Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1092 insertions, 0 deletions

diff --git a/layout/generic/nsGfxScrollFrame.h b/layout/generic/nsGfxScrollFrame.h
new file mode 100644
index 0000000000..a85d3c0ec4
--- /dev/null
+++ b/layout/generic/nsGfxScrollFrame.h
@@ -0,0 +1,1092 @@
+/* -*- 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/. */
+
+/* rendering object to wrap rendering objects that should be scrollable */
+
+#ifndef nsGfxScrollFrame_h___
+#define nsGfxScrollFrame_h___
+
+#include "mozilla/Attributes.h"
+#include "nsContainerFrame.h"
+#include "nsIAnonymousContentCreator.h"
+#include "nsIScrollableFrame.h"
+#include "nsIScrollbarMediator.h"
+#include "nsIStatefulFrame.h"
+#include "nsThreadUtils.h"
+#include "nsIReflowCallback.h"
+#include "nsQueryFrame.h"
+#include "nsExpirationTracker.h"
+#include "TextOverflow.h"
+#include "ScrollVelocityQueue.h"
+#include "mozilla/ScrollTypes.h"
+#include "mozilla/PresState.h"
+#include "mozilla/layout/ScrollAnchorContainer.h"
+#include "mozilla/TypedEnumBits.h"
+
+class nsPresContext;
+class nsIContent;
+class nsAtom;
+class nsIScrollPositionListener;
+class AutoContainsBlendModeCapturer;
+
+namespace mozilla {
+class PresShell;
+struct ScrollReflowInput;
+struct StyleScrollSnapAlign;
+namespace layers {
+class Layer;
+class WebRenderLayerManager;
+}  // namespace layers
+namespace layout {
+class ScrollbarActivity;
+}  // namespace layout
+
+}  // namespace mozilla
+
+/**
+ * The scroll frame creates and manages the scrolling view
+ *
+ * It only supports having a single child frame that typically is an area
+ * frame, but doesn't have to be. The child frame must have a view, though
+ *
+ * Scroll frames don't support incremental changes, i.e. you can't replace
+ * or remove the scrolled frame
+ */
+class nsHTMLScrollFrame : public nsContainerFrame,
+                          public nsIScrollableFrame,
+                          public nsIAnonymousContentCreator,
+                          public nsIReflowCallback,
+                          public nsIStatefulFrame {
+ public:
+  using Sides = nsIFrame::Sides;
+  using ScrollbarActivity = mozilla::layout::ScrollbarActivity;
+  using ScrollSnapFlags = mozilla::ScrollSnapFlags;
+  using ScrollTriggeredByScript = mozilla::ScrollTriggeredByScript;
+  using ScrollSnapTargetIds = mozilla::ScrollSnapTargetIds;
+  using FrameMetrics = mozilla::layers::FrameMetrics;
+  using ScrollableLayerGuid = mozilla::layers::ScrollableLayerGuid;
+  using ScrollSnapInfo = mozilla::layers::ScrollSnapInfo;
+  using WebRenderLayerManager = mozilla::layers::WebRenderLayerManager;
+  using APZScrollAnimationType = mozilