layout/base/PresShell.cpp
author Mike Hommey <mh+mozilla@glandium.org>
Wed, 16 Jan 2019 21:44:54 +0000
changeset 514172 e0fd6ca971ae522dd9398d49f564fe3f7263112b
parent 513947 918042a8eb34fe65335f96b5ae1226409361d4f6
child 514213 8e7a368e513a746650e08297b50c4d8ec971386c
permissions -rw-r--r--
Bug 1520377 - Replace/Inline subconfigure.{prefix_lines,execute_and_prefix}. r=nalexander Use an I/O wrapper on the configure output handler to add the "js/src>" prefix. Depends on D16643 Differential Revision: https://phabricator.services.mozilla.com/D16644

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/* a presentation of a document, part 2 */

#include "mozilla/PresShell.h"

#include "mozilla/dom/FontFaceSet.h"
#include "mozilla/ArrayUtils.h"
#include "mozilla/Attributes.h"
#include "mozilla/AutoRestore.h"
#include "mozilla/ContentIterator.h"
#include "mozilla/EventDispatcher.h"
#include "mozilla/EventStateManager.h"
#include "mozilla/EventStates.h"
#include "mozilla/IMEStateManager.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/dom/TabChild.h"
#include "mozilla/Likely.h"
#include "mozilla/Logging.h"
#include "mozilla/MouseEvents.h"
#include "mozilla/Sprintf.h"
#include "mozilla/StaticPrefs.h"
#include "mozilla/TextEvents.h"
#include "mozilla/TimeStamp.h"
#include "mozilla/TouchEvents.h"
#include "mozilla/UniquePtr.h"
#include "mozilla/Unused.h"
#include <algorithm>

#ifdef XP_WIN
#include "winuser.h"
#endif

#include "gfxContext.h"
#include "gfxPrefs.h"
#include "gfxUserFontSet.h"
#include "nsContentList.h"
#include "nsPresContext.h"
#include "nsIContent.h"
#include "nsIPresShellInlines.h"
#include "mozilla/dom/Element.h"
#include "mozilla/dom/PointerEventHandler.h"
#include "mozilla/dom/PopupBlocker.h"
#include "mozilla/dom/Document.h"
#include "nsAnimationManager.h"
#include "nsNameSpaceManager.h"  // for Pref-related rule management (bugs 22963,20760,31816)
#include "nsFrame.h"
#include "FrameLayerBuilder.h"
#include "nsViewManager.h"
#include "nsView.h"
#include "nsCRTGlue.h"
#include "prinrval.h"
#include "nsTArray.h"
#include "nsCOMArray.h"
#include "nsContainerFrame.h"
#include "mozilla/dom/Selection.h"
#include "nsGkAtoms.h"
#include "nsRange.h"
#include "nsWindowSizes.h"
#include "nsCOMPtr.h"
#include "nsReadableUtils.h"
#include "nsIPageSequenceFrame.h"
#include "nsIPermissionManager.h"
#include "nsIMozBrowserFrame.h"
#include "nsCaret.h"
#include "mozilla/AccessibleCaretEventHub.h"
#include "nsFrameManager.h"
#include "nsXPCOM.h"
#include "nsILayoutHistoryState.h"
#include "nsILineIterator.h"  // for ScrollContentIntoView
#include "PLDHashTable.h"
#include "mozilla/dom/Touch.h"
#include "mozilla/dom/TouchEvent.h"
#include "mozilla/dom/PointerEventBinding.h"
#include "mozilla/dom/ShadowIncludingTreeIterator.h"
#include "nsIObserverService.h"
#include "nsDocShell.h"  // for reflow observation
#include "nsIBaseWindow.h"
#include "nsError.h"
#include "nsLayoutUtils.h"
#include "nsViewportInfo.h"
#include "nsCSSRendering.h"
// for |#ifdef DEBUG| code
#include "prenv.h"
#include "nsDisplayList.h"
#include "nsRegion.h"
#include "nsAutoLayoutPhase.h"
#ifdef MOZ_GECKO_PROFILER
#include "AutoProfilerStyleMarker.h"
#endif
#ifdef MOZ_REFLOW_PERF
#include "nsFontMetrics.h"
#endif
#include "OverflowChangedTracker.h"
#include "PositionedEventTargeting.h"

#include "nsIReflowCallback.h"

#include "nsPIDOMWindow.h"
#include "nsFocusManager.h"
#include "nsIObjectFrame.h"
#include "nsIObjectLoadingContent.h"
#include "nsNetUtil.h"
#include "nsThreadUtils.h"
#include "nsStyleSheetService.h"
#include "gfxUtils.h"
#include "mozilla/SMILAnimationController.h"
#include "SVGContentUtils.h"
#include "SVGObserverUtils.h"
#include "SVGFragmentIdentifier.h"
#include "nsFrameSelection.h"

#include "mozilla/dom/Performance.h"
#include "nsRefreshDriver.h"
#include "nsDOMNavigationTiming.h"

// Drag & Drop, Clipboard
#include "nsIDocShellTreeItem.h"
#include "nsIURI.h"
#include "nsIScrollableFrame.h"
#include "nsITimer.h"
#ifdef ACCESSIBILITY
#include "nsAccessibilityService.h"
#include "mozilla/a11y/DocAccessible.h"
#ifdef DEBUG
#include "mozilla/a11y/Logging.h"
#endif
#endif

// For style data reconstruction
#include "nsStyleChangeList.h"
#include "nsCSSFrameConstructor.h"
#ifdef MOZ_XUL
#include "nsMenuFrame.h"
#include "nsTreeBodyFrame.h"
#include "XULTreeElement.h"
#include "nsMenuPopupFrame.h"
#include "nsTreeColumns.h"
#include "nsIDOMXULMultSelectCntrlEl.h"
#include "nsIDOMXULSelectCntrlItemEl.h"
#include "nsIDOMXULMenuListElement.h"
#include "nsXULElement.h"
#endif  // MOZ_XUL

#include "mozilla/layers/CompositorBridgeChild.h"
#include "ClientLayerManager.h"
#include "GeckoProfiler.h"
#include "gfxPlatform.h"
#include "Layers.h"
#include "LayerTreeInvalidation.h"
#include "mozilla/css/ImageLoader.h"
#include "mozilla/dom/DocumentTimeline.h"
#include "mozilla/dom/ScriptSettings.h"
#include "mozilla/ErrorResult.h"
#include "mozilla/Preferences.h"
#include "mozilla/Telemetry.h"
#include "nsCanvasFrame.h"
#include "nsIImageLoadingContent.h"
#include "nsImageFrame.h"
#include "nsIScreen.h"
#include "nsIScreenManager.h"
#include "nsPlaceholderFrame.h"
#include "nsTransitionManager.h"
#include "ChildIterator.h"
#include "mozilla/RestyleManager.h"
#include "nsIDragSession.h"
#include "nsIFrameInlines.h"
#include "mozilla/gfx/2D.h"
#include "nsSubDocumentFrame.h"
#include "nsQueryObject.h"
#include "nsLayoutStylesheetCache.h"
#include "mozilla/layers/InputAPZContext.h"
#include "mozilla/layers/FocusTarget.h"
#include "mozilla/layers/WebRenderLayerManager.h"
#include "mozilla/layers/WebRenderUserData.h"
#include "mozilla/layout/ScrollAnchorContainer.h"
#include "mozilla/ServoBindings.h"
#include "mozilla/ServoStyleSet.h"
#include "mozilla/StyleSheet.h"
#include "mozilla/StyleSheetInlines.h"
#include "mozilla/dom/ImageTracker.h"
#include "nsIDocShellTreeOwner.h"
#include "nsBindingManager.h"
#include "nsClassHashtable.h"
#include "nsHashKeys.h"
#include "VisualViewport.h"

#ifdef MOZ_TASK_TRACER
#include "GeckoTaskTracer.h"
using namespace mozilla::tasktracer;
#endif

#define ANCHOR_SCROLL_FLAGS \
  (nsIPresShell::SCROLL_OVERFLOW_HIDDEN | nsIPresShell::SCROLL_NO_PARENT_FRAMES)

// define the scalfactor of drag and drop images
// relative to the max screen height/width
#define RELATIVE_SCALEFACTOR 0.0925f

using namespace mozilla;
using namespace mozilla::css;
using namespace mozilla::dom;
using namespace mozilla::gfx;
using namespace mozilla::layers;
using namespace mozilla::gfx;
using namespace mozilla::layout;
using PaintFrameFlags = nsLayoutUtils::PaintFrameFlags;
typedef ScrollableLayerGuid::ViewID ViewID;

CapturingContentInfo nsIPresShell::gCaptureInfo = {
    false /* mAllowed */, false /* mPointerLock */,
    false /* mRetargetToElement */, false /* mPreventDrag */};
nsIContent* nsIPresShell::gKeyDownTarget;

// RangePaintInfo is used to paint ranges to offscreen buffers
struct RangePaintInfo {
  RefPtr<nsRange> mRange;
  nsDisplayListBuilder mBuilder;
  nsDisplayList mList;

  // offset of builder's reference frame to the root frame
  nsPoint mRootOffset;

  RangePaintInfo(nsRange* aRange, nsIFrame* aFrame)
      : mRange(aRange),
        mBuilder(aFrame, nsDisplayListBuilderMode::PAINTING, false) {
    MOZ_COUNT_CTOR(RangePaintInfo);
    mBuilder.BeginFrame();
  }

  ~RangePaintInfo() {
    mList.DeleteAll(&mBuilder);
    mBuilder.EndFrame();
    MOZ_COUNT_DTOR(RangePaintInfo);
  }
};

#undef NOISY

// ----------------------------------------------------------------------

#ifdef DEBUG
// Set the environment variable GECKO_VERIFY_REFLOW_FLAGS to one or
// more of the following flags (comma separated) for handy debug
// output.
static uint32_t gVerifyReflowFlags;

struct VerifyReflowFlags {
  const char* name;
  uint32_t bit;
};

static const VerifyReflowFlags gFlags[] = {
    // clang-format off
  { "verify",                VERIFY_REFLOW_ON },
  { "reflow",                VERIFY_REFLOW_NOISY },
  { "all",                   VERIFY_REFLOW_ALL },
  { "list-commands",         VERIFY_REFLOW_DUMP_COMMANDS },
  { "noisy-commands",        VERIFY_REFLOW_NOISY_RC },
  { "really-noisy-commands", VERIFY_REFLOW_REALLY_NOISY_RC },
  { "resize",                VERIFY_REFLOW_DURING_RESIZE_REFLOW },
    // clang-format on
};

#define NUM_VERIFY_REFLOW_FLAGS (sizeof(gFlags) / sizeof(gFlags[0]))

static void ShowVerifyReflowFlags() {
  printf("Here are the available GECKO_VERIFY_REFLOW_FLAGS:\n");
  const VerifyReflowFlags* flag = gFlags;
  const VerifyReflowFlags* limit = gFlags + NUM_VERIFY_REFLOW_FLAGS;
  while (flag < limit) {
    printf("  %s\n", flag->name);
    ++flag;
  }
  printf("Note: GECKO_VERIFY_REFLOW_FLAGS is a comma separated list of flag\n");
  printf("names (no whitespace)\n");
}
#endif

//========================================================================
//========================================================================
//========================================================================
#ifdef MOZ_REFLOW_PERF
class ReflowCountMgr;

static const char kGrandTotalsStr[] = "Grand Totals";

// Counting Class
class ReflowCounter {
 public:
  explicit ReflowCounter(ReflowCountMgr* aMgr = nullptr);
  ~ReflowCounter();

  void ClearTotals();
  void DisplayTotals(const char* aStr);
  void DisplayDiffTotals(const char* aStr);
  void DisplayHTMLTotals(const char* aStr);

  void Add() { mTotal++; }
  void Add(uint32_t aTotal) { mTotal += aTotal; }

  void CalcDiffInTotals();
  void SetTotalsCache();

  void SetMgr(ReflowCountMgr* aMgr) { mMgr = aMgr; }

  uint32_t GetTotal() { return mTotal; }

 protected:
  void DisplayTotals(uint32_t aTotal, const char* aTitle);
  void DisplayHTMLTotals(uint32_t aTotal, const char* aTitle);

  uint32_t mTotal;
  uint32_t mCacheTotal;

  ReflowCountMgr* mMgr;  // weak reference (don't delete)
};

// Counting Class
class IndiReflowCounter {
 public:
  explicit IndiReflowCounter(ReflowCountMgr* aMgr = nullptr)
      : mFrame(nullptr),
        mCount(0),
        mMgr(aMgr),
        mCounter(aMgr),
        mHasBeenOutput(false) {}
  virtual ~IndiReflowCounter() {}

  nsAutoString mName;
  nsIFrame* mFrame;  // weak reference (don't delete)
  int32_t mCount;

  ReflowCountMgr* mMgr;  // weak reference (don't delete)

  ReflowCounter mCounter;
  bool mHasBeenOutput;
};

//--------------------
// Manager Class
//--------------------
class ReflowCountMgr {
 public:
  ReflowCountMgr();
  virtual ~ReflowCountMgr();

  void ClearTotals();
  void ClearGrandTotals();
  void DisplayTotals(const char* aStr);
  void DisplayHTMLTotals(const char* aStr);
  void DisplayDiffsInTotals();

  void Add(const char* aName, nsIFrame* aFrame);
  ReflowCounter* LookUp(const char* aName);

  void PaintCount(const char* aName, gfxContext* aRenderingContext,
                  nsPresContext* aPresContext, nsIFrame* aFrame,
                  const nsPoint& aOffset, uint32_t aColor);

  FILE* GetOutFile() { return mFD; }

  void SetPresContext(nsPresContext* aPresContext) {
    mPresContext = aPresContext;  // weak reference
  }
  void SetPresShell(nsIPresShell* aPresShell) {
    mPresShell = aPresShell;  // weak reference
  }

  void SetDumpFrameCounts(bool aVal) { mDumpFrameCounts = aVal; }
  void SetDumpFrameByFrameCounts(bool aVal) { mDumpFrameByFrameCounts = aVal; }
  void SetPaintFrameCounts(bool aVal) { mPaintFrameByFrameCounts = aVal; }

  bool IsPaintingFrameCounts() { return mPaintFrameByFrameCounts; }

 protected:
  void DisplayTotals(uint32_t aTotal, uint32_t* aDupArray, char* aTitle);
  void DisplayHTMLTotals(uint32_t aTotal, uint32_t* aDupArray, char* aTitle);

  void DoGrandTotals();
  void DoIndiTotalsTree();

  // HTML Output Methods
  void DoGrandHTMLTotals();

  nsClassHashtable<nsCharPtrHashKey, ReflowCounter> mCounts;
  nsClassHashtable<nsCharPtrHashKey, IndiReflowCounter> mIndiFrameCounts;
  FILE* mFD;

  bool mDumpFrameCounts;
  bool mDumpFrameByFrameCounts;
  bool mPaintFrameByFrameCounts;

  bool mCycledOnce;

  // Root Frame for Individual Tracking
  nsPresContext* mPresContext;
  nsIPresShell* mPresShell;

  // ReflowCountMgr gReflowCountMgr;
};
#endif
//========================================================================

// comment out to hide caret
#define SHOW_CARET

// The upper bound on the amount of time to spend reflowing, in
// microseconds.  When this bound is exceeded and reflow commands are
// still queued up, a reflow event is posted.  The idea is for reflow
// to not hog the processor beyond the time specifed in
// gMaxRCProcessingTime.  This data member is initialized from the
// layout.reflow.timeslice pref.
#define NS_MAX_REFLOW_TIME 1000000
static int32_t gMaxRCProcessingTime = -1;

struct nsCallbackEventRequest {
  nsIReflowCallback* callback;
  nsCallbackEventRequest* next;
};

// ----------------------------------------------------------------------------
//
// NOTE(emilio): It'd be nice for this to assert that our document isn't in the
// bfcache, but font pref changes don't care about that, and maybe / probably
// shouldn't.
#ifdef DEBUG
#define ASSERT_REFLOW_SCHEDULED_STATE()                                       \
  {                                                                           \
    if (ObservingLayoutFlushes()) {                                           \
      MOZ_ASSERT(                                                             \
          mDocument->GetBFCacheEntry() ||                                     \
              mPresContext->RefreshDriver()->IsLayoutFlushObserver(this),     \
          "Unexpected state");                                                \
    } else {                                                                  \
      MOZ_ASSERT(!mPresContext->RefreshDriver()->IsLayoutFlushObserver(this), \
                 "Unexpected state");                                         \
    }                                                                         \
  }
#else
#define ASSERT_REFLOW_SCHEDULED_STATE() /* nothing */
#endif

class nsAutoCauseReflowNotifier {
 public:
  explicit nsAutoCauseReflowNotifier(PresShell* aShell) : mShell(aShell) {
    mShell->WillCauseReflow();
  }
  ~nsAutoCauseReflowNotifier() {
    // This check should not be needed. Currently the only place that seem
    // to need it is the code that deals with bug 337586.
    if (!mShell->mHaveShutDown) {
      mShell->DidCauseReflow();
    } else {
      nsContentUtils::RemoveScriptBlocker();
    }
  }

  PresShell* mShell;
};

class MOZ_STACK_CLASS nsPresShellEventCB : public EventDispatchingCallback {
 public:
  explicit nsPresShellEventCB(PresShell* aPresShell) : mPresShell(aPresShell) {}

  virtual void HandleEvent(EventChainPostVisitor& aVisitor) override {
    if (aVisitor.mPresContext && aVisitor.mEvent->mClass != eBasicEventClass) {
      if (aVisitor.mEvent->mMessage == eMouseDown ||
          aVisitor.mEvent->mMessage == eMouseUp) {
        // Mouse-up and mouse-down events call nsFrame::HandlePress/Release
        // which call GetContentOffsetsFromPoint which requires up-to-date
        // layout. Bring layout up-to-date now so that GetCurrentEventFrame()
        // below will return a real frame and we don't have to worry about
        // destroying it by flushing later.
        mPresShell->FlushPendingNotifications(FlushType::Layout);
      } else if (aVisitor.mEvent->mMessage == eWheel &&
                 aVisitor.mEventStatus != nsEventStatus_eConsumeNoDefault) {
        nsIFrame* frame = mPresShell->GetCurrentEventFrame();
        if (frame) {
          // chrome (including addons) should be able to know if content
          // handles both D3E "wheel" event and legacy mouse scroll events.
          // We should dispatch legacy mouse events before dispatching the
          // "wheel" event into system group.
          RefPtr<EventStateManager> esm =
              aVisitor.mPresContext->EventStateManager();
          esm->DispatchLegacyMouseScrollEvents(
              frame, aVisitor.mEvent->AsWheelEvent(), &aVisitor.mEventStatus);
        }
      }
      nsIFrame* frame = mPresShell->GetCurrentEventFrame();
      if (!frame && (aVisitor.mEvent->mMessage == eMouseUp ||
                     aVisitor.mEvent->mMessage == eTouchEnd)) {
        // Redirect BUTTON_UP and TOUCH_END events to the root frame to ensure
        // that capturing is released.
        frame = mPresShell->GetRootFrame();
      }
      if (frame) {
        frame->HandleEvent(aVisitor.mPresContext, aVisitor.mEvent->AsGUIEvent(),
                           &aVisitor.mEventStatus);
      }
    }
  }

  RefPtr<PresShell> mPresShell;
};

class nsBeforeFirstPaintDispatcher : public Runnable {
 public:
  explicit nsBeforeFirstPaintDispatcher(Document* aDocument)
      : mozilla::Runnable("nsBeforeFirstPaintDispatcher"),
        mDocument(aDocument) {}

  // Fires the "before-first-paint" event so that interested parties (right now,
  // the mobile browser) are aware of it.
  NS_IMETHOD Run() override {
    nsCOMPtr<nsIObserverService> observerService =
        mozilla::services::GetObserverService();
    if (observerService) {
      observerService->NotifyObservers(ToSupports(mDocument),
                                       "before-first-paint", nullptr);
    }
    return NS_OK;
  }

 private:
  RefPtr<Document> mDocument;
};

// This is a helper class to track whether the targeted frame is destroyed after
// dispatching pointer events. In that case, we need the original targeted
// content so that we can dispatch the mouse events to it.
class MOZ_STACK_CLASS AutoPointerEventTargetUpdater final {
 public:
  AutoPointerEventTargetUpdater(PresShell* aShell, WidgetEvent* aEvent,
                                nsIFrame* aFrame, nsIContent** aTargetContent) {
    MOZ_ASSERT(aEvent);
    if (!aTargetContent || aEvent->mClass != ePointerEventClass) {
      // Make the destructor happy.
      mTargetContent = nullptr;
      return;
    }
    MOZ_ASSERT(aShell);
    MOZ_ASSERT(aFrame);
    MOZ_ASSERT(!aFrame->GetContent() ||
               aShell->GetDocument() == aFrame->GetContent()->OwnerDoc());

    MOZ_ASSERT(PointerEventHandler::IsPointerEventEnabled());
    mShell = aShell;
    mWeakFrame = aFrame;
    mTargetContent = aTargetContent;
    aShell->mPointerEventTarget = aFrame->GetContent();
  }

  ~AutoPointerEventTargetUpdater() {
    if (!mTargetContent || !mShell || mWeakFrame.IsAlive()) {
      return;
    }
    mShell->mPointerEventTarget.swap(*mTargetContent);
  }

 private:
  RefPtr<PresShell> mShell;
  AutoWeakFrame mWeakFrame;
  nsIContent** mTargetContent;
};

void nsIPresShell::DirtyRootsList::Add(nsIFrame* aFrame) {
  // Is this root already scheduled for reflow?
  // FIXME: This could possibly be changed to a uniqueness assertion, with some
  // work in ResizeReflowIgnoreOverride (and maybe others?)
  if (mList.Contains(aFrame)) {
    // We don't expect frame to change depths.
    MOZ_ASSERT(aFrame->GetDepthInFrameTree() ==
               mList[mList.IndexOf(aFrame)].mDepth);
    return;
  }

  mList.InsertElementSorted(
      FrameAndDepth{aFrame, aFrame->GetDepthInFrameTree()},
      FrameAndDepth::CompareByReverseDepth{});
}

void nsIPresShell::DirtyRootsList::Remove(nsIFrame* aFrame) {
  mList.RemoveElement(aFrame);
}

nsIFrame* nsIPresShell::DirtyRootsList::PopShallowestRoot() {
  // List is sorted in order of decreasing depth, so there are no deeper
  // frames than the last one.
  const FrameAndDepth& lastFAD = mList.LastElement();
  nsIFrame* frame = lastFAD.mFrame;
  // We don't expect frame to change depths.
  MOZ_ASSERT(frame->GetDepthInFrameTree() == lastFAD.mDepth);
  mList.RemoveLastElement();
  return frame;
}

void nsIPresShell::DirtyRootsList::Clear() { mList.Clear(); }

bool nsIPresShell::DirtyRootsList::Contains(nsIFrame* aFrame) const {
  return mList.Contains(aFrame);
}

bool nsIPresShell::DirtyRootsList::IsEmpty() const { return mList.IsEmpty(); }

bool nsIPresShell::DirtyRootsList::FrameIsAncestorOfDirtyRoot(
    nsIFrame* aFrame) const {
  MOZ_ASSERT(aFrame);

  // Look for a path from any dirty roots to aFrame, following GetParent().
  // This check mirrors what FrameNeedsReflow() would have done if the reflow
  // root didn't get in the way.
  for (nsIFrame* dirtyFrame : mList) {
    do {
      if (dirtyFrame == aFrame) {
        return true;
      }
      dirtyFrame = dirtyFrame->GetParent();
    } while (dirtyFrame);
  }

  return false;
}

bool PresShell::sDisableNonTestMouseEvents = false;

mozilla::LazyLogModule PresShell::gLog("PresShell");

mozilla::TimeStamp PresShell::sLastInputCreated;
mozilla::TimeStamp PresShell::sLastInputProcessed;

bool PresShell::sProcessInteractable = false;

static bool gVerifyReflowEnabled;

bool nsIPresShell::GetVerifyReflowEnable() {
#ifdef DEBUG
  static bool firstTime = true;
  if (firstTime) {
    firstTime = false;
    char* flags = PR_GetEnv("GECKO_VERIFY_REFLOW_FLAGS");
    if (flags) {
      bool error = false;

      for (;;) {
        char* comma = PL_strchr(flags, ',');
        if (comma) *comma = '\0';

        bool found = false;
        const VerifyReflowFlags* flag = gFlags;
        const VerifyReflowFlags* limit = gFlags + NUM_VERIFY_REFLOW_FLAGS;
        while (flag < limit) {
          if (PL_strcasecmp(flag->name, flags) == 0) {
            gVerifyReflowFlags |= flag->bit;
            found = true;
            break;
          }
          ++flag;
        }

        if (!found) error = true;

        if (!comma) break;

        *comma = ',';
        flags = comma + 1;
      }

      if (error) ShowVerifyReflowFlags();
    }

    if (VERIFY_REFLOW_ON & gVerifyReflowFlags) {
      gVerifyReflowEnabled = true;

      printf("Note: verifyreflow is enabled");
      if (VERIFY_REFLOW_NOISY & gVerifyReflowFlags) {
        printf(" (noisy)");
      }
      if (VERIFY_REFLOW_ALL & gVerifyReflowFlags) {
        printf(" (all)");
      }
      if (VERIFY_REFLOW_DUMP_COMMANDS & gVerifyReflowFlags) {
        printf(" (show reflow commands)");
      }
      if (VERIFY_REFLOW_NOISY_RC & gVerifyReflowFlags) {
        printf(" (noisy reflow commands)");
        if (VERIFY_REFLOW_REALLY_NOISY_RC & gVerifyReflowFlags) {
          printf(" (REALLY noisy reflow commands)");
        }
      }
      printf("\n");
    }
  }
#endif
  return gVerifyReflowEnabled;
}

void nsIPresShell::SetVerifyReflowEnable(bool aEnabled) {
  gVerifyReflowEnabled = aEnabled;
}

void nsIPresShell::AddAutoWeakFrame(AutoWeakFrame* aWeakFrame) {
  if (aWeakFrame->GetFrame()) {
    aWeakFrame->GetFrame()->AddStateBits(NS_FRAME_EXTERNAL_REFERENCE);
  }
  aWeakFrame->SetPreviousWeakFrame(mAutoWeakFrames);
  mAutoWeakFrames = aWeakFrame;
}

void nsIPresShell::AddWeakFrame(WeakFrame* aWeakFrame) {
  if (aWeakFrame->GetFrame()) {
    aWeakFrame->GetFrame()->AddStateBits(NS_FRAME_EXTERNAL_REFERENCE);
  }
  MOZ_ASSERT(!mWeakFrames.GetEntry(aWeakFrame));
  mWeakFrames.PutEntry(aWeakFrame);
}

void nsIPresShell::RemoveAutoWeakFrame(AutoWeakFrame* aWeakFrame) {
  if (mAutoWeakFrames == aWeakFrame) {
    mAutoWeakFrames = aWeakFrame->GetPreviousWeakFrame();
    return;
  }
  AutoWeakFrame* nextWeak = mAutoWeakFrames;
  while (nextWeak && nextWeak->GetPreviousWeakFrame() != aWeakFrame) {
    nextWeak = nextWeak->GetPreviousWeakFrame();
  }
  if (nextWeak) {
    nextWeak->SetPreviousWeakFrame(aWeakFrame->GetPreviousWeakFrame());
  }
}

void nsIPresShell::RemoveWeakFrame(WeakFrame* aWeakFrame) {
  MOZ_ASSERT(mWeakFrames.GetEntry(aWeakFrame));
  mWeakFrames.RemoveEntry(aWeakFrame);
}

already_AddRefed<nsFrameSelection> nsIPresShell::FrameSelection() {
  RefPtr<nsFrameSelection> ret = mSelection;
  return ret.forget();
}

//----------------------------------------------------------------------

static bool sSynthMouseMove = true;
static uint32_t sNextPresShellId;

/* static */ bool PresShell::AccessibleCaretEnabled(nsIDocShell* aDocShell) {
  // If the pref forces it on, then enable it.
  if (StaticPrefs::layout_accessiblecaret_enabled()) {
    return true;
  }
  // If the touch pref is on, and touch events are enabled (this depends
  // on the specific device running), then enable it.
  if (StaticPrefs::layout_accessiblecaret_enabled_on_touch() &&
      dom::TouchEvent::PrefEnabled(aDocShell)) {
    return true;
  }
  // Otherwise, disabled.
  return false;
}

nsIPresShell::nsIPresShell()
    : mViewManager(nullptr),
      mFrameManager(nullptr),
#ifdef ACCESSIBILITY
      mDocAccessible(nullptr),
#endif
#ifdef DEBUG
      mDrawEventTargetFrame(nullptr),
#endif
      mPaintCount(0),
      mAutoWeakFrames(nullptr),
      mCanvasBackgroundColor(NS_RGBA(0, 0, 0, 0)),
      mSelectionFlags(0),
      mChangeNestCount(0),
      mRenderFlags(0),
      mDidInitialize(false),
      mIsDestroying(false),
      mIsReflowing(false),
      mIsObservingDocument(false),
      mIsDocumentGone(false),
      mPaintingSuppressed(false),
      mIsActive(false),
      mFrozen(false),
      mIsFirstPaint(false),
      mObservesMutationsForPrint(false),
      mWasLastReflowInterrupted(false),
      mVisualViewportSizeSet(false),
      mNeedLayoutFlush(true),
      mNeedStyleFlush(true),
      mObservingStyleFlushes(false),
      mObservingLayoutFlushes(false),
      mResizeEventPending(false),
      mNeedThrottledAnimationFlush(true),
      mFontSizeInflationForceEnabled(false),
      mFontSizeInflationDisabledInMasterProcess(false),
      mFontSizeInflationEnabled(false),
      mPaintingIsFrozen(false),
      mIsNeverPainting(false),
      mResolutionUpdated(false),
      mPresShellId(0),
      mFontSizeInflationEmPerLine(0),
      mFontSizeInflationMinTwips(0),
      mFontSizeInflationLineThreshold(0),
      mInFlush(false),
      mCurrentEventFrame(nullptr) {
}

