aAnimation->GetEffect()->AsTransition()) {
    // We update startValue from the replaced transition only if the effect is
    // an ElementPropertyTransition.
    aAnimation->GetEffect()
        ->AsTransition()
        ->UpdateStartValueFromReplacedTransition();
  }

  animation->originTime() =
      !aAnimation->GetTimeline()
          ? TimeStamp()
          : aAnimation->GetTimeline()->ToTimeStamp(TimeDuration());

  Nullable<TimeDuration> startTime = aAnimation->GetCurrentOrPendingStartTime();
  if (startTime.IsNull()) {
    animation->startTime() = null_t();
  } else {
    animation->startTime() = startTime.Value();
  }

  animation->holdTime() = aAnimation->GetCurrentTimeAsDuration().Value();

  const ComputedTiming computedTiming =
      aAnimation->GetEffect()->GetComputedTiming();
  animation->delay() = timing.Delay();
  animation->endDelay() = timing.EndDelay();
  animation->duration() = computedTiming.mDuration;
  animation->iterations() = computedTiming.mIterations;
  animation->iterationStart() = computedTiming.mIterationStart;
  animation->direction() = static_cast<uint8_t>(timing.Direction());
  animation->fillMode() = static_cast<uint8_t>(computedTiming.mFill);
  animation->property() = aProperty.mProperty;
  animation->playbackRate() = aAnimation->CurrentOrPendingPlaybackRate();
  animation->previousPlaybackRate() =
      aAnimation->HasPendingPlaybackRate()
          ? aAnimation->PlaybackRate()
          : std::numeric_limits<float>::quiet_NaN();
  animation->data() = aData;
  animation->easingFunction() = ToTimingFunction(timing.TimingFunction());
  animation->iterationComposite() = static_cast<uint8_t>(
      aAnimation->GetEffect()->AsKeyframeEffect()->IterationComposite());
  animation->isNotPlaying() = !aAnimation->IsPlaying();

  TransformReferenceBox refBox(aFrame);

  // If the animation is additive or accumulates, we need to pass its base value
  // to the compositor.

  AnimationValue baseStyle =
      aAnimation->GetEffect()->AsKeyframeEffect()->BaseStyle(
          aProperty.mProperty);
  if (!baseStyle.IsNull()) {
    SetAnimatable(aProperty.mProperty, baseStyle, aFrame, refBox,
                  animation->baseStyle());
  } else {
    animation->baseStyle() = null_t();
  }

  for (uint32_t segIdx = 0; segIdx < aProperty.mSegments.Length(); segIdx++) {
    const AnimationPropertySegment& segment = aProperty.mSegments[segIdx];

    AnimationSegment* animSegment = animation->segments().AppendElement();
    SetAnimatable(aProperty.mProperty, segment.mFromValue, aFrame, refBox,
                  animSegment->startState());
    SetAnimatable(aProperty.mProperty, segment.mToValue, aFrame, refBox,
                  animSegment->endState());

    animSegment->startPortion() = segment.mFromKey;
    animSegment->endPortion() = segment.mToKey;
    animSegment->startComposite() =
        static_cast<uint8_t>(segment.mFromComposite);
    animSegment->endComposite() = static_cast<uint8_t>(segment.mToComposite);
    animSegment->sampleFn() = ToTimingFunction(segment.mTimingFunction);
  }
}

static void AddAnimationsForProperty(
    nsIFrame* aFrame, nsDisplayListBuilder* aBuilder, nsDisplayItem* aItem,
    nsCSSPropertyID aProperty, AnimationInfo& aAnimationInfo, Send aSendFlag,
    layers::LayersBackend aLayersBackend) {
  if (aSendFlag == Send::NextTransaction) {
    aAnimationInfo.ClearAnimationsForNextTransaction();
  } else {
    aAnimationInfo.ClearAnimations();
  }

  nsIFrame* styleFrame = nsLayoutUtils::GetStyleFrame(aFrame);
  if (!styleFrame) {
    return;
  }

  // Update the animation generation on the layer. We need to do this before
  // any early returns since even if we don't add any animations to the
  // layer, we still need to mark it as up-to-date with regards to animations.
  // Otherwise, in RestyleManager we'll notice the discrepancy between the
  // animation generation numbers and update the layer indefinitely.
  // Note that EffectSet::GetEffectSet expects to work with the style frame
  // instead of the primary frame.
  EffectSet* effects = EffectSet::GetEffectSet(styleFrame);
  uint64_t animationGeneration =
      effects ? effects->GetAnimationGeneration() : 0;
  aAnimationInfo.SetAnimationGeneration(animationGeneration);

  EffectCompositor::ClearIsRunningOnCompositor(styleFrame, aProperty);
  nsTArray<RefPtr<dom::Animation>> compositorAnimations =
      EffectCompositor::GetAnimationsForCompositor(styleFrame, aProperty);
  if (compositorAnimations.IsEmpty()) {
    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)) {
    // EffectCompositor needs to know that we refused to run this animation
    // asynchronously so that it will not throttle the main thread
    // animation.
    aFrame->SetProperty(nsIFrame::RefusedAsyncAnimationProperty(), true);
    return;
  }

  AnimationData data;
  if (aProperty == eCSSProperty_transform) {
    // XXX Performance here isn't ideal for SVG. We'd prefer to avoid resolving
    // the dimensions of refBox. That said, we only get here if there are CSS
    // animations or transitions on this element, and that is likely to be a
    // lot rarer than transforms on SVG (the frequency of which drives the need
    // for TransformReferenceBox).
    TransformReferenceBox refBox(aFrame);
    nsRect bounds(0, 0, refBox.Width(), refBox.Height());
    // all data passed directly to the compositor should be in dev pixels
    int32_t devPixelsToAppUnits = aFrame->PresContext()->AppUnitsPerDevPixel();
    float scale = devPixelsToAppUnits;
    Point3D offsetToTransformOrigin =
        nsDisplayTransform::GetDeltaToTransformOrigin(aFrame, scale, &bounds);
    nsPoint origin;
    float scaleX = 1.0f;
    float scaleY = 1.0f;
    bool hasPerspectiveParent = false;
    if (aLayersBackend == layers::LayersBackend::LAYERS_WR) {
      // leave origin empty, because we are sending it separately on the
      // stacking context that we are pushing to WR, and WR will automatically
      // include it when picking up the animated transform values
    } else if (aItem) {
      // This branch is for display items to leverage the cache of
      // nsDisplayListBuilder.
      origin = aItem->ToReferenceFrame();
    } else {
      // This branch is running for restyling.
      // Animations are animated at the coordination of the reference
      // frame outside, not the given frame itself.  The given frame
      // is also reference frame too, so the parent's reference frame
      // are used.
      nsIFrame* referenceFrame = nsLayoutUtils::GetReferenceFrame(
          nsLayoutUtils::GetCrossDocParentFrame(aFrame));
      origin = aFrame->GetOffsetToCrossDoc(referenceFrame);
    }

    data = TransformData(origin, offsetToTransformOrigin, bounds,
                         devPixelsToAppUnits, scaleX, scaleY,
                         hasPerspectiveParent);
  } else {
    data = null_t();
  }

  MOZ_ASSERT(
      nsCSSProps::PropHasFlags(aProperty, CSSPropFlags::CanAnimateOnCompositor),
      "inconsistent property flags");

  // Add from first to last (since last overrides)
  for (size_t animIdx = 0; animIdx < compositorAnimations.Length(); animIdx++) {
    dom::Animation* anim = compositorAnimations[animIdx];
    if (!anim->IsRelevant()) {
      continue;
    }

    dom::KeyframeEffect* keyframeEffect =
        anim->GetEffect() ? anim->GetEffect()->AsKeyframeEffect() : nullptr;
    MOZ_ASSERT(keyframeEffect,
               "A playing animation should have a keyframe effect");
    const AnimationProperty* property =
        keyframeEffect->GetEffectiveAnimationOfProperty(aProperty, *effects);
    if (!property) {
      continue;
    }

    // Note that if the property is overridden by !important rules,
    // GetEffectiveAnimationOfProperty returns null instead.
    // This is what we want, since if we have animations overridden by
    // !important rules, we don't want to send them to the compositor.
    MOZ_ASSERT(
        anim->CascadeLevel() != EffectCompositor::CascadeLevel::Animations ||
            !EffectSet::GetEffectSet(styleFrame)
                 ->PropertiesWithImportantRules()
                 .HasProperty(aProperty),
        "GetEffectiveAnimationOfProperty already tested the property "
        "is not overridden by !important rules");

    // Don't add animations that are pending if their timeline does not
    // track wallclock time. This is because any pending animations on layers
    // will have their start time updated with the current wallclock time.
    // If we can't convert that wallclock time back to an equivalent timeline
    // time, we won't be able to update the content animation and it will end
    // up being out of sync with the layer animation.
    //
    // Currently this only happens when the timeline is driven by a refresh
    // driver under test control. In this case, the next time the refresh
    // driver is advanced it will trigger any pending animations.
    if (anim->Pending() &&
        (anim->GetTimeline() && !anim->GetTimeline()->TracksWallclockTime())) {
      continue;
    }

    AddAnimationForProperty(aFrame, *property, anim, aAnimationInfo, data,
                            aSendFlag);
    keyframeEffect->SetIsRunningOnCompositor(aProperty, true);
  }
}

static uint64_t AddAnimationsForWebRender(
    nsDisplayItem* aItem, nsCSSPropertyID aProperty,
    mozilla::layers::RenderRootStateManager* aManager,
    nsDisplayListBuilder* aDisplayListBuilder) {
  RefPtr<WebRenderAnimationData> animationData =
      aManager->CommandBuilder()
          .CreateOrRecycleWebRenderUserData<WebRenderAnimationData>(aItem);
  AnimationInfo& animationInfo = animationData->GetAnimationInfo();
  AddAnimationsForProperty(aItem->Frame(), aDisplayListBuilder, aItem,
                           aProperty, animationInfo, Send::Immediate,
                           layers::LayersBackend::LAYERS_WR);
  animationInfo.StartPendingAnimations(
      aManager->LayerManager()->GetAnimationReadyTime());

  // Note that animationsId can be 0 (uninitialized in AnimationInfo) if there
  // are no active animations.
  uint64_t animationsId = animationInfo.GetCompositorAnimationsId();
  if (!animationInfo.GetAnimations().IsEmpty()) {
    OpAddCompositorAnimations anim(
        CompositorAnimations(animationInfo.GetAnimations(), animationsId));
    aManager->WrBridge()->AddWebRenderParentCommand(anim);
    aManager->AddActiveCompositorAnimationId(animationsId);
  } else if (animationsId) {
    aManager->AddCompositorAnimationsIdForDiscard(animationsId);
    animationsId = 0;
  }

  return animationsId;
}

static bool GenerateAndPushTextMask(nsIFrame* aFrame, gfxContext* aContext,
                                    const nsRect& aFillRect,
                                    nsDisplayListBuilder* aBuilder) {
  if (aBuilder->IsForGenerateGlyphMask()) {
    return false;
  }

  // The main function of enabling background-clip:text property value.
  // When a nsDisplayBackgroundImage detects "text" bg-clip style, it will call
  // this function to
  // 1. Generate a mask by all descendant text frames
  // 2. Push the generated mask into aContext.

  gfxContext* sourceCtx = aContext;
  LayoutDeviceRect bounds = LayoutDeviceRect::FromAppUnits(
      aFillRect, aFrame->PresContext()->AppUnitsPerDevPixel());

  // Evaluate required surface size.
  IntRect drawRect =
      RoundedOut(ToRect(sourceCtx->GetClipExtents(gfxContext::eDeviceSpace)));

  Matrix currentMatrix = sourceCtx->CurrentMatrix();
  Matrix maskTransform =
      currentMatrix * Matrix::Translation(-drawRect.x, -drawRect.y);
  maskTransform.Invert();

  // Create a mask surface.
  RefPtr<DrawTarget> sourceTarget = sourceCtx->GetDrawTarget();
  if (!sourceTarget->CanCreateSimilarDrawTarget(drawRect.Size(),
                                                SurfaceFormat::A8)) {
    return false;
  }
  RefPtr<DrawTarget> maskDT = sourceTarget->CreateClippedDrawTarget(
      drawRect.Size(), maskTransform * currentMatrix, SurfaceFormat::A8);
  if (!maskDT || !maskDT->IsValid()) {
    return false;
  }
  RefPtr<gfxContext> maskCtx =
      gfxContext::CreatePreservingTransformOrNull(maskDT);
  MOZ_ASSERT(maskCtx);
  maskCtx->SetMatrix(Matrix::Translation(bounds.TopLeft().ToUnknownPoint()) *
                     currentMatrix * Matrix::Translation(-drawRect.TopLeft()));

  // Shade text shape into mask A8 surface.
  nsLayoutUtils::PaintFrame(
      maskCtx, aFrame, nsRect(nsPoint(0, 0), aFrame->GetSize()),
      NS_RGB(255, 255, 255), nsDisplayListBuilderMode::GENERATE_GLYPH);

  // Push the generated mask into aContext, so that the caller can pop and
  // blend with it.
  RefPtr<SourceSurface> maskSurface = maskDT->Snapshot();
  sourceCtx->PushGroupForBlendBack(gfxContentType::COLOR_ALPHA, 1.0,
                                   maskSurface, maskTransform);

  return true;
}

/* static */ void nsDisplayListBuilder::AddAnimationsAndTransitionsToLayer(
    Layer* aLayer, nsDisplayListBuilder* aBuilder, nsDisplayItem* aItem,
    nsIFrame* aFrame, nsCSSPropertyID aProperty) {
  MOZ_ASSERT(
      nsCSSProps::PropHasFlags(aProperty, CSSPropFlags::CanAnimateOnCompositor),
      "inconsistent property flags");

  // 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");

  // Only send animations to a layer that is actually using
  // off-main-thread compositing.
  LayersBackend backend = aLayer->Manager()->GetBackendType();
  if (!(backend == layers::LayersBackend::LAYERS_CLIENT ||
        backend == layers::LayersBackend::LAYERS_WR)) {
    return;
  }

  Send sendFlag = !aBuilder ? Send::NextTransaction : Send::Immediate;
  AnimationInfo& animationInfo = aLayer->GetAnimationInfo();
  AddAnimationsForProperty(aFrame, aBuilder, aItem, aProperty, animationInfo,
                           sendFlag, layers::LayersBackend::LAYERS_CLIENT);
  animationInfo.TransferMutatedFlagToLayer(aLayer);
}

nsDisplayItem* nsDisplayListBuilder::MergeItems(
    nsTArray<nsDisplayItem*>& aMergedItems) {
  // For merging, we create a temporary item by cloning the last item of the
  // mergeable items list. This ensures that the temporary item will have the
  // correct frame and bounds.
  nsDisplayItem* merged = nullptr;

  for (nsDisplayItem* item : Reversed(aMergedItems)) {
    MOZ_ASSERT(item);

    if (!merged) {
      // Create the temporary item.
      merged = item->Clone(this);
      MOZ_ASSERT(merged);

      AddTemporaryItem(merged);
    } else {
      // Merge the item properties (frame/bounds/etc) with the previously
      // created temporary item.
      MOZ_ASSERT(merged->CanMerge(item));
      merged->Merge(item);
    }

    // Create nsDisplayWrapList that points to the internal display list of the
    // item we are merging. This nsDisplayWrapList is added to the display list
    // of the temporary item.
    merged->MergeDisplayListFromItem(this, item);
  }

  return merged;
}

void nsDisplayListBuilder::AutoCurrentActiveScrolledRootSetter::
    SetCurrentActiveScrolledRoot(
        const ActiveScrolledRoot* aActiveScrolledRoot) {
  MOZ_ASSERT(!mUsed);

  // Set the builder's mCurrentActiveScrolledRoot.
  mBuilder->mCurrentActiveScrolledRoot = aActiveScrolledRoot;

  // We also need to adjust the builder's mCurrentContainerASR.
  // mCurrentContainerASR needs to be an ASR that all the container's
  // contents have finite bounds with respect to. If aActiveScrolledRoot
  // is an ancestor ASR of mCurrentContainerASR, that means we need to
  // set mCurrentContainerASR to aActiveScrolledRoot, because otherwise
  // the items that will be created with aActiveScrolledRoot wouldn't
  // have finite bounds with respect to mCurrentContainerASR. There's one
  // exception, in the case where there's a content clip on the builder
  // that is scrolled by a descendant ASR of aActiveScrolledRoot. This
  // content clip will clip all items that are created while this
  // AutoCurrentActiveScrolledRootSetter exists. This means that the items
  // created during our lifetime will have finite bounds with respect to
  // the content clip's ASR, even if the items' actual ASR is an ancestor
  // of that. And it also means that mCurrentContainerASR only needs to be
  // set to the content clip's ASR and not all the way to aActiveScrolledRoot.
  // This case is tested by fixed-pos-scrolled-clip-opacity-layerize.html
  // and fixed-pos-scrolled-clip-opacity-inside-layerize.html.

  // finiteBoundsASR is the leafmost ASR that all items created during
  // object's lifetime have finite bounds with respect to.
  const ActiveScrolledRoot* finiteBoundsASR =
      ActiveScrolledRoot::PickDescendant(mContentClipASR, aActiveScrolledRoot);

  // mCurrentContainerASR is adjusted so that it's still an ancestor of
  // finiteBoundsASR.
  mBuilder->mCurrentContainerASR = ActiveScrolledRoot::PickAncestor(
      mBuilder->mCurrentContainerASR, finiteBoundsASR);

  // If we are entering out-of-flow content inside a CSS filter, mark
  // scroll frames wrt. which the content is fixed as containing such content.
  if (mBuilder->mFilterASR && ActiveScrolledRoot::IsAncestor(
                                  aActiveScrolledRoot, mBuilder->mFilterASR)) {
    for (const ActiveScrolledRoot* asr = mBuilder->mFilterASR;
         asr && asr != aActiveScrolledRoot; asr = asr->mParent) {
      asr->mScrollableFrame->SetHasOutOfFlowContentInsideFilter();
    }
  }

  mUsed = true;
}

void nsDisplayListBuilder::AutoCurrentActiveScrolledRootSetter::
    InsertScrollFrame(nsIScrollableFrame* aScrollableFrame) {
  MOZ_ASSERT(!mUsed);
  size_t descendantsEndIndex = mBuilder->mActiveScrolledRoots.Length();
  const ActiveScrolledRoot* parentASR = mBuilder->mCurrentActiveScrolledRoot;
  const ActiveScrolledRoot* asr =
      mBuilder->AllocateActiveScrolledRoot(parentASR, aScrollableFrame);
  mBuilder->mCurrentActiveScrolledRoot = asr;

  // All child ASRs of parentASR that were created while this
  // AutoCurrentActiveScrolledRootSetter object was on the stack belong to us
  // now. Reparent them to asr.
  for (size_t i = mDescendantsStartIndex; i < descendantsEndIndex; i++) {
    ActiveScrolledRoot* descendantASR = mBuilder->mActiveScrolledRoots[i];
    if (ActiveScrolledRoot::IsAncestor(parentASR, descendantASR)) {
      descendantASR->IncrementDepth();
      if (descendantASR->mParent == parentASR) {
        descendantASR->mParent = asr;
      }
    }
  }

  mUsed = true;
}

/* static */ nsRect
nsDisplayListBuilder::OutOfFlowDisplayData::ComputeVisibleRectForFrame(
    nsDisplayListBuilder* aBuilder, nsIFrame* aFrame,
    const nsRect& aVisibleRect, const nsRect& aDirtyRect,
    nsRect* aOutDirtyRect) {
  nsRect visible = aVisibleRect;
  nsRect dirtyRectRelativeToDirtyFrame = aDirtyRect;

