The Tor Browser: layout/base/nsDisplayList.cpp@b8a032363ba2 (annotated)

layout/base/nsDisplayList.cpp@b8a032363ba2 (annotated)

layout/base/nsDisplayList.cpp

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
  * vim: set ts=2 sw=2 et tw=78:
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
  */
 /*
  * structures that represent things to be painted (ordered in z-order),
  * used during painting and hit testing
  */
 #include "mozilla/dom/TabChild.h"
 #include "mozilla/layers/PLayerTransaction.h"
 #include "nsDisplayList.h"
 #include "nsCSSRendering.h"
 #include "nsRenderingContext.h"
 #include "nsISelectionController.h"
 #include "nsIPresShell.h"
 #include "nsRegion.h"
 #include "nsStyleStructInlines.h"
 #include "nsStyleTransformMatrix.h"
 #include "gfxMatrix.h"
 #include "nsSVGIntegrationUtils.h"
 #include "nsLayoutUtils.h"
 #include "nsIScrollableFrame.h"
 #include "nsIFrameInlines.h"
 #include "nsThemeConstants.h"
 #include "LayerTreeInvalidation.h"
 #include "imgIContainer.h"
 #include "BasicLayers.h"
 #include "nsBoxFrame.h"
 #include "nsViewportFrame.h"
 #include "nsSubDocumentFrame.h"
 #include "nsSVGEffects.h"
 #include "nsSVGElement.h"
 #include "nsSVGClipPathFrame.h"
 #include "GeckoProfiler.h"
 #include "nsAnimationManager.h"
 #include "nsTransitionManager.h"
 #include "nsViewManager.h"
 #include "ImageLayers.h"
 #include "ImageContainer.h"
 #include "nsCanvasFrame.h"
 #include "StickyScrollContainer.h"
 #include "mozilla/EventStates.h"
 #include "mozilla/LookAndFeel.h"
 #include "mozilla/Preferences.h"
 #include "ActiveLayerTracker.h"
 #include "nsContentUtils.h"
 #include "nsPrintfCString.h"
 #include "UnitTransforms.h"
 #include <stdint.h>
 #include <algorithm>
 using namespace mozilla;
 using namespace mozilla::css;
 using namespace mozilla::layers;
 using namespace mozilla::dom;
 typedef FrameMetrics::ViewID ViewID;
 static inline nsIFrame*
 GetTransformRootFrame(nsIFrame* aFrame)
 {
   return nsLayoutUtils::GetTransformRootFrame(aFrame);
 }
 static void AddTransformFunctions(nsCSSValueList* aList,
                                   nsStyleContext* aContext,
                                   nsPresContext* aPresContext,
                                   nsRect& aBounds,
                                   float aAppUnitsPerPixel,
                                   InfallibleTArray<TransformFunction>& aFunctions)
 {
   if (aList->mValue.GetUnit() == eCSSUnit_None) {
     return;
   }
   for (const nsCSSValueList* curr = aList; curr; curr = curr->mNext) {
     const nsCSSValue& currElem = curr->mValue;
     NS_ASSERTION(currElem.GetUnit() == eCSSUnit_Function,
                  "Stream should consist solely of functions!");
     nsCSSValue::Array* array = currElem.GetArrayValue();
     bool canStoreInRuleTree = true;
     switch (nsStyleTransformMatrix::TransformFunctionOf(array)) {
       case eCSSKeyword_rotatex:
       {
         double theta = array->Item(1).GetAngleValueInRadians();
         aFunctions.AppendElement(RotationX(theta));
         break;
       }
       case eCSSKeyword_rotatey:
       {
         double theta = array->Item(1).GetAngleValueInRadians();
         aFunctions.AppendElement(RotationY(theta));
         break;
       }
       case eCSSKeyword_rotatez:
       {
         double theta = array->Item(1).GetAngleValueInRadians();
         aFunctions.AppendElement(RotationZ(theta));
         break;
       }
       case eCSSKeyword_rotate:
       {
         double theta = array->Item(1).GetAngleValueInRadians();
         aFunctions.AppendElement(Rotation(theta));
         break;
       }
       case eCSSKeyword_rotate3d:
       {
         double x = array->Item(1).GetFloatValue();
         double y = array->Item(2).GetFloatValue();
         double z = array->Item(3).GetFloatValue();
         double theta = array->Item(4).GetAngleValueInRadians();
         aFunctions.AppendElement(Rotation3D(x, y, z, theta));
         break;
       }
       case eCSSKeyword_scalex:
       {
         double x = array->Item(1).GetFloatValue();
         aFunctions.AppendElement(Scale(x, 1, 1));
         break;
       }
       case eCSSKeyword_scaley:
       {
         double y = array->Item(1).GetFloatValue();
         aFunctions.AppendElement(Scale(1, y, 1));
         break;
       }
       case eCSSKeyword_scalez:
       {
         double z = array->Item(1).GetFloatValue();
         aFunctions.AppendElement(Scale(1, 1, z));
         break;
       }
       case eCSSKeyword_scale:
       {
         double x = array->Item(1).GetFloatValue();
         // scale(x) is shorthand for scale(x, x);
         double y = array->Count() == 2 ? x : array->Item(2).GetFloatValue();
         aFunctions.AppendElement(Scale(x, y, 1));
         break;
       }
       case eCSSKeyword_scale3d:
       {
         double x = array->Item(1).GetFloatValue();
         double y = array->Item(2).GetFloatValue();
         double z = array->Item(3).GetFloatValue();
         aFunctions.AppendElement(Scale(x, y, z));
         break;
       }
       case eCSSKeyword_translatex:
       {
         double x = nsStyleTransformMatrix::ProcessTranslatePart(
           array->Item(1), aContext, aPresContext, canStoreInRuleTree,
           aBounds.Width(), aAppUnitsPerPixel);
         aFunctions.AppendElement(Translation(x, 0, 0));
         break;
       }
       case eCSSKeyword_translatey:
       {
         double y = nsStyleTransformMatrix::ProcessTranslatePart(
           array->Item(1), aContext, aPresContext, canStoreInRuleTree,
           aBounds.Height(), aAppUnitsPerPixel);
         aFunctions.AppendElement(Translation(0, y, 0));
         break;
       }
       case eCSSKeyword_translatez:
       {
         double z = nsStyleTransformMatrix::ProcessTranslatePart(
           array->Item(1), aContext, aPresContext, canStoreInRuleTree,
 , aAppUnitsPerPixel);
         aFunctions.AppendElement(Translation(0, 0, z));
         break;
       }
       case eCSSKeyword_translate:
       {
         double x = nsStyleTransformMatrix::ProcessTranslatePart(
           array->Item(1), aContext, aPresContext, canStoreInRuleTree,
           aBounds.Width(), aAppUnitsPerPixel);
         // translate(x) is shorthand for translate(x, 0)
         double y = 0;
         if (array->Count() == 3) {
            y = nsStyleTransformMatrix::ProcessTranslatePart(
             array->Item(2), aContext, aPresContext, canStoreInRuleTree,
             aBounds.Height(), aAppUnitsPerPixel);
         }
         aFunctions.AppendElement(Translation(x, y, 0));
         break;
       }
       case eCSSKeyword_translate3d:
       {
         double x = nsStyleTransformMatrix::ProcessTranslatePart(
           array->Item(1), aContext, aPresContext, canStoreInRuleTree,
           aBounds.Width(), aAppUnitsPerPixel);
         double y = nsStyleTransformMatrix::ProcessTranslatePart(
           array->Item(2), aContext, aPresContext, canStoreInRuleTree,
           aBounds.Height(), aAppUnitsPerPixel);
         double z = nsStyleTransformMatrix::ProcessTranslatePart(
           array->Item(3), aContext, aPresContext, canStoreInRuleTree,
 , aAppUnitsPerPixel);
         aFunctions.AppendElement(Translation(x, y, z));
         break;
       }
       case eCSSKeyword_skewx:
       {
         double x = array->Item(1).GetAngleValueInRadians();
         aFunctions.AppendElement(SkewX(x));
         break;
       }
       case eCSSKeyword_skewy:
       {
         double y = array->Item(1).GetAngleValueInRadians();
         aFunctions.AppendElement(SkewY(y));
         break;
       }
       case eCSSKeyword_skew:
       {
         double x = array->Item(1).GetAngleValueInRadians();
         // skew(x) is shorthand for skew(x, 0)
         double y = 0;
         if (array->Count() == 3) {
           y = array->Item(2).GetAngleValueInRadians();
         }
         aFunctions.AppendElement(Skew(x, y));
         break;
       }
       case eCSSKeyword_matrix:
       {
         gfx::Matrix4x4 matrix;
         matrix._11 = array->Item(1).GetFloatValue();
         matrix._12 = array->Item(2).GetFloatValue();
         matrix._13 = 0;
         matrix._14 = 0;
         matrix._21 = array->Item(3).GetFloatValue();
         matrix._22 = array->Item(4).GetFloatValue();
         matrix._23 = 0;
         matrix._24 = 0;
         matrix._31 = 0;
         matrix._32 = 0;
         matrix._33 = 1;
         matrix._34 = 0;
         matrix._41 = array->Item(5).GetFloatValue();
         matrix._42 = array->Item(6).GetFloatValue();
         matrix._43 = 0;
         matrix._44 = 1;
         aFunctions.AppendElement(TransformMatrix(matrix));
         break;
       }
       case eCSSKeyword_matrix3d:
       {
         gfx::Matrix4x4 matrix;
         matrix._11 = array->Item(1).GetFloatValue();
         matrix._12 = array->Item(2).GetFloatValue();
         matrix._13 = array->Item(3).GetFloatValue();
         matrix._14 = array->Item(4).GetFloatValue();
         matrix._21 = array->Item(5).GetFloatValue();
         matrix._22 = array->Item(6).GetFloatValue();
         matrix._23 = array->Item(7).GetFloatValue();
         matrix._24 = array->Item(8).GetFloatValue();
         matrix._31 = array->Item(9).GetFloatValue();
         matrix._32 = array->Item(10).GetFloatValue();
         matrix._33 = array->Item(11).GetFloatValue();
         matrix._34 = array->Item(12).GetFloatValue();
         matrix._41 = array->Item(13).GetFloatValue();
         matrix._42 = array->Item(14).GetFloatValue();
         matrix._43 = array->Item(15).GetFloatValue();
         matrix._44 = array->Item(16).GetFloatValue();
         aFunctions.AppendElement(TransformMatrix(matrix));
         break;
       }
       case eCSSKeyword_interpolatematrix:
       {
         gfx3DMatrix matrix;
         nsStyleTransformMatrix::ProcessInterpolateMatrix(matrix, array,
                                                          aContext,
                                                          aPresContext,
                                                          canStoreInRuleTree,
                                                          aBounds,
                                                          aAppUnitsPerPixel);
         gfx::Matrix4x4 transform;
         gfx::ToMatrix4x4(matrix, transform);
         aFunctions.AppendElement(TransformMatrix(transform));
         break;
       }
       case eCSSKeyword_perspective:
       {
         aFunctions.AppendElement(Perspective(array->Item(1).GetFloatValue()));
         break;
       }
       default:
         NS_ERROR("Function not handled yet!");
     }
   }
 }
 static TimingFunction
 ToTimingFunction(css::ComputedTimingFunction& aCTF)
 {
   if (aCTF.GetType() == nsTimingFunction::Function) {
     const nsSMILKeySpline* spline = aCTF.GetFunction();
     return TimingFunction(CubicBezierFunction(spline->X1(), spline->Y1(),
                                               spline->X2(), spline->Y2()));
   }
   uint32_t type = aCTF.GetType() == nsTimingFunction::StepStart ? 1 : 2;
   return TimingFunction(StepFunction(aCTF.GetSteps(), type));
 }
 static void
 AddAnimationForProperty(nsIFrame* aFrame, nsCSSProperty aProperty,
                         mozilla::StyleAnimation* ea, Layer* aLayer,
                         AnimationData& aData, bool aPending)
 {
   NS_ASSERTION(aLayer->AsContainerLayer(), "Should only animate ContainerLayer");
   nsStyleContext* styleContext = aFrame->StyleContext();
   nsPresContext* presContext = aFrame->PresContext();
   nsRect bounds = nsDisplayTransform::GetFrameBoundsForTransform(aFrame);
   // all data passed directly to the compositor should be in css pixels
   float scale = nsDeviceContext::AppUnitsPerCSSPixel();
   mozilla::layers::Animation* animation =
     aPending ?
     aLayer->AddAnimationForNextTransaction() :
     aLayer->AddAnimation();
   animation->startTime() = ea->mStartTime + ea->mDelay;
   animation->duration() = ea->mIterationDuration;
   animation->numIterations() =
     ea->mIterationCount != NS_IEEEPositiveInfinity() ? ea->mIterationCount : -1;
   animation->direction() = ea->mDirection;
   animation->property() = aProperty;
   animation->data() = aData;
   for (uint32_t propIdx = 0; propIdx < ea->mProperties.Length(); propIdx++) {
     AnimationProperty* property = &ea->mProperties[propIdx];
     if (aProperty != property->mProperty) {
       continue;
     }
     for (uint32_t segIdx = 0; segIdx < property->mSegments.Length(); segIdx++) {
       AnimationPropertySegment* segment = &property->mSegments[segIdx];
       AnimationSegment* animSegment = animation->segments().AppendElement();
       if (aProperty == eCSSProperty_transform) {
         animSegment->startState() = InfallibleTArray<TransformFunction>();
         animSegment->endState() = InfallibleTArray<TransformFunction>();
         nsCSSValueSharedList* list = segment->mFromValue.GetCSSValueSharedListValue();
         AddTransformFunctions(list->mHead, styleContext, presContext, bounds, scale,
                               animSegment->startState().get_ArrayOfTransformFunction());
         list = segment->mToValue.GetCSSValueSharedListValue();
         AddTransformFunctions(list->mHead, styleContext, presContext, bounds, scale,
                               animSegment->endState().get_ArrayOfTransformFunction());
       } else if (aProperty == eCSSProperty_opacity) {
         animSegment->startState() = segment->mFromValue.GetFloatValue();
         animSegment->endState() = segment->mToValue.GetFloatValue();
       }
       animSegment->startPortion() = segment->mFromKey;
       animSegment->endPortion() = segment->mToKey;
       animSegment->sampleFn() = ToTimingFunction(segment->mTimingFunction);
     }
   }
 }
 template<class T>
 static void
 AddAnimationsForProperty(nsIFrame* aFrame, nsCSSProperty aProperty,
                          nsTArray<T>& aAnimations,
                          Layer* aLayer, AnimationData& aData,
                          bool aPending) {
   mozilla::TimeStamp currentTime =
     aFrame->PresContext()->RefreshDriver()->MostRecentRefresh();
   for (uint32_t animIdx = 0; animIdx < aAnimations.Length(); animIdx++) {
     mozilla::StyleAnimation* anim = &aAnimations[animIdx];
     if (!(anim->HasAnimationOfProperty(aProperty) &&
           anim->IsRunningAt(currentTime))) {
       continue;
     }
     AddAnimationForProperty(aFrame, aProperty, anim, aLayer, aData, aPending);
     anim->mIsRunningOnCompositor = true;
   }
 }
 /* static */ void
 nsDisplayListBuilder::AddAnimationsAndTransitionsToLayer(Layer* aLayer,
                                                          nsDisplayListBuilder* aBuilder,
                                                          nsDisplayItem* aItem,
                                                          nsIFrame* aFrame,
                                                          nsCSSProperty aProperty)
 {
   // This function can be called in two ways:  from
   // nsDisplay*::BuildLayer while constructing a layer (with all
   // pointers non-null), or from RestyleManager's handling of
   // UpdateOpacityLayer/UpdateTransformLayer hints.
   MOZ_ASSERT(!aBuilder == !aItem,
              "should only be called in two configurations, with both "
              "aBuilder and aItem, or with neither");
   MOZ_ASSERT(!aItem || aFrame == aItem->Frame(), "frame mismatch");
   bool pending = !aBuilder;
   if (pending) {
     aLayer->ClearAnimationsForNextTransaction();
   } else {
     aLayer->ClearAnimations();
   }
   nsIContent* content = aFrame->GetContent();
   if (!content) {
     return;
   }
   ElementTransitions* et =
     nsTransitionManager::GetTransitionsForCompositor(content, aProperty);
   ElementAnimations* ea =
     nsAnimationManager::GetAnimationsForCompositor(content, aProperty);
   if (!ea && !et) {
     return;
   }
   // If the frame is not prerendered, bail out.
   // Do this check only during layer construction; during updating the
   // caller is required to check it appropriately.
   if (aItem && !aItem->CanUseAsyncAnimations(aBuilder)) {
     // AnimationManager or TransitionManager need to know that we refused to
     // run this animation asynchronously so that they will not throttle the
     // main thread animation.
     aFrame->Properties().Set(nsIFrame::RefusedAsyncAnimation(),
                             reinterpret_cast<void*>(intptr_t(true)));
     // We need to schedule another refresh driver run so that AnimationManager
     // or TransitionManager get a chance to unthrottle the animation.
     aFrame->SchedulePaint();
     return;
   }
   AnimationData data;
   if (aProperty == eCSSProperty_transform) {
     nsRect bounds = nsDisplayTransform::GetFrameBoundsForTransform(aFrame);
     // all data passed directly to the compositor should be in css pixels
     float scale = nsDeviceContext::AppUnitsPerCSSPixel();
     gfxPoint3D offsetToTransformOrigin =
       nsDisplayTransform::GetDeltaToTransformOrigin(aFrame, scale, &bounds);
     gfxPoint3D offsetToPerspectiveOrigin =
       nsDisplayTransform::GetDeltaToPerspectiveOrigin(aFrame, scale);
     nscoord perspective = 0.0;
     nsStyleContext* parentStyleContext = aFrame->StyleContext()->GetParent();
     if (parentStyleContext) {
       const nsStyleDisplay* disp = parentStyleContext->StyleDisplay();
       if (disp && disp->mChildPerspective.GetUnit() == eStyleUnit_Coord) {
         perspective = disp->mChildPerspective.GetCoordValue();
       }
     }
     nsPoint origin;
     if (aItem) {
       origin = aItem->ToReferenceFrame();
     } else {
       // transform display items used a reference frame computed from
       // their GetTransformRootFrame().
       nsIFrame* referenceFrame =
         nsLayoutUtils::GetReferenceFrame(GetTransformRootFrame(aFrame));
       origin = aFrame->GetOffsetToCrossDoc(referenceFrame);
     }
     data = TransformData(origin, offsetToTransformOrigin,
                          offsetToPerspectiveOrigin, bounds, perspective,
                          aFrame->PresContext()->AppUnitsPerDevPixel());
   } else if (aProperty == eCSSProperty_opacity) {
     data = null_t();
   }
   if (et) {
     AddAnimationsForProperty(aFrame, aProperty, et->mPropertyTransitions,
                              aLayer, data, pending);
     aLayer->SetAnimationGeneration(et->mAnimationGeneration);
   }
   if (ea) {
     AddAnimationsForProperty(aFrame, aProperty, ea->mAnimations,
                              aLayer, data, pending);
     aLayer->SetAnimationGeneration(ea->mAnimationGeneration);
   }
 }
 nsDisplayListBuilder::nsDisplayListBuilder(nsIFrame* aReferenceFrame,
     Mode aMode, bool aBuildCaret)
     : mReferenceFrame(aReferenceFrame),
       mIgnoreScrollFrame(nullptr),
       mLayerEventRegions(nullptr),
       mCurrentTableItem(nullptr),
       mFinalTransparentRegion(nullptr),
       mCachedOffsetFrame(aReferenceFrame),
       mCachedReferenceFrame(aReferenceFrame),
       mCachedOffset(0, 0),
       mGlassDisplayItem(nullptr),
       mMode(aMode),
       mCurrentScrollParentId(FrameMetrics::NULL_SCROLL_ID),
       mBuildCaret(aBuildCaret),
       mIgnoreSuppression(false),
       mHadToIgnoreSuppression(false),
       mIsAtRootOfPseudoStackingContext(false),
       mIncludeAllOutOfFlows(false),
       mDescendIntoSubdocuments(true),
       mSelectedFramesOnly(false),
       mAccurateVisibleRegions(false),
       mAllowMergingAndFlattening(true),
       mWillComputePluginGeometry(false),
       mInTransform(false),
       mInFixedPos(false),
       mSyncDecodeImages(false),
       mIsPaintingToWindow(false),
       mIsCompositingCheap(false),
       mContainsPluginItem(false),
       mContainsBlendMode(false),
       mAncestorHasTouchEventHandler(false),
       mHaveScrollableDisplayPort(false)
 {
   MOZ_COUNT_CTOR(nsDisplayListBuilder);
   PL_InitArenaPool(&mPool, "displayListArena", 1024,
                    std::max(NS_ALIGNMENT_OF(void*),NS_ALIGNMENT_OF(double))-1);
   nsPresContext* pc = aReferenceFrame->PresContext();
   nsIPresShell *shell = pc->PresShell();
   if (pc->IsRenderingOnlySelection()) {
     nsCOMPtr<nsISelectionController> selcon(do_QueryInterface(shell));
     if (selcon) {
       selcon->GetSelection(nsISelectionController::SELECTION_NORMAL,
                            getter_AddRefs(mBoundingSelection));
     }
   }
   nsCSSRendering::BeginFrameTreesLocked();
   PR_STATIC_ASSERT(nsDisplayItem::TYPE_MAX < (1 << nsDisplayItem::TYPE_BITS));
 }
 static void MarkFrameForDisplay(nsIFrame* aFrame, nsIFrame* aStopAtFrame) {
   for (nsIFrame* f = aFrame; f;
        f = nsLayoutUtils::GetParentOrPlaceholderFor(f)) {
     if (f->GetStateBits() & NS_FRAME_FORCE_DISPLAY_LIST_DESCEND_INTO)
       return;
     f->AddStateBits(NS_FRAME_FORCE_DISPLAY_LIST_DESCEND_INTO);
     if (f == aStopAtFrame) {
       // we've reached a frame that we know will be painted, so we can stop.
       break;
     }
   }
 }
 void nsDisplayListBuilder::MarkOutOfFlowFrameForDisplay(nsIFrame* aDirtyFrame,
                                                         nsIFrame* aFrame,
                                                         const nsRect& aDirtyRect)
 {
   nsRect dirtyRectRelativeToDirtyFrame = aDirtyRect;
   if (nsLayoutUtils::IsFixedPosFrameInDisplayPort(aFrame)) {
     NS_ASSERTION(aDirtyFrame == aFrame->GetParent(), "Dirty frame should be viewport frame");
     // position: fixed items are reflowed into and only drawn inside the
     // viewport, or the scroll position clamping scrollport size, if one is
     // set.
     nsIPresShell* ps = aFrame->PresContext()->PresShell();
     dirtyRectRelativeToDirtyFrame.MoveTo(0, 0);
     if (ps->IsScrollPositionClampingScrollPortSizeSet()) {
       dirtyRectRelativeToDirtyFrame.SizeTo(ps->GetScrollPositionClampingScrollPortSize());
     } else {
       dirtyRectRelativeToDirtyFrame.SizeTo(aDirtyFrame->GetSize());
     }
   }
   nsRect dirty = dirtyRectRelativeToDirtyFrame - aFrame->GetOffsetTo(aDirtyFrame);
   nsRect overflowRect = aFrame->GetVisualOverflowRect();
   if (aFrame->IsTransformed() &&
       nsLayoutUtils::HasAnimationsForCompositor(aFrame->GetContent(),
                                                 eCSSProperty_transform)) {
    /**
     * Add a fuzz factor to the overflow rectangle so that elements only just
     * out of view are pulled into the display list, so they can be
     * prerendered if necessary.
     */
     overflowRect.Inflate(nsPresContext::CSSPixelsToAppUnits(32));
   }
   if (!dirty.IntersectRect(dirty, overflowRect))
     return;
   const DisplayItemClip* clip = mClipState.GetClipForContainingBlockDescendants();
   OutOfFlowDisplayData* data = clip ? new OutOfFlowDisplayData(*clip, dirty)
     : new OutOfFlowDisplayData(dirty);
   aFrame->Properties().Set(nsDisplayListBuilder::OutOfFlowDisplayDataProperty(), data);
   MarkFrameForDisplay(aFrame, aDirtyFrame);
 }
 static void UnmarkFrameForDisplay(nsIFrame* aFrame) {
   nsPresContext* presContext = aFrame->PresContext();
   presContext->PropertyTable()->
     Delete(aFrame, nsDisplayListBuilder::OutOfFlowDisplayDataProperty());
   for (nsIFrame* f = aFrame; f;
        f = nsLayoutUtils::GetParentOrPlaceholderFor(f)) {
     if (!(f->GetStateBits() & NS_FRAME_FORCE_DISPLAY_LIST_DESCEND_INTO))
       return;
     f->RemoveStateBits(NS_FRAME_FORCE_DISPLAY_LIST_DESCEND_INTO);
   }
 }
 static bool gPrintApzcTree = false;
 static bool GetApzcTreePrintPref() {
   static bool initialized = false;
   if (!initialized) {
     Preferences::AddBoolVarCache(&gPrintApzcTree, "apz.printtree", gPrintApzcTree);
     initialized = true;
   }
   return gPrintApzcTree;
 }
 static void RecordFrameMetrics(nsIFrame* aForFrame,
                                nsIFrame* aScrollFrame,
                                const nsIFrame* aReferenceFrame,
                                ContainerLayer* aRoot,
                                const nsRect& aVisibleRect,
                                const nsRect& aViewport,
                                nsRect* aDisplayPort,
                                nsRect* aCriticalDisplayPort,
                                ViewID aScrollId,
                                bool aIsRoot,
                                const ContainerLayerParameters& aContainerParameters) {
   nsPresContext* presContext = aForFrame->PresContext();
   int32_t auPerDevPixel = presContext->AppUnitsPerDevPixel();
   LayoutDeviceToLayerScale resolution(aContainerParameters.mXScale, aContainerParameters.mYScale);
   nsIntRect visible = aVisibleRect.ScaleToNearestPixels(
     resolution.scale, resolution.scale, auPerDevPixel);
   aRoot->SetVisibleRegion(visible);
   FrameMetrics metrics;
   metrics.mViewport = CSSRect::FromAppUnits(aViewport);
   if (aDisplayPort) {
     metrics.mDisplayPort = CSSRect::FromAppUnits(*aDisplayPort);
     if (aCriticalDisplayPort) {
       metrics.mCriticalDisplayPort = CSSRect::FromAppUnits(*aCriticalDisplayPort);
     }
   }
   nsIScrollableFrame* scrollableFrame = nullptr;
   if (aScrollFrame)
     scrollableFrame = aScrollFrame->GetScrollTargetFrame();
   metrics.mScrollableRect = CSSRect::FromAppUnits(
     nsLayoutUtils::CalculateScrollableRectForFrame(scrollableFrame, aForFrame));
   if (scrollableFrame) {
     nsPoint scrollPosition = scrollableFrame->GetScrollPosition();
     metrics.SetScrollOffset(CSSPoint::FromAppUnits(scrollPosition));
     // If the frame was scrolled since the last layers update, and by
     // something other than the APZ code, we want to tell the APZ to update
     // its scroll offset.
     nsIAtom* originOfLastScroll = scrollableFrame->OriginOfLastScroll();
     if (originOfLastScroll && originOfLastScroll != nsGkAtoms::apz) {
       metrics.SetScrollOffsetUpdated(scrollableFrame->CurrentScrollGeneration());
     }
   }
   metrics.SetScrollId(aScrollId);
   metrics.mIsRoot = aIsRoot;
   // Only the root scrollable frame for a given presShell should pick up
   // the presShell's resolution. All the other frames are 1.0.
   nsIPresShell* presShell = presContext->GetPresShell();
   if (aScrollFrame == presShell->GetRootScrollFrame()) {
     metrics.mResolution = ParentLayerToLayerScale(presShell->GetXResolution(),
                                                   presShell->GetYResolution());
   } else {
     metrics.mResolution = ParentLayerToLayerScale(1.0f);
   }
   // For the cumulateive resolution, multiply the resolutions of all the
   // presShells back up to the root
   metrics.mCumulativeResolution = LayoutDeviceToLayerScale(1.0f);
   nsIPresShell* curPresShell = presShell;
   while (curPresShell != nullptr) {
     ParentLayerToLayerScale presShellResolution(curPresShell->GetXResolution(),
                                                 curPresShell->GetYResolution());
     metrics.mCumulativeResolution.scale *= presShellResolution.scale;
     nsPresContext* parentContext = curPresShell->GetPresContext()->GetParentPresContext();
     curPresShell = parentContext ? parentContext->GetPresShell() : nullptr;
   }
   metrics.mDevPixelsPerCSSPixel = CSSToLayoutDeviceScale(
     (float)nsPresContext::AppUnitsPerCSSPixel() / auPerDevPixel);
   // Initially, AsyncPanZoomController should render the content to the screen
   // at the painted resolution.
   const LayerToScreenScale layerToScreenScale(1.0f);
   metrics.SetZoom(metrics.mCumulativeResolution * metrics.mDevPixelsPerCSSPixel
                   * layerToScreenScale);
   if (presShell) {
     nsIDocument* document = nullptr;
     document = presShell->GetDocument();
     if (document) {
       nsCOMPtr<nsPIDOMWindow> innerWin(document->GetInnerWindow());
       if (innerWin) {
         metrics.mMayHaveTouchListeners = innerWin->HasTouchEventListeners();
       }
     }
   }
   LayoutDeviceToParentLayerScale layoutToParentLayerScale =
     // The ScreenToParentLayerScale should be mTransformScale which is not calculated yet,
     // but we don't yet handle CSS transforms, so we assume it's 1 here.
     metrics.mCumulativeResolution * LayerToScreenScale(1.0) * ScreenToParentLayerScale(1.0);
   // Calculate the composition bounds as the size of the scroll frame and
   // its origin relative to the reference frame.