PresShell::PresShell()
    : mCaretEnabled(false),
#ifdef DEBUG
      mInVerifyReflow(false),
      mCurrentReflowRoot(nullptr),
#endif
#ifdef MOZ_REFLOW_PERF
      mReflowCountMgr(nullptr),
#endif
      mMouseLocation(NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE),
      mFirstCallbackEventRequest(nullptr),
      mLastCallbackEventRequest(nullptr),
      mLastReflowStart(0.0),
      mLastAnchorScrollPositionY(0),
      mActiveSuppressDisplayport(0),
      mAPZFocusSequenceNumber(0),
      mDocumentLoading(false),
      mIgnoreFrameDestruction(false),
      mHaveShutDown(false),
      mLastRootReflowHadUnconstrainedBSize(false),
      mNoDelayedMouseEvents(false),
      mNoDelayedKeyEvents(false),
      mShouldUnsuppressPainting(false),
      mApproximateFrameVisibilityVisited(false),
      mNextPaintCompressed(false),
      mHasCSSBackgroundColor(false),
      mIsLastChromeOnlyEscapeKeyConsumed(false),
      mHasReceivedPaintMessage(false),
      mIsLastKeyDownCanceled(false),
      mHasHandledUserInput(false),
      mForceDispatchKeyPressEventsForNonPrintableKeys(false),
      mForceUseLegacyKeyCodeAndCharCodeValues(false),
      mInitializedWithKeyPressEventDispatchingBlacklist(false) {
  MOZ_LOG(gLog, LogLevel::Debug, ("PresShell::PresShell this=%p", this));

#ifdef MOZ_REFLOW_PERF
  mReflowCountMgr = MakeUnique<ReflowCountMgr>();
  mReflowCountMgr->SetPresContext(mPresContext);
  mReflowCountMgr->SetPresShell(this);
#endif
  mLastOSWake = mLoadBegin = TimeStamp::Now();

  mSelectionFlags =
      nsISelectionDisplay::DISPLAY_TEXT | nsISelectionDisplay::DISPLAY_IMAGES;
  mIsActive = true;
  // FIXME/bug 735029: find a better solution to this problem
  mIsFirstPaint = true;
  mPresShellId = sNextPresShellId++;
  mFrozen = false;
  mRenderFlags = 0;

  mVisualViewportSizeSet = false;

  static bool addedSynthMouseMove = false;
  if (!addedSynthMouseMove) {
    Preferences::AddBoolVarCache(&sSynthMouseMove,
                                 "layout.reflow.synthMouseMove", true);
    addedSynthMouseMove = true;
  }
  PointerEventHandler::Initialize();
  mPaintingIsFrozen = false;
  mHasCSSBackgroundColor = true;
  mIsLastChromeOnlyEscapeKeyConsumed = false;
  mHasReceivedPaintMessage = false;
}

NS_IMPL_ISUPPORTS(PresShell, nsIPresShell, nsIDocumentObserver,
                  nsISelectionController, nsISelectionDisplay, nsIObserver,
                  nsISupportsWeakReference, nsIMutationObserver)

PresShell::~PresShell() {
  MOZ_LOG(gLog, LogLevel::Debug, ("PresShell::~PresShell this=%p", this));

  if (!mHaveShutDown) {
    MOZ_ASSERT_UNREACHABLE("Someone did not call nsIPresShell::destroy");
    Destroy();
  }

  NS_ASSERTION(mCurrentEventContentStack.Count() == 0,
               "Huh, event content left on the stack in pres shell dtor!");
  NS_ASSERTION(mFirstCallbackEventRequest == nullptr &&
                   mLastCallbackEventRequest == nullptr,
               "post-reflow queues not empty.  This means we're leaking");

  // Verify that if painting was frozen, but we're being removed from the tree,
  // that we now re-enable painting on our refresh driver, since it may need to
  // be re-used by another presentation.
  if (mPaintingIsFrozen) {
    mPresContext->RefreshDriver()->Thaw();
  }

  MOZ_ASSERT(mAllocatedPointers.IsEmpty(),
             "Some pres arena objects were not freed");

  mStyleSet = nullptr;
  mFrameManager = nullptr;
  mFrameConstructor = nullptr;

  mCurrentEventContent = nullptr;
}

/**
 * Initialize the presentation shell. Create view manager and style
 * manager.
 * Note this can't be merged into our constructor because caret initialization
 * calls AddRef() on us.
 */
void PresShell::Init(Document* aDocument, nsPresContext* aPresContext,
                     nsViewManager* aViewManager,
                     UniquePtr<ServoStyleSet> aStyleSet) {
  MOZ_ASSERT(aDocument, "null ptr");
  MOZ_ASSERT(aPresContext, "null ptr");
  MOZ_ASSERT(aViewManager, "null ptr");
  MOZ_ASSERT(!mDocument, "already initialized");

  if (!aDocument || !aPresContext || !aViewManager || mDocument) {
    return;
  }

  mDocument = aDocument;
  mViewManager = aViewManager;

  // mDocument is now set.  It might have a display document whose "need layout/
  // style" flush flags are not set, but ours will be set.  To keep these
  // consistent, call the flag setting functions to propagate those flags up
  // to the display document.
  SetNeedLayoutFlush();
  SetNeedStyleFlush();

  // Create our frame constructor.
  mFrameConstructor = MakeUnique<nsCSSFrameConstructor>(mDocument, this);

  mFrameManager = mFrameConstructor.get();

  // The document viewer owns both view manager and pres shell.
  mViewManager->SetPresShell(this);

  // Bind the context to the presentation shell.
  mPresContext = aPresContext;
  mPresContext->AttachShell(this);

  // Now we can initialize the style set. Make sure to set the member before
  // calling Init, since various subroutines need to find the style set off
  // the PresContext during initialization.
  mStyleSet = std::move(aStyleSet);
  mStyleSet->Init(aPresContext);

  // Notify our prescontext that it now has a compatibility mode.  Note that
  // this MUST happen after we set up our style set but before we create any
  // frames.
  mPresContext->CompatibilityModeChanged();

  // Add the preference style sheet.
  UpdatePreferenceStyles();

  bool accessibleCaretEnabled =
      AccessibleCaretEnabled(mDocument->GetDocShell());
  if (accessibleCaretEnabled) {
    // Need to happen before nsFrameSelection has been set up.
    mAccessibleCaretEventHub = new AccessibleCaretEventHub(this);
  }

  mSelection = new nsFrameSelection();

  RefPtr<nsFrameSelection> frameSelection = mSelection;
  frameSelection->Init(this, nullptr, accessibleCaretEnabled);

  // Important: this has to happen after the selection has been set up
#ifdef SHOW_CARET
  // make the caret
  mCaret = new nsCaret();
  mCaret->Init(this);
  mOriginalCaret = mCaret;

  // SetCaretEnabled(true);       // make it show in browser windows
#endif
  // set up selection to be displayed in document
  // Don't enable selection for print media
  nsPresContext::nsPresContextType type = aPresContext->Type();
  if (type != nsPresContext::eContext_PrintPreview &&
      type != nsPresContext::eContext_Print)
    SetDisplaySelection(nsISelectionController::SELECTION_DISABLED);

  if (gMaxRCProcessingTime == -1) {
    gMaxRCProcessingTime =
        Preferences::GetInt("layout.reflow.timeslice", NS_MAX_REFLOW_TIME);
  }

  if (nsStyleSheetService* ss = nsStyleSheetService::GetInstance()) {
    ss->RegisterPresShell(this);
  }

  {
    nsCOMPtr<nsIObserverService> os = mozilla::services::GetObserverService();
    if (os) {
#ifdef MOZ_XUL
      os->AddObserver(this, "chrome-flush-skin-caches", false);
#endif
      os->AddObserver(this, "memory-pressure", false);
      os->AddObserver(this, NS_WIDGET_WAKE_OBSERVER_TOPIC, false);
      if (XRE_IsParentProcess() && !sProcessInteractable) {
        os->AddObserver(this, "sessionstore-one-or-no-tab-restored", false);
      }
      os->AddObserver(this, "font-info-updated", false);
    }
  }

#ifdef MOZ_REFLOW_PERF
  if (mReflowCountMgr) {
    bool paintFrameCounts =
        Preferences::GetBool("layout.reflow.showframecounts");

    bool dumpFrameCounts =
        Preferences::GetBool("layout.reflow.dumpframecounts");

    bool dumpFrameByFrameCounts =
        Preferences::GetBool("layout.reflow.dumpframebyframecounts");

    mReflowCountMgr->SetDumpFrameCounts(dumpFrameCounts);
    mReflowCountMgr->SetDumpFrameByFrameCounts(dumpFrameByFrameCounts);
    mReflowCountMgr->SetPaintFrameCounts(paintFrameCounts);
  }
#endif

  if (mDocument->HasAnimationController()) {
    SMILAnimationController* animCtrl = mDocument->GetAnimationController();
    animCtrl->NotifyRefreshDriverCreated(GetPresContext()->RefreshDriver());
  }

  for (DocumentTimeline* timeline : mDocument->Timelines()) {
    timeline->NotifyRefreshDriverCreated(GetPresContext()->RefreshDriver());
  }

  // Get our activeness from the docShell.
  QueryIsActive();

  // Setup our font inflation preferences.
  mFontSizeInflationEmPerLine = nsLayoutUtils::FontSizeInflationEmPerLine();
  mFontSizeInflationMinTwips = nsLayoutUtils::FontSizeInflationMinTwips();
  mFontSizeInflationLineThreshold =
      nsLayoutUtils::FontSizeInflationLineThreshold();
  mFontSizeInflationForceEnabled =
      nsLayoutUtils::FontSizeInflationForceEnabled();
  mFontSizeInflationDisabledInMasterProcess =
      nsLayoutUtils::FontSizeInflationDisabledInMasterProcess();
  // We'll compute the font size inflation state in Initialize(), when we know
  // the document type.

  mTouchManager.Init(this, mDocument);

  if (mPresContext->IsRootContentDocument()) {
    mZoomConstraintsClient = new ZoomConstraintsClient();
    mZoomConstraintsClient->Init(this, mDocument);

    // We call this to create mMobileViewportManager, if it is needed.
    UpdateViewportOverridden(false);
  }
}

enum TextPerfLogType { eLog_reflow, eLog_loaddone, eLog_totals };

static void LogTextPerfStats(gfxTextPerfMetrics* aTextPerf,
                             PresShell* aPresShell,
                             const gfxTextPerfMetrics::TextCounts& aCounts,
                             float aTime, TextPerfLogType aLogType,
                             const char* aURL) {
  LogModule* tpLog = gfxPlatform::GetLog(eGfxLog_textperf);

  // ignore XUL contexts unless at debug level
  mozilla::LogLevel logLevel = LogLevel::Warning;
  if (aCounts.numContentTextRuns == 0) {
    logLevel = LogLevel::Debug;
  }

  if (!MOZ_LOG_TEST(tpLog, logLevel)) {
    return;
  }

  char prefix[256];

  switch (aLogType) {
    case eLog_reflow:
      SprintfLiteral(prefix, "(textperf-reflow) %p time-ms: %7.0f", aPresShell,
                     aTime);
      break;
    case eLog_loaddone:
      SprintfLiteral(prefix, "(textperf-loaddone) %p time-ms: %7.0f",
                     aPresShell, aTime);
      break;
    default:
      MOZ_ASSERT(aLogType == eLog_totals, "unknown textperf log type");
      SprintfLiteral(prefix, "(textperf-totals) %p", aPresShell);
  }

  double hitRatio = 0.0;
  uint32_t lookups = aCounts.wordCacheHit + aCounts.wordCacheMiss;
  if (lookups) {
    hitRatio = double(aCounts.wordCacheHit) / double(lookups);
  }

  if (aLogType == eLog_loaddone) {
    MOZ_LOG(
        tpLog, logLevel,
        ("%s reflow: %d chars: %d "
         "[%s] "
         "content-textruns: %d chrome-textruns: %d "
         "max-textrun-len: %d "
         "word-cache-lookups: %d word-cache-hit-ratio: %4.3f "
         "word-cache-space: %d word-cache-long: %d "
         "pref-fallbacks: %d system-fallbacks: %d "
         "textruns-const: %d textruns-destr: %d "
         "generic-lookups: %d "
         "cumulative-textruns-destr: %d\n",
         prefix, aTextPerf->reflowCount, aCounts.numChars, (aURL ? aURL : ""),
         aCounts.numContentTextRuns, aCounts.numChromeTextRuns,
         aCounts.maxTextRunLen, lookups, hitRatio, aCounts.wordCacheSpaceRules,
         aCounts.wordCacheLong, aCounts.fallbackPrefs, aCounts.fallbackSystem,
         aCounts.textrunConst, aCounts.textrunDestr, aCounts.genericLookups,
         aTextPerf->cumulative.textrunDestr));
  } else {
    MOZ_LOG(
        tpLog, logLevel,
        ("%s reflow: %d chars: %d "
         "content-textruns: %d chrome-textruns: %d "
         "max-textrun-len: %d "
         "word-cache-lookups: %d word-cache-hit-ratio: %4.3f "
         "word-cache-space: %d word-cache-long: %d "
         "pref-fallbacks: %d system-fallbacks: %d "
         "textruns-const: %d textruns-destr: %d "
         "generic-lookups: %d "
         "cumulative-textruns-destr: %d\n",
         prefix, aTextPerf->reflowCount, aCounts.numChars,
         aCounts.numContentTextRuns, aCounts.numChromeTextRuns,
         aCounts.maxTextRunLen, lookups, hitRatio, aCounts.wordCacheSpaceRules,
         aCounts.wordCacheLong, aCounts.fallbackPrefs, aCounts.fallbackSystem,
         aCounts.textrunConst, aCounts.textrunDestr, aCounts.genericLookups,
         aTextPerf->cumulative.textrunDestr));
  }
}

void PresShell::Destroy() {
  // Do not add code before this line please!
  if (mHaveShutDown) {
    return;
  }

  NS_ASSERTION(!nsContentUtils::IsSafeToRunScript(),
               "destroy called on presshell while scripts not blocked");

  AUTO_PROFILER_LABEL("PresShell::Destroy", LAYOUT);

  // dump out cumulative text perf metrics
  gfxTextPerfMetrics* tp;
  if (mPresContext && (tp = mPresContext->GetTextPerfMetrics())) {
    tp->Accumulate();
    if (tp->cumulative.numChars > 0) {
      LogTextPerfStats(tp, this, tp->cumulative, 0.0, eLog_totals, nullptr);
    }
  }
  if (mPresContext) {
    const bool mayFlushUserFontSet = false;
    gfxUserFontSet* fs = mPresContext->GetUserFontSet(mayFlushUserFontSet);
    if (fs) {
      uint32_t fontCount;
      uint64_t fontSize;
      fs->GetLoadStatistics(fontCount, fontSize);
      Telemetry::Accumulate(Telemetry::WEBFONT_PER_PAGE, fontCount);
      Telemetry::Accumulate(Telemetry::WEBFONT_SIZE_PER_PAGE,
                            uint32_t(fontSize / 1024));
    } else {
      Telemetry::Accumulate(Telemetry::WEBFONT_PER_PAGE, 0);
      Telemetry::Accumulate(Telemetry::WEBFONT_SIZE_PER_PAGE, 0);
    }
  }

#ifdef MOZ_REFLOW_PERF
  DumpReflows();
  mReflowCountMgr = nullptr;
#endif

  if (mZoomConstraintsClient) {
    mZoomConstraintsClient->Destroy();
    mZoomConstraintsClient = nullptr;
  }
  if (mMobileViewportManager) {
    mMobileViewportManager->Destroy();
    mMobileViewportManager = nullptr;
  }

#ifdef ACCESSIBILITY
  if (mDocAccessible) {
#ifdef DEBUG
    if (a11y::logging::IsEnabled(a11y::logging::eDocDestroy))
      a11y::logging::DocDestroy("presshell destroyed", mDocument);
#endif

    mDocAccessible->Shutdown();
    mDocAccessible = nullptr;
  }
#endif  // ACCESSIBILITY

  MaybeReleaseCapturingContent();

  if (gKeyDownTarget && gKeyDownTarget->OwnerDoc() == mDocument) {
    NS_RELEASE(gKeyDownTarget);
  }

  if (mContentToScrollTo) {
    mContentToScrollTo->DeleteProperty(nsGkAtoms::scrolling);
    mContentToScrollTo = nullptr;
  }

  if (mPresContext) {
    // We need to notify the destroying the nsPresContext to ESM for
    // suppressing to use from ESM.
    mPresContext->EventStateManager()->NotifyDestroyPresContext(mPresContext);
  }

  if (nsStyleSheetService* ss = nsStyleSheetService::GetInstance()) {
    ss->UnregisterPresShell(this);
  }

  {
    nsCOMPtr<nsIObserverService> os = mozilla::services::GetObserverService();
    if (os) {
#ifdef MOZ_XUL
      os->RemoveObserver(this, "chrome-flush-skin-caches");
#endif
      os->RemoveObserver(this, "memory-pressure");
      os->RemoveObserver(this, NS_WIDGET_WAKE_OBSERVER_TOPIC);
      if (XRE_IsParentProcess()) {
        os->RemoveObserver(this, "sessionstore-one-or-no-tab-restored");
      }
      os->RemoveObserver(this, "font-info-updated");
    }
  }

  // If our paint suppression timer is still active, kill it.
  if (mPaintSuppressionTimer) {
    mPaintSuppressionTimer->Cancel();
    mPaintSuppressionTimer = nullptr;
  }

  // Same for our reflow continuation timer
  if (mReflowContinueTimer) {
    mReflowContinueTimer->Cancel();
    mReflowContinueTimer = nullptr;
  }

  if (mDelayedPaintTimer) {
    mDelayedPaintTimer->Cancel();
    mDelayedPaintTimer = nullptr;
  }

  mSynthMouseMoveEvent.Revoke();

  mUpdateApproximateFrameVisibilityEvent.Revoke();

  ClearApproximatelyVisibleFramesList(Some(OnNonvisible::DISCARD_IMAGES));

  if (mCaret) {
    mCaret->Terminate();
    mCaret = nullptr;
  }

  if (mSelection) {
    RefPtr<nsFrameSelection> frameSelection = mSelection;
    frameSelection->DisconnectFromPresShell();
  }

  if (mAccessibleCaretEventHub) {
    mAccessibleCaretEventHub->Terminate();
    mAccessibleCaretEventHub = nullptr;
  }

  // release our pref style sheet, if we have one still
  //
  // FIXME(emilio): Why do we need to do this? The stylist is getting nixed with
  // us anyway.
  RemovePreferenceStyles();

  mIsDestroying = true;

  // We can't release all the event content in
  // mCurrentEventContentStack here since there might be code on the
  // stack that will release the event content too. Double release
  // bad!

  // The frames will be torn down, so remove them from the current
  // event frame stack (since they'd be dangling references if we'd
  // leave them in) and null out the mCurrentEventFrame pointer as
  // well.

  mCurrentEventFrame = nullptr;

  int32_t i, count = mCurrentEventFrameStack.Length();
  for (i = 0; i < count; i++) {
    mCurrentEventFrameStack[i] = nullptr;
  }

  mFramesToDirty.Clear();
  mDirtyScrollAnchorContainers.Clear();

  if (mViewManager) {
    // Clear the view manager's weak pointer back to |this| in case it
    // was leaked.
    mViewManager->SetPresShell(nullptr);
    mViewManager = nullptr;
  }

  // mFrameArena will be destroyed soon.  Clear out any ArenaRefPtrs
  // pointing to objects in the arena now.  This is done:
  //
  //   (a) before mFrameArena's destructor runs so that our
  //       mAllocatedPointers becomes empty and doesn't trip the assertion
  //       in ~PresShell,
  //   (b) before the mPresContext->DetachShell() below, so
  //       that when we clear the ArenaRefPtrs they'll still be able to
  //       get back to this PresShell to deregister themselves (e.g. note
  //       how ComputedStyle::Arena returns the PresShell got from its
  //       rule node's nsPresContext, which would return null if we'd already
  //       called mPresContext->DetachShell()), and
  //   (c) before the mStyleSet->BeginShutdown() call just below, so that
  //       the ComputedStyles don't complain they're being destroyed later
  //       than the rule tree is.
  mFrameArena.ClearArenaRefPtrs();

  mStyleSet->BeginShutdown();
  nsRefreshDriver* rd = GetPresContext()->RefreshDriver();

  // This shell must be removed from the document before the frame
  // hierarchy is torn down to avoid finding deleted frames through
  // this presshell while the frames are being torn down
  if (mDocument) {
    NS_ASSERTION(mDocument->GetShell() == this, "Wrong shell?");
    mDocument->ClearServoRestyleRoot();
    mDocument->DeleteShell();

    if (mDocument->HasAnimationController()) {
      mDocument->GetAnimationController()->NotifyRefreshDriverDestroying(rd);
    }
    for (DocumentTimeline* timeline : mDocument->Timelines()) {
      timeline->NotifyRefreshDriverDestroying(rd);
    }
  }

  if (mPresContext) {
    rd->CancelPendingAnimationEvents(mPresContext->AnimationEventDispatcher());
  }

  // Revoke any pending events.  We need to do this and cancel pending reflows
  // before we destroy the frame manager, since apparently frame destruction
  // sometimes spins the event queue when plug-ins are involved(!).
  StopObservingRefreshDriver();

  if (rd->GetPresContext() == GetPresContext()) {
    rd->RevokeViewManagerFlush();
  }

  CancelAllPendingReflows();
  CancelPostedReflowCallbacks();

  // Destroy the frame manager. This will destroy the frame hierarchy
  mFrameConstructor->WillDestroyFrameTree();

  NS_WARNING_ASSERTION(!mAutoWeakFrames && mWeakFrames.IsEmpty(),
                       "Weak frames alive after destroying FrameManager");
  while (mAutoWeakFrames) {
    mAutoWeakFrames->Clear(this);
  }
  nsTArray<WeakFrame*> toRemove(mWeakFrames.Count());
  for (auto iter = mWeakFrames.Iter(); !iter.Done(); iter.Next()) {
    toRemove.AppendElement(iter.Get()->GetKey());
  }
  for (WeakFrame* weakFrame : toRemove) {
    weakFrame->Clear(this);
  }

  // Let the style set do its cleanup.
  mStyleSet->Shutdown();

  if (mPresContext) {
    // We hold a reference to the pres context, and it holds a weak link back
    // to us. To avoid the pres context having a dangling reference, set its
    // pres shell to nullptr
    mPresContext->DetachShell();

    // Clear the link handler (weak reference) as well
    mPresContext->SetLinkHandler(nullptr);
  }

  mHaveShutDown = true;

  mTouchManager.Destroy();
}

void nsIPresShell::StopObservingRefreshDriver() {
  nsRefreshDriver* rd = mPresContext->RefreshDriver();
  if (mResizeEventPending) {
    rd->RemoveResizeEventFlushObserver(this);
  }
  if (mObservingLayoutFlushes) {
    rd->RemoveLayoutFlushObserver(this);
  }
  if (mObservingStyleFlushes) {
    rd->RemoveStyleFlushObserver(this);
  }
}

void nsIPresShell::StartObservingRefreshDriver() {
  nsRefreshDriver* rd = mPresContext->RefreshDriver();
  if (mResizeEventPending) {
    rd->AddResizeEventFlushObserver(this);
  }
  if (mObservingLayoutFlushes) {
    rd->AddLayoutFlushObserver(this);
  }
  if (mObservingStyleFlushes) {
    rd->AddStyleFlushObserver(this);
  }
}

nsRefreshDriver* nsIPresShell::GetRefreshDriver() const {
  return mPresContext ? mPresContext->RefreshDriver() : nullptr;
}

void nsIPresShell::SetAuthorStyleDisabled(bool aStyleDisabled) {
  if (aStyleDisabled != mStyleSet->GetAuthorStyleDisabled()) {
    mStyleSet->SetAuthorStyleDisabled(aStyleDisabled);
    ApplicableStylesChanged();

    nsCOMPtr<nsIObserverService> observerService =
        mozilla::services::GetObserverService();
    if (observerService) {
      observerService->NotifyObservers(
          ToSupports(mDocument), "author-style-disabled-changed", nullptr);
    }
  }
}

bool nsIPresShell::GetAuthorStyleDisabled() const {
  return mStyleSet->GetAuthorStyleDisabled();
}

void PresShell::UpdatePreferenceStyles() {
  if (!mDocument) {
    return;
  }

  // If the document doesn't have a window there's no need to notify
  // its presshell about changes to preferences since the document is
  // in a state where it doesn't matter any more (see
  // nsDocumentViewer::Close()).
  if (!mDocument->GetWindow()) {
    return;
  }

  // Documents in chrome shells do not have any preference style rules applied.
  if (nsContentUtils::IsInChromeDocshell(mDocument)) {
    return;
  }

  // We need to pass in mPresContext so that if the nsLayoutStylesheetCache
  // needs to recreate the pref style sheet, it has somewhere to get the
  // pref styling information from.  All pres contexts for
  // IsChromeOriginImage() == false will have the same pref styling information,
  // and similarly for IsChromeOriginImage() == true, so it doesn't really
  // matter which pres context we pass in when it does need to be recreated.
  // (See nsPresContext::GetDocumentColorPreferences for how whether we
  // are a chrome origin image affects some pref styling information.)
  auto cache = nsLayoutStylesheetCache::Singleton();
  RefPtr<StyleSheet> newPrefSheet =
      mPresContext->IsChromeOriginImage()
          ? cache->ChromePreferenceSheet(mPresContext)
          : cache->ContentPreferenceSheet(mPresContext);

  if (mPrefStyleSheet == newPrefSheet) {
    return;
  }

  RemovePreferenceStyles();

  // NOTE(emilio): This sheet is added as an agent sheet, because we don't want
  // it to be modifiable from devtools and similar, see bugs 1239336 and
  // 1436782. I think it conceptually should be a user sheet, and could be
  // without too much trouble I'd think.
  mStyleSet->AppendStyleSheet(SheetType::Agent, newPrefSheet);
  mPrefStyleSheet = newPrefSheet;
}

void PresShell::RemovePreferenceStyles() {
  if (mPrefStyleSheet) {
    mStyleSet->RemoveStyleSheet(SheetType::Agent, mPrefStyleSheet);
    mPrefStyleSheet = nullptr;
  }
}

void PresShell::AddUserSheet(StyleSheet* aSheet) {
  // Make sure this does what nsDocumentViewer::CreateStyleSet does wrt
  // ordering. We want this new sheet to come after all the existing stylesheet
  // service sheets (which are at the start), but before other user sheets; see
  // nsIStyleSheetService.idl for the ordering.

  nsStyleSheetService* sheetService = nsStyleSheetService::GetInstance();
  nsTArray<RefPtr<StyleSheet>>& userSheets = *sheetService->UserStyleSheets();

  // Search for the place to insert the new user sheet. Since all of the
  // stylesheet service provided user sheets should be at the start of the style
  // set's list, and aSheet should be at the end of userSheets. Given that, we
  // can find the right place to insert the new sheet based on the length of
  // userSheets.
  MOZ_ASSERT(aSheet);
  MOZ_ASSERT(userSheets.LastElement() == aSheet);

  size_t index = userSheets.Length() - 1;

  // Assert that all of userSheets (except for the last, new element) matches up
  // with what's in the style set.
  for (size_t i = 0; i < index; ++i) {
    MOZ_ASSERT(mStyleSet->StyleSheetAt(SheetType::User, i) == userSheets[i]);
  }

  if (index == static_cast<size_t>(mStyleSet->SheetCount(SheetType::User))) {
    mStyleSet->AppendStyleSheet(SheetType::User, aSheet);
  } else {
    StyleSheet* ref = mStyleSet->StyleSheetAt(SheetType::User, index);
    mStyleSet->InsertStyleSheetBefore(SheetType::User, aSheet, ref);
  }

  ApplicableStylesChanged();
}

void PresShell::AddAgentSheet(StyleSheet* aSheet) {
  // Make sure this does what nsDocumentViewer::CreateStyleSet does
  // wrt ordering.
  mStyleSet->AppendStyleSheet(SheetType::Agent, aSheet);
  ApplicableStylesChanged();
}

void PresShell::AddAuthorSheet(StyleSheet* aSheet) {
  // Document specific "additional" Author sheets should be stronger than the
  // ones added with the StyleSheetService.
  StyleSheet* firstAuthorSheet = mDocument->GetFirstAdditionalAuthorSheet();
  if (firstAuthorSheet) {
    mStyleSet->InsertStyleSheetBefore(SheetType::Doc, aSheet, firstAuthorSheet);
  } else {
    mStyleSet->AppendStyleSheet(SheetType::Doc, aSheet);
  }

  ApplicableStylesChanged();
}

void PresShell::RemoveSheet(SheetType aType, StyleSheet* aSheet) {
  mStyleSet->RemoveStyleSheet(aType, aSheet);
  ApplicableStylesChanged();
}

NS_IMETHODIMP
PresShell::SetDisplaySelection(int16_t aToggle) {
  RefPtr<nsFrameSelection> frameSelection = mSelection;
  frameSelection->SetDisplaySelection(aToggle);
  return NS_OK;
}

NS_IMETHODIMP
PresShell::GetDisplaySelection(int16_t* aToggle) {
  RefPtr<nsFrameSelection> frameSelection = mSelection;
  *aToggle = frameSelection->GetDisplaySelection();
  return NS_OK;
}

NS_IMETHODIMP
PresShell::GetSelectionFromScript(RawSelectionType aRawSelectionType,
                                  Selection** aSelection) {
  if (!aSelection || !mSelection) return NS_ERROR_NULL_POINTER;

  RefPtr<nsFrameSelection> frameSelection = mSelection;
  RefPtr<Selection> selection =
      frameSelection->GetSelection(ToSelectionType(aRawSelectionType));

  if (!selection) {
    return NS_ERROR_INVALID_ARG;
  }

  selection.forget(aSelection);
  return NS_OK;
}

Selection* PresShell::GetSelection(RawSelectionType aRawSelectionType) {
  if (!mSelection) {
    return nullptr;
  }

  RefPtr<nsFrameSelection> frameSelection = mSelection;
  return frameSelection->GetSelection(ToSelectionType(aRawSelectionType));
}

Selection* PresShell::GetCurrentSelection(SelectionType aSelectionType) {
  if (!mSelection) return nullptr;

  RefPtr<nsFrameSelection> frameSelection = mSelection;
  return frameSelection->GetSelection(aSelectionType);
}

already_AddRefed<nsISelectionController>
PresShell::GetSelectionControllerForFocusedContent(
    nsIContent** aFocusedContent) {
  if (aFocusedContent) {
    *aFocusedContent = nullptr;
  }

  if (mDocument) {
    nsCOMPtr<nsPIDOMWindowOuter> focusedWindow;
    nsCOMPtr<nsIContent> focusedContent = nsFocusManager::GetFocusedDescendant(
        mDocument->GetWindow(), nsFocusManager::eOnlyCurrentWindow,
        getter_AddRefs(focusedWindow));
    if (focusedContent) {
      nsIFrame* frame = focusedContent->GetPrimaryFrame();
      if (frame) {
        nsCOMPtr<nsISelectionController> selectionController;
        frame->GetSelectionController(mPresContext,
                                      getter_AddRefs(selectionController));
        if (selectionController) {
          if (aFocusedContent) {
            focusedContent.forget(aFocusedContent);
          }
          return selectionController.forget();
        }
      }
    }
  }
  nsCOMPtr<nsISelectionController> self(this);
  return self.forget();
}

NS_IMETHODIMP
PresShell::ScrollSelectionIntoView(RawSelectionType aRawSelectionType,
                                   SelectionRegion aRegion, int16_t aFlags) {
  if (!mSelection) return NS_ERROR_NULL_POINTER;

  RefPtr<nsFrameSelection> frameSelection = mSelection;
  return frameSelection->ScrollSelectionIntoView(
      ToSelectionType(aRawSelectionType), aRegion, aFlags);
}

NS_IMETHODIMP
PresShell::RepaintSelection(RawSelectionType aRawSelectionType) {
  if (!mSelection) {
    return NS_ERROR_NULL_POINTER;
  }

  if (MOZ_UNLIKELY(mIsDestroying)) {
    return NS_OK;
  }

  RefPtr<nsFrameSelection> frameSelection = mSelection;
  return frameSelection->RepaintSelection(ToSelectionType(aRawSelectionType));
}

// Make shell be a document observer
void nsIPresShell::BeginObservingDocument() {
  if (mDocument && !mIsDestroying) {
    mIsObservingDocument = true;
    if (mIsDocumentGone) {
      NS_WARNING(
          "Adding a presshell that was disconnected from the document "
          "as a document observer?  Sounds wrong...");
      mIsDocumentGone = false;
    }
  }
}

// Make shell stop being a document observer
void nsIPresShell::EndObservingDocument() {
  // XXXbz do we need to tell the frame constructor that the document
  // is gone, perhaps?  Except for printing it's NOT gone, sometimes.
  mIsDocumentGone = true;
  mIsObservingDocument = false;
}

#ifdef DEBUG_kipp
char* nsPresShell_ReflowStackPointerTop;
#endif

class XBLConstructorRunner : public Runnable {
 public:
  explicit XBLConstructorRunner(Document* aDocument)
      : Runnable("XBLConstructorRunner"), mDocument(aDocument) {}

  NS_IMETHOD Run() override {
    mDocument->BindingManager()->ProcessAttachedQueue();
    return NS_OK;
  }

 private:
  RefPtr<Document> mDocument;
};

nsresult PresShell::Initialize() {
  if (mIsDestroying) {
    return NS_OK;
  }

  if (!mDocument) {
    // Nothing to do
    return NS_OK;
  }

  MOZ_LOG(gLog, LogLevel::Debug, ("PresShell::Initialize this=%p", this));

  NS_ASSERTION(!mDidInitialize, "Why are we being called?");

  nsCOMPtr<nsIPresShell> kungFuDeathGrip(this);

  RecomputeFontSizeInflationEnabled();
  MOZ_DIAGNOSTIC_ASSERT(!mIsDestroying);

  // Ensure the pres context doesn't think it has changed, since we haven't even
  // started layout. This avoids spurious restyles / reflows afterwards.
  //
  // Note that this is very intentionally before setting mDidInitialize so it
  // doesn't notify the document, or run media query change events.
  mPresContext->FlushPendingMediaFeatureValuesChanged();
  MOZ_DIAGNOSTIC_ASSERT(!mIsDestroying);

  mDidInitialize = true;

#ifdef DEBUG
  if (VERIFY_REFLOW_NOISY_RC & gVerifyReflowFlags) {
    if (mDocument) {
      nsIURI* uri = mDocument->GetDocumentURI();
      if (uri) {
        printf("*** PresShell::Initialize (this=%p, url='%s')\n", (void*)this,
               uri->GetSpecOrDefault().get());
      }
    }
  }
#endif

  // Get the root frame from the frame manager
  // XXXbz it would be nice to move this somewhere else... like frame manager
  // Init(), say.  But we need to make sure our views are all set up by the
  // time we do this!
  nsIFrame* rootFrame = mFrameConstructor->GetRootFrame();
  NS_ASSERTION(!rootFrame, "How did that happen, exactly?");

  if (!rootFrame) {
    nsAutoScriptBlocker scriptBlocker;
    rootFrame = mFrameConstructor->ConstructRootFrame();
    mFrameConstructor->SetRootFrame(rootFrame);
  }

  NS_ENSURE_STATE(!mHaveShutDown);

  if (!rootFrame) {
    return NS_ERROR_OUT_OF_MEMORY;
  }

  if (Element* root = mDocument->GetRootElement()) {
    {
      nsAutoCauseReflowNotifier reflowNotifier(this);
      // Have the style sheet processor construct frame for the root
      // content object down
      mFrameConstructor->ContentInserted(
          root, nullptr, nsCSSFrameConstructor::InsertionKind::Sync);

      // Something in mFrameConstructor->ContentInserted may have caused
      // Destroy() to get called, bug 337586.
      NS_ENSURE_STATE(!mHaveShutDown);
    }

    // nsAutoCauseReflowNotifier (which sets up a script blocker) going out of
    // scope may have killed us too
    NS_ENSURE_STATE(!mHaveShutDown);

    // Run the XBL binding constructors for any new frames we've constructed.
    // (Do this in a script runner, since our caller might have a script
    // blocker on the stack.)
    nsContentUtils::AddScriptRunner(new XBLConstructorRunner(mDocument));

    // XBLConstructorRunner might destroy us.
    NS_ENSURE_STATE(!mHaveShutDown);
  }

  mDocument->TriggerAutoFocus();

  NS_ASSERTION(rootFrame, "How did that happen?");

  // Note: when the frame was created above it had the NS_FRAME_IS_DIRTY bit
  // set, but XBL processing could have caused a reflow which clears it.
  if (MOZ_LIKELY(rootFrame->GetStateBits() & NS_FRAME_IS_DIRTY)) {
    // Unset the DIRTY bits so that FrameNeedsReflow() will work right.
    rootFrame->RemoveStateBits(NS_FRAME_IS_DIRTY | NS_FRAME_HAS_DIRTY_CHILDREN);
    NS_ASSERTION(!mDirtyRoots.Contains(rootFrame),
                 "Why is the root in mDirtyRoots already?");
    FrameNeedsReflow(rootFrame, nsIPresShell::eResize, NS_FRAME_IS_DIRTY);
    NS_ASSERTION(mDirtyRoots.Contains(rootFrame),
                 "Should be in mDirtyRoots now");
    NS_ASSERTION(mObservingLayoutFlushes, "Why no reflow scheduled?");
  }

  // Restore our root scroll position now if we're getting here after EndLoad
  // got called, since this is our one chance to do it.  Note that we need not
  // have reflowed for this to work; when the scrollframe is finally reflowed
  // it'll pick up the position we store in it here.
  if (!mDocumentLoading) {
    RestoreRootScrollPosition();
  }

  // For printing, we just immediately unsuppress.
  if (!mPresContext->IsPaginated()) {
    // Kick off a one-shot timer based off our pref value.  When this timer
    // fires, if painting is still locked down, then we will go ahead and
    // trigger a full invalidate and allow painting to proceed normally.
    mPaintingSuppressed = true;
    // Don't suppress painting if the document isn't loading.
    Document::ReadyState readyState = mDocument->GetReadyStateEnum();
    if (readyState != Document::READYSTATE_COMPLETE) {
      mPaintSuppressionTimer = NS_NewTimer();
    }
    if (!mPaintSuppressionTimer) {
      mPaintingSuppressed = false;
    } else {
      // Initialize the timer.

      // Default to PAINTLOCK_EVENT_DELAY if we can't get the pref value.
      int32_t delay = Preferences::GetInt("nglayout.initialpaint.delay",
                                          PAINTLOCK_EVENT_DELAY);

      mPaintSuppressionTimer->SetTarget(
          mDocument->EventTargetFor(TaskCategory::Other));
      mPaintSuppressionTimer->InitWithNamedFuncCallback(
          sPaintSuppressionCallback, this, delay, nsITimer::TYPE_ONE_SHOT,
          "PresShell::sPaintSuppressionCallback");
    }
  }

  // If we get here and painting is not suppressed, then we can paint anytime
  // and we should fire the before-first-paint notification
  if (!mPaintingSuppressed) {
    ScheduleBeforeFirstPaint();
  }

  return NS_OK;  // XXX this needs to be real. MMP
}

void PresShell::sPaintSuppressionCallback(nsITimer* aTimer, void* aPresShell) {
  RefPtr<PresShell> self = static_cast<PresShell*>(aPresShell);
  if (self) self->UnsuppressPainting();
}

nsresult PresShell::ResizeReflow(nscoord aWidth, nscoord aHeight,
                                 nscoord aOldWidth, nscoord aOldHeight,
                                 ResizeReflowOptions aOptions) {
  if (mZoomConstraintsClient) {
    // If we have a ZoomConstraintsClient and the available screen area
    // changed, then we might need to disable double-tap-to-zoom, so notify
    // the ZCC to update itself.
    mZoomConstraintsClient->ScreenSizeChanged();
  }
  if (mMobileViewportManager) {
    // If we have a mobile viewport manager, request a reflow from it. It can
    // recompute the final CSS viewport and trigger a call to
    // ResizeReflowIgnoreOverride if it changed.
    mMobileViewportManager->RequestReflow();
    return NS_OK;
  }

  return ResizeReflowIgnoreOverride(aWidth, aHeight, aOldWidth, aOldHeight,
                                    aOptions);
}

nsresult PresShell::ResizeReflowIgnoreOverride(nscoord aWidth, nscoord aHeight,
                                               nscoord aOldWidth,
                                               nscoord aOldHeight,
                                               ResizeReflowOptions aOptions) {
  MOZ_ASSERT(!mIsReflowing, "Shouldn't be in reflow here!");

  nsIFrame* rootFrame = mFrameConstructor->GetRootFrame();
  if (!rootFrame) {
    // If we don't have a root frame yet, that means we haven't had our initial
    // reflow... If that's the case, and aWidth or aHeight is unconstrained,
    // ignore them altogether.
    if (aHeight == NS_UNCONSTRAINEDSIZE || aWidth == NS_UNCONSTRAINEDSIZE) {
      // We can't do the work needed for SizeToContent without a root
      // frame, and we want to return before setting the visible area.
      return NS_ERROR_NOT_AVAILABLE;
    }

    mPresContext->SetVisibleArea(nsRect(0, 0, aWidth, aHeight));
    // There isn't anything useful we can do if the initial reflow hasn't
    // happened.
    return NS_OK;
  }

  WritingMode wm = rootFrame->GetWritingMode();
  const bool shrinkToFit = aOptions == ResizeReflowOptions::eBSizeLimit;
  MOZ_ASSERT(shrinkToFit ||
                 (wm.IsVertical() ? aWidth : aHeight) != NS_UNCONSTRAINEDSIZE,
             "unconstrained bsize only usable with eBSizeLimit");
  MOZ_ASSERT((wm.IsVertical() ? aHeight : aWidth) != NS_UNCONSTRAINEDSIZE,
             "unconstrained isize not allowed");
  bool isBSizeChanging =
      wm.IsVertical() ? aOldWidth != aWidth : aOldHeight != aHeight;
  nscoord targetWidth = aWidth;
  nscoord targetHeight = aHeight;

  if (shrinkToFit) {
    if (wm.IsVertical()) {
      targetWidth = NS_UNCONSTRAINEDSIZE;
    } else {
      targetHeight = NS_UNCONSTRAINEDSIZE;
    }
    isBSizeChanging = true;
  }

  const bool suppressingResizeReflow =
      GetPresContext()->SuppressingResizeReflow();

  RefPtr<nsViewManager> viewManager = mViewManager;
  nsCOMPtr<nsIPresShell> kungFuDeathGrip(this);

  if (!suppressingResizeReflow && shrinkToFit) {
    // Make sure that style is flushed before setting the pres context
    // VisibleArea if we're shrinking to fit.
    //
    // Otherwise we may end up with bogus viewport units resolved against the
    // unconstrained bsize, or restyling the whole document resolving viewport
    // units against targetWidth, which may end up doing wasteful work.
    mDocument->FlushPendingNotifications(FlushType::Frames);
  }

  if (!mIsDestroying) {
    mPresContext->SetVisibleArea(nsRect(0, 0, targetWidth, targetHeight));
  }

  if (!mIsDestroying && !suppressingResizeReflow) {
    if (!shrinkToFit) {
      // Flush styles _now_ (with the correct visible area) if not computing the
      // shrink-to-fit size.
      //
      // We've asserted above that sizes are not unconstrained, so this is going
      // to be the final size, which means that we'll get the (correct) final
      // styles now, and avoid a further potentially-wasteful full recascade on
      // the next flush.
      mDocument->FlushPendingNotifications(FlushType::Frames);
    }

    rootFrame = mFrameConstructor->GetRootFrame();
    if (!mIsDestroying && rootFrame) {
      // XXX Do a full invalidate at the beginning so that invalidates along
      // the way don't have region accumulation issues?

      if (isBSizeChanging) {
        // For BSize changes driven by style, RestyleManager handles this.
        // For height:auto BSizes (i.e. layout-controlled), descendant
        // intrinsic sizes can't depend on them. So the only other case is
        // viewport-controlled BSizes which we handle here.
        nsLayoutUtils::MarkIntrinsicISizesDirtyIfDependentOnBSize(rootFrame);
      }

      {
        nsAutoCauseReflowNotifier crNotifier(this);
        WillDoReflow();

        // Kick off a top-down reflow
        AUTO_LAYOUT_PHASE_ENTRY_POINT(GetPresContext(), Reflow);
        nsViewManager::AutoDisableRefresh refreshBlocker(viewManager);

        mDirtyRoots.Remove(rootFrame);
        DoReflow(rootFrame, true, nullptr);

        if (shrinkToFit) {
          const bool reflowAgain =
              wm.IsVertical() ? mPresContext->GetVisibleArea().width > aWidth
                              : mPresContext->GetVisibleArea().height > aHeight;

          if (reflowAgain) {
            mPresContext->SetVisibleArea(nsRect(0, 0, aWidth, aHeight));
            DoReflow(rootFrame, true, nullptr);
          }
        }
      }

      // the first DoReflow above should've set our bsize if it was
      // NS_UNCONSTRAINEDSIZE, and the isize shouldn't be NS_UNCONSTRAINEDSIZE
      // anyway
      NS_ASSERTION(mPresContext->GetVisibleArea().width != NS_UNCONSTRAINEDSIZE,
                   "width should not be NS_UNCONSTRAINEDSIZE after reflow");
      NS_ASSERTION(
          mPresContext->GetVisibleArea().height != NS_UNCONSTRAINEDSIZE,
          "height should not be NS_UNCONSTRAINEDSIZE after reflow");

      DidDoReflow(true);
    }
  }

  rootFrame = mFrameConstructor->GetRootFrame();
  if (rootFrame) {
    wm = rootFrame->GetWritingMode();
    // reflow did not happen; if the reflow happened, our bsize should not be
    // NS_UNCONSTRAINEDSIZE because DoReflow will fix it up to the same values
    // as below
    if (wm.IsVertical()) {
      if (mPresContext->GetVisibleArea().width == NS_UNCONSTRAINEDSIZE) {
        mPresContext->SetVisibleArea(
            nsRect(0, 0, rootFrame->GetRect().width, aHeight));
      }
    } else {
      if (mPresContext->GetVisibleArea().height == NS_UNCONSTRAINEDSIZE) {
        mPresContext->SetVisibleArea(
            nsRect(0, 0, aWidth, rootFrame->GetRect().height));
      }
    }
  }

  if (!mIsDestroying && !mResizeEventPending) {
    mResizeEventPending = true;
    if (MOZ_LIKELY(!mDocument->GetBFCacheEntry())) {
      mPresContext->RefreshDriver()->AddResizeEventFlushObserver(this);
    }
  }

  return NS_OK;  // XXX this needs to be real. MMP
}

void PresShell::FireResizeEvent() {
  if (mIsDocumentGone) {
    return;
  }

  // If event handling is suppressed, repost the resize event to the refresh
  // driver. The event is marked as delayed so that the refresh driver does not
  // continue ticking.
  if (mDocument->EventHandlingSuppressed()) {
    if (MOZ_LIKELY(!mDocument->GetBFCacheEntry())) {
      mDocument->SetHasDelayedRefreshEvent();
      mPresContext->RefreshDriver()->AddResizeEventFlushObserver(
          this, /* aDelayed = */ true);
    }
    return;
  }

  mResizeEventPending = false;

  // Send resize event from here.
  WidgetEvent event(true, mozilla::eResize);
  nsEventStatus status = nsEventStatus_eIgnore;

  if (nsPIDOMWindowOuter* window = mDocument->GetWindow()) {
    EventDispatcher::Dispatch(window, mPresContext, &event, nullptr, &status);
  }
}

static nsIContent* GetNativeAnonymousSubtreeRoot(nsIContent* aContent) {
  if (!aContent || !aContent->IsInNativeAnonymousSubtree()) {
    return nullptr;
  }
  auto* current = aContent;
  // FIXME(emilio): This should not need to worry about current being null, but
  // editor removes nodes in native anonymous subtrees, and we don't clean nodes
  // from the current event content stack from ContentRemoved, so it can
  // actually happen, see bug 1510208.
  while (current && !current->IsRootOfNativeAnonymousSubtree()) {
    current = current->GetFlattenedTreeParent();
  }
  return current;
}

void nsIPresShell::NativeAnonymousContentRemoved(nsIContent* aAnonContent) {
  MOZ_ASSERT(aAnonContent->IsRootOfNativeAnonymousSubtree());
  if (nsIContent* root = GetNativeAnonymousSubtreeRoot(mCurrentEventContent)) {
    if (aAnonContent == root) {
      mCurrentEventContent = aAnonContent->GetFlattenedTreeParent();
      mCurrentEventFrame = nullptr;
    }
  }

  for (unsigned int i = 0; i < mCurrentEventContentStack.Length(); i++) {
    nsIContent* anon =
        GetNativeAnonymousSubtreeRoot(mCurrentEventContentStack.ElementAt(i));
    if (aAnonContent == anon) {
      mCurrentEventContentStack.ReplaceObjectAt(
          aAnonContent->GetFlattenedTreeParent(), i);
      mCurrentEventFrameStack[i] = nullptr;
    }
  }
}

void PresShell::SetIgnoreFrameDestruction(bool aIgnore) {
  if (mDocument) {
    // We need to tell the ImageLoader to drop all its references to frames
    // because they're about to go away and it won't get notifications of that.
    mDocument->StyleImageLoader()->ClearFrames(mPresContext);
  }
  mIgnoreFrameDestruction = aIgnore;
}

void PresShell::NotifyDestroyingFrame(nsIFrame* aFrame) {
  // We must remove these from FrameLayerBuilder::DisplayItemData::mFrameList
  // here, otherwise the DisplayItemData destructor will use the destroyed frame
  // when it tries to remove it from the (array) value of this property.
  aFrame->RemoveDisplayItemDataForDeletion();

  if (!mIgnoreFrameDestruction) {
    if (aFrame->HasImageRequest()) {
      mDocument->StyleImageLoader()->DropRequestsForFrame(aFrame);
    }

    mFrameConstructor->NotifyDestroyingFrame(aFrame);

    mDirtyRoots.Remove(aFrame);

    // Remove frame properties
    aFrame->DeleteAllProperties();

    if (aFrame == mCurrentEventFrame) {
      mCurrentEventContent = aFrame->GetContent();
      mCurrentEventFrame = nullptr;
    }

#ifdef DEBUG
    if (aFrame == mDrawEventTargetFrame) {
      mDrawEventTargetFrame = nullptr;
    }
#endif

    for (unsigned int i = 0; i < mCurrentEventFrameStack.Length(); i++) {
      if (aFrame == mCurrentEventFrameStack.ElementAt(i)) {
        // One of our stack frames was deleted.  Get its content so that when we
        // pop it we can still get its new frame from its content
        nsIContent* currentEventContent = aFrame->GetContent();
        mCurrentEventContentStack.ReplaceObjectAt(currentEventContent, i);
        mCurrentEventFrameStack[i] = nullptr;
      }
    }

    mFramesToDirty.RemoveEntry(aFrame);

    nsIScrollableFrame* scrollableFrame = do_QueryFrame(aFrame);
    if (scrollableFrame) {
      mDirtyScrollAnchorContainers.RemoveEntry(scrollableFrame);
    }
  }
}

already_AddRefed<nsCaret> PresShell::GetCaret() const {
  RefPtr<nsCaret> caret = mCaret;
  return caret.forget();
}

already_AddRefed<AccessibleCaretEventHub>
PresShell::GetAccessibleCaretEventHub() const {
  RefPtr<AccessibleCaretEventHub> eventHub = mAccessibleCaretEventHub;
  return eventHub.forget();
}

void PresShell::SetCaret(nsCaret* aNewCaret) { mCaret = aNewCaret; }

void PresShell::RestoreCaret() { mCaret = mOriginalCaret; }

NS_IMETHODIMP PresShell::SetCaretEnabled(bool aInEnable) {
  bool oldEnabled = mCaretEnabled;

  mCaretEnabled = aInEnable;

  if (mCaretEnabled != oldEnabled) {
    MOZ_ASSERT(mCaret);
    if (mCaret) {
      mCaret->SetVisible(mCaretEnabled);
    }
  }

  return NS_OK;
}

NS_IMETHODIMP PresShell::SetCaretReadOnly(bool aReadOnly) {
  if (mCaret) mCaret->SetCaretReadOnly(aReadOnly);
  return NS_OK;
}

NS_IMETHODIMP PresShell::GetCaretEnabled(bool* aOutEnabled) {
  NS_ENSURE_ARG_POINTER(aOutEnabled);
  *aOutEnabled = mCaretEnabled;
  return NS_OK;
}

NS_IMETHODIMP PresShell::SetCaretVisibilityDuringSelection(bool aVisibility) {
  if (mCaret) mCaret->SetVisibilityDuringSelection(aVisibility);
  return NS_OK;
}

NS_IMETHODIMP PresShell::GetCaretVisible(bool* aOutIsVisible) {
  *aOutIsVisible = false;
  if (mCaret) {
    *aOutIsVisible = mCaret->IsVisible();
  }
  return NS_OK;
}

NS_IMETHODIMP PresShell::SetSelectionFlags(int16_t aInEnable) {
  mSelectionFlags = aInEnable;
  return NS_OK;
}

NS_IMETHODIMP PresShell::GetSelectionFlags(int16_t* aOutEnable) {
  if (!aOutEnable) return NS_ERROR_INVALID_ARG;
  *aOutEnable = mSelectionFlags;
  return NS_OK;
}

// implementation of nsISelectionController

NS_IMETHODIMP
PresShell::PhysicalMove(int16_t aDirection, int16_t aAmount, bool aExtend) {
  RefPtr<nsFrameSelection> frameSelection = mSelection;
  return frameSelection->PhysicalMove(aDirection, aAmount, aExtend);
}

NS_IMETHODIMP
PresShell::CharacterMove(bool aForward, bool aExtend) {
  RefPtr<nsFrameSelection> frameSelection = mSelection;
  return frameSelection->CharacterMove(aForward, aExtend);
}

NS_IMETHODIMP
PresShell::CharacterExtendForDelete() {
  RefPtr<nsFrameSelection> frameSelection = mSelection;
  return frameSelection->CharacterExtendForDelete();
}

NS_IMETHODIMP
PresShell::CharacterExtendForBackspace() {
  RefPtr<nsFrameSelection> frameSelection = mSelection;
  return frameSelection->CharacterExtendForBackspace();
}

NS_IMETHODIMP
PresShell::WordMove(bool aForward, bool aExtend) {
  RefPtr<nsFrameSelection> frameSelection = mSelection;
  nsresult result = frameSelection->WordMove(aForward, aExtend);
  // if we can't go down/up any more we must then move caret completely to
  // end/beginning respectively.
  if (NS_FAILED(result)) result = CompleteMove(aForward, aExtend);
  return result;
}

NS_IMETHODIMP
PresShell::WordExtendForDelete(bool aForward) {
  RefPtr<nsFrameSelection> frameSelection = mSelection;
  return frameSelection->WordExtendForDelete(aForward);
}

NS_IMETHODIMP
PresShell::LineMove(bool aForward, bool aExtend) {
  RefPtr<nsFrameSelection> frameSelection = mSelection;
  nsresult result = frameSelection->LineMove(aForward, aExtend);
  // if we can't go down/up any more we must then move caret completely to
  // end/beginning respectively.
  if (NS_FAILED(result)) result = CompleteMove(aForward, aExtend);
  return result;
}

NS_IMETHODIMP
PresShell::IntraLineMove(bool aForward, bool aExtend) {
  RefPtr<nsFrameSelection> frameSelection = mSelection;
  return frameSelection->IntraLineMove(aForward, aExtend);
}

NS_IMETHODIMP
PresShell::PageMove(bool aForward, bool aExtend) {
  nsIFrame* frame = nullptr;
  if (!aExtend) {
    frame = do_QueryFrame(GetScrollableFrameToScroll(nsIPresShell::eVertical));
    // If there is no scrollable frame, get the frame to move caret instead.
  }
  if (!frame) {
    frame = mSelection->GetFrameToPageSelect();
    if (!frame) {
      return NS_OK;
    }
  }
  RefPtr<nsFrameSelection> frameSelection = mSelection;
  frameSelection->CommonPageMove(aForward, aExtend, frame);
  // After ScrollSelectionIntoView(), the pending notifications might be
  // flushed and PresShell/PresContext/Frames may be dead. See bug 418470.
  return ScrollSelectionIntoView(
      nsISelectionController::SELECTION_NORMAL,
      nsISelectionController::SELECTION_FOCUS_REGION,
      nsISelectionController::SCROLL_SYNCHRONOUS |
          nsISelectionController::SCROLL_FOR_CARET_MOVE);
}

NS_IMETHODIMP
PresShell::ScrollPage(bool aForward) {
  nsIScrollableFrame* scrollFrame =
      GetScrollableFrameToScroll(nsIPresShell::eVertical);
  if (scrollFrame) {
    scrollFrame->ScrollBy(nsIntPoint(0, aForward ? 1 : -1),
                          nsIScrollableFrame::PAGES, nsIScrollableFrame::SMOOTH,
                          nullptr, nullptr, nsIScrollableFrame::NOT_MOMENTUM,
                          nsIScrollableFrame::ENABLE_SNAP);
  }
  return NS_OK;
}

NS_IMETHODIMP
PresShell::ScrollLine(bool aForward) {
  nsIScrollableFrame* scrollFrame =
      GetScrollableFrameToScroll(nsIPresShell::eVertical);
  if (scrollFrame) {
    int32_t lineCount =
        Preferences::GetInt("toolkit.scrollbox.verticalScrollDistance",
                            NS_DEFAULT_VERTICAL_SCROLL_DISTANCE);
    scrollFrame->ScrollBy(nsIntPoint(0, aForward ? lineCount : -lineCount),
                          nsIScrollableFrame::LINES, nsIScrollableFrame::SMOOTH,
                          nullptr, nullptr, nsIScrollableFrame::NOT_MOMENTUM,
                          nsIScrollableFrame::ENABLE_SNAP);
  }
  return NS_OK;
}

NS_IMETHODIMP
PresShell::ScrollCharacter(bool aRight) {
  nsIScrollableFrame* scrollFrame =
      GetScrollableFrameToScroll(nsIPresShell::eHorizontal);
  if (scrollFrame) {
    int32_t h =
        Preferences::GetInt("toolkit.scrollbox.horizontalScrollDistance",
                            NS_DEFAULT_HORIZONTAL_SCROLL_DISTANCE);
    scrollFrame->ScrollBy(nsIntPoint(aRight ? h : -h, 0),
                          nsIScrollableFrame::LINES, nsIScrollableFrame::SMOOTH,
                          nullptr, nullptr, nsIScrollableFrame::NOT_MOMENTUM,
                          nsIScrollableFrame::ENABLE_SNAP);
  }
  return NS_OK;
}

NS_IMETHODIMP
PresShell::CompleteScroll(bool aForward) {
  nsIScrollableFrame* scrollFrame =
      GetScrollableFrameToScroll(nsIPresShell::eVertical);
  if (scrollFrame) {
    scrollFrame->ScrollBy(nsIntPoint(0, aForward ? 1 : -1),
                          nsIScrollableFrame::WHOLE, nsIScrollableFrame::SMOOTH,
                          nullptr, nullptr, nsIScrollableFrame::NOT_MOMENTUM,
                          nsIScrollableFrame::ENABLE_SNAP);
  }
  return NS_OK;
}

NS_IMETHODIMP
PresShell::CompleteMove(bool aForward, bool aExtend) {
  // Beware! This may flush notifications via synchronous
  // ScrollSelectionIntoView.
  RefPtr<nsFrameSelection> frameSelection = mSelection;
  nsIContent* limiter = frameSelection->GetAncestorLimiter();
  nsIFrame* frame = limiter ? limiter->GetPrimaryFrame()
                            : FrameConstructor()->GetRootElementFrame();
  if (!frame) return NS_ERROR_FAILURE;
  nsIFrame::CaretPosition pos = frame->GetExtremeCaretPosition(!aForward);
  frameSelection->HandleClick(
      pos.mResultContent, pos.mContentOffset, pos.mContentOffset, aExtend,
      false, aForward ? CARET_ASSOCIATE_AFTER : CARET_ASSOCIATE_BEFORE);
  if (limiter) {
    // HandleClick resets ancestorLimiter, so set it again.
    frameSelection->SetAncestorLimiter(limiter);
  }

  // After ScrollSelectionIntoView(), the pending notifications might be
  // flushed and PresShell/PresContext/Frames may be dead. See bug 418470.
  return ScrollSelectionIntoView(
      nsISelectionController::SELECTION_NORMAL,
      nsISelectionController::SELECTION_FOCUS_REGION,
      nsISelectionController::SCROLL_SYNCHRONOUS |
          nsISelectionController::SCROLL_FOR_CARET_MOVE);
}

NS_IMETHODIMP
PresShell::SelectAll() {
  RefPtr<nsFrameSelection> frameSelection = mSelection;
  return frameSelection->SelectAll();
}

static void DoCheckVisibility(nsPresContext* aPresContext, nsIContent* aNode,
                              int16_t aStartOffset, int16_t aEndOffset,
                              bool* aRetval) {
  nsIFrame* frame = aNode->GetPrimaryFrame();
  if (!frame) {
    // No frame to look at so it must not be visible.
    return;
  }

  // Start process now to go through all frames to find startOffset. Then check
  // chars after that to see if anything until EndOffset is visible.
  bool finished = false;
  frame->CheckVisibility(aPresContext, aStartOffset, aEndOffset, true,
                         &finished, aRetval);
  // Don't worry about other return value.
}

NS_IMETHODIMP
PresShell::CheckVisibility(nsINode* node, int16_t startOffset,
                           int16_t EndOffset, bool* _retval) {
  if (!node || startOffset > EndOffset || !_retval || startOffset < 0 ||
      EndOffset < 0)
    return NS_ERROR_INVALID_ARG;
  *_retval = false;  // initialize return parameter
  nsCOMPtr<nsIContent> content(do_QueryInterface(node));
  if (!content) return NS_ERROR_FAILURE;

  DoCheckVisibility(mPresContext, content, startOffset, EndOffset, _retval);
  return NS_OK;
}

nsresult PresShell::CheckVisibilityContent(nsIContent* aNode,
                                           int16_t aStartOffset,
                                           int16_t aEndOffset, bool* aRetval) {
  if (!aNode || aStartOffset > aEndOffset || !aRetval || aStartOffset < 0 ||
      aEndOffset < 0) {
    return NS_ERROR_INVALID_ARG;
  }

  *aRetval = false;
  DoCheckVisibility(mPresContext, aNode, aStartOffset, aEndOffset, aRetval);
  return NS_OK;
}

// end implementations nsISelectionController

nsIFrame* nsIPresShell::GetRootScrollFrame() const {
  nsIFrame* rootFrame = mFrameConstructor->GetRootFrame();
  // Ensure root frame is a viewport frame
  if (!rootFrame || !rootFrame->IsViewportFrame()) return nullptr;
  nsIFrame* theFrame = rootFrame->PrincipalChildList().FirstChild();
  if (!theFrame || !theFrame->IsScrollFrame()) return nullptr;
  return theFrame;
}

nsIScrollableFrame* nsIPresShell::GetRootScrollFrameAsScrollable() const {
  nsIFrame* frame = GetRootScrollFrame();
  if (!frame) return nullptr;
  nsIScrollableFrame* scrollableFrame = do_QueryFrame(frame);
  NS_ASSERTION(scrollableFrame,
               "All scroll frames must implement nsIScrollableFrame");
  return scrollableFrame;
}

nsIPageSequenceFrame* PresShell::GetPageSequenceFrame() const {
  nsIFrame* frame = mFrameConstructor->GetPageSequenceFrame();
  return do_QueryFrame(frame);
}

nsCanvasFrame* PresShell::GetCanvasFrame() const {
  nsIFrame* frame = mFrameConstructor->GetDocElementContainingBlock();
  return do_QueryFrame(frame);
}

void PresShell::RestoreRootScrollPosition() {
  nsIScrollableFrame* scrollableFrame = GetRootScrollFrameAsScrollable();
  if (scrollableFrame) {
    scrollableFrame->ScrollToRestoredPosition();
  }
}

void PresShell::MaybeReleaseCapturingContent() {
  RefPtr<nsFrameSelection> frameSelection = FrameSelection();
  if (frameSelection) {
    frameSelection->SetDragState(false);
  }
  if (gCaptureInfo.mContent && gCaptureInfo.mContent->OwnerDoc() == mDocument) {
    SetCapturingContent(nullptr, 0);
  }
}

void PresShell::BeginLoad(Document* aDocument) {
  mDocumentLoading = true;

  gfxTextPerfMetrics* tp = nullptr;
  if (mPresContext) {
    tp = mPresContext->GetTextPerfMetrics();
  }

  bool shouldLog = MOZ_LOG_TEST(gLog, LogLevel::Debug);
  if (shouldLog || tp) {
    mLoadBegin = TimeStamp::Now();
  }

  if (shouldLog) {
    nsIURI* uri = mDocument->GetDocumentURI();
    MOZ_LOG(gLog, LogLevel::Debug,
            ("(presshell) %p load begin [%s]\n", this,
             uri ? uri->GetSpecOrDefault().get() : ""));
  }
}

void PresShell::EndLoad(Document* aDocument) {
  MOZ_ASSERT(aDocument == mDocument, "Wrong document");

  RestoreRootScrollPosition();

  mDocumentLoading = false;
}

void PresShell::LoadComplete() {
  gfxTextPerfMetrics* tp = nullptr;
  if (mPresContext) {
    tp = mPresContext->GetTextPerfMetrics();
  }

  // log load
  bool shouldLog = MOZ_LOG_TEST(gLog, LogLevel::Debug);
  if (shouldLog || tp) {
    TimeDuration loadTime = TimeStamp::Now() - mLoadBegin;
    nsIURI* uri = mDocument->GetDocumentURI();
    nsAutoCString spec;
    if (uri) {
      spec = uri->GetSpecOrDefault();
    }
    if (shouldLog) {
      MOZ_LOG(gLog, LogLevel::Debug,
              ("(presshell) %p load done time-ms: %9.2f [%s]\n", this,
               loadTime.ToMilliseconds(), spec.get()));
    }
    if (tp) {
      tp->Accumulate();
      if (tp->cumulative.numChars > 0) {
        LogTextPerfStats(tp, this, tp->cumulative, loadTime.ToMilliseconds(),
                         eLog_loaddone, spec.get());
      }
    }
  }
}

#ifdef DEBUG
void PresShell::VerifyHasDirtyRootAncestor(nsIFrame* aFrame) {
  // XXXbz due to bug 372769, can't actually assert anything here...
  return;

  // XXXbz shouldn't need this part; remove it once FrameNeedsReflow
  // handles the root frame correctly.
  if (!aFrame->GetParent()) {
    return;
  }

  // Make sure that there is a reflow root ancestor of |aFrame| that's
  // in mDirtyRoots already.
  while (aFrame && (aFrame->GetStateBits() & NS_FRAME_HAS_DIRTY_CHILDREN)) {
    if ((aFrame->HasAnyStateBits(NS_FRAME_REFLOW_ROOT |
                                 NS_FRAME_DYNAMIC_REFLOW_ROOT) ||
         !aFrame->GetParent()) &&
        mDirtyRoots.Contains(aFrame)) {
      return;
    }

    aFrame = aFrame->GetParent();
  }

  MOZ_ASSERT_UNREACHABLE(
      "Frame has dirty bits set but isn't scheduled to be "
      "reflowed?");
}
#endif

void PresShell::PostDirtyScrollAnchorContainer(nsIScrollableFrame* aFrame) {
  mDirtyScrollAnchorContainers.PutEntry(aFrame);
}

void PresShell::FlushDirtyScrollAnchorContainers() {
  for (auto iter = mDirtyScrollAnchorContainers.Iter(); !iter.Done();
       iter.Next()) {
    nsIScrollableFrame* scroll = iter.Get()->GetKey();
    scroll->GetAnchor()->SelectAnchor();
  }
  mDirtyScrollAnchorContainers.Clear();
}

void PresShell::FrameNeedsReflow(nsIFrame* aFrame,
                                 IntrinsicDirty aIntrinsicDirty,
                                 nsFrameState aBitToAdd,
                                 ReflowRootHandling aRootHandling) {
  MOZ_ASSERT(aBitToAdd == NS_FRAME_IS_DIRTY ||
                 aBitToAdd == NS_FRAME_HAS_DIRTY_CHILDREN || !aBitToAdd,
             "Unexpected bits being added");

  // FIXME bug 478135
  NS_ASSERTION(!(aIntrinsicDirty == eStyleChange &&
                 aBitToAdd == NS_FRAME_HAS_DIRTY_CHILDREN),
               "bits don't correspond to style change reason");

  // FIXME bug 457400
  NS_ASSERTION(!mIsReflowing, "can't mark frame dirty during reflow");

  // If we've not yet done the initial reflow, then don't bother
  // enqueuing a reflow command yet.
  if (!mDidInitialize) return;

  // If we're already destroying, don't bother with this either.
  if (mIsDestroying) return;

#ifdef DEBUG
  // printf("gShellCounter: %d\n", gShellCounter++);
  if (mInVerifyReflow) return;

  if (VERIFY_REFLOW_NOISY_RC & gVerifyReflowFlags) {
    printf("\nPresShell@%p: frame %p needs reflow\n", (void*)this,
           (void*)aFrame);
    if (VERIFY_REFLOW_REALLY_NOISY_RC & gVerifyReflowFlags) {
      printf("Current content model:\n");
      Element* rootElement = mDocument->GetRootElement();
      if (rootElement) {
        rootElement->List(stdout, 0);
      }
    }
  }
#endif

  AutoTArray<nsIFrame*, 4> subtrees;
  subtrees.AppendElement(aFrame);

  do {
    nsIFrame* subtreeRoot = subtrees.PopLastElement();

    // Grab |wasDirty| now so we can go ahead and update the bits on
    // subtreeRoot.
    bool wasDirty = NS_SUBTREE_DIRTY(subtreeRoot);
    subtreeRoot->AddStateBits(aBitToAdd);

    // Determine whether we need to keep looking for the next ancestor
    // reflow root if subtreeRoot itself is a reflow root.
    bool targetNeedsReflowFromParent;
    switch (aRootHandling) {
      case ePositionOrSizeChange:
        targetNeedsReflowFromParent = true;
        break;
      case eNoPositionOrSizeChange:
        targetNeedsReflowFromParent = false;
        break;
      case eInferFromBitToAdd:
        targetNeedsReflowFromParent = (aBitToAdd == NS_FRAME_IS_DIRTY);
        break;
    }

#define FRAME_IS_REFLOW_ROOT(_f)                          \
  ((_f)->HasAnyStateBits(NS_FRAME_REFLOW_ROOT |           \
                         NS_FRAME_DYNAMIC_REFLOW_ROOT) && \
   ((_f) != subtreeRoot || !targetNeedsReflowFromParent))

    // Mark the intrinsic widths as dirty on the frame, all of its ancestors,
    // and all of its descendants, if needed:

    if (aIntrinsicDirty != nsIPresShell::eResize) {
      // Mark argument and all ancestors dirty. (Unless we hit a reflow
      // root that should contain the reflow.  That root could be
      // subtreeRoot itself if it's not dirty, or it could be some
      // ancestor of subtreeRoot.)
      for (nsIFrame* a = subtreeRoot; a && !FRAME_IS_REFLOW_ROOT(a);
           a = a->GetParent()) {
        a->MarkIntrinsicISizesDirty();
        if (a->HasAnyStateBits(NS_FRAME_OUT_OF_FLOW) &&
            a->IsAbsolutelyPositioned()) {
          // If we get here, 'a' is abspos, so its subtree's intrinsic sizing
          // has no effect on its ancestors' intrinsic sizing. So, don't loop
          // upwards any further.
          break;
        }
      }
    }

    if (aIntrinsicDirty == eStyleChange) {
      // Mark all descendants dirty (using an nsTArray stack rather than
      // recursion).
      // Note that ReflowInput::InitResizeFlags has some similar
      // code; see comments there for how and why it differs.
      AutoTArray<nsIFrame*, 32> stack;
      stack.AppendElement(subtreeRoot);

      do {
        nsIFrame* f = stack.PopLastElement();

        if (f->IsPlaceholderFrame()) {
          nsIFrame* oof = nsPlaceholderFrame::GetRealFrameForPlaceholder(f);
          if (!nsLayoutUtils::IsProperAncestorFrame(subtreeRoot, oof)) {
            // We have another distinct subtree we need to mark.
            subtrees.AppendElement(oof);
          }
        }

        nsIFrame::ChildListIterator lists(f);
        for (; !lists.IsDone(); lists.Next()) {
          for (nsIFrame* kid : lists.CurrentList()) {
            kid->MarkIntrinsicISizesDirty();
            stack.AppendElement(kid);
          }
        }
      } while (stack.Length() != 0);
    }

    // Skip setting dirty bits up the tree if we weren't given a bit to add.
    if (!aBitToAdd) {
      continue;
    }

    // Set NS_FRAME_HAS_DIRTY_CHILDREN bits (via nsIFrame::ChildIsDirty)
    // up the tree until we reach either a frame that's already dirty or
    // a reflow root.
    nsIFrame* f = subtreeRoot;
    for (;;) {
      if (FRAME_IS_REFLOW_ROOT(f) || !f->GetParent()) {
        // we've hit a reflow root or the root frame
        if (!wasDirty) {
          mDirtyRoots.Add(f);
          SetNeedLayoutFlush();
        }
#ifdef DEBUG
        else {
          VerifyHasDirtyRootAncestor(f);
        }
#endif

        break;
      }

      nsIFrame* child = f;
      f = f->GetParent();
      wasDirty = NS_SUBTREE_DIRTY(f);
      f->ChildIsDirty(child);
      NS_ASSERTION(f->GetStateBits() & NS_FRAME_HAS_DIRTY_CHILDREN,
                   "ChildIsDirty didn't do its job");
      if (wasDirty) {
        // This frame was already marked dirty.
#ifdef DEBUG
        VerifyHasDirtyRootAncestor(f);
#endif
        break;
      }
    }
  } while (subtrees.Length() != 0);

  MaybeScheduleReflow();
}

void PresShell::FrameNeedsToContinueReflow(nsIFrame* aFrame) {
  NS_ASSERTION(mIsReflowing, "Must be in reflow when marking path dirty.");
  MOZ_ASSERT(mCurrentReflowRoot, "Must have a current reflow root here");
  NS_ASSERTION(
      aFrame == mCurrentReflowRoot ||
          nsLayoutUtils::IsProperAncestorFrame(mCurrentReflowRoot, aFrame),
      "Frame passed in is not the descendant of mCurrentReflowRoot");
  NS_ASSERTION(aFrame->GetStateBits() & NS_FRAME_IN_REFLOW,
               "Frame passed in not in reflow?");

  mFramesToDirty.PutEntry(aFrame);
}

already_AddRefed<nsIContent> nsIPresShell::GetContentForScrolling() const {
  if (nsCOMPtr<nsIContent> focused = GetFocusedContentInOurWindow()) {
    return focused.forget();
  }
  return GetSelectedContentForScrolling();
}

already_AddRefed<nsIContent> nsIPresShell::GetSelectedContentForScrolling()
    const {
  nsCOMPtr<nsIContent> selectedContent;
  if (mSelection) {
    Selection* domSelection = mSelection->GetSelection(SelectionType::eNormal);
    if (domSelection) {
      selectedContent =
          nsIContent::FromNodeOrNull(domSelection->GetFocusNode());
    }
  }
  return selectedContent.forget();
}

nsIScrollableFrame* nsIPresShell::GetNearestScrollableFrame(
    nsIFrame* aFrame, nsIPresShell::ScrollDirection aDirection) {
  if (aDirection == nsIPresShell::eEither) {
    return nsLayoutUtils::GetNearestScrollableFrame(aFrame);
  }

  return nsLayoutUtils::GetNearestScrollableFrameForDirection(
      aFrame, aDirection == eVertical ? nsLayoutUtils::eVertical
                                      : nsLayoutUtils::eHorizontal);
}

nsIScrollableFrame* nsIPresShell::GetScrollableFrameToScrollForContent(
    nsIContent* aContent, nsIPresShell::ScrollDirection aDirection) {
  nsIScrollableFrame* scrollFrame = nullptr;
  if (aContent) {
    nsIFrame* startFrame = aContent->GetPrimaryFrame();
    if (startFrame) {
      scrollFrame = startFrame->GetScrollTargetFrame();
      if (scrollFrame) {
        startFrame = scrollFrame->GetScrolledFrame();
      }
      scrollFrame = GetNearestScrollableFrame(startFrame, aDirection);
    }
  }
  if (!scrollFrame) {
    scrollFrame = GetRootScrollFrameAsScrollable();
    if (!scrollFrame || !scrollFrame->GetScrolledFrame()) {
      return nullptr;
    }
    scrollFrame =
        GetNearestScrollableFrame(scrollFrame->GetScrolledFrame(), aDirection);
  }
  return scrollFrame;
}

nsIScrollableFrame* nsIPresShell::GetScrollableFrameToScroll(
    nsIPresShell::ScrollDirection aDirection) {
  nsCOMPtr<nsIContent> content = GetContentForScrolling();
  return GetScrollableFrameToScrollForContent(content.get(), aDirection);
}

void PresShell::CancelAllPendingReflows() {
  mDirtyRoots.Clear();

  if (mObservingLayoutFlushes) {
    GetPresContext()->RefreshDriver()->RemoveLayoutFlushObserver(this);
    mObservingLayoutFlushes = false;
  }

  ASSERT_REFLOW_SCHEDULED_STATE();
}

static bool DestroyFramesAndStyleDataFor(
    Element* aElement, nsPresContext& aPresContext,
    RestyleManager::IncludeRoot aIncludeRoot) {
  bool didReconstruct =
      aPresContext.FrameConstructor()->DestroyFramesFor(aElement);
  RestyleManager::ClearServoDataFromSubtree(aElement, aIncludeRoot);
  return didReconstruct;
}

void nsIPresShell::SlotAssignmentWillChange(Element& aElement,
                                            HTMLSlotElement* aOldSlot,
                                            HTMLSlotElement* aNewSlot) {
  MOZ_ASSERT(aOldSlot != aNewSlot);

  if (MOZ_UNLIKELY(!mDidInitialize)) {
    return;
  }

  // If the old slot is about to become empty, let layout know that it needs to
  // do work.
  if (aOldSlot && aOldSlot->AssignedNodes().Length() == 1) {
    DestroyFramesForAndRestyle(aOldSlot);
  }

  // Ensure the new element starts off clean.
  DestroyFramesAndStyleDataFor(&aElement, *mPresContext,
                               RestyleManager::IncludeRoot::Yes);

  if (aNewSlot) {
    // If the new slot will stop showing fallback content, we need to reframe it
    // altogether.
    if (aNewSlot->AssignedNodes().IsEmpty()) {
      DestroyFramesForAndRestyle(aNewSlot);
      // Otherwise we just care about the element, but we need to ensure that
      // something takes care of traversing to the relevant slot, if needed.
    } else if (aNewSlot->HasServoData() &&
               !Servo_Element_IsDisplayNone(aNewSlot)) {
      // Set the reframe bits...
      aNewSlot->NoteDescendantsNeedFramesForServo();
      aElement.SetFlags(NODE_NEEDS_FRAME);
      // Now the style dirty bits. Note that we can't just do
      // aElement.NoteDirtyForServo(), because the new slot is not setup yet.
      aNewSlot->SetHasDirtyDescendantsForServo();
      aNewSlot->NoteDirtySubtreeForServo();
    }
  }
}

#ifdef DEBUG
static void AssertNoFramesInSubtree(nsIContent* aContent) {
  for (nsINode* node : ShadowIncludingTreeIterator(*aContent)) {
    nsIContent* c = nsIContent::FromNode(node);
    MOZ_ASSERT(!c->GetPrimaryFrame());
    if (auto* binding = c->GetXBLBinding()) {
      if (auto* bindingWithContent = binding->GetBindingWithContent()) {
        nsIContent* anonContent = bindingWithContent->GetAnonymousContent();
        MOZ_ASSERT(!anonContent->GetPrimaryFrame());

        // Need to do this instead of just AssertNoFramesInSubtree(anonContent),
        // because the parent of the children of the <content> element isn't the
        // <content> element, but the bound element, and that confuses
        // GetNextNode a lot.
        for (nsIContent* child = anonContent->GetFirstChild(); child;
             child = child->GetNextSibling()) {
          AssertNoFramesInSubtree(child);
        }
      }
    }
  }
}
#endif

void nsIPresShell::DestroyFramesForAndRestyle(Element* aElement) {
#ifdef DEBUG
  auto postCondition =
      mozilla::MakeScopeExit([&]() { AssertNoFramesInSubtree(aElement); });
#endif

  MOZ_ASSERT(aElement);
  if (MOZ_UNLIKELY(!mDidInitialize)) {
    return;
  }

  if (!aElement->GetFlattenedTreeParentNode()) {
    // Nothing to do here, the element already is out of the frame tree.
    return;
  }

  nsAutoScriptBlocker scriptBlocker;

  // Mark ourselves as not safe to flush while we're doing frame destruction.
  ++mChangeNestCount;

  const bool didReconstruct = FrameConstructor()->DestroyFramesFor(aElement);

  // Clear the style data from all the flattened tree descendants, but _not_
  // from us, since otherwise we wouldn't see the reframe.
  RestyleManager::ClearServoDataFromSubtree(aElement,
                                            RestyleManager::IncludeRoot::No);

  auto changeHint =
      didReconstruct ? nsChangeHint(0) : nsChangeHint_ReconstructFrame;

  // NOTE(emilio): eRestyle_Subtree is needed to force also a full subtree
  // restyle for the content (in Stylo, where the existence of frames != the
  // existence of styles).
  mPresContext->RestyleManager()->PostRestyleEvent(aElement, eRestyle_Subtree,
                                                   changeHint);

  --mChangeNestCount;
}

void nsIPresShell::PostRecreateFramesFor(Element* aElement) {
  if (MOZ_UNLIKELY(!mDidInitialize)) {
    // Nothing to do here. In fact, if we proceed and aElement is the root, we
    // will crash.
    return;
  }

  mPresContext->RestyleManager()->PostRestyleEvent(
      aElement, nsRestyleHint(0), nsChangeHint_ReconstructFrame);
}

void nsIPresShell::RestyleForAnimation(Element* aElement, nsRestyleHint aHint) {
  // Now that we no longer have separate non-animation and animation
  // restyles, this method having a distinct identity is less important,
  // but it still seems useful to offer as a "more public" API and as a
  // chokepoint for these restyles to go through.
  mPresContext->RestyleManager()->PostRestyleEvent(aElement, aHint,
                                                   nsChangeHint(0));
}

void nsIPresShell::SetForwardingContainer(
    const WeakPtr<nsDocShell>& aContainer) {
  mForwardingContainer = aContainer;
}

void PresShell::ClearFrameRefs(nsIFrame* aFrame) {
  mPresContext->EventStateManager()->ClearFrameRefs(aFrame);

  AutoWeakFrame* weakFrame = mAutoWeakFrames;
  while (weakFrame) {
    AutoWeakFrame* prev = weakFrame->GetPreviousWeakFrame();
    if (weakFrame->GetFrame() == aFrame) {
      // This removes weakFrame from mAutoWeakFrames.
      weakFrame->Clear(this);
    }
    weakFrame = prev;
  }

  AutoTArray<WeakFrame*, 4> toRemove;
  for (auto iter = mWeakFrames.Iter(); !iter.Done(); iter.Next()) {
    WeakFrame* weakFrame = iter.Get()->GetKey();
    if (weakFrame->GetFrame() == aFrame) {
      toRemove.AppendElement(weakFrame);
    }
  }
  for (WeakFrame* weakFrame : toRemove) {
    weakFrame->Clear(this);
  }
}

already_AddRefed<gfxContext> PresShell::CreateReferenceRenderingContext() {
  nsDeviceContext* devCtx = mPresContext->DeviceContext();
  RefPtr<gfxContext> rc;
  if (mPresContext->IsScreen()) {
    rc = gfxContext::CreateOrNull(
        gfxPlatform::GetPlatform()->ScreenReferenceDrawTarget().get());
  } else {
    // We assume the devCtx has positive width and height for this call.
    // However, width and height, may be outside of the reasonable range
    // so rc may still be null.
    rc = devCtx->CreateReferenceRenderingContext();
  }

  return rc ? rc.forget() : nullptr;
}

nsresult PresShell::GoToAnchor(const nsAString& aAnchorName, bool aScroll,
                               uint32_t aAdditionalScrollFlags) {
  if (!mDocument) {
    return NS_ERROR_FAILURE;
  }

  const Element* root = mDocument->GetRootElement();
  if (root && root->IsSVGElement(nsGkAtoms::svg)) {
    // We need to execute this even if there is an empty anchor name
    // so that any existing SVG fragment identifier effect is removed
    if (SVGFragmentIdentifier::ProcessFragmentIdentifier(mDocument,
                                                         aAnchorName)) {
      return NS_OK;
    }
  }

  // Hold a reference to the ESM in case event dispatch tears us down.
  RefPtr<EventStateManager> esm = mPresContext->EventStateManager();

  if (aAnchorName.IsEmpty()) {
    NS_ASSERTION(!aScroll, "can't scroll to empty anchor name");
    esm->SetContentState(nullptr, NS_EVENT_STATE_URLTARGET);
    return NS_OK;
  }

  nsresult rv = NS_OK;
  nsCOMPtr<nsIContent> content;

  // Search for an element with a matching "id" attribute
  if (mDocument) {
    content = mDocument->GetElementById(aAnchorName);
  }

  // Search for an anchor element with a matching "name" attribute
  if (!content && mDocument->IsHTMLDocument()) {
    // Find a matching list of named nodes
    nsCOMPtr<nsINodeList> list = mDocument->GetElementsByName(aAnchorName);
    if (list) {
      // Loop through the named nodes looking for the first anchor
      uint32_t length = list->Length();
      for (uint32_t i = 0; i < length; i++) {
        nsIContent* node = list->Item(i);
        if (node->IsHTMLElement(nsGkAtoms::a)) {
          content = node;
          break;
        }
      }
    }
  }

  // Search for anchor in the HTML namespace with a matching name
  if (!content && !mDocument->IsHTMLDocument()) {
    NS_NAMED_LITERAL_STRING(nameSpace, "http://www.w3.org/1999/xhtml");
    // Get the list of anchor elements
    nsCOMPtr<nsINodeList> list =
        mDocument->GetElementsByTagNameNS(nameSpace, NS_LITERAL_STRING("a"));
    // Loop through the anchors looking for the first one with the given name.
    for (uint32_t i = 0; true; i++) {
      nsIContent* node = list->Item(i);
      if (!node) {  // End of list
        break;
      }

      // Compare the name attribute
      if (node->IsElement() &&
          node->AsElement()->AttrValueIs(kNameSpaceID_None, nsGkAtoms::name,
                                         aAnchorName, eCaseMatters)) {
        content = node;
        break;
      }
    }
  }

  esm->SetContentState(content, NS_EVENT_STATE_URLTARGET);

#ifdef ACCESSIBILITY
  nsIContent* anchorTarget = content;
#endif

  nsIScrollableFrame* rootScroll = GetRootScrollFrameAsScrollable();
  if (rootScroll && rootScroll->DidHistoryRestore()) {
    // Scroll position restored from history trumps scrolling to anchor.
    aScroll = false;
    rootScroll->ClearDidHistoryRestore();
  }

  if (content) {
    if (aScroll) {
      rv = ScrollContentIntoView(content, ScrollAxis(SCROLL_TOP, SCROLL_ALWAYS),
                                 ScrollAxis(),
                                 ANCHOR_SCROLL_FLAGS | aAdditionalScrollFlags);
      NS_ENSURE_SUCCESS(rv, rv);

      nsIScrollableFrame* rootScroll = GetRootScrollFrameAsScrollable();
      if (rootScroll) {
        mLastAnchorScrolledTo = content;
        mLastAnchorScrollPositionY = rootScroll->GetScrollPosition().y;
      }
    }

    // Should we select the target? This action is controlled by a
    // preference: the default is to not select.
    bool selectAnchor = Preferences::GetBool("layout.selectanchor");

    // Even if select anchor pref is false, we must still move the
    // caret there. That way tabbing will start from the new
    // location
    RefPtr<nsRange> jumpToRange = new nsRange(mDocument);
    while (content && content->GetFirstChild()) {
      content = content->GetFirstChild();
    }
    jumpToRange->SelectNodeContents(*content, IgnoreErrors());
    // Select the anchor
    RefPtr<Selection> sel = mSelection->GetSelection(SelectionType::eNormal);
    if (sel) {
      sel->RemoveAllRanges(IgnoreErrors());
      sel->AddRange(*jumpToRange, IgnoreErrors());
      if (!selectAnchor) {
        // Use a caret (collapsed selection) at the start of the anchor
        sel->CollapseToStart(IgnoreErrors());
      }
    }
    // Selection is at anchor.
    // Now focus the document itself if focus is on an element within it.
    nsPIDOMWindowOuter* win = mDocument->GetWindow();

    nsIFocusManager* fm = nsFocusManager::GetFocusManager();
    if (fm && win) {
      nsCOMPtr<mozIDOMWindowProxy> focusedWindow;
      fm->GetFocusedWindow(getter_AddRefs(focusedWindow));
      if (SameCOMIdentity(win, focusedWindow)) {
        fm->ClearFocus(focusedWindow);
      }
    }

    // If the target is an animation element, activate the animation
    if (content->IsNodeOfType(nsINode::eANIMATION)) {
      SVGContentUtils::ActivateByHyperlink(content.get());
    }
  } else {
    rv = NS_ERROR_FAILURE;
    NS_NAMED_LITERAL_STRING(top, "top");
    if (nsContentUtils::EqualsIgnoreASCIICase(aAnchorName, top)) {
      // Scroll to the top/left if aAnchorName is "top" and there is no element
      // with such a name or id.
      rv = NS_OK;
      nsIScrollableFrame* sf = GetRootScrollFrameAsScrollable();
      // Check |aScroll| after setting |rv| so we set |rv| to the same
      // thing whether or not |aScroll| is true.
      if (aScroll && sf) {
        // Scroll to the top of the page
        sf->ScrollTo(nsPoint(0, 0), nsIScrollableFrame::INSTANT);
      }
    }
  }

#ifdef ACCESSIBILITY
  if (anchorTarget) {
    nsAccessibilityService* accService = AccService();
    if (accService) accService->NotifyOfAnchorJumpTo(anchorTarget);
  }
#endif

  return rv;
}

nsresult PresShell::ScrollToAnchor() {
  if (!mLastAnchorScrolledTo) {
    return NS_OK;
  }
  NS_ASSERTION(mDidInitialize, "should have done initial reflow by now");

  nsIScrollableFrame* rootScroll = GetRootScrollFrameAsScrollable();
  if (!rootScroll ||
      mLastAnchorScrollPositionY != rootScroll->GetScrollPosition().y) {
    return NS_OK;
  }
  nsresult rv = ScrollContentIntoView(mLastAnchorScrolledTo,
                                      ScrollAxis(SCROLL_TOP, SCROLL_ALWAYS),
                                      ScrollAxis(), ANCHOR_SCROLL_FLAGS);
  mLastAnchorScrolledTo = nullptr;
  return rv;
}

/*
 * Helper (per-continuation) for ScrollContentIntoView.
 *
 * @param aContainerFrame [in] the frame which aRect is relative to
 * @param aFrame [in] Frame whose bounds should be unioned
 * @param aUseWholeLineHeightForInlines [in] if true, then for inline frames
 * we should include the top of the line in the added rectangle
 * @param aRect [inout] rect into which its bounds should be unioned
 * @param aHaveRect [inout] whether aRect contains data yet
 * @param aPrevBlock [inout] the block aLines is a line iterator for
 * @param aLines [inout] the line iterator we're using
 * @param aCurLine [inout] the line to start looking from in this iterator
 */
static void AccumulateFrameBounds(nsIFrame* aContainerFrame, nsIFrame* aFrame,
                                  bool aUseWholeLineHeightForInlines,
                                  nsRect& aRect, bool& aHaveRect,
                                  nsIFrame*& aPrevBlock,
                                  nsAutoLineIterator& aLines,
                                  int32_t& aCurLine) {
  nsIFrame* frame = aFrame;
  nsRect frameBounds = nsRect(nsPoint(0, 0), aFrame->GetSize());

  // If this is an inline frame and either the bounds height is 0 (quirks
  // layout model) or aUseWholeLineHeightForInlines is set, we need to
  // change the top of the bounds to include the whole line.
  if (frameBounds.height == 0 || aUseWholeLineHeightForInlines) {
    nsIFrame* prevFrame = aFrame;
    nsIFrame* f = aFrame;

    while (f && f->IsFrameOfType(nsIFrame::eLineParticipant) &&
           !f->IsTransformed() && !f->IsAbsPosContainingBlock()) {
      prevFrame = f;
      f = prevFrame->GetParent();
    }

    if (f != aFrame && f && f->IsBlockFrame()) {
      // find the line containing aFrame and increase the top of |offset|.
      if (f != aPrevBlock) {
        aLines = f->GetLineIterator();
        aPrevBlock = f;
        aCurLine = 0;
      }
      if (aLines) {
        int32_t index = aLines->FindLineContaining(prevFrame, aCurLine);
        if (index >= 0) {
          aCurLine = index;
          nsIFrame* trash1;
          int32_t trash2;
          nsRect lineBounds;

          if (NS_SUCCEEDED(
                  aLines->GetLine(index, &trash1, &trash2, lineBounds))) {
            frameBounds += frame->GetOffsetTo(f);
            frame = f;
            if (lineBounds.y < frameBounds.y) {
              frameBounds.height = frameBounds.YMost() - lineBounds.y;
              frameBounds.y = lineBounds.y;
            }
          }
        }
      }
    }
  }

  nsRect transformedBounds = nsLayoutUtils::TransformFrameRectToAncestor(
      frame, frameBounds, aContainerFrame);

  if (aHaveRect) {
    // We can't use nsRect::UnionRect since it drops empty rects on
    // the floor, and we need to include them.  (Thus we need
    // aHaveRect to know when to drop the initial value on the floor.)
    aRect.UnionRectEdges(aRect, transformedBounds);
  } else {
    aHaveRect = true;
    aRect = transformedBounds;
  }
}

static bool ComputeNeedToScroll(nsIPresShell::WhenToScroll aWhenToScroll,
                                nscoord aLineSize, nscoord aRectMin,
                                nscoord aRectMax, nscoord aViewMin,
                                nscoord aViewMax) {
  // See how the rect should be positioned vertically
  if (nsIPresShell::SCROLL_ALWAYS == aWhenToScroll) {
    // The caller wants the frame as visible as possible
    return true;
  } else if (nsIPresShell::SCROLL_IF_NOT_VISIBLE == aWhenToScroll) {
    // Scroll only if no part of the frame is visible in this view
    return aRectMax - aLineSize <= aViewMin || aRectMin + aLineSize >= aViewMax;
  } else if (nsIPresShell::SCROLL_IF_NOT_FULLY_VISIBLE == aWhenToScroll) {
    // Scroll only if part of the frame is hidden and more can fit in view
    return !(aRectMin >= aViewMin && aRectMax <= aViewMax) &&
           std::min(aViewMax, aRectMax) - std::max(aRectMin, aViewMin) <
               aViewMax - aViewMin;
  }
  return false;
}

static nscoord ComputeWhereToScroll(int16_t aWhereToScroll,
                                    nscoord aOriginalCoord, nscoord aRectMin,
                                    nscoord aRectMax, nscoord aViewMin,
                                    nscoord aViewMax, nscoord* aRangeMin,
                                    nscoord* aRangeMax) {
  nscoord resultCoord = aOriginalCoord;
  nscoord scrollPortLength = aViewMax - aViewMin;
  if (nsIPresShell::SCROLL_MINIMUM == aWhereToScroll) {
    // Scroll the minimum amount necessary to show as much as possible of the
    // frame. If the frame is too large, don't hide any initially visible part
    // of it.
    nscoord min = std::min(aRectMin, aRectMax - scrollPortLength);
    nscoord max = std::max(aRectMin, aRectMax - scrollPortLength);
    resultCoord = std::min(std::max(aOriginalCoord, min), max);
  } else {
    nscoord frameAlignCoord = NSToCoordRound(
        aRectMin + (aRectMax - aRectMin) * (aWhereToScroll / 100.0f));
    resultCoord = NSToCoordRound(frameAlignCoord -
                                 scrollPortLength * (aWhereToScroll / 100.0f));
  }
  // Force the scroll range to extend to include resultCoord.
  *aRangeMin = std::min(resultCoord, aRectMax - scrollPortLength);
  *aRangeMax = std::max(resultCoord, aRectMin);
  return resultCoord;
}

/**
 * This function takes a scrollable frame, a rect in the coordinate system
 * of the scrolled frame, and a desired percentage-based scroll
 * position and attempts to scroll the rect to that position in the
 * visual viewport.
 *
 * This needs to work even if aRect has a width or height of zero.
 *
 * Note that, since we are performing a layout scroll, it's possible that
 * this fnction will sometimes be unsuccessful; the content will move as
 * fast as it can on the screen using layout viewport scrolling, and then
 * stop there, even if it could get closer to the desired position by
 * moving the visual viewport within the layout viewport.
 */
static void ScrollToShowRect(nsIScrollableFrame* aFrameAsScrollable,
                             const nsRect& aRect,
                             nsIPresShell::ScrollAxis aVertical,
                             nsIPresShell::ScrollAxis aHorizontal,
                             uint32_t aFlags) {
  nsPoint scrollPt = aFrameAsScrollable->GetVisualViewportOffset();
  nsRect visibleRect(scrollPt, aFrameAsScrollable->GetVisualViewportSize());

  nsSize lineSize;
  // Don't call GetLineScrollAmount unless we actually need it. Not only
  // does this save time, but it's not safe to call GetLineScrollAmount
  // during reflow (because it depends on font size inflation and doesn't
  // use the in-reflow-safe font-size inflation path). If we did call it,
  // it would assert and possible give the wrong result.
  if (aVertical.mWhenToScroll == nsIPresShell::SCROLL_IF_NOT_VISIBLE ||
      aHorizontal.mWhenToScroll == nsIPresShell::SCROLL_IF_NOT_VISIBLE) {
    lineSize = aFrameAsScrollable->GetLineScrollAmount();
  }
  ScrollStyles ss = aFrameAsScrollable->GetScrollStyles();
  nsRect allowedRange(scrollPt, nsSize(0, 0));
  bool needToScroll = false;
  uint32_t directions = aFrameAsScrollable->GetPerceivedScrollingDirections();

  if (((aFlags & nsIPresShell::SCROLL_OVERFLOW_HIDDEN) ||
       ss.mVertical != StyleOverflow::Hidden) &&
      (!aVertical.mOnlyIfPerceivedScrollableDirection ||
       (directions & nsIScrollableFrame::VERTICAL))) {
    if (ComputeNeedToScroll(aVertical.mWhenToScroll, lineSize.height, aRect.y,
                            aRect.YMost(), visibleRect.y,
                            visibleRect.YMost())) {
      nscoord maxHeight;
      scrollPt.y = ComputeWhereToScroll(
          aVertical.mWhereToScroll, scrollPt.y, aRect.y, aRect.YMost(),
          visibleRect.y, visibleRect.YMost(), &allowedRange.y, &maxHeight);
      allowedRange.height = maxHeight - allowedRange.y;
      needToScroll = true;
    }
  }

  if (((aFlags & nsIPresShell::SCROLL_OVERFLOW_HIDDEN) ||
       ss.mHorizontal != StyleOverflow::Hidden) &&
      (!aHorizontal.mOnlyIfPerceivedScrollableDirection ||
       (directions & nsIScrollableFrame::HORIZONTAL))) {
    if (ComputeNeedToScroll(aHorizontal.mWhenToScroll, lineSize.width, aRect.x,
                            aRect.XMost(), visibleRect.x,
                            visibleRect.XMost())) {
      nscoord maxWidth;
      scrollPt.x = ComputeWhereToScroll(
          aHorizontal.mWhereToScroll, scrollPt.x, aRect.x, aRect.XMost(),
          visibleRect.x, visibleRect.XMost(), &allowedRange.x, &maxWidth);
      allowedRange.width = maxWidth - allowedRange.x;
      needToScroll = true;
    }
  }

  // If we don't need to scroll, then don't try since it might cancel
  // a current smooth scroll operation.
  if (needToScroll) {
    nsIScrollableFrame::ScrollMode scrollMode = nsIScrollableFrame::INSTANT;
    bool autoBehaviorIsSmooth =
        (aFrameAsScrollable->GetScrollStyles().mScrollBehavior ==
         NS_STYLE_SCROLL_BEHAVIOR_SMOOTH);
    bool smoothScroll =
        (aFlags & nsIPresShell::SCROLL_SMOOTH) ||
        ((aFlags & nsIPresShell::SCROLL_SMOOTH_AUTO) && autoBehaviorIsSmooth);
    if (gfxPrefs::ScrollBehaviorEnabled() && smoothScroll) {
      scrollMode = nsIScrollableFrame::SMOOTH_MSD;
    }
    aFrameAsScrollable->ScrollTo(scrollPt, scrollMode, &allowedRange);
  }
}

nsresult PresShell::ScrollContentIntoView(nsIContent* aContent,
                                          nsIPresShell::ScrollAxis aVertical,
                                          nsIPresShell::ScrollAxis aHorizontal,
                                          uint32_t aFlags) {
  NS_ENSURE_TRUE(aContent, NS_ERROR_NULL_POINTER);
  RefPtr<Document> composedDoc = aContent->GetComposedDoc();
  NS_ENSURE_STATE(composedDoc);

  NS_ASSERTION(mDidInitialize, "should have done initial reflow by now");

  if (mContentToScrollTo) {
    mContentToScrollTo->DeleteProperty(nsGkAtoms::scrolling);
  }
  mContentToScrollTo = aContent;
  ScrollIntoViewData* data = new ScrollIntoViewData();
  data->mContentScrollVAxis = aVertical;
  data->mContentScrollHAxis = aHorizontal;
  data->mContentToScrollToFlags = aFlags;
  if (NS_FAILED(mContentToScrollTo->SetProperty(
          nsGkAtoms::scrolling, data,
          nsINode::DeleteProperty<PresShell::ScrollIntoViewData>))) {
    mContentToScrollTo = nullptr;
  }

  // Flush layout and attempt to scroll in the process.
  if (nsIPresShell* shell = composedDoc->GetShell()) {
    shell->SetNeedLayoutFlush();
  }
  composedDoc->FlushPendingNotifications(FlushType::InterruptibleLayout);

  // If mContentToScrollTo is non-null, that means we interrupted the reflow
  // (or suppressed it altogether because we're suppressing interruptible
  // flushes right now) and won't necessarily get the position correct, but do
  // a best-effort scroll here.  The other option would be to do this inside
  // FlushPendingNotifications, but I'm not sure the repeated scrolling that
  // could trigger if reflows keep getting interrupted would be more desirable
  // than a single best-effort scroll followed by one final scroll on the first
  // completed reflow.
  if (mContentToScrollTo) {
    DoScrollContentIntoView();
  }
  return NS_OK;
}

void PresShell::DoScrollContentIntoView() {
  NS_ASSERTION(mDidInitialize, "should have done initial reflow by now");

  nsIFrame* frame = mContentToScrollTo->GetPrimaryFrame();
  if (!frame) {
    mContentToScrollTo->DeleteProperty(nsGkAtoms::scrolling);
    mContentToScrollTo = nullptr;
    return;
  }

  if (frame->GetStateBits() & NS_FRAME_FIRST_REFLOW) {
    // The reflow flush before this scroll got interrupted, and this frame's
    // coords and size are all zero, and it has no content showing anyway.
    // Don't bother scrolling to it.  We'll try again when we finish up layout.
    return;
  }

  // Make sure we skip 'frame' ... if it's scrollable, we should use its
  // scrollable ancestor as the container.
  nsIFrame* container = nsLayoutUtils::GetClosestFrameOfType(
      frame->GetParent(), LayoutFrameType::Scroll);
  if (!container) {
    // nothing can be scrolled
    return;
  }

  ScrollIntoViewData* data = static_cast<ScrollIntoViewData*>(
      mContentToScrollTo->GetProperty(nsGkAtoms::scrolling));
  if (MOZ_UNLIKELY(!data)) {
    mContentToScrollTo = nullptr;
    return;
  }

  // This is a two-step process.
  // Step 1: Find the bounds of the rect we want to scroll into view.  For
  //         example, for an inline frame we may want to scroll in the whole
  //         line, or we may want to scroll multiple lines into view.
  // Step 2: Walk container frame and its ancestors and scroll them
  //         appropriately.
  // frameBounds is relative to container. We're assuming
  // that scrollframes don't split so every continuation of frame will
  // be a descendant of container. (Things would still mostly work
  // even if that assumption was false.)
  nsRect frameBounds;
  bool haveRect = false;
  bool useWholeLineHeightForInlines = data->mContentScrollVAxis.mWhenToScroll !=
                                      nsIPresShell::SCROLL_IF_NOT_FULLY_VISIBLE;
  // Reuse the same line iterator across calls to AccumulateFrameBounds.  We set
  // it every time we detect a new block (stored in prevBlock).
  nsIFrame* prevBlock = nullptr;
  nsAutoLineIterator lines;
  // The last line we found a continuation on in |lines|.  We assume that later
  // continuations cannot come on earlier lines.
  int32_t curLine = 0;
  do {
    AccumulateFrameBounds(container, frame, useWholeLineHeightForInlines,
                          frameBounds, haveRect, prevBlock, lines, curLine);
  } while ((frame = frame->GetNextContinuation()));

  ScrollFrameRectIntoView(container, frameBounds, data->mContentScrollVAxis,
                          data->mContentScrollHAxis,
                          data->mContentToScrollToFlags);
}

bool PresShell::ScrollFrameRectIntoView(nsIFrame* aFrame, const nsRect& aRect,
                                        nsIPresShell::ScrollAxis aVertical,
                                        nsIPresShell::ScrollAxis aHorizontal,
                                        uint32_t aFlags) {
  bool didScroll = false;
  // This function needs to work even if rect has a width or height of 0.
  nsRect rect = aRect;
  nsIFrame* container = aFrame;
  // Walk up the frame hierarchy scrolling the rect into view and
  // keeping rect relative to container
  do {
    nsIScrollableFrame* sf = do_QueryFrame(container);
    if (sf) {
      nsPoint oldPosition = sf->GetScrollPosition();
      nsRect targetRect = rect;
      // Inflate the scrolled rect by the container's padding in each dimension,
      // unless we have 'overflow-clip-box-*: content-box' in that dimension.
      auto* disp = container->StyleDisplay();
      if (disp->mOverflowClipBoxBlock == StyleOverflowClipBox::ContentBox ||
          disp->mOverflowClipBoxInline == StyleOverflowClipBox::ContentBox) {
        WritingMode wm = container->GetWritingMode();
        bool cbH = (wm.IsVertical() ? disp->mOverflowClipBoxBlock
                                    : disp->mOverflowClipBoxInline) ==
                   StyleOverflowClipBox::ContentBox;
        bool cbV = (wm.IsVertical() ? disp->mOverflowClipBoxInline
                                    : disp->mOverflowClipBoxBlock) ==
                   StyleOverflowClipBox::ContentBox;
        nsMargin padding = container->GetUsedPadding();
        if (!cbH) {
          padding.left = padding.right = nscoord(0);
        }
        if (!cbV) {
          padding.top = padding.bottom = nscoord(0);
        }
        targetRect.Inflate(padding);
      }
      ScrollToShowRect(sf, targetRect - sf->GetScrolledFrame()->GetPosition(),
                       aVertical, aHorizontal, aFlags);
      nsPoint newPosition = sf->LastScrollDestination();
      // If the scroll position increased, that means our content moved up,
      // so our rect's offset should decrease
      rect += oldPosition - newPosition;

      if (oldPosition != newPosition) {
        didScroll = true;
      }

      // only scroll one container when this flag is set
      if (aFlags & nsIPresShell::SCROLL_FIRST_ANCESTOR_ONLY) {
        break;
      }
    }
    nsIFrame* parent;
    if (container->IsTransformed()) {
      container->GetTransformMatrix(nullptr, &parent);
      rect =
          nsLayoutUtils::TransformFrameRectToAncestor(container, rect, parent);
    } else {
      rect += container->GetPosition();
      parent = container->GetParent();
    }
    if (!parent && !(aFlags & nsIPresShell::SCROLL_NO_PARENT_FRAMES)) {
      nsPoint extraOffset(0, 0);
      parent = nsLayoutUtils::GetCrossDocParentFrame(container, &extraOffset);
      if (parent) {
        int32_t APD = container->PresContext()->AppUnitsPerDevPixel();
        int32_t parentAPD = parent->PresContext()->AppUnitsPerDevPixel();
        rect = rect.ScaleToOtherAppUnitsRoundOut(APD, parentAPD);
        rect += extraOffset;
      }
    }
    container = parent;
  } while (container);

  return didScroll;
}

nsRectVisibility PresShell::GetRectVisibility(nsIFrame* aFrame,
                                              const nsRect& aRect,
                                              nscoord aMinTwips) const {
  NS_ASSERTION(aFrame->PresContext() == GetPresContext(),
               "prescontext mismatch?");
  nsIFrame* rootFrame = mFrameConstructor->GetRootFrame();
  NS_ASSERTION(
      rootFrame,
      "How can someone have a frame for this presshell when there's no root?");
  nsIScrollableFrame* sf = GetRootScrollFrameAsScrollable();
  nsRect scrollPortRect;
  if (sf) {
    scrollPortRect = sf->GetScrollPortRect();
    nsIFrame* f = do_QueryFrame(sf);
    scrollPortRect += f->GetOffsetTo(rootFrame);
  } else {
    scrollPortRect = nsRect(nsPoint(0, 0), rootFrame->GetSize());
  }

  // scrollPortRect has the viewport visible area relative to rootFrame.
  nsRect visibleAreaRect(scrollPortRect);
  // Find the intersection of this and the frame's ancestor scrollable
  // frames. We walk the whole ancestor chain to find all the scrollable
  // frames.
  nsIScrollableFrame* scrollAncestorFrame =
      nsLayoutUtils::GetNearestScrollableFrame(
          aFrame, nsLayoutUtils::SCROLLABLE_INCLUDE_HIDDEN);
  while (scrollAncestorFrame) {
    nsRect scrollAncestorRect = scrollAncestorFrame->GetScrollPortRect();
    nsIFrame* f = do_QueryFrame(scrollAncestorFrame);
    scrollAncestorRect += f->GetOffsetTo(rootFrame);

    visibleAreaRect = visibleAreaRect.Intersect(scrollAncestorRect);

    // Continue up the chain.
    scrollAncestorFrame = nsLayoutUtils::GetNearestScrollableFrame(
        f->GetParent(), nsLayoutUtils::SCROLLABLE_INCLUDE_HIDDEN);
  }

  // aRect is in the aFrame coordinate space, so bring it into rootFrame
  // coordinate space.
  nsRect r = aRect + aFrame->GetOffsetTo(rootFrame);
  // If aRect is entirely visible then we don't need to ensure that
  // at least aMinTwips of it is visible
  if (visibleAreaRect.Contains(r)) {
    return nsRectVisibility_kVisible;
  }

  nsRect insetRect = visibleAreaRect;
  insetRect.Deflate(aMinTwips, aMinTwips);
  if (r.YMost() <= insetRect.y) return nsRectVisibility_kAboveViewport;
  if (r.y >= insetRect.YMost()) return nsRectVisibility_kBelowViewport;
  if (r.XMost() <= insetRect.x) return nsRectVisibility_kLeftOfViewport;
  if (r.x >= insetRect.XMost()) return nsRectVisibility_kRightOfViewport;

  return nsRectVisibility_kVisible;
}

void PresShell::ScheduleViewManagerFlush(PaintType aType) {
  if (MOZ_UNLIKELY(mIsDestroying)) {
    return;
  }

  if (aType == PAINT_DELAYED_COMPRESS) {
    // Delay paint for 1 second.
    static const uint32_t kPaintDelayPeriod = 1000;
    if (!mDelayedPaintTimer) {
      nsTimerCallbackFunc PaintTimerCallBack = [](nsITimer* aTimer,
                                                  void* aClosure) {
        // The passed-in PresShell is always alive here. Because if PresShell
        // died, mDelayedPaintTimer->Cancel() would be called during the
        // destruction and this callback would never be invoked.
        auto self = static_cast<PresShell*>(aClosure);
        self->SetNextPaintCompressed();
        self->ScheduleViewManagerFlush();
      };

      NS_NewTimerWithFuncCallback(
          getter_AddRefs(mDelayedPaintTimer), PaintTimerCallBack, this,
          kPaintDelayPeriod, nsITimer::TYPE_ONE_SHOT, "PaintTimerCallBack",
          mDocument->EventTargetFor(TaskCategory::Other));
    }
    return;
  }

  nsPresContext* presContext = GetPresContext();
  if (presContext) {
    presContext->RefreshDriver()->ScheduleViewManagerFlush();
  }
  SetNeedLayoutFlush();
}

void nsIPresShell::DispatchSynthMouseMove(WidgetGUIEvent* aEvent) {
  AUTO_PROFILER_TRACING_DOCSHELL("Paint", "DispatchSynthMouseMove",
                                 mPresContext->GetDocShell());
  nsEventStatus status = nsEventStatus_eIgnore;
  nsView* targetView = nsView::GetViewFor(aEvent->mWidget);
  if (!targetView) return;
  targetView->GetViewManager()->DispatchEvent(aEvent, targetView, &status);
}

void PresShell::ClearMouseCaptureOnView(nsView* aView) {
  if (gCaptureInfo.mContent) {
    if (aView) {
      // if a view was specified, ensure that the captured content is within
      // this view.
      nsIFrame* frame = gCaptureInfo.mContent->GetPrimaryFrame();
      if (frame) {
        nsView* view = frame->GetClosestView();
        // if there is no view, capturing won't be handled any more, so
        // just release the capture.
        if (view) {
          do {
            if (view == aView) {
              gCaptureInfo.mContent = nullptr;
              // the view containing the captured content likely disappeared so
              // disable capture for now.
              gCaptureInfo.mAllowed = false;
              break;
            }

            view = view->GetParent();
          } while (view);
          // return if the view wasn't found
          return;
        }
      }
    }

    gCaptureInfo.mContent = nullptr;
  }

  // disable mouse capture until the next mousedown as a dialog has opened
  // or a drag has started. Otherwise, someone could start capture during
  // the modal dialog or drag.
  gCaptureInfo.mAllowed = false;
}

void nsIPresShell::ClearMouseCapture(nsIFrame* aFrame) {
  if (!gCaptureInfo.mContent) {
    gCaptureInfo.mAllowed = false;
    return;
  }

  // null frame argument means clear the capture
  if (!aFrame) {
    gCaptureInfo.mContent = nullptr;
    gCaptureInfo.mAllowed = false;
    return;
  }

  nsIFrame* capturingFrame = gCaptureInfo.mContent->GetPrimaryFrame();
  if (!capturingFrame) {
    gCaptureInfo.mContent = nullptr;
    gCaptureInfo.mAllowed = false;
    return;
  }

  if (nsLayoutUtils::IsAncestorFrameCrossDoc(aFrame, capturingFrame)) {
    gCaptureInfo.mContent = nullptr;
    gCaptureInfo.mAllowed = false;
  }
}

nsresult PresShell::CaptureHistoryState(nsILayoutHistoryState** aState) {
  MOZ_ASSERT(nullptr != aState, "null state pointer");

  // We actually have to mess with the docshell here, since we want to
  // store the state back in it.
  // XXXbz this isn't really right, since this is being called in the
  // content viewer's Hide() method...  by that point the docshell's
  // state could be wrong.  We should sort out a better ownership
  // model for the layout history state.
  nsCOMPtr<nsIDocShell> docShell(mPresContext->GetDocShell());
  if (!docShell) return NS_ERROR_FAILURE;

  nsCOMPtr<nsILayoutHistoryState> historyState;
  docShell->GetLayoutHistoryState(getter_AddRefs(historyState));
  if (!historyState) {
    // Create the document state object
    historyState = NS_NewLayoutHistoryState();
    docShell->SetLayoutHistoryState(historyState);
  }

  *aState = historyState;
  NS_IF_ADDREF(*aState);

  // Capture frame state for the entire frame hierarchy
  nsIFrame* rootFrame = mFrameConstructor->GetRootFrame();
  if (!rootFrame) return NS_OK;

  mFrameConstructor->CaptureFrameState(rootFrame, historyState);

  return NS_OK;
}

void PresShell::ScheduleBeforeFirstPaint() {
  if (!mDocument->IsResourceDoc()) {
    // Notify observers that a new page is about to be drawn. Execute this
    // as soon as it is safe to run JS, which is guaranteed to be before we
    // go back to the event loop and actually draw the page.
    MOZ_LOG(gLog, LogLevel::Debug,
            ("PresShell::ScheduleBeforeFirstPaint this=%p", this));

    nsContentUtils::AddScriptRunner(
        new nsBeforeFirstPaintDispatcher(mDocument));
  }
}

void PresShell::UnsuppressAndInvalidate() {
  // Note: We ignore the EnsureVisible check for resource documents, because
  // they won't have a docshell, so they'll always fail EnsureVisible.
  if ((!mDocument->IsResourceDoc() && !mPresContext->EnsureVisible()) ||
      mHaveShutDown) {
    // No point; we're about to be torn down anyway.
    return;
  }

  ScheduleBeforeFirstPaint();

  mPaintingSuppressed = false;
  nsIFrame* rootFrame = mFrameConstructor->GetRootFrame();
  if (rootFrame) {
    // let's assume that outline on a root frame is not supported
    rootFrame->InvalidateFrame();
  }

  // now that painting is unsuppressed, focus may be set on the document
  if (nsPIDOMWindowOuter* win = mDocument->GetWindow()) win->SetReadyForFocus();

  if (!mHaveShutDown) {
    SynthesizeMouseMove(false);
    ScheduleApproximateFrameVisibilityUpdateNow();
  }
}

void PresShell::UnsuppressPainting() {
  if (mPaintSuppressionTimer) {
    mPaintSuppressionTimer->Cancel();
    mPaintSuppressionTimer = nullptr;
  }

  if (mIsDocumentGone || !mPaintingSuppressed) return;

  // If we have reflows pending, just wait until we process
  // the reflows and get all the frames where we want them
  // before actually unlocking the painting.  Otherwise
  // go ahead and unlock now.
  if (!mDirtyRoots.IsEmpty())
    mShouldUnsuppressPainting = true;
  else
    UnsuppressAndInvalidate();
}

// Post a request to handle an arbitrary callback after reflow has finished.
nsresult PresShell::PostReflowCallback(nsIReflowCallback* aCallback) {
  void* result = AllocateByObjectID(eArenaObjectID_nsCallbackEventRequest,
                                    sizeof(nsCallbackEventRequest));
  nsCallbackEventRequest* request = (nsCallbackEventRequest*)result;

  request->callback = aCallback;
  request->next = nullptr;

  if (mLastCallbackEventRequest) {
    mLastCallbackEventRequest = mLastCallbackEventRequest->next = request;
  } else {
    mFirstCallbackEventRequest = request;
    mLastCallbackEventRequest = request;
  }

  return NS_OK;
}

void PresShell::CancelReflowCallback(nsIReflowCallback* aCallback) {
  nsCallbackEventRequest* before = nullptr;
  nsCallbackEventRequest* node = mFirstCallbackEventRequest;
  while (node) {
    nsIReflowCallback* callback = node->callback;

    if (callback == aCallback) {
      nsCallbackEventRequest* toFree = node;
      if (node == mFirstCallbackEventRequest) {
        node = node->next;
        mFirstCallbackEventRequest = node;
        NS_ASSERTION(before == nullptr, "impossible");
      } else {
        node = node->next;
        before->next = node;
      }

      if (toFree == mLastCallbackEventRequest) {
        mLastCallbackEventRequest = before;
      }

      FreeByObjectID(eArenaObjectID_nsCallbackEventRequest, toFree);
    } else {
      before = node;
      node = node->next;
    }
  }
}

void PresShell::CancelPostedReflowCallbacks() {
  while (mFirstCallbackEventRequest) {
    nsCallbackEventRequest* node = mFirstCallbackEventRequest;
    mFirstCallbackEventRequest = node->next;
    if (!mFirstCallbackEventRequest) {
      mLastCallbackEventRequest = nullptr;
    }
    nsIReflowCallback* callback = node->callback;
    FreeByObjectID(eArenaObjectID_nsCallbackEventRequest, node);
    if (callback) {
      callback->ReflowCallbackCanceled();
    }
  }
}

void PresShell::HandlePostedReflowCallbacks(bool aInterruptible) {
  bool shouldFlush = false;

  while (mFirstCallbackEventRequest) {
    nsCallbackEventRequest* node = mFirstCallbackEventRequest;
    mFirstCallbackEventRequest = node->next;
    if (!mFirstCallbackEventRequest) {
      mLastCallbackEventRequest = nullptr;
    }
    nsIReflowCallback* callback = node->callback;
    FreeByObjectID(eArenaObjectID_nsCallbackEventRequest, node);
    if (callback) {
      if (callback->ReflowFinished()) {
        shouldFlush = true;
      }
    }
  }

  FlushType flushType =
      aInterruptible ? FlushType::InterruptibleLayout : FlushType::Layout;
  if (shouldFlush && !mIsDestroying) {
    FlushPendingNotifications(flushType);
  }
}

bool nsIPresShell::IsSafeToFlush() const {
  // Not safe if we are getting torn down, reflowing, or in the middle of frame
  // construction.
  if (mIsReflowing || mChangeNestCount || mIsDestroying) {
    return false;
  }

  // Not safe if we are painting
  if (nsViewManager* viewManager = GetViewManager()) {
    bool isPainting = false;
    viewManager->IsPainting(isPainting);
    if (isPainting) {
      return false;
    }
  }

  return true;
}

void nsIPresShell::NotifyFontFaceSetOnRefresh() {
  if (FontFaceSet* set = mDocument->GetFonts()) {
    set->DidRefresh();
  }
}

void PresShell::DoFlushPendingNotifications(FlushType aType) {
  // by default, flush animations if aType >= FlushType::Style
  mozilla::ChangesToFlush flush(aType, aType >= FlushType::Style);
  FlushPendingNotifications(flush);
}

#ifdef DEBUG
static void AssertFrameSubtreeIsSane(const nsIFrame& aRoot) {
  if (const nsIContent* content = aRoot.GetContent()) {
    MOZ_ASSERT(content->GetFlattenedTreeParentNodeForStyle(),
               "Node not in the flattened tree still has a frame?");
  }

  nsIFrame::ChildListIterator childLists(&aRoot);
  for (; !childLists.IsDone(); childLists.Next()) {
    for (const nsIFrame* child : childLists.CurrentList()) {
      AssertFrameSubtreeIsSane(*child);
    }
  }
}
#endif

static inline void AssertFrameTreeIsSane(const nsIPresShell& aShell) {
#ifdef DEBUG
  if (const nsIFrame* root = aShell.GetRootFrame()) {
    AssertFrameSubtreeIsSane(*root);
  }
#endif
}

void PresShell::DoFlushPendingNotifications(mozilla::ChangesToFlush aFlush) {
  // Per our API contract, hold a strong ref to ourselves until we return.
  nsCOMPtr<nsIPresShell> kungFuDeathGrip = this;

  /**
   * VERY IMPORTANT: If you add some sort of new flushing to this
   * method, make sure to add the relevant SetNeedLayoutFlush or
   * SetNeedStyleFlush calls on the shell.
   */
  FlushType flushType = aFlush.mFlushType;

  MOZ_ASSERT(NeedFlush(flushType), "Why did we get called?");

#ifdef MOZ_GECKO_PROFILER
  // clang-format off
  static const EnumeratedArray<FlushType, FlushType::Count, const char*>
      flushTypeNames = {
    "",
    "Event",
    "Content",
    "ContentAndNotify",
    // As far as the profiler is concerned, EnsurePresShellInitAndFrames and
    // Frames are the same
    "Style",
    "Style",
    "InterruptibleLayout",
    "Layout",
    "Display"
  };
  // clang-format on
  AUTO_PROFILER_LABEL_DYNAMIC_CSTR("PresShell::DoFlushPendingNotifications",
                                   LAYOUT, flushTypeNames[flushType]);
#endif

#ifdef ACCESSIBILITY
#ifdef DEBUG
  if (nsAccessibilityService* accService = GetAccService()) {
    NS_ASSERTION(!accService->IsProcessingRefreshDriverNotification(),
                 "Flush during accessible tree update!");
  }
#endif
#endif

  NS_ASSERTION(flushType >= FlushType::Frames, "Why did we get called?");

  mNeedStyleFlush = false;
  mNeedThrottledAnimationFlush =
      mNeedThrottledAnimationFlush && !aFlush.mFlushAnimations;
  mNeedLayoutFlush =
      mNeedLayoutFlush && (flushType < FlushType::InterruptibleLayout);

  bool isSafeToFlush = IsSafeToFlush();

  // If layout could possibly trigger scripts, then it's only safe to flush if
  // it's safe to run script.
  bool hasHadScriptObject;
  if (mDocument->GetScriptHandlingObject(hasHadScriptObject) ||
      hasHadScriptObject) {
    isSafeToFlush = isSafeToFlush && nsContentUtils::IsSafeToRunScript();
  }

  MOZ_DIAGNOSTIC_ASSERT(!mIsDestroying || !isSafeToFlush);
  MOZ_DIAGNOSTIC_ASSERT(mIsDestroying || mViewManager);
  MOZ_DIAGNOSTIC_ASSERT(mIsDestroying || mDocument->HasShellOrBFCacheEntry());
  MOZ_DIAGNOSTIC_ASSERT(mIsDestroying || mDocument->GetShell() == this);

  // Make sure the view manager stays alive.
  RefPtr<nsViewManager> viewManager = mViewManager;
  bool didStyleFlush = false;
  bool didLayoutFlush = false;
  if (isSafeToFlush) {
    // Record that we are in a flush, so that our optimization in
    // Document::FlushPendingNotifications doesn't skip any re-entrant
    // calls to us.  Otherwise, we might miss some needed flushes, since
    // we clear mNeedStyleFlush / mNeedLayoutFlush here at the top of
    // the function but we might not have done the work yet.
    AutoRestore<bool> guard(mInFlush);
    mInFlush = true;

    // We need to make sure external resource documents are flushed too (for
    // example, svg filters that reference a filter in an external document
    // need the frames in the external document to be constructed for the
    // filter to work). We only need external resources to be flushed when the
    // main document is flushing >= FlushType::Frames, so we flush external
    // resources here instead of Document::FlushPendingNotifications.
    mDocument->FlushExternalResources(flushType);

    // Force flushing of any pending content notifications that might have
    // queued up while our event was pending.  That will ensure that we don't
    // construct frames for content right now that's still waiting to be
    // notified on,
    mDocument->FlushPendingNotifications(FlushType::ContentAndNotify);

    mDocument->UpdateSVGUseElementShadowTrees();

    // Process pending restyles, since any flush of the presshell wants
    // up-to-date style data.
    if (MOZ_LIKELY(!mIsDestroying)) {
      viewManager->FlushDelayedResize(false);
      mPresContext->FlushPendingMediaFeatureValuesChanged();
    }

    if (MOZ_LIKELY(!mIsDestroying)) {
      // Now that we have flushed media queries, update the rules before looking
      // up @font-face / @counter-style / @font-feature-values rules.
      mStyleSet->UpdateStylistIfNeeded();

      // Flush any pending update of the user font set, since that could
      // cause style changes (for updating ex/ch units, and to cause a
      // reflow).
      mDocument->FlushUserFontSet();

      mPresContext->FlushCounterStyles();

      mPresContext->FlushFontFeatureValues();

      // Flush any requested SMIL samples.
      if (mDocument->HasAnimationController()) {
        mDocument->GetAnimationController()->FlushResampleRequests();
      }

      if (aFlush.mFlushAnimations && mPresContext->EffectCompositor()) {
        mPresContext->EffectCompositor()->PostRestyleForThrottledAnimations();
      }
    }

    // The FlushResampleRequests() above flushed style changes.
    if (MOZ_LIKELY(!mIsDestroying)) {
      nsAutoScriptBlocker scriptBlocker;
#ifdef MOZ_GECKO_PROFILER
      nsCOMPtr<nsIDocShell> docShell = mPresContext->GetDocShell();
      DECLARE_DOCSHELL_AND_HISTORY_ID(docShell);
      AutoProfilerStyleMarker tracingStyleFlush(std::move(mStyleCause),
                                                docShellId, docShellHistoryId);
#endif

      mPresContext->RestyleManager()->ProcessPendingRestyles();
    }

    // Process whatever XBL constructors those restyles queued up.  This
    // ensures that onload doesn't fire too early and that we won't do extra
    // reflows after those constructors run.
    if (MOZ_LIKELY(!mIsDestroying)) {
      mDocument->BindingManager()->ProcessAttachedQueue();
    }

    // Now those constructors or events might have posted restyle
    // events.  At the same time, we still need up-to-date style data.
    // In particular, reflow depends on style being completely up to
    // date.  If it's not, then style reparenting, which can
    // happen during reflow, might suddenly pick up the new rules and
    // we'll end up with frames whose style doesn't match the frame
    // type.
    if (MOZ_LIKELY(!mIsDestroying)) {
      nsAutoScriptBlocker scriptBlocker;
#ifdef MOZ_GECKO_PROFILER
      nsCOMPtr<nsIDocShell> docShell = mPresContext->GetDocShell();
      DECLARE_DOCSHELL_AND_HISTORY_ID(docShell);
      AutoProfilerStyleMarker tracingStyleFlush(std::move(mStyleCause),
                                                docShellId, docShellHistoryId);
#endif

      mPresContext->RestyleManager()->ProcessPendingRestyles();
      // Clear mNeedStyleFlush here agagin to make this flag work properly for
      // optimization since the flag might have set in ProcessPendingRestyles().
      mNeedStyleFlush = false;
    }

    AssertFrameTreeIsSane(*this);

    didStyleFlush = true;

    // There might be more pending constructors now, but we're not going to
    // worry about them.  They can't be triggered during reflow, so we should
    // be good.

    if (flushType >= (SuppressInterruptibleReflows()
                          ? FlushType::Layout
                          : FlushType::InterruptibleLayout) &&
        !mIsDestroying) {
      didLayoutFlush = true;
      mFrameConstructor->RecalcQuotesAndCounters();
      viewManager->FlushDelayedResize(true);
      if (ProcessReflowCommands(flushType < FlushType::Layout) &&
          mContentToScrollTo) {
        // We didn't get interrupted.  Go ahead and scroll to our content
        DoScrollContentIntoView();
        if (mContentToScrollTo) {
          mContentToScrollTo->DeleteProperty(nsGkAtoms::scrolling);
          mContentToScrollTo = nullptr;
        }
      }
    }

    if (flushType >= FlushType::Layout) {
      if (!mIsDestroying) {
        viewManager->UpdateWidgetGeometry();
      }
    }
  }

  if (!didStyleFlush && flushType >= FlushType::Style && !mIsDestroying) {
    SetNeedStyleFlush();
    if (aFlush.mFlushAnimations) {
      SetNeedThrottledAnimationFlush();
    }
  }

  if (!didLayoutFlush && flushType >= FlushType::InterruptibleLayout &&
      !mIsDestroying) {
    // We suppressed this flush either due to it not being safe to flush,
    // or due to SuppressInterruptibleReflows().  Either way, the
    // mNeedLayoutFlush flag needs to be re-set.
    SetNeedLayoutFlush();
  }
}

void PresShell::CharacterDataChanged(nsIContent* aContent,
                                     const CharacterDataChangeInfo& aInfo) {
  MOZ_ASSERT(!mIsDocumentGone, "Unexpected CharacterDataChanged");
  MOZ_ASSERT(aContent->OwnerDoc() == mDocument, "Unexpected document");

  nsAutoCauseReflowNotifier crNotifier(this);

  mPresContext->RestyleManager()->CharacterDataChanged(aContent, aInfo);
  mFrameConstructor->CharacterDataChanged(aContent, aInfo);
}

void PresShell::ContentStateChanged(Document* aDocument, nsIContent* aContent,
                                    EventStates aStateMask) {
  MOZ_ASSERT(!mIsDocumentGone, "Unexpected ContentStateChanged");
  MOZ_ASSERT(aDocument == mDocument, "Unexpected aDocument");

  if (mDidInitialize) {
    nsAutoCauseReflowNotifier crNotifier(this);
    mPresContext->RestyleManager()->ContentStateChanged(aContent, aStateMask);
  }
}

void PresShell::DocumentStatesChanged(Document* aDocument,
                                      EventStates aStateMask) {
  MOZ_ASSERT(!mIsDocumentGone, "Unexpected DocumentStatesChanged");
  MOZ_ASSERT(aDocument == mDocument, "Unexpected aDocument");
  MOZ_ASSERT(!aStateMask.IsEmpty());

  if (mDidInitialize) {
    mStyleSet->InvalidateStyleForDocumentStateChanges(aStateMask);
  }

  if (aStateMask.HasState(NS_DOCUMENT_STATE_WINDOW_INACTIVE)) {
    if (nsIFrame* root = mFrameConstructor->GetRootFrame()) {
      root->SchedulePaint();
    }
  }
}

void PresShell::AttributeWillChange(Element* aElement, int32_t aNameSpaceID,
                                    nsAtom* aAttribute, int32_t aModType,
                                    const nsAttrValue* aNewValue) {
  MOZ_ASSERT(!mIsDocumentGone, "Unexpected AttributeWillChange");
  MOZ_ASSERT(aElement->OwnerDoc() == mDocument, "Unexpected document");

  // XXXwaterson it might be more elegant to wait until after the
  // initial reflow to begin observing the document. That would
  // squelch any other inappropriate notifications as well.
  if (mDidInitialize) {
    nsAutoCauseReflowNotifier crNotifier(this);
    mPresContext->RestyleManager()->AttributeWillChange(
        aElement, aNameSpaceID, aAttribute, aModType, aNewValue);
  }
}

void PresShell::AttributeChanged(Element* aElement, int32_t aNameSpaceID,
                                 nsAtom* aAttribute, int32_t aModType,
                                 const nsAttrValue* aOldValue) {
  MOZ_ASSERT(!mIsDocumentGone, "Unexpected AttributeChanged");
  MOZ_ASSERT(aElement->OwnerDoc() == mDocument, "Unexpected document");

  // XXXwaterson it might be more elegant to wait until after the
  // initial reflow to begin observing the document. That would
  // squelch any other inappropriate notifications as well.
  if (mDidInitialize) {
    nsAutoCauseReflowNotifier crNotifier(this);
    mPresContext->RestyleManager()->AttributeChanged(
        aElement, aNameSpaceID, aAttribute, aModType, aOldValue);
  }
}

void PresShell::ContentAppended(nsIContent* aFirstNewContent) {
  MOZ_ASSERT(!mIsDocumentGone, "Unexpected ContentAppended");
  MOZ_ASSERT(aFirstNewContent->OwnerDoc() == mDocument, "Unexpected document");

  // We never call ContentAppended with a document as the container, so we can
  // assert that we have an nsIContent parent.
  MOZ_ASSERT(aFirstNewContent->GetParent());
  MOZ_ASSERT(aFirstNewContent->GetParent()->IsElement() ||
             aFirstNewContent->GetParent()->IsShadowRoot());

  if (!mDidInitialize) {
    return;
  }

  nsAutoCauseReflowNotifier crNotifier(this);

  // Call this here so it only happens for real content mutations and
  // not cases when the frame constructor calls its own methods to force
  // frame reconstruction.
  mPresContext->RestyleManager()->ContentAppended(aFirstNewContent);

  mFrameConstructor->ContentAppended(
      aFirstNewContent, nsCSSFrameConstructor::InsertionKind::Async);
}

void PresShell::ContentInserted(nsIContent* aChild) {
  MOZ_ASSERT(!mIsDocumentGone, "Unexpected ContentInserted");
  MOZ_ASSERT(aChild->OwnerDoc() == mDocument, "Unexpected document");

  if (!mDidInitialize) {
    return;
  }

  nsAutoCauseReflowNotifier crNotifier(this);

  // Call this here so it only happens for real content mutations and
  // not cases when the frame constructor calls its own methods to force
  // frame reconstruction.
  mPresContext->RestyleManager()->ContentInserted(aChild);

  mFrameConstructor->ContentInserted(
      aChild, nullptr, nsCSSFrameConstructor::InsertionKind::Async);
}

void PresShell::ContentRemoved(nsIContent* aChild,
                               nsIContent* aPreviousSibling) {
  MOZ_ASSERT(!mIsDocumentGone, "Unexpected ContentRemoved");
  MOZ_ASSERT(aChild->OwnerDoc() == mDocument, "Unexpected document");
  nsINode* container = aChild->GetParentNode();

  // Notify the ESM that the content has been removed, so that
  // it can clean up any state related to the content.

  mPresContext->EventStateManager()->ContentRemoved(mDocument, aChild);

  nsAutoCauseReflowNotifier crNotifier(this);

  // Call this here so it only happens for real content mutations and
  // not cases when the frame constructor calls its own methods to force
  // frame reconstruction.
  nsIContent* oldNextSibling = nullptr;

  // Editor calls into here with NAC via HTMLEditor::DeleteRefToAnonymousNode.
  // This could be asserted if that caller is fixed.
  if (MOZ_LIKELY(!aChild->IsRootOfAnonymousSubtree())) {
    oldNextSibling = aPreviousSibling ? aPreviousSibling->GetNextSibling()
                                      : container->GetFirstChild();
  }

  // After removing aChild from tree we should save information about live
  // ancestor
  if (mPointerEventTarget &&
      nsContentUtils::ContentIsDescendantOf(mPointerEventTarget, aChild)) {
    mPointerEventTarget = aChild->GetParent();
  }

  mFrameConstructor->ContentRemoved(aChild, oldNextSibling,
                                    nsCSSFrameConstructor::REMOVE_CONTENT);

  // NOTE(emilio): It's important that this goes after the frame constructor
  // stuff, otherwise the frame constructor can't see elements which are
  // display: contents / display: none, because we'd have cleared all the style
  // data from there.
  mPresContext->RestyleManager()->ContentRemoved(aChild, oldNextSibling);
}

void PresShell::NotifyCounterStylesAreDirty() {
  nsAutoCauseReflowNotifier reflowNotifier(this);
  mFrameConstructor->NotifyCounterStylesAreDirty();
}

bool nsIPresShell::FrameIsAncestorOfDirtyRoot(nsIFrame* aFrame) const {
  return mDirtyRoots.FrameIsAncestorOfDirtyRoot(aFrame);
}

void PresShell::ReconstructFrames() {
  MOZ_ASSERT(!mFrameConstructor->GetRootFrame() || mDidInitialize,
             "Must not have root frame before initial reflow");
  if (!mDidInitialize || mIsDestroying) {
    // Nothing to do here
    return;
  }

  nsCOMPtr<nsIPresShell> kungFuDeathGrip(this);

  // Have to make sure that the content notifications are flushed before we
  // start messing with the frame model; otherwise we can get content doubling.
  //
  // Also make sure that styles are flushed before calling into the frame
  // constructor, since that's what it expects.
  mDocument->FlushPendingNotifications(FlushType::Style);

  if (mIsDestroying) {
    return;
  }

  nsAutoCauseReflowNotifier crNotifier(this);
  mFrameConstructor->ReconstructDocElementHierarchy(
      nsCSSFrameConstructor::InsertionKind::Sync);
}

void nsIPresShell::ApplicableStylesChanged() {
  if (mIsDestroying) {
    // We don't want to mess with restyles at this point
    return;
  }

  EnsureStyleFlush();
  mDocument->MarkUserFontSetDirty();

  if (mPresContext) {
    mPresContext->MarkCounterStylesDirty();
    mPresContext->MarkFontFeatureValuesDirty();
    mPresContext->RestyleManager()->NextRestyleIsForCSSRuleChanges();
  }
}

nsresult PresShell::RenderDocument(const nsRect& aRect, uint32_t aFlags,
                                   nscolor aBackgroundColor,
                                   gfxContext* aThebesContext) {
  NS_ENSURE_TRUE(!(aFlags & RENDER_IS_UNTRUSTED), NS_ERROR_NOT_IMPLEMENTED);

  nsRootPresContext* rootPresContext = mPresContext->GetRootPresContext();
  if (rootPresContext) {
    rootPresContext->FlushWillPaintObservers();
    if (mIsDestroying) return NS_OK;
  }

  nsAutoScriptBlocker blockScripts;

  // Set up the rectangle as the path in aThebesContext
  gfxRect r(0, 0, nsPresContext::AppUnitsToFloatCSSPixels(aRect.width),
            nsPresContext::AppUnitsToFloatCSSPixels(aRect.height));
  aThebesContext->NewPath();
#ifdef MOZ_GFX_OPTIMIZE_MOBILE
  aThebesContext->SnappedRectangle(r);
#else
  aThebesContext->Rectangle(r);
#endif

  nsIFrame* rootFrame = mFrameConstructor->GetRootFrame();
  if (!rootFrame) {
    // Nothing to paint, just fill the rect
    aThebesContext->SetColor(Color::FromABGR(aBackgroundColor));
    aThebesContext->Fill();
    return NS_OK;
  }

  gfxContextAutoSaveRestore save(aThebesContext);

  MOZ_ASSERT(aThebesContext->CurrentOp() == CompositionOp::OP_OVER);

  aThebesContext->Clip();

  nsDeviceContext* devCtx = mPresContext->DeviceContext();

  gfxPoint offset(-nsPresContext::AppUnitsToFloatCSSPixels(aRect.x),
                  -nsPresContext::AppUnitsToFloatCSSPixels(aRect.y));
  gfxFloat scale =
      gfxFloat(devCtx->AppUnitsPerDevPixel()) / AppUnitsPerCSSPixel();

  // Since canvas APIs use floats to set up their matrices, we may have some
  // slight rounding errors here.  We use NudgeToIntegers() here to adjust
  // matrix components that are integers up to the accuracy of floats to be
  // those integers.
  gfxMatrix newTM = aThebesContext->CurrentMatrixDouble()
                        .PreTranslate(offset)
                        .PreScale(scale, scale)
                        .NudgeToIntegers();
  aThebesContext->SetMatrixDouble(newTM);

  AutoSaveRestoreRenderingState _(this);

  bool wouldFlushRetainedLayers = false;
  PaintFrameFlags flags = PaintFrameFlags::PAINT_IGNORE_SUPPRESSION;
  if (aThebesContext->CurrentMatrix().HasNonIntegerTranslation()) {
    flags |= PaintFrameFlags::PAINT_IN_TRANSFORM;
  }
  if (!(aFlags & RENDER_ASYNC_DECODE_IMAGES)) {
    flags |= PaintFrameFlags::PAINT_SYNC_DECODE_IMAGES;
  }
  if (aFlags & RENDER_USE_WIDGET_LAYERS) {
    // We only support using widget layers on display root's with widgets.
    nsView* view = rootFrame->GetView();
    if (view && view->GetWidget() &&
        nsLayoutUtils::GetDisplayRootFrame(rootFrame) == rootFrame) {
      LayerManager* layerManager = view->GetWidget()->GetLayerManager();
      // ClientLayerManagers or WebRenderLayerManagers in content processes
      // don't support taking snapshots.
      if (layerManager &&
          (!layerManager->AsKnowsCompositor() || XRE_IsParentProcess())) {
        flags |= PaintFrameFlags::PAINT_WIDGET_LAYERS;
      }
    }
  }
  if (!(aFlags & RENDER_CARET)) {
    wouldFlushRetainedLayers = true;
    flags |= PaintFrameFlags::PAINT_HIDE_CARET;
  }
  if (aFlags & RENDER_IGNORE_VIEWPORT_SCROLLING) {
    wouldFlushRetainedLayers = !IgnoringViewportScrolling();
    mRenderFlags =
        ChangeFlag(mRenderFlags, true, STATE_IGNORING_VIEWPORT_SCROLLING);
  }
  if (aFlags & RENDER_DRAWWINDOW_NOT_FLUSHING) {
    mRenderFlags =
        ChangeFlag(mRenderFlags, true, STATE_DRAWWINDOW_NOT_FLUSHING);
  }
  if (aFlags & RENDER_DOCUMENT_RELATIVE) {
    // XXX be smarter about this ... drawWindow might want a rect
    // that's "pretty close" to what our retained layer tree covers.
    // In that case, it wouldn't disturb normal rendering too much,
    // and we should allow it.
    wouldFlushRetainedLayers = true;
    flags |= PaintFrameFlags::PAINT_DOCUMENT_RELATIVE;
  }

  // Don't let drawWindow blow away our retained layer tree
  if ((flags & PaintFrameFlags::PAINT_WIDGET_LAYERS) &&
      wouldFlushRetainedLayers) {
    flags &= ~PaintFrameFlags::PAINT_WIDGET_LAYERS;
  }

  nsLayoutUtils::PaintFrame(aThebesContext, rootFrame, nsRegion(aRect),
                            aBackgroundColor,
                            nsDisplayListBuilderMode::PAINTING, flags);

  return NS_OK;
}

/*
 * Clip the display list aList to a range. Returns the clipped
 * rectangle surrounding the range.
 */
nsRect PresShell::ClipListToRange(nsDisplayListBuilder* aBuilder,
                                  nsDisplayList* aList, nsRange* aRange) {
  // iterate though the display items and add up the bounding boxes of each.
  // This will allow the total area of the frames within the range to be
  // determined. To do this, remove an item from the bottom of the list, check
  // whether it should be part of the range, and if so, append it to the top
  // of the temporary list tmpList. If the item is a text frame at the end of
  // the selection range, clip it to the portion of the text frame that is
  // part of the selection. Then, append the wrapper to the top of the list.
  // Otherwise, just delete the item and don't append it.
  nsRect surfaceRect;
  nsDisplayList tmpList;

  nsDisplayItem* i;
  while ((i = aList->RemoveBottom())) {
    // itemToInsert indiciates the item that should be inserted into the
    // temporary list. If null, no item should be inserted.
    nsDisplayItem* itemToInsert = nullptr;
    nsIFrame* frame = i->Frame();
    nsIContent* content = frame->GetContent();
    if (content) {
      bool atStart = (content == aRange->GetStartContainer());
      bool atEnd = (content == aRange->GetEndContainer());
      if ((atStart || atEnd) && frame->IsTextFrame()) {
        int32_t frameStartOffset, frameEndOffset;
        frame->GetOffsets(frameStartOffset, frameEndOffset);

        int32_t hilightStart =
            atStart ? std::max(static_cast<int32_t>(aRange->StartOffset()),
                               frameStartOffset)
                    : frameStartOffset;
        int32_t hilightEnd =
            atEnd ? std::min(static_cast<int32_t>(aRange->EndOffset()),
                             frameEndOffset)
                  : frameEndOffset;
        if (hilightStart < hilightEnd) {
          // determine the location of the start and end edges of the range.
          nsPoint startPoint, endPoint;
          frame->GetPointFromOffset(hilightStart, &startPoint);
          frame->GetPointFromOffset(hilightEnd, &endPoint);

          // The clip rectangle is determined by taking the the start and
          // end points of the range, offset from the reference frame.
          // Because of rtl, the end point may be to the left of (or above,
          // in vertical mode) the start point, so x (or y) is set to the
          // lower of the values.
          nsRect textRect(aBuilder->ToReferenceFrame(frame), frame->GetSize());
          if (frame->GetWritingMode().IsVertical()) {
            nscoord y = std::min(startPoint.y, endPoint.y);
            textRect.y += y;
            textRect.height = std::max(startPoint.y, endPoint.y) - y;
          } else {
            nscoord x = std::min(startPoint.x, endPoint.x);
            textRect.x += x;
            textRect.width = std::max(startPoint.x, endPoint.x) - x;
          }
          surfaceRect.UnionRect(surfaceRect, textRect);

          const ActiveScrolledRoot* asr = i->GetActiveScrolledRoot();

          DisplayItemClip newClip;
          newClip.SetTo(textRect);

          const DisplayItemClipChain* newClipChain =
              aBuilder->AllocateDisplayItemClipChain(newClip, asr, nullptr);

          i->IntersectClip(aBuilder, newClipChain, true);
          itemToInsert = i;
        }
      }
      // Don't try to descend into subdocuments.
      // If this ever changes we'd need to add handling for subdocuments with
      // different zoom levels.
      else if (content->GetUncomposedDoc() ==
               aRange->GetStartContainer()->GetUncomposedDoc()) {
        // if the node is within the range, append it to the temporary list
        bool before, after;
        nsresult rv =
            nsRange::CompareNodeToRange(content, aRange, &before, &after);
        if (NS_SUCCEEDED(rv) && !before && !after) {
          itemToInsert = i;
          bool snap;
          surfaceRect.UnionRect(surfaceRect, i->GetBounds(aBuilder, &snap));
        }
      }
    }

    // insert the item into the list if necessary. If the item has a child
    // list, insert that as well
    nsDisplayList* sublist = i->GetSameCoordinateSystemChildren();
    if (itemToInsert || sublist) {
      tmpList.AppendToTop(itemToInsert ? itemToInsert : i);
      // if the item is a list, iterate over it as well
      if (sublist)
        surfaceRect.UnionRect(surfaceRect,
                              ClipListToRange(aBuilder, sublist, aRange));
    } else {
      // otherwise, just delete the item and don't readd it to the list
      i->Destroy(aBuilder);
    }
  }

  // now add all the items back onto the original list again
  aList->AppendToTop(&tmpList);

  return surfaceRect;
}

#ifdef DEBUG
#include <stdio.h>

static bool gDumpRangePaintList = false;
#endif

UniquePtr<RangePaintInfo> PresShell::CreateRangePaintInfo(
    nsRange* aRange, nsRect& aSurfaceRect, bool aForPrimarySelection) {
  nsIFrame* ancestorFrame;
  nsIFrame* rootFrame = GetRootFrame();

  // If the start or end of the range is the document, just use the root
  // frame, otherwise get the common ancestor of the two endpoints of the
  // range.
  nsINode* startContainer = aRange->GetStartContainer();
  nsINode* endContainer = aRange->GetEndContainer();
  Document* doc = startContainer->GetComposedDoc();
  if (startContainer == doc || endContainer == doc) {
    ancestorFrame = rootFrame;
  } else {
    nsINode* ancestor =
        nsContentUtils::GetCommonAncestor(startContainer, endContainer);
    NS_ASSERTION(!ancestor || ancestor->IsContent(),
                 "common ancestor is not content");
    if (!ancestor || !ancestor->IsContent()) return nullptr;

    ancestorFrame = ancestor->AsContent()->GetPrimaryFrame();

    // XXX deal with ancestorFrame being null due to display:contents

    // use the nearest ancestor frame that includes all continuations as the
    // root for building the display list
    while (ancestorFrame &&
           nsLayoutUtils::GetNextContinuationOrIBSplitSibling(ancestorFrame))
      ancestorFrame = ancestorFrame->GetParent();
  }

  if (!ancestorFrame) {
    return nullptr;
  }

  // get a display list containing the range
  auto info = MakeUnique<RangePaintInfo>(aRange, ancestorFrame);
  info->mBuilder.SetIncludeAllOutOfFlows();
  if (aForPrimarySelection) {
    info->mBuilder.SetSelectedFramesOnly();
  }
  info->mBuilder.EnterPresShell(ancestorFrame);

  ContentSubtreeIterator subtreeIter;
  nsresult rv = subtreeIter.Init(aRange);
  if (NS_FAILED(rv)) {
    return nullptr;
  }

  auto BuildDisplayListForNode = [&](nsINode* aNode) {
    if (MOZ_UNLIKELY(!aNode->IsContent())) {
      return;
    }
    nsIFrame* frame = aNode->AsContent()->GetPrimaryFrame();
    // XXX deal with frame being null due to display:contents
    for (; frame;
         frame = nsLayoutUtils::GetNextContinuationOrIBSplitSibling(frame)) {
      info->mBuilder.SetVisibleRect(frame->GetVisualOverflowRect());
      info->mBuilder.SetDirtyRect(frame->GetVisualOverflowRect());
      frame->BuildDisplayListForStackingContext(&info->mBuilder, &info->mList);
    }
  };
  if (startContainer->NodeType() == nsINode::TEXT_NODE) {
    BuildDisplayListForNode(startContainer);
  }
  for (; !subtreeIter.IsDone(); subtreeIter.Next()) {
    nsCOMPtr<nsINode> node = subtreeIter.GetCurrentNode();
    BuildDisplayListForNode(node);
  }
  if (endContainer != startContainer &&
      endContainer->NodeType() == nsINode::TEXT_NODE) {
    BuildDisplayListForNode(endContainer);
  }

#ifdef DEBUG
  if (gDumpRangePaintList) {
    fprintf(stderr, "CreateRangePaintInfo --- before ClipListToRange:\n");
    nsFrame::PrintDisplayList(&(info->mBuilder), info->mList);
  }
#endif

  nsRect rangeRect = ClipListToRange(&info->mBuilder, &info->mList, aRange);

  info->mBuilder.LeavePresShell(ancestorFrame, &info->mList);

#ifdef DEBUG
  if (gDumpRangePaintList) {
    fprintf(stderr, "CreateRangePaintInfo --- after ClipListToRange:\n");
    nsFrame::PrintDisplayList(&(info->mBuilder), info->mList);
  }
#endif

  // determine the offset of the reference frame for the display list
  // to the root frame. This will allow the coordinates used when painting
  // to all be offset from the same point
  info->mRootOffset = ancestorFrame->GetOffsetTo(rootFrame);
  rangeRect.MoveBy(info->mRootOffset);
  aSurfaceRect.UnionRect(aSurfaceRect, rangeRect);

  return info;
}

already_AddRefed<SourceSurface> PresShell::PaintRangePaintInfo(
    const nsTArray<UniquePtr<RangePaintInfo>>& aItems, Selection* aSelection,
    const Maybe<CSSIntRegion>& aRegion, nsRect aArea,
    const LayoutDeviceIntPoint aPoint, LayoutDeviceIntRect* aScreenRect,
    uint32_t aFlags) {
  nsPresContext* pc = GetPresContext();
  if (!pc || aArea.width == 0 || aArea.height == 0) return nullptr;

  // use the rectangle to create the surface
  nsIntRect pixelArea = aArea.ToOutsidePixels(pc->AppUnitsPerDevPixel());

  // if the image should not be resized, scale must be 1
  float scale = 1.0;
  nsIntRect rootScreenRect =
      GetRootFrame()->GetScreenRectInAppUnits().ToNearestPixels(
          pc->AppUnitsPerDevPixel());

  nsRect maxSize;
  pc->DeviceContext()->GetClientRect(maxSize);

  // check if the image should be resized
  bool resize = aFlags & RENDER_AUTO_SCALE;

  if (resize) {
    // check if image-resizing-algorithm should be used
    if (aFlags & RENDER_IS_IMAGE) {
      // get max screensize
      nscoord maxWidth = pc->AppUnitsToDevPixels(maxSize.width);
      nscoord maxHeight = pc->AppUnitsToDevPixels(maxSize.height);
      // resize image relative to the screensize
      // get best height/width relative to screensize
      float bestHeight = float(maxHeight) * RELATIVE_SCALEFACTOR;
      float bestWidth = float(maxWidth) * RELATIVE_SCALEFACTOR;
      // calculate scale for bestWidth
      float adjustedScale = bestWidth / float(pixelArea.width);
      // get the worst height (height when width is perfect)
      float worstHeight = float(pixelArea.height) * adjustedScale;
      // get the difference of best and worst height
      float difference = bestHeight - worstHeight;
      // halve the difference and add it to worstHeight to get
      // the best compromise between bestHeight and bestWidth,
      // then calculate the corresponding scale factor
      adjustedScale = (worstHeight + difference / 2) / float(pixelArea.height);
      // prevent upscaling
      scale = std::min(scale, adjustedScale);
    } else {
      // get half of max screensize
      nscoord maxWidth = pc->AppUnitsToDevPixels(maxSize.width >> 1);
      nscoord maxHeight = pc->AppUnitsToDevPixels(maxSize.height >> 1);
      if (pixelArea.width > maxWidth || pixelArea.height > maxHeight) {
        // divide the maximum size by the image size in both directions.
        // Whichever direction produces the smallest result determines how much
        // should be scaled.
        if (pixelArea.width > maxWidth)
          scale = std::min(scale, float(maxWidth) / pixelArea.width);
        if (pixelArea.height > maxHeight)
          scale = std::min(scale, float(maxHeight) / pixelArea.height);
      }
    }

    pixelArea.width = NSToIntFloor(float(pixelArea.width) * scale);
    pixelArea.height = NSToIntFloor(float(pixelArea.height) * scale);
    if (!pixelArea.width || !pixelArea.height) return nullptr;

    // adjust the screen position based on the rescaled size
    nscoord left = rootScreenRect.x + pixelArea.x;
    nscoord top = rootScreenRect.y + pixelArea.y;
    aScreenRect->x = NSToIntFloor(aPoint.x - float(aPoint.x - left) * scale);
    aScreenRect->y = NSToIntFloor(aPoint.y - float(aPoint.y - top) * scale);
  } else {
    // move aScreenRect to the position of the surface in screen coordinates
    aScreenRect->MoveTo(rootScreenRect.x + pixelArea.x,
                        rootScreenRect.y + pixelArea.y);
  }
  aScreenRect->width = pixelArea.width;
  aScreenRect->height = pixelArea.height;

  RefPtr<DrawTarget> dt =
      gfxPlatform::GetPlatform()->CreateOffscreenContentDrawTarget(
          IntSize(pixelArea.width, pixelArea.height), SurfaceFormat::B8G8R8A8);
  if (!dt || !dt->IsValid()) {
    return nullptr;
  }

  RefPtr<gfxContext> ctx = gfxContext::CreateOrNull(dt);
  MOZ_ASSERT(ctx);  // already checked the draw target above

  if (aRegion) {
    RefPtr<PathBuilder> builder = dt->CreatePathBuilder(FillRule::FILL_WINDING);

    // Convert aRegion from CSS pixels to dev pixels
    nsIntRegion region = aRegion->ToAppUnits(AppUnitsPerCSSPixel())
                             .ToOutsidePixels(pc->AppUnitsPerDevPixel());
    for (auto iter = region.RectIter(); !iter.Done(); iter.Next()) {
      const IntRect& rect = iter.Get();

      builder->MoveTo(rect.TopLeft());
      builder->LineTo(rect.TopRight());
      builder->LineTo(rect.BottomRight());
      builder->LineTo(rect.BottomLeft());
      builder->LineTo(rect.TopLeft());
    }

    RefPtr<Path> path = builder->Finish();
    ctx->Clip(path);
  }

  gfxMatrix initialTM = ctx->CurrentMatrixDouble();

  if (resize) initialTM.PreScale(scale, scale);

  // translate so that points are relative to the surface area
  gfxPoint surfaceOffset = nsLayoutUtils::PointToGfxPoint(
      -aArea.TopLeft(), pc->AppUnitsPerDevPixel());
  initialTM.PreTranslate(surfaceOffset);

  // temporarily hide the selection so that text is drawn normally. If a
  // selection is being rendered, use that, otherwise use the presshell's
  // selection.
  RefPtr<nsFrameSelection> frameSelection;
  if (aSelection) {
    frameSelection = aSelection->GetFrameSelection();
  } else {
    frameSelection = FrameSelection();
  }
  int16_t oldDisplaySelection = frameSelection->GetDisplaySelection();
  frameSelection->SetDisplaySelection(nsISelectionController::SELECTION_HIDDEN);

  // next, paint each range in the selection
  for (const UniquePtr<RangePaintInfo>& rangeInfo : aItems) {
    // the display lists paint relative to the offset from the reference
    // frame, so account for that translation too:
    gfxPoint rootOffset = nsLayoutUtils::PointToGfxPoint(
        rangeInfo->mRootOffset, pc->AppUnitsPerDevPixel());
    ctx->SetMatrixDouble(initialTM.PreTranslate(rootOffset));
    aArea.MoveBy(-rangeInfo->mRootOffset.x, -rangeInfo->mRootOffset.y);
    nsRegion visible(aArea);
    RefPtr<LayerManager> layerManager = rangeInfo->mList.PaintRoot(
        &rangeInfo->mBuilder, ctx, nsDisplayList::PAINT_DEFAULT);
    aArea.MoveBy(rangeInfo->mRootOffset.x, rangeInfo->mRootOffset.y);
  }

  // restore the old selection display state
  frameSelection->SetDisplaySelection(oldDisplaySelection);

  return dt->Snapshot();
}

already_AddRefed<SourceSurface> PresShell::RenderNode(
    nsINode* aNode, const Maybe<CSSIntRegion>& aRegion,
    const LayoutDeviceIntPoint aPoint, LayoutDeviceIntRect* aScreenRect,
    uint32_t aFlags) {
  // area will hold the size of the surface needed to draw the node, measured
  // from the root frame.
  nsRect area;
  nsTArray<UniquePtr<RangePaintInfo>> rangeItems;

  // nothing to draw if the node isn't in a document
  if (!aNode->IsInComposedDoc()) {
    return nullptr;
  }

  RefPtr<nsRange> range = new nsRange(aNode);
  IgnoredErrorResult rv;
  range->SelectNode(*aNode, rv);
  if (rv.Failed()) {
    return nullptr;
  }

  UniquePtr<RangePaintInfo> info = CreateRangePaintInfo(range, area, false);
  if (info && !rangeItems.AppendElement(std::move(info))) {
    return nullptr;
  }

  Maybe<CSSIntRegion> region = aRegion;
  if (region) {
    // combine the area with the supplied region
    CSSIntRect rrectPixels = region->GetBounds();

    nsRect rrect = ToAppUnits(rrectPixels, AppUnitsPerCSSPixel());
    area.IntersectRect(area, rrect);

    nsPresContext* pc = GetPresContext();
    if (!pc) return nullptr;

    // move the region so that it is offset from the topleft corner of the
    // surface
    region->MoveBy(-nsPresContext::AppUnitsToIntCSSPixels(area.x),
                   -nsPresContext::AppUnitsToIntCSSPixels(area.y));
  }

  return PaintRangePaintInfo(rangeItems, nullptr, region, area, aPoint,
                             aScreenRect, aFlags);
}

already_AddRefed<SourceSurface> PresShell::RenderSelection(
    Selection* aSelection, const LayoutDeviceIntPoint aPoint,
    LayoutDeviceIntRect* aScreenRect, uint32_t aFlags) {
  // area will hold the size of the surface needed to draw the selection,
  // measured from the root frame.
  nsRect area;
  nsTArray<UniquePtr<RangePaintInfo>> rangeItems;

  // iterate over each range and collect them into the rangeItems array.
  // This is done so that the size of selection can be determined so as
  // to allocate a surface area
  uint32_t numRanges = aSelection->RangeCount();
  NS_ASSERTION(numRanges > 0, "RenderSelection called with no selection");

  for (uint32_t r = 0; r < numRanges; r++) {
    RefPtr<nsRange> range = aSelection->GetRangeAt(r);

    UniquePtr<RangePaintInfo> info = CreateRangePaintInfo(range, area, true);
    if (info && !rangeItems.AppendElement(std::move(info))) {
      return nullptr;
    }
  }

  return PaintRangePaintInfo(rangeItems, aSelection, Nothing(), area, aPoint,
                             aScreenRect, aFlags);
}

void PresShell::AddPrintPreviewBackgroundItem(nsDisplayListBuilder& aBuilder,
                                              nsDisplayList& aList,
                                              nsIFrame* aFrame,
                                              const nsRect& aBounds) {
  aList.AppendToBottom(MakeDisplayItem<nsDisplaySolidColor>(
      &aBuilder, aFrame, aBounds, NS_RGB(115, 115, 115)));
}

static bool AddCanvasBackgroundColor(const nsDisplayList& aList,
                                     nsIFrame* aCanvasFrame, nscolor aColor,
                                     bool aCSSBackgroundColor) {
  for (nsDisplayItem* i = aList.GetBottom(); i; i = i->GetAbove()) {
    const DisplayItemType type = i->GetType();

    if (i->Frame() == aCanvasFrame &&
        type == DisplayItemType::TYPE_CANVAS_BACKGROUND_COLOR) {
      nsDisplayCanvasBackgroundColor* bg =
          static_cast<nsDisplayCanvasBackgroundColor*>(i);
      bg->SetExtraBackgroundColor(aColor);
      return true;
    }

    const bool isBlendContainer =
        type == DisplayItemType::TYPE_BLEND_CONTAINER ||
        type == DisplayItemType::TYPE_TABLE_BLEND_CONTAINER;

    nsDisplayList* sublist = i->GetSameCoordinateSystemChildren();
    if (sublist && !(isBlendContainer && !aCSSBackgroundColor) &&
        AddCanvasBackgroundColor(*sublist, aCanvasFrame, aColor,
                                 aCSSBackgroundColor))
      return true;
  }
  return false;
}

void PresShell::AddCanvasBackgroundColorItem(
    nsDisplayListBuilder& aBuilder, nsDisplayList& aList, nsIFrame* aFrame,
    const nsRect& aBounds, nscolor aBackstopColor, uint32_t aFlags) {
  if (aBounds.IsEmpty()) {
    return;
  }
  // We don't want to add an item for the canvas background color if the frame
  // (sub)tree we are painting doesn't include any canvas frames. There isn't
  // an easy way to check this directly, but if we check if the root of the
  // (sub)tree we are painting is a canvas frame that should cover us in all
  // cases (it will usually be a viewport frame when we have a canvas frame in
  // the (sub)tree).
  if (!(aFlags & nsIPresShell::FORCE_DRAW) &&
      !nsCSSRendering::IsCanvasFrame(aFrame)) {
    return;
  }

  nscolor bgcolor = NS_ComposeColors(aBackstopColor, mCanvasBackgroundColor);
  if (NS_GET_A(bgcolor) == 0) return;

  // To make layers work better, we want to avoid having a big non-scrolled
  // color background behind a scrolled transparent background. Instead,
  // we'll try to move the color background into the scrolled content
  // by making nsDisplayCanvasBackground paint it.
  // If we're only adding an unscrolled item, then pretend that we've
  // already done it.
  bool addedScrollingBackgroundColor = (aFlags & APPEND_UNSCROLLED_ONLY);
  if (!aFrame->GetParent() && !addedScrollingBackgroundColor) {
    nsIScrollableFrame* sf =
        aFrame->PresShell()->GetRootScrollFrameAsScrollable();
    if (sf) {
      nsCanvasFrame* canvasFrame = do_QueryFrame(sf->GetScrolledFrame());
      if (canvasFrame && canvasFrame->IsVisibleForPainting()) {
        addedScrollingBackgroundColor = AddCanvasBackgroundColor(
            aList, canvasFrame, bgcolor, mHasCSSBackgroundColor);
      }
    }
  }

  // With async scrolling, we'd like to have two instances of the background
  // color: one that scrolls with the content (for the reasons stated above),
  // and one underneath which does not scroll with the content, but which can
  // be shown during checkerboarding and overscroll.
  // We can only do that if the color is opaque.
  bool forceUnscrolledItem =
      nsLayoutUtils::UsesAsyncScrolling(aFrame) && NS_GET_A(bgcolor) == 255;
  if ((aFlags & ADD_FOR_SUBDOC) &&
      gfxPrefs::LayoutUseContainersForRootFrames()) {
    // If we're using ContainerLayers for a subdoc, then any items we add here
    // will still be scrolled (since we're inside the container at this point),
    // so don't bother and we will do it manually later.
    forceUnscrolledItem = false;
  }

  if (!addedScrollingBackgroundColor || forceUnscrolledItem) {
    aList.AppendToBottom(MakeDisplayItem<nsDisplaySolidColor>(
        &aBuilder, aFrame, aBounds, bgcolor));
  }
}

static bool IsTransparentContainerElement(nsPresContext* aPresContext) {
  nsCOMPtr<nsIDocShell> docShell = aPresContext->GetDocShell();
  if (!docShell) {
    return false;
  }

  nsCOMPtr<nsPIDOMWindowOuter> pwin = docShell->GetWindow();
  if (!pwin) return false;
  nsCOMPtr<Element> containerElement = pwin->GetFrameElementInternal();

  TabChild* tab = TabChild::GetFrom(docShell);
  if (tab) {
    // Check if presShell is the top PresShell. Only the top can
    // influence the canvas background color.
    nsCOMPtr<nsIPresShell> presShell = aPresContext->GetPresShell();
    nsCOMPtr<nsIPresShell> topPresShell = tab->GetPresShell();
    if (presShell != topPresShell) {
      tab = nullptr;
    }
  }

  return (containerElement && containerElement->HasAttr(
                                  kNameSpaceID_None, nsGkAtoms::transparent)) ||
         (tab && tab->IsTransparent());
}

nscolor PresShell::GetDefaultBackgroundColorToDraw() {
  if (!mPresContext || !mPresContext->GetBackgroundColorDraw()) {
    return NS_RGB(255, 255, 255);
  }
  return mPresContext->DefaultBackgroundColor();
}

void PresShell::UpdateCanvasBackground() {
  // If we have a frame tree and it has style information that
  // specifies the background color of the canvas, update our local
  // cache of that color.
  nsIFrame* rootStyleFrame = FrameConstructor()->GetRootElementStyleFrame();
  if (rootStyleFrame) {
    ComputedStyle* bgStyle =
        nsCSSRendering::FindRootFrameBackground(rootStyleFrame);
    // XXX We should really be passing the canvasframe, not the root element
    // style frame but we don't have access to the canvasframe here. It isn't
    // a problem because only a few frames can return something other than true
    // and none of them would be a canvas frame or root element style frame.
    bool drawBackgroundImage;
    bool drawBackgroundColor;
    mCanvasBackgroundColor = nsCSSRendering::DetermineBackgroundColor(
        mPresContext, bgStyle, rootStyleFrame, drawBackgroundImage,
        drawBackgroundColor);
    mHasCSSBackgroundColor = drawBackgroundColor;
    if (mPresContext->IsRootContentDocument() &&
        !IsTransparentContainerElement(mPresContext)) {
      mCanvasBackgroundColor = NS_ComposeColors(
          GetDefaultBackgroundColorToDraw(), mCanvasBackgroundColor);
    }
  }

  // If the root element of the document (ie html) has style 'display: none'
  // then the document's background color does not get drawn; cache the
  // color we actually draw.
  if (!FrameConstructor()->GetRootElementFrame()) {
    mCanvasBackgroundColor = GetDefaultBackgroundColorToDraw();
  }
}

nscolor PresShell::ComputeBackstopColor(nsView* aDisplayRoot) {
  nsIWidget* widget = aDisplayRoot->GetWidget();
  if (widget && (widget->GetTransparencyMode() != eTransparencyOpaque ||
                 widget->WidgetPaintsBackground())) {
    // Within a transparent widget, so the backstop color must be
    // totally transparent.
    return NS_RGBA(0, 0, 0, 0);
  }
  // Within an opaque widget (or no widget at all), so the backstop
  // color must be totally opaque. The user's default background
  // as reported by the prescontext is guaranteed to be opaque.
  return GetDefaultBackgroundColorToDraw();
}

struct PaintParams {
  nscolor mBackgroundColor;
};

LayerManager* PresShell::GetLayerManager() {
  NS_ASSERTION(mViewManager, "Should have view manager");

  nsView* rootView = mViewManager->GetRootView();
  if (rootView) {
    if (nsIWidget* widget = rootView->GetWidget()) {
      return widget->GetLayerManager();
    }
  }
  return nullptr;
}

bool PresShell::AsyncPanZoomEnabled() {
  NS_ASSERTION(mViewManager, "Should have view manager");
  nsView* rootView = mViewManager->GetRootView();
  if (rootView) {
    if (nsIWidget* widget = rootView->GetWidget()) {
      return widget->AsyncPanZoomEnabled();
    }
  }
  return gfxPlatform::AsyncPanZoomEnabled();
}

void PresShell::SetIgnoreViewportScrolling(bool aIgnore) {
  if (IgnoringViewportScrolling() == aIgnore) {
    return;
  }
  RenderingState state(this);
  state.mRenderFlags = ChangeFlag(state.mRenderFlags, aIgnore,
                                  STATE_IGNORING_VIEWPORT_SCROLLING);
  SetRenderingState(state);
}

nsresult PresShell::SetResolutionAndScaleTo(float aResolution,
                                            ChangeOrigin aOrigin) {
  if (!(aResolution > 0.0)) {
    return NS_ERROR_ILLEGAL_VALUE;
  }
  if (aResolution == mResolution.valueOr(0.0)) {
    MOZ_ASSERT(mResolution.isSome());
    return NS_OK;
  }
  RenderingState state(this);
  state.mResolution = Some(aResolution);
  SetRenderingState(state);
  if (mMobileViewportManager) {
    mMobileViewportManager->ResolutionUpdated();
  }
  if (aOrigin != ChangeOrigin::eApz) {
    mResolutionUpdated = true;
  }
  if (auto* window = nsGlobalWindowInner::Cast(mDocument->GetInnerWindow())) {
    window->VisualViewport()->PostResizeEvent();
  }

  return NS_OK;
}

float PresShell::GetCumulativeResolution() {
  float resolution = GetResolution();
  nsPresContext* parentCtx = GetPresContext()->GetParentPresContext();
  if (parentCtx) {
    resolution *= parentCtx->PresShell()->GetCumulativeResolution();
  }
  return resolution;
}

float PresShell::GetCumulativeNonRootScaleResolution() {
  float resolution = 1.0;
  nsIPresShell* currentShell = this;
  while (currentShell) {
    nsPresContext* currentCtx = currentShell->GetPresContext();
    if (currentCtx != currentCtx->GetRootPresContext()) {
      resolution *= currentShell->GetResolution();
    }
    nsPresContext* parentCtx = currentCtx->GetParentPresContext();
    if (parentCtx) {
      currentShell = parentCtx->PresShell();
    } else {
      currentShell = nullptr;
    }
  }
  return resolution;
}

void PresShell::SetRestoreResolution(float aResolution,
                                     LayoutDeviceIntSize aDisplaySize) {
  if (mMobileViewportManager) {
    mMobileViewportManager->SetRestoreResolution(aResolution, aDisplaySize);
  }
}

void PresShell::SetRenderingState(const RenderingState& aState) {
  if (mRenderFlags != aState.mRenderFlags) {
    // Rendering state changed in a way that forces us to flush any
    // retained layers we might already have.
    LayerManager* manager = GetLayerManager();
    if (manager) {
      FrameLayerBuilder::InvalidateAllLayers(manager);
    }
  }

  mRenderFlags = aState.mRenderFlags;
  mResolution = aState.mResolution;
}

void PresShell::SynthesizeMouseMove(bool aFromScroll) {
  if (!sSynthMouseMove) return;

  if (mPaintingSuppressed || !mIsActive || !mPresContext) {
    return;
  }

  if (!mPresContext->IsRoot()) {
    nsIPresShell* rootPresShell = GetRootPresShell();
    if (rootPresShell) {
      rootPresShell->SynthesizeMouseMove(aFromScroll);
    }
    return;
  }

  if (mMouseLocation == nsPoint(NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE))
    return;

  if (!mSynthMouseMoveEvent.IsPending()) {
    RefPtr<nsSynthMouseMoveEvent> ev =
        new nsSynthMouseMoveEvent(this, aFromScroll);

    GetPresContext()->RefreshDriver()->AddRefreshObserver(ev,
                                                          FlushType::Display);
    mSynthMouseMoveEvent = std::move(ev);
  }
}

/**
 * Find the first floating view with a widget in a postorder traversal of the
 * view tree that contains the point. Thus more deeply nested floating views
 * are preferred over their ancestors, and floating views earlier in the
 * view hierarchy (i.e., added later) are preferred over their siblings.
 * This is adequate for finding the "topmost" floating view under a point,
 * given that floating views don't supporting having a specific z-index.
 *
 * We cannot exit early when aPt is outside the view bounds, because floating
 * views aren't necessarily included in their parent's bounds, so this could
 * traverse the entire view hierarchy --- use carefully.
 */
static nsView* FindFloatingViewContaining(nsView* aView, nsPoint aPt) {
  if (aView->GetVisibility() == nsViewVisibility_kHide)
    // No need to look into descendants.
    return nullptr;

  nsIFrame* frame = aView->GetFrame();
  if (frame) {
    if (!frame->IsVisibleConsideringAncestors(
            nsIFrame::VISIBILITY_CROSS_CHROME_CONTENT_BOUNDARY) ||
        !frame->PresShell()->IsActive()) {
      return nullptr;
    }
  }

  for (nsView* v = aView->GetFirstChild(); v; v = v->GetNextSibling()) {
    nsView* r = FindFloatingViewContaining(v, v->ConvertFromParentCoords(aPt));
    if (r) return r;
  }

  if (aView->GetFloating() && aView->HasWidget() &&
      aView->GetDimensions().Contains(aPt))
    return aView;

  return nullptr;
}

/*
 * This finds the first view containing the given point in a postorder
 * traversal of the view tree that contains the point, assuming that the
 * point is not in a floating view.  It assumes that only floating views
 * extend outside the bounds of their parents.
 *
 * This methods should only be called if FindFloatingViewContaining
 * returns null.
 */
static nsView* FindViewContaining(nsView* aView, nsPoint aPt) {
  if (!aView->GetDimensions().Contains(aPt) ||
      aView->GetVisibility() == nsViewVisibility_kHide) {
    return nullptr;
  }

  nsIFrame* frame = aView->GetFrame();
  if (frame) {
    if (!frame->IsVisibleConsideringAncestors(
            nsIFrame::VISIBILITY_CROSS_CHROME_CONTENT_BOUNDARY) ||
        !frame->PresShell()->IsActive()) {
      return nullptr;
    }
  }

  for (nsView* v = aView->GetFirstChild(); v; v = v->GetNextSibling()) {
    nsView* r = FindViewContaining(v, v->ConvertFromParentCoords(aPt));
    if (r) return r;
  }

  return aView;
}

void PresShell::ProcessSynthMouseMoveEvent(bool aFromScroll) {
  // If drag session has started, we shouldn't synthesize mousemove event.
  nsCOMPtr<nsIDragSession> dragSession = nsContentUtils::GetDragSession();
  if (dragSession) {
    mSynthMouseMoveEvent.Forget();
    return;
  }

  // allow new event to be posted while handling this one only if the
  // source of the event is a scroll (to prevent infinite reflow loops)
  if (aFromScroll) {
    mSynthMouseMoveEvent.Forget();
  }

  nsView* rootView = mViewManager ? mViewManager->GetRootView() : nullptr;
  if (mMouseLocation == nsPoint(NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE) ||
      !rootView || !rootView->HasWidget() || !mPresContext) {
    mSynthMouseMoveEvent.Forget();
    return;
  }

  NS_ASSERTION(mPresContext->IsRoot(), "Only a root pres shell should be here");

  // Hold a ref to ourselves so DispatchEvent won't destroy us (since
  // we need to access members after we call DispatchEvent).
  nsCOMPtr<nsIPresShell> kungFuDeathGrip(this);

#ifdef DEBUG_MOUSE_LOCATION
  printf("[ps=%p]synthesizing mouse move to (%d,%d)\n", this, mMouseLocation.x,
         mMouseLocation.y);
#endif

  int32_t APD = mPresContext->AppUnitsPerDevPixel();

  // We need a widget to put in the event we are going to dispatch so we look
  // for a view that has a widget and the mouse location is over. We first look
  // for floating views, if there isn't one we use the root view. |view| holds
  // that view.
  nsView* view = nullptr;

  // The appunits per devpixel ratio of |view|.
  int32_t viewAPD;

  // mRefPoint will be mMouseLocation relative to the widget of |view|, the
  // widget we will put in the event we dispatch, in viewAPD appunits
  nsPoint refpoint(0, 0);

  // We always dispatch the event to the pres shell that contains the view that
  // the mouse is over. pointVM is the VM of that pres shell.
  nsViewManager* pointVM = nullptr;

  // This could be a bit slow (traverses entire view hierarchy)
  // but it's OK to do it once per synthetic mouse event
  view = FindFloatingViewContaining(rootView, mMouseLocation);
  if (!view) {
    view = rootView;
    nsView* pointView = FindViewContaining(rootView, mMouseLocation);
    // pointView can be null in situations related to mouse capture
    pointVM = (pointView ? pointView : view)->GetViewManager();
    refpoint = mMouseLocation + rootView->ViewToWidgetOffset();
    viewAPD = APD;
  } else {
    pointVM = view->GetViewManager();
    nsIFrame* frame = view->GetFrame();
    NS_ASSERTION(frame, "floating views can't be anonymous");
    viewAPD = frame->PresContext()->AppUnitsPerDevPixel();
    refpoint = mMouseLocation.ScaleToOtherAppUnits(APD, viewAPD);
    refpoint -= view->GetOffsetTo(rootView);
    refpoint += view->ViewToWidgetOffset();
  }
  NS_ASSERTION(view->GetWidget(), "view should have a widget here");
  WidgetMouseEvent event(true, eMouseMove, view->GetWidget(),
                         WidgetMouseEvent::eSynthesized);
  event.mRefPoint =
      LayoutDeviceIntPoint::FromAppUnitsToNearest(refpoint, viewAPD);
  event.mTime = PR_IntervalNow();
  // XXX set event.mModifiers ?
  // XXX mnakano I think that we should get the latest information from widget.

  nsCOMPtr<nsIPresShell> shell = pointVM->GetPresShell();
  if (shell) {
    // Since this gets run in a refresh tick there isn't an InputAPZContext on
    // the stack from the nsBaseWidget. We need to simulate one with at least
    // the correct target guid, so that the correct callback transform gets
    // applied if this event goes to a child process. The input block id is set
    // to 0 because this is a synthetic event which doesn't really belong to any
    // input block. Same for the APZ response field.
    InputAPZContext apzContext(mMouseEventTargetGuid, 0, nsEventStatus_eIgnore);
    shell->DispatchSynthMouseMove(&event);
  }

  if (!aFromScroll) {
    mSynthMouseMoveEvent.Forget();
  }
}

/* static */ void PresShell::MarkFramesInListApproximatelyVisible(
    const nsDisplayList& aList) {
  for (nsDisplayItem* item = aList.GetBottom(); item; item = item->GetAbove()) {
    nsDisplayList* sublist = item->GetChildren();
    if (sublist) {
      MarkFramesInListApproximatelyVisible(*sublist);
      continue;
    }

    nsIFrame* frame = item->Frame();
    MOZ_ASSERT(frame);

    if (!frame->TrackingVisibility()) {
      continue;
    }

    // Use the presshell containing the frame.
    auto* presShell = static_cast<PresShell*>(frame->PresShell());
    MOZ_ASSERT(!presShell->AssumeAllFramesVisible());
    if (presShell->mApproximatelyVisibleFrames.EnsureInserted(frame)) {
      // The frame was added to mApproximatelyVisibleFrames, so increment its
      // visible count.
      frame->IncApproximateVisibleCount();
    }
  }
}

/* static */ void PresShell::DecApproximateVisibleCount(
    VisibleFrames& aFrames, const Maybe<OnNonvisible>& aNonvisibleAction
    /* = Nothing() */) {
  for (auto iter = aFrames.Iter(); !iter.Done(); iter.Next()) {
    nsIFrame* frame = iter.Get()->GetKey();
    // Decrement the frame's visible count if we're still tracking its
    // visibility. (We may not be, if the frame disabled visibility tracking
    // after we added it to the visible frames list.)
    if (frame->TrackingVisibility()) {
      frame->DecApproximateVisibleCount(aNonvisibleAction);
    }
  }
}

void PresShell::RebuildApproximateFrameVisibilityDisplayList(
    const nsDisplayList& aList) {
  MOZ_ASSERT(!mApproximateFrameVisibilityVisited, "already visited?");
  mApproximateFrameVisibilityVisited = true;

  // Remove the entries of the mApproximatelyVisibleFrames hashtable and put
  // them in oldApproxVisibleFrames.
  VisibleFrames oldApproximatelyVisibleFrames;
  mApproximatelyVisibleFrames.SwapElements(oldApproximatelyVisibleFrames);

  MarkFramesInListApproximatelyVisible(aList);

  DecApproximateVisibleCount(oldApproximatelyVisibleFrames);
}

/* static */ void PresShell::ClearApproximateFrameVisibilityVisited(
    nsView* aView, bool aClear) {
  nsViewManager* vm = aView->GetViewManager();
  if (aClear) {
    PresShell* presShell = static_cast<PresShell*>(vm->GetPresShell());
    if (!presShell->mApproximateFrameVisibilityVisited) {
      presShell->ClearApproximatelyVisibleFramesList();
    }
    presShell->mApproximateFrameVisibilityVisited = false;
  }
  for (nsView* v = aView->GetFirstChild(); v; v = v->GetNextSibling()) {
    ClearApproximateFrameVisibilityVisited(v, v->GetViewManager() != vm);
  }
}

void PresShell::ClearApproximatelyVisibleFramesList(
    const Maybe<OnNonvisible>& aNonvisibleAction
    /* = Nothing() */) {
  DecApproximateVisibleCount(mApproximatelyVisibleFrames, aNonvisibleAction);
  mApproximatelyVisibleFrames.Clear();
}

void PresShell::MarkFramesInSubtreeApproximatelyVisible(
    nsIFrame* aFrame, const nsRect& aRect, bool aRemoveOnly /* = false */) {
  MOZ_ASSERT(aFrame->PresShell() == this, "wrong presshell");

  if (aFrame->TrackingVisibility() && aFrame->StyleVisibility()->IsVisible() &&
      (!aRemoveOnly ||
       aFrame->GetVisibility() == Visibility::APPROXIMATELY_VISIBLE)) {
    MOZ_ASSERT(!AssumeAllFramesVisible());
    if (mApproximatelyVisibleFrames.EnsureInserted(aFrame)) {
      // The frame was added to mApproximatelyVisibleFrames, so increment its
      // visible count.
      aFrame->IncApproximateVisibleCount();
    }
  }

  nsSubDocumentFrame* subdocFrame = do_QueryFrame(aFrame);
  if (subdocFrame) {
    nsIPresShell* presShell = subdocFrame->GetSubdocumentPresShellForPainting(
        nsSubDocumentFrame::IGNORE_PAINT_SUPPRESSION);
    if (presShell && !presShell->AssumeAllFramesVisible()) {
      nsRect rect = aRect;
      nsIFrame* root = presShell->GetRootFrame();
      if (root) {
        rect.MoveBy(aFrame->GetOffsetToCrossDoc(root));
      } else {
        rect.MoveBy(-aFrame->GetContentRectRelativeToSelf().TopLeft());
      }
      rect = rect.ScaleToOtherAppUnitsRoundOut(
          aFrame->PresContext()->AppUnitsPerDevPixel(),
          presShell->GetPresContext()->AppUnitsPerDevPixel());

      presShell->RebuildApproximateFrameVisibility(&rect);
    }
    return;
  }

  nsRect rect = aRect;

  nsIScrollableFrame* scrollFrame = do_QueryFrame(aFrame);
  if (scrollFrame) {
    bool ignoreDisplayPort = false;
    if (nsLayoutUtils::IsMissingDisplayPortBaseRect(aFrame->GetContent())) {
      // We can properly set the base rect for root scroll frames on top level
      // and root content documents. Otherwise the base rect we compute might
      // be way too big without the limiting that
      // ScrollFrameHelper::DecideScrollableLayer does, so we just ignore the
      // displayport in that case.
      nsPresContext* pc = aFrame->PresContext();
      if (scrollFrame->IsRootScrollFrameOfDocument() &&
          (pc->IsRootContentDocument() || !pc->GetParentPresContext())) {
        nsRect baseRect =
            nsRect(nsPoint(0, 0),
                   nsLayoutUtils::CalculateCompositionSizeForFrame(aFrame));
        nsLayoutUtils::SetDisplayPortBase(aFrame->GetContent(), baseRect);
      } else {
        ignoreDisplayPort = true;
      }
    }

    nsRect displayPort;
    bool usingDisplayport =
        !ignoreDisplayPort &&
        nsLayoutUtils::GetDisplayPortForVisibilityTesting(
            aFrame->GetContent(), &displayPort, RelativeTo::ScrollFrame);

    scrollFrame->NotifyApproximateFrameVisibilityUpdate(!usingDisplayport);

    if (usingDisplayport) {
      rect = displayPort;
    } else {
      rect = rect.Intersect(scrollFrame->GetScrollPortRect());
    }
    rect = scrollFrame->ExpandRectToNearlyVisible(rect);
  }

  bool preserves3DChildren = aFrame->Extend3DContext();

  // We assume all frames in popups are visible, so we skip them here.
  const nsIFrame::ChildListIDs skip = {nsIFrame::kPopupList,
                                       nsIFrame::kSelectPopupList};
  for (nsIFrame::ChildListIterator childLists(aFrame); !childLists.IsDone();
       childLists.Next()) {
    if (skip.contains(childLists.CurrentID())) {
      continue;
    }

    for (nsIFrame* child : childLists.CurrentList()) {
      nsRect r = rect - child->GetPosition();
      if (!r.IntersectRect(r, child->GetVisualOverflowRect())) {
        continue;
      }
      if (child->IsTransformed()) {
        // for children of a preserve3d element we just pass down the same dirty
        // rect
        if (!preserves3DChildren ||
            !child->Combines3DTransformWithAncestors()) {
          const nsRect overflow = child->GetVisualOverflowRectRelativeToSelf();
          nsRect out;
          if (nsDisplayTransform::UntransformRect(r, overflow, child, &out)) {
            r = out;
          } else {
            r.SetEmpty();
          }
        }
      }
      MarkFramesInSubtreeApproximatelyVisible(child, r);
    }
  }
}

void PresShell::RebuildApproximateFrameVisibility(
    nsRect* aRect, bool aRemoveOnly /* = false */) {
  MOZ_ASSERT(!mApproximateFrameVisibilityVisited, "already visited?");
  mApproximateFrameVisibilityVisited = true;

  nsIFrame* rootFrame = GetRootFrame();
  if (!rootFrame) {
    return;
  }

  // Remove the entries of the mApproximatelyVisibleFrames hashtable and put
  // them in oldApproximatelyVisibleFrames.
  VisibleFrames oldApproximatelyVisibleFrames;
  mApproximatelyVisibleFrames.SwapElements(oldApproximatelyVisibleFrames);

  nsRect vis(nsPoint(0, 0), rootFrame->GetSize());
  if (aRect) {
    vis = *aRect;
  }

  MarkFramesInSubtreeApproximatelyVisible(rootFrame, vis, aRemoveOnly);

  DecApproximateVisibleCount(oldApproximatelyVisibleFrames);
}

void PresShell::UpdateApproximateFrameVisibility() {
  DoUpdateApproximateFrameVisibility(/* aRemoveOnly = */ false);
}

void PresShell::DoUpdateApproximateFrameVisibility(bool aRemoveOnly) {
  MOZ_ASSERT(
      !mPresContext || mPresContext->IsRootContentDocument(),
      "Updating approximate frame visibility on a non-root content document?");

  mUpdateApproximateFrameVisibilityEvent.Revoke();

  if (mHaveShutDown || mIsDestroying) {
    return;
  }

  // call update on that frame
  nsIFrame* rootFrame = GetRootFrame();
  if (!rootFrame) {
    ClearApproximatelyVisibleFramesList(Some(OnNonvisible::DISCARD_IMAGES));
    return;
  }

  RebuildApproximateFrameVisibility(/* aRect = */ nullptr, aRemoveOnly);
  ClearApproximateFrameVisibilityVisited(rootFrame->GetView(), true);

#ifdef DEBUG_FRAME_VISIBILITY_DISPLAY_LIST
  // This can be used to debug the frame walker by comparing beforeFrameList
  // and mApproximatelyVisibleFrames in RebuildFrameVisibilityDisplayList to see
  // if they produce the same results (mApproximatelyVisibleFrames holds the
  // frames the display list thinks are visible, beforeFrameList holds the
  // frames the frame walker thinks are visible).
  nsDisplayListBuilder builder(
      rootFrame, nsDisplayListBuilderMode::FRAME_VISIBILITY, false);
  nsRect updateRect(nsPoint(0, 0), rootFrame->GetSize());
  nsIFrame* rootScroll = GetRootScrollFrame();
  if (rootScroll) {
    nsIContent* content = rootScroll->GetContent();
    if (content) {
      Unused << nsLayoutUtils::GetDisplayPortForVisibilityTesting(
          content, &updateRect, RelativeTo::ScrollFrame);
    }

    if (IgnoringViewportScrolling()) {
      builder.SetIgnoreScrollFrame(rootScroll);
    }
  }
  builder.IgnorePaintSuppression();
  builder.EnterPresShell(rootFrame);
  nsDisplayList list;
  rootFrame->BuildDisplayListForStackingContext(&builder, updateRect, &list);
  builder.LeavePresShell(rootFrame, &list);

  RebuildApproximateFrameVisibilityDisplayList(list);

  ClearApproximateFrameVisibilityVisited(rootFrame->GetView(), true);

  list.DeleteAll(&builder);
#endif
}

bool PresShell::AssumeAllFramesVisible() {
  static bool sFrameVisibilityEnabled = true;
  static bool sFrameVisibilityPrefCached = false;

  if (!sFrameVisibilityPrefCached) {
    Preferences::AddBoolVarCache(&sFrameVisibilityEnabled,
                                 "layout.framevisibility.enabled", true);
    sFrameVisibilityPrefCached = true;
  }

  if (!sFrameVisibilityEnabled || !mPresContext || !mDocument) {
    return true;
  }

  // We assume all frames are visible in print, print preview, chrome, and
  // resource docs and don't keep track of them.
  if (mPresContext->Type() == nsPresContext::eContext_PrintPreview ||
      mPresContext->Type() == nsPresContext::eContext_Print ||
      mPresContext->IsChrome() || mDocument->IsResourceDoc()) {
    return true;
  }

  // If we're assuming all frames are visible in the top level content
  // document, we need to in subdocuments as well. Otherwise we can get in a
  // situation where things like animations won't work in subdocuments because
  // their frames appear not to be visible, since we won't schedule an image
  // visibility update if the top level content document is assuming all
  // frames are visible.
  //
  // Note that it's not safe to call IsRootContentDocument() if we're
  // currently being destroyed, so we have to check that first.
  if (!mHaveShutDown && !mIsDestroying &&
      !mPresContext->IsRootContentDocument()) {
    nsPresContext* presContext =
        mPresContext->GetToplevelContentDocumentPresContext();
    if (presContext && presContext->PresShell()->AssumeAllFramesVisible()) {
      return true;
    }
  }

  return false;
}

void PresShell::ScheduleApproximateFrameVisibilityUpdateSoon() {
  if (AssumeAllFramesVisible()) {
    return;
  }

  if (!mPresContext) {
    return;
  }

  nsRefreshDriver* refreshDriver = mPresContext->RefreshDriver();
  if (!refreshDriver) {
    return;
  }

  // Ask the refresh driver to update frame visibility soon.
  refreshDriver->ScheduleFrameVisibilityUpdate();
}

void PresShell::ScheduleApproximateFrameVisibilityUpdateNow() {
  if (AssumeAllFramesVisible()) {
    return;
  }

  if (!mPresContext->IsRootContentDocument()) {
    nsPresContext* presContext =
        mPresContext->GetToplevelContentDocumentPresContext();
    if (!presContext) return;
    MOZ_ASSERT(presContext->IsRootContentDocument(),
               "Didn't get a root prescontext from "
               "GetToplevelContentDocumentPresContext?");
    presContext->PresShell()->ScheduleApproximateFrameVisibilityUpdateNow();
    return;
  }

  if (mHaveShutDown || mIsDestroying) {
    return;
  }

  if (mUpdateApproximateFrameVisibilityEvent.IsPending()) {
    return;
  }

  RefPtr<nsRunnableMethod<PresShell>> event =
      NewRunnableMethod("PresShell::UpdateApproximateFrameVisibility", this,
                        &PresShell::UpdateApproximateFrameVisibility);
  nsresult rv = mDocument->Dispatch(TaskCategory::Other, do_AddRef(event));

  if (NS_SUCCEEDED(rv)) {
    mUpdateApproximateFrameVisibilityEvent = std::move(event);
  }
}

void PresShell::EnsureFrameInApproximatelyVisibleList(nsIFrame* aFrame) {
  if (!aFrame->TrackingVisibility()) {
    return;
  }

  if (AssumeAllFramesVisible()) {
    aFrame->IncApproximateVisibleCount();
    return;
  }

#ifdef DEBUG
  // Make sure it's in this pres shell.
  nsCOMPtr<nsIContent> content = aFrame->GetContent();
  if (content) {
    PresShell* shell = static_cast<PresShell*>(content->OwnerDoc()->GetShell());
    MOZ_ASSERT(!shell || shell == this, "wrong shell");
  }
#endif

  if (mApproximatelyVisibleFrames.EnsureInserted(aFrame)) {
    // We inserted a new entry.
    aFrame->IncApproximateVisibleCount();
  }
}

void PresShell::RemoveFrameFromApproximatelyVisibleList(nsIFrame* aFrame) {
#ifdef DEBUG
  // Make sure it's in this pres shell.
  nsCOMPtr<nsIContent> content = aFrame->GetContent();
  if (content) {
    PresShell* shell = static_cast<PresShell*>(content->OwnerDoc()->GetShell());
    MOZ_ASSERT(!shell || shell == this, "wrong shell");
  }
#endif

  if (AssumeAllFramesVisible()) {
    MOZ_ASSERT(mApproximatelyVisibleFrames.Count() == 0,
               "Shouldn't have any frames in the table");
    return;
  }

  if (mApproximatelyVisibleFrames.EnsureRemoved(aFrame) &&
      aFrame->TrackingVisibility()) {
    // aFrame was in the hashtable, and we're still tracking its visibility,
    // so we need to decrement its visible count.
    aFrame->DecApproximateVisibleCount();
  }
}

class nsAutoNotifyDidPaint {
 public:
  nsAutoNotifyDidPaint(PresShell* aShell, uint32_t aFlags)
      : mShell(aShell), mFlags(aFlags) {}
  ~nsAutoNotifyDidPaint() {
    if (mFlags & nsIPresShell::PAINT_COMPOSITE) {
      mShell->GetPresContext()->NotifyDidPaintForSubtree();
    }
  }

 private:
  PresShell* mShell;
  uint32_t mFlags;
};

void nsIPresShell::RecordShadowStyleChange(ShadowRoot& aShadowRoot) {
  mStyleSet->RecordShadowStyleChange(aShadowRoot);
  ApplicableStylesChanged();
}

void PresShell::Paint(nsView* aViewToPaint, const nsRegion& aDirtyRegion,
                      uint32_t aFlags) {
  nsCString url;
  nsIURI* uri = mDocument->GetDocumentURI();
  Document* contentRoot = GetPrimaryContentDocument();
  if (contentRoot) {
    uri = contentRoot->GetDocumentURI();
  }
  url = uri ? uri->GetSpecOrDefault() : NS_LITERAL_CSTRING("N/A");
#ifdef MOZ_GECKO_PROFILER
  AUTO_PROFILER_LABEL_DYNAMIC_NSCSTRING("PresShell::Paint", GRAPHICS, url);
#endif

  Maybe<js::AutoAssertNoContentJS> nojs;

  // On Android, Flash can call into content JS during painting, so we can't
  // assert there. However, we don't rely on this assertion on Android because
  // we don't paint while JS is running.
#if !defined(MOZ_WIDGET_ANDROID)
  if (!(aFlags & nsIPresShell::PAINT_COMPOSITE)) {
    // We need to allow content JS when the flag is set since we may trigger
    // MozAfterPaint events in content in those cases.
    nojs.emplace(dom::danger::GetJSContext());
  }
#endif

  NS_ASSERTION(!mIsDestroying, "painting a destroyed PresShell");
  NS_ASSERTION(aViewToPaint, "null view");

  MOZ_ASSERT(!mApproximateFrameVisibilityVisited, "Should have been cleared");

  if (!mIsActive) {
    return;
  }

  if (gfxPrefs::APZKeyboardEnabled()) {
    // Update the focus target for async keyboard scrolling. This will be
    // forwarded to APZ by nsDisplayList::PaintRoot. We need to to do this
    // before we enter the paint phase because dispatching eVoid events can
    // cause layout to happen.
    mAPZFocusTarget = FocusTarget(this, mAPZFocusSequenceNumber);
  }

  nsPresContext* presContext = GetPresContext();
  AUTO_LAYOUT_PHASE_ENTRY_POINT(presContext, Paint);

  nsIFrame* frame = aViewToPaint->GetFrame();

  LayerManager* layerManager = aViewToPaint->GetWidget()->GetLayerManager();
  NS_ASSERTION(layerManager, "Must be in paint event");
  bool shouldInvalidate = layerManager->NeedsWidgetInvalidation();

  nsAutoNotifyDidPaint notifyDidPaint(this, aFlags);

  // Whether or not we should set first paint when painting is suppressed
  // is debatable. For now we'll do it because B2G relied on first paint
  // to configure the viewport and we only want to do that when we have
  // real content to paint. See Bug 798245
  if (mIsFirstPaint && !mPaintingSuppressed) {
    layerManager->SetIsFirstPaint();
    mIsFirstPaint = false;
  }

  if (!layerManager->BeginTransaction(url)) {
    return;
  }

  // Send an updated focus target with this transaction. Be sure to do this
  // before we paint in the case this is an empty transaction.
  layerManager->SetFocusTarget(mAPZFocusTarget);

  if (frame) {
    // Try to do an empty transaction, if the frame tree does not
    // need to be updated. Do not try to do an empty transaction on
    // a non-retained layer manager (like the BasicLayerManager that
    // draws the window title bar on Mac), because a) it won't work
    // and b) below we don't want to clear NS_FRAME_UPDATE_LAYER_TREE,
    // that will cause us to forget to update the real layer manager!

    if (!(aFlags & PAINT_LAYERS)) {
      if (layerManager->EndEmptyTransaction()) {
        return;
      }
      NS_WARNING("Must complete empty transaction when compositing!");
    }

    if (!(aFlags & PAINT_SYNC_DECODE_IMAGES) &&
        !(frame->GetStateBits() & NS_FRAME_UPDATE_LAYER_TREE) &&
        !mNextPaintCompressed) {
      NotifySubDocInvalidationFunc computeInvalidFunc =
          presContext->MayHavePaintEventListenerInSubDocument()
              ? nsPresContext::NotifySubDocInvalidation
              : 0;
      bool computeInvalidRect =
          computeInvalidFunc ||
          (layerManager->GetBackendType() == LayersBackend::LAYERS_BASIC);

      UniquePtr<LayerProperties> props;
      // For WR, the layermanager has no root layer. We want to avoid
      // calling ComputeDifferences in that case because it assumes non-null
      // and crashes.
      if (computeInvalidRect && layerManager->GetRoot()) {
        props = LayerProperties::CloneFrom(layerManager->GetRoot());
      }

      MaybeSetupTransactionIdAllocator(layerManager, presContext);

      if (layerManager->EndEmptyTransaction(
              (aFlags & PAINT_COMPOSITE) ? LayerManager::END_DEFAULT
                                         : LayerManager::END_NO_COMPOSITE)) {
        nsIntRegion invalid;
        bool areaOverflowed = false;
        if (props) {
          if (!props->ComputeDifferences(layerManager->GetRoot(), invalid,
                                         computeInvalidFunc)) {
            areaOverflowed = true;
          }
        } else {
          LayerProperties::ClearInvalidations(layerManager->GetRoot());
        }
        if (props && !areaOverflowed) {
          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) {
              aViewToPaint->GetViewManager()->InvalidateViewNoSuppression(
                  aViewToPaint, rect);
            }
            presContext->NotifyInvalidation(
                layerManager->GetLastTransactionId(), bounds);
          }
        } else if (shouldInvalidate) {
          aViewToPaint->GetViewManager()->InvalidateView(aViewToPaint);
        }

        frame->UpdatePaintCountForPaintedPresShells();
        return;
      }
    }
    frame->RemoveStateBits(NS_FRAME_UPDATE_LAYER_TREE);
  }
  if (frame) {
    frame->ClearPresShellsFromLastPaint();
  }

  nscolor bgcolor = ComputeBackstopColor(aViewToPaint);
  PaintFrameFlags flags = PaintFrameFlags::PAINT_WIDGET_LAYERS |
                          PaintFrameFlags::PAINT_EXISTING_TRANSACTION;
  if (!(aFlags & PAINT_COMPOSITE)) {
    flags |= PaintFrameFlags::PAINT_NO_COMPOSITE;
  }
  if (aFlags & PAINT_SYNC_DECODE_IMAGES) {
    flags |= PaintFrameFlags::PAINT_SYNC_DECODE_IMAGES;
  }
  if (mNextPaintCompressed) {
    flags |= PaintFrameFlags::PAINT_COMPRESSED;
    mNextPaintCompressed = false;
  }

  if (frame) {
    // We can paint directly into the widget using its layer manager.
    nsLayoutUtils::PaintFrame(nullptr, frame, aDirtyRegion, bgcolor,
                              nsDisplayListBuilderMode::PAINTING, flags);

    // When recording/replaying, create a checkpoint after every paint. This
    // can cause content JS to run, so reset |nojs|.
    if (recordreplay::IsRecordingOrReplaying()) {
      nojs.reset();
      recordreplay::child::CreateCheckpoint();
    }

    return;
  }

  if (layerManager->GetBackendType() ==