#ifdef MOZ_WIDGET_ANDROID
  if (nsLayoutUtils::IsFixedPosFrameInDisplayPort(aFrame) &&
      aBuilder->IsPaintingToWindow()) {
    // We want to ensure that fixed position elements are visible when
    // being async scrolled, so we paint them at the size of the larger
    // viewport.
    dirtyRectRelativeToDirtyFrame =
        nsRect(nsPoint(0, 0), aFrame->GetParent()->GetSize());

    nsIPresShell* ps = aFrame->PresShell();
    if (ps->IsVisualViewportSizeSet() &&
        dirtyRectRelativeToDirtyFrame.Size() < ps->GetVisualViewportSize()) {
      dirtyRectRelativeToDirtyFrame.SizeTo(ps->GetVisualViewportSize());
    }

    visible = dirtyRectRelativeToDirtyFrame;
  }
#endif

  *aOutDirtyRect = dirtyRectRelativeToDirtyFrame - aFrame->GetPosition();
  visible -= aFrame->GetPosition();

  nsRect overflowRect = aFrame->GetVisualOverflowRect();

  if (aFrame->IsTransformed() &&
      mozilla::EffectCompositor::HasAnimationsForCompositor(
          aFrame, 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));
  }

  visible.IntersectRect(visible, overflowRect);
  aOutDirtyRect->IntersectRect(*aOutDirtyRect, overflowRect);

  return visible;
}

nsDisplayListBuilder::nsDisplayListBuilder(nsIFrame* aReferenceFrame,
                                           nsDisplayListBuilderMode aMode,
                                           bool aBuildCaret,
                                           bool aRetainingDisplayList)
    : mReferenceFrame(aReferenceFrame),
      mIgnoreScrollFrame(nullptr),
      mCurrentTableItem(nullptr),
      mCurrentActiveScrolledRoot(nullptr),
      mCurrentContainerASR(nullptr),
      mCurrentFrame(aReferenceFrame),
      mCurrentReferenceFrame(aReferenceFrame),
      mRootAGR(AnimatedGeometryRoot::CreateAGRForFrame(
          aReferenceFrame, nullptr, true, aRetainingDisplayList)),
      mCurrentAGR(mRootAGR),
      mUsedAGRBudget(0),
      mDirtyRect(-1, -1, -1, -1),
      mGlassDisplayItem(nullptr),
      mScrollInfoItemsForHoisting(nullptr),
      mFirstClipChainToDestroy(nullptr),
      mActiveScrolledRootForRootScrollframe(nullptr),
      mMode(aMode),
      mCurrentScrollParentId(ScrollableLayerGuid::NULL_SCROLL_ID),
      mCurrentScrollbarTarget(ScrollableLayerGuid::NULL_SCROLL_ID),
      mSVGEffectsBuildingDepth(0),
      mFilterASR(nullptr),
      mContainsBlendMode(false),
      mIsBuildingScrollbar(false),
      mCurrentScrollbarWillHaveLayer(false),
      mBuildCaret(aBuildCaret),
      mRetainingDisplayList(aRetainingDisplayList),
      mPartialUpdate(false),
      mIgnoreSuppression(false),
      mIsAtRootOfPseudoStackingContext(false),
      mIncludeAllOutOfFlows(false),
      mDescendIntoSubdocuments(true),
      mSelectedFramesOnly(false),
      mAllowMergingAndFlattening(true),
      mWillComputePluginGeometry(false),
      mInTransform(false),
      mInFilter(false),
      mInPageSequence(false),
      mIsInChromePresContext(false),
      mSyncDecodeImages(false),
      mIsPaintingToWindow(false),
      mIsPaintingForWebRender(false),
      mIsCompositingCheap(false),
      mContainsPluginItem(false),
      mAncestorHasApzAwareEventHandler(false),
      mHaveScrollableDisplayPort(false),
      mWindowDraggingAllowed(false),
      mIsBuildingForPopup(nsLayoutUtils::IsPopup(aReferenceFrame)),
      mForceLayerForScrollParent(false),
      mAsyncPanZoomEnabled(nsLayoutUtils::AsyncPanZoomEnabled(aReferenceFrame)),
      mBuildingInvisibleItems(false),
      mHitTestIsForVisibility(false),
      mIsBuilding(false),
      mInInvalidSubtree(false),
      mDisablePartialUpdates(false),
      mPartialBuildFailed(false),
      mIsInActiveDocShell(false),
      mHitTestArea(),
      mHitTestInfo(CompositorHitTestInvisibleToHit) {
  MOZ_COUNT_CTOR(nsDisplayListBuilder);

  mBuildCompositorHitTestInfo = mAsyncPanZoomEnabled && IsForPainting();

  static_assert(
      static_cast<uint32_t>(DisplayItemType::TYPE_MAX) < (1 << TYPE_BITS),
      "Check TYPE_MAX should not overflow");
}

void nsDisplayListBuilder::BeginFrame() {
  nsCSSRendering::BeginFrameTreesLocked();
  mCurrentAGR = mRootAGR;
  mFrameToAnimatedGeometryRootMap.Put(mReferenceFrame, mRootAGR);

  mIsPaintingToWindow = false;
  mIgnoreSuppression = false;
  mInTransform = false;
  mInFilter = false;
  mSyncDecodeImages = false;
}

void nsDisplayListBuilder::EndFrame() {
  NS_ASSERTION(!mInInvalidSubtree,
               "Someone forgot to cleanup mInInvalidSubtree!");
  mFrameToAnimatedGeometryRootMap.Clear();
  mAGRBudgetSet.Clear();
  mActiveScrolledRoots.Clear();
  FreeClipChains();
  FreeTemporaryItems();
  nsCSSRendering::EndFrameTreesLocked();
}

void nsDisplayListBuilder::MarkFrameForDisplay(nsIFrame* aFrame,
                                               nsIFrame* aStopAtFrame) {
  mFramesMarkedForDisplay.AppendElement(aFrame);
  for (nsIFrame* f = aFrame; f;
       f = nsLayoutUtils::GetParentOrPlaceholderForCrossDoc(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::AddFrameMarkedForDisplayIfVisible(nsIFrame* aFrame) {
  mFramesMarkedForDisplayIfVisible.AppendElement(aFrame);
}

void nsDisplayListBuilder::MarkFrameForDisplayIfVisible(
    nsIFrame* aFrame, nsIFrame* aStopAtFrame) {
  AddFrameMarkedForDisplayIfVisible(aFrame);
  for (nsIFrame* f = aFrame; f;
       f = nsLayoutUtils::GetParentOrPlaceholderForCrossDoc(f)) {
    if (f->ForceDescendIntoIfVisible()) return;
    f->SetForceDescendIntoIfVisible(true);
    if (f == aStopAtFrame) {
      // we've reached a frame that we know will be painted, so we can stop.
      break;
    }
  }
}

bool nsDisplayListBuilder::NeedToForceTransparentSurfaceForItem(
    nsDisplayItem* aItem) {
  return aItem == mGlassDisplayItem || aItem->ClearsBackground();
}

AnimatedGeometryRoot* nsDisplayListBuilder::WrapAGRForFrame(
    nsIFrame* aAnimatedGeometryRoot, bool aIsAsync,
    AnimatedGeometryRoot* aParent /* = nullptr */) {
  DebugOnly<bool> dummy;
  MOZ_ASSERT(IsAnimatedGeometryRoot(aAnimatedGeometryRoot, dummy) == AGR_YES);

  RefPtr<AnimatedGeometryRoot> result;
  if (!mFrameToAnimatedGeometryRootMap.Get(aAnimatedGeometryRoot, &result)) {
    MOZ_ASSERT(nsLayoutUtils::IsAncestorFrameCrossDoc(RootReferenceFrame(),
                                                      aAnimatedGeometryRoot));
    RefPtr<AnimatedGeometryRoot> parent = aParent;
    if (!parent) {
      nsIFrame* parentFrame =
          nsLayoutUtils::GetCrossDocParentFrame(aAnimatedGeometryRoot);
      if (parentFrame) {
        bool isAsync;
        nsIFrame* parentAGRFrame =
            FindAnimatedGeometryRootFrameFor(parentFrame, isAsync);
        parent = WrapAGRForFrame(parentAGRFrame, isAsync);
      }
    }
    result = AnimatedGeometryRoot::CreateAGRForFrame(
        aAnimatedGeometryRoot, parent, aIsAsync, IsRetainingDisplayList());
    mFrameToAnimatedGeometryRootMap.Put(aAnimatedGeometryRoot, result);
  }
  MOZ_ASSERT(!aParent || result->mParentAGR == aParent);
  return result;
}

AnimatedGeometryRoot* nsDisplayListBuilder::AnimatedGeometryRootForASR(
    const ActiveScrolledRoot* aASR) {
  if (!aASR) {
    return GetRootAnimatedGeometryRoot();
  }
  nsIFrame* scrolledFrame = aASR->mScrollableFrame->GetScrolledFrame();
  return FindAnimatedGeometryRootFor(scrolledFrame);
}

AnimatedGeometryRoot* nsDisplayListBuilder::FindAnimatedGeometryRootFor(
    nsIFrame* aFrame) {
  if (!IsPaintingToWindow()) {
    return mRootAGR;
  }
  if (aFrame == mCurrentFrame) {
    return mCurrentAGR;
  }
  RefPtr<AnimatedGeometryRoot> result;
  if (mFrameToAnimatedGeometryRootMap.Get(aFrame, &result)) {
    return result;
  }

  bool isAsync;
  nsIFrame* agrFrame = FindAnimatedGeometryRootFrameFor(aFrame, isAsync);
  result = WrapAGRForFrame(agrFrame, isAsync);
  mFrameToAnimatedGeometryRootMap.Put(aFrame, result);
  return result;
}

AnimatedGeometryRoot* nsDisplayListBuilder::FindAnimatedGeometryRootFor(
    nsDisplayItem* aItem) {
  if (aItem->ShouldFixToViewport(this)) {
    // Make its active scrolled root be the active scrolled root of
    // the enclosing viewport, since it shouldn't be scrolled by scrolled
    // frames in its document. InvalidateFixedBackgroundFramesFromList in
    // nsGfxScrollFrame will not repaint this item when scrolling occurs.
    nsIFrame* viewportFrame = nsLayoutUtils::GetClosestFrameOfType(
        aItem->Frame(), LayoutFrameType::Viewport, RootReferenceFrame());
    if (viewportFrame) {
      return FindAnimatedGeometryRootFor(viewportFrame);
    }
  }
  return FindAnimatedGeometryRootFor(aItem->Frame());
}

bool nsDisplayListBuilder::MarkOutOfFlowFrameForDisplay(nsIFrame* aDirtyFrame,
                                                        nsIFrame* aFrame) {
  MOZ_ASSERT(aFrame->GetParent() == aDirtyFrame);
  nsRect dirty;
  nsRect visible = OutOfFlowDisplayData::ComputeVisibleRectForFrame(
      this, aFrame, GetVisibleRect(), GetDirtyRect(), &dirty);
  if (!(aFrame->GetStateBits() & NS_FRAME_FORCE_DISPLAY_LIST_DESCEND_INTO) &&
      visible.IsEmpty()) {
    return false;
  }

  // Only MarkFrameForDisplay if we're dirty. If this is a nested out-of-flow
  // frame, then it will also mark any outer frames to ensure that building
  // reaches the dirty feame.
  if (!dirty.IsEmpty() || aFrame->ForceDescendIntoIfVisible()) {
    MarkFrameForDisplay(aFrame, aDirtyFrame);
  }

  return true;
}

static void UnmarkFrameForDisplay(nsIFrame* aFrame, nsIFrame* aStopAtFrame) {
  for (nsIFrame* f = aFrame; f;
       f = nsLayoutUtils::GetParentOrPlaceholderForCrossDoc(f)) {
    if (!(f->GetStateBits() & NS_FRAME_FORCE_DISPLAY_LIST_DESCEND_INTO)) return;
    f->RemoveStateBits(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;
    }
  }
}

static void UnmarkFrameForDisplayIfVisible(nsIFrame* aFrame) {
  for (nsIFrame* f = aFrame; f;
       f = nsLayoutUtils::GetParentOrPlaceholderForCrossDoc(f)) {
    if (!f->ForceDescendIntoIfVisible()) return;
    f->SetForceDescendIntoIfVisible(false);
  }
}

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

  DisplayItemClipChain* c = mFirstClipChainToDestroy;
  while (c) {
    DisplayItemClipChain* next = c->mNextClipChainToDestroy;
    c->DisplayItemClipChain::~DisplayItemClipChain();
    c = next;
  }

  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() {
  RefPtr<nsCaret> caret = CurrentPresShellState()->mPresShell->GetCaret();
  return caret;
}

void nsDisplayListBuilder::IncrementPresShellPaintCount(
    nsIPresShell* aPresShell) {
  if (mIsPaintingToWindow) {
    mReferenceFrame->AddPaintedPresShell(aPresShell);
    aPresShell->IncrementPaintCount();
  }
}

void nsDisplayListBuilder::EnterPresShell(nsIFrame* aReferenceFrame,
                                          bool aPointerEventsNoneDoc) {
  PresShellState* state = mPresShellStates.AppendElement();
  state->mPresShell = aReferenceFrame->PresShell();
  state->mCaretFrame = nullptr;
  state->mFirstFrameMarkedForDisplay = mFramesMarkedForDisplay.Length();
  state->mFirstFrameWithOOFData = mFramesWithOOFData.Length();

  nsIScrollableFrame* sf = state->mPresShell->GetRootScrollFrameAsScrollable();
  if (sf && IsInSubdocument()) {
    // We are forcing a rebuild of nsDisplayCanvasBackgroundColor to make sure
    // that the canvas background color will be set correctly, and that only one
    // unscrollable item will be created.
    // This is done to avoid, for example, a case where only scrollbar frames
    // are invalidated - we would skip creating nsDisplayCanvasBackgroundColor
    // and possibly end up with an extra nsDisplaySolidColor item.
    // We skip this for the root document, since we don't want to use
    // MarkFrameForDisplayIfVisible before ComputeRebuildRegion. We'll
    // do it manually there.
    nsCanvasFrame* canvasFrame = do_QueryFrame(sf->GetScrolledFrame());
    if (canvasFrame) {
      MarkFrameForDisplayIfVisible(canvasFrame, aReferenceFrame);
    }
  }

#ifdef DEBUG
  state->mAutoLayoutPhase.emplace(aReferenceFrame->PresContext(),
                                  eLayoutPhase_DisplayListBuilding);
#endif

  state->mPresShell->UpdateCanvasBackground();

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

  bool pointerEventsNone = aPointerEventsNoneDoc;
  if (IsInSubdocument()) {
    pointerEventsNone |= mPresShellStates[mPresShellStates.Length() - 2]
                             .mInsidePointerEventsNoneDoc;
  }
  state->mInsidePointerEventsNoneDoc = pointerEventsNone;

  state->mPresShellIgnoreScrollFrame =
      state->mPresShell->IgnoringViewportScrolling()
          ? state->mPresShell->GetRootScrollFrame()
          : nullptr;

  nsPresContext* pc = aReferenceFrame->PresContext();
  nsCOMPtr<nsIDocShell> docShell = pc->GetDocShell();
  if (docShell) {
    docShell->GetWindowDraggingAllowed(&mWindowDraggingAllowed);
  }

  mIsInChromePresContext = pc->IsChrome();

  if (!buildCaret) {
    return;
  }

  RefPtr<nsCaret> caret = state->mPresShell->GetCaret();
  state->mCaretFrame = caret->GetPaintGeometry(&state->mCaretRect);
  if (state->mCaretFrame) {
    MarkFrameForDisplay(state->mCaretFrame, aReferenceFrame);
  }
}

// A non-blank paint is a paint that does not just contain the canvas
// background.
static bool DisplayListIsNonBlank(nsDisplayList* aList) {
  for (nsDisplayItem* i = aList->GetBottom(); i != nullptr; i = i->GetAbove()) {
    switch (i->GetType()) {
      case DisplayItemType::TYPE_COMPOSITOR_HITTEST_INFO:
      case DisplayItemType::TYPE_CANVAS_BACKGROUND_COLOR:
      case DisplayItemType::TYPE_CANVAS_BACKGROUND_IMAGE:
        continue;
      case DisplayItemType::TYPE_SOLID_COLOR:
      case DisplayItemType::TYPE_BACKGROUND:
      case DisplayItemType::TYPE_BACKGROUND_COLOR:
        if (i->Frame()->IsCanvasFrame()) {
          continue;
        }
        return true;
      default:
        return true;
    }
  }
  return false;
}

// A contentful paint is a paint that does contains DOM content (text,
// images, non-blank canvases, SVG): "First Contentful Paint entry
// contains a DOMHighResTimeStamp reporting the time when the browser
// first rendered any text, image (including background images),
// non-white canvas or SVG. This excludes any content of iframes, but
// includes text with pending webfonts. This is the first time users
// could start consuming page content."
static bool DisplayListIsContentful(nsDisplayList* aList) {
  for (nsDisplayItem* i = aList->GetBottom(); i != nullptr; i = i->GetAbove()) {
    DisplayItemType type = i->GetType();
    nsDisplayList* children = i->GetChildren();

    switch (type) {
      case DisplayItemType::TYPE_SUBDOCUMENT:  // iframes are ignored
        break;
      // CANVASes check if they may have been modified (as a stand-in
      // actually tracking all modifications)
      default:
        if (i->IsContentful()) {
          return true;
        }
        if (children) {
          if (DisplayListIsContentful(children)) {
            return true;
          }
        }
        break;
    }
  }
  return false;
}

void nsDisplayListBuilder::LeavePresShell(nsIFrame* aReferenceFrame,
                                          nsDisplayList* aPaintedContents) {
  NS_ASSERTION(
      CurrentPresShellState()->mPresShell == aReferenceFrame->PresShell(),
      "Presshell mismatch");

  if (mIsPaintingToWindow && aPaintedContents) {
    nsPresContext* pc = aReferenceFrame->PresContext();
    if (!pc->HadNonBlankPaint()) {
      if (!CurrentPresShellState()->mIsBackgroundOnly &&
          DisplayListIsNonBlank(aPaintedContents)) {
        pc->NotifyNonBlankPaint();
      }
    }
    if (!pc->HadContentfulPaint()) {
      if (!CurrentPresShellState()->mIsBackgroundOnly &&
          DisplayListIsContentful(aPaintedContents)) {
        pc->NotifyContentfulPaint();
      }
    }
  }

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

  if (!mPresShellStates.IsEmpty()) {
    nsPresContext* pc = CurrentPresContext();
    nsCOMPtr<nsIDocShell> docShell = pc->GetDocShell();
    if (docShell) {
      docShell->GetWindowDraggingAllowed(&mWindowDraggingAllowed);
    }
    mIsInChromePresContext = pc->IsChrome();
  } else {
    mCurrentAGR = mRootAGR;

    for (uint32_t i = 0; i < mFramesMarkedForDisplayIfVisible.Length(); ++i) {
      UnmarkFrameForDisplayIfVisible(mFramesMarkedForDisplayIfVisible[i]);
    }
    mFramesMarkedForDisplayIfVisible.SetLength(0);
  }
}

void nsDisplayListBuilder::FreeClipChains() {
  // Iterate the clip chains from newest to oldest (forward
  // iteration), so that we destroy descendants first which
  // will drop the ref count on their ancestors.
  DisplayItemClipChain** indirect = &mFirstClipChainToDestroy;

  while (*indirect) {
    if (!(*indirect)->mRefCount) {
      DisplayItemClipChain* next = (*indirect)->mNextClipChainToDestroy;

      mClipDeduplicator.erase(*indirect);
      (*indirect)->DisplayItemClipChain::~DisplayItemClipChain();
      Destroy(DisplayItemType::TYPE_ZERO, *indirect);

      *indirect = next;
    } else {
      indirect = &(*indirect)->mNextClipChainToDestroy;
    }
  }
}

void nsDisplayListBuilder::FreeTemporaryItems() {
  for (nsDisplayItem* i : mTemporaryItems) {
    // Temporary display items are not added to the frames.
    MOZ_ASSERT(i->Frame());
    i->RemoveFrame(i->Frame());
    i->Destroy(this);
  }

  mTemporaryItems.Clear();
}

void nsDisplayListBuilder::ResetMarkedFramesForDisplayList(
    nsIFrame* aReferenceFrame) {
  // 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], aReferenceFrame);
  }
  mFramesMarkedForDisplay.SetLength(firstFrameForShell);

  firstFrameForShell = CurrentPresShellState()->mFirstFrameWithOOFData;
  for (uint32_t i = firstFrameForShell; i < mFramesWithOOFData.Length(); ++i) {
    mFramesWithOOFData[i]->DeleteProperty(OutOfFlowDisplayDataProperty());
  }
  mFramesWithOOFData.SetLength(firstFrameForShell);
}

void nsDisplayListBuilder::ClearFixedBackgroundDisplayData() {
  CurrentPresShellState()->mFixedBackgroundDisplayData = Nothing();
}

void nsDisplayListBuilder::MarkFramesForDisplayList(
    nsIFrame* aDirtyFrame, const nsFrameList& aFrames) {
  bool markedFrames = false;
  for (nsIFrame* e : aFrames) {
    // Skip the AccessibleCaret frame when building no caret.
    if (!IsBuildingCaret()) {
      nsIContent* content = e->GetContent();
      if (content && content->IsInNativeAnonymousSubtree() &&
          content->IsElement()) {
        auto classList = content->AsElement()->ClassList();
        if (classList->Contains(NS_LITERAL_STRING("moz-accessiblecaret"))) {
          continue;
        }
      }
    }
    if (MarkOutOfFlowFrameForDisplay(aDirtyFrame, e)) {
      markedFrames = true;
    }
  }

  if (markedFrames) {
    // mClipState.GetClipChainForContainingBlockDescendants can return pointers
    // to objects on the stack, so we need to clone the chain.
    const DisplayItemClipChain* clipChain =
        CopyWholeChain(mClipState.GetClipChainForContainingBlockDescendants());
    const DisplayItemClipChain* combinedClipChain =
        mClipState.GetCurrentCombinedClipChain(this);
    const ActiveScrolledRoot* asr = mCurrentActiveScrolledRoot;
    OutOfFlowDisplayData* data = new OutOfFlowDisplayData(
        clipChain, combinedClipChain, asr, GetVisibleRect(), GetDirtyRect());
    aDirtyFrame->SetProperty(
        nsDisplayListBuilder::OutOfFlowDisplayDataProperty(), data);
    mFramesWithOOFData.AppendElement(aDirtyFrame);
  }

  if (!aDirtyFrame->GetParent()) {
    // This is the viewport frame of aDirtyFrame's presshell.
    // Store the current display data so that it can be used for fixed
    // background images.
    NS_ASSERTION(
        CurrentPresShellState()->mPresShell == aDirtyFrame->PresShell(),
        "Presshell mismatch");
    MOZ_ASSERT(!CurrentPresShellState()->mFixedBackgroundDisplayData,
               "already traversed this presshell's root frame?");

    const DisplayItemClipChain* clipChain =
        CopyWholeChain(mClipState.GetClipChainForContainingBlockDescendants());
    const DisplayItemClipChain* combinedClipChain =
        mClipState.GetCurrentCombinedClipChain(this);
    const ActiveScrolledRoot* asr = mCurrentActiveScrolledRoot;
    CurrentPresShellState()->mFixedBackgroundDisplayData.emplace(
        clipChain, combinedClipChain, asr, GetVisibleRect(), GetDirtyRect());
  }
}

/**
 * Mark all preserve-3d children with
 * NS_FRAME_FORCE_DISPLAY_LIST_DESCEND_INTO to make sure
 * nsFrame::BuildDisplayListForChild() would visit them.  Also compute
 * dirty rect for preserve-3d children.
 *
 * @param aDirtyFrame is the frame to mark children extending context.
 */
void nsDisplayListBuilder::MarkPreserve3DFramesForDisplayList(
    nsIFrame* aDirtyFrame) {
  AutoTArray<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->Combines3DTransformWithAncestors()) {
        MarkFrameForDisplay(child, aDirtyFrame);
      }
    }
  }
}

uint32_t gDisplayItemSizes[static_cast<uint32_t>(DisplayItemType::TYPE_MAX)] = {
    0};

void* nsDisplayListBuilder::Allocate(size_t aSize, DisplayItemType aType) {
  size_t roundedUpSize = RoundUpPow2(aSize);
  uint_fast8_t type = FloorLog2Size(roundedUpSize);

  MOZ_RELEASE_ASSERT(gDisplayItemSizes[static_cast<uint32_t>(aType)] == type ||
                     gDisplayItemSizes[static_cast<uint32_t>(aType)] == 0);
  gDisplayItemSizes[static_cast<uint32_t>(aType)] = type;
  return mPool.AllocateByCustomID(type, roundedUpSize);
}

void nsDisplayListBuilder::Destroy(DisplayItemType aType, void* aPtr) {
  mPool.FreeByCustomID(gDisplayItemSizes[static_cast<uint32_t>(aType)], aPtr);
}

ActiveScrolledRoot* nsDisplayListBuilder::AllocateActiveScrolledRoot(
    const ActiveScrolledRoot* aParent, nsIScrollableFrame* aScrollableFrame) {
  RefPtr<ActiveScrolledRoot> asr = ActiveScrolledRoot::CreateASRForFrame(
      aParent, aScrollableFrame, IsRetainingDisplayList());
  mActiveScrolledRoots.AppendElement(asr);
  return asr;
}

const DisplayItemClipChain* nsDisplayListBuilder::AllocateDisplayItemClipChain(
    const DisplayItemClip& aClip, const ActiveScrolledRoot* aASR,
    const DisplayItemClipChain* aParent) {
  MOZ_ASSERT(!(aParent && aParent->mOnStack));
  void* p = Allocate(sizeof(DisplayItemClipChain), DisplayItemType::TYPE_ZERO);
  DisplayItemClipChain* c = new (KnownNotNull, p)
      DisplayItemClipChain(aClip, aASR, aParent, mFirstClipChainToDestroy);
#ifdef DEBUG
  c->mOnStack = false;
#endif
  auto result = mClipDeduplicator.insert(c);
  if (!result.second) {
    // An equivalent clip chain item was already created, so let's return that
    // instead. Destroy the one we just created.
    // Note that this can cause clip chains from different coordinate systems to
    // collapse into the same clip chain object, because clip chains do not keep
    // track of the reference frame that they were created in.
    c->DisplayItemClipChain::~DisplayItemClipChain();
    Destroy(DisplayItemType::TYPE_ZERO, c);
    return *(result.first);
  }
  mFirstClipChainToDestroy = c;
  return c;
}

struct ClipChainItem {
  DisplayItemClip clip;
  const ActiveScrolledRoot* asr;
};

const DisplayItemClipChain* nsDisplayListBuilder::CreateClipChainIntersection(
    const DisplayItemClipChain* aAncestor,
    const DisplayItemClipChain* aLeafClip1,
    const DisplayItemClipChain* aLeafClip2) {
  AutoTArray<ClipChainItem, 8> intersectedClips;

  const DisplayItemClipChain* clip1 = aLeafClip1;
  const DisplayItemClipChain* clip2 = aLeafClip2;

  const ActiveScrolledRoot* asr = ActiveScrolledRoot::PickDescendant(
      clip1 ? clip1->mASR : nullptr, clip2 ? clip2->mASR : nullptr);

  // Build up the intersection from the leaf to the root and put it into
  // intersectedClips. The loop below will convert intersectedClips into an
  // actual DisplayItemClipChain.
  // (We need to do this in two passes because we need the parent clip in order
  // to create the DisplayItemClipChain object, but the parent clip has not
  // been created at that point.)
  while (!aAncestor || asr != aAncestor->mASR) {
    if (clip1 && clip1->mASR == asr) {
      if (clip2 && clip2->mASR == asr) {
        DisplayItemClip intersection = clip1->mClip;
        intersection.IntersectWith(clip2->mClip);
        intersectedClips.AppendElement(ClipChainItem{intersection, asr});
        clip2 = clip2->mParent;
      } else {
        intersectedClips.AppendElement(ClipChainItem{clip1->mClip, asr});
      }
      clip1 = clip1->mParent;
    } else if (clip2 && clip2->mASR == asr) {
      intersectedClips.AppendElement(ClipChainItem{clip2->mClip, asr});
      clip2 = clip2->mParent;
    }
    if (!asr) {
      MOZ_ASSERT(!aAncestor, "We should have exited this loop earlier");
      break;
    }
    asr = asr->mParent;
  }

  // Convert intersectedClips into a DisplayItemClipChain.
  const DisplayItemClipChain* parentSC = aAncestor;
  for (auto& sc : Reversed(intersectedClips)) {
    parentSC = AllocateDisplayItemClipChain(sc.clip, sc.asr, parentSC);
  }
  return parentSC;
}

const DisplayItemClipChain* nsDisplayListBuilder::CopyWholeChain(
    const DisplayItemClipChain* aClipChain) {
  return CreateClipChainIntersection(nullptr, aClipChain, nullptr);
}

const DisplayItemClipChain* nsDisplayListBuilder::FuseClipChainUpTo(
    const DisplayItemClipChain* aClipChain, const ActiveScrolledRoot* aASR) {
  if (!aClipChain) {
    return nullptr;
  }

  const DisplayItemClipChain* sc = aClipChain;
  DisplayItemClip mergedClip;
  while (sc && ActiveScrolledRoot::PickDescendant(aASR, sc->mASR) == sc->mASR) {
    mergedClip.IntersectWith(sc->mClip);
    sc = sc->mParent;
  }

  if (!mergedClip.HasClip()) {
    return nullptr;
  }

  return AllocateDisplayItemClipChain(mergedClip, aASR, sc);
}

const nsIFrame* nsDisplayListBuilder::FindReferenceFrameFor(
    const nsIFrame* aFrame, nsPoint* aOffset) const {
  if (aFrame == mCurrentFrame) {
    if (aOffset) {
      *aOffset = mCurrentOffsetToReferenceFrame;
    }
    return mCurrentReferenceFrame;
  }
  for (const nsIFrame* f = aFrame; f;
       f = nsLayoutUtils::GetCrossDocParentFrame(f)) {
    if (f == mReferenceFrame || f->IsTransformed()) {
      if (aOffset) {
        *aOffset = aFrame->GetOffsetToCrossDoc(f);
      }
      return f;
    }
  }
  if (aOffset) {
    *aOffset = aFrame->GetOffsetToCrossDoc(mReferenceFrame);
  }
  return mReferenceFrame;
}

// Sticky frames are active if their nearest scrollable frame is also active.
static bool IsStickyFrameActive(nsDisplayListBuilder* aBuilder,
                                nsIFrame* aFrame, nsIFrame* aParent) {
  MOZ_ASSERT(aFrame->StyleDisplay()->mPosition == NS_STYLE_POSITION_STICKY);

  // Find the nearest scrollframe.
  nsIFrame* cursor = aFrame;
  nsIFrame* parent = aParent;
  if (!parent) {
    parent = nsLayoutUtils::GetCrossDocParentFrame(aFrame);
  }
  while (!parent->IsScrollFrame()) {
    cursor = parent;
    if ((parent = nsLayoutUtils::GetCrossDocParentFrame(cursor)) == nullptr) {
      return false;
    }
  }

  nsIScrollableFrame* sf = do_QueryFrame(parent);
  return sf->IsScrollingActive(aBuilder) && sf->GetScrolledFrame() == cursor;
}

nsDisplayListBuilder::AGRState nsDisplayListBuilder::IsAnimatedGeometryRoot(
    nsIFrame* aFrame, bool& aIsAsync, nsIFrame** aParent) {
  aIsAsync = false;
  if (aFrame == mReferenceFrame) {
    aIsAsync = true;
    return AGR_YES;
  }
  if (!IsPaintingToWindow()) {
    if (aParent) {
      *aParent = nsLayoutUtils::GetCrossDocParentFrame(aFrame);
    }
    return AGR_NO;
  }

  nsIFrame* parent = nsLayoutUtils::GetCrossDocParentFrame(aFrame);
  if (!parent) {
    aIsAsync = true;
    return AGR_YES;
  }

  AGRState result = AGR_NO;  // Possible to transition from not being an AGR
                             // to being an AGR without a style change.

  LayoutFrameType parentType = parent->Type();

  if (aFrame->IsTransformed()) {
    aIsAsync = EffectCompositor::HasAnimationsForCompositor(
        aFrame, eCSSProperty_transform);
    result = AGR_YES;
  }

  if (parentType == LayoutFrameType::Scroll ||
      parentType == LayoutFrameType::ListControl) {
    nsIScrollableFrame* sf = do_QueryFrame(parent);
    if (sf->GetScrolledFrame() == aFrame) {
      if (sf->IsScrollingActive(this)) {
        aIsAsync = aIsAsync || sf->IsMaybeAsynchronouslyScrolled();
        result = AGR_YES;
      } else {
        result = AGR_MAYBE;
      }
    }
  }

  // Finished checking all conditions that might set aIsAsync, so we can
  // early return now.
  if (result == AGR_YES) {
    return result;
  }

  if (nsLayoutUtils::IsPopup(aFrame)) return AGR_YES;
  if (ActiveLayerTracker::IsOffsetStyleAnimated(aFrame)) {
    const bool inBudget = AddToAGRBudget(aFrame);
    if (inBudget) {
      return AGR_YES;
    }
  }
  if (!aFrame->GetParent() &&
      nsLayoutUtils::ViewportHasDisplayPort(aFrame->PresContext())) {
    // Viewport frames in a display port need to be animated geometry roots
    // for background-attachment:fixed elements.
    return AGR_YES;
  }

  // Treat the slider thumb as being as an active scrolled root when it wants
  // its own layer so that it can move without repainting.
  if (parentType == LayoutFrameType::Slider) {
    nsIScrollableFrame* sf =
        static_cast<nsSliderFrame*>(parent)->GetScrollFrame();
    // The word "Maybe" in IsMaybeScrollingActive might be confusing but we do
    // indeed need to always consider scroll thumbs as AGRs if
    // IsMaybeScrollingActive is true because that is the same condition we use
    // in ScrollFrameHelper::AppendScrollPartsTo to layerize scroll thumbs.
    if (sf && sf->IsMaybeScrollingActive()) {
      return AGR_YES;
    }
    result = AGR_MAYBE;
  }

  if (aFrame->StyleDisplay()->mPosition == NS_STYLE_POSITION_STICKY) {
    if (IsStickyFrameActive(this, aFrame, parent)) {
      return AGR_YES;
    }
    result = AGR_MAYBE;
  }

  // Fixed-pos frames are parented by the viewport frame, which has no parent.
  if (nsLayoutUtils::IsFixedPosFrameInDisplayPort(aFrame)) {
    return AGR_YES;
  }

  if ((aFrame->GetStateBits() & NS_FRAME_MAY_BE_TRANSFORMED) &&
      aFrame->IsFrameOfType(nsIFrame::eSVG)) {
    // For SVG containers, they always have
    // NS_FRAME_MAY_BE_TRANSFORMED bit.  However, they would be
    // affected by the fragement identifiers in the svgView form at
    // runtime without a new ComputedStyle.
    // For example, layout/reftests/svg/fragmentIdentifier-01.xhtml
    //
    // see https://www.w3.org/TR/SVG/linking.html#SVGFragmentIdentifiers
    result = AGR_MAYBE;
  }

  if (aParent) {
    *aParent = parent;
  }
  return result;
}

nsIFrame* nsDisplayListBuilder::FindAnimatedGeometryRootFrameFor(
    nsIFrame* aFrame, bool& aIsAsync) {
  MOZ_ASSERT(
      nsLayoutUtils::IsAncestorFrameCrossDoc(RootReferenceFrame(), aFrame));
  nsIFrame* cursor = aFrame;
  while (cursor != RootReferenceFrame()) {
    nsIFrame* next;
    if (IsAnimatedGeometryRoot(cursor, aIsAsync, &next) == AGR_YES)
      return cursor;
    cursor = next;
  }
  // Root frame is always an async agr.
  aIsAsync = true;
  return cursor;
}

void nsDisplayListBuilder::RecomputeCurrentAnimatedGeometryRoot() {
  bool isAsync;
  if (*mCurrentAGR != mCurrentFrame &&
      IsAnimatedGeometryRoot(const_cast<nsIFrame*>(mCurrentFrame), isAsync) ==
          AGR_YES) {
    AnimatedGeometryRoot* oldAGR = mCurrentAGR;
    mCurrentAGR = WrapAGRForFrame(const_cast<nsIFrame*>(mCurrentFrame), isAsync,
                                  mCurrentAGR);

    // Iterate the AGR cache and look for any objects that reference the old AGR
    // and check to see if they need to be updated. AGRs can be in the cache
    // multiple times, so we may end up doing the work multiple times for AGRs
    // that don't change.
    for (auto iter = mFrameToAnimatedGeometryRootMap.Iter(); !iter.Done();
         iter.Next()) {
      RefPtr<AnimatedGeometryRoot> cached = iter.UserData();
      if (cached->mParentAGR == oldAGR && cached != mCurrentAGR) {
        // It's possible that this cached AGR struct that has the old AGR as a
        // parent should instead have mCurrentFrame has a parent.
        nsIFrame* parent = FindAnimatedGeometryRootFrameFor(*cached, isAsync);
        MOZ_ASSERT(parent == mCurrentFrame || parent == *oldAGR);
        if (parent == mCurrentFrame) {
          cached->mParentAGR = mCurrentAGR;
        }
      }
    }
  }
}

static nsRect ApplyAllClipNonRoundedIntersection(
    const DisplayItemClipChain* aClipChain, const nsRect& aRect) {
  nsRect result = aRect;
  while (aClipChain) {
    result = aClipChain->mClip.ApplyNonRoundedIntersection(result);
    aClipChain = aClipChain->mParent;
  }
  return result;
}

void nsDisplayListBuilder::AdjustWindowDraggingRegion(nsIFrame* aFrame) {
  if (!mWindowDraggingAllowed || !IsForPainting()) {
    return;
  }

  const nsStyleUIReset* styleUI = aFrame->StyleUIReset();
  if (styleUI->mWindowDragging == StyleWindowDragging::Default) {
    // This frame has the default value and doesn't influence the window
    // dragging region.
    return;
  }

  LayoutDeviceToLayoutDeviceMatrix4x4 referenceFrameToRootReferenceFrame;

  // The const_cast is for nsLayoutUtils::GetTransformToAncestor.
  nsIFrame* referenceFrame =
      const_cast<nsIFrame*>(FindReferenceFrameFor(aFrame));

  if (IsInTransform()) {
    // Only support 2d rectilinear transforms. Transform support is needed for
    // the horizontal flip transform that's applied to the urlbar textbox in
    // RTL mode - it should be able to exclude itself from the draggable region.
    referenceFrameToRootReferenceFrame =
        ViewAs<LayoutDeviceToLayoutDeviceMatrix4x4>(
            nsLayoutUtils::GetTransformToAncestor(referenceFrame,
                                                  mReferenceFrame)
                .GetMatrix());
    Matrix referenceFrameToRootReferenceFrame2d;
    if (!referenceFrameToRootReferenceFrame.Is2D(
            &referenceFrameToRootReferenceFrame2d) ||
        !referenceFrameToRootReferenceFrame2d.IsRectilinear()) {
      return;
    }
  } else {
    MOZ_ASSERT(referenceFrame == mReferenceFrame,
               "referenceFrameToRootReferenceFrame needs to be adjusted");
  }

  // We do some basic visibility checking on the frame's border box here.
  // We intersect it both with the current dirty rect and with the current
  // clip. Either one is just a conservative approximation on its own, but
  // their intersection luckily works well enough for our purposes, so that
  // we don't have to do full-blown visibility computations.
  // The most important case we need to handle is the scrolled-off tab:
  // If the tab bar overflows, tab parts that are clipped by the scrollbox
  // should not be allowed to interfere with the window dragging region. Using
  // just the current DisplayItemClip is not enough to cover this case
  // completely because clips are reset while building stacking context
  // contents, so for example we'd fail to clip frames that have a clip path
  // applied to them. But the current dirty rect doesn't get reset in that
  // case, so we use it to make this case work.
  nsRect borderBox = aFrame->GetRectRelativeToSelf().Intersect(mVisibleRect);
  borderBox += ToReferenceFrame(aFrame);
  const DisplayItemClipChain* clip =
      ClipState().GetCurrentCombinedClipChain(this);
  borderBox = ApplyAllClipNonRoundedIntersection(clip, borderBox);
  if (borderBox.IsEmpty()) {
    return;
  }

  LayoutDeviceRect devPixelBorderBox = LayoutDevicePixel::FromAppUnits(
      borderBox, aFrame->PresContext()->AppUnitsPerDevPixel());

  LayoutDeviceRect transformedDevPixelBorderBox =
      TransformBy(referenceFrameToRootReferenceFrame, devPixelBorderBox);
  transformedDevPixelBorderBox.Round();
  LayoutDeviceIntRect transformedDevPixelBorderBoxInt;

  if (!transformedDevPixelBorderBox.ToIntRect(
          &transformedDevPixelBorderBoxInt)) {
    return;
  }

  LayoutDeviceIntRegion& region =
      styleUI->mWindowDragging == StyleWindowDragging::Drag
          ? mWindowDraggingRegion
          : mWindowNoDraggingRegion;

  if (!IsRetainingDisplayList()) {
    region.OrWith(transformedDevPixelBorderBoxInt);
    return;
  }

  mozilla::gfx::IntRect rect(transformedDevPixelBorderBoxInt.ToUnknownRect());
  if (styleUI->mWindowDragging == StyleWindowDragging::Drag) {
    mRetainedWindowDraggingRegion.Add(aFrame, rect);
  } else {
    mRetainedWindowNoDraggingRegion.Add(aFrame, rect);
  }
}

LayoutDeviceIntRegion nsDisplayListBuilder::GetWindowDraggingRegion() const {
  LayoutDeviceIntRegion result;
  if (!IsRetainingDisplayList()) {
    result.Sub(mWindowDraggingRegion, mWindowNoDraggingRegion);
    return result;
  }

  LayoutDeviceIntRegion dragRegion =
      mRetainedWindowDraggingRegion.ToLayoutDeviceIntRegion();

  LayoutDeviceIntRegion noDragRegion =
      mRetainedWindowNoDraggingRegion.ToLayoutDeviceIntRegion();

  result.Sub(dragRegion, noDragRegion);
  return result;
}

/**
 * Removes modified frames and rects from this WeakFrameRegion.
 */
void nsDisplayListBuilder::WeakFrameRegion::RemoveModifiedFramesAndRects() {
  MOZ_ASSERT(mFrames.Length() == mRects.Length());

  uint32_t i = 0;
  uint32_t length = mFrames.Length();

  while (i < length) {
    auto& wrapper = mFrames[i];

    if (!wrapper.mWeakFrame->IsAlive() ||
        wrapper.mWeakFrame->GetFrame()->IsFrameModified()) {
      // To avoid multiple O(n) shifts in the array, move the last element of
      // the array to the current position and decrease the array length.
      mFrameSet.RemoveEntry(wrapper.mFrame);
      mFrames[i] = std::move(mFrames[length - 1]);
      mRects[i] = std::move(mRects[length - 1]);
      length--;
    } else {
      i++;
    }
  }

  mFrames.TruncateLength(length);
  mRects.TruncateLength(length);
}

void nsDisplayListBuilder::RemoveModifiedWindowRegions() {
  mRetainedWindowDraggingRegion.RemoveModifiedFramesAndRects();
  mRetainedWindowNoDraggingRegion.RemoveModifiedFramesAndRects();
  mWindowExcludeGlassRegion.RemoveModifiedFramesAndRects();
}

void nsDisplayListBuilder::ClearRetainedWindowRegions() {
  mRetainedWindowDraggingRegion.Clear();
  mRetainedWindowNoDraggingRegion.Clear();
  mWindowExcludeGlassRegion.Clear();
}

const uint32_t gWillChangeAreaMultiplier = 3;
static uint32_t GetLayerizationCost(const nsSize& aSize) {
  // There's significant overhead for each layer created from Gecko
  // (IPC+Shared Objects) and from the backend (like an OpenGL texture).
  // Therefore we set a minimum cost threshold of a 64x64 area.
  int minBudgetCost = 64 * 64;

  uint32_t budgetCost = std::max(
      minBudgetCost, nsPresContext::AppUnitsToIntCSSPixels(aSize.width) *
                         nsPresContext::AppUnitsToIntCSSPixels(aSize.height));

  return budgetCost;
}

bool nsDisplayListBuilder::AddToWillChangeBudget(nsIFrame* aFrame,
                                                 const nsSize& aSize) {
  if (mWillChangeBudgetSet.Get(aFrame, nullptr)) {
    return true;  // Already accounted
  }

  nsPresContext* presContext = aFrame->PresContext();
  nsRect area = presContext->GetVisibleArea();
  uint32_t budgetLimit = nsPresContext::AppUnitsToIntCSSPixels(area.width) *
                         nsPresContext::AppUnitsToIntCSSPixels(area.height);
  uint32_t cost = GetLayerizationCost(aSize);

  DocumentWillChangeBudget& budget = mWillChangeBudget.GetOrInsert(presContext);

  bool onBudget =
      (budget.mBudget + cost) / gWillChangeAreaMultiplier < budgetLimit;

  if (onBudget) {
    budget.mBudget += cost;
    mWillChangeBudgetSet.Put(aFrame, FrameWillChangeBudget(presContext, cost));
    aFrame->SetMayHaveWillChangeBudget(true);
  }

  return onBudget;
}

bool nsDisplayListBuilder::IsInWillChangeBudget(nsIFrame* aFrame,
                                                const nsSize& aSize) {
  bool onBudget = AddToWillChangeBudget(aFrame, aSize);

  if (!onBudget) {
    nsString usageStr;
    usageStr.AppendInt(GetLayerizationCost(aSize));

    nsString multiplierStr;
    multiplierStr.AppendInt(gWillChangeAreaMultiplier);

    nsString limitStr;
    nsRect area = aFrame->PresContext()->GetVisibleArea();
    uint32_t budgetLimit = nsPresContext::AppUnitsToIntCSSPixels(area.width) *
                           nsPresContext::AppUnitsToIntCSSPixels(area.height);
    limitStr.AppendInt(budgetLimit);

    const char16_t* params[] = {multiplierStr.get(), limitStr.get()};
    aFrame->PresContext()->Document()->WarnOnceAbout(
        Document::eIgnoringWillChangeOverBudget, false, params,
        ArrayLength(params));
  }
  return onBudget;
}

void nsDisplayListBuilder::RemoveFromWillChangeBudget(nsIFrame* aFrame) {
  FrameWillChangeBudget* frameBudget = mWillChangeBudgetSet.GetValue(aFrame);

  if (!frameBudget) {
    return;
  }

  DocumentWillChangeBudget* budget =
      mWillChangeBudget.GetValue(frameBudget->mPresContext);

  if (budget) {
    budget->mBudget -= frameBudget->mUsage;
  }

  mWillChangeBudgetSet.Remove(aFrame);
}

void nsDisplayListBuilder::ClearWillChangeBudget() {
  mWillChangeBudgetSet.Clear();
  mWillChangeBudget.Clear();
}

#ifdef MOZ_GFX_OPTIMIZE_MOBILE
const float gAGRBudgetAreaMultiplier = 0.3;
#else
const float gAGRBudgetAreaMultiplier = 3.0;
#endif

bool nsDisplayListBuilder::AddToAGRBudget(nsIFrame* aFrame) {
  if (mAGRBudgetSet.Contains(aFrame)) {
    return true;
  }

  const nsPresContext* presContext =
      aFrame->PresContext()->GetRootPresContext();
  if (!presContext) {
    return false;
  }

  const nsRect area = presContext->GetVisibleArea();
  const uint32_t budgetLimit =
      gAGRBudgetAreaMultiplier *
      nsPresContext::AppUnitsToIntCSSPixels(area.width) *
      nsPresContext::AppUnitsToIntCSSPixels(area.height);

  const uint32_t cost = GetLayerizationCost(aFrame->GetSize());
  const bool onBudget = mUsedAGRBudget + cost < budgetLimit;

  if (onBudget) {
    mUsedAGRBudget += cost;
    mAGRBudgetSet.PutEntry(aFrame);
  }

  return onBudget;
}

void nsDisplayListBuilder::EnterSVGEffectsContents(
    nsDisplayList* aHoistedItemsStorage) {
  MOZ_ASSERT(mSVGEffectsBuildingDepth >= 0);
  MOZ_ASSERT(aHoistedItemsStorage);
  if (mSVGEffectsBuildingDepth == 0) {
    MOZ_ASSERT(!mScrollInfoItemsForHoisting);
    mScrollInfoItemsForHoisting = aHoistedItemsStorage;
  }
  mSVGEffectsBuildingDepth++;
}

void nsDisplayListBuilder::ExitSVGEffectsContents() {
  mSVGEffectsBuildingDepth--;
  MOZ_ASSERT(mSVGEffectsBuildingDepth >= 0);
  MOZ_ASSERT(mScrollInfoItemsForHoisting);
  if (mSVGEffectsBuildingDepth == 0) {
    mScrollInfoItemsForHoisting = nullptr;
  }
}

void nsDisplayListBuilder::AppendNewScrollInfoItemForHoisting(
    nsDisplayScrollInfoLayer* aScrollInfoItem) {
  MOZ_ASSERT(ShouldBuildScrollInfoItemsForHoisting());
  MOZ_ASSERT(mScrollInfoItemsForHoisting);
  mScrollInfoItemsForHoisting->AppendToTop(aScrollInfoItem);
}

void nsDisplayListBuilder::BuildCompositorHitTestInfoIfNeeded(
    nsIFrame* aFrame, nsDisplayList* aList, const bool aBuildNew) {
  MOZ_ASSERT(aFrame);
  MOZ_ASSERT(aList);

  if (!BuildCompositorHitTestInfo()) {
    return;
  }

  const CompositorHitTestInfo info = aFrame->GetCompositorHitTestInfo(this);
  if (info == CompositorHitTestInvisibleToHit) {
    return;
  }

  const nsRect area = aFrame->GetCompositorHitTestArea(this);
  if (!aBuildNew && GetHitTestInfo() == info &&
      GetHitTestArea().Contains(area)) {
    return;
  }

  auto* item = MakeDisplayItem<nsDisplayCompositorHitTestInfo>(
      this, aFrame, info, 0, Some(area));

  SetCompositorHitTestInfo(area, info);
  aList->AppendToTop(item);
}

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());
}

static void MoveListTo(nsDisplayList* aList,
                       nsTArray<nsDisplayItem*>* aElements) {
  nsDisplayItem* item;
  while ((item = aList->RemoveBottom()) != nullptr) {
    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;
}

nsRect nsDisplayList::GetClippedBoundsWithRespectToASR(
    nsDisplayListBuilder* aBuilder, const ActiveScrolledRoot* aASR,
    nsRect* aBuildingRect) const {
  nsRect bounds;
  for (nsDisplayItem* i = GetBottom(); i != nullptr; i = i->GetAbove()) {
    nsRect r = i->GetClippedBounds(aBuilder);
    if (aASR != i->GetActiveScrolledRoot() && !r.IsEmpty()) {
      if (Maybe<nsRect> clip = i->GetClipWithRespectToASR(aBuilder, aASR)) {
        r = clip.ref();
      }
    }
    if (aBuildingRect) {
      aBuildingRect->UnionRect(*aBuildingRect, i->GetBuildingRect());
    }
    bounds.UnionRect(bounds, r);
  }
  return bounds;
}

nsRect nsDisplayList::GetBuildingRect() const {
  nsRect result;
  for (nsDisplayItem* i = GetBottom(); i != nullptr; i = i->GetAbove()) {
    result.UnionRect(result, i->GetBuildingRect());
  }
  return result;
}

bool nsDisplayList::ComputeVisibilityForRoot(nsDisplayListBuilder* aBuilder,
                                             nsRegion* aVisibleRegion) {
  AUTO_PROFILER_LABEL("nsDisplayList::ComputeVisibilityForRoot", GRAPHICS);

  nsRegion r;
  const ActiveScrolledRoot* rootASR = nullptr;
  if (gfxPrefs::LayoutUseContainersForRootFrames()) {
    rootASR = aBuilder->ActiveScrolledRootForRootScrollframe();
  }
  r.And(*aVisibleRegion, GetClippedBoundsWithRespectToASR(aBuilder, rootASR));
  return ComputeVisibilityForSublist(aBuilder, aVisibleRegion, r.GetBounds());
}

static nsRegion TreatAsOpaque(nsDisplayItem* aItem,
                              nsDisplayListBuilder* aBuilder) {
  bool snap;
  nsRegion opaque = aItem->GetOpaqueRegion(aBuilder, &snap);
  if (aBuilder->IsForPluginGeometry() &&
      aItem->GetType() != DisplayItemType::TYPE_COMPOSITOR_HITTEST_INFO) {
    // 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->StyleEffects()->mOpacity != 0.0) {
      opaque = aItem->GetBounds(aBuilder, &snap);
    }
  }
  if (opaque.IsEmpty()) {
    return opaque;
  }
  nsRegion opaqueClipped;
  for (auto iter = opaque.RectIter(); !iter.Done(); iter.Next()) {
    opaqueClipped.Or(opaqueClipped,
                     aItem->GetClip().ApproximateIntersectInward(iter.Get()));
  }
  return opaqueClipped;
}

bool nsDisplayList::ComputeVisibilityForSublist(
    nsDisplayListBuilder* aBuilder, nsRegion* aVisibleRegion,
    const nsRect& aListVisibleBounds) {
#ifdef DEBUG
  nsRegion r;
  r.And(*aVisibleRegion, GetBounds(aBuilder));
  // XXX this fails sometimes:
  NS_WARNING_ASSERTION(r.GetBounds().IsEqualInterior(aListVisibleBounds),
                       "bad aListVisibleBounds");
#endif

  bool anyVisible = false;

  AutoTArray<nsDisplayItem*, 512> elements;
  MoveListTo(this, &elements);

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

    if (item->ForceNotVisible() && !item->GetSameCoordinateSystemChildren()) {
      NS_ASSERTION(item->GetBuildingRect().IsEmpty(),
                   "invisible items should have empty vis rect");
      item->SetPaintRect(nsRect());
    } else {
      nsRect bounds = item->GetClippedBounds(aBuilder);

      nsRegion itemVisible;
      itemVisible.And(*aVisibleRegion, bounds);
      item->SetPaintRect(itemVisible.GetBounds());
    }

    if (item->ComputeVisibility(aBuilder, aVisibleRegion)) {
      anyVisible = true;

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

  mIsOpaque = !aVisibleRegion->Intersects(aListVisibleBounds);
  return anyVisible;
}

static bool TriggerPendingAnimationsOnSubDocuments(Document* aDocument,
                                                   void* aReadyTime) {
  PendingAnimationTracker* tracker = aDocument->GetPendingAnimationTracker();
  if (tracker) {
    nsIPresShell* shell = aDocument->GetShell();
    // If paint-suppression is in effect then we haven't finished painting
    // this document yet so we shouldn't start animations
    if (!shell || !shell->IsPaintingSuppressed()) {
      const TimeStamp& readyTime = *static_cast<TimeStamp*>(aReadyTime);
      tracker->TriggerPendingAnimationsOnNextTick(readyTime);
    }
  }
  aDocument->EnumerateSubDocuments(TriggerPendingAnimationsOnSubDocuments,
                                   aReadyTime);
  return true;
}

static void TriggerPendingAnimations(Document* aDocument,
                                     const TimeStamp& aReadyTime) {
  MOZ_ASSERT(!aReadyTime.IsNull(),
             "Animation ready time is not set. Perhaps we're using a layer"
             " manager that doesn't update it");
  TriggerPendingAnimationsOnSubDocuments(aDocument,
                                         const_cast<TimeStamp*>(&aReadyTime));
}

LayerManager* nsDisplayListBuilder::GetWidgetLayerManager(nsView** aView) {
  if (aView) {
    *aView = RootReferenceFrame()->GetView();
  }
  if (RootReferenceFrame() !=
      nsLayoutUtils::GetDisplayRootFrame(RootReferenceFrame())) {
    return nullptr;
  }
  nsIWidget* window = RootReferenceFrame()->GetNearestWidget();
  if (window) {
    return window->GetLayerManager();
  }
  return nullptr;
}

FrameLayerBuilder* nsDisplayList::BuildLayers(nsDisplayListBuilder* aBuilder,
                                              LayerManager* aLayerManager,
                                              uint32_t aFlags,
                                              bool aIsWidgetTransaction) {
  nsIFrame* frame = aBuilder->RootReferenceFrame();
  nsPresContext* presContext = frame->PresContext();
  nsIPresShell* presShell = presContext->PresShell();

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

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

  RefPtr<ContainerLayer> root;
  {
#ifdef MOZ_GECKO_PROFILER
    nsCOMPtr<nsIDocShell> docShell = presContext->GetDocShell();
    AUTO_PROFILER_TRACING_DOCSHELL("Paint", "LayerBuilding", GRAPHICS,
                                   docShell);
#endif

    if (XRE_IsContentProcess() && gfxPrefs::AlwaysPaint()) {
      FrameLayerBuilder::InvalidateAllLayers(aLayerManager);
    }

    if (aIsWidgetTransaction) {
      layerBuilder->DidBeginRetainedLayerTransaction(aLayerManager);
    }

    // Clear any ScrollMetadata that may have been set on the root layer on a
    // previous paint. This paint will set new metrics if necessary, and if we
    // don't clear the old one here, we may be left with extra metrics.
    if (Layer* rootLayer = aLayerManager->GetRoot()) {
      rootLayer->SetScrollMetadata(nsTArray<ScrollMetadata>());
    }

    ContainerLayerParameters containerParameters(presShell->GetResolution(),
                                                 presShell->GetResolution());

    {
      PaintTelemetry::AutoRecord record(PaintTelemetry::Metric::Layerization);

      root = layerBuilder->BuildContainerLayerFor(aBuilder, aLayerManager,
                                                  frame, nullptr, this,
                                                  containerParameters, nullptr);

      if (!record.GetStart().IsNull() && gfxPrefs::LayersDrawFPS()) {
        if (PaintTiming* pt =
                ClientLayerManager::MaybeGetPaintTiming(aLayerManager)) {
          pt->flbMs() = (TimeStamp::Now() - record.GetStart()).ToMilliseconds();
        }
      }
    }

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

    auto callback = [root](ScrollableLayerGuid::ViewID aScrollId) -> bool {
      return nsLayoutUtils::ContainsMetricsWithId(root, aScrollId);
    };
    if (Maybe<ScrollMetadata> rootMetadata = nsLayoutUtils::GetRootMetadata(
            aBuilder, root->Manager(), containerParameters, callback)) {
      root->SetScrollMetadata(rootMetadata.value());
    }

    // NS_WARNING is debug-only, so don't even bother checking the conditions
    // in a release build.
#ifdef DEBUG
    bool usingDisplayport = false;
    if (nsIFrame* rootScrollFrame = presShell->GetRootScrollFrame()) {
      nsIContent* content = rootScrollFrame->GetContent();
      if (content) {
        usingDisplayport = nsLayoutUtils::HasDisplayPort(content);
      }
    }
    if (usingDisplayport &&
        !(root->GetContentFlags() & Layer::CONTENT_OPAQUE) &&
        SpammyLayoutWarningsEnabled()) {
      // See bug 693938, attachment 567017
      NS_WARNING("Transparent content with displayports can be expensive.");
    }
#endif

    aLayerManager->SetRoot(root);
    layerBuilder->WillEndTransaction();
  }
  return layerBuilder;
}

/**
 * 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 PaintedLayers.
 */
already_AddRefed<LayerManager> nsDisplayList::PaintRoot(
    nsDisplayListBuilder* aBuilder, gfxContext* aCtx, uint32_t aFlags) {
  AUTO_PROFILER_LABEL("nsDisplayList::PaintRoot", GRAPHICS);

  RefPtr<LayerManager> layerManager;
  bool widgetTransaction = false;
  bool doBeginTransaction = true;
  nsView* view = nullptr;
  if (aFlags & PAINT_USE_WIDGET_LAYERS) {
    layerManager = aBuilder->GetWidgetLayerManager(&view);
    if (layerManager) {
      layerManager->SetContainsSVG(false);

      doBeginTransaction = !(aFlags & PAINT_EXISTING_TRANSACTION);
      widgetTransaction = true;
    }
  }
  if (!layerManager) {
    if (!aCtx) {
      NS_WARNING("Nowhere to paint into");
      return nullptr;
    }
    layerManager = new BasicLayerManager(BasicLayerManager::BLM_OFFSCREEN);
  }

  nsIFrame* frame = aBuilder->RootReferenceFrame();
  nsPresContext* presContext = frame->PresContext();
  nsIPresShell* presShell = presContext->PresShell();
  Document* document = presShell->GetDocument();

  if (layerManager->GetBackendType() == layers::LayersBackend::LAYERS_WR) {
    if (doBeginTransaction) {
      if (aCtx) {
        if (!layerManager->BeginTransactionWithTarget(aCtx)) {
          return nullptr;
        }
      } else {
        if (!layerManager->BeginTransaction()) {
          return nullptr;
        }
      }
    }

    bool prevIsCompositingCheap =
        aBuilder->SetIsCompositingCheap(layerManager->IsCompositingCheap());
    MaybeSetupTransactionIdAllocator(layerManager, presContext);

    bool sent = false;
    if (aFlags & PAINT_IDENTICAL_DISPLAY_LIST) {
      sent = layerManager->EndEmptyTransaction();
    }

    if (!sent) {
      // Windowed plugins are not supported with WebRender enabled.
      // But PluginGeometry needs to be updated to show plugin.
      // Windowed plugins are going to be removed by Bug 1296400.
      nsRootPresContext* rootPresContext = presContext->GetRootPresContext();
      if (rootPresContext && XRE_IsContentProcess()) {
        if (aBuilder->WillComputePluginGeometry()) {
          rootPresContext->ComputePluginGeometryUpdates(
              aBuilder->RootReferenceFrame(), aBuilder, this);
        }
        // This must be called even if PluginGeometryUpdates were not computed.
        rootPresContext->CollectPluginGeometryUpdates(layerManager);
      }

      auto* wrManager = static_cast<WebRenderLayerManager*>(layerManager.get());

      nsIDocShell* docShell = presContext->GetDocShell();
      nsTArray<wr::FilterOp> wrFilters;
      gfx::Matrix5x4* colorMatrix =
          nsDocShell::Cast(docShell)->GetColorMatrix();
      if (colorMatrix) {
        wrFilters.AppendElement(
            wr::FilterOp::ColorMatrix(colorMatrix->components));
      }

      wrManager->EndTransactionWithoutLayer(this, aBuilder,
                                            std::move(wrFilters));
    }

    // For layers-free mode, we check the invalidation state bits in the
    // EndTransaction. So we clear the invalidation state bits after
    // EndTransaction.
    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())) {
      frame->ClearInvalidationStateBits();
    }

    aBuilder->SetIsCompositingCheap(prevIsCompositingCheap);
    if (document && widgetTransaction) {
      TriggerPendingAnimations(document, layerManager->GetAnimationReadyTime());
    }

    if (presContext->RefreshDriver()->HasScheduleFlush()) {
      presContext->NotifyInvalidation(layerManager->GetLastTransactionId(),
                                      frame->GetRect());
    }

    return layerManager.forget();
  }

  NotifySubDocInvalidationFunc computeInvalidFunc =
      presContext->MayHavePaintEventListenerInSubDocument()
          ? nsPresContext::NotifySubDocInvalidation
          : nullptr;

  UniquePtr<LayerProperties> props;

  bool computeInvalidRect =
      (computeInvalidFunc || (!layerManager->IsCompositingCheap() &&
                              layerManager->NeedsWidgetInvalidation())) &&
      widgetTransaction;

  if (computeInvalidRect) {
    props = LayerProperties::CloneFrom(layerManager->GetRoot());
  }

  if (doBeginTransaction) {
    if (aCtx) {
      if (!layerManager->BeginTransactionWithTarget(aCtx)) {
        return nullptr;
      }
    } else {
      if (!layerManager->BeginTransaction()) {
        return nullptr;
      }
    }
  }

  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;
    }
  }

  MaybeSetupTransactionIdAllocator(layerManager, presContext);

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

  bool sent = false;
  if (aFlags & PAINT_IDENTICAL_DISPLAY_LIST) {
    sent = layerManager->EndEmptyTransaction(flags);
  }

  if (!sent) {
    layerBuilder =
        BuildLayers(aBuilder, layerManager, aFlags, widgetTransaction);

    if (!layerBuilder) {
      layerManager->SetUserData(&gLayerManagerLayerBuilder, oldBuilder);
      return nullptr;
    }

    // If this is the content process, we ship plugin geometry updates over with
    // layer updates, so calculate that now before we call EndTransaction.
    nsRootPresContext* rootPresContext = presContext->GetRootPresContext();
    if (rootPresContext && XRE_IsContentProcess()) {
      if (aBuilder->WillComputePluginGeometry()) {
        rootPresContext->ComputePluginGeometryUpdates(
            aBuilder->RootReferenceFrame(), aBuilder, this);
      }
      // The layer system caches plugin configuration information for forwarding
      // with layer updates which needs to get set during reflow. This must be
      // called even if there are no windowed plugins in the page.
      rootPresContext->CollectPluginGeometryUpdates(layerManager);
    }

    layerManager->EndTransaction(FrameLayerBuilder::DrawPaintedLayer, aBuilder,
                                 flags);
    layerBuilder->DidEndTransaction();
  }

  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())) {
    frame->ClearInvalidationStateBits();
  }

  aBuilder->SetIsCompositingCheap(temp);

  if (document && widgetTransaction) {
    TriggerPendingAnimations(document, layerManager->GetAnimationReadyTime());
  }

  nsIntRegion invalid;
  if (props) {
    if (!props->ComputeDifferences(layerManager->GetRoot(), invalid,
                                   computeInvalidFunc)) {
      invalid = nsIntRect::MaxIntRect();
    }
  } else if (widgetTransaction) {
    LayerProperties::ClearInvalidations(layerManager->GetRoot());
  }

  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(layerManager->GetLastTransactionId(),
                                        bounds);
      }
    } else if (shouldInvalidate) {
      view->GetViewManager()->InvalidateView(view);
    }
  }

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

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;
  mLength--;
  return item;
}

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

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

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

static bool IsFrameReceivingPointerEvents(nsIFrame* aFrame) {
  return NS_STYLE_POINTER_EVENTS_NONE !=
         aFrame->StyleUI()->GetEffectivePointerEvents(aFrame);
}

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

  bool operator<(const FramesWithDepth& aOther) const {
    if (!FuzzyEqual(mDepth, aOther.mDepth, 0.1f)) {
      // 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
static 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->AppendElements(std::move(aSource[i].mFrames));
  }
  aSource.Clear();
}

void nsDisplayList::HitTest(nsDisplayListBuilder* aBuilder, const nsRect& aRect,
                            nsDisplayItem::HitTestState* aState,
                            nsTArray<nsIFrame*>* aOutFrames) const {
  nsDisplayItem* item;

  if (aState->mInPreserves3D) {
    // Collect leaves of the current 3D rendering context.
    for (item = GetBottom(); item; item = item->GetAbove()) {
      auto itemType = item->GetType();
      if (itemType != DisplayItemType::TYPE_TRANSFORM ||
          !static_cast<nsDisplayTransform*>(item)->IsLeafOf3DContext()) {
        item->HitTest(aBuilder, aRect, aState, aOutFrames);
      } else {
        // One of leaves in the current 3D rendering context.
        aState->mItemBuffer.AppendElement(item);
      }
    }
    return;
  }

  int32_t itemBufferStart = aState->mItemBuffer.Length();
  for (item = GetBottom(); item; item = item->GetAbove()) {
    aState->mItemBuffer.AppendElement(item);
  }

  AutoTArray<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);
    auto itemType = item->GetType();
    bool same3DContext =
        (itemType == DisplayItemType::TYPE_TRANSFORM &&
         static_cast<nsDisplayTransform*>(item)->IsParticipating3DContext()) ||
        (itemType == DisplayItemType::TYPE_PERSPECTIVE &&
         item->Frame()->Extend3DContext());
    if (same3DContext &&
        (itemType != DisplayItemType::TYPE_TRANSFORM ||
         !static_cast<nsDisplayTransform*>(item)->IsLeafOf3DContext())) {
      if (!item->GetClip().MayIntersect(aRect)) {
        continue;
      }
      AutoTArray<nsIFrame*, 1> neverUsed;
      // Start gethering leaves of the 3D rendering context, and
      // append leaves at the end of mItemBuffer.  Leaves are
      // processed at following iterations.
      aState->mInPreserves3D = true;
      item->HitTest(aBuilder, aRect, aState, &neverUsed);
      aState->mInPreserves3D = false;
      i = aState->mItemBuffer.Length();
      continue;
    }
    if (same3DContext || item->GetClip().MayIntersect(r)) {
      AutoTArray<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() == DisplayItemType::TYPE_TRANSFORM &&
          static_cast<nsDisplayTransform*>(item)->IsLeafOf3DContext()) {
        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);
        // Filter out some frames depending on the type of hittest
        // we are doing. For visibility tests, pass through all frames.
        // For pointer tests, only pass through frames that are styled
        // to receive pointer events.
        if (aBuilder->HitTestIsForVisibility() ||
            (!GetMouseThrough(f) && IsFrameReceivingPointerEvents(f))) {
          writeFrames->AppendElement(f);
        }
      }

      if (aBuilder->HitTestIsForVisibility() &&
          item->GetOpaqueRegion(aBuilder, &snap).Contains(aRect)) {
        // We're exiting early, so pop the remaining items off the buffer.
        aState->mItemBuffer.SetLength(itemBufferStart);
        break;
      }
    }
  }
  // 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 nsIContent* FindContentInDocument(nsDisplayItem* aItem, Document* 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;
}

struct ZSortItem {
  nsDisplayItem* item;
  int32_t zIndex;

  explicit ZSortItem(nsDisplayItem* aItem)
      : item(aItem), zIndex(aItem->ZIndex()) {}

  operator nsDisplayItem*() { return item; }
};

struct ZOrderComparator {
  bool operator()(const ZSortItem& aLeft, const ZSortItem& aRight) const {
    // Note that we can't just take the difference of the two
    // z-indices here, because that might overflow a 32-bit int.
    return aLeft.zIndex < aRight.zIndex;
  }
};

void nsDisplayList::SortByZOrder() { Sort<ZSortItem>(ZOrderComparator()); }

struct ContentComparator {
  nsIContent* mCommonAncestor;

  explicit ContentComparator(nsIContent* aCommonAncestor)
      : mCommonAncestor(aCommonAncestor) {}

  bool operator()(nsDisplayItem* aLeft, nsDisplayItem* aRight) const {
    // 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.
    Document* commonAncestorDoc = mCommonAncestor->OwnerDoc();
    nsIContent* content1 = FindContentInDocument(aLeft, commonAncestorDoc);
    nsIContent* content2 = FindContentInDocument(aRight, commonAncestorDoc);
    if (!content1 || !content2) {
      NS_ERROR("Document trees are mixed up!");
      // Something weird going on
      return true;
    }
    return nsLayoutUtils::CompareTreePosition(content1, content2,
                                              mCommonAncestor) < 0;
  }
};

void nsDisplayList::SortByContentOrder(nsIContent* aCommonAncestor) {
  Sort<nsDisplayItem*>(ContentComparator(aCommonAncestor));
}

nsDisplayItem::nsDisplayItem(nsDisplayListBuilder* aBuilder, nsIFrame* aFrame)
    : nsDisplayItem(aBuilder, aFrame, aBuilder->CurrentActiveScrolledRoot()) {}

nsDisplayItem::nsDisplayItem(nsDisplayListBuilder* aBuilder, nsIFrame* aFrame,
                             const ActiveScrolledRoot* aActiveScrolledRoot,
                             bool aAnonymous)
    : mFrame(aFrame),
      mActiveScrolledRoot(aActiveScrolledRoot),
      mAnimatedGeometryRoot(nullptr),
      mForceNotVisible(aBuilder->IsBuildingInvisibleItems()),
      mDisableSubpixelAA(false),
      mReusedItem(false),
      mBackfaceHidden(mFrame->In3DContextAndBackfaceIsHidden()),
      mPaintRectValid(false)
#ifdef MOZ_DUMP_PAINTING
      ,
      mPainted(false)
#endif
{
  MOZ_COUNT_CTOR(nsDisplayItem);
  if (aBuilder->IsRetainingDisplayList() && !aAnonymous) {
    mFrame->AddDisplayItem(this);
  }
  mReferenceFrame = aBuilder->FindReferenceFrameFor(aFrame, &mToReferenceFrame);
  // This can return the wrong result if the item override
  // ShouldFixToViewport(), the item needs to set it again in its constructor.
  mAnimatedGeometryRoot = aBuilder->FindAnimatedGeometryRootFor(aFrame);
  MOZ_ASSERT(nsLayoutUtils::IsAncestorFrameCrossDoc(
                 aBuilder->RootReferenceFrame(), *mAnimatedGeometryRoot),
             "Bad");
  NS_ASSERTION(
      aBuilder->GetVisibleRect().width >= 0 || !aBuilder->IsForPainting(),
      "visible rect not set");

  nsDisplayItem::SetClipChain(
      aBuilder->ClipState().GetCurrentCombinedClipChain(aBuilder), true);

  // The visible rect is for mCurrentFrame, so we have to use
  // mCurrentOffsetToReferenceFrame
  nsRect visible = aBuilder->GetVisibleRect() +
                   aBuilder->GetCurrentFrameOffsetToReferenceFrame();
  SetBuildingRect(visible);
}

/* 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 ZIndexForFrame(nsIFrame* aFrame) {
  if (!aFrame->IsAbsPosContainingBlock() && !aFrame->IsFlexOrGridItem())
    return 0;

  const nsStylePosition* position = aFrame->StylePosition();
  if (position->mZIndex.GetUnit() == eStyleUnit_Integer)
    return position->mZIndex.GetIntValue();

  // sort the auto and 0 elements together
  return 0;
}

int32_t nsDisplayItem::ZIndex() const { return ZIndexForFrame(mFrame); }

bool nsDisplayItem::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                      nsRegion* aVisibleRegion) {
  return !GetPaintRect().IsEmpty() &&
         !IsInvisibleInRect(aVisibleRegion->GetBounds());
}

bool nsDisplayItem::RecomputeVisibility(nsDisplayListBuilder* aBuilder,
                                        nsRegion* aVisibleRegion) {
  if (mForceNotVisible && !GetSameCoordinateSystemChildren()) {
    // mForceNotVisible wants to ensure that this display item doesn't render
    // anything itself. If this item has contents, then we obviously want to
    // render those, so we don't need this check in that case.
    NS_ASSERTION(GetBuildingRect().IsEmpty(),
                 "invisible items without children should have empty vis rect");
    SetPaintRect(nsRect());
  } else {
    bool snap;
    nsRect bounds = GetBounds(aBuilder, &snap);

    nsRegion itemVisible;
    itemVisible.And(*aVisibleRegion, bounds);
    SetPaintRect(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)) {
    SetPaintRect(nsRect());
    return false;
  }

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

void nsDisplayItem::SetClipChain(const DisplayItemClipChain* aClipChain,
                                 bool aStore) {
  mClipChain = aClipChain;
  mClip = DisplayItemClipChain::ClipForASR(aClipChain, mActiveScrolledRoot);

  if (aStore) {
    mState.mClipChain = mClipChain;
    mState.mClip = mClip;
  }
}

Maybe<nsRect> nsDisplayItem::GetClipWithRespectToASR(
    nsDisplayListBuilder* aBuilder, const ActiveScrolledRoot* aASR) const {
  if (const DisplayItemClip* clip =
          DisplayItemClipChain::ClipForASR(GetClipChain(), aASR)) {
    return Some(clip->GetClipRect());
  }
#ifdef DEBUG
  if (!gfxPrefs::LayoutUseContainersForRootFrames()) {
    MOZ_ASSERT(false, "item should have finite clip with respect to aASR");
  }
#endif
  return Nothing();
}

void nsDisplayItem::FuseClipChainUpTo(nsDisplayListBuilder* aBuilder,
                                      const ActiveScrolledRoot* aASR) {
  mClipChain = aBuilder->FuseClipChainUpTo(mClipChain, aASR);

  if (mClipChain) {
    mClip = &mClipChain->mClip;
  } else {
    mClip = nullptr;
  }
}

bool nsDisplayItem::ShouldUseAdvancedLayer(LayerManager* aManager,
                                           PrefFunc aFunc) const {
  return CanUseAdvancedLayer(aManager) ? aFunc() : false;
}

bool nsDisplayItem::CanUseAdvancedLayer(LayerManager* aManager) const {
  return gfxPrefs::LayersAdvancedBasicLayerEnabled() || !aManager ||
         aManager->GetBackendType() == layers::LayersBackend::LAYERS_WR;
}

static const DisplayItemClipChain* FindCommonAncestorClipForIntersection(
    const DisplayItemClipChain* aOne, const DisplayItemClipChain* aTwo) {
  for (const ActiveScrolledRoot* asr =
           ActiveScrolledRoot::PickDescendant(aOne->mASR, aTwo->mASR);
       asr; asr = asr->mParent) {
    if (aOne == aTwo) {
      return aOne;
    }
    if (aOne->mASR == asr) {
      aOne = aOne->mParent;
    }
    if (aTwo->mASR == asr) {
      aTwo = aTwo->mParent;
    }
    if (!aOne) {
      return aTwo;
    }
    if (!aTwo) {
      return aOne;
    }
  }
  return nullptr;
}

void nsDisplayItem::IntersectClip(nsDisplayListBuilder* aBuilder,
                                  const DisplayItemClipChain* aOther,
                                  bool aStore) {
  if (!aOther || mClipChain == aOther) {
    return;
  }

  // aOther might be a reference to a clip on the stack. We need to make sure
  // that CreateClipChainIntersection will allocate the actual intersected
  // clip in the builder's arena, so for the mClipChain == nullptr case,
  // we supply nullptr as the common ancestor so that
  // CreateClipChainIntersection clones the whole chain.
  const DisplayItemClipChain* ancestorClip =
      mClipChain ? FindCommonAncestorClipForIntersection(mClipChain, aOther)
                 : nullptr;

  SetClipChain(
      aBuilder->CreateClipChainIntersection(ancestorClip, mClipChain, aOther),
      aStore);
}

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

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

LayerState nsDisplaySolidColor::GetLayerState(
    nsDisplayListBuilder* aBuilder, LayerManager* aManager,
    const ContainerLayerParameters& aParameters) {
  if (ForceActiveLayers()) {
    return LAYER_ACTIVE;
  }

  return LAYER_NONE;
}

already_AddRefed<Layer> nsDisplaySolidColor::BuildLayer(
    nsDisplayListBuilder* aBuilder, LayerManager* aManager,
    const ContainerLayerParameters& aContainerParameters) {
  RefPtr<ColorLayer> layer = static_cast<ColorLayer*>(
      aManager->GetLayerBuilder()->GetLeafLayerFor(aBuilder, this));
  if (!layer) {
    layer = aManager->CreateColorLayer();
    if (!layer) {
      return nullptr;
    }
  }
  layer->SetColor(gfx::Color::FromABGR(mColor));

  const int32_t appUnitsPerDevPixel =
      mFrame->PresContext()->AppUnitsPerDevPixel();
  layer->SetBounds(mBounds.ToNearestPixels(appUnitsPerDevPixel));
  layer->SetBaseTransform(gfx::Matrix4x4::Translation(
      aContainerParameters.mOffset.x, aContainerParameters.mOffset.y, 0));

  return layer.forget();
}

void nsDisplaySolidColor::Paint(nsDisplayListBuilder* aBuilder,
                                gfxContext* aCtx) {
  int32_t appUnitsPerDevPixel = mFrame->PresContext()->AppUnitsPerDevPixel();
  DrawTarget* drawTarget = aCtx->GetDrawTarget();
  Rect rect =
      NSRectToSnappedRect(GetPaintRect(), appUnitsPerDevPixel, *drawTarget);
  drawTarget->FillRect(rect, ColorPattern(ToDeviceColor(mColor)));
}

void nsDisplaySolidColor::WriteDebugInfo(std::stringstream& aStream) {
  aStream << " (rgba " << (int)NS_GET_R(mColor) << "," << (int)NS_GET_G(mColor)
          << "," << (int)NS_GET_B(mColor) << "," << (int)NS_GET_A(mColor)
          << ")";
}

bool nsDisplaySolidColor::CreateWebRenderCommands(
    mozilla::wr::DisplayListBuilder& aBuilder,
    mozilla::wr::IpcResourceUpdateQueue& aResources,
    const StackingContextHelper& aSc,
    mozilla::layers::RenderRootStateManager* aManager,
    nsDisplayListBuilder* aDisplayListBuilder) {
  LayoutDeviceRect bounds = LayoutDeviceRect::FromAppUnits(
      mBounds, mFrame->PresContext()->AppUnitsPerDevPixel());
  wr::LayoutRect roundedRect = wr::ToRoundedLayoutRect(bounds);

  aBuilder.PushRect(roundedRect, roundedRect, !BackfaceIsHidden(),
                    wr::ToColorF(ToDeviceColor(mColor)));

  return true;
}

nsRect nsDisplaySolidColorRegion::GetBounds(nsDisplayListBuilder* aBuilder,
                                            bool* aSnap) const {
  *aSnap = true;
  return mRegion.GetBounds();
}

void nsDisplaySolidColorRegion::Paint(nsDisplayListBuilder* aBuilder,
                                      gfxContext* aCtx) {
  int32_t appUnitsPerDevPixel = mFrame->PresContext()->AppUnitsPerDevPixel();
  DrawTarget* drawTarget = aCtx->GetDrawTarget();
  ColorPattern color(mColor);
  for (auto iter = mRegion.RectIter(); !iter.Done(); iter.Next()) {
    Rect rect =
        NSRectToSnappedRect(iter.Get(), appUnitsPerDevPixel, *drawTarget);
    drawTarget->FillRect(rect, color);
  }
}

void nsDisplaySolidColorRegion::WriteDebugInfo(std::stringstream& aStream) {
  aStream << " (rgba " << int(mColor.r * 255) << "," << int(mColor.g * 255)
          << "," << int(mColor.b * 255) << "," << mColor.a << ")";
}

bool nsDisplaySolidColorRegion::CreateWebRenderCommands(
    mozilla::wr::DisplayListBuilder& aBuilder,
    mozilla::wr::IpcResourceUpdateQueue& aResources,
    const StackingContextHelper& aSc,
    mozilla::layers::RenderRootStateManager* aManager,
    nsDisplayListBuilder* aDisplayListBuilder) {
  for (auto iter = mRegion.RectIter(); !iter.Done(); iter.Next()) {
    nsRect rect = iter.Get();
    LayoutDeviceRect layerRects = LayoutDeviceRect::FromAppUnits(
        rect, mFrame->PresContext()->AppUnitsPerDevPixel());
    wr::LayoutRect roundedRect = wr::ToRoundedLayoutRect(layerRects);
    aBuilder.PushRect(roundedRect, roundedRect, !BackfaceIsHidden(),
                      wr::ToColorF(ToDeviceColor(mColor)));
  }

  return true;
}

static void RegisterThemeGeometry(nsDisplayListBuilder* aBuilder,
                                  nsDisplayItem* aItem, nsIFrame* aFrame,
                                  nsITheme::ThemeGeometryType aType) {
  if (aBuilder->IsInChromeDocumentOrPopup() && !aBuilder->IsInTransform()) {
    nsIFrame* displayRoot = nsLayoutUtils::GetDisplayRootFrame(aFrame);
    nsPoint offset = aBuilder->IsInSubdocument()
                         ? aBuilder->ToReferenceFrame(aFrame)
                         : aFrame->GetOffsetTo(displayRoot);
    nsRect borderBox = nsRect(offset, aFrame->GetSize());
    aBuilder->RegisterThemeGeometry(
        aType, aItem,
        LayoutDeviceIntRect::FromUnknownRect(borderBox.ToNearestPixels(
            aFrame->PresContext()->AppUnitsPerDevPixel())));
  }
}

// Return the bounds of the viewport relative to |aFrame|'s reference frame.
// Returns Nothing() if transforming into |aFrame|'s coordinate space fails.
static Maybe<nsRect> GetViewportRectRelativeToReferenceFrame(
    nsDisplayListBuilder* aBuilder, nsIFrame* aFrame) {
  nsIFrame* rootFrame = aFrame->PresShell()->GetRootFrame();
  nsRect rootRect = rootFrame->GetRectRelativeToSelf();
  if (nsLayoutUtils::TransformRect(rootFrame, aFrame, rootRect) ==
      nsLayoutUtils::TRANSFORM_SUCCEEDED) {
    return Some(rootRect + aBuilder->ToReferenceFrame(aFrame));
  }
  return Nothing();
}

/* static */ nsDisplayBackgroundImage::InitData
nsDisplayBackgroundImage::GetInitData(nsDisplayListBuilder* aBuilder,
                                      nsIFrame* aFrame, uint32_t aLayer,
                                      const nsRect& aBackgroundRect,
                                      ComputedStyle* aBackgroundStyle) {
  nsPresContext* presContext = aFrame->PresContext();
  uint32_t flags = aBuilder->GetBackgroundPaintFlags();
  const nsStyleImageLayers::Layer& layer =
      aBackgroundStyle->StyleBackground()->mImage.mLayers[aLayer];

  bool isTransformedFixed;
  nsBackgroundLayerState state = nsCSSRendering::PrepareImageLayer(
      presContext, aFrame, flags, aBackgroundRect, aBackgroundRect, layer,
      &isTransformedFixed);

  // background-attachment:fixed is treated as background-attachment:scroll
  // if it's affected by a transform.
  // See https://www.w3.org/Bugs/Public/show_bug.cgi?id=17521.
  bool shouldTreatAsFixed =
      layer.mAttachment == StyleImageLayerAttachment::Fixed &&
      !isTransformedFixed;

  bool shouldFixToViewport = shouldTreatAsFixed && !layer.mImage.IsEmpty();
  bool isRasterImage = state.mImageRenderer.IsRasterImage();
  nsCOMPtr<imgIContainer> image;
  if (isRasterImage) {
    image = state.mImageRenderer.GetImage();
  }
  return InitData{aBuilder,         aFrame,
                  aBackgroundStyle, image,
                  aBackgroundRect,  state.mFillArea,
                  state.mDestArea,  aLayer,
                  isRasterImage,    shouldFixToViewport};
}

nsDisplayBackgroundImage::nsDisplayBackgroundImage(
    nsDisplayListBuilder* aBuilder, const InitData& aInitData,
    nsIFrame* aFrameForBounds)
    : nsDisplayImageContainer(aBuilder, aInitData.frame),
      mBackgroundStyle(aInitData.backgroundStyle),
      mImage(aInitData.image),
      mDependentFrame(nullptr),
      mBackgroundRect(aInitData.backgroundRect),
      mFillRect(aInitData.fillArea),
      mDestRect(aInitData.destArea),
      mLayer(aInitData.layer),
      mIsRasterImage(aInitData.isRasterImage),
      mShouldFixToViewport(aInitData.shouldFixToViewport),
      mImageFlags(0) {
  MOZ_COUNT_CTOR(nsDisplayBackgroundImage);

  mBounds = GetBoundsInternal(aInitData.builder, aFrameForBounds);
  if (mShouldFixToViewport) {
    mAnimatedGeometryRoot =
        aInitData.builder->FindAnimatedGeometryRootFor(this);

    // Expand the item's visible rect to cover the entire bounds, limited to the
    // viewport rect. This is necessary because the background's clip can move
    // asynchronously.
    if (Maybe<nsRect> viewportRect = GetViewportRectRelativeToReferenceFrame(
            aInitData.builder, mFrame)) {
      SetBuildingRect(mBounds.Intersect(*viewportRect));
    }
  }
}

nsDisplayBackgroundImage::~nsDisplayBackgroundImage() {
#ifdef NS_BUILD_REFCNT_LOGGING
  MOZ_COUNT_DTOR(nsDisplayBackgroundImage);
#endif
  if (mDependentFrame) {
    mDependentFrame->RemoveDisplayItem(this);
  }
}

static nsIFrame* GetBackgroundComputedStyleFrame(nsIFrame* aFrame) {
  nsIFrame* f;
  if (!nsCSSRendering::FindBackgroundFrame(aFrame, &f)) {
    // 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()->HasAppearance()) {
      return nullptr;
    }

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

    f = aFrame;
  }
  return f;
}

static void SetBackgroundClipRegion(
    DisplayListClipState::AutoSaveRestore& aClipState, nsIFrame* aFrame,
    const nsPoint& aToReferenceFrame, const nsStyleImageLayers::Layer& aLayer,
    const nsRect& aBackgroundRect, bool aWillPaintBorder) {
  nsCSSRendering::ImageLayerClipState clip;
  nsCSSRendering::GetImageLayerClip(
      aLayer, aFrame, *aFrame->StyleBorder(), aBackgroundRect, aBackgroundRect,
      aWillPaintBorder, aFrame->PresContext()->AppUnitsPerDevPixel(), &clip);

  if (clip.mHasAdditionalBGClipArea) {
    aClipState.ClipContentDescendants(
        clip.mAdditionalBGClipArea, clip.mBGClipArea,
        clip.mHasRoundedCorners ? clip.mRadii : nullptr);
  } else {
    aClipState.ClipContentDescendants(
        clip.mBGClipArea, clip.mHasRoundedCorners ? clip.mRadii : nullptr);
  }
}

/**
 * This is used for the find bar highlighter overlay. It's only accessible
 * through the AnonymousContent API, so it's not exposed to general web pages.
 */
static bool SpecialCutoutRegionCase(nsDisplayListBuilder* aBuilder,
                                    nsIFrame* aFrame,
                                    const nsRect& aBackgroundRect,
                                    nsDisplayList* aList, nscolor aColor) {
  nsIContent* content = aFrame->GetContent();
  if (!content) {
    return false;
  }

  void* cutoutRegion = content->GetProperty(nsGkAtoms::cutoutregion);
  if (!cutoutRegion) {
    return false;
  }

  if (NS_GET_A(aColor) == 0) {
    return true;
  }

  nsRegion region;
  region.Sub(aBackgroundRect, *static_cast<nsRegion*>(cutoutRegion));
  region.MoveBy(aBuilder->ToReferenceFrame(aFrame));
  aList->AppendToTop(MakeDisplayItem<nsDisplaySolidColorRegion>(
      aBuilder, aFrame, region, aColor));

  return true;
}

/*static*/ bool nsDisplayBackgroundImage::AppendBackgroundItemsToTop(
    nsDisplayListBuilder* aBuilder, nsIFrame* aFrame,
    const nsRect& aBackgroundRect, nsDisplayList* aList,
    bool aAllowWillPaintBorderOptimization, ComputedStyle* aComputedStyle,
    const nsRect& aBackgroundOriginRect, nsIFrame* aSecondaryReferenceFrame) {
  ComputedStyle* bgSC = aComputedStyle;
  const nsStyleBackground* bg = nullptr;
  nsRect bgRect = aBackgroundRect + aBuilder->ToReferenceFrame(aFrame);
  nsRect bgOriginRect = bgRect;
  if (!aBackgroundOriginRect.IsEmpty()) {
    bgOriginRect = aBackgroundOriginRect + aBuilder->ToReferenceFrame(aFrame);
  }
  nsPresContext* presContext = aFrame->PresContext();
  bool isThemed = aFrame->IsThemed();
  nsIFrame* dependentFrame = nullptr;
  if (!isThemed) {
    if (!bgSC) {
      dependentFrame = GetBackgroundComputedStyleFrame(aFrame);
      if (dependentFrame) {
        bgSC = dependentFrame->Style();
        if (dependentFrame == aFrame) {
          dependentFrame = nullptr;
        }
      }
    }
    if (bgSC) {
      bg = bgSC->StyleBackground();
    }
  }

  bool drawBackgroundColor = false;
  // Dummy initialisation to keep Valgrind/Memcheck happy.
  // See bug 1122375 comment 1.
  nscolor color = NS_RGBA(0, 0, 0, 0);
  if (!nsCSSRendering::IsCanvasFrame(aFrame) && bg) {
    bool drawBackgroundImage;
    color = nsCSSRendering::DetermineBackgroundColor(
        presContext, bgSC, aFrame, drawBackgroundImage, drawBackgroundColor);
  }

  if (SpecialCutoutRegionCase(aBuilder, aFrame, aBackgroundRect, aList,
                              color)) {
    return false;
  }

  const nsStyleBorder* borderStyle = aFrame->StyleBorder();
  const nsStyleEffects* effectsStyle = aFrame->StyleEffects();
  bool hasInsetShadow = effectsStyle->mBoxShadow &&
                        effectsStyle->mBoxShadow->HasShadowWithInset(true);
  bool willPaintBorder = aAllowWillPaintBorderOptimization && !isThemed &&
                         !hasInsetShadow && borderStyle->HasBorder();

  nsPoint toRef = aBuilder->ToReferenceFrame(aFrame);

  // 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()) {
    Maybe<DisplayListClipState::AutoSaveRestore> clipState;
    nsRect bgColorRect = bgRect;
    if (bg && !aBuilder->IsForEventDelivery()) {
      // Disable the will-paint-border optimization for background
      // colors with no border-radius. Enabling it for background colors
      // doesn't help much (there are no tiling issues) and clipping the
      // background breaks detection of the element's border-box being
      // opaque. For nonzero border-radius we still need it because we
      // want to inset the background if possible to avoid antialiasing
      // artifacts along the rounded corners.
      bool useWillPaintBorderOptimization =
          willPaintBorder &&
          nsLayoutUtils::HasNonZeroCorner(borderStyle->mBorderRadius);

      nsCSSRendering::ImageLayerClipState clip;
      nsCSSRendering::GetImageLayerClip(
          bg->BottomLayer(), aFrame, *aFrame->StyleBorder(), bgRect, bgRect,
          useWillPaintBorderOptimization,
          aFrame->PresContext()->AppUnitsPerDevPixel(), &clip);

      bgColorRect = bgColorRect.Intersect(clip.mBGClipArea);
      if (clip.mHasAdditionalBGClipArea) {
        bgColorRect = bgColorRect.Intersect(clip.mAdditionalBGClipArea);
      }
      if (clip.mHasRoundedCorners) {
        clipState.emplace(aBuilder);
        clipState->ClipContentDescendants(clip.mBGClipArea, clip.mRadii);
      }
    }
    nsDisplayBackgroundColor* bgItem;
    if (aSecondaryReferenceFrame) {
      bgItem = MakeDisplayItem<nsDisplayTableBackgroundColor>(
          aBuilder, aSecondaryReferenceFrame, bgColorRect, bgSC,
          drawBackgroundColor ? color : NS_RGBA(0, 0, 0, 0), aFrame);
    } else {
      bgItem = MakeDisplayItem<nsDisplayBackgroundColor>(
          aBuilder, aFrame, bgColorRect, bgSC,
          drawBackgroundColor ? color : NS_RGBA(0, 0, 0, 0));
    }
    bgItem->SetDependentFrame(aBuilder, dependentFrame);
    bgItemList.AppendToTop(bgItem);
  }

  if (isThemed) {
    nsITheme* theme = presContext->GetTheme();
    if (theme->NeedToClearBackgroundBehindWidget(
            aFrame, aFrame->StyleDisplay()->mAppearance) &&
        aBuilder->IsInChromeDocumentOrPopup() && !aBuilder->IsInTransform()) {
      bgItemList.AppendToTop(
          MakeDisplayItem<nsDisplayClearBackground>(aBuilder, aFrame));
    }
    if (aSecondaryReferenceFrame) {
      nsDisplayTableThemedBackground* bgItem =
          MakeDisplayItem<nsDisplayTableThemedBackground>(
              aBuilder, aSecondaryReferenceFrame, bgRect, aFrame);
      bgItem->Init(aBuilder);
      bgItemList.AppendToTop(bgItem);
    } else {
      nsDisplayThemedBackground* bgItem =
          MakeDisplayItem<nsDisplayThemedBackground>(aBuilder, aFrame, bgRect);
      bgItem->Init(aBuilder);
      bgItemList.AppendToTop(bgItem);
    }
    aList->AppendToTop(&bgItemList);
    return true;
  }

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

  const ActiveScrolledRoot* asr = aBuilder->CurrentActiveScrolledRoot();

  bool needBlendContainer = false;

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

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

    DisplayListClipState::AutoSaveRestore clipState(aBuilder);
    if (!aBuilder->IsForEventDelivery()) {
      const nsStyleImageLayers::Layer& layer = bg->mImage.mLayers[i];
      SetBackgroundClipRegion(clipState, aFrame, toRef, layer, bgRect,
                              willPaintBorder);
    }

    nsDisplayList thisItemList;
    nsDisplayBackgroundImage::InitData bgData =
        nsDisplayBackgroundImage::GetInitData(aBuilder, aFrame, i, bgOriginRect,
                                              bgSC);

    if (bgData.shouldFixToViewport) {
      auto* displayData = aBuilder->GetCurrentFixedBackgroundDisplayData();
      nsDisplayListBuilder::AutoBuildingDisplayList buildingDisplayList(
          aBuilder, aFrame, aBuilder->GetVisibleRect(),
          aBuilder->GetDirtyRect(), false);

      nsDisplayListBuilder::AutoCurrentActiveScrolledRootSetter asrSetter(
          aBuilder);
      if (displayData) {
        asrSetter.SetCurrentActiveScrolledRoot(
            displayData->mContainingBlockActiveScrolledRoot);
        if (nsLayoutUtils::UsesAsyncScrolling(aFrame)) {
          // Override the dirty rect on the builder to be the dirty rect of
          // the viewport.
          // displayData->mDirtyRect is relative to the presshell's viewport
          // frame (the root frame), and we need it to be relative to aFrame.
          nsIFrame* rootFrame =
              aBuilder->CurrentPresShellState()->mPresShell->GetRootFrame();
          // There cannot be any transforms between aFrame and rootFrame
          // because then bgData.shouldFixToViewport would have been false.
          nsRect visibleRect =
              displayData->mVisibleRect + aFrame->GetOffsetTo(rootFrame);
          aBuilder->SetVisibleRect(visibleRect);
          nsRect dirtyRect =
              displayData->mDirtyRect + aFrame->GetOffsetTo(rootFrame);
          aBuilder->SetDirtyRect(dirtyRect);
        }
      }
      nsDisplayBackgroundImage* bgItem = nullptr;
      {
        // The clip is captured by the nsDisplayFixedPosition, so clear the
        // clip for the nsDisplayBackgroundImage inside.
        DisplayListClipState::AutoSaveRestore bgImageClip(aBuilder);
        bgImageClip.Clear();
        if (aSecondaryReferenceFrame) {
          nsDisplayBackgroundImage::InitData tableData = bgData;
          nsIFrame* styleFrame = tableData.frame;
          tableData.frame = aSecondaryReferenceFrame;
          bgItem = MakeDisplayItem<nsDisplayTableBackgroundImage>(
              aBuilder, tableData, styleFrame);
        } else {
          bgItem = MakeDisplayItem<nsDisplayBackgroundImage>(aBuilder, bgData);
        }
      }
      bgItem->SetDependentFrame(aBuilder, dependentFrame);
      if (aSecondaryReferenceFrame) {
        thisItemList.AppendToTop(
            nsDisplayTableFixedPosition::CreateForFixedBackground(
                aBuilder, aSecondaryReferenceFrame, bgItem, i, aFrame));
      } else {
        thisItemList.AppendToTop(
            nsDisplayFixedPosition::CreateForFixedBackground(aBuilder, aFrame,
                                                             bgItem, i));
      }

    } else {
      nsDisplayBackgroundImage* bgItem;
      if (aSecondaryReferenceFrame) {
        nsDisplayBackgroundImage::InitData tableData = bgData;
        nsIFrame* styleFrame = tableData.frame;
        tableData.frame = aSecondaryReferenceFrame;

        bgItem = MakeDisplayItem<nsDisplayTableBackgroundImage>(
            aBuilder, tableData, styleFrame);
      } else {
        bgItem = MakeDisplayItem<nsDisplayBackgroundImage>(aBuilder, bgData);
      }
      bgItem->SetDependentFrame(aBuilder, dependentFrame);
      thisItemList.AppendToTop(bgItem);
    }

    if (bg->mImage.mLayers[i].mBlendMode != NS_STYLE_BLEND_NORMAL) {
      DisplayListClipState::AutoSaveRestore blendClip(aBuilder);
      // asr is scrolled. Even if we wrap a fixed background layer, that's
      // fine, because the item will have a scrolled clip that limits the
      // item with respect to asr.
      if (aSecondaryReferenceFrame) {
        thisItemList.AppendToTop(MakeDisplayItem<nsDisplayTableBlendMode>(
            aBuilder, aSecondaryReferenceFrame, &thisItemList,
            bg->mImage.mLayers[i].mBlendMode, asr, i + 1, aFrame));
      } else {
        thisItemList.AppendToTop(MakeDisplayItem<nsDisplayBlendMode>(
            aBuilder, aFrame, &thisItemList, bg->mImage.mLayers[i].mBlendMode,
            asr, i + 1));
      }
    }
    bgItemList.AppendToTop(&thisItemList);
  }

  if (needBlendContainer) {
    DisplayListClipState::AutoSaveRestore blendContainerClip(aBuilder);
    if (aSecondaryReferenceFrame) {
      bgItemList.AppendToTop(
          nsDisplayTableBlendContainer::CreateForBackgroundBlendMode(
              aBuilder, aSecondaryReferenceFrame, &bgItemList, asr, aFrame));
    } else {
      bgItemList.AppendToTop(
          nsDisplayBlendContainer::CreateForBackgroundBlendMode(
              aBuilder, aFrame, &bgItemList, asr));
    }
  }

  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::CanOptimizeToImageLayer(
    LayerManager* aManager, nsDisplayListBuilder* aBuilder) {
  if (!mBackgroundStyle) {
    return false;
  }

  // We currently can't handle tiled backgrounds.
  if (!mDestRect.Contains(mFillRect)) {
    return false;
  }

  // For 'contain' and 'cover', we allow any pixel of the image to be sampled
  // because there isn't going to be any spriting/atlasing going on.
  const nsStyleImageLayers::Layer& layer =
      mBackgroundStyle->StyleBackground()->mImage.mLayers[mLayer];
  bool allowPartialImages =
      (layer.mSize.mWidthType == nsStyleImageLayers::Size::eContain ||
       layer.mSize.mWidthType == nsStyleImageLayers::Size::eCover);
  if (!allowPartialImages && !mFillRect.Contains(mDestRect)) {
    return false;
  }

  return nsDisplayImageContainer::CanOptimizeToImageLayer(aManager, aBuilder);
}

nsRect nsDisplayBackgroundImage::GetDestRect() const { return mDestRect; }

already_AddRefed<imgIContainer> nsDisplayBackgroundImage::GetImage() {
  nsCOMPtr<imgIContainer> image = mImage;
  return image.forget();
}

nsDisplayBackgroundImage::ImageLayerization
nsDisplayBackgroundImage::ShouldCreateOwnLayer(nsDisplayListBuilder* aBuilder,
                                               LayerManager* aManager) {
  if (ForceActiveLayers()) {
    return WHENEVER_POSSIBLE;
  }

  nsIFrame* backgroundStyleFrame =
      nsCSSRendering::FindBackgroundStyleFrame(StyleFrame());
  if (ActiveLayerTracker::IsBackgroundPositionAnimated(aBuilder,
                                                       backgroundStyleFrame)) {
    return WHENEVER_POSSIBLE;
  }

  if (nsLayoutUtils::AnimatedImageLayersEnabled() && mBackgroundStyle) {
    const nsStyleImageLayers::Layer& layer =
        mBackgroundStyle->StyleBackground()->mImage.mLayers[mLayer];
    const nsStyleImage* image = &layer.mImage;
    if (image->GetType() == eStyleImageType_Image) {
      imgIRequest* imgreq = image->GetImageData();
      nsCOMPtr<imgIContainer> image;
      if (imgreq && NS_SUCCEEDED(imgreq->GetImage(getter_AddRefs(image))) &&
          image) {
        bool animated = false;
        if (NS_SUCCEEDED(image->GetAnimated(&animated)) && animated) {
          return WHENEVER_POSSIBLE;
        }
      }
    }
  }

  if (nsLayoutUtils::GPUImageScalingEnabled() &&
      aManager->IsCompositingCheap()) {
    return ONLY_FOR_SCALING;
  }

  return NO_LAYER_NEEDED;
}

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

LayerState nsDisplayBackgroundImage::GetLayerState(
    nsDisplayListBuilder* aBuilder, LayerManager* aManager,
    const ContainerLayerParameters& aParameters) {
  mImageFlags = aBuilder->GetBackgroundPaintFlags();
  CheckForBorderItem(this, mImageFlags);

  ImageLayerization shouldLayerize = ShouldCreateOwnLayer(aBuilder, aManager);
  if (shouldLayerize == NO_LAYER_NEEDED) {
    // We can skip the call to CanOptimizeToImageLayer if we don't want a
    // layer anyway.
    return LAYER_NONE;
  }

  if (CanOptimizeToImageLayer(aManager, aBuilder)) {
    if (shouldLayerize == WHENEVER_POSSIBLE) {
      return LAYER_ACTIVE;
    }

    MOZ_ASSERT(shouldLayerize == ONLY_FOR_SCALING,
               "unhandled ImageLayerization value?");

    MOZ_ASSERT(mImage);
    int32_t imageWidth;
    int32_t imageHeight;
    mImage->GetWidth(&imageWidth);
    mImage->GetHeight(&imageHeight);
    NS_ASSERTION(imageWidth != 0 && imageHeight != 0, "Invalid image size!");

    int32_t appUnitsPerDevPixel = mFrame->PresContext()->AppUnitsPerDevPixel();
    LayoutDeviceRect destRect =
        LayoutDeviceRect::FromAppUnits(GetDestRect(), appUnitsPerDevPixel);

    const LayerRect destLayerRect = destRect * aParameters.Scale();

    // Calculate the scaling factor for the frame.
    const gfxSize scale = gfxSize(destLayerRect.width / imageWidth,
                                  destLayerRect.height / imageHeight);

    if ((scale.width != 1.0f || scale.height != 1.0f) &&
        (destLayerRect.width * destLayerRect.height >= 64 * 64)) {
      // Separate this image into a layer.
      // There's no point in doing this if we are not scaling at all or if the
      // target size is pretty small.
      return LAYER_ACTIVE;
    }
  }

  return LAYER_NONE;
}

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

bool nsDisplayBackgroundImage::CanBuildWebRenderDisplayItems(
    LayerManager* aManager, nsDisplayListBuilder* aDisplayListBuilder) {
  if (aDisplayListBuilder) {
    mImageFlags = aDisplayListBuilder->GetBackgroundPaintFlags();
  }

  return mBackgroundStyle->StyleBackground()->mImage.mLayers[mLayer].mClip !=
             StyleGeometryBox::Text &&
         nsCSSRendering::CanBuildWebRenderDisplayItemsForStyleImageLayer(
             aManager, *StyleFrame()->PresContext(), StyleFrame(),
             mBackgroundStyle->StyleBackground(), mLayer, mImageFlags);
}

bool nsDisplayBackgroundImage::CreateWebRenderCommands(
    mozilla::wr::DisplayListBuilder& aBuilder,
    mozilla::wr::IpcResourceUpdateQueue& aResources,
    const StackingContextHelper& aSc, RenderRootStateManager* aManager,
    nsDisplayListBuilder* aDisplayListBuilder) {
  ContainerLayerParameters parameter;
  if (!CanBuildWebRenderDisplayItems(aManager->LayerManager(),
                                     aDisplayListBuilder)) {
    return false;
  }

  CheckForBorderItem(this, mImageFlags);
  nsCSSRendering::PaintBGParams params =
      nsCSSRendering::PaintBGParams::ForSingleLayer(
          *StyleFrame()->PresContext(), GetPaintRect(), mBackgroundRect,
          StyleFrame(), mImageFlags, mLayer, CompositionOp::OP_OVER);
  params.bgClipRect = &mBounds;
  ImgDrawResult result =
      nsCSSRendering::BuildWebRenderDisplayItemsForStyleImageLayer(
          params, aBuilder, aResources, aSc, aManager, this);
  if (result == ImgDrawResult::NOT_SUPPORTED) {
    return false;
  }

  nsDisplayBackgroundGeometry::UpdateDrawResult(this, result);
  return true;
}

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) {
  if (!nsDisplayItem::ComputeVisibility(aBuilder, aVisibleRegion)) {
    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(
    const nsDisplayItem* aItem, StyleGeometryBox aClip, const nsRect& aRect,
    const nsRect& aBackgroundRect) {
  nsRegion result;
  if (aRect.IsEmpty()) return result;

  nsIFrame* frame = aItem->Frame();

  nsRect clipRect = aBackgroundRect;
  if (frame->IsCanvasFrame()) {
    nsCanvasFrame* canvasFrame = static_cast<nsCanvasFrame*>(frame);
    clipRect = canvasFrame->CanvasArea() + aItem->ToReferenceFrame();
  } else if (aClip == StyleGeometryBox::PaddingBox ||
             aClip == StyleGeometryBox::ContentBox) {
    nsMargin border = frame->GetUsedBorder();
    if (aClip == StyleGeometryBox::ContentBox) {
      border += frame->GetUsedPadding();
    }
    border.ApplySkipSides(frame->GetSkipSides());
    clipRect.Deflate(border);
  }

  return clipRect.Intersect(aRect);
}

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

  if (!mBackgroundStyle) return result;

  *aSnap = true;

  // For StyleBoxDecorationBreak::Slice, 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 (mFrame->StyleBorder()->mBoxDecorationBreak ==
          StyleBoxDecorationBreak::Clone ||
      (!mFrame->GetPrevContinuation() && !mFrame->GetNextContinuation())) {
    const nsStyleImageLayers::Layer& layer =
        mBackgroundStyle->StyleBackground()->mImage.mLayers[mLayer];
    if (layer.mImage.IsOpaque() && layer.mBlendMode == NS_STYLE_BLEND_NORMAL &&
        layer.mRepeat.mXRepeat != StyleImageLayerRepeat::Space &&
        layer.mRepeat.mYRepeat != StyleImageLayerRepeat::Space &&
        layer.mClip != StyleGeometryBox::Text) {
      result = GetInsideClipRegion(this, layer.mClip, mBounds, mBackgroundRect);
    }
  }

  return result;
}

Maybe<nscolor> nsDisplayBackgroundImage::IsUniform(
    nsDisplayListBuilder* aBuilder) const {
  if (!mBackgroundStyle) {
    return Some(NS_RGBA(0, 0, 0, 0));
  }
  return Nothing();
}

nsRect nsDisplayBackgroundImage::GetPositioningArea() const {
  if (!mBackgroundStyle) {
    return nsRect();
  }
  nsIFrame* attachedToFrame;
  bool transformedFixed;
  return nsCSSRendering::ComputeImageLayerPositioningArea(
             mFrame->PresContext(), mFrame, mBackgroundRect,
             mBackgroundStyle->StyleBackground()->mImage.mLayers[mLayer],
             &attachedToFrame, &transformedFixed) +
         ToReferenceFrame();
}

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

void nsDisplayBackgroundImage::Paint(nsDisplayListBuilder* aBuilder,
                                     gfxContext* aCtx) {
  PaintInternal(aBuilder, aCtx, GetPaintRect(), &mBounds);
}

void nsDisplayBackgroundImage::PaintInternal(nsDisplayListBuilder* aBuilder,
                                             gfxContext* aCtx,
                                             const nsRect& aBounds,
                                             nsRect* aClipRect) {
  gfxContext* ctx = aCtx;
  StyleGeometryBox clip =
      mBackgroundStyle->StyleBackground()->mImage.mLayers[mLayer].mClip;

  if (clip == StyleGeometryBox::Text) {
    if (!GenerateAndPushTextMask(StyleFrame(), aCtx, mBackgroundRect,
                                 aBuilder)) {
      return;
    }
  }

  nsCSSRendering::PaintBGParams params =
      nsCSSRendering::PaintBGParams::ForSingleLayer(
          *StyleFrame()->PresContext(), aBounds, mBackgroundRect, StyleFrame(),
          mImageFlags, mLayer, CompositionOp::OP_OVER);
  params.bgClipRect = aClipRect;
  ImgDrawResult result = nsCSSRendering::PaintStyleImageLayer(params, *aCtx);

  if (clip == StyleGeometryBox::Text) {
    ctx->PopGroupAndBlend();
  }

  nsDisplayBackgroundGeometry::UpdateDrawResult(this, result);
}

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

  auto* 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 (!mDestRect.IsEqualInterior(geometry->mDestRect)) {
    // Dest 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()) {
    const nsStyleImage& image =
        mBackgroundStyle->StyleBackground()->mImage.mLayers[mLayer].mImage;
    if (image.GetType() == eStyleImageType_Image &&
        geometry->ShouldInvalidateToSyncDecodeImages()) {
      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) const {
  *aSnap = true;
  return mBounds;
}

nsRect nsDisplayBackgroundImage::GetBoundsInternal(
    nsDisplayListBuilder* aBuilder, nsIFrame* aFrameForBounds) {
  // This allows nsDisplayTableBackgroundImage to change the frame used for
  // bounds calculation.
  nsIFrame* frame = aFrameForBounds ? aFrameForBounds : mFrame;

  nsPresContext* presContext = frame->PresContext();

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

  nsRect clipRect = mBackgroundRect;
  if (frame->IsCanvasFrame()) {
    nsCanvasFrame* canvasFrame = static_cast<nsCanvasFrame*>(frame);
    clipRect = canvasFrame->CanvasArea() + ToReferenceFrame();
  }
  const nsStyleImageLayers::Layer& layer =
      mBackgroundStyle->StyleBackground()->mImage.mLayers[mLayer];
  return nsCSSRendering::GetBackgroundLayerRect(
      presContext, frame, mBackgroundRect, clipRect, layer,
      aBuilder->GetBackgroundPaintFlags());
}

nsDisplayTableBackgroundImage::nsDisplayTableBackgroundImage(
    nsDisplayListBuilder* aBuilder, const InitData& aData, nsIFrame* aCellFrame)
    : nsDisplayBackgroundImage(aBuilder, aData, aCellFrame),
      mStyleFrame(aCellFrame),
      mTableType(GetTableTypeFromFrame(mStyleFrame)) {
  if (aBuilder->IsRetainingDisplayList()) {
    mStyleFrame->AddDisplayItem(this);
  }
}

nsDisplayTableBackgroundImage::~nsDisplayTableBackgroundImage() {
  if (mStyleFrame) {
    mStyleFrame->RemoveDisplayItem(this);
  }
}

bool nsDisplayTableBackgroundImage::IsInvalid(nsRect& aRect) const {
  bool result = mStyleFrame ? mStyleFrame->IsInvalid(aRect) : false;
  aRect += ToReferenceFrame();
  return result;
}

nsDisplayThemedBackground::nsDisplayThemedBackground(
    nsDisplayListBuilder* aBuilder, nsIFrame* aFrame,
    const nsRect& aBackgroundRect)
    : nsDisplayItem(aBuilder, aFrame), mBackgroundRect(aBackgroundRect) {
  MOZ_COUNT_CTOR(nsDisplayThemedBackground);
}

void nsDisplayThemedBackground::Init(nsDisplayListBuilder* aBuilder) {
  const nsStyleDisplay* disp = StyleFrame()->StyleDisplay();
  mAppearance = disp->mAppearance;
  StyleFrame()->IsThemed(disp, &mThemeTransparency);

  // Perform necessary RegisterThemeGeometry
  nsITheme* theme = StyleFrame()->PresContext()->GetTheme();
  nsITheme::ThemeGeometryType type =
      theme->ThemeGeometryTypeForWidget(StyleFrame(), disp->mAppearance);
  if (type != nsITheme::eThemeGeometryTypeUnknown) {
    RegisterThemeGeometry(aBuilder, this, StyleFrame(), type);
  }

  if (disp->mAppearance == StyleAppearance::MozWinBorderlessGlass ||
      disp->mAppearance == StyleAppearance::MozWinGlass) {
    aBuilder->SetGlassDisplayItem(this);
  }

  mBounds = GetBoundsInternal();
}

void nsDisplayThemedBackground::WriteDebugInfo(std::stringstream& aStream) {
  aStream << " (themed, appearance:" << (int)mAppearance << ")";
}

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

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

  if (mThemeTransparency == nsITheme::eOpaque) {
    result = mBackgroundRect;
  }
  return result;
}

Maybe<nscolor> nsDisplayThemedBackground::IsUniform(
    nsDisplayListBuilder* aBuilder) const {
  if (mAppearance == StyleAppearance::MozWinBorderlessGlass ||
      mAppearance == StyleAppearance::MozWinGlass) {
    return Some(NS_RGBA(0, 0, 0, 0));
  }
  return Nothing();
}

nsRect nsDisplayThemedBackground::GetPositioningArea() const {
  return mBackgroundRect;
}

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

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

bool nsDisplayThemedBackground::CreateWebRenderCommands(
    mozilla::wr::DisplayListBuilder& aBuilder,
    mozilla::wr::IpcResourceUpdateQueue& aResources,
    const StackingContextHelper& aSc,
    mozilla::layers::RenderRootStateManager* aManager,
    nsDisplayListBuilder* aDisplayListBuilder) {
  nsITheme* theme = StyleFrame()->PresContext()->GetTheme();
  return theme->CreateWebRenderCommandsForWidget(aBuilder, aResources, aSc,
                                                 aManager, StyleFrame(),
                                                 mAppearance, mBackgroundRect);
}

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

void nsDisplayThemedBackground::ComputeInvalidationRegion(
    nsDisplayListBuilder* aBuilder, const nsDisplayItemGeometry* aGeometry,
    nsRegion* aInvalidRegion) const {
  auto* 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 = StyleFrame()->PresContext()->GetTheme();
  if (theme->WidgetAppearanceDependsOnWindowFocus(mAppearance) &&
      IsWindowActive() != geometry->mWindowIsActive) {
    aInvalidRegion->Or(*aInvalidRegion, bounds);
  }
}

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

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

  nsRect r = mBackgroundRect - ToReferenceFrame();
  presContext->GetTheme()->GetWidgetOverflow(
      presContext->DeviceContext(), mFrame, mFrame->StyleDisplay()->mAppearance,
      &r);
  return r + ToReferenceFrame();
}

void nsDisplayImageContainer::ConfigureLayer(
    ImageLayer* aLayer, const ContainerLayerParameters& aParameters) {
  aLayer->SetSamplingFilter(nsLayoutUtils::GetSamplingFilterForFrame(mFrame));

  nsCOMPtr<imgIContainer> image = GetImage();
  MOZ_ASSERT(image);
  int32_t imageWidth;
  int32_t imageHeight;
  image->GetWidth(&imageWidth);
  image->GetHeight(&imageHeight);
  NS_ASSERTION(imageWidth != 0 && imageHeight != 0, "Invalid image size!");

  if (imageWidth > 0 && imageHeight > 0) {
    // We're actually using the ImageContainer. Let our frame know that it
    // should consider itself to have painted successfully.
    UpdateDrawResult(ImgDrawResult::SUCCESS);
  }

  // It's possible (for example, due to downscale-during-decode) that the
  // ImageContainer this ImageLayer is holding has a different size from the
  // intrinsic size of the image. For this reason we compute the transform using
  // the ImageContainer's size rather than the image's intrinsic size.
  // XXX(seth): In reality, since the size of the ImageContainer may change
  // asynchronously, this is not enough. Bug 1183378 will provide a more
  // complete fix, but this solution is safe in more cases than simply relying
  // on the intrinsic size.
  IntSize containerSize = aLayer->GetContainer()
                              ? aLayer->GetContainer()->GetCurrentSize()
                              : IntSize(imageWidth, imageHeight);

  const int32_t factor = mFrame->PresContext()->AppUnitsPerDevPixel();
  const LayoutDeviceRect destRect(
      LayoutDeviceIntRect::FromAppUnitsToNearest(GetDestRect(), factor));

  const LayoutDevicePoint p = destRect.TopLeft();
  Matrix transform = Matrix::Translation(p.x + aParameters.mOffset.x,
                                         p.y + aParameters.mOffset.y);
  transform.PreScale(destRect.width / containerSize.width,
                     destRect.height / containerSize.height);
  aLayer->SetBaseTransform(gfx::Matrix4x4::From2D(transform));
}

already_AddRefed<ImageContainer> nsDisplayImageContainer::GetContainer(
    LayerManager* aManager, nsDisplayListBuilder* aBuilder) {
  nsCOMPtr<imgIContainer> image = GetImage();
  if (!image) {
    MOZ_ASSERT_UNREACHABLE(
        "Must call CanOptimizeToImage() and get true "
        "before calling GetContainer()");
    return nullptr;
  }

  uint32_t flags = imgIContainer::FLAG_ASYNC_NOTIFY;
  if (aBuilder->ShouldSyncDecodeImages()) {
    flags |= imgIContainer::FLAG_SYNC_DECODE;
  }

  RefPtr<ImageContainer> container = image->GetImageContainer(aManager, flags);
  if (!container || !container->HasCurrentImage()) {
    return nullptr;
  }

  return container.forget();
}

bool nsDisplayImageContainer::CanOptimizeToImageLayer(
    LayerManager* aManager, nsDisplayListBuilder* aBuilder) {
  uint32_t flags = aBuilder->ShouldSyncDecodeImages()
                       ? imgIContainer::FLAG_SYNC_DECODE
                       : imgIContainer::FLAG_NONE;

  nsCOMPtr<imgIContainer> image = GetImage();
  if (!image) {
    return false;
  }

  if (!image->IsImageContainerAvailable(aManager, flags)) {
    return false;
  }

  int32_t imageWidth;
  int32_t imageHeight;
  image->GetWidth(&imageWidth);
  image->GetHeight(&imageHeight);

  if (imageWidth == 0 || imageHeight == 0) {
    NS_ASSERTION(false, "invalid image size");
    return false;
  }

  const int32_t factor = mFrame->PresContext()->AppUnitsPerDevPixel();
  const LayoutDeviceRect destRect(
      LayoutDeviceIntRect::FromAppUnitsToNearest(GetDestRect(), factor));

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

  if (scale.width < 0.34 || scale.height < 0.34) {
    // This would look awful as long as we can't use high-quality downscaling
    // for image layers (bug 803703), so don't turn this into an image layer.
    return false;
  }

  if (mFrame->IsImageFrame() || mFrame->IsImageControlFrame()) {
    // Image layer doesn't support draw focus ring for image map.
    nsImageFrame* f = static_cast<nsImageFrame*>(mFrame);
    if (f->HasImageMap()) {
      return false;
    }
  }

  return true;
}

void nsDisplayBackgroundColor::ApplyOpacity(nsDisplayListBuilder* aBuilder,
                                            float aOpacity,
                                            const DisplayItemClipChain* aClip) {
  NS_ASSERTION(CanApplyOpacity(), "ApplyOpacity should be allowed");
  mColor.a = mColor.a * aOpacity;
  IntersectClip(aBuilder, aClip, false);
}

bool nsDisplayBackgroundColor::CanApplyOpacity() const {
  // Don't apply opacity if the background color is animated since the color is
  // going to be changed on the compositor.
  return !EffectCompositor::HasAnimationsForCompositor(
      mFrame, eCSSProperty_background_color);
}

LayerState nsDisplayBackgroundColor::GetLayerState(
    nsDisplayListBuilder* aBuilder, LayerManager* aManager,
    const ContainerLayerParameters& aParameters) {
  StyleGeometryBox clip =
      mBackgroundStyle->StyleBackground()->mImage.mLayers[0].mClip;
  if (ForceActiveLayers() && clip != StyleGeometryBox::Text) {
    return LAYER_ACTIVE;
  }

  if (EffectCompositor::HasAnimationsForCompositor(
          mFrame, eCSSProperty_background_color)) {
    return LAYER_ACTIVE_FORCE;
  }

  return LAYER_NONE;
}

already_AddRefed<Layer> nsDisplayBackgroundColor::BuildLayer(
    nsDisplayListBuilder* aBuilder, LayerManager* aManager,
    const ContainerLayerParameters& aContainerParameters) {
  if (mColor == Color()) {
    return nullptr;
  }

  RefPtr<ColorLayer> layer = static_cast<ColorLayer*>(
      aManager->GetLayerBuilder()->GetLeafLayerFor(aBuilder, this));
  if (!layer) {
    layer = aManager->CreateColorLayer();
    if (!layer) return nullptr;
  }
  layer->SetColor(mColor);

  int32_t appUnitsPerDevPixel = mFrame->PresContext()->AppUnitsPerDevPixel();
  layer->SetBounds(mBackgroundRect.ToNearestPixels(appUnitsPerDevPixel));
  layer->SetBaseTransform(gfx::Matrix4x4::Translation(
      aContainerParameters.mOffset.x, aContainerParameters.mOffset.y, 0));

  nsDisplayListBuilder::AddAnimationsAndTransitionsToLayer(
      layer, aBuilder, this, mFrame, eCSSProperty_background_color);

  return layer.forget();
}

bool nsDisplayBackgroundColor::CreateWebRenderCommands(
    mozilla::wr::DisplayListBuilder& aBuilder,
    mozilla::wr::IpcResourceUpdateQueue& aResources,
    const StackingContextHelper& aSc,
    mozilla::layers::RenderRootStateManager* aManager,
    nsDisplayListBuilder* aDisplayListBuilder) {
  if (mColor == Color()) {
    return true;
  }

  StyleGeometryBox clip =
      mBackgroundStyle->StyleBackground()->mImage.mLayers[0].mClip;
  if (clip == StyleGeometryBox::Text) {
    return false;
  }

  LayoutDeviceRect bounds = LayoutDeviceRect::FromAppUnits(
      mBackgroundRect, mFrame->PresContext()->AppUnitsPerDevPixel());
  wr::LayoutRect roundedRect = wr::ToRoundedLayoutRect(bounds);

  aBuilder.PushRect(roundedRect, roundedRect, !BackfaceIsHidden(),
                    wr::ToColorF(ToDeviceColor(mColor)));

  return true;
}

void nsDisplayBackgroundColor::PaintWithClip(nsDisplayListBuilder* aBuilder,
                                             gfxContext* aCtx,
                                             const DisplayItemClip& aClip) {
  MOZ_ASSERT(mBackgroundStyle->StyleBackground()->mImage.mLayers[0].mClip !=
             StyleGeometryBox::Text);
  if (mColor == Color()) {
    return;
  }

  nsRect fillRect = mBackgroundRect;
  if (aClip.HasClip()) {
    fillRect.IntersectRect(fillRect, aClip.GetClipRect());
  }

  DrawTarget* dt = aCtx->GetDrawTarget();
  int32_t A2D = mFrame->PresContext()->AppUnitsPerDevPixel();
  Rect bounds = ToRect(nsLayoutUtils::RectToGfxRect(fillRect, A2D));
  MaybeSnapToDevicePixels(bounds, *dt);
  ColorPattern fill(ToDeviceColor(mColor));

  if (aClip.GetRoundedRectCount()) {
    MOZ_ASSERT(aClip.GetRoundedRectCount() == 1);

    AutoTArray<DisplayItemClip::RoundedRect, 1> roundedRect;
    aClip.AppendRoundedRects(&roundedRect);

    bool pushedClip = false;
    if (!fillRect.Contains(roundedRect[0].mRect)) {
      dt->PushClipRect(bounds);
      pushedClip = true;
    }

    RectCornerRadii pixelRadii;
    nsCSSRendering::ComputePixelRadii(roundedRect[0].mRadii, A2D, &pixelRadii);
    dt->FillRoundedRect(
        RoundedRect(NSRectToSnappedRect(roundedRect[0].mRect, A2D, *dt),
                    pixelRadii),
        fill);
    if (pushedClip) {
      dt->PopClip();
    }
  } else {
    dt->FillRect(bounds, fill);
  }
}

void nsDisplayBackgroundColor::Paint(nsDisplayListBuilder* aBuilder,
                                     gfxContext* aCtx) {
  if (mColor == Color()) {
    return;
  }

#if 0
  // See https://bugzilla.mozilla.org/show_bug.cgi?id=1148418#c21 for why this
  // results in a precision induced rounding issue that makes the rect one
  // pixel shorter in rare cases. Disabled in favor of the old code for now.
  // Note that the pref layout.css.devPixelsPerPx needs to be set to 1 to
  // reproduce the bug.
  //
  // TODO:
  // This new path does not include support for background-clip:text; need to
  // be fixed if/when we switch to this new code path.

  DrawTarget& aDrawTarget = *aCtx->GetDrawTarget();

  Rect rect = NSRectToSnappedRect(mBackgroundRect,
                                  mFrame->PresContext()->AppUnitsPerDevPixel(),
                                  aDrawTarget);
  ColorPattern color(ToDeviceColor(mColor));
  aDrawTarget.FillRect(rect, color);
#else
  gfxContext* ctx = aCtx;
  gfxRect bounds = nsLayoutUtils::RectToGfxRect(
      mBackgroundRect, mFrame->PresContext()->AppUnitsPerDevPixel());

  StyleGeometryBox clip =
      mBackgroundStyle->StyleBackground()->mImage.mLayers[0].mClip;
  if (clip == StyleGeometryBox::Text) {
    if (!GenerateAndPushTextMask(mFrame, aCtx, mBackgroundRect, aBuilder)) {
      return;
    }

    ctx->SetColor(mColor);
    ctx->NewPath();
    ctx->SnappedRectangle(bounds);
    ctx->Fill();
    ctx->PopGroupAndBlend();
    return;
  }

  ctx->SetColor(mColor);
  ctx->NewPath();
  ctx->SnappedRectangle(bounds);
  ctx->Fill();
#endif
}

nsRegion nsDisplayBackgroundColor::GetOpaqueRegion(
    nsDisplayListBuilder* aBuilder, bool* aSnap) const {
  *aSnap = false;

  if (mColor.a != 1) {
    return nsRegion();
  }

  if (!mBackgroundStyle) return nsRegion();

  const nsStyleImageLayers::Layer& bottomLayer =
      mBackgroundStyle->StyleBackground()->BottomLayer();
  if (bottomLayer.mClip == StyleGeometryBox::Text) {
    return nsRegion();
  }

  *aSnap = true;
  return nsDisplayBackgroundImage::GetInsideClipRegion(
      this, bottomLayer.mClip, mBackgroundRect, mBackgroundRect);
}

Maybe<nscolor> nsDisplayBackgroundColor::IsUniform(
    nsDisplayListBuilder* aBuilder) const {
  return Some(mColor.ToABGR());
}

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);
}

void nsDisplayBackgroundColor::WriteDebugInfo(std::stringstream& aStream) {
  aStream << " (rgba " << mColor.r << "," << mColor.g << "," << mColor.b << ","
          << mColor.a << ")";
  aStream << " backgroundRect" << mBackgroundRect;
}

already_AddRefed<Layer> nsDisplayClearBackground::BuildLayer(
    nsDisplayListBuilder* aBuilder, LayerManager* aManager,
    const ContainerLayerParameters& aParameters) {
  RefPtr<ColorLayer> layer = static_cast<ColorLayer*>(
      aManager->GetLayerBuilder()->GetLeafLayerFor(aBuilder, this));
  if (!layer) {
    layer = aManager->CreateColorLayer();
    if (!layer) return nullptr;
  }
  layer->SetColor(Color());
  layer->SetMixBlendMode(gfx::CompositionOp::OP_SOURCE);

  bool snap;
  nsRect bounds = GetBounds(aBuilder, &snap);
  int32_t appUnitsPerDevPixel = mFrame->PresContext()->AppUnitsPerDevPixel();
  layer->SetBounds(bounds.ToNearestPixels(appUnitsPerDevPixel));  // XXX Do we
                                                                  // need to
                                                                  // respect the
                                                                  // parent
                                                                  // layer's
                                                                  // scale here?

  return layer.forget();
}

bool nsDisplayClearBackground::CreateWebRenderCommands(
    mozilla::wr::DisplayListBuilder& aBuilder,
    mozilla::wr::IpcResourceUpdateQueue& aResources,
    const StackingContextHelper& aSc,
    mozilla::layers::RenderRootStateManager* aManager,
    nsDisplayListBuilder* aDisplayListBuilder) {
  LayoutDeviceRect bounds = LayoutDeviceRect::FromAppUnits(
      nsRect(ToReferenceFrame(), mFrame->GetSize()),
      mFrame->PresContext()->AppUnitsPerDevPixel());

  aBuilder.PushClearRect(wr::ToRoundedLayoutRect(bounds));

  return true;
}

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

void nsDisplayOutline::Paint(nsDisplayListBuilder* aBuilder, gfxContext* aCtx) {
  // TODO join outlines together
  MOZ_ASSERT(mFrame->StyleOutline()->ShouldPaintOutline(),
             "Should have not created a nsDisplayOutline!");

  nsPoint offset = ToReferenceFrame();
  nsCSSRendering::PaintOutline(
      mFrame->PresContext(), *aCtx, mFrame, GetPaintRect(),
      nsRect(offset, mFrame->GetSize()), mFrame->Style());
}

bool nsDisplayOutline::CreateWebRenderCommands(
    mozilla::wr::DisplayListBuilder& aBuilder,
    mozilla::wr::IpcResourceUpdateQueue& aResources,
    const StackingContextHelper& aSc,
    mozilla::layers::RenderRootStateManager* aManager,
    nsDisplayListBuilder* aDisplayListBuilder) {
  ContainerLayerParameters parameter;

  const auto& outlineStyle = mFrame->StyleOutline()->mOutlineStyle;
  if (outlineStyle.IsAuto() && nsLayoutUtils::IsOutlineStyleAutoEnabled()) {
    nsITheme* theme = mFrame->PresContext()->GetTheme();
    if (theme && theme->ThemeSupportsWidget(mFrame->PresContext(), mFrame,
                                            StyleAppearance::FocusOutline)) {
      return false;
    }
  }

  nsPoint offset = ToReferenceFrame();

  mozilla::Maybe<nsCSSBorderRenderer> borderRenderer =
      nsCSSRendering::CreateBorderRendererForOutline(
          mFrame->PresContext(), nullptr, mFrame, GetPaintRect(),
          nsRect(offset, mFrame->GetSize()), mFrame->Style());

  if (!borderRenderer) {
    // No border renderer means "there is no outline".
    // Paint nothing and return success.
    return true;
  }

  borderRenderer->CreateWebRenderCommands(this, aBuilder, aResources, aSc);
  return true;
}

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

  return false;
}

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);
}

bool nsDisplayEventReceiver::CreateWebRenderCommands(
    mozilla::wr::DisplayListBuilder& aBuilder,
    mozilla::wr::IpcResourceUpdateQueue& aResources,
    const StackingContextHelper& aSc,
    mozilla::layers::RenderRootStateManager* aManager,
    nsDisplayListBuilder* aDisplayListBuilder) {
  // This display item should never be getting created when building a display
  // list for WebRender consumption, so this function should never get called.
  MOZ_ASSERT(false);
  return true;
}

nsDisplayCompositorHitTestInfo::nsDisplayCompositorHitTestInfo(
    nsDisplayListBuilder* aBuilder, nsIFrame* aFrame,
    const mozilla::gfx::CompositorHitTestInfo& aHitTestFlags, uint32_t aIndex,
    const mozilla::Maybe<nsRect>& aArea)
    : nsDisplayHitTestInfoItem(aBuilder, aFrame),
      mIndex(aIndex),
      mAppUnitsPerDevPixel(mFrame->PresContext()->AppUnitsPerDevPixel()) {
  MOZ_COUNT_CTOR(nsDisplayCompositorHitTestInfo);
  // We should never even create this display item if we're not building
  // compositor hit-test info or if the computed hit info indicated the
  // frame is invisible to hit-testing
  MOZ_ASSERT(aBuilder->BuildCompositorHitTestInfo());
  MOZ_ASSERT(aHitTestFlags != CompositorHitTestInvisibleToHit);

  const nsRect& area =
      aArea.isSome() ? *aArea : aFrame->GetCompositorHitTestArea(aBuilder);