   // If aScrollFrame is null, we are in a document without a root scroll frame,
   // so it's a xul document. In this case, use the size of the viewport frame.
   nsIFrame* frameForCompositionBoundsCalculation = aScrollFrame ? aScrollFrame : aForFrame;
   nsRect compositionBounds(frameForCompositionBoundsCalculation->GetOffsetToCrossDoc(aReferenceFrame),
                            frameForCompositionBoundsCalculation->GetSize());
   metrics.mCompositionBounds = RoundedToInt(LayoutDeviceRect::FromAppUnits(compositionBounds, auPerDevPixel)
                                             * layoutToParentLayerScale);
   // For the root scroll frame of the root content document, the above calculation
   // will yield the size of the viewport frame as the composition bounds, which
   // doesn't actually correspond to what is visible when
   // nsIDOMWindowUtils::setCSSViewport has been called to modify the visible area of
   // the prescontext that the viewport frame is reflowed into. In that case if our
   // document has a widget then the widget's bounds will correspond to what is
   // visible. If we don't have a widget the root view's bounds correspond to what
   // would be visible because they don't get modified by setCSSViewport.
   bool isRootContentDocRootScrollFrame = presContext->IsRootContentDocument()
                                       && aScrollFrame == presShell->GetRootScrollFrame();
   if (isRootContentDocRootScrollFrame) {
     if (nsIFrame* rootFrame = presShell->GetRootFrame()) {
       if (nsView* view = rootFrame->GetView()) {
         nsRect viewBoundsAppUnits = view->GetBounds() + rootFrame->GetOffsetToCrossDoc(aReferenceFrame);
         ParentLayerIntRect viewBounds = RoundedToInt(LayoutDeviceRect::FromAppUnits(viewBoundsAppUnits, auPerDevPixel)
                                                      * layoutToParentLayerScale);
         // On Android, we need to do things a bit differently to get things
         // right (see bug 983208, bug 988882). We use the bounds of the nearest
         // widget, but clamp the height to the view bounds height. This clamping
         // is done to get correct results for a page where the page is sized to
         // the screen and thus the dynamic toolbar never disappears. In such a
         // case, we want the composition bounds to exclude the toolbar height,
         // but the widget bounds includes it. We don't currently have a good way
         // of knowing about the toolbar height, but clamping to the view bounds
         // height gives the correct answer in the cases we care about.
         nsIWidget* widget =
 #ifdef MOZ_WIDGET_ANDROID
             rootFrame->GetNearestWidget();
 #else
             view->GetWidget();
 #endif
         if (widget) {
           nsIntRect widgetBounds;
           widget->GetBounds(widgetBounds);
           metrics.mCompositionBounds = ViewAs<ParentLayerPixel>(widgetBounds);
 #ifdef MOZ_WIDGET_ANDROID
           if (viewBounds.height < metrics.mCompositionBounds.height) {
             metrics.mCompositionBounds.height = viewBounds.height;
           }
 #endif
         } else {
           metrics.mCompositionBounds = viewBounds;
         }
       }
     }
   }
   // Adjust composition bounds for the size of scroll bars.
   if (scrollableFrame && !LookAndFeel::GetInt(LookAndFeel::eIntID_UseOverlayScrollbars)) {
     nsMargin sizes = scrollableFrame->GetActualScrollbarSizes();
     // Scrollbars are not subject to scaling, so CSS pixels = layer pixels for them.
     ParentLayerIntMargin boundMargins = RoundedToInt(CSSMargin::FromAppUnits(sizes) * CSSToParentLayerScale(1.0f));
     metrics.mCompositionBounds.Deflate(boundMargins);
   }
   metrics.SetRootCompositionSize(
     nsLayoutUtils::CalculateRootCompositionSize(aScrollFrame ? aScrollFrame : aForFrame,
                                                 isRootContentDocRootScrollFrame, metrics));
   if (GetApzcTreePrintPref()) {
     if (nsIContent* content = frameForCompositionBoundsCalculation->GetContent()) {
       nsAutoString contentDescription;
       content->Describe(contentDescription);
       metrics.SetContentDescription(NS_LossyConvertUTF16toASCII(contentDescription).get());
     }
   }
   metrics.mPresShellId = presShell->GetPresShellId();
   // If the scroll frame's content is marked 'scrollgrab', record this
   // in the FrameMetrics so APZ knows to provide the scroll grabbing
   // behaviour.
   if (aScrollFrame && nsContentUtils::HasScrollgrab(aScrollFrame->GetContent())) {
     metrics.mHasScrollgrab = true;
   }
   aRoot->SetFrameMetrics(metrics);
 }
 nsDisplayListBuilder::~nsDisplayListBuilder() {
   NS_ASSERTION(mFramesMarkedForDisplay.Length() == 0,
                "All frames should have been unmarked");
   NS_ASSERTION(mPresShellStates.Length() == 0,
                "All presshells should have been exited");
   NS_ASSERTION(!mCurrentTableItem, "No table item should be active");
   nsCSSRendering::EndFrameTreesLocked();
   for (uint32_t i = 0; i < mDisplayItemClipsToDestroy.Length(); ++i) {
     mDisplayItemClipsToDestroy[i]->DisplayItemClip::~DisplayItemClip();
   }
   PL_FinishArenaPool(&mPool);
   MOZ_COUNT_DTOR(nsDisplayListBuilder);
 }
 uint32_t
 nsDisplayListBuilder::GetBackgroundPaintFlags() {
   uint32_t flags = 0;
   if (mSyncDecodeImages) {
     flags |= nsCSSRendering::PAINTBG_SYNC_DECODE_IMAGES;
   }
   if (mIsPaintingToWindow) {
     flags |= nsCSSRendering::PAINTBG_TO_WINDOW;
   }
   return flags;
 }
 void
 nsDisplayListBuilder::SubtractFromVisibleRegion(nsRegion* aVisibleRegion,
                                                 const nsRegion& aRegion)
 {
   if (aRegion.IsEmpty())
     return;
   nsRegion tmp;
   tmp.Sub(*aVisibleRegion, aRegion);
   // Don't let *aVisibleRegion get too complex, but don't let it fluff out
   // to its bounds either, which can be very bad (see bug 516740).
   // Do let aVisibleRegion get more complex if by doing so we reduce its
   // area by at least half.
   if (GetAccurateVisibleRegions() || tmp.GetNumRects() <= 15 ||
       tmp.Area() <= aVisibleRegion->Area()/2) {
     *aVisibleRegion = tmp;
   }
 }
 nsCaret *
 nsDisplayListBuilder::GetCaret() {
   nsRefPtr<nsCaret> caret = CurrentPresShellState()->mPresShell->GetCaret();
   return caret;
 }
 void
 nsDisplayListBuilder::EnterPresShell(nsIFrame* aReferenceFrame,
                                      const nsRect& aDirtyRect) {
   PresShellState* state = mPresShellStates.AppendElement();
   if (!state)
     return;
   state->mPresShell = aReferenceFrame->PresContext()->PresShell();
   state->mCaretFrame = nullptr;
   state->mFirstFrameMarkedForDisplay = mFramesMarkedForDisplay.Length();
   state->mPresShell->UpdateCanvasBackground();
   if (mIsPaintingToWindow) {
     mReferenceFrame->AddPaintedPresShell(state->mPresShell);
     state->mPresShell->IncrementPaintCount();
   }
   bool buildCaret = mBuildCaret;
   if (mIgnoreSuppression || !state->mPresShell->IsPaintingSuppressed()) {
     if (state->mPresShell->IsPaintingSuppressed()) {
       mHadToIgnoreSuppression = true;
     }
     state->mIsBackgroundOnly = false;
   } else {
     state->mIsBackgroundOnly = true;
     buildCaret = false;
   }
   if (!buildCaret)
     return;
   nsRefPtr<nsCaret> caret = state->mPresShell->GetCaret();
   state->mCaretFrame = caret->GetCaretFrame();
   NS_ASSERTION(state->mCaretFrame == caret->GetCaretFrame(),
                "GetCaretFrame() is unstable");
   if (state->mCaretFrame) {
     // Check if the dirty rect intersects with the caret's dirty rect.
     nsRect caretRect =
       caret->GetCaretRect() + state->mCaretFrame->GetOffsetTo(aReferenceFrame);
     if (caretRect.Intersects(aDirtyRect)) {
       // Okay, our rects intersect, let's mark the frame and all of its ancestors.
       mFramesMarkedForDisplay.AppendElement(state->mCaretFrame);
       MarkFrameForDisplay(state->mCaretFrame, nullptr);
     }
   }
 }
 void
 nsDisplayListBuilder::LeavePresShell(nsIFrame* aReferenceFrame,
                                      const nsRect& aDirtyRect) {
   if (CurrentPresShellState()->mPresShell != aReferenceFrame->PresContext()->PresShell()) {
     // Must have not allocated a state for this presshell, presumably due
     // to OOM.
     return;
   }
   ResetMarkedFramesForDisplayList();
   mPresShellStates.SetLength(mPresShellStates.Length() - 1);
 }
 void
 nsDisplayListBuilder::ResetMarkedFramesForDisplayList()
 {
   // Unmark and pop off the frames marked for display in this pres shell.
   uint32_t firstFrameForShell = CurrentPresShellState()->mFirstFrameMarkedForDisplay;
   for (uint32_t i = firstFrameForShell;
        i < mFramesMarkedForDisplay.Length(); ++i) {
     UnmarkFrameForDisplay(mFramesMarkedForDisplay[i]);
   }
   mFramesMarkedForDisplay.SetLength(firstFrameForShell);
 }
 void
 nsDisplayListBuilder::MarkFramesForDisplayList(nsIFrame* aDirtyFrame,
                                                const nsFrameList& aFrames,
                                                const nsRect& aDirtyRect) {
   mFramesMarkedForDisplay.SetCapacity(mFramesMarkedForDisplay.Length() + aFrames.GetLength());
   for (nsFrameList::Enumerator e(aFrames); !e.AtEnd(); e.Next()) {
     mFramesMarkedForDisplay.AppendElement(e.get());
     MarkOutOfFlowFrameForDisplay(aDirtyFrame, e.get(), aDirtyRect);
   }
 }
 void
 nsDisplayListBuilder::MarkPreserve3DFramesForDisplayList(nsIFrame* aDirtyFrame, const nsRect& aDirtyRect)
 {
   nsAutoTArray<nsIFrame::ChildList,4> childListArray;
   aDirtyFrame->GetChildLists(&childListArray);
   nsIFrame::ChildListArrayIterator lists(childListArray);
   for (; !lists.IsDone(); lists.Next()) {
     nsFrameList::Enumerator childFrames(lists.CurrentList());
     for (; !childFrames.AtEnd(); childFrames.Next()) {
       nsIFrame *child = childFrames.get();
       if (child->Preserves3D()) {
         mFramesMarkedForDisplay.AppendElement(child);
         nsRect dirty = aDirtyRect - child->GetOffsetTo(aDirtyFrame);
         child->Properties().Set(nsDisplayListBuilder::Preserve3DDirtyRectProperty(),
                            new nsRect(dirty));
         MarkFrameForDisplay(child, aDirtyFrame);
       }
     }
   }
 }
 void*
 nsDisplayListBuilder::Allocate(size_t aSize) {
   void *tmp;
   PL_ARENA_ALLOCATE(tmp, &mPool, aSize);
   if (!tmp) {
     NS_RUNTIMEABORT("out of memory");
   }
   return tmp;
 }
 const DisplayItemClip*
 nsDisplayListBuilder::AllocateDisplayItemClip(const DisplayItemClip& aOriginal)
 {
   void* p = Allocate(sizeof(DisplayItemClip));
   if (!aOriginal.GetRoundedRectCount()) {
     memcpy(p, &aOriginal, sizeof(DisplayItemClip));
     return static_cast<DisplayItemClip*>(p);
   }
   DisplayItemClip* c = new (p) DisplayItemClip(aOriginal);
   mDisplayItemClipsToDestroy.AppendElement(c);
   return c;
 }
 void nsDisplayListSet::MoveTo(const nsDisplayListSet& aDestination) const
 {
   aDestination.BorderBackground()->AppendToTop(BorderBackground());
   aDestination.BlockBorderBackgrounds()->AppendToTop(BlockBorderBackgrounds());
   aDestination.Floats()->AppendToTop(Floats());
   aDestination.Content()->AppendToTop(Content());
   aDestination.PositionedDescendants()->AppendToTop(PositionedDescendants());
   aDestination.Outlines()->AppendToTop(Outlines());
 }
 void
 nsDisplayList::FlattenTo(nsTArray<nsDisplayItem*>* aElements) {
   nsDisplayItem* item;
   while ((item = RemoveBottom()) != nullptr) {
     if (item->GetType() == nsDisplayItem::TYPE_WRAP_LIST) {
       item->GetSameCoordinateSystemChildren()->FlattenTo(aElements);
       item->~nsDisplayItem();
     } else {
       aElements->AppendElement(item);
     }
   }
 }
 nsRect
 nsDisplayList::GetBounds(nsDisplayListBuilder* aBuilder) const {
   nsRect bounds;
   for (nsDisplayItem* i = GetBottom(); i != nullptr; i = i->GetAbove()) {
     bounds.UnionRect(bounds, i->GetClippedBounds(aBuilder));
   }
   return bounds;
 }
 bool
 nsDisplayList::ComputeVisibilityForRoot(nsDisplayListBuilder* aBuilder,
                                         nsRegion* aVisibleRegion,
                                         nsIFrame* aDisplayPortFrame) {
   PROFILER_LABEL("nsDisplayList", "ComputeVisibilityForRoot");
   nsRegion r;
   r.And(*aVisibleRegion, GetBounds(aBuilder));
   return ComputeVisibilityForSublist(aBuilder, aVisibleRegion,
                                      r.GetBounds(), r.GetBounds(),
                                      aDisplayPortFrame);
 }
 static nsRegion
 TreatAsOpaque(nsDisplayItem* aItem, nsDisplayListBuilder* aBuilder)
 {
   bool snap;
   nsRegion opaque = aItem->GetOpaqueRegion(aBuilder, &snap);
   if (aBuilder->IsForPluginGeometry()) {
     // Treat all leaf chrome items as opaque, unless their frames are opacity:0.
     // Since opacity:0 frames generate an nsDisplayOpacity, that item will
     // not be treated as opaque here, so opacity:0 chrome content will be
     // effectively ignored, as it should be.
     // We treat leaf chrome items as opaque to ensure that they cover
     // content plugins, for security reasons.
     // Non-leaf chrome items don't render contents of their own so shouldn't
     // be treated as opaque (and their bounds is just the union of their
     // children, which might be a large area their contents don't really cover).
     nsIFrame* f = aItem->Frame();
     if (f->PresContext()->IsChrome() && !aItem->GetChildren() &&
         f->StyleDisplay()->mOpacity != 0.0) {
       opaque = aItem->GetBounds(aBuilder, &snap);
     }
   }
   if (opaque.IsEmpty()) {
     return opaque;
   }
   nsRegion opaqueClipped;
   nsRegionRectIterator iter(opaque);
   for (const nsRect* r = iter.Next(); r; r = iter.Next()) {
     opaqueClipped.Or(opaqueClipped, aItem->GetClip().ApproximateIntersectInward(*r));
   }
   return opaqueClipped;
 }
 /* Checks if aPotentialScrollItem is a scroll layer item and aPotentialScrollbarItem
  * is an overlay scrollbar item for the same scroll frame.
  */
 static bool
 IsScrollLayerItemAndOverlayScrollbarForScrollFrame(
   nsDisplayItem* aPotentialScrollItem, nsDisplayItem* aPotentialScrollbarItem)
 {
   if (aPotentialScrollItem->GetType() == nsDisplayItem::TYPE_SCROLL_LAYER &&
       aPotentialScrollbarItem &&
       aPotentialScrollbarItem->GetType() == nsDisplayItem::TYPE_OWN_LAYER &&
       LookAndFeel::GetInt(LookAndFeel::eIntID_UseOverlayScrollbars)) {
     nsDisplayScrollLayer* scrollItem =
       static_cast<nsDisplayScrollLayer*>(aPotentialScrollItem);
     nsDisplayOwnLayer* layerItem =
       static_cast<nsDisplayOwnLayer*>(aPotentialScrollbarItem);
     if ((layerItem->GetFlags() &
          (nsDisplayOwnLayer::VERTICAL_SCROLLBAR |
           nsDisplayOwnLayer::HORIZONTAL_SCROLLBAR)) &&
         layerItem->Frame()->GetParent() == scrollItem->GetScrollFrame()) {
       return true;
     }
   }
   return false;
 }
 bool
 nsDisplayList::ComputeVisibilityForSublist(nsDisplayListBuilder* aBuilder,
                                            nsRegion* aVisibleRegion,
                                            const nsRect& aListVisibleBounds,
                                            const nsRect& aAllowVisibleRegionExpansion,
                                            nsIFrame* aDisplayPortFrame) {
 #ifdef DEBUG
   nsRegion r;
   r.And(*aVisibleRegion, GetBounds(aBuilder));
   NS_ASSERTION(r.GetBounds().IsEqualInterior(aListVisibleBounds),
                "bad aListVisibleBounds");
 #endif
   mVisibleRect = aListVisibleBounds;
   bool anyVisible = false;
   nsAutoTArray<nsDisplayItem*, 512> elements;
   FlattenTo(&elements);
   bool forceTransparentSurface = false;
   for (int32_t i = elements.Length() - 1; i >= 0; --i) {
     nsDisplayItem* item = elements[i];
     nsDisplayItem* belowItem = i < 1 ? nullptr : elements[i - 1];
     nsDisplayList* list = item->GetSameCoordinateSystemChildren();
     if (aBuilder->AllowMergingAndFlattening()) {
       if (belowItem && item->TryMerge(aBuilder, belowItem)) {
         belowItem->~nsDisplayItem();
         elements.ReplaceElementsAt(i - 1, 1, item);
         continue;
       }
       // If an overlay scrollbar item is between a scroll layer item and the
       // other scroll layer items that we need to merge with just move the
       // scrollbar item up, that way it will be on top of the scrolled content
       // and we can try to merge all the scroll layer items.
       if (IsScrollLayerItemAndOverlayScrollbarForScrollFrame(item, belowItem)) {
         elements[i] = belowItem;
         elements[i-1] = item;
         i++;
         continue;
       }
       if (list && item->ShouldFlattenAway(aBuilder)) {
         // The elements on the list >= i no longer serve any use.
         elements.SetLength(i);
         list->FlattenTo(&elements);
         i = elements.Length();
         item->~nsDisplayItem();
         continue;
       }
     }
     nsRect bounds = item->GetClippedBounds(aBuilder);
     nsRegion itemVisible;
     itemVisible.And(*aVisibleRegion, bounds);
     item->mVisibleRect = itemVisible.GetBounds();
     if (item->ComputeVisibility(aBuilder, aVisibleRegion,
                                 aAllowVisibleRegionExpansion.Intersect(bounds))) {
       anyVisible = true;
       // If we're in a displayport, we need to make sure that fixed position
       // items do not subtract from the visible region, as async scrolling
       // may expose these occluded areas.
       // If the item is fixed pos in the same document as the displayport
       // then don't let it occlude this list. The only other case possible
       // is that the fixed pos content is in a child document, in which it
       // would scroll with the rest of the content.
       bool occlude = true;
       if (aDisplayPortFrame && item->IsInFixedPos()) {
         if (item->Frame()->PresContext() == aDisplayPortFrame->PresContext()) {
           occlude = false;
         }
       }
       if (occlude) {
         nsRegion opaque = TreatAsOpaque(item, aBuilder);
         // Subtract opaque item from the visible region
         aBuilder->SubtractFromVisibleRegion(aVisibleRegion, opaque);
       }
       if (aBuilder->NeedToForceTransparentSurfaceForItem(item) ||
           (list && list->NeedsTransparentSurface())) {
         forceTransparentSurface = true;
       }
     }
     AppendToBottom(item);
   }
   mIsOpaque = !aVisibleRegion->Intersects(mVisibleRect);
   mForceTransparentSurface = forceTransparentSurface;
 #if defined(DEBUG) || defined(MOZ_DUMP_PAINTING)
   mDidComputeVisibility = true;
 #endif
   return anyVisible;
 }
 void nsDisplayList::PaintRoot(nsDisplayListBuilder* aBuilder,
                               nsRenderingContext* aCtx,
                               uint32_t aFlags) const {
   PROFILER_LABEL("nsDisplayList", "PaintRoot");
   PaintForFrame(aBuilder, aCtx, aBuilder->RootReferenceFrame(), aFlags);
 }
 /**
  * We paint by executing a layer manager transaction, constructing a
  * single layer representing the display list, and then making it the
  * root of the layer manager, drawing into the ThebesLayers.
  */
 void nsDisplayList::PaintForFrame(nsDisplayListBuilder* aBuilder,
                                   nsRenderingContext* aCtx,
                                   nsIFrame* aForFrame,
                                   uint32_t aFlags) const {
   NS_ASSERTION(mDidComputeVisibility,
                "Must call ComputeVisibility before calling Paint");
   nsRefPtr<LayerManager> layerManager;
   bool widgetTransaction = false;
   bool allowRetaining = false;
   bool doBeginTransaction = true;
   nsView *view = nullptr;
   if (aFlags & PAINT_USE_WIDGET_LAYERS) {
     nsIFrame* rootReferenceFrame = aBuilder->RootReferenceFrame();
     view = rootReferenceFrame->GetView();
     NS_ASSERTION(rootReferenceFrame == nsLayoutUtils::GetDisplayRootFrame(rootReferenceFrame),
                  "Reference frame must be a display root for us to use the layer manager");
     nsIWidget* window = rootReferenceFrame->GetNearestWidget();
     if (window) {
       layerManager = window->GetLayerManager(&allowRetaining);
       if (layerManager) {
         doBeginTransaction = !(aFlags & PAINT_EXISTING_TRANSACTION);
         widgetTransaction = true;
       }
     }
   }
   if (!layerManager) {
     if (!aCtx) {
       NS_WARNING("Nowhere to paint into");
       return;
     }
     layerManager = new BasicLayerManager();
   }
   // Store the existing layer builder to reinstate it on return.
   FrameLayerBuilder *oldBuilder = layerManager->GetLayerBuilder();
   FrameLayerBuilder *layerBuilder = new FrameLayerBuilder();
   layerBuilder->Init(aBuilder, layerManager);
   if (aFlags & PAINT_COMPRESSED) {
     layerBuilder->SetLayerTreeCompressionMode();
   }
   if (aFlags & PAINT_FLUSH_LAYERS) {
     FrameLayerBuilder::InvalidateAllLayers(layerManager);
   }
   if (doBeginTransaction) {
     if (aCtx) {
       layerManager->BeginTransactionWithTarget(aCtx->ThebesContext());
     } else {
       layerManager->BeginTransaction();
     }
   }
   if (widgetTransaction) {
     layerBuilder->DidBeginRetainedLayerTransaction(layerManager);
   }
   nsPresContext* presContext = aForFrame->PresContext();
   nsIPresShell* presShell = presContext->GetPresShell();
   NotifySubDocInvalidationFunc computeInvalidFunc =
     presContext->MayHavePaintEventListenerInSubDocument() ? nsPresContext::NotifySubDocInvalidation : 0;
   bool computeInvalidRect = (computeInvalidFunc ||
                              (!layerManager->IsCompositingCheap() && layerManager->NeedsWidgetInvalidation())) &&
                             widgetTransaction;
   nsAutoPtr<LayerProperties> props(computeInvalidRect ?
                                      LayerProperties::CloneFrom(layerManager->GetRoot()) :
                                      nullptr);
   ContainerLayerParameters containerParameters
     (presShell->GetXResolution(), presShell->GetYResolution());
   nsRefPtr<ContainerLayer> root = layerBuilder->
     BuildContainerLayerFor(aBuilder, layerManager, aForFrame, nullptr, *this,
                            containerParameters, nullptr);
   nsIDocument* document = nullptr;
   if (presShell) {
     document = presShell->GetDocument();
   }
   if (widgetTransaction ||
       // SVG-as-an-image docs don't paint as part of the retained layer tree,
       // but they still need the invalidation state bits cleared in order for
       // invalidation for CSS/SMIL animation to work properly.
       (document && document->IsBeingUsedAsImage())) {
     aForFrame->ClearInvalidationStateBits();
   }
   if (!root) {
     layerManager->SetUserData(&gLayerManagerLayerBuilder, oldBuilder);
     return;
   }
   // Root is being scaled up by the X/Y resolution. Scale it back down.
   root->SetPostScale(1.0f/containerParameters.mXScale,
 .0f/containerParameters.mYScale);
   ViewID id = FrameMetrics::NULL_SCROLL_ID;
   bool isRoot = presContext->IsRootContentDocument();
   nsIFrame* rootScrollFrame = presShell->GetRootScrollFrame();
   nsRect displayport, criticalDisplayport;
   bool usingDisplayport = false;
   bool usingCriticalDisplayport = false;
   if (rootScrollFrame) {
     nsIContent* content = rootScrollFrame->GetContent();
     if (content) {
       usingDisplayport = nsLayoutUtils::GetDisplayPort(content, &displayport);
       usingCriticalDisplayport =
         nsLayoutUtils::GetCriticalDisplayPort(content, &criticalDisplayport);
       // If this is the root content document, we want it to have a scroll id.
       if (isRoot) {
         id = nsLayoutUtils::FindOrCreateIDFor(content);
       }
     }
   }
   nsRect viewport(aBuilder->ToReferenceFrame(aForFrame), aForFrame->GetSize());
   RecordFrameMetrics(aForFrame, rootScrollFrame,
                      aBuilder->FindReferenceFrameFor(aForFrame),
                      root, mVisibleRect, viewport,
                      (usingDisplayport ? &displayport : nullptr),
                      (usingCriticalDisplayport ? &criticalDisplayport : nullptr),
                      id, isRoot, containerParameters);
   if (usingDisplayport &&
       !(root->GetContentFlags() & Layer::CONTENT_OPAQUE)) {
     // See bug 693938, attachment 567017
     NS_WARNING("Transparent content with displayports can be expensive.");
   }
   layerManager->SetRoot(root);
   layerBuilder->WillEndTransaction();
   bool temp = aBuilder->SetIsCompositingCheap(layerManager->IsCompositingCheap());
   LayerManager::EndTransactionFlags flags = LayerManager::END_DEFAULT;
   if (layerManager->NeedsWidgetInvalidation()) {
     if (aFlags & PAINT_NO_COMPOSITE) {
       flags = LayerManager::END_NO_COMPOSITE;
     }
   } else {
     // Client layer managers never composite directly, so
     // we don't need to worry about END_NO_COMPOSITE.
     if (aBuilder->WillComputePluginGeometry()) {
       flags = LayerManager::END_NO_REMOTE_COMPOSITE;
     }
   }
   layerManager->EndTransaction(FrameLayerBuilder::DrawThebesLayer,
                                aBuilder, flags);
   aBuilder->SetIsCompositingCheap(temp);
   layerBuilder->DidEndTransaction();
   nsIntRegion invalid;
   if (props) {
     invalid = props->ComputeDifferences(root, computeInvalidFunc);
   } else if (widgetTransaction) {
     LayerProperties::ClearInvalidations(root);
   }
   bool shouldInvalidate = layerManager->NeedsWidgetInvalidation();
   if (view) {
     if (props) {
       if (!invalid.IsEmpty()) {
         nsIntRect bounds = invalid.GetBounds();
         nsRect rect(presContext->DevPixelsToAppUnits(bounds.x),
                     presContext->DevPixelsToAppUnits(bounds.y),
                     presContext->DevPixelsToAppUnits(bounds.width),
                     presContext->DevPixelsToAppUnits(bounds.height));
         if (shouldInvalidate) {
           view->GetViewManager()->InvalidateViewNoSuppression(view, rect);
         }
         presContext->NotifyInvalidation(bounds, 0);
       }
     } else if (shouldInvalidate) {
       view->GetViewManager()->InvalidateView(view);
     }
   }
   if (aFlags & PAINT_FLUSH_LAYERS) {
     FrameLayerBuilder::InvalidateAllLayers(layerManager);
   }
   layerManager->SetUserData(&gLayerManagerLayerBuilder, oldBuilder);
 }
 uint32_t nsDisplayList::Count() const {
   uint32_t count = 0;
   for (nsDisplayItem* i = GetBottom(); i; i = i->GetAbove()) {
     ++count;
   }
   return count;
 }
 nsDisplayItem* nsDisplayList::RemoveBottom() {
   nsDisplayItem* item = mSentinel.mAbove;
   if (!item)
     return nullptr;
   mSentinel.mAbove = item->mAbove;
   if (item == mTop) {
     // must have been the only item
     mTop = &mSentinel;
   }
   item->mAbove = nullptr;
   return item;
 }
 void nsDisplayList::DeleteAll() {
   nsDisplayItem* item;
   while ((item = RemoveBottom()) != nullptr) {
     item->~nsDisplayItem();
   }
 }
 static bool
 GetMouseThrough(const nsIFrame* aFrame)
 {
   if (!aFrame->IsBoxFrame())
     return false;
   const nsIFrame* frame = aFrame;
   while (frame) {
     if (frame->GetStateBits() & NS_FRAME_MOUSE_THROUGH_ALWAYS) {
       return true;
     } else if (frame->GetStateBits() & NS_FRAME_MOUSE_THROUGH_NEVER) {
       return false;
     }
     frame = frame->GetParentBox();
   }
   return false;
 }
 static bool
 IsFrameReceivingPointerEvents(nsIFrame* aFrame)
 {
   nsSubDocumentFrame* frame = do_QueryFrame(aFrame);
   if (frame && frame->PassPointerEventsToChildren()) {
     return true;
   }
   return NS_STYLE_POINTER_EVENTS_NONE !=
     aFrame->StyleVisibility()->GetEffectivePointerEvents(aFrame);
 }
 // A list of frames, and their z depth. Used for sorting
 // the results of hit testing.
 struct FramesWithDepth
 {
   FramesWithDepth(float aDepth) :
     mDepth(aDepth)
   {}
   bool operator<(const FramesWithDepth& aOther) const {
     if (mDepth != aOther.mDepth) {
       // We want to sort so that the shallowest item (highest depth value) is first
       return mDepth > aOther.mDepth;
     }
     return this < &aOther;
   }
   bool operator==(const FramesWithDepth& aOther) const {
     return this == &aOther;
   }
   float mDepth;
   nsTArray<nsIFrame*> mFrames;
 };
 // Sort the frames by depth and then moves all the contained frames to the destination
 void FlushFramesArray(nsTArray<FramesWithDepth>& aSource, nsTArray<nsIFrame*>* aDest)
 {
   if (aSource.IsEmpty()) {
     return;
   }
   aSource.Sort();
   uint32_t length = aSource.Length();
   for (uint32_t i = 0; i < length; i++) {
     aDest->MoveElementsFrom(aSource[i].mFrames);
   }
   aSource.Clear();
 }
 void nsDisplayList::HitTest(nsDisplayListBuilder* aBuilder, const nsRect& aRect,
                             nsDisplayItem::HitTestState* aState,
                             nsTArray<nsIFrame*> *aOutFrames) const {
   int32_t itemBufferStart = aState->mItemBuffer.Length();
   nsDisplayItem* item;
   for (item = GetBottom(); item; item = item->GetAbove()) {
     aState->mItemBuffer.AppendElement(item);
   }
   nsAutoTArray<FramesWithDepth, 16> temp;
   for (int32_t i = aState->mItemBuffer.Length() - 1; i >= itemBufferStart; --i) {
     // Pop element off the end of the buffer. We want to shorten the buffer
     // so that recursive calls to HitTest have more buffer space.
     item = aState->mItemBuffer[i];
     aState->mItemBuffer.SetLength(i);
     bool snap;
     nsRect r = item->GetBounds(aBuilder, &snap).Intersect(aRect);
     if (item->GetClip().MayIntersect(r)) {
       nsAutoTArray<nsIFrame*, 16> outFrames;
       item->HitTest(aBuilder, aRect, aState, &outFrames);
       // For 3d transforms with preserve-3d we add hit frames into the temp list
       // so we can sort them later, otherwise we add them directly to the output list.
       nsTArray<nsIFrame*> *writeFrames = aOutFrames;
       if (item->GetType() == nsDisplayItem::TYPE_TRANSFORM &&
           item->Frame()->Preserves3D()) {
         if (outFrames.Length()) {
           nsDisplayTransform *transform = static_cast<nsDisplayTransform*>(item);
           nsPoint point = aRect.TopLeft();
           // A 1x1 rect means a point, otherwise use the center of the rect
           if (aRect.width != 1 || aRect.height != 1) {
             point = aRect.Center();
           }
           temp.AppendElement(FramesWithDepth(transform->GetHitDepthAtPoint(aBuilder, point)));
           writeFrames = &temp[temp.Length() - 1].mFrames;
         }
       } else {
         // We may have just finished a run of consecutive preserve-3d transforms,
         // so flush these into the destination array before processing our frame list.
         FlushFramesArray(temp, aOutFrames);
       }
       for (uint32_t j = 0; j < outFrames.Length(); j++) {
         nsIFrame *f = outFrames.ElementAt(j);
         // Handle the XUL 'mousethrough' feature and 'pointer-events'.
         if (!GetMouseThrough(f) && IsFrameReceivingPointerEvents(f)) {
           writeFrames->AppendElement(f);
         }
       }
     }
   }
   // Clear any remaining preserve-3d transforms.
   FlushFramesArray(temp, aOutFrames);
   NS_ASSERTION(aState->mItemBuffer.Length() == uint32_t(itemBufferStart),
                "How did we forget to pop some elements?");
 }
 static void Sort(nsDisplayList* aList, int32_t aCount, nsDisplayList::SortLEQ aCmp,
                  void* aClosure) {
   if (aCount < 2)
     return;
   nsDisplayList list1;
   nsDisplayList list2;
   int i;
   int32_t half = aCount/2;
   bool sorted = true;
   nsDisplayItem* prev = nullptr;
   for (i = 0; i < aCount; ++i) {
     nsDisplayItem* item = aList->RemoveBottom();
     (i < half ? &list1 : &list2)->AppendToTop(item);
     if (sorted && prev && !aCmp(prev, item, aClosure)) {
       sorted = false;
     }
     prev = item;
   }
   if (sorted) {
     aList->AppendToTop(&list1);
     aList->AppendToTop(&list2);
     return;
   }
   Sort(&list1, half, aCmp, aClosure);
   Sort(&list2, aCount - half, aCmp, aClosure);
   for (i = 0; i < aCount; ++i) {
     if (list1.GetBottom() &&
         (!list2.GetBottom() ||
          aCmp(list1.GetBottom(), list2.GetBottom(), aClosure))) {
       aList->AppendToTop(list1.RemoveBottom());
     } else {
       aList->AppendToTop(list2.RemoveBottom());
     }
   }
 }
 static nsIContent* FindContentInDocument(nsDisplayItem* aItem, nsIDocument* aDoc) {
   nsIFrame* f = aItem->Frame();
   while (f) {
     nsPresContext* pc = f->PresContext();
     if (pc->Document() == aDoc) {
       return f->GetContent();
     }
     f = nsLayoutUtils::GetCrossDocParentFrame(pc->PresShell()->GetRootFrame());
   }
   return nullptr;
 }
 static bool IsContentLEQ(nsDisplayItem* aItem1, nsDisplayItem* aItem2,
                          void* aClosure) {
   nsIContent* commonAncestor = static_cast<nsIContent*>(aClosure);
   // It's possible that the nsIContent for aItem1 or aItem2 is in a subdocument
   // of commonAncestor, because display items for subdocuments have been
   // mixed into the same list. Ensure that we're looking at content
   // in commonAncestor's document.
   nsIDocument* commonAncestorDoc = commonAncestor->OwnerDoc();
   nsIContent* content1 = FindContentInDocument(aItem1, commonAncestorDoc);
   nsIContent* content2 = FindContentInDocument(aItem2, commonAncestorDoc);
   if (!content1 || !content2) {
     NS_ERROR("Document trees are mixed up!");
     // Something weird going on
     return true;
   }
   return nsLayoutUtils::CompareTreePosition(content1, content2, commonAncestor) <= 0;
 }
 static bool IsZOrderLEQ(nsDisplayItem* aItem1, nsDisplayItem* aItem2,
                         void* aClosure) {
   // Note that we can't just take the difference of the two
   // z-indices here, because that might overflow a 32-bit int.
   return aItem1->ZIndex() <= aItem2->ZIndex();
 }
 void nsDisplayList::SortByZOrder(nsDisplayListBuilder* aBuilder,
                                  nsIContent* aCommonAncestor) {
   Sort(aBuilder, IsZOrderLEQ, aCommonAncestor);
 }
 void nsDisplayList::SortByContentOrder(nsDisplayListBuilder* aBuilder,
                                        nsIContent* aCommonAncestor) {
   Sort(aBuilder, IsContentLEQ, aCommonAncestor);
 }
 void nsDisplayList::Sort(nsDisplayListBuilder* aBuilder,
                          SortLEQ aCmp, void* aClosure) {
   ::Sort(this, Count(), aCmp, aClosure);
 }
 void
 nsDisplayItem::AddInvalidRegionForSyncDecodeBackgroundImages(
   nsDisplayListBuilder* aBuilder,
   const nsDisplayItemGeometry* aGeometry,
   nsRegion* aInvalidRegion)
 {
   if (aBuilder->ShouldSyncDecodeImages()) {
     if (!nsCSSRendering::AreAllBackgroundImagesDecodedForFrame(mFrame)) {
       bool snap;
       aInvalidRegion->Or(*aInvalidRegion, GetBounds(aBuilder, &snap));
     }
   }
 }
 /* static */ bool
 nsDisplayItem::ForceActiveLayers()
 {
   static bool sForce = false;
   static bool sForceCached = false;
   if (!sForceCached) {
     Preferences::AddBoolVarCache(&sForce, "layers.force-active", false);
     sForceCached = true;
   }
   return sForce;
 }
 /* static */ int32_t
 nsDisplayItem::MaxActiveLayers()
 {
   static int32_t sMaxLayers = false;
   static bool sMaxLayersCached = false;
   if (!sMaxLayersCached) {
     Preferences::AddIntVarCache(&sMaxLayers, "layers.max-active", -1);
     sMaxLayersCached = true;
   }
   return sMaxLayers;
 }
 int32_t
 nsDisplayItem::ZIndex() const
 {
   if (!mFrame->IsPositioned() && !mFrame->IsFlexItem())
     return 0;
   const nsStylePosition* position = mFrame->StylePosition();
   if (position->mZIndex.GetUnit() == eStyleUnit_Integer)
     return position->mZIndex.GetIntValue();
   // sort the auto and 0 elements together
   return 0;
 }
 bool
 nsDisplayItem::RecomputeVisibility(nsDisplayListBuilder* aBuilder,
                                    nsRegion* aVisibleRegion) {
   nsRect bounds = GetClippedBounds(aBuilder);
   nsRegion itemVisible;
   itemVisible.And(*aVisibleRegion, bounds);
   mVisibleRect = itemVisible.GetBounds();
   // When we recompute visibility within layers we don't need to
   // expand the visible region for content behind plugins (the plugin
   // is not in the layer).
   if (!ComputeVisibility(aBuilder, aVisibleRegion, nsRect()))
     return false;
   nsRegion opaque = TreatAsOpaque(this, aBuilder);
   aBuilder->SubtractFromVisibleRegion(aVisibleRegion, opaque);
   return true;
 }
 nsRect
 nsDisplayItem::GetClippedBounds(nsDisplayListBuilder* aBuilder)
 {
   bool snap;
   nsRect r = GetBounds(aBuilder, &snap);
   return GetClip().ApplyNonRoundedIntersection(r);
 }
 nsRect
 nsDisplaySolidColor::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap)
 {
   *aSnap = true;
   return mBounds;
 }
 void
 nsDisplaySolidColor::Paint(nsDisplayListBuilder* aBuilder,
                            nsRenderingContext* aCtx)
 {
   aCtx->SetColor(mColor);
   aCtx->FillRect(mVisibleRect);
 }
 #ifdef MOZ_DUMP_PAINTING
 void
 nsDisplaySolidColor::WriteDebugInfo(nsACString& aTo)
 {
   aTo += nsPrintfCString(" (rgba %d,%d,%d,%d)",
                  NS_GET_R(mColor), NS_GET_G(mColor),
                  NS_GET_B(mColor), NS_GET_A(mColor));
 }
 #endif
 static void
 RegisterThemeGeometry(nsDisplayListBuilder* aBuilder, nsIFrame* aFrame)
 {
   nsIFrame* displayRoot = nsLayoutUtils::GetDisplayRootFrame(aFrame);
   for (nsIFrame* f = aFrame; f; f = f->GetParent()) {
     // Bail out if we're in a transformed subtree
     if (f->IsTransformed())
       return;
     // Bail out if we're not in the displayRoot's document
     if (!f->GetParent() && f != displayRoot)
       return;
   }
   nsRect borderBox(aFrame->GetOffsetTo(displayRoot), aFrame->GetSize());
   aBuilder->RegisterThemeGeometry(aFrame->StyleDisplay()->mAppearance,
       borderBox.ToNearestPixels(aFrame->PresContext()->AppUnitsPerDevPixel()));
 }
 nsDisplayBackgroundImage::nsDisplayBackgroundImage(nsDisplayListBuilder* aBuilder,
                                                    nsIFrame* aFrame,
                                                    uint32_t aLayer,
                                                    const nsStyleBackground* aBackgroundStyle)
   : nsDisplayImageContainer(aBuilder, aFrame)
   , mBackgroundStyle(aBackgroundStyle)
   , mLayer(aLayer)
 {
   MOZ_COUNT_CTOR(nsDisplayBackgroundImage);
   mBounds = GetBoundsInternal(aBuilder);
 }
 nsDisplayBackgroundImage::~nsDisplayBackgroundImage()
 {
 #ifdef NS_BUILD_REFCNT_LOGGING
   MOZ_COUNT_DTOR(nsDisplayBackgroundImage);
 #endif
 }
 static nsStyleContext* GetBackgroundStyleContext(nsIFrame* aFrame)
 {
   nsStyleContext *sc;
   if (!nsCSSRendering::FindBackground(aFrame, &sc)) {
     // We don't want to bail out if moz-appearance is set on a root
     // node. If it has a parent content node, bail because it's not
     // a root, other wise keep going in order to let the theme stuff
     // draw the background. The canvas really should be drawing the
     // bg, but there's no way to hook that up via css.
     if (!aFrame->StyleDisplay()->mAppearance) {
       return nullptr;
     }
     nsIContent* content = aFrame->GetContent();
     if (!content || content->GetParent()) {
       return nullptr;
     }
     sc = aFrame->StyleContext();
   }
   return sc;
 }
 /*static*/ bool
 nsDisplayBackgroundImage::AppendBackgroundItemsToTop(nsDisplayListBuilder* aBuilder,
                                                      nsIFrame* aFrame,
                                                      nsDisplayList* aList)
 {
   nsStyleContext* bgSC = nullptr;
   const nsStyleBackground* bg = nullptr;
   nsPresContext* presContext = aFrame->PresContext();
   bool isThemed = aFrame->IsThemed();
   if (!isThemed) {
     bgSC = GetBackgroundStyleContext(aFrame);
     if (bgSC) {
       bg = bgSC->StyleBackground();
     }
   }
   bool drawBackgroundColor = false;
   nscolor color;
   if (!nsCSSRendering::IsCanvasFrame(aFrame) && bg) {
     bool drawBackgroundImage;
     color =
       nsCSSRendering::DetermineBackgroundColor(presContext, bgSC, aFrame,
                                                drawBackgroundImage, drawBackgroundColor);
   }
   // An auxiliary list is necessary in case we have background blending; if that
   // is the case, background items need to be wrapped by a blend container to
   // isolate blending to the background
   nsDisplayList bgItemList;
   // Even if we don't actually have a background color to paint, we may still need
   // to create an item for hit testing.
   if ((drawBackgroundColor && color != NS_RGBA(0,0,0,0)) ||
       aBuilder->IsForEventDelivery()) {
     bgItemList.AppendNewToTop(
         new (aBuilder) nsDisplayBackgroundColor(aBuilder, aFrame, bg,
                                                 drawBackgroundColor ? color : NS_RGBA(0, 0, 0, 0)));
   }
   if (isThemed) {
     nsDisplayThemedBackground* bgItem =
       new (aBuilder) nsDisplayThemedBackground(aBuilder, aFrame);
     bgItemList.AppendNewToTop(bgItem);
     aList->AppendToTop(&bgItemList);
     return true;
   }
   if (!bg) {
     aList->AppendToTop(&bgItemList);
     return false;
   }
   bool needBlendContainer = false;
   // Passing bg == nullptr in this macro will result in one iteration with
   // i = 0.
   NS_FOR_VISIBLE_BACKGROUND_LAYERS_BACK_TO_FRONT(i, bg) {
     if (bg->mLayers[i].mImage.IsEmpty()) {
       continue;
     }
     if (bg->mLayers[i].mBlendMode != NS_STYLE_BLEND_NORMAL) {
       needBlendContainer = true;
     }
     nsDisplayBackgroundImage* bgItem =
       new (aBuilder) nsDisplayBackgroundImage(aBuilder, aFrame, i, bg);
     bgItemList.AppendNewToTop(bgItem);
   }
   if (needBlendContainer) {
     bgItemList.AppendNewToTop(
       new (aBuilder) nsDisplayBlendContainer(aBuilder, aFrame, &bgItemList));
   }
   aList->AppendToTop(&bgItemList);
   return false;
 }
 // Check that the rounded border of aFrame, added to aToReferenceFrame,
 // intersects aRect.  Assumes that the unrounded border has already
 // been checked for intersection.
 static bool
 RoundedBorderIntersectsRect(nsIFrame* aFrame,
                             const nsPoint& aFrameToReferenceFrame,
                             const nsRect& aTestRect)
 {
   if (!nsRect(aFrameToReferenceFrame, aFrame->GetSize()).Intersects(aTestRect))
     return false;
   nscoord radii[8];
   return !aFrame->GetBorderRadii(radii) ||
          nsLayoutUtils::RoundedRectIntersectsRect(nsRect(aFrameToReferenceFrame,
                                                   aFrame->GetSize()),
                                                   radii, aTestRect);
 }
 // Returns TRUE if aContainedRect is guaranteed to be contained in
 // the rounded rect defined by aRoundedRect and aRadii. Complex cases are
 // handled conservatively by returning FALSE in some situations where
 // a more thorough analysis could return TRUE.
 //
 // See also RoundedRectIntersectsRect.
 static bool RoundedRectContainsRect(const nsRect& aRoundedRect,
                                     const nscoord aRadii[8],
                                     const nsRect& aContainedRect) {
   nsRegion rgn = nsLayoutUtils::RoundedRectIntersectRect(aRoundedRect, aRadii, aContainedRect);
   return rgn.Contains(aContainedRect);
 }
 bool
 nsDisplayBackgroundImage::IsSingleFixedPositionImage(nsDisplayListBuilder* aBuilder,
                                                      const nsRect& aClipRect,
                                                      gfxRect* aDestRect)
 {
   if (!mBackgroundStyle)
     return false;
   if (mBackgroundStyle->mLayers.Length() != 1)
     return false;
   nsPresContext* presContext = mFrame->PresContext();
   uint32_t flags = aBuilder->GetBackgroundPaintFlags();
   nsRect borderArea = nsRect(ToReferenceFrame(), mFrame->GetSize());
   const nsStyleBackground::Layer &layer = mBackgroundStyle->mLayers[mLayer];
   if (layer.mAttachment != NS_STYLE_BG_ATTACHMENT_FIXED)
     return false;
   nsBackgroundLayerState state =
     nsCSSRendering::PrepareBackgroundLayer(presContext,
                                            mFrame,
                                            flags,
                                            borderArea,
                                            aClipRect,
                                            *mBackgroundStyle,
                                            layer);
   nsImageRenderer* imageRenderer = &state.mImageRenderer;
   // We only care about images here, not gradients.
   if (!imageRenderer->IsRasterImage())
     return false;
   int32_t appUnitsPerDevPixel = presContext->AppUnitsPerDevPixel();
   *aDestRect = nsLayoutUtils::RectToGfxRect(state.mFillArea, appUnitsPerDevPixel);
   return true;
 }
 bool
 nsDisplayBackgroundImage::TryOptimizeToImageLayer(LayerManager* aManager,
                                                   nsDisplayListBuilder* aBuilder)
 {
   if (!mBackgroundStyle)
     return false;
   nsPresContext* presContext = mFrame->PresContext();
   uint32_t flags = aBuilder->GetBackgroundPaintFlags();
   nsRect borderArea = nsRect(ToReferenceFrame(), mFrame->GetSize());
   const nsStyleBackground::Layer &layer = mBackgroundStyle->mLayers[mLayer];
   if (layer.mClip != NS_STYLE_BG_CLIP_BORDER) {
     return false;
   }
   nscoord radii[8];
   if (mFrame->GetBorderRadii(radii)) {
     return false;
   }
   nsBackgroundLayerState state =
     nsCSSRendering::PrepareBackgroundLayer(presContext,
                                            mFrame,
                                            flags,
                                            borderArea,
                                            borderArea,
                                            *mBackgroundStyle,
                                            layer);
   nsImageRenderer* imageRenderer = &state.mImageRenderer;
   // We only care about images here, not gradients.
   if (!imageRenderer->IsRasterImage())
     return false;
   nsRefPtr<ImageContainer> imageContainer = imageRenderer->GetContainer(aManager);
   // Image is not ready to be made into a layer yet
   if (!imageContainer)
     return false;
   // We currently can't handle tiled or partial backgrounds.
   if (!state.mDestArea.IsEqualEdges(state.mFillArea)) {
     return false;
   }
   // XXX Ignoring state.mAnchor. ImageLayer drawing snaps mDestArea edges to
   // layer pixel boundaries. This should be OK for now.
   int32_t appUnitsPerDevPixel = presContext->AppUnitsPerDevPixel();
   mDestRect = nsLayoutUtils::RectToGfxRect(state.mDestArea, appUnitsPerDevPixel);
   mImageContainer = imageContainer;
   // Ok, we can turn this into a layer if needed.
   return true;
 }
 already_AddRefed<ImageContainer>
 nsDisplayBackgroundImage::GetContainer(LayerManager* aManager,
                                        nsDisplayListBuilder *aBuilder)
 {
   if (!TryOptimizeToImageLayer(aManager, aBuilder)) {
     return nullptr;
   }
   nsRefPtr<ImageContainer> container = mImageContainer;
   return container.forget();
 }
 LayerState
 nsDisplayBackgroundImage::GetLayerState(nsDisplayListBuilder* aBuilder,
                                         LayerManager* aManager,
                                         const ContainerLayerParameters& aParameters)
 {
   bool animated = false;
   if (mBackgroundStyle) {
     const nsStyleBackground::Layer &layer = mBackgroundStyle->mLayers[mLayer];
     const nsStyleImage* image = &layer.mImage;
     if (image->GetType() == eStyleImageType_Image) {
       imgIRequest* imgreq = image->GetImageData();
       nsCOMPtr<imgIContainer> image;
       if (NS_SUCCEEDED(imgreq->GetImage(getter_AddRefs(image))) && image) {
         if (NS_FAILED(image->GetAnimated(&animated))) {
           animated = false;
         }
       }
     }
   }
   if (!animated ||
       !nsLayoutUtils::AnimatedImageLayersEnabled()) {
     if (!aManager->IsCompositingCheap() ||
         !nsLayoutUtils::GPUImageScalingEnabled()) {
       return LAYER_NONE;
     }
   }
   if (!TryOptimizeToImageLayer(aManager, aBuilder)) {
     return LAYER_NONE;
   }
   if (!animated) {
     mozilla::gfx::IntSize imageSize = mImageContainer->GetCurrentSize();
     NS_ASSERTION(imageSize.width != 0 && imageSize.height != 0, "Invalid image size!");
     gfxRect destRect = mDestRect;
     destRect.width *= aParameters.mXScale;
     destRect.height *= aParameters.mYScale;
     // Calculate the scaling factor for the frame.
     gfxSize scale = gfxSize(destRect.width / imageSize.width, destRect.height / imageSize.height);
     // If we are not scaling at all, no point in separating this into a layer.
     if (scale.width == 1.0f && scale.height == 1.0f) {
       return LAYER_NONE;
     }
     // If the target size is pretty small, no point in using a layer.
     if (destRect.width * destRect.height < 64 * 64) {
       return LAYER_NONE;
     }
   }
   return LAYER_ACTIVE;
 }
 already_AddRefed<Layer>
 nsDisplayBackgroundImage::BuildLayer(nsDisplayListBuilder* aBuilder,
                                      LayerManager* aManager,
                                      const ContainerLayerParameters& aParameters)
 {
   nsRefPtr<ImageLayer> layer = static_cast<ImageLayer*>
     (aManager->GetLayerBuilder()->GetLeafLayerFor(aBuilder, this));
   if (!layer) {
     layer = aManager->CreateImageLayer();
     if (!layer)
       return nullptr;
   }
   layer->SetContainer(mImageContainer);
   ConfigureLayer(layer, aParameters.mOffset);
   return layer.forget();
 }
 void
 nsDisplayBackgroundImage::ConfigureLayer(ImageLayer* aLayer, const nsIntPoint& aOffset)
 {
   aLayer->SetFilter(nsLayoutUtils::GetGraphicsFilterForFrame(mFrame));
   mozilla::gfx::IntSize imageSize = mImageContainer->GetCurrentSize();
   NS_ASSERTION(imageSize.width != 0 && imageSize.height != 0, "Invalid image size!");
   gfxPoint p = mDestRect.TopLeft() + aOffset;
   gfx::Matrix transform;
   transform.Translate(p.x, p.y);
   transform.Scale(mDestRect.width/imageSize.width,
                   mDestRect.height/imageSize.height);
   aLayer->SetBaseTransform(gfx::Matrix4x4::From2D(transform));
   aLayer->SetVisibleRegion(nsIntRect(0, 0, imageSize.width, imageSize.height));
 }
 void
 nsDisplayBackgroundImage::HitTest(nsDisplayListBuilder* aBuilder,
                                   const nsRect& aRect,
                                   HitTestState* aState,
                                   nsTArray<nsIFrame*> *aOutFrames)
 {
   if (RoundedBorderIntersectsRect(mFrame, ToReferenceFrame(), aRect)) {
     aOutFrames->AppendElement(mFrame);
   }
 }
 bool
 nsDisplayBackgroundImage::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                             nsRegion* aVisibleRegion,
                                             const nsRect& aAllowVisibleRegionExpansion)
 {
   if (!nsDisplayItem::ComputeVisibility(aBuilder, aVisibleRegion,
                                         aAllowVisibleRegionExpansion)) {
     return false;
   }
   // Return false if the background was propagated away from this
   // frame. We don't want this display item to show up and confuse
   // anything.
   return mBackgroundStyle;
 }
 /* static */ nsRegion
 nsDisplayBackgroundImage::GetInsideClipRegion(nsDisplayItem* aItem,
                                               nsPresContext* aPresContext,
                                               uint8_t aClip, const nsRect& aRect,
                                               bool* aSnap)
 {
   nsRegion result;
   if (aRect.IsEmpty())
     return result;
   nsIFrame *frame = aItem->Frame();
   nscoord radii[8];
   nsRect clipRect;
   bool haveRadii;
   switch (aClip) {
   case NS_STYLE_BG_CLIP_BORDER:
     haveRadii = frame->GetBorderRadii(radii);
     clipRect = nsRect(aItem->ToReferenceFrame(), frame->GetSize());
     break;
   case NS_STYLE_BG_CLIP_PADDING:
     haveRadii = frame->GetPaddingBoxBorderRadii(radii);
     clipRect = frame->GetPaddingRect() - frame->GetPosition() + aItem->ToReferenceFrame();
     break;
   case NS_STYLE_BG_CLIP_CONTENT:
     haveRadii = frame->GetContentBoxBorderRadii(radii);
     clipRect = frame->GetContentRect() - frame->GetPosition() + aItem->ToReferenceFrame();
     break;
   default:
     NS_NOTREACHED("Unknown clip type");
     return result;
   }
   if (haveRadii) {
     *aSnap = false;
     result = nsLayoutUtils::RoundedRectIntersectRect(clipRect, radii, aRect);
   } else {
     result = clipRect.Intersect(aRect);
   }
   return result;
 }
 nsRegion
 nsDisplayBackgroundImage::GetOpaqueRegion(nsDisplayListBuilder* aBuilder,
                                           bool* aSnap) {
   nsRegion result;
   *aSnap = false;
   if (!mBackgroundStyle)
     return result;
   *aSnap = true;
   // For policies other than EACH_BOX, don't try to optimize here, since
   // this could easily lead to O(N^2) behavior inside InlineBackgroundData,
   // which expects frames to be sent to it in content order, not reverse
   // content order which we'll produce here.
   // Of course, if there's only one frame in the flow, it doesn't matter.
   if (mBackgroundStyle->mBackgroundInlinePolicy == NS_STYLE_BG_INLINE_POLICY_EACH_BOX ||
       (!mFrame->GetPrevContinuation() && !mFrame->GetNextContinuation())) {
     const nsStyleBackground::Layer& layer = mBackgroundStyle->mLayers[mLayer];
     if (layer.mImage.IsOpaque() && layer.mBlendMode == NS_STYLE_BLEND_NORMAL) {
       nsPresContext* presContext = mFrame->PresContext();
       result = GetInsideClipRegion(this, presContext, layer.mClip, mBounds, aSnap);
     }
   }
   return result;
 }
 bool
 nsDisplayBackgroundImage::IsUniform(nsDisplayListBuilder* aBuilder, nscolor* aColor) {
   if (!mBackgroundStyle) {
     *aColor = NS_RGBA(0,0,0,0);
     return true;
   }
   return false;
 }
 bool
 nsDisplayBackgroundImage::IsVaryingRelativeToMovingFrame(nsDisplayListBuilder* aBuilder,
                                                          nsIFrame* aFrame)
 {
   if (!mBackgroundStyle)
     return false;
   if (!mBackgroundStyle->HasFixedBackground())
     return false;
   // If aFrame is mFrame or an ancestor in this document, and aFrame is
   // not the viewport frame, then moving aFrame will move mFrame
   // relative to the viewport, so our fixed-pos background will change.
   return aFrame->GetParent() &&
     (aFrame == mFrame ||
      nsLayoutUtils::IsProperAncestorFrame(aFrame, mFrame));
 }
 nsRect
 nsDisplayBackgroundImage::GetPositioningArea()
 {
   if (!mBackgroundStyle) {
     return nsRect();
   }
   nsIFrame* attachedToFrame;
   return nsCSSRendering::ComputeBackgroundPositioningArea(
       mFrame->PresContext(), mFrame,
       nsRect(ToReferenceFrame(), mFrame->GetSize()),
       *mBackgroundStyle, mBackgroundStyle->mLayers[mLayer],
       &attachedToFrame) + ToReferenceFrame();
 }
 bool
 nsDisplayBackgroundImage::RenderingMightDependOnPositioningAreaSizeChange()
 {
   if (!mBackgroundStyle)
     return false;
   nscoord radii[8];
   if (mFrame->GetBorderRadii(radii)) {
     // A change in the size of the positioning area might change the position
     // of the rounded corners.
     return true;
   }
   const nsStyleBackground::Layer &layer = mBackgroundStyle->mLayers[mLayer];
   if (layer.RenderingMightDependOnPositioningAreaSizeChange()) {
     return true;
   }
   return false;
 }
 static void CheckForBorderItem(nsDisplayItem *aItem, uint32_t& aFlags)
 {
   nsDisplayItem* nextItem = aItem->GetAbove();
   while (nextItem && nextItem->GetType() == nsDisplayItem::TYPE_BACKGROUND) {
     nextItem = nextItem->GetAbove();
   }
   if (nextItem &&
       nextItem->Frame() == aItem->Frame() &&
       nextItem->GetType() == nsDisplayItem::TYPE_BORDER) {
     aFlags |= nsCSSRendering::PAINTBG_WILL_PAINT_BORDER;
   }
 }
 void
 nsDisplayBackgroundImage::Paint(nsDisplayListBuilder* aBuilder,
                                 nsRenderingContext* aCtx) {
   PaintInternal(aBuilder, aCtx, mVisibleRect, nullptr);
 }
 void
 nsDisplayBackgroundImage::PaintInternal(nsDisplayListBuilder* aBuilder,
                                         nsRenderingContext* aCtx, const nsRect& aBounds,
                                         nsRect* aClipRect) {
   nsPoint offset = ToReferenceFrame();
   uint32_t flags = aBuilder->GetBackgroundPaintFlags();
   CheckForBorderItem(this, flags);
   nsCSSRendering::PaintBackground(mFrame->PresContext(), *aCtx, mFrame,
                                   aBounds,
                                   nsRect(offset, mFrame->GetSize()),
                                   flags, aClipRect, mLayer);
 }
 void nsDisplayBackgroundImage::ComputeInvalidationRegion(nsDisplayListBuilder* aBuilder,
                                                          const nsDisplayItemGeometry* aGeometry,
                                                          nsRegion* aInvalidRegion)
 {
   if (!mBackgroundStyle) {
     return;
   }
   const nsDisplayBackgroundGeometry* geometry = static_cast<const nsDisplayBackgroundGeometry*>(aGeometry);
   bool snap;
   nsRect bounds = GetBounds(aBuilder, &snap);
   nsRect positioningArea = GetPositioningArea();
   if (positioningArea.TopLeft() != geometry->mPositioningArea.TopLeft() ||
       (positioningArea.Size() != geometry->mPositioningArea.Size() &&
        RenderingMightDependOnPositioningAreaSizeChange())) {
     // Positioning area changed in a way that could cause everything to change,
     // so invalidate everything (both old and new painting areas).
     aInvalidRegion->Or(bounds, geometry->mBounds);
     if (positioningArea.Size() != geometry->mPositioningArea.Size()) {
       NotifyRenderingChanged();
     }
     return;
   }
   if (aBuilder->ShouldSyncDecodeImages()) {
     if (mBackgroundStyle &&
         !nsCSSRendering::IsBackgroundImageDecodedForStyleContextAndLayer(mBackgroundStyle, mLayer)) {
       aInvalidRegion->Or(*aInvalidRegion, bounds);
       NotifyRenderingChanged();
     }
   }
   if (!bounds.IsEqualInterior(geometry->mBounds)) {
     // Positioning area is unchanged, so invalidate just the change in the
     // painting area.
     aInvalidRegion->Xor(bounds, geometry->mBounds);
     NotifyRenderingChanged();
   }
 }
 nsRect
 nsDisplayBackgroundImage::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap) {
   *aSnap = true;
   return mBounds;
 }
 nsRect
 nsDisplayBackgroundImage::GetBoundsInternal(nsDisplayListBuilder* aBuilder) {
   nsPresContext* presContext = mFrame->PresContext();
   if (!mBackgroundStyle) {
     return nsRect();
   }
   nsRect borderBox = nsRect(ToReferenceFrame(), mFrame->GetSize());
   nsRect clipRect = borderBox;
   if (mFrame->GetType() == nsGkAtoms::canvasFrame) {
     nsCanvasFrame* frame = static_cast<nsCanvasFrame*>(mFrame);
     clipRect = frame->CanvasArea() + ToReferenceFrame();
   }
   const nsStyleBackground::Layer& layer = mBackgroundStyle->mLayers[mLayer];
   return nsCSSRendering::GetBackgroundLayerRect(presContext, mFrame,
                                                 borderBox, clipRect,
                                                 *mBackgroundStyle, layer,
                                                 aBuilder->GetBackgroundPaintFlags());
 }
 uint32_t
 nsDisplayBackgroundImage::GetPerFrameKey()
 {
   return (mLayer << nsDisplayItem::TYPE_BITS) |
     nsDisplayItem::GetPerFrameKey();
 }
 nsDisplayThemedBackground::nsDisplayThemedBackground(nsDisplayListBuilder* aBuilder,
                                                      nsIFrame* aFrame)
   : nsDisplayItem(aBuilder, aFrame)
 {
   MOZ_COUNT_CTOR(nsDisplayThemedBackground);
   const nsStyleDisplay* disp = mFrame->StyleDisplay();
   mAppearance = disp->mAppearance;
   mFrame->IsThemed(disp, &mThemeTransparency);
   // Perform necessary RegisterThemeGeometry
   switch (disp->mAppearance) {
     case NS_THEME_MOZ_MAC_UNIFIED_TOOLBAR:
     case NS_THEME_TOOLBAR:
     case NS_THEME_WINDOW_TITLEBAR:
     case NS_THEME_WINDOW_BUTTON_BOX:
     case NS_THEME_MOZ_MAC_FULLSCREEN_BUTTON:
     case NS_THEME_WINDOW_BUTTON_BOX_MAXIMIZED:
       RegisterThemeGeometry(aBuilder, aFrame);
       break;
     case NS_THEME_WIN_BORDERLESS_GLASS:
     case NS_THEME_WIN_GLASS:
       aBuilder->SetGlassDisplayItem(this);
       break;
   }
   mBounds = GetBoundsInternal();
 }
 nsDisplayThemedBackground::~nsDisplayThemedBackground()
 {
 #ifdef NS_BUILD_REFCNT_LOGGING
   MOZ_COUNT_DTOR(nsDisplayThemedBackground);
 #endif
 }
 #ifdef MOZ_DUMP_PAINTING
 void
 nsDisplayThemedBackground::WriteDebugInfo(nsACString& aTo)
 {
   aTo += nsPrintfCString(" (themed, appearance:%d)", mAppearance);
 }
 #endif
 void
 nsDisplayThemedBackground::HitTest(nsDisplayListBuilder* aBuilder,
                                   const nsRect& aRect,
                                   HitTestState* aState,
                                   nsTArray<nsIFrame*> *aOutFrames)
 {
   // Assume that any point in our border rect is a hit.
   if (nsRect(ToReferenceFrame(), mFrame->GetSize()).Intersects(aRect)) {
     aOutFrames->AppendElement(mFrame);
   }
 }
 nsRegion
 nsDisplayThemedBackground::GetOpaqueRegion(nsDisplayListBuilder* aBuilder,
                                            bool* aSnap) {
   nsRegion result;
   *aSnap = false;
   if (mThemeTransparency == nsITheme::eOpaque) {
     result = nsRect(ToReferenceFrame(), mFrame->GetSize());
   }
   return result;
 }
 bool
 nsDisplayThemedBackground::IsUniform(nsDisplayListBuilder* aBuilder, nscolor* aColor) {
   if (mAppearance == NS_THEME_WIN_BORDERLESS_GLASS ||
       mAppearance == NS_THEME_WIN_GLASS) {
     *aColor = NS_RGBA(0,0,0,0);
     return true;
   }
   return false;
 }
 nsRect
 nsDisplayThemedBackground::GetPositioningArea()
 {
   return nsRect(ToReferenceFrame(), mFrame->GetSize());
 }
 void
 nsDisplayThemedBackground::Paint(nsDisplayListBuilder* aBuilder,
                                  nsRenderingContext* aCtx)
 {
   PaintInternal(aBuilder, aCtx, mVisibleRect, nullptr);
 }
 void
 nsDisplayThemedBackground::PaintInternal(nsDisplayListBuilder* aBuilder,
                                          nsRenderingContext* aCtx, const nsRect& aBounds,
                                          nsRect* aClipRect)
 {
   // XXXzw this ignores aClipRect.
   nsPresContext* presContext = mFrame->PresContext();
   nsITheme *theme = presContext->GetTheme();
   nsRect borderArea(ToReferenceFrame(), mFrame->GetSize());
   nsRect drawing(borderArea);
   theme->GetWidgetOverflow(presContext->DeviceContext(), mFrame, mAppearance,
                            &drawing);
   drawing.IntersectRect(drawing, aBounds);
   theme->DrawWidgetBackground(aCtx, mFrame, mAppearance, borderArea, drawing);
 }
 bool nsDisplayThemedBackground::IsWindowActive()
 {
   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 nsDisplayThemedBackgroundGeometry* geometry = static_cast<const nsDisplayThemedBackgroundGeometry*>(aGeometry);
   bool snap;
   nsRect bounds = GetBounds(aBuilder, &snap);
   nsRect positioningArea = GetPositioningArea();
   if (!positioningArea.IsEqualInterior(geometry->mPositioningArea)) {
     // Invalidate everything (both old and new painting areas).
     aInvalidRegion->Or(bounds, geometry->mBounds);
     return;
   }
   if (!bounds.IsEqualInterior(geometry->mBounds)) {
     // Positioning area is unchanged, so invalidate just the change in the
     // painting area.
     aInvalidRegion->Xor(bounds, geometry->mBounds);
   }
   nsITheme* theme = mFrame->PresContext()->GetTheme();
   if (theme->WidgetAppearanceDependsOnWindowFocus(mAppearance) &&
       IsWindowActive() != geometry->mWindowIsActive) {
     aInvalidRegion->Or(*aInvalidRegion, bounds);
   }
 }
 nsRect
 nsDisplayThemedBackground::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap) {
   *aSnap = true;
   return mBounds;
 }
 nsRect
 nsDisplayThemedBackground::GetBoundsInternal() {
   nsPresContext* presContext = mFrame->PresContext();
   nsRect r(nsPoint(0,0), mFrame->GetSize());
   presContext->GetTheme()->
       GetWidgetOverflow(presContext->DeviceContext(), mFrame,
                         mFrame->StyleDisplay()->mAppearance, &r);
 #ifdef XP_MACOSX
   // Bug 748219
   r.Inflate(mFrame->PresContext()->AppUnitsPerDevPixel());
 #endif
   return r + ToReferenceFrame();
 }
 void
 nsDisplayBackgroundColor::Paint(nsDisplayListBuilder* aBuilder,
                                 nsRenderingContext* aCtx)
 {
   if (mColor == NS_RGBA(0, 0, 0, 0)) {
     return;
   }
   nsPoint offset = ToReferenceFrame();
   uint32_t flags = aBuilder->GetBackgroundPaintFlags();
   CheckForBorderItem(this, flags);
   nsCSSRendering::PaintBackgroundColor(mFrame->PresContext(), *aCtx, mFrame,
                                        mVisibleRect,
                                        nsRect(offset, mFrame->GetSize()),
                                        flags);
 }
 nsRegion
 nsDisplayBackgroundColor::GetOpaqueRegion(nsDisplayListBuilder* aBuilder,
                                           bool* aSnap)
 {
   if (NS_GET_A(mColor) != 255) {
     return nsRegion();
   }
   if (!mBackgroundStyle)
     return nsRegion();
   *aSnap = true;
   const nsStyleBackground::Layer& bottomLayer = mBackgroundStyle->BottomLayer();
   nsRect borderBox = nsRect(ToReferenceFrame(), mFrame->GetSize());
   nsPresContext* presContext = mFrame->PresContext();
   return nsDisplayBackgroundImage::GetInsideClipRegion(this, presContext, bottomLayer.mClip, borderBox, aSnap);
 }
 bool
 nsDisplayBackgroundColor::IsUniform(nsDisplayListBuilder* aBuilder, nscolor* aColor)
 {
   *aColor = mColor;
   if (!mBackgroundStyle)
     return true;
   return (!nsLayoutUtils::HasNonZeroCorner(mFrame->StyleBorder()->mBorderRadius) &&
           mBackgroundStyle->BottomLayer().mClip == NS_STYLE_BG_CLIP_BORDER);
 }
 void
 nsDisplayBackgroundColor::HitTest(nsDisplayListBuilder* aBuilder,
                                   const nsRect& aRect,
                                   HitTestState* aState,
                                   nsTArray<nsIFrame*> *aOutFrames)
 {
   if (!RoundedBorderIntersectsRect(mFrame, ToReferenceFrame(), aRect)) {
     // aRect doesn't intersect our border-radius curve.
     return;
   }
   aOutFrames->AppendElement(mFrame);
 }
 #ifdef MOZ_DUMP_PAINTING
 void
 nsDisplayBackgroundColor::WriteDebugInfo(nsACString& aTo)
 {
   aTo += nsPrintfCString(" (rgba %d,%d,%d,%d)",
           NS_GET_R(mColor), NS_GET_G(mColor),
           NS_GET_B(mColor), NS_GET_A(mColor));
 }
 #endif
 nsRect
 nsDisplayOutline::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap) {
   *aSnap = false;
   return mFrame->GetVisualOverflowRectRelativeToSelf() + ToReferenceFrame();
 }
 void
 nsDisplayOutline::Paint(nsDisplayListBuilder* aBuilder,
                         nsRenderingContext* aCtx) {
   // TODO join outlines together
   nsPoint offset = ToReferenceFrame();
   nsCSSRendering::PaintOutline(mFrame->PresContext(), *aCtx, mFrame,
                                mVisibleRect,
                                nsRect(offset, mFrame->GetSize()),
                                mFrame->StyleContext());
 }
 bool
 nsDisplayOutline::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                     nsRegion* aVisibleRegion,
                                     const nsRect& aAllowVisibleRegionExpansion) {
   if (!nsDisplayItem::ComputeVisibility(aBuilder, aVisibleRegion,
                                         aAllowVisibleRegionExpansion)) {
     return false;
   }
   const nsStyleOutline* outline = mFrame->StyleOutline();
   nsRect borderBox(ToReferenceFrame(), mFrame->GetSize());
   if (borderBox.Contains(aVisibleRegion->GetBounds()) &&
       !nsLayoutUtils::HasNonZeroCorner(outline->mOutlineRadius)) {
     if (outline->mOutlineOffset >= 0) {
       // the visible region is entirely inside the border-rect, and the outline
       // isn't rendered inside the border-rect, so the outline is not visible
       return false;
     }
   }
   return true;
 }
 void
 nsDisplayEventReceiver::HitTest(nsDisplayListBuilder* aBuilder,
                                 const nsRect& aRect,
                                 HitTestState* aState,
                                 nsTArray<nsIFrame*> *aOutFrames)
 {
   if (!RoundedBorderIntersectsRect(mFrame, ToReferenceFrame(), aRect)) {
     // aRect doesn't intersect our border-radius curve.
     return;
   }
   aOutFrames->AppendElement(mFrame);
 }
 void
 nsDisplayLayerEventRegions::AddFrame(nsDisplayListBuilder* aBuilder,
                                      nsIFrame* aFrame)
 {
   NS_ASSERTION(aBuilder->FindReferenceFrameFor(aFrame) == aBuilder->FindReferenceFrameFor(mFrame),
                "Reference frame mismatch");
   uint8_t pointerEvents = aFrame->StyleVisibility()->mPointerEvents;
   if (pointerEvents == NS_STYLE_POINTER_EVENTS_NONE) {
     return;
   }
   // XXX handle other pointerEvents values for SVG
   // XXX Do something clever here for the common case where the border box
   // is obviously entirely inside mHitRegion.
   nsRect borderBox(aBuilder->ToReferenceFrame(aFrame), aFrame->GetSize());
   const DisplayItemClip* clip = aBuilder->ClipState().GetCurrentCombinedClip(aBuilder);
   bool borderBoxHasRoundedCorners =
     nsLayoutUtils::HasNonZeroCorner(aFrame->StyleBorder()->mBorderRadius);
   if (clip) {
     borderBox = clip->ApplyNonRoundedIntersection(borderBox);
     if (clip->GetRoundedRectCount() > 0) {
       borderBoxHasRoundedCorners = true;
     }
   }
   if (borderBoxHasRoundedCorners ||
       (aFrame->GetStateBits() & NS_FRAME_SVG_LAYOUT)) {
     mMaybeHitRegion.Or(mMaybeHitRegion, borderBox);
   } else {
     mHitRegion.Or(mHitRegion, borderBox);
   }
   if (aBuilder->GetAncestorHasTouchEventHandler()) {
     mDispatchToContentHitRegion.Or(mDispatchToContentHitRegion, borderBox);
   }
 }
 void
 nsDisplayCaret::Paint(nsDisplayListBuilder* aBuilder,
                       nsRenderingContext* aCtx) {
   // Note: Because we exist, we know that the caret is visible, so we don't
   // need to check for the caret's visibility.
   mCaret->PaintCaret(aBuilder, aCtx, mFrame, ToReferenceFrame());
 }
 bool
 nsDisplayBorder::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                    nsRegion* aVisibleRegion,
                                    const nsRect& aAllowVisibleRegionExpansion) {
   if (!nsDisplayItem::ComputeVisibility(aBuilder, aVisibleRegion,
                                         aAllowVisibleRegionExpansion)) {
     return false;
   }
   nsRect paddingRect = mFrame->GetPaddingRect() - mFrame->GetPosition() +
     ToReferenceFrame();
   const nsStyleBorder *styleBorder;
   if (paddingRect.Contains(aVisibleRegion->GetBounds()) &&
       !(styleBorder = mFrame->StyleBorder())->IsBorderImageLoaded() &&
       !nsLayoutUtils::HasNonZeroCorner(styleBorder->mBorderRadius)) {
     // the visible region is entirely inside the content rect, and no part
     // of the border is rendered inside the content rect, so we are not
     // visible
     // Skip this if there's a border-image (which draws a background
     // too) or if there is a border-radius (which makes the border draw
     // further in).
     return false;
   }
   return true;
 }
 nsDisplayItemGeometry*
 nsDisplayBorder::AllocateGeometry(nsDisplayListBuilder* aBuilder)
 {
   return new nsDisplayBorderGeometry(this, aBuilder);
 }
 void
 nsDisplayBorder::ComputeInvalidationRegion(nsDisplayListBuilder* aBuilder,
                                            const nsDisplayItemGeometry* aGeometry,
                                            nsRegion* aInvalidRegion)
 {
   const nsDisplayBorderGeometry* geometry = static_cast<const nsDisplayBorderGeometry*>(aGeometry);
   bool snap;
   if (!geometry->mBounds.IsEqualInterior(GetBounds(aBuilder, &snap)) ||
       !geometry->mContentRect.IsEqualInterior(GetContentRect())) {
     // We can probably get away with only invalidating the difference
     // between the border and padding rects, but the XUL ui at least
     // is apparently painting a background with this?
     aInvalidRegion->Or(GetBounds(aBuilder, &snap), geometry->mBounds);
   }
 }
 void
 nsDisplayBorder::Paint(nsDisplayListBuilder* aBuilder,
                        nsRenderingContext* aCtx) {
   nsPoint offset = ToReferenceFrame();
   nsCSSRendering::PaintBorder(mFrame->PresContext(), *aCtx, mFrame,
                               mVisibleRect,
                               nsRect(offset, mFrame->GetSize()),
                               mFrame->StyleContext(),
                               mFrame->GetSkipSides());
 }
 nsRect
 nsDisplayBorder::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap)
 {
   *aSnap = true;
   return CalculateBounds(*mFrame->StyleBorder());
 }
 nsRect
 nsDisplayBorder::CalculateBounds(const nsStyleBorder& aStyleBorder)
 {
   nsRect borderBounds(ToReferenceFrame(), mFrame->GetSize());
   if (aStyleBorder.IsBorderImageLoaded()) {
     borderBounds.Inflate(aStyleBorder.GetImageOutset());
     return borderBounds;
   } else {
     nsMargin border = aStyleBorder.GetComputedBorder();
     nsRect result;
     if (border.top > 0) {
       result = nsRect(borderBounds.X(), borderBounds.Y(), borderBounds.Width(), border.top);
     }
     if (border.right > 0) {
       result.UnionRect(result, nsRect(borderBounds.XMost() - border.right, borderBounds.Y(), border.right, borderBounds.Height()));
     }
     if (border.bottom > 0) {
       result.UnionRect(result, nsRect(borderBounds.X(), borderBounds.YMost() - border.bottom, borderBounds.Width(), border.bottom));
     }
     if (border.left > 0) {
       result.UnionRect(result, nsRect(borderBounds.X(), borderBounds.Y(), border.left, borderBounds.Height()));
     }
     return result;
   }
 }
 // Given a region, compute a conservative approximation to it as a list
 // of rectangles that aren't vertically adjacent (i.e., vertically
 // adjacent or overlapping rectangles are combined).
 // Right now this is only approximate, some vertically overlapping rectangles
 // aren't guaranteed to be combined.
 static void
 ComputeDisjointRectangles(const nsRegion& aRegion,
                           nsTArray<nsRect>* aRects) {
   nscoord accumulationMargin = nsPresContext::CSSPixelsToAppUnits(25);
   nsRect accumulated;
   nsRegionRectIterator iter(aRegion);
   while (true) {
     const nsRect* r = iter.Next();
     if (r && !accumulated.IsEmpty() &&
         accumulated.YMost() >= r->y - accumulationMargin) {
       accumulated.UnionRect(accumulated, *r);
       continue;
     }
     if (!accumulated.IsEmpty()) {
       aRects->AppendElement(accumulated);
       accumulated.SetEmpty();
     }
     if (!r)
       break;
     accumulated = *r;
   }
 }
 void
 nsDisplayBoxShadowOuter::Paint(nsDisplayListBuilder* aBuilder,
                                nsRenderingContext* aCtx) {
   nsPoint offset = ToReferenceFrame();
   nsRect borderRect = mFrame->VisualBorderRectRelativeToSelf() + offset;
   nsPresContext* presContext = mFrame->PresContext();
   nsAutoTArray<nsRect,10> rects;
   ComputeDisjointRectangles(mVisibleRegion, &rects);
   PROFILER_LABEL("nsDisplayBoxShadowOuter", "Paint");
   for (uint32_t i = 0; i < rects.Length(); ++i) {
     aCtx->PushState();
     aCtx->IntersectClip(rects[i]);
     nsCSSRendering::PaintBoxShadowOuter(presContext, *aCtx, mFrame,
                                         borderRect, rects[i], mOpacity);
     aCtx->PopState();
   }
 }
 nsRect
 nsDisplayBoxShadowOuter::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap) {
   *aSnap = false;
   return mBounds;
 }
 nsRect
 nsDisplayBoxShadowOuter::GetBoundsInternal() {
   return nsLayoutUtils::GetBoxShadowRectForFrame(mFrame, mFrame->GetSize()) +
          ToReferenceFrame();
 }
 bool
 nsDisplayBoxShadowOuter::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                            nsRegion* aVisibleRegion,
                                            const nsRect& aAllowVisibleRegionExpansion) {
   if (!nsDisplayItem::ComputeVisibility(aBuilder, aVisibleRegion,
                                         aAllowVisibleRegionExpansion)) {
     return false;
   }
   // Store the actual visible region
   mVisibleRegion.And(*aVisibleRegion, mVisibleRect);
   nsPoint origin = ToReferenceFrame();
   nsRect visibleBounds = aVisibleRegion->GetBounds();
   nsRect frameRect(origin, mFrame->GetSize());
   if (!frameRect.Contains(visibleBounds))
     return true;
   // the visible region is entirely inside the border-rect, and box shadows
   // never render within the border-rect (unless there's a border radius).
   nscoord twipsRadii[8];
   bool hasBorderRadii = mFrame->GetBorderRadii(twipsRadii);
   if (!hasBorderRadii)
     return false;
   return !RoundedRectContainsRect(frameRect, twipsRadii, visibleBounds);
 }
 void
 nsDisplayBoxShadowOuter::ComputeInvalidationRegion(nsDisplayListBuilder* aBuilder,
                                                    const nsDisplayItemGeometry* aGeometry,
                                                    nsRegion* aInvalidRegion)
 {
   const nsDisplayItemGenericGeometry* geometry =
     static_cast<const nsDisplayItemGenericGeometry*>(aGeometry);
   bool snap;
   if (!geometry->mBounds.IsEqualInterior(GetBounds(aBuilder, &snap)) ||
       !geometry->mBorderRect.IsEqualInterior(GetBorderRect())) {
     nsRegion oldShadow, newShadow;
     nscoord dontCare[8];
     bool hasBorderRadius = mFrame->GetBorderRadii(dontCare);
     if (hasBorderRadius) {
       // If we have rounded corners then we need to invalidate the frame area
       // too since we paint into it.
       oldShadow = geometry->mBounds;
       newShadow = GetBounds(aBuilder, &snap);
     } else {
       oldShadow = oldShadow.Sub(geometry->mBounds, geometry->mBorderRect);
       newShadow = newShadow.Sub(GetBounds(aBuilder, &snap), GetBorderRect());
     }
     aInvalidRegion->Or(oldShadow, newShadow);
   }
 }
 void
 nsDisplayBoxShadowInner::Paint(nsDisplayListBuilder* aBuilder,
                                nsRenderingContext* aCtx) {
   nsPoint offset = ToReferenceFrame();
   nsRect borderRect = nsRect(offset, mFrame->GetSize());
   nsPresContext* presContext = mFrame->PresContext();
   nsAutoTArray<nsRect,10> rects;
   ComputeDisjointRectangles(mVisibleRegion, &rects);
   PROFILER_LABEL("nsDisplayBoxShadowInner", "Paint");
   for (uint32_t i = 0; i < rects.Length(); ++i) {
     aCtx->PushState();
     aCtx->IntersectClip(rects[i]);
     nsCSSRendering::PaintBoxShadowInner(presContext, *aCtx, mFrame,
                                         borderRect, rects[i]);
     aCtx->PopState();
   }
 }
 bool
 nsDisplayBoxShadowInner::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                            nsRegion* aVisibleRegion,
                                            const nsRect& aAllowVisibleRegionExpansion) {
   if (!nsDisplayItem::ComputeVisibility(aBuilder, aVisibleRegion,
                                         aAllowVisibleRegionExpansion)) {
     return false;
   }
   // Store the actual visible region
   mVisibleRegion.And(*aVisibleRegion, mVisibleRect);
   return true;
 }
 nsDisplayWrapList::nsDisplayWrapList(nsDisplayListBuilder* aBuilder,
                                      nsIFrame* aFrame, nsDisplayList* aList)
   : nsDisplayItem(aBuilder, aFrame)
   , mOverrideZIndex(0)
 {
   mList.AppendToTop(aList);
   UpdateBounds(aBuilder);
   if (!aFrame || !aFrame->IsTransformed()) {
     return;
   }
   // If the frame is a preserve-3d parent, then we will create transforms
   // inside this list afterwards (see WrapPreserve3DList in nsFrame.cpp).
   // In this case we will always be outside of the transform, so share
   // our parents reference frame.
   if (aFrame->Preserves3DChildren()) {
     mReferenceFrame =
       aBuilder->FindReferenceFrameFor(GetTransformRootFrame(aFrame));
     mToReferenceFrame = aFrame->GetOffsetToCrossDoc(mReferenceFrame);
     return;
   }
   // If we're a transformed frame, then we need to find out if we're inside
   // the nsDisplayTransform or outside of it. Frames inside the transform
   // need mReferenceFrame == mFrame, outside needs the next ancestor
   // reference frame.
   // If we're inside the transform, then the nsDisplayItem constructor
   // will have done the right thing.
   // If we're outside the transform, then we should have only one child
   // (since nsDisplayTransform wraps all actual content), and that child
   // will have the correct reference frame set (since nsDisplayTransform
   // handles this explictly).
   //
   // Preserve-3d can cause us to have multiple nsDisplayTransform
   // children.
   nsDisplayItem *i = mList.GetBottom();
   if (i && (!i->GetAbove() || i->GetType() == TYPE_TRANSFORM) &&
       i->Frame() == mFrame) {
     mReferenceFrame = i->ReferenceFrame();
     mToReferenceFrame = i->ToReferenceFrame();
   }
 }
 nsDisplayWrapList::nsDisplayWrapList(nsDisplayListBuilder* aBuilder,
                                      nsIFrame* aFrame, nsDisplayItem* aItem)
   : nsDisplayItem(aBuilder, aFrame)
   , mOverrideZIndex(0)
 {
   mList.AppendToTop(aItem);
   UpdateBounds(aBuilder);
   if (!aFrame || !aFrame->IsTransformed()) {
     return;
   }
   if (aFrame->Preserves3DChildren()) {
     mReferenceFrame =
       aBuilder->FindReferenceFrameFor(GetTransformRootFrame(aFrame));
     mToReferenceFrame = aFrame->GetOffsetToCrossDoc(mReferenceFrame);
     return;
   }
   // See the previous nsDisplayWrapList constructor
   if (aItem->Frame() == aFrame) {
     mReferenceFrame = aItem->ReferenceFrame();
     mToReferenceFrame = aItem->ToReferenceFrame();
   }
 }
 nsDisplayWrapList::nsDisplayWrapList(nsDisplayListBuilder* aBuilder,
                                      nsIFrame* aFrame, nsDisplayItem* aItem,
                                      const nsIFrame* aReferenceFrame,
                                      const nsPoint& aToReferenceFrame)
   : nsDisplayItem(aBuilder, aFrame, aReferenceFrame, aToReferenceFrame)
   , mOverrideZIndex(0)
 {
   mList.AppendToTop(aItem);
   mBounds = mList.GetBounds(aBuilder);
 }
 nsDisplayWrapList::~nsDisplayWrapList() {
   mList.DeleteAll();
 }
 void
 nsDisplayWrapList::HitTest(nsDisplayListBuilder* aBuilder, const nsRect& aRect,
                            HitTestState* aState, nsTArray<nsIFrame*> *aOutFrames) {
   mList.HitTest(aBuilder, aRect, aState, aOutFrames);
 }
 nsRect
 nsDisplayWrapList::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap) {
   *aSnap = false;
   return mBounds;
 }
 bool
 nsDisplayWrapList::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                      nsRegion* aVisibleRegion,
                                      const nsRect& aAllowVisibleRegionExpansion) {
   // Convert the passed in visible region to our appunits.
   nsRegion visibleRegion;
   // mVisibleRect has been clipped to GetClippedBounds
   visibleRegion.And(*aVisibleRegion, mVisibleRect);
   nsRegion originalVisibleRegion = visibleRegion;
   bool retval =
     mList.ComputeVisibilityForSublist(aBuilder, &visibleRegion,
                                       mVisibleRect,
                                       aAllowVisibleRegionExpansion);
   nsRegion removed;
   // removed = originalVisibleRegion - visibleRegion
   removed.Sub(originalVisibleRegion, visibleRegion);
   // aVisibleRegion = aVisibleRegion - removed (modulo any simplifications
   // SubtractFromVisibleRegion does)
   aBuilder->SubtractFromVisibleRegion(aVisibleRegion, removed);
   return retval;
 }
 nsRegion
 nsDisplayWrapList::GetOpaqueRegion(nsDisplayListBuilder* aBuilder,
                                    bool* aSnap) {
   *aSnap = false;
   nsRegion result;
   if (mList.IsOpaque()) {
     // Everything within GetBounds that's visible is opaque.
     result = GetBounds(aBuilder, aSnap);
   }
   return result;
 }
 bool nsDisplayWrapList::IsUniform(nsDisplayListBuilder* aBuilder, nscolor* aColor) {
   // We could try to do something but let's conservatively just return false.
   return false;
 }
 bool nsDisplayWrapList::IsVaryingRelativeToMovingFrame(nsDisplayListBuilder* aBuilder,
                                                          nsIFrame* aFrame) {
   NS_WARNING("nsDisplayWrapList::IsVaryingRelativeToMovingFrame called unexpectedly");
   // We could try to do something but let's conservatively just return true.
   return true;
 }
 void nsDisplayWrapList::Paint(nsDisplayListBuilder* aBuilder,
                               nsRenderingContext* aCtx) {
   NS_ERROR("nsDisplayWrapList should have been flattened away for painting");
 }
 /**
  * Returns true if all descendant display items can be placed in the same
  * ThebesLayer --- GetLayerState returns LAYER_INACTIVE or LAYER_NONE,
  * and they all have the expected animated geometry root.
  */
 static LayerState
 RequiredLayerStateForChildren(nsDisplayListBuilder* aBuilder,
                               LayerManager* aManager,
                               const ContainerLayerParameters& aParameters,
                               const nsDisplayList& aList,
                               nsIFrame* aExpectedAnimatedGeometryRootForChildren)
 {
   LayerState result = LAYER_INACTIVE;
   for (nsDisplayItem* i = aList.GetBottom(); i; i = i->GetAbove()) {
     if (result == LAYER_INACTIVE &&
         nsLayoutUtils::GetAnimatedGeometryRootFor(i, aBuilder) !=
           aExpectedAnimatedGeometryRootForChildren) {
       result = LAYER_ACTIVE;
     }
     LayerState state = i->GetLayerState(aBuilder, aManager, aParameters);
     if ((state == LAYER_ACTIVE || state == LAYER_ACTIVE_FORCE) &&
         state > result) {
       result = state;
     }
     if (state == LAYER_ACTIVE_EMPTY && state > result) {
       result = LAYER_ACTIVE_FORCE;
     }
     if (state == LAYER_NONE) {
       nsDisplayList* list = i->GetSameCoordinateSystemChildren();
       if (list) {
         LayerState childState =
           RequiredLayerStateForChildren(aBuilder, aManager, aParameters, *list,
               aExpectedAnimatedGeometryRootForChildren);
         if (childState > result) {
           result = childState;
         }
       }
     }
   }
   return result;
 }
 nsRect nsDisplayWrapList::GetComponentAlphaBounds(nsDisplayListBuilder* aBuilder)
 {
   nsRect bounds;
   for (nsDisplayItem* i = mList.GetBottom(); i; i = i->GetAbove()) {
     bounds.UnionRect(bounds, i->GetComponentAlphaBounds(aBuilder));
   }
   return bounds;
 }
 static nsresult
 WrapDisplayList(nsDisplayListBuilder* aBuilder, nsIFrame* aFrame,
                 nsDisplayList* aList, nsDisplayWrapper* aWrapper) {
   if (!aList->GetTop())
     return NS_OK;
   nsDisplayItem* item = aWrapper->WrapList(aBuilder, aFrame, aList);
   if (!item)
     return NS_ERROR_OUT_OF_MEMORY;
   // aList was emptied
   aList->AppendToTop(item);
   return NS_OK;
 }
 static nsresult
 WrapEachDisplayItem(nsDisplayListBuilder* aBuilder,
                     nsDisplayList* aList, nsDisplayWrapper* aWrapper) {
   nsDisplayList newList;
   nsDisplayItem* item;
   while ((item = aList->RemoveBottom())) {
     item = aWrapper->WrapItem(aBuilder, item);
     if (!item)
       return NS_ERROR_OUT_OF_MEMORY;
     newList.AppendToTop(item);
   }
   // aList was emptied
   aList->AppendToTop(&newList);
   return NS_OK;
 }
 nsresult nsDisplayWrapper::WrapLists(nsDisplayListBuilder* aBuilder,
     nsIFrame* aFrame, const nsDisplayListSet& aIn, const nsDisplayListSet& aOut)
 {
   nsresult rv = WrapListsInPlace(aBuilder, aFrame, aIn);
   NS_ENSURE_SUCCESS(rv, rv);
   if (&aOut == &aIn)
     return NS_OK;
   aOut.BorderBackground()->AppendToTop(aIn.BorderBackground());
   aOut.BlockBorderBackgrounds()->AppendToTop(aIn.BlockBorderBackgrounds());
   aOut.Floats()->AppendToTop(aIn.Floats());
   aOut.Content()->AppendToTop(aIn.Content());
   aOut.PositionedDescendants()->AppendToTop(aIn.PositionedDescendants());
   aOut.Outlines()->AppendToTop(aIn.Outlines());
   return NS_OK;
 }
 nsresult nsDisplayWrapper::WrapListsInPlace(nsDisplayListBuilder* aBuilder,
     nsIFrame* aFrame, const nsDisplayListSet& aLists)
 {
   nsresult rv;
   if (WrapBorderBackground()) {
     // Our border-backgrounds are in-flow
     rv = WrapDisplayList(aBuilder, aFrame, aLists.BorderBackground(), this);
     NS_ENSURE_SUCCESS(rv, rv);
   }
   // Our block border-backgrounds are in-flow
   rv = WrapDisplayList(aBuilder, aFrame, aLists.BlockBorderBackgrounds(), this);
   NS_ENSURE_SUCCESS(rv, rv);
   // The floats are not in flow
   rv = WrapEachDisplayItem(aBuilder, aLists.Floats(), this);
   NS_ENSURE_SUCCESS(rv, rv);
   // Our child content is in flow
   rv = WrapDisplayList(aBuilder, aFrame, aLists.Content(), this);
   NS_ENSURE_SUCCESS(rv, rv);
   // The positioned descendants may not be in-flow
   rv = WrapEachDisplayItem(aBuilder, aLists.PositionedDescendants(), this);
   NS_ENSURE_SUCCESS(rv, rv);
   // The outlines may not be in-flow
   return WrapEachDisplayItem(aBuilder, aLists.Outlines(), this);
 }
 nsDisplayOpacity::nsDisplayOpacity(nsDisplayListBuilder* aBuilder,
                                    nsIFrame* aFrame, nsDisplayList* aList)
     : nsDisplayWrapList(aBuilder, aFrame, aList) {
   MOZ_COUNT_CTOR(nsDisplayOpacity);
 }
 #ifdef NS_BUILD_REFCNT_LOGGING
 nsDisplayOpacity::~nsDisplayOpacity() {
   MOZ_COUNT_DTOR(nsDisplayOpacity);
 }
 #endif
 nsRegion nsDisplayOpacity::GetOpaqueRegion(nsDisplayListBuilder* aBuilder,
                                            bool* aSnap) {
   *aSnap = false;
   // We are never opaque, if our opacity was < 1 then we wouldn't have
   // been created.
   return nsRegion();
 }
 // nsDisplayOpacity uses layers for rendering
 already_AddRefed<Layer>
 nsDisplayOpacity::BuildLayer(nsDisplayListBuilder* aBuilder,
                              LayerManager* aManager,
                              const ContainerLayerParameters& aContainerParameters) {
   if (mFrame->StyleDisplay()->mOpacity == 0 && mFrame->GetContent() &&
       !nsLayoutUtils::HasAnimations(mFrame->GetContent(), eCSSProperty_opacity)) {
     return nullptr;
   }
   nsRefPtr<Layer> container = aManager->GetLayerBuilder()->
     BuildContainerLayerFor(aBuilder, aManager, mFrame, this, mList,
                            aContainerParameters, nullptr);
   if (!container)
     return nullptr;
   container->SetOpacity(mFrame->StyleDisplay()->mOpacity);
   nsDisplayListBuilder::AddAnimationsAndTransitionsToLayer(container, aBuilder,
                                                            this, mFrame,
                                                            eCSSProperty_opacity);
   return container.forget();
 }
 /**
  * This doesn't take into account layer scaling --- the layer may be
  * rendered at a higher (or lower) resolution, affecting the retained layer
  * size --- but this should be good enough.
  */
 static bool
 IsItemTooSmallForActiveLayer(nsDisplayItem* aItem)
 {
   nsIntRect visibleDevPixels = aItem->GetVisibleRect().ToOutsidePixels(
           aItem->Frame()->PresContext()->AppUnitsPerDevPixel());
   static const int MIN_ACTIVE_LAYER_SIZE_DEV_PIXELS = 16;
   return visibleDevPixels.Size() <
     nsIntSize(MIN_ACTIVE_LAYER_SIZE_DEV_PIXELS, MIN_ACTIVE_LAYER_SIZE_DEV_PIXELS);
 }
 bool
 nsDisplayOpacity::NeedsActiveLayer()
 {
   if (ActiveLayerTracker::IsStyleAnimated(mFrame, eCSSProperty_opacity) &&
       !IsItemTooSmallForActiveLayer(this))
     return true;
   if (mFrame->GetContent()) {
     if (nsLayoutUtils::HasAnimationsForCompositor(mFrame->GetContent(),
                                                   eCSSProperty_opacity)) {
       return true;
     }
   }
   return false;
 }
 bool
 nsDisplayOpacity::ShouldFlattenAway(nsDisplayListBuilder* aBuilder)
 {
   if (NeedsActiveLayer())
     return false;
   nsDisplayItem* child = mList.GetBottom();
   // Only try folding our opacity down if we have a single
   // child. We could potentially do this also if we had multiple
   // children as long as they don't overlap.
   if (!child || child->GetAbove()) {
     return false;
   }
   return child->ApplyOpacity(aBuilder, mFrame->StyleDisplay()->mOpacity, mClip);
 }
 nsDisplayItem::LayerState
 nsDisplayOpacity::GetLayerState(nsDisplayListBuilder* aBuilder,
                                 LayerManager* aManager,
                                 const ContainerLayerParameters& aParameters) {
   if (NeedsActiveLayer())
     return LAYER_ACTIVE;
   return RequiredLayerStateForChildren(aBuilder, aManager, aParameters, mList,
     nsLayoutUtils::GetAnimatedGeometryRootFor(this, aBuilder));
 }
 bool
 nsDisplayOpacity::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                     nsRegion* aVisibleRegion,
                                     const nsRect& aAllowVisibleRegionExpansion) {
   // Our children are translucent so we should not allow them to subtract
   // area from aVisibleRegion. We do need to find out what is visible under
   // our children in the temporary compositing buffer, because if our children
   // paint our entire bounds opaquely then we don't need an alpha channel in
   // the temporary compositing buffer.
   nsRect bounds = GetClippedBounds(aBuilder);
   nsRegion visibleUnderChildren;
   visibleUnderChildren.And(*aVisibleRegion, bounds);
   nsRect allowExpansion = bounds.Intersect(aAllowVisibleRegionExpansion);
   return
     nsDisplayWrapList::ComputeVisibility(aBuilder, &visibleUnderChildren,
                                          allowExpansion);
 }
 bool nsDisplayOpacity::TryMerge(nsDisplayListBuilder* aBuilder, nsDisplayItem* aItem) {
   if (aItem->GetType() != TYPE_OPACITY)
     return false;
   // items for the same content element should be merged into a single
   // compositing group
   // aItem->GetUnderlyingFrame() returns non-null because it's nsDisplayOpacity
   if (aItem->Frame()->GetContent() != mFrame->GetContent())
     return false;
   if (aItem->GetClip() != GetClip())
     return false;
   MergeFromTrackingMergedFrames(static_cast<nsDisplayOpacity*>(aItem));
   return true;
 }
 #ifdef MOZ_DUMP_PAINTING
 void
 nsDisplayOpacity::WriteDebugInfo(nsACString& aTo)
 {
   aTo += nsPrintfCString(" (opacity %f)", mFrame->StyleDisplay()->mOpacity);
 }
 #endif
 nsDisplayMixBlendMode::nsDisplayMixBlendMode(nsDisplayListBuilder* aBuilder,
                                              nsIFrame* aFrame, nsDisplayList* aList,
                                              uint32_t aFlags)
 : nsDisplayWrapList(aBuilder, aFrame, aList) {
   MOZ_COUNT_CTOR(nsDisplayMixBlendMode);
 }
 #ifdef NS_BUILD_REFCNT_LOGGING
 nsDisplayMixBlendMode::~nsDisplayMixBlendMode() {
   MOZ_COUNT_DTOR(nsDisplayMixBlendMode);
 }
 #endif
 nsRegion nsDisplayMixBlendMode::GetOpaqueRegion(nsDisplayListBuilder* aBuilder,
                                                 bool* aSnap) {
   *aSnap = false;
   // We are never considered opaque
   return nsRegion();
 }
 // nsDisplayMixBlendMode uses layers for rendering
 already_AddRefed<Layer>
 nsDisplayMixBlendMode::BuildLayer(nsDisplayListBuilder* aBuilder,
                                   LayerManager* aManager,
                                   const ContainerLayerParameters& aContainerParameters) {
   ContainerLayerParameters newContainerParameters = aContainerParameters;
   newContainerParameters.mDisableSubpixelAntialiasingInDescendants = true;
   nsRefPtr<Layer> container = aManager->GetLayerBuilder()->
   BuildContainerLayerFor(aBuilder, aManager, mFrame, this, mList,
                          newContainerParameters, nullptr);
   if (!container) {
     return nullptr;
   }
   container->DeprecatedSetMixBlendMode(nsCSSRendering::GetGFXBlendMode(mFrame->StyleDisplay()->mMixBlendMode));
   return container.forget();
 }
 bool nsDisplayMixBlendMode::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                               nsRegion* aVisibleRegion,
                                               const nsRect& aAllowVisibleRegionExpansion) {
   // Our children are need their backdrop so we should not allow them to subtract
   // area from aVisibleRegion. We do need to find out what is visible under
   // our children in the temporary compositing buffer, because if our children
   // paint our entire bounds opaquely then we don't need an alpha channel in
   // the temporary compositing buffer.
   nsRect bounds = GetClippedBounds(aBuilder);
   nsRegion visibleUnderChildren;
   visibleUnderChildren.And(*aVisibleRegion, bounds);
   nsRect allowExpansion = bounds.Intersect(aAllowVisibleRegionExpansion);
   return
   nsDisplayWrapList::ComputeVisibility(aBuilder, &visibleUnderChildren,
                                        allowExpansion);
 }
 bool nsDisplayMixBlendMode::TryMerge(nsDisplayListBuilder* aBuilder, nsDisplayItem* aItem) {
   if (aItem->GetType() != TYPE_MIX_BLEND_MODE)
     return false;
   // items for the same content element should be merged into a single
   // compositing group
   // aItem->GetUnderlyingFrame() returns non-null because it's nsDisplayOpacity
   if (aItem->Frame()->GetContent() != mFrame->GetContent())
     return false;
   if (aItem->GetClip() != GetClip())
     return false;
   MergeFromTrackingMergedFrames(static_cast<nsDisplayMixBlendMode*>(aItem));
   return true;
 }
 nsDisplayBlendContainer::nsDisplayBlendContainer(nsDisplayListBuilder* aBuilder,
                                                  nsIFrame* aFrame, nsDisplayList* aList,
                                                  uint32_t aFlags)
     : nsDisplayWrapList(aBuilder, aFrame, aList) {
   MOZ_COUNT_CTOR(nsDisplayBlendContainer);
 }
 #ifdef NS_BUILD_REFCNT_LOGGING
 nsDisplayBlendContainer::~nsDisplayBlendContainer() {
   MOZ_COUNT_DTOR(nsDisplayBlendContainer);
 }
 #endif
 // nsDisplayBlendContainer uses layers for rendering
 already_AddRefed<Layer>
 nsDisplayBlendContainer::BuildLayer(nsDisplayListBuilder* aBuilder,
                                     LayerManager* aManager,
                                     const ContainerLayerParameters& aContainerParameters) {
   // turn off anti-aliasing in the parent stacking context because it changes
   // how the group is initialized.
   ContainerLayerParameters newContainerParameters = aContainerParameters;
   newContainerParameters.mDisableSubpixelAntialiasingInDescendants = true;
   nsRefPtr<Layer> container = aManager->GetLayerBuilder()->
   BuildContainerLayerFor(aBuilder, aManager, mFrame, this, mList,
                          newContainerParameters, nullptr);
   if (!container) {
     return nullptr;
   }
   container->SetForceIsolatedGroup(true);
   return container.forget();
 }
 bool nsDisplayBlendContainer::TryMerge(nsDisplayListBuilder* aBuilder, nsDisplayItem* aItem) {
   if (aItem->GetType() != TYPE_BLEND_CONTAINER)
     return false;
   // items for the same content element should be merged into a single
   // compositing group
   // aItem->GetUnderlyingFrame() returns non-null because it's nsDisplayOpacity
   if (aItem->Frame()->GetContent() != mFrame->GetContent())
     return false;
   if (aItem->GetClip() != GetClip())
     return false;
   MergeFromTrackingMergedFrames(static_cast<nsDisplayBlendContainer*>(aItem));
   return true;
 }
 nsDisplayOwnLayer::nsDisplayOwnLayer(nsDisplayListBuilder* aBuilder,
                                      nsIFrame* aFrame, nsDisplayList* aList,
                                      uint32_t aFlags, ViewID aScrollTarget)
     : nsDisplayWrapList(aBuilder, aFrame, aList)
     , mFlags(aFlags)
     , mScrollTarget(aScrollTarget) {
   MOZ_COUNT_CTOR(nsDisplayOwnLayer);
 }
 #ifdef NS_BUILD_REFCNT_LOGGING
 nsDisplayOwnLayer::~nsDisplayOwnLayer() {
   MOZ_COUNT_DTOR(nsDisplayOwnLayer);
 }
 #endif
 // nsDisplayOpacity uses layers for rendering
 already_AddRefed<Layer>
 nsDisplayOwnLayer::BuildLayer(nsDisplayListBuilder* aBuilder,
                               LayerManager* aManager,
                               const ContainerLayerParameters& aContainerParameters) {
   nsRefPtr<ContainerLayer> layer = aManager->GetLayerBuilder()->
     BuildContainerLayerFor(aBuilder, aManager, mFrame, this, mList,
                            aContainerParameters, nullptr);
   if (mFlags & VERTICAL_SCROLLBAR) {
     layer->SetScrollbarData(mScrollTarget, Layer::ScrollDirection::VERTICAL);
   }
   if (mFlags & HORIZONTAL_SCROLLBAR) {
     layer->SetScrollbarData(mScrollTarget, Layer::ScrollDirection::HORIZONTAL);
   }
   if (mFlags & GENERATE_SUBDOC_INVALIDATIONS) {
     mFrame->PresContext()->SetNotifySubDocInvalidationData(layer);
   }
   return layer.forget();
 }
 nsDisplaySubDocument::nsDisplaySubDocument(nsDisplayListBuilder* aBuilder,
                                            nsIFrame* aFrame, nsDisplayList* aList,
                                            uint32_t aFlags)
     : nsDisplayOwnLayer(aBuilder, aFrame, aList, aFlags)
     , mScrollParentId(aBuilder->GetCurrentScrollParentId())
 {
   MOZ_COUNT_CTOR(nsDisplaySubDocument);
 }
 #ifdef NS_BUILD_REFCNT_LOGGING
 nsDisplaySubDocument::~nsDisplaySubDocument() {
   MOZ_COUNT_DTOR(nsDisplaySubDocument);
 }
 #endif
 already_AddRefed<Layer>
 nsDisplaySubDocument::BuildLayer(nsDisplayListBuilder* aBuilder,
                                  LayerManager* aManager,
                                  const ContainerLayerParameters& aContainerParameters) {
   nsRefPtr<Layer> layer = nsDisplayOwnLayer::BuildLayer(
     aBuilder, aManager, aContainerParameters);
   if (!(mFlags & GENERATE_SCROLLABLE_LAYER)) {
     return layer.forget();
   }
   NS_ASSERTION(layer->AsContainerLayer(), "nsDisplayOwnLayer should have made a ContainerLayer");
   if (ContainerLayer* container = layer->AsContainerLayer()) {
     nsPresContext* presContext = mFrame->PresContext();
     nsIFrame* rootScrollFrame = presContext->PresShell()->GetRootScrollFrame();
     bool isRootContentDocument = presContext->IsRootContentDocument();
     bool usingDisplayport = false;
     bool usingCriticalDisplayport = false;
     nsRect displayport, criticalDisplayport;
     ViewID scrollId = FrameMetrics::NULL_SCROLL_ID;
     if (rootScrollFrame) {
       nsIContent* content = rootScrollFrame->GetContent();
       if (content) {
         usingDisplayport = nsLayoutUtils::GetDisplayPort(content, &displayport);
         usingCriticalDisplayport =
           nsLayoutUtils::GetCriticalDisplayPort(content, &criticalDisplayport);
         if (isRootContentDocument) {
           scrollId = nsLayoutUtils::FindOrCreateIDFor(content);
         } else {
           nsLayoutUtils::FindIDFor(content, &scrollId);
         }
       }
     }
     nsRect viewport = mFrame->GetRect() -
                       mFrame->GetPosition() +
                       mFrame->GetOffsetToCrossDoc(ReferenceFrame());
     container->SetScrollHandoffParentId(mScrollParentId);
     RecordFrameMetrics(mFrame, rootScrollFrame, ReferenceFrame(),
                        container, mList.GetVisibleRect(), viewport,
                        (usingDisplayport ? &displayport : nullptr),
                        (usingCriticalDisplayport ? &criticalDisplayport : nullptr),
                        scrollId, isRootContentDocument, aContainerParameters);
   }
   return layer.forget();
 }
 nsRect
 nsDisplaySubDocument::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap)
 {
   bool usingDisplayPort =
     nsLayoutUtils::ViewportHasDisplayPort(mFrame->PresContext());
   if ((mFlags & GENERATE_SCROLLABLE_LAYER) && usingDisplayPort) {
     *aSnap = false;
     return mFrame->GetRect() + aBuilder->ToReferenceFrame(mFrame);
   }
   return nsDisplayOwnLayer::GetBounds(aBuilder, aSnap);
 }
 bool
 nsDisplaySubDocument::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                         nsRegion* aVisibleRegion,
                                         const nsRect& aAllowVisibleRegionExpansion)
 {
   nsRect displayport;
   bool usingDisplayPort =
     nsLayoutUtils::ViewportHasDisplayPort(mFrame->PresContext(), &displayport);
   if (!(mFlags & GENERATE_SCROLLABLE_LAYER) || !usingDisplayPort) {
     return nsDisplayWrapList::ComputeVisibility(aBuilder, aVisibleRegion,
                                                 aAllowVisibleRegionExpansion);
   }
   nsRegion childVisibleRegion;
   // The visible region for the children may be much bigger than the hole we
   // are viewing the children from, so that the compositor process has enough
   // content to asynchronously pan while content is being refreshed.
   childVisibleRegion = displayport + mFrame->GetOffsetToCrossDoc(ReferenceFrame());
   nsRect boundedRect =
     childVisibleRegion.GetBounds().Intersect(mList.GetBounds(aBuilder));
   nsRect allowExpansion = boundedRect.Intersect(aAllowVisibleRegionExpansion);
   bool visible = mList.ComputeVisibilityForSublist(
     aBuilder, &childVisibleRegion, boundedRect, allowExpansion,
     usingDisplayPort ? mFrame : nullptr);
   // We don't allow this computation to influence aVisibleRegion, on the
   // assumption that the layer can be asynchronously scrolled so we'll
   // definitely need all the content under it.
   return visible;
 }
 bool
 nsDisplaySubDocument::ShouldBuildLayerEvenIfInvisible(nsDisplayListBuilder* aBuilder)
 {
   bool usingDisplayPort =
     nsLayoutUtils::ViewportHasDisplayPort(mFrame->PresContext());
   if ((mFlags & GENERATE_SCROLLABLE_LAYER) && usingDisplayPort) {
     return true;
   }
   return nsDisplayOwnLayer::ShouldBuildLayerEvenIfInvisible(aBuilder);
 }
 nsRegion
 nsDisplaySubDocument::GetOpaqueRegion(nsDisplayListBuilder* aBuilder, bool* aSnap)
 {
   bool usingDisplayPort =
     nsLayoutUtils::ViewportHasDisplayPort(mFrame->PresContext());
   if ((mFlags & GENERATE_SCROLLABLE_LAYER) && usingDisplayPort) {
     *aSnap = false;
     return nsRegion();
   }
   return nsDisplayOwnLayer::GetOpaqueRegion(aBuilder, aSnap);
 }
 nsDisplayResolution::nsDisplayResolution(nsDisplayListBuilder* aBuilder,
                                          nsIFrame* aFrame, nsDisplayList* aList,
                                          uint32_t aFlags)
     : nsDisplaySubDocument(aBuilder, aFrame, aList, aFlags) {
   MOZ_COUNT_CTOR(nsDisplayResolution);
 }
 #ifdef NS_BUILD_REFCNT_LOGGING
 nsDisplayResolution::~nsDisplayResolution() {
   MOZ_COUNT_DTOR(nsDisplayResolution);
 }
 #endif
 already_AddRefed<Layer>
 nsDisplayResolution::BuildLayer(nsDisplayListBuilder* aBuilder,
                                 LayerManager* aManager,
                                 const ContainerLayerParameters& aContainerParameters) {
   nsIPresShell* presShell = mFrame->PresContext()->PresShell();
   ContainerLayerParameters containerParameters(
     presShell->GetXResolution(), presShell->GetYResolution(), nsIntPoint(),
     aContainerParameters);
   nsRefPtr<Layer> layer = nsDisplaySubDocument::BuildLayer(
     aBuilder, aManager, containerParameters);
   layer->SetPostScale(1.0f / presShell->GetXResolution(),
 .0f / presShell->GetYResolution());
   return layer.forget();
 }
 nsDisplayStickyPosition::nsDisplayStickyPosition(nsDisplayListBuilder* aBuilder,
                                                  nsIFrame* aFrame,
                                                  nsDisplayList* aList)
   : nsDisplayOwnLayer(aBuilder, aFrame, aList)
 {
   MOZ_COUNT_CTOR(nsDisplayStickyPosition);
 }
 #ifdef NS_BUILD_REFCNT_LOGGING
 nsDisplayStickyPosition::~nsDisplayStickyPosition() {
   MOZ_COUNT_DTOR(nsDisplayStickyPosition);
 }
 #endif
 already_AddRefed<Layer>
 nsDisplayStickyPosition::BuildLayer(nsDisplayListBuilder* aBuilder,
                                     LayerManager* aManager,
                                     const ContainerLayerParameters& aContainerParameters) {
   nsRefPtr<Layer> layer =
     nsDisplayOwnLayer::BuildLayer(aBuilder, aManager, aContainerParameters);
   StickyScrollContainer* stickyScrollContainer = StickyScrollContainer::
     GetStickyScrollContainerForFrame(mFrame);
   if (!stickyScrollContainer) {
     return layer.forget();
   }
   nsIFrame* scrollFrame = do_QueryFrame(stickyScrollContainer->ScrollFrame());
   nsPresContext* presContext = scrollFrame->PresContext();
   // Sticky position frames whose scroll frame is the root scroll frame are
   // reflowed into the scroll-port size if one has been set.
   nsSize scrollFrameSize = scrollFrame->GetSize();
   if (scrollFrame == presContext->PresShell()->GetRootScrollFrame() &&
       presContext->PresShell()->IsScrollPositionClampingScrollPortSizeSet()) {
     scrollFrameSize = presContext->PresShell()->
       GetScrollPositionClampingScrollPortSize();
   }
   nsLayoutUtils::SetFixedPositionLayerData(layer, scrollFrame,
     nsRect(scrollFrame->GetOffsetToCrossDoc(ReferenceFrame()), scrollFrameSize),
     mFrame, presContext, aContainerParameters);
   ViewID scrollId = nsLayoutUtils::FindOrCreateIDFor(
     stickyScrollContainer->ScrollFrame()->GetScrolledFrame()->GetContent());
   float factor = presContext->AppUnitsPerDevPixel();
   nsRect outer;
   nsRect inner;
   stickyScrollContainer->GetScrollRanges(mFrame, &outer, &inner);
   LayerRect stickyOuter(NSAppUnitsToFloatPixels(outer.x, factor) *
                           aContainerParameters.mXScale,
                         NSAppUnitsToFloatPixels(outer.y, factor) *
                           aContainerParameters.mYScale,
                         NSAppUnitsToFloatPixels(outer.width, factor) *
                           aContainerParameters.mXScale,
                         NSAppUnitsToFloatPixels(outer.height, factor) *
                           aContainerParameters.mYScale);
   LayerRect stickyInner(NSAppUnitsToFloatPixels(inner.x, factor) *
                           aContainerParameters.mXScale,
                         NSAppUnitsToFloatPixels(inner.y, factor) *
                           aContainerParameters.mYScale,
                         NSAppUnitsToFloatPixels(inner.width, factor) *
                           aContainerParameters.mXScale,
                         NSAppUnitsToFloatPixels(inner.height, factor) *
                           aContainerParameters.mYScale);
   layer->SetStickyPositionData(scrollId, stickyOuter, stickyInner);
   return layer.forget();
 }
 bool nsDisplayStickyPosition::TryMerge(nsDisplayListBuilder* aBuilder, nsDisplayItem* aItem) {
   if (aItem->GetType() != TYPE_STICKY_POSITION)
     return false;
   // Items with the same fixed position frame can be merged.
   nsDisplayStickyPosition* other = static_cast<nsDisplayStickyPosition*>(aItem);
   if (other->mFrame != mFrame)
     return false;
   if (aItem->GetClip() != GetClip())
     return false;
   MergeFromTrackingMergedFrames(other);
   return true;
 }
 nsDisplayScrollLayer::nsDisplayScrollLayer(nsDisplayListBuilder* aBuilder,
                                            nsDisplayList* aList,
                                            nsIFrame* aForFrame,
                                            nsIFrame* aScrolledFrame,
                                            nsIFrame* aScrollFrame)
   : nsDisplayWrapList(aBuilder, aForFrame, aList)
   , mScrollFrame(aScrollFrame)
   , mScrolledFrame(aScrolledFrame)
   , mScrollParentId(aBuilder->GetCurrentScrollParentId())
 {
 #ifdef NS_BUILD_REFCNT_LOGGING
   MOZ_COUNT_CTOR(nsDisplayScrollLayer);
 #endif
   NS_ASSERTION(mScrolledFrame && mScrolledFrame->GetContent(),
                "Need a child frame with content");
 }
 nsDisplayScrollLayer::nsDisplayScrollLayer(nsDisplayListBuilder* aBuilder,
                                            nsDisplayItem* aItem,
                                            nsIFrame* aForFrame,
                                            nsIFrame* aScrolledFrame,
                                            nsIFrame* aScrollFrame)
   : nsDisplayWrapList(aBuilder, aForFrame, aItem)
   , mScrollFrame(aScrollFrame)
   , mScrolledFrame(aScrolledFrame)
   , mScrollParentId(aBuilder->GetCurrentScrollParentId())
 {
 #ifdef NS_BUILD_REFCNT_LOGGING
   MOZ_COUNT_CTOR(nsDisplayScrollLayer);
 #endif
   NS_ASSERTION(mScrolledFrame && mScrolledFrame->GetContent(),
                "Need a child frame with content");
 }
 nsDisplayScrollLayer::nsDisplayScrollLayer(nsDisplayListBuilder* aBuilder,
                                            nsIFrame* aForFrame,
                                            nsIFrame* aScrolledFrame,
                                            nsIFrame* aScrollFrame)
   : nsDisplayWrapList(aBuilder, aForFrame)
   , mScrollFrame(aScrollFrame)
   , mScrolledFrame(aScrolledFrame)
   , mScrollParentId(aBuilder->GetCurrentScrollParentId())
 {
 #ifdef NS_BUILD_REFCNT_LOGGING
   MOZ_COUNT_CTOR(nsDisplayScrollLayer);
 #endif
   NS_ASSERTION(mScrolledFrame && mScrolledFrame->GetContent(),
                "Need a child frame with content");
 }
 #ifdef NS_BUILD_REFCNT_LOGGING
 nsDisplayScrollLayer::~nsDisplayScrollLayer()
 {
   MOZ_COUNT_DTOR(nsDisplayScrollLayer);
 }
 #endif
 nsRect
 nsDisplayScrollLayer::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap)
 {
   nsIScrollableFrame* sf = do_QueryFrame(mScrollFrame);
   if (sf) {
     *aSnap = false;
     return sf->GetScrollPortRect() + aBuilder->ToReferenceFrame(mScrollFrame);
   }
   return nsDisplayWrapList::GetBounds(aBuilder, aSnap);
 }
 already_AddRefed<Layer>
 nsDisplayScrollLayer::BuildLayer(nsDisplayListBuilder* aBuilder,
                                  LayerManager* aManager,
                                  const ContainerLayerParameters& aContainerParameters) {
   nsRefPtr<ContainerLayer> layer = aManager->GetLayerBuilder()->
     BuildContainerLayerFor(aBuilder, aManager, mFrame, this, mList,
                            aContainerParameters, nullptr);
   // Get the already set unique ID for scrolling this content remotely.
   // Or, if not set, generate a new ID.
   nsIContent* content = mScrolledFrame->GetContent();
   ViewID scrollId = nsLayoutUtils::FindOrCreateIDFor(content);
   nsRect viewport = mScrollFrame->GetRect() -
                     mScrollFrame->GetPosition() +
                     mScrollFrame->GetOffsetToCrossDoc(ReferenceFrame());
   bool usingDisplayport = false;
   bool usingCriticalDisplayport = false;
   nsRect displayport, criticalDisplayport;
   if (content) {
     usingDisplayport = nsLayoutUtils::GetDisplayPort(content, &displayport);
     usingCriticalDisplayport =
       nsLayoutUtils::GetCriticalDisplayPort(content, &criticalDisplayport);
   }
   layer->SetScrollHandoffParentId(mScrollParentId);
   RecordFrameMetrics(mScrolledFrame, mScrollFrame, ReferenceFrame(), layer,
                      mList.GetVisibleRect(), viewport,
                      (usingDisplayport ? &displayport : nullptr),
                      (usingCriticalDisplayport ? &criticalDisplayport : nullptr),
                      scrollId, false, aContainerParameters);
   return layer.forget();
 }
 bool
 nsDisplayScrollLayer::ShouldBuildLayerEvenIfInvisible(nsDisplayListBuilder* aBuilder)
 {
   if (nsLayoutUtils::GetDisplayPort(mScrolledFrame->GetContent(), nullptr)) {
     return true;
   }
   return nsDisplayWrapList::ShouldBuildLayerEvenIfInvisible(aBuilder);
 }
 bool
 nsDisplayScrollLayer::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                         nsRegion* aVisibleRegion,
                                         const nsRect& aAllowVisibleRegionExpansion)
 {
   nsRect displayport;
   bool usingDisplayPort =
     nsLayoutUtils::GetDisplayPort(mScrolledFrame->GetContent(), &displayport);
   nsRegion childVisibleRegion;
   if (usingDisplayPort) {
     // The visible region for the children may be much bigger than the hole we
     // are viewing the children from, so that the compositor process has enough
     // content to asynchronously pan while content is being refreshed.
     childVisibleRegion = displayport + mScrollFrame->GetOffsetToCrossDoc(ReferenceFrame());
   } else {
     bool snap;
     childVisibleRegion = GetBounds(aBuilder, &snap);
   }
   nsRect boundedRect =
     childVisibleRegion.GetBounds().Intersect(mList.GetBounds(aBuilder));
   nsRect allowExpansion = boundedRect.Intersect(aAllowVisibleRegionExpansion);
   bool visible = mList.ComputeVisibilityForSublist(
     aBuilder, &childVisibleRegion, boundedRect, allowExpansion,
     usingDisplayPort ? mScrollFrame : nullptr);
   // We don't allow this computation to influence aVisibleRegion, on the
   // assumption that the layer can be asynchronously scrolled so we'll
   // definitely need all the content under it.
   return visible;
 }
 LayerState
 nsDisplayScrollLayer::GetLayerState(nsDisplayListBuilder* aBuilder,
                                     LayerManager* aManager,
                                     const ContainerLayerParameters& aParameters)
 {
   // Force this as a layer so we can scroll asynchronously.
   // This causes incorrect rendering for rounded clips!
   return LAYER_ACTIVE_FORCE;
 }
 // Check if we are going to clip an abs pos item that we don't contain.
 // Root scroll frames clip all their descendants, so we don't need to worry
 // about them.
 bool
 WouldCauseIncorrectClippingOnAbsPosItem(nsDisplayListBuilder* aBuilder,
                                         nsDisplayScrollLayer* aItem)
 {
   nsIFrame* scrollFrame = aItem->GetScrollFrame();
   nsIPresShell* presShell = scrollFrame->PresContext()->PresShell();
   if (scrollFrame == presShell->GetRootScrollFrame()) {
     return false;
   }
   nsIFrame* scrolledFrame = aItem->GetScrolledFrame();
   nsIFrame* frame = aItem->Frame();
   if (frame == scrolledFrame || !frame->IsAbsolutelyPositioned() ||
       nsLayoutUtils::IsAncestorFrameCrossDoc(scrollFrame, frame, presShell->GetRootFrame())) {
     return false;
   }
   if (!aItem->GetClip().IsRectAffectedByClip(aItem->GetChildren()->GetBounds(aBuilder))) {
     return false;
   }
   return true;
 }
 bool
 nsDisplayScrollLayer::TryMerge(nsDisplayListBuilder* aBuilder,
                                nsDisplayItem* aItem)
 {
   if (aItem->GetType() != TYPE_SCROLL_LAYER) {
     return false;
   }
   nsDisplayScrollLayer* other = static_cast<nsDisplayScrollLayer*>(aItem);
   if (other->mScrolledFrame != this->mScrolledFrame) {
     return false;
   }
   if (aItem->GetClip() != GetClip()) {
     return false;
   }
   if (WouldCauseIncorrectClippingOnAbsPosItem(aBuilder, this) ||
       WouldCauseIncorrectClippingOnAbsPosItem(aBuilder, other)) {
     return false;
   }
   NS_ASSERTION(other->mReferenceFrame == mReferenceFrame,
                "Must have the same reference frame!");
   FrameProperties props = mScrolledFrame->Properties();
   props.Set(nsIFrame::ScrollLayerCount(),
     reinterpret_cast<void*>(GetScrollLayerCount() - 1));
   // Swap frames with the other item before doing MergeFrom.
   // XXX - This ensures that the frame associated with a scroll layer after
   // merging is the first, rather than the last. This tends to change less,
   // ensuring we're more likely to retain the associated gfx layer.
   // See Bug 729534 and Bug 731641.
   nsIFrame* tmp = mFrame;
   mFrame = other->mFrame;
   other->mFrame = tmp;
   MergeFromTrackingMergedFrames(other);
   return true;
 }
 void
 PropagateClip(nsDisplayListBuilder* aBuilder, const DisplayItemClip& aClip,
               nsDisplayList* aList)
 {
   for (nsDisplayItem* i = aList->GetBottom(); i != nullptr; i = i->GetAbove()) {
     DisplayItemClip clip(i->GetClip());
     clip.IntersectWith(aClip);
     i->SetClip(aBuilder, clip);
     nsDisplayList* list = i->GetSameCoordinateSystemChildren();
     if (list) {
       PropagateClip(aBuilder, aClip, list);
     }
   }
 }
 bool
 nsDisplayScrollLayer::ShouldFlattenAway(nsDisplayListBuilder* aBuilder)
 {
   bool badAbsPosClip = WouldCauseIncorrectClippingOnAbsPosItem(aBuilder, this);
   if (GetScrollLayerCount() > 1 || badAbsPosClip) {
     // Propagate our clip to our children. The clip for the scroll frame is
     // on this item, but not our child items so that they can draw non-visible
     // parts of the display port. But if we are flattening we failed and can't
     // draw the extra content, so it needs to be clipped.
     // But don't induce our clip on abs pos frames that we shouldn't be clipping.
     if (!badAbsPosClip) {
       PropagateClip(aBuilder, GetClip(), &mList);
     }
     return true;
   }
   if (mFrame != mScrolledFrame) {
     mMergedFrames.AppendElement(mFrame);
     mFrame = mScrolledFrame;
   }
   return false;
 }
 intptr_t
 nsDisplayScrollLayer::GetScrollLayerCount()
 {
   FrameProperties props = mScrolledFrame->Properties();
 #ifdef DEBUG
   bool hasCount = false;
   intptr_t result = reinterpret_cast<intptr_t>(
     props.Get(nsIFrame::ScrollLayerCount(), &hasCount));
   // If this aborts, then the property was either not added before scroll
   // layers were created or the property was deleted to early. If the latter,
   // make sure that nsDisplayScrollInfoLayer is on the bottom of the list so
   // that it is processed last.
   NS_ABORT_IF_FALSE(hasCount, "nsDisplayScrollLayer should always be defined");
   return result;
 #else
   return reinterpret_cast<intptr_t>(props.Get(nsIFrame::ScrollLayerCount()));
 #endif
 }
 #ifdef MOZ_DUMP_PAINTING
 void
 nsDisplayScrollLayer::WriteDebugInfo(nsACString& aTo)
 {
   aTo += nsPrintfCString(" (scrollframe %p scrolledframe %p)",
                          mScrollFrame, mScrolledFrame);
 }
 #endif
 nsDisplayScrollInfoLayer::nsDisplayScrollInfoLayer(
   nsDisplayListBuilder* aBuilder,
   nsIFrame* aScrolledFrame,
   nsIFrame* aScrollFrame)
   : nsDisplayScrollLayer(aBuilder, aScrollFrame, aScrolledFrame, aScrollFrame)
 {
 #ifdef NS_BUILD_REFCNT_LOGGING
   MOZ_COUNT_CTOR(nsDisplayScrollInfoLayer);
 #endif
 }
 nsDisplayScrollInfoLayer::~nsDisplayScrollInfoLayer()
 {
   FrameProperties props = mScrolledFrame->Properties();
   props.Remove(nsIFrame::ScrollLayerCount());
   MOZ_COUNT_DTOR(nsDisplayScrollInfoLayer);
 }
 nsRect
 nsDisplayScrollInfoLayer::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap)
 {
   return nsDisplayWrapList::GetBounds(aBuilder, aSnap);
 }
 LayerState
 nsDisplayScrollInfoLayer::GetLayerState(nsDisplayListBuilder* aBuilder,
                                         LayerManager* aManager,
                                         const ContainerLayerParameters& aParameters)
 {
   return LAYER_ACTIVE_EMPTY;
 }
 bool
 nsDisplayScrollInfoLayer::TryMerge(nsDisplayListBuilder* aBuilder,
                                    nsDisplayItem* aItem)
 {
   return false;
 }
 bool
 nsDisplayScrollInfoLayer::ShouldFlattenAway(nsDisplayListBuilder* aBuilder)
 {
   // Layer metadata for a particular scroll frame needs to be unique. Only
   // one nsDisplayScrollLayer (with rendered content) or one
   // nsDisplayScrollInfoLayer (with only the metadata) should survive the
   // visibility computation.
   return GetScrollLayerCount() == 1;
 }
 nsDisplayZoom::nsDisplayZoom(nsDisplayListBuilder* aBuilder,
                              nsIFrame* aFrame, nsDisplayList* aList,
                              int32_t aAPD, int32_t aParentAPD,
                              uint32_t aFlags)
     : nsDisplaySubDocument(aBuilder, aFrame, aList, aFlags)
     , mAPD(aAPD), mParentAPD(aParentAPD) {
   MOZ_COUNT_CTOR(nsDisplayZoom);
 }
 #ifdef NS_BUILD_REFCNT_LOGGING
 nsDisplayZoom::~nsDisplayZoom() {
   MOZ_COUNT_DTOR(nsDisplayZoom);
 }
 #endif
 nsRect nsDisplayZoom::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap)
 {
   nsRect bounds = nsDisplaySubDocument::GetBounds(aBuilder, aSnap);
   *aSnap = false;
   return bounds.ConvertAppUnitsRoundOut(mAPD, mParentAPD);
 }
 void nsDisplayZoom::HitTest(nsDisplayListBuilder *aBuilder,
                             const nsRect& aRect,
                             HitTestState *aState,
                             nsTArray<nsIFrame*> *aOutFrames)
 {
   nsRect rect;
   // A 1x1 rect indicates we are just hit testing a point, so pass down a 1x1
   // rect as well instead of possibly rounding the width or height to zero.
   if (aRect.width == 1 && aRect.height == 1) {
     rect.MoveTo(aRect.TopLeft().ConvertAppUnits(mParentAPD, mAPD));
     rect.width = rect.height = 1;
   } else {
     rect = aRect.ConvertAppUnitsRoundOut(mParentAPD, mAPD);
   }
   mList.HitTest(aBuilder, rect, aState, aOutFrames);
 }
 void nsDisplayZoom::Paint(nsDisplayListBuilder* aBuilder,
                           nsRenderingContext* aCtx)
 {
   mList.PaintForFrame(aBuilder, aCtx, mFrame, nsDisplayList::PAINT_DEFAULT);
 }
 bool nsDisplayZoom::ComputeVisibility(nsDisplayListBuilder *aBuilder,
                                       nsRegion *aVisibleRegion,
                                       const nsRect& aAllowVisibleRegionExpansion)
 {
   // Convert the passed in visible region to our appunits.
   nsRegion visibleRegion;
   // mVisibleRect has been clipped to GetClippedBounds
   visibleRegion.And(*aVisibleRegion, mVisibleRect);
   visibleRegion = visibleRegion.ConvertAppUnitsRoundOut(mParentAPD, mAPD);
   nsRegion originalVisibleRegion = visibleRegion;
   nsRect transformedVisibleRect =
     mVisibleRect.ConvertAppUnitsRoundOut(mParentAPD, mAPD);
   nsRect allowExpansion =
     aAllowVisibleRegionExpansion.ConvertAppUnitsRoundIn(mParentAPD, mAPD);
   bool retval;
   // If we are to generate a scrollable layer we call
   // nsDisplaySubDocument::ComputeVisibility to make the necessary adjustments
   // for ComputeVisibility, it does all it's calculations in the child APD.
   bool usingDisplayPort =
     nsLayoutUtils::ViewportHasDisplayPort(mFrame->PresContext());
   if (!(mFlags & GENERATE_SCROLLABLE_LAYER) || !usingDisplayPort) {
     retval =
       mList.ComputeVisibilityForSublist(aBuilder, &visibleRegion,
                                         transformedVisibleRect,
                                         allowExpansion);
   } else {
     retval =
       nsDisplaySubDocument::ComputeVisibility(aBuilder, &visibleRegion,
                                               allowExpansion);
   }
   nsRegion removed;
   // removed = originalVisibleRegion - visibleRegion
   removed.Sub(originalVisibleRegion, visibleRegion);
   // Convert removed region to parent appunits.
   removed = removed.ConvertAppUnitsRoundIn(mAPD, mParentAPD);
   // aVisibleRegion = aVisibleRegion - removed (modulo any simplifications
   // SubtractFromVisibleRegion does)
   aBuilder->SubtractFromVisibleRegion(aVisibleRegion, removed);
   return retval;
 }
 ///////////////////////////////////////////////////
 // nsDisplayTransform Implementation
 //
 // Write #define UNIFIED_CONTINUATIONS here to have the transform property try
 // to transform content with continuations as one unified block instead of
 // several smaller ones.  This is currently disabled because it doesn't work
 // correctly, since when the frames are initially being reflowed, their
 // continuations all compute their bounding rects independently of each other
 // and consequently get the wrong value.  Write #define DEBUG_HIT here to have
 // the nsDisplayTransform class dump out a bunch of information about hit
 // detection.
 #undef  UNIFIED_CONTINUATIONS
 #undef  DEBUG_HIT
 /* Returns the bounds of a frame as defined for transforms.  If
  * UNIFIED_CONTINUATIONS is not defined, this is simply the frame's bounding
  * rectangle, translated to the origin. Otherwise, returns the smallest
  * rectangle containing a frame and all of its continuations.  For example, if
  * there is a <span> element with several continuations split over several
  * lines, this function will return the rectangle containing all of those
  * continuations.  This rectangle is relative to the origin of the frame's local
  * coordinate space.
  */
 #ifndef UNIFIED_CONTINUATIONS
 nsRect
 nsDisplayTransform::GetFrameBoundsForTransform(const nsIFrame* aFrame)
 {
   NS_PRECONDITION(aFrame, "Can't get the bounds of a nonexistent frame!");
   if (aFrame->GetStateBits() & NS_FRAME_SVG_LAYOUT) {
     // TODO: SVG needs to define what percentage translations resolve against.
     return nsRect();
   }
   return nsRect(nsPoint(0, 0), aFrame->GetSize());
 }
 #else
 nsRect
 nsDisplayTransform::GetFrameBoundsForTransform(const nsIFrame* aFrame)
 {
   NS_PRECONDITION(aFrame, "Can't get the bounds of a nonexistent frame!");
   nsRect result;
   if (aFrame->GetStateBits() & NS_FRAME_SVG_LAYOUT) {
     // TODO: SVG needs to define what percentage translations resolve against.
     return result;
   }
   /* Iterate through the continuation list, unioning together all the
    * bounding rects.
    */
   for (const nsIFrame *currFrame = aFrame->FirstContinuation();
        currFrame != nullptr;
        currFrame = currFrame->GetNextContinuation())
     {
       /* Get the frame rect in local coordinates, then translate back to the
        * original coordinates.
        */
       result.UnionRect(result, nsRect(currFrame->GetOffsetTo(aFrame),
                                       currFrame->GetSize()));
     }
   return result;
 }
 #endif
 nsDisplayTransform::nsDisplayTransform(nsDisplayListBuilder* aBuilder, nsIFrame *aFrame,
                                        nsDisplayList *aList, ComputeTransformFunction aTransformGetter,
                                        uint32_t aIndex)
   : nsDisplayItem(aBuilder, aFrame)
   , mStoredList(aBuilder, aFrame, aList)
   , mTransformGetter(aTransformGetter)
   , mIndex(aIndex)
 {
   MOZ_COUNT_CTOR(nsDisplayTransform);
   NS_ABORT_IF_FALSE(aFrame, "Must have a frame!");
   NS_ABORT_IF_FALSE(!aFrame->IsTransformed(), "Can't specify a transform getter for a transformed frame!");
   mStoredList.SetClip(aBuilder, DisplayItemClip::NoClip());
 }
 nsDisplayTransform::nsDisplayTransform(nsDisplayListBuilder* aBuilder, nsIFrame *aFrame,
                                        nsDisplayList *aList, uint32_t aIndex)
   : nsDisplayItem(aBuilder, aFrame)
   , mStoredList(aBuilder, aFrame, aList)
   , mTransformGetter(nullptr)
   , mIndex(aIndex)
 {
   MOZ_COUNT_CTOR(nsDisplayTransform);
   NS_ABORT_IF_FALSE(aFrame, "Must have a frame!");
   mReferenceFrame =
     aBuilder->FindReferenceFrameFor(GetTransformRootFrame(aFrame));
   mToReferenceFrame = aFrame->GetOffsetToCrossDoc(mReferenceFrame);
   mStoredList.SetClip(aBuilder, DisplayItemClip::NoClip());
 }
 nsDisplayTransform::nsDisplayTransform(nsDisplayListBuilder* aBuilder, nsIFrame *aFrame,
                                        nsDisplayItem *aItem, uint32_t aIndex)
   : nsDisplayItem(aBuilder, aFrame)
   , mStoredList(aBuilder, aFrame, aItem)
   , mTransformGetter(nullptr)
   , mIndex(aIndex)
 {
   MOZ_COUNT_CTOR(nsDisplayTransform);
   NS_ABORT_IF_FALSE(aFrame, "Must have a frame!");
   mReferenceFrame =
     aBuilder->FindReferenceFrameFor(GetTransformRootFrame(aFrame));
   mToReferenceFrame = aFrame->GetOffsetToCrossDoc(mReferenceFrame);
   mStoredList.SetClip(aBuilder, DisplayItemClip::NoClip());
 }
 /* Returns the delta specified by the -moz-transform-origin property.
  * This is a positive delta, meaning that it indicates the direction to move
  * to get from (0, 0) of the frame to the transform origin.  This function is
  * called off the main thread.
  */
 /* static */ gfxPoint3D
 nsDisplayTransform::GetDeltaToTransformOrigin(const nsIFrame* aFrame,
                                               float aAppUnitsPerPixel,
                                               const nsRect* aBoundsOverride)
 {
   NS_PRECONDITION(aFrame, "Can't get delta for a null frame!");
   NS_PRECONDITION(aFrame->IsTransformed() || aFrame->StyleDisplay()->BackfaceIsHidden(),
                   "Shouldn't get a delta for an untransformed frame!");
   if (!aFrame->IsTransformed()) {
     return gfxPoint3D();
   }
   /* For both of the coordinates, if the value of -moz-transform is a
    * percentage, it's relative to the size of the frame.  Otherwise, if it's
    * a distance, it's already computed for us!
    */
   const nsStyleDisplay* display = aFrame->StyleDisplay();
   nsRect boundingRect = (aBoundsOverride ? *aBoundsOverride :
                          nsDisplayTransform::GetFrameBoundsForTransform(aFrame));
   /* Allows us to access named variables by index. */
   float coords[3];
   const nscoord* dimensions[2] =
     {&boundingRect.width, &boundingRect.height};
   for (uint8_t index = 0; index < 2; ++index) {
     /* If the -moz-transform-origin specifies a percentage, take the percentage
      * of the size of the box.
      */
     const nsStyleCoord &coord = display->mTransformOrigin[index];
     if (coord.GetUnit() == eStyleUnit_Calc) {
       const nsStyleCoord::Calc *calc = coord.GetCalcValue();
       coords[index] =
         NSAppUnitsToFloatPixels(*dimensions[index], aAppUnitsPerPixel) *
           calc->mPercent +
         NSAppUnitsToFloatPixels(calc->mLength, aAppUnitsPerPixel);
     } else if (coord.GetUnit() == eStyleUnit_Percent) {
       coords[index] =
         NSAppUnitsToFloatPixels(*dimensions[index], aAppUnitsPerPixel) *
         coord.GetPercentValue();
     } else {
       NS_ABORT_IF_FALSE(coord.GetUnit() == eStyleUnit_Coord, "unexpected unit");
       coords[index] =
         NSAppUnitsToFloatPixels(coord.GetCoordValue(), aAppUnitsPerPixel);
     }
     if ((aFrame->GetStateBits() & NS_FRAME_SVG_LAYOUT) &&
         coord.GetUnit() != eStyleUnit_Percent) {
       // <length> values represent offsets from the origin of the SVG element's
       // user space, not the top left of its bounds, so we must adjust for that:
       nscoord offset =
         (index == 0) ? aFrame->GetPosition().x : aFrame->GetPosition().y;
       coords[index] -= NSAppUnitsToFloatPixels(offset, aAppUnitsPerPixel);
     }
   }
   coords[2] = NSAppUnitsToFloatPixels(display->mTransformOrigin[2].GetCoordValue(),
                                       aAppUnitsPerPixel);
   /* Adjust based on the origin of the rectangle. */
   coords[0] += NSAppUnitsToFloatPixels(boundingRect.x, aAppUnitsPerPixel);
   coords[1] += NSAppUnitsToFloatPixels(boundingRect.y, aAppUnitsPerPixel);
   return gfxPoint3D(coords[0], coords[1], coords[2]);
 }
 /* Returns the delta specified by the -moz-perspective-origin property.
  * This is a positive delta, meaning that it indicates the direction to move
  * to get from (0, 0) of the frame to the perspective origin. This function is
  * called off the main thread.
  */
 /* static */ gfxPoint3D
 nsDisplayTransform::GetDeltaToPerspectiveOrigin(const nsIFrame* aFrame,
                                                 float aAppUnitsPerPixel)
 {
   NS_PRECONDITION(aFrame, "Can't get delta for a null frame!");
   NS_PRECONDITION(aFrame->IsTransformed() || aFrame->StyleDisplay()->BackfaceIsHidden(),
                   "Shouldn't get a delta for an untransformed frame!");
   if (!aFrame->IsTransformed()) {
     return gfxPoint3D();
   }
   /* For both of the coordinates, if the value of -moz-perspective-origin is a
    * percentage, it's relative to the size of the frame.  Otherwise, if it's
    * a distance, it's already computed for us!
    */
   //TODO: Should this be using our bounds or the parent's bounds?
   // How do we handle aBoundsOverride in the latter case?
   nsIFrame* parent = aFrame->GetParentStyleContextFrame();
   if (!parent) {
     return gfxPoint3D();
   }
   const nsStyleDisplay* display = parent->StyleDisplay();
   nsRect boundingRect = nsDisplayTransform::GetFrameBoundsForTransform(parent);
   /* Allows us to access named variables by index. */
   gfxPoint3D result;
   result.z = 0.0f;
   gfxFloat* coords[2] = {&result.x, &result.y};
   const nscoord* dimensions[2] =
     {&boundingRect.width, &boundingRect.height};
   for (uint8_t index = 0; index < 2; ++index) {
     /* If the -moz-transform-origin specifies a percentage, take the percentage
      * of the size of the box.
      */
     const nsStyleCoord &coord = display->mPerspectiveOrigin[index];
     if (coord.GetUnit() == eStyleUnit_Calc) {
       const nsStyleCoord::Calc *calc = coord.GetCalcValue();
       *coords[index] =
         NSAppUnitsToFloatPixels(*dimensions[index], aAppUnitsPerPixel) *
           calc->mPercent +
         NSAppUnitsToFloatPixels(calc->mLength, aAppUnitsPerPixel);
     } else if (coord.GetUnit() == eStyleUnit_Percent) {
       *coords[index] =
         NSAppUnitsToFloatPixels(*dimensions[index], aAppUnitsPerPixel) *
         coord.GetPercentValue();
     } else {
       NS_ABORT_IF_FALSE(coord.GetUnit() == eStyleUnit_Coord, "unexpected unit");
       *coords[index] =
         NSAppUnitsToFloatPixels(coord.GetCoordValue(), aAppUnitsPerPixel);
     }
   }
   nsPoint parentOffset = aFrame->GetOffsetTo(parent);
   gfxPoint3D gfxOffset(
                NSAppUnitsToFloatPixels(parentOffset.x, aAppUnitsPerPixel),
                NSAppUnitsToFloatPixels(parentOffset.y, aAppUnitsPerPixel),
 .0f);
   return result - gfxOffset;
 }
 nsDisplayTransform::FrameTransformProperties::FrameTransformProperties(const nsIFrame* aFrame,
                                                                        float aAppUnitsPerPixel,
                                                                        const nsRect* aBoundsOverride)
   : mFrame(aFrame)
   , mTransformList(aFrame->StyleDisplay()->mSpecifiedTransform)
   , mToTransformOrigin(GetDeltaToTransformOrigin(aFrame, aAppUnitsPerPixel, aBoundsOverride))
   , mToPerspectiveOrigin(GetDeltaToPerspectiveOrigin(aFrame, aAppUnitsPerPixel))
   , mChildPerspective(0)
 {
   const nsStyleDisplay* parentDisp = nullptr;
   nsStyleContext* parentStyleContext = aFrame->StyleContext()->GetParent();
   if (parentStyleContext) {
     parentDisp = parentStyleContext->StyleDisplay();
   }
   if (parentDisp && parentDisp->mChildPerspective.GetUnit() == eStyleUnit_Coord) {
     mChildPerspective = parentDisp->mChildPerspective.GetCoordValue();
   }
 }
 /* Wraps up the -moz-transform matrix in a change-of-basis matrix pair that
  * translates from local coordinate space to transform coordinate space, then
  * hands it back.
  */
 gfx3DMatrix
 nsDisplayTransform::GetResultingTransformMatrix(const FrameTransformProperties& aProperties,
                                                 const nsPoint& aOrigin,
                                                 float aAppUnitsPerPixel,
                                                 const nsRect* aBoundsOverride,
                                                 nsIFrame** aOutAncestor)
 {
   return GetResultingTransformMatrixInternal(aProperties, aOrigin, aAppUnitsPerPixel,
                                              aBoundsOverride, aOutAncestor);
 }
 gfx3DMatrix
 nsDisplayTransform::GetResultingTransformMatrix(const nsIFrame* aFrame,
                                                 const nsPoint& aOrigin,
                                                 float aAppUnitsPerPixel,
                                                 const nsRect* aBoundsOverride,
                                                 nsIFrame** aOutAncestor)
 {
   FrameTransformProperties props(aFrame,
                                  aAppUnitsPerPixel,
                                  aBoundsOverride);
   return GetResultingTransformMatrixInternal(props, aOrigin, aAppUnitsPerPixel,
                                              aBoundsOverride, aOutAncestor);
 }
 gfx3DMatrix
 nsDisplayTransform::GetResultingTransformMatrixInternal(const FrameTransformProperties& aProperties,
                                                         const nsPoint& aOrigin,
                                                         float aAppUnitsPerPixel,
                                                         const nsRect* aBoundsOverride,
                                                         nsIFrame** aOutAncestor)
 {
   const nsIFrame *frame = aProperties.mFrame;
   if (aOutAncestor) {
     *aOutAncestor = nsLayoutUtils::GetCrossDocParentFrame(frame);
   }
   /* Account for the -moz-transform-origin property by translating the
    * coordinate space to the new origin.
    */
   gfxPoint3D newOrigin =
     gfxPoint3D(NSAppUnitsToFloatPixels(aOrigin.x, aAppUnitsPerPixel),
                NSAppUnitsToFloatPixels(aOrigin.y, aAppUnitsPerPixel),
 .0f);
   /* Get the underlying transform matrix.  This requires us to get the
    * bounds of the frame.
    */
   nsRect bounds = (aBoundsOverride ? *aBoundsOverride :
                    nsDisplayTransform::GetFrameBoundsForTransform(frame));
   /* Get the matrix, then change its basis to factor in the origin. */
   bool dummy;
   gfx3DMatrix result;
   // Call IsSVGTransformed() regardless of the value of
   // disp->mSpecifiedTransform, since we still need any transformFromSVGParent.
   mozilla::gfx::Matrix svgTransform, transformFromSVGParent;
   bool hasSVGTransforms =
     frame && frame->IsSVGTransformed(&svgTransform, &transformFromSVGParent);
   /* Transformed frames always have a transform, or are preserving 3d (and might still have perspective!) */
   if (aProperties.mTransformList) {
     result = nsStyleTransformMatrix::ReadTransforms(aProperties.mTransformList->mHead,
                                                     frame ? frame->StyleContext() : nullptr,
                                                     frame ? frame->PresContext() : nullptr,
                                                     dummy, bounds, aAppUnitsPerPixel);
   } else if (hasSVGTransforms) {
     // Correct the translation components for zoom:
     float pixelsPerCSSPx = frame->PresContext()->AppUnitsPerCSSPixel() /
                              aAppUnitsPerPixel;
     svgTransform._31 *= pixelsPerCSSPx;
     svgTransform._32 *= pixelsPerCSSPx;
     result = gfx3DMatrix::From2D(ThebesMatrix(svgTransform));
   }
   if (hasSVGTransforms && !transformFromSVGParent.IsIdentity()) {
     // Correct the translation components for zoom:
     float pixelsPerCSSPx = frame->PresContext()->AppUnitsPerCSSPixel() /
                              aAppUnitsPerPixel;
     transformFromSVGParent._31 *= pixelsPerCSSPx;
     transformFromSVGParent._32 *= pixelsPerCSSPx;
     result = result * gfx3DMatrix::From2D(ThebesMatrix(transformFromSVGParent));
   }
   if (aProperties.mChildPerspective > 0.0) {
     gfx3DMatrix perspective;
     perspective._34 =
       -1.0 / NSAppUnitsToFloatPixels(aProperties.mChildPerspective, aAppUnitsPerPixel);
     /* At the point when perspective is applied, we have been translated to the transform origin.
      * The translation to the perspective origin is the difference between these values.
      */
     result = result * nsLayoutUtils::ChangeMatrixBasis(aProperties.mToPerspectiveOrigin - aProperties.mToTransformOrigin, perspective);
   }
   gfxPoint3D rounded(hasSVGTransforms ? newOrigin.x : NS_round(newOrigin.x),
                      hasSVGTransforms ? newOrigin.y : NS_round(newOrigin.y),
 );
   if (frame && frame->Preserves3D()) {
       // Include the transform set on our parent
       NS_ASSERTION(frame->GetParent() &&
                    frame->GetParent()->IsTransformed() &&
                    frame->GetParent()->Preserves3DChildren(),
                    "Preserve3D mismatch!");
       FrameTransformProperties props(frame->GetParent(),
                                      aAppUnitsPerPixel,
                                      nullptr);
       gfx3DMatrix parent =
         GetResultingTransformMatrixInternal(props,
                                             aOrigin - frame->GetPosition(),
                                             aAppUnitsPerPixel, nullptr, aOutAncestor);
       return nsLayoutUtils::ChangeMatrixBasis(rounded + aProperties.mToTransformOrigin, result) * parent;
   }
   return nsLayoutUtils::ChangeMatrixBasis
     (rounded + aProperties.mToTransformOrigin, result);
 }
 bool
 nsDisplayOpacity::CanUseAsyncAnimations(nsDisplayListBuilder* aBuilder)
 {
   if (ActiveLayerTracker::IsStyleAnimated(mFrame, eCSSProperty_opacity)) {
     return true;
   }
   if (nsLayoutUtils::IsAnimationLoggingEnabled()) {
     nsCString message;
     message.AppendLiteral("Performance warning: Async animation disabled because frame was not marked active for opacity animation");
     CommonElementAnimationData::LogAsyncAnimationFailure(message,
                                                          Frame()->GetContent());
   }
   return false;
 }
 bool
 nsDisplayTransform::CanUseAsyncAnimations(nsDisplayListBuilder* aBuilder)
 {
   return ShouldPrerenderTransformedContent(aBuilder,
                                            Frame(),
                                            nsLayoutUtils::IsAnimationLoggingEnabled());
 }
 /* static */ bool
 nsDisplayTransform::ShouldPrerenderTransformedContent(nsDisplayListBuilder* aBuilder,
                                                       nsIFrame* aFrame,
                                                       bool aLogAnimations)
 {
   // Elements whose transform has been modified recently, or which
   // have a compositor-animated transform, can be prerendered. An element
   // might have only just had its transform animated in which case
   // the ActiveLayerManager may not have been notified yet.
   if (!ActiveLayerTracker::IsStyleAnimated(aFrame, eCSSProperty_transform) &&
       (!aFrame->GetContent() ||
        !nsLayoutUtils::HasAnimationsForCompositor(aFrame->GetContent(),
                                                   eCSSProperty_transform))) {
     if (aLogAnimations) {
       nsCString message;
       message.AppendLiteral("Performance warning: Async animation disabled because frame was not marked active for transform animation");
       CommonElementAnimationData::LogAsyncAnimationFailure(message,
                                                            aFrame->GetContent());
     }
     return false;
   }
   nsSize refSize = aBuilder->RootReferenceFrame()->GetSize();
   // Only prerender if the transformed frame's size (in the reference
   // frames coordinate space) is <= the reference frame size (~viewport),
   // allowing a 1/8th fuzz factor for shadows, borders, etc.
   refSize += nsSize(refSize.width / 8, refSize.height / 8);
   nsRect frameRect = aFrame->GetVisualOverflowRectRelativeToSelf();
   frameRect =
     nsLayoutUtils::TransformFrameRectToAncestor(aFrame, frameRect,
                                                 aBuilder->RootReferenceFrame());
   if (frameRect.Size() <= refSize) {
     return true;
   }
   if (aLogAnimations) {
     nsCString message;
     message.AppendLiteral("Performance warning: Async animation disabled because frame size (");
     message.AppendInt(nsPresContext::AppUnitsToIntCSSPixels(frameRect.width));
     message.AppendLiteral(", ");
     message.AppendInt(nsPresContext::AppUnitsToIntCSSPixels(frameRect.height));
     message.AppendLiteral(") is bigger than the viewport (");
     message.AppendInt(nsPresContext::AppUnitsToIntCSSPixels(refSize.width));
     message.AppendLiteral(", ");
     message.AppendInt(nsPresContext::AppUnitsToIntCSSPixels(refSize.height));
     message.AppendLiteral(")");
     CommonElementAnimationData::LogAsyncAnimationFailure(message,
                                                          aFrame->GetContent());
   }
   return false;
 }
 /* If the matrix is singular, or a hidden backface is shown, the frame won't be visible or hit. */
 static bool IsFrameVisible(nsIFrame* aFrame, const gfx3DMatrix& aMatrix)
 {
   if (aMatrix.IsSingular()) {
     return false;
   }
   if (aFrame->StyleDisplay()->mBackfaceVisibility == NS_STYLE_BACKFACE_VISIBILITY_HIDDEN &&
       aMatrix.IsBackfaceVisible()) {
     return false;
   }
   return true;
 }
 const gfx3DMatrix&
 nsDisplayTransform::GetTransform()
 {
   if (mTransform.IsIdentity()) {
     float scale = mFrame->PresContext()->AppUnitsPerDevPixel();
     gfxPoint3D newOrigin =
       gfxPoint3D(NSAppUnitsToFloatPixels(mToReferenceFrame.x, scale),
                  NSAppUnitsToFloatPixels(mToReferenceFrame.y, scale),
 .0f);
     if (mTransformGetter) {
       mTransform = mTransformGetter(mFrame, scale);
       mTransform = nsLayoutUtils::ChangeMatrixBasis(newOrigin, mTransform);
     } else {
       mTransform =
         GetResultingTransformMatrix(mFrame, ToReferenceFrame(), scale);
       /**
        * Shift the coorindates to be relative to our reference frame instead of relative to this frame.
        *  When we have preserve-3d, our reference frame is already guaranteed to be an ancestor of the
        * preserve-3d chain, so we only need to do this once.
        */
       bool hasSVGTransforms = mFrame->IsSVGTransformed();
       gfxPoint3D rounded(hasSVGTransforms ? newOrigin.x : NS_round(newOrigin.x),
                          hasSVGTransforms ? newOrigin.y : NS_round(newOrigin.y),
 );
       mTransform.Translate(rounded);
     }
   }
   return mTransform;
 }
 bool
 nsDisplayTransform::ShouldBuildLayerEvenIfInvisible(nsDisplayListBuilder* aBuilder)
 {
   return ShouldPrerenderTransformedContent(aBuilder, mFrame, false);
 }
 already_AddRefed<Layer> nsDisplayTransform::BuildLayer(nsDisplayListBuilder *aBuilder,
                                                        LayerManager *aManager,
                                                        const ContainerLayerParameters& aContainerParameters)
 {
   const gfx3DMatrix& newTransformMatrix = GetTransform();
   if (mFrame->StyleDisplay()->mBackfaceVisibility == NS_STYLE_BACKFACE_VISIBILITY_HIDDEN &&
       newTransformMatrix.IsBackfaceVisible()) {
     return nullptr;
   }
   uint32_t flags = ShouldPrerenderTransformedContent(aBuilder, mFrame, false) ?
     FrameLayerBuilder::CONTAINER_NOT_CLIPPED_BY_ANCESTORS : 0;
   nsRefPtr<ContainerLayer> container = aManager->GetLayerBuilder()->
     BuildContainerLayerFor(aBuilder, aManager, mFrame, this, *mStoredList.GetChildren(),
                            aContainerParameters, &newTransformMatrix, flags);
   if (!container) {
     return nullptr;
   }
   // Add the preserve-3d flag for this layer, BuildContainerLayerFor clears all flags,
   // so we never need to explicitely unset this flag.
   if (mFrame->Preserves3D() || mFrame->Preserves3DChildren()) {
     container->SetContentFlags(container->GetContentFlags() | Layer::CONTENT_PRESERVE_3D);
   } else {
     container->SetContentFlags(container->GetContentFlags() & ~Layer::CONTENT_PRESERVE_3D);
   }
   nsDisplayListBuilder::AddAnimationsAndTransitionsToLayer(container, aBuilder,
                                                            this, mFrame,
                                                            eCSSProperty_transform);
   if (ShouldPrerenderTransformedContent(aBuilder, mFrame, false)) {
     container->SetUserData(nsIFrame::LayerIsPrerenderedDataKey(),
                            /*the value is irrelevant*/nullptr);
     container->SetContentFlags(container->GetContentFlags() | Layer::CONTENT_MAY_CHANGE_TRANSFORM);
   } else {
     container->RemoveUserData(nsIFrame::LayerIsPrerenderedDataKey());
     container->SetContentFlags(container->GetContentFlags() & ~Layer::CONTENT_MAY_CHANGE_TRANSFORM);
   }
   return container.forget();
 }
 nsDisplayItem::LayerState
 nsDisplayTransform::GetLayerState(nsDisplayListBuilder* aBuilder,
                                   LayerManager* aManager,
                                   const ContainerLayerParameters& aParameters) {
   // If the transform is 3d, or the layer takes part in preserve-3d sorting
   // then we *always* want this to be an active layer.
   if (!GetTransform().Is2D() || mFrame->Preserves3D()) {
     return LAYER_ACTIVE_FORCE;
   }
   // Here we check if the *post-transform* bounds of this item are big enough
   // to justify an active layer.
   if (ActiveLayerTracker::IsStyleAnimated(mFrame, eCSSProperty_transform) &&
       !IsItemTooSmallForActiveLayer(this))
     return LAYER_ACTIVE;
   if (mFrame->GetContent()) {
     if (nsLayoutUtils::HasAnimationsForCompositor(mFrame->GetContent(),
                                                   eCSSProperty_transform)) {
       return LAYER_ACTIVE;
     }
   }
   const nsStyleDisplay* disp = mFrame->StyleDisplay();
   if ((disp->mWillChangeBitField & NS_STYLE_WILL_CHANGE_TRANSFORM)) {
     return LAYER_ACTIVE;
   }
   // Expect the child display items to have this frame as their animated
   // geometry root (since it will be their reference frame). If they have a
   // different animated geometry root, we'll make this an active layer so the
   // animation can be accelerated.
   return RequiredLayerStateForChildren(aBuilder, aManager, aParameters,
     *mStoredList.GetChildren(), Frame());
 }
 bool nsDisplayTransform::ComputeVisibility(nsDisplayListBuilder *aBuilder,
                                              nsRegion *aVisibleRegion,
                                              const nsRect& aAllowVisibleRegionExpansion)
 {
   /* As we do this, we need to be sure to
    * untransform the visible rect, since we want everything that's painting to
    * think that it's painting in its original rectangular coordinate space.
    * If we can't untransform, take the entire overflow rect */
   nsRect untransformedVisibleRect;
   if (ShouldPrerenderTransformedContent(aBuilder, mFrame) ||
       !UntransformVisibleRect(aBuilder, &untransformedVisibleRect))
   {
     untransformedVisibleRect = mFrame->GetVisualOverflowRectRelativeToSelf();
   }
   nsRegion untransformedVisible = untransformedVisibleRect;
   // Call RecomputeVisiblity instead of ComputeVisibility since
   // nsDisplayItem::ComputeVisibility should only be called from
   // nsDisplayList::ComputeVisibility (which sets mVisibleRect on the item)
   mStoredList.RecomputeVisibility(aBuilder, &untransformedVisible);
   return true;
 }
 #ifdef DEBUG_HIT
 #include <time.h>
 #endif
 /* HitTest does some fun stuff with matrix transforms to obtain the answer. */
 void nsDisplayTransform::HitTest(nsDisplayListBuilder *aBuilder,
                                  const nsRect& aRect,
                                  HitTestState *aState,
                                  nsTArray<nsIFrame*> *aOutFrames)
 {
   /* Here's how this works:
    * 1. Get the matrix.  If it's singular, abort (clearly we didn't hit
    *    anything).
    * 2. Invert the matrix.
    * 3. Use it to transform the rect into the correct space.
    * 4. Pass that rect down through to the list's version of HitTest.
    */
   // GetTransform always operates in dev pixels.
   float factor = mFrame->PresContext()->AppUnitsPerDevPixel();
   gfx3DMatrix matrix = GetTransform();
   if (!IsFrameVisible(mFrame, matrix)) {
     return;
   }
   /* We want to go from transformed-space to regular space.
    * Thus we have to invert the matrix, which normally does
    * the reverse operation (e.g. regular->transformed)
    */
   bool snap;
   nsRect childBounds = mStoredList.GetBounds(aBuilder, &snap);
   gfxRect childGfxBounds(NSAppUnitsToFloatPixels(childBounds.x, factor),
                          NSAppUnitsToFloatPixels(childBounds.y, factor),
                          NSAppUnitsToFloatPixels(childBounds.width, factor),
                          NSAppUnitsToFloatPixels(childBounds.height, factor));
   /* Now, apply the transform and pass it down the channel. */
   nsRect resultingRect;
   if (aRect.width == 1 && aRect.height == 1) {
     // Magic width/height indicating we're hit testing a point, not a rect
     gfxPoint point;
     if (!matrix.UntransformPoint(gfxPoint(NSAppUnitsToFloatPixels(aRect.x, factor),
                                           NSAppUnitsToFloatPixels(aRect.y, factor)),
                                  childGfxBounds,
                                  &point)) {
       return;
     }
     resultingRect = nsRect(NSFloatPixelsToAppUnits(float(point.x), factor),
                            NSFloatPixelsToAppUnits(float(point.y), factor),
 , 1);
   } else {
     gfxRect originalRect(NSAppUnitsToFloatPixels(aRect.x, factor),
                          NSAppUnitsToFloatPixels(aRect.y, factor),
                          NSAppUnitsToFloatPixels(aRect.width, factor),
                          NSAppUnitsToFloatPixels(aRect.height, factor));
     gfxRect rect = matrix.UntransformBounds(originalRect, childGfxBounds);
     resultingRect = nsRect(NSFloatPixelsToAppUnits(float(rect.X()), factor),
                            NSFloatPixelsToAppUnits(float(rect.Y()), factor),
                            NSFloatPixelsToAppUnits(float(rect.Width()), factor),
                            NSFloatPixelsToAppUnits(float(rect.Height()), factor));
   }
   if (resultingRect.IsEmpty()) {
     return;
   }
 #ifdef DEBUG_HIT
   printf("Frame: %p\n", dynamic_cast<void *>(mFrame));
   printf("  Untransformed point: (%f, %f)\n", resultingRect.X(), resultingRect.Y());
   uint32_t originalFrameCount = aOutFrames.Length();
 #endif
   mStoredList.HitTest(aBuilder, resultingRect, aState, aOutFrames);
 #ifdef DEBUG_HIT
   if (originalFrameCount != aOutFrames.Length())
     printf("  Hit! Time: %f, first frame: %p\n", static_cast<double>(clock()),
            dynamic_cast<void *>(aOutFrames.ElementAt(0)));
   printf("=== end of hit test ===\n");
 #endif
 }
 float
 nsDisplayTransform::GetHitDepthAtPoint(nsDisplayListBuilder* aBuilder, const nsPoint& aPoint)
 {
   // GetTransform always operates in dev pixels.
   float factor = mFrame->PresContext()->AppUnitsPerDevPixel();
   gfx3DMatrix matrix = GetTransform();
   NS_ASSERTION(IsFrameVisible(mFrame, matrix), "We can't have hit a frame that isn't visible!");
   bool snap;
   nsRect childBounds = mStoredList.GetBounds(aBuilder, &snap);
   gfxRect childGfxBounds(NSAppUnitsToFloatPixels(childBounds.x, factor),
                          NSAppUnitsToFloatPixels(childBounds.y, factor),
                          NSAppUnitsToFloatPixels(childBounds.width, factor),
                          NSAppUnitsToFloatPixels(childBounds.height, factor));
   gfxPoint point;
   DebugOnly<bool> result = matrix.UntransformPoint(gfxPoint(NSAppUnitsToFloatPixels(aPoint.x, factor),
                                                             NSAppUnitsToFloatPixels(aPoint.y, factor)),
                                                    childGfxBounds,
                                                    &point);
   NS_ASSERTION(result, "Why are we trying to get the depth for a point we didn't hit?");
   gfxPoint3D transformed = matrix.Transform3D(gfxPoint3D(point.x, point.y, 0));
   return transformed.z;
 }
 /* The bounding rectangle for the object is the overflow rectangle translated
  * by the reference point.
  */
 nsRect nsDisplayTransform::GetBounds(nsDisplayListBuilder *aBuilder, bool* aSnap)
 {
   nsRect untransformedBounds =
     ShouldPrerenderTransformedContent(aBuilder, mFrame) ?
     mFrame->GetVisualOverflowRectRelativeToSelf() :
     mStoredList.GetBounds(aBuilder, aSnap);
   *aSnap = false;
   // GetTransform always operates in dev pixels.
   float factor = mFrame->PresContext()->AppUnitsPerDevPixel();
   return nsLayoutUtils::MatrixTransformRect(untransformedBounds,
                                             GetTransform(),
                                             factor);
 }
 /* The transform is opaque iff the transform consists solely of scales and
  * translations and if the underlying content is opaque.  Thus if the transform
  * is of the form
  *
  * |a c e|
  * |b d f|
  * |0 0 1|
  *
  * We need b and c to be zero.
  *
  * We also need to check whether the underlying opaque content completely fills
  * our visible rect. We use UntransformRect which expands to the axis-aligned
  * bounding rect, but that's OK since if
  * mStoredList.GetVisibleRect().Contains(untransformedVisible), then it
  * certainly contains the actual (non-axis-aligned) untransformed rect.
  */
 nsRegion nsDisplayTransform::GetOpaqueRegion(nsDisplayListBuilder *aBuilder,
                                              bool* aSnap)
 {
   *aSnap = false;
   nsRect untransformedVisible;
   // If we're going to prerender all our content, pretend like we
   // don't have opqaue content so that everything under us is rendered
   // as well.  That will increase graphics memory usage if our frame
   // covers the entire window, but it allows our transform to be
   // updated extremely cheaply, without invalidating any other
   // content.
   if (ShouldPrerenderTransformedContent(aBuilder, mFrame) ||
       !UntransformVisibleRect(aBuilder, &untransformedVisible)) {
       return nsRegion();
   }
   const gfx3DMatrix& matrix = GetTransform();
   nsRegion result;
   gfxMatrix matrix2d;
   bool tmpSnap;
   if (matrix.Is2D(&matrix2d) &&
       matrix2d.PreservesAxisAlignedRectangles() &&
       mStoredList.GetOpaqueRegion(aBuilder, &tmpSnap).Contains(untransformedVisible)) {
     result = mVisibleRect;
   }
   return result;
 }
 /* The transform is uniform if it fills the entire bounding rect and the
  * wrapped list is uniform.  See GetOpaqueRegion for discussion of why this
  * works.
  */
 bool nsDisplayTransform::IsUniform(nsDisplayListBuilder *aBuilder, nscolor* aColor)
 {
   nsRect untransformedVisible;
   if (!UntransformVisibleRect(aBuilder, &untransformedVisible)) {
     return false;
   }
   const gfx3DMatrix& matrix = GetTransform();
   gfxMatrix matrix2d;
   return matrix.Is2D(&matrix2d) &&
          matrix2d.PreservesAxisAlignedRectangles() &&
          mStoredList.GetVisibleRect().Contains(untransformedVisible) &&
          mStoredList.IsUniform(aBuilder, aColor);
 }
 /* If UNIFIED_CONTINUATIONS is defined, we can merge two display lists that
  * share the same underlying content.  Otherwise, doing so results in graphical
  * glitches.
  */
 #ifndef UNIFIED_CONTINUATIONS
 bool
 nsDisplayTransform::TryMerge(nsDisplayListBuilder *aBuilder,
                              nsDisplayItem *aItem)
 {
   return false;
 }
 #else
 bool
 nsDisplayTransform::TryMerge(nsDisplayListBuilder *aBuilder,
                              nsDisplayItem *aItem)
 {
   NS_PRECONDITION(aItem, "Why did you try merging with a null item?");
   NS_PRECONDITION(aBuilder, "Why did you try merging with a null builder?");
   /* Make sure that we're dealing with two transforms. */
   if (aItem->GetType() != TYPE_TRANSFORM)
     return false;
   /* Check to see that both frames are part of the same content. */
   if (aItem->Frame()->GetContent() != mFrame->GetContent())
     return false;
   if (aItem->GetClip() != GetClip())
     return false;
   /* Now, move everything over to this frame and signal that
    * we merged things!
    */
   mStoredList.MergeFrom(&static_cast<nsDisplayTransform*>(aItem)->mStoredList);
   return true;
 }
 #endif
 /* TransformRect takes in as parameters a rectangle (in app space) and returns
  * the smallest rectangle (in app space) containing the transformed image of
  * that rectangle.  That is, it takes the four corners of the rectangle,
  * transforms them according to the matrix associated with the specified frame,
  * then returns the smallest rectangle containing the four transformed points.
  *
  * @param aUntransformedBounds The rectangle (in app units) to transform.
  * @param aFrame The frame whose transformation should be applied.
  * @param aOrigin The delta from the frame origin to the coordinate space origin
  * @param aBoundsOverride (optional) Force the frame bounds to be the
  *        specified bounds.
  * @return The smallest rectangle containing the image of the transformed
  *         rectangle.
  */
 nsRect nsDisplayTransform::TransformRect(const nsRect &aUntransformedBounds,
                                          const nsIFrame* aFrame,
                                          const nsPoint &aOrigin,
                                          const nsRect* aBoundsOverride)
 {
   NS_PRECONDITION(aFrame, "Can't take the transform based on a null frame!");
   float factor = aFrame->PresContext()->AppUnitsPerDevPixel();
   return nsLayoutUtils::MatrixTransformRect
     (aUntransformedBounds,
      GetResultingTransformMatrix(aFrame, aOrigin, factor, aBoundsOverride),
      factor);
 }
 nsRect nsDisplayTransform::TransformRectOut(const nsRect &aUntransformedBounds,
                                             const nsIFrame* aFrame,
                                             const nsPoint &aOrigin,
                                             const nsRect* aBoundsOverride)
 {
   NS_PRECONDITION(aFrame, "Can't take the transform based on a null frame!");
   float factor = aFrame->PresContext()->AppUnitsPerDevPixel();
   return nsLayoutUtils::MatrixTransformRectOut
     (aUntransformedBounds,
      GetResultingTransformMatrix(aFrame, aOrigin, factor, aBoundsOverride),
      factor);
 }
 bool nsDisplayTransform::UntransformRect(const nsRect &aTransformedBounds,
                                          const nsRect &aChildBounds,
                                          const nsIFrame* aFrame,
                                          const nsPoint &aOrigin,
                                          nsRect *aOutRect)
 {
   NS_PRECONDITION(aFrame, "Can't take the transform based on a null frame!");
   float factor = aFrame->PresContext()->AppUnitsPerDevPixel();
   gfx3DMatrix transform = GetResultingTransformMatrix(aFrame, aOrigin, factor, nullptr);
   if (transform.IsSingular()) {
     return false;
   }
   gfxRect result(NSAppUnitsToFloatPixels(aTransformedBounds.x, factor),
                  NSAppUnitsToFloatPixels(aTransformedBounds.y, factor),
                  NSAppUnitsToFloatPixels(aTransformedBounds.width, factor),
                  NSAppUnitsToFloatPixels(aTransformedBounds.height, factor));
   gfxRect childGfxBounds(NSAppUnitsToFloatPixels(aChildBounds.x, factor),
                          NSAppUnitsToFloatPixels(aChildBounds.y, factor),
                          NSAppUnitsToFloatPixels(aChildBounds.width, factor),
                          NSAppUnitsToFloatPixels(aChildBounds.height, factor));
   result = transform.UntransformBounds(result, childGfxBounds);
   *aOutRect = nsLayoutUtils::RoundGfxRectToAppRect(result, factor);
   return true;
 }
 bool nsDisplayTransform::UntransformVisibleRect(nsDisplayListBuilder* aBuilder,
                                                 nsRect *aOutRect)
 {
   const gfx3DMatrix& matrix = GetTransform();
   if (matrix.IsSingular())
     return false;
   // GetTransform always operates in dev pixels.
   float factor = mFrame->PresContext()->AppUnitsPerDevPixel();
   gfxRect result(NSAppUnitsToFloatPixels(mVisibleRect.x, factor),
                  NSAppUnitsToFloatPixels(mVisibleRect.y, factor),
                  NSAppUnitsToFloatPixels(mVisibleRect.width, factor),
                  NSAppUnitsToFloatPixels(mVisibleRect.height, factor));
   bool snap;
   nsRect childBounds = mStoredList.GetBounds(aBuilder, &snap);
   gfxRect childGfxBounds(NSAppUnitsToFloatPixels(childBounds.x, factor),
                          NSAppUnitsToFloatPixels(childBounds.y, factor),
                          NSAppUnitsToFloatPixels(childBounds.width, factor),
                          NSAppUnitsToFloatPixels(childBounds.height, factor));
   /* We want to untransform the matrix, so invert the transformation first! */
   result = matrix.UntransformBounds(result, childGfxBounds);
   *aOutRect = nsLayoutUtils::RoundGfxRectToAppRect(result, factor);
   return true;
 }
 nsDisplaySVGEffects::nsDisplaySVGEffects(nsDisplayListBuilder* aBuilder,
                                          nsIFrame* aFrame, nsDisplayList* aList)
     : nsDisplayWrapList(aBuilder, aFrame, aList),
       mEffectsBounds(aFrame->GetVisualOverflowRectRelativeToSelf())
 {
   MOZ_COUNT_CTOR(nsDisplaySVGEffects);
 }
 #ifdef NS_BUILD_REFCNT_LOGGING
 nsDisplaySVGEffects::~nsDisplaySVGEffects()
 {
   MOZ_COUNT_DTOR(nsDisplaySVGEffects);
 }
 #endif
 nsRegion nsDisplaySVGEffects::GetOpaqueRegion(nsDisplayListBuilder* aBuilder,
                                               bool* aSnap)
 {
   *aSnap = false;
   return nsRegion();
 }
 void
 nsDisplaySVGEffects::HitTest(nsDisplayListBuilder* aBuilder, const nsRect& aRect,
                              HitTestState* aState, nsTArray<nsIFrame*> *aOutFrames)
 {
   nsPoint rectCenter(aRect.x + aRect.width / 2, aRect.y + aRect.height / 2);
   if (nsSVGIntegrationUtils::HitTestFrameForEffects(mFrame,
       rectCenter - ToReferenceFrame())) {
     mList.HitTest(aBuilder, aRect, aState, aOutFrames);
   }
 }
 void
 nsDisplaySVGEffects::PaintAsLayer(nsDisplayListBuilder* aBuilder,
                                   nsRenderingContext* aCtx,
                                   LayerManager* aManager)
 {
   nsSVGIntegrationUtils::PaintFramesWithEffects(aCtx, mFrame,
                                                 mVisibleRect,
                                                 aBuilder, aManager);
 }
 LayerState
 nsDisplaySVGEffects::GetLayerState(nsDisplayListBuilder* aBuilder,
                                    LayerManager* aManager,
                                    const ContainerLayerParameters& aParameters)
 {
   return LAYER_SVG_EFFECTS;
 }
 already_AddRefed<Layer>
 nsDisplaySVGEffects::BuildLayer(nsDisplayListBuilder* aBuilder,
                                 LayerManager* aManager,
                                 const ContainerLayerParameters& aContainerParameters)
 {
   const nsIContent* content = mFrame->GetContent();
   bool hasSVGLayout = (mFrame->GetStateBits() & NS_FRAME_SVG_LAYOUT);
   if (hasSVGLayout) {
     nsISVGChildFrame *svgChildFrame = do_QueryFrame(mFrame);
     if (!svgChildFrame || !mFrame->GetContent()->IsSVG()) {
       NS_ASSERTION(false, "why?");
       return nullptr;
     }
     if (!static_cast<const nsSVGElement*>(content)->HasValidDimensions()) {
       return nullptr; // The SVG spec says not to draw filters for this
     }
   }
   float opacity = mFrame->StyleDisplay()->mOpacity;
   if (opacity == 0.0f)
     return nullptr;
   nsIFrame* firstFrame =
     nsLayoutUtils::FirstContinuationOrIBSplitSibling(mFrame);
   nsSVGEffects::EffectProperties effectProperties =
     nsSVGEffects::GetEffectProperties(firstFrame);
   bool isOK = effectProperties.HasNoFilterOrHasValidFilter();
   effectProperties.GetClipPathFrame(&isOK);
   effectProperties.GetMaskFrame(&isOK);
   if (!isOK) {
     return nullptr;
   }
   ContainerLayerParameters newContainerParameters = aContainerParameters;
   if (effectProperties.HasValidFilter()) {
     newContainerParameters.mDisableSubpixelAntialiasingInDescendants = true;
   }
   nsRefPtr<ContainerLayer> container = aManager->GetLayerBuilder()->
     BuildContainerLayerFor(aBuilder, aManager, mFrame, this, mList,
                            newContainerParameters, nullptr);
   return container.forget();
 }
 bool nsDisplaySVGEffects::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                               nsRegion* aVisibleRegion,
                                               const nsRect& aAllowVisibleRegionExpansion) {
   nsPoint offset = ToReferenceFrame();
   nsRect dirtyRect =
     nsSVGIntegrationUtils::GetRequiredSourceForInvalidArea(mFrame,
                                                            mVisibleRect - offset) +
     offset;
   // Our children may be made translucent or arbitrarily deformed so we should
   // not allow them to subtract area from aVisibleRegion.
   nsRegion childrenVisible(dirtyRect);
   nsRect r = dirtyRect.Intersect(mList.GetBounds(aBuilder));
   mList.ComputeVisibilityForSublist(aBuilder, &childrenVisible, r, nsRect());
   return true;
 }
 bool nsDisplaySVGEffects::TryMerge(nsDisplayListBuilder* aBuilder, nsDisplayItem* aItem)
 {
   if (aItem->GetType() != TYPE_SVG_EFFECTS)
     return false;
   // items for the same content element should be merged into a single
   // compositing group
   // aItem->GetUnderlyingFrame() returns non-null because it's nsDisplaySVGEffects
   if (aItem->Frame()->GetContent() != mFrame->GetContent())
     return false;
   if (aItem->GetClip() != GetClip())
     return false;
   nsDisplaySVGEffects* other = static_cast<nsDisplaySVGEffects*>(aItem);
   MergeFromTrackingMergedFrames(other);
   mEffectsBounds.UnionRect(mEffectsBounds,
     other->mEffectsBounds + other->mFrame->GetOffsetTo(mFrame));
   return true;
 }
 #ifdef MOZ_DUMP_PAINTING
 void
 nsDisplaySVGEffects::PrintEffects(nsACString& aTo)
 {
   nsIFrame* firstFrame =
     nsLayoutUtils::FirstContinuationOrIBSplitSibling(mFrame);
   nsSVGEffects::EffectProperties effectProperties =
     nsSVGEffects::GetEffectProperties(firstFrame);
   bool isOK = true;
   nsSVGClipPathFrame *clipPathFrame = effectProperties.GetClipPathFrame(&isOK);
   bool first = true;
   aTo += " effects=(";
   if (mFrame->StyleDisplay()->mOpacity != 1.0f) {
     first = false;
     aTo += nsPrintfCString("opacity(%f)", mFrame->StyleDisplay()->mOpacity);
   }
   if (clipPathFrame) {
     if (!first) {
       aTo += ", ";
     }
     aTo += nsPrintfCString("clip(%s)", clipPathFrame->IsTrivial() ? "trivial" : "non-trivial");
     first = false;
   }
   if (effectProperties.HasValidFilter()) {
     if (!first) {
       aTo += ", ";
     }
     aTo += "filter";
     first = false;
   }
   if (effectProperties.GetMaskFrame(&isOK)) {
     if (!first) {
       aTo += ", ";
     }
     aTo += "mask";
   }
   aTo += ")";
 }
 #endif

The Tor Browser / annotate

layout/base/nsDisplayList.cpp@b8a032363ba2 (annotated)

layout/base/nsDisplayList.cpp