  SetHitTestInfo(area, aHitTestFlags);
  InitializeScrollTarget(aBuilder);
}

nsDisplayCompositorHitTestInfo::nsDisplayCompositorHitTestInfo(
    nsDisplayListBuilder* aBuilder, nsIFrame* aFrame,
    mozilla::UniquePtr<HitTestInfo>&& aHitTestInfo)
    : nsDisplayHitTestInfoItem(aBuilder, aFrame),
      mIndex(0),
      mAppUnitsPerDevPixel(mFrame->PresContext()->AppUnitsPerDevPixel()) {
  MOZ_COUNT_CTOR(nsDisplayCompositorHitTestInfo);
  SetHitTestInfo(std::move(aHitTestInfo));
  InitializeScrollTarget(aBuilder);
}

void nsDisplayCompositorHitTestInfo::InitializeScrollTarget(
    nsDisplayListBuilder* aBuilder) {
  if (aBuilder->GetCurrentScrollbarDirection().isSome()) {
    // In the case of scrollbar frames, we use the scrollbar's target
    // scrollframe instead of the scrollframe with which the scrollbar actually
    // moves.
    MOZ_ASSERT(HitTestFlags().contains(CompositorHitTestFlags::eScrollbar));
    mScrollTarget = mozilla::Some(aBuilder->GetCurrentScrollbarTarget());
  }
}

bool nsDisplayCompositorHitTestInfo::CreateWebRenderCommands(
    mozilla::wr::DisplayListBuilder& aBuilder,
    mozilla::wr::IpcResourceUpdateQueue& aResources,
    const StackingContextHelper& aSc,
    mozilla::layers::RenderRootStateManager* aManager,
    nsDisplayListBuilder* aDisplayListBuilder) {
  if (HitTestArea().IsEmpty()) {
    return true;
  }

  // XXX: eventually this scrollId computation and the SetHitTestInfo
  // call will get moved out into the WR display item iteration code so that
  // we don't need to do it as often, and so that we can do it for other
  // display item types as well (reducing the need for as many instances of
  // this display item).
  ScrollableLayerGuid::ViewID scrollId =
      mScrollTarget.valueOrFrom([&]() -> ScrollableLayerGuid::ViewID {
        const ActiveScrolledRoot* asr = GetActiveScrolledRoot();
        Maybe<ScrollableLayerGuid::ViewID> fixedTarget =
            aBuilder.GetContainingFixedPosScrollTarget(asr);
        if (fixedTarget) {
          return *fixedTarget;
        }
        if (asr) {
          return asr->GetViewId();
        }
        return ScrollableLayerGuid::NULL_SCROLL_ID;
      });

  // Insert a transparent rectangle with the hit-test info
  aBuilder.SetHitTestInfo(scrollId, HitTestFlags());

  const LayoutDeviceRect devRect =
      LayoutDeviceRect::FromAppUnits(HitTestArea(), mAppUnitsPerDevPixel);

  const wr::LayoutRect rect = wr::ToRoundedLayoutRect(devRect);

  aBuilder.PushRect(rect, rect, !BackfaceIsHidden(),
                    wr::ToColorF(gfx::Color()));
  aBuilder.ClearHitTestInfo();

  return true;
}

uint32_t nsDisplayCompositorHitTestInfo::GetPerFrameKey() const {
  return (mIndex << TYPE_BITS) | nsDisplayItem::GetPerFrameKey();
}

int32_t nsDisplayCompositorHitTestInfo::ZIndex() const {
  return mOverrideZIndex ? *mOverrideZIndex : nsDisplayItem::ZIndex();
}

void nsDisplayCompositorHitTestInfo::SetOverrideZIndex(int32_t aZIndex) {
  mOverrideZIndex = Some(aZIndex);
}

nsDisplayCaret::nsDisplayCaret(nsDisplayListBuilder* aBuilder,
                               nsIFrame* aCaretFrame)
    : nsDisplayItem(aBuilder, aCaretFrame),
      mCaret(aBuilder->GetCaret()),
      mBounds(aBuilder->GetCaretRect() + ToReferenceFrame()) {
  MOZ_COUNT_CTOR(nsDisplayCaret);
}

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

nsRect nsDisplayCaret::GetBounds(nsDisplayListBuilder* aBuilder,
                                 bool* aSnap) const {
  *aSnap = true;
  // The caret returns a rect in the coordinates of mFrame.
  return mBounds;
}

void nsDisplayCaret::Paint(nsDisplayListBuilder* aBuilder, gfxContext* 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(*aCtx->GetDrawTarget(), mFrame, ToReferenceFrame());
}

bool nsDisplayCaret::CreateWebRenderCommands(
    mozilla::wr::DisplayListBuilder& aBuilder,
    mozilla::wr::IpcResourceUpdateQueue& aResources,
    const StackingContextHelper& aSc,
    mozilla::layers::RenderRootStateManager* aManager,
    nsDisplayListBuilder* aDisplayListBuilder) {
  using namespace mozilla::layers;
  int32_t contentOffset;
  nsIFrame* frame = mCaret->GetFrame(&contentOffset);
  if (!frame) {
    return true;
  }
  NS_ASSERTION(frame == mFrame, "We're referring different frame");

  int32_t appUnitsPerDevPixel = frame->PresContext()->AppUnitsPerDevPixel();

  nsRect caretRect;
  nsRect hookRect;
  mCaret->ComputeCaretRects(frame, contentOffset, &caretRect, &hookRect);

  gfx::Color color = ToDeviceColor(frame->GetCaretColorAt(contentOffset));
  LayoutDeviceRect devCaretRect = LayoutDeviceRect::FromAppUnits(
      caretRect + ToReferenceFrame(), appUnitsPerDevPixel);
  LayoutDeviceRect devHookRect = LayoutDeviceRect::FromAppUnits(
      hookRect + ToReferenceFrame(), appUnitsPerDevPixel);

  wr::LayoutRect caret = wr::ToRoundedLayoutRect(devCaretRect);
  wr::LayoutRect hook = wr::ToRoundedLayoutRect(devHookRect);

  // Note, WR will pixel snap anything that is layout aligned.
  aBuilder.PushRect(caret, caret, !BackfaceIsHidden(), wr::ToColorF(color));

  if (!devHookRect.IsEmpty()) {
    aBuilder.PushRect(hook, hook, !BackfaceIsHidden(), wr::ToColorF(color));
  }
  return true;
}

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

  mBounds = CalculateBounds<nsRect>(*mFrame->StyleBorder());
}

bool nsDisplayBorder::IsInvisibleInRect(const nsRect& aRect) const {
  nsRect paddingRect = GetPaddingRect();
  const nsStyleBorder* styleBorder;
  if (paddingRect.Contains(aRect) &&
      !(styleBorder = mFrame->StyleBorder())->IsBorderImageLoaded() &&
      !nsLayoutUtils::HasNonZeroCorner(styleBorder->mBorderRadius)) {
    // aRect 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 true;
  }

  return false;
}

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

void nsDisplayBorder::ComputeInvalidationRegion(
    nsDisplayListBuilder* aBuilder, const nsDisplayItemGeometry* aGeometry,
    nsRegion* aInvalidRegion) const {
  auto* geometry = static_cast<const nsDisplayBorderGeometry*>(aGeometry);
  bool snap;

  if (!geometry->mBounds.IsEqualInterior(GetBounds(aBuilder, &snap))) {
    // 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);
  }

  if (aBuilder->ShouldSyncDecodeImages() &&
      geometry->ShouldInvalidateToSyncDecodeImages()) {
    aInvalidRegion->Or(*aInvalidRegion, GetBounds(aBuilder, &snap));
  }
}

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

bool nsDisplayBorder::CreateWebRenderCommands(
    mozilla::wr::DisplayListBuilder& aBuilder,
    mozilla::wr::IpcResourceUpdateQueue& aResources,
    const StackingContextHelper& aSc,
    mozilla::layers::RenderRootStateManager* aManager,
    nsDisplayListBuilder* aDisplayListBuilder) {
  nsRect rect = nsRect(ToReferenceFrame(), mFrame->GetSize());

  ImgDrawResult drawResult = nsCSSRendering::CreateWebRenderCommandsForBorder(
      this, mFrame, rect, aBuilder, aResources, aSc, aManager,
      aDisplayListBuilder);

  if (drawResult == ImgDrawResult::NOT_SUPPORTED) {
    return false;
  }

  nsDisplayBorderGeometry::UpdateDrawResult(this, drawResult);
  return true;
};

void nsDisplayBorder::Paint(nsDisplayListBuilder* aBuilder, gfxContext* aCtx) {
  nsPoint offset = ToReferenceFrame();

  PaintBorderFlags flags = aBuilder->ShouldSyncDecodeImages()
                               ? PaintBorderFlags::SYNC_DECODE_IMAGES
                               : PaintBorderFlags();

  ImgDrawResult result = nsCSSRendering::PaintBorder(
      mFrame->PresContext(), *aCtx, mFrame, GetPaintRect(),
      nsRect(offset, mFrame->GetSize()), mFrame->Style(), flags,
      mFrame->GetSkipSides());

  nsDisplayBorderGeometry::UpdateDrawResult(this, result);
}

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

// 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;

  for (auto iter = aRegion.RectIter(); !iter.Done(); iter.Next()) {
    const nsRect& r = iter.Get();
    if (accumulated.IsEmpty()) {
      accumulated = r;
      continue;
    }

    if (accumulated.YMost() >= r.y - accumulationMargin) {
      accumulated.UnionRect(accumulated, r);
    } else {
      aRects->AppendElement(accumulated);
      accumulated = r;
    }
  }

  // Finish the in-flight rectangle, if there is one.
  if (!accumulated.IsEmpty()) {
    aRects->AppendElement(accumulated);
  }
}

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

  AUTO_PROFILER_LABEL("nsDisplayBoxShadowOuter::Paint", GRAPHICS);

  for (uint32_t i = 0; i < rects.Length(); ++i) {
    nsCSSRendering::PaintBoxShadowOuter(presContext, *aCtx, mFrame, borderRect,
                                        rects[i], mOpacity);
  }
}

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

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

bool nsDisplayBoxShadowOuter::IsInvisibleInRect(const nsRect& aRect) const {
  nsPoint origin = ToReferenceFrame();
  nsRect frameRect(origin, mFrame->GetSize());
  if (!frameRect.Contains(aRect)) return false;

  // 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 true;

  return RoundedRectContainsRect(frameRect, twipsRadii, aRect);
}

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

  mVisibleRegion.And(*aVisibleRegion, GetPaintRect());
  return true;
}

bool nsDisplayBoxShadowOuter::CanBuildWebRenderDisplayItems() {
  nsCSSShadowArray* shadows = mFrame->StyleEffects()->mBoxShadow;
  if (!shadows) {
    return false;
  }

  bool hasBorderRadius;
  bool nativeTheme =
      nsCSSRendering::HasBoxShadowNativeTheme(mFrame, hasBorderRadius);

  // We don't support native themed things yet like box shadows around
  // input buttons.
  if (nativeTheme) {
    return false;
  }

  return true;
}

bool nsDisplayBoxShadowOuter::CreateWebRenderCommands(
    mozilla::wr::DisplayListBuilder& aBuilder,
    mozilla::wr::IpcResourceUpdateQueue& aResources,
    const StackingContextHelper& aSc,
    mozilla::layers::RenderRootStateManager* aManager,
    nsDisplayListBuilder* aDisplayListBuilder) {
  if (!CanBuildWebRenderDisplayItems()) {
    return false;
  }

  int32_t appUnitsPerDevPixel = mFrame->PresContext()->AppUnitsPerDevPixel();
  nsPoint offset = ToReferenceFrame();
  nsRect borderRect = mFrame->VisualBorderRectRelativeToSelf() + offset;
  AutoTArray<nsRect, 10> rects;
  bool snap;
  nsRect bounds = GetBounds(aDisplayListBuilder, &snap);
  ComputeDisjointRectangles(bounds, &rects);

  bool hasBorderRadius;
  bool nativeTheme =
      nsCSSRendering::HasBoxShadowNativeTheme(mFrame, hasBorderRadius);

  // Don't need the full size of the shadow rect like we do in
  // nsCSSRendering since WR takes care of calculations for blur
  // and spread radius.
  nsRect frameRect =
      nsCSSRendering::GetShadowRect(borderRect, nativeTheme, mFrame);

  RectCornerRadii borderRadii;
  if (hasBorderRadius) {
    hasBorderRadius = nsCSSRendering::GetBorderRadii(frameRect, borderRect,
                                                     mFrame, borderRadii);
  }

  // Everything here is in app units, change to device units.
  for (uint32_t i = 0; i < rects.Length(); ++i) {
    LayoutDeviceRect clipRect =
        LayoutDeviceRect::FromAppUnits(rects[i], appUnitsPerDevPixel);
    nsCSSShadowArray* shadows = mFrame->StyleEffects()->mBoxShadow;
    MOZ_ASSERT(shadows);

    for (uint32_t j = shadows->Length(); j > 0; j--) {
      nsCSSShadowItem* shadow = shadows->ShadowAt(j - 1);
      if (shadow->mInset) {
        continue;
      }

      float blurRadius = float(shadow->mRadius) / float(appUnitsPerDevPixel);
      gfx::Color shadowColor =
          nsCSSRendering::GetShadowColor(shadow, mFrame, mOpacity);

      // We don't move the shadow rect here since WR does it for us
      // Now translate everything to device pixels.
      const nsRect& shadowRect = frameRect;
      LayoutDevicePoint shadowOffset = LayoutDevicePoint::FromAppUnits(
          nsPoint(shadow->mXOffset, shadow->mYOffset), appUnitsPerDevPixel);

      LayoutDeviceRect deviceBox =
          LayoutDeviceRect::FromAppUnits(shadowRect, appUnitsPerDevPixel);
      wr::LayoutRect deviceBoxRect = wr::ToRoundedLayoutRect(deviceBox);
      wr::LayoutRect deviceClipRect = wr::ToRoundedLayoutRect(clipRect);

      LayoutDeviceSize zeroSize;
      wr::BorderRadius borderRadius =
          wr::ToBorderRadius(zeroSize, zeroSize, zeroSize, zeroSize);
      if (hasBorderRadius) {
        borderRadius = wr::ToBorderRadius(
            LayoutDeviceSize::FromUnknownSize(borderRadii.TopLeft()),
            LayoutDeviceSize::FromUnknownSize(borderRadii.TopRight()),
            LayoutDeviceSize::FromUnknownSize(borderRadii.BottomLeft()),
            LayoutDeviceSize::FromUnknownSize(borderRadii.BottomRight()));
      }

      float spreadRadius = float(shadow->mSpread) / float(appUnitsPerDevPixel);

      aBuilder.PushBoxShadow(deviceBoxRect, deviceClipRect, !BackfaceIsHidden(),
                             deviceBoxRect, wr::ToLayoutVector2D(shadowOffset),
                             wr::ToColorF(shadowColor), blurRadius,
                             spreadRadius, borderRadius,
                             wr::BoxShadowClipMode::Outset);
    }
  }

  return true;
}

void nsDisplayBoxShadowOuter::ComputeInvalidationRegion(
    nsDisplayListBuilder* aBuilder, const nsDisplayItemGeometry* aGeometry,
    nsRegion* aInvalidRegion) const {
  auto* geometry =
      static_cast<const nsDisplayBoxShadowOuterGeometry*>(aGeometry);
  bool snap;
  if (!geometry->mBounds.IsEqualInterior(GetBounds(aBuilder, &snap)) ||
      !geometry->mBorderRect.IsEqualInterior(GetBorderRect()) ||
      mOpacity != geometry->mOpacity) {
    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.Sub(geometry->mBounds, geometry->mBorderRect);
      newShadow.Sub(GetBounds(aBuilder, &snap), GetBorderRect());
    }
    aInvalidRegion->Or(oldShadow, newShadow);
  }
}

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

  AUTO_PROFILER_LABEL("nsDisplayBoxShadowInner::Paint", GRAPHICS);

  DrawTarget* drawTarget = aCtx->GetDrawTarget();
  gfxContext* gfx = aCtx;
  int32_t appUnitsPerDevPixel = mFrame->PresContext()->AppUnitsPerDevPixel();

  for (uint32_t i = 0; i < rects.Length(); ++i) {
    gfx->Save();
    gfx->Clip(NSRectToSnappedRect(rects[i], appUnitsPerDevPixel, *drawTarget));
    nsCSSRendering::PaintBoxShadowInner(presContext, *aCtx, mFrame, borderRect);
    gfx->Restore();
  }
}

bool nsDisplayBoxShadowInner::CanCreateWebRenderCommands(
    nsDisplayListBuilder* aBuilder, nsIFrame* aFrame,
    const nsPoint& aReferenceOffset) {
  nsCSSShadowArray* shadows = aFrame->StyleEffects()->mBoxShadow;
  if (!shadows) {
    // Means we don't have to paint anything
    return true;
  }

  bool hasBorderRadius;
  bool nativeTheme =
      nsCSSRendering::HasBoxShadowNativeTheme(aFrame, hasBorderRadius);

  // We don't support native themed things yet like box shadows around
  // input buttons.
  if (nativeTheme) {
    return false;
  }

  return true;
}

/* static */ void
nsDisplayBoxShadowInner::CreateInsetBoxShadowWebRenderCommands(
    mozilla::wr::DisplayListBuilder& aBuilder, const StackingContextHelper& aSc,
    nsRegion& aVisibleRegion, nsIFrame* aFrame, const nsRect& aBorderRect) {
  if (!nsCSSRendering::ShouldPaintBoxShadowInner(aFrame)) {
    return;
  }

  int32_t appUnitsPerDevPixel = aFrame->PresContext()->AppUnitsPerDevPixel();

  AutoTArray<nsRect, 10> rects;
  ComputeDisjointRectangles(aVisibleRegion, &rects);

  nsCSSShadowArray* shadows = aFrame->StyleEffects()->mBoxShadow;

  for (uint32_t i = 0; i < rects.Length(); ++i) {
    LayoutDeviceRect clipRect =
        LayoutDeviceRect::FromAppUnits(rects[i], appUnitsPerDevPixel);

    for (uint32_t i = shadows->Length(); i > 0; --i) {
      nsCSSShadowItem* shadowItem = shadows->ShadowAt(i - 1);
      if (!shadowItem->mInset) {
        continue;
      }

      nsRect shadowRect =
          nsCSSRendering::GetBoxShadowInnerPaddingRect(aFrame, aBorderRect);
      RectCornerRadii innerRadii;
      nsCSSRendering::GetShadowInnerRadii(aFrame, aBorderRect, innerRadii);

      // Now translate everything to device pixels.
      LayoutDeviceRect deviceBoxRect =
          LayoutDeviceRect::FromAppUnits(shadowRect, appUnitsPerDevPixel);
      wr::LayoutRect deviceClipRect = wr::ToRoundedLayoutRect(clipRect);
      Color shadowColor =
          nsCSSRendering::GetShadowColor(shadowItem, aFrame, 1.0);

      LayoutDevicePoint shadowOffset = LayoutDevicePoint::FromAppUnits(
          nsPoint(shadowItem->mXOffset, shadowItem->mYOffset),
          appUnitsPerDevPixel);

      float blurRadius =
          float(shadowItem->mRadius) / float(appUnitsPerDevPixel);

      wr::BorderRadius borderRadius = wr::ToBorderRadius(
          LayoutDeviceSize::FromUnknownSize(innerRadii.TopLeft()),
          LayoutDeviceSize::FromUnknownSize(innerRadii.TopRight()),
          LayoutDeviceSize::FromUnknownSize(innerRadii.BottomLeft()),
          LayoutDeviceSize::FromUnknownSize(innerRadii.BottomRight()));
      // NOTE: Any spread radius > 0 will render nothing. WR Bug.
      float spreadRadius =
          float(shadowItem->mSpread) / float(appUnitsPerDevPixel);

      aBuilder.PushBoxShadow(
          wr::ToLayoutRect(deviceBoxRect), deviceClipRect,
          !aFrame->BackfaceIsHidden(), wr::ToLayoutRect(deviceBoxRect),
          wr::ToLayoutVector2D(shadowOffset), wr::ToColorF(shadowColor),
          blurRadius, spreadRadius, borderRadius, wr::BoxShadowClipMode::Inset);
    }
  }
}

bool nsDisplayBoxShadowInner::CreateWebRenderCommands(
    mozilla::wr::DisplayListBuilder& aBuilder,
    mozilla::wr::IpcResourceUpdateQueue& aResources,
    const StackingContextHelper& aSc,
    mozilla::layers::RenderRootStateManager* aManager,
    nsDisplayListBuilder* aDisplayListBuilder) {
  if (!CanCreateWebRenderCommands(aDisplayListBuilder, mFrame,
                                  ToReferenceFrame())) {
    return false;
  }

  bool snap;
  nsRegion visible = GetBounds(aDisplayListBuilder, &snap);
  nsPoint offset = ToReferenceFrame();
  nsRect borderRect = nsRect(offset, mFrame->GetSize());
  nsDisplayBoxShadowInner::CreateInsetBoxShadowWebRenderCommands(
      aBuilder, aSc, visible, mFrame, borderRect);

  return true;
}

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

  mVisibleRegion.And(*aVisibleRegion, GetPaintRect());
  return true;
}

nsDisplayWrapList::nsDisplayWrapList(nsDisplayListBuilder* aBuilder,
                                     nsIFrame* aFrame, nsDisplayList* aList,
                                     bool aAnonymous)
    : nsDisplayWrapList(aBuilder, aFrame, aList,
                        aBuilder->CurrentActiveScrolledRoot(), false, 0,
                        aAnonymous) {}

nsDisplayWrapList::nsDisplayWrapList(
    nsDisplayListBuilder* aBuilder, nsIFrame* aFrame, nsDisplayList* aList,
    const ActiveScrolledRoot* aActiveScrolledRoot, bool aClearClipChain,
    uint32_t aIndex, bool aAnonymous)
    : nsDisplayHitTestInfoItem(aBuilder, aFrame, aActiveScrolledRoot,
                               aAnonymous),
      mFrameActiveScrolledRoot(aBuilder->CurrentActiveScrolledRoot()),
      mOverrideZIndex(0),
      mIndex(aIndex),
      mHasZIndexOverride(false),
      mClearingClipChain(aClearClipChain) {
  MOZ_COUNT_CTOR(nsDisplayWrapList);

  mBaseBuildingRect = GetBuildingRect();

  mListPtr = &mList;
  mListPtr->AppendToTop(aList);
  nsDisplayWrapList::UpdateBounds(aBuilder);

  if (!aFrame || !aFrame->IsTransformed()) {
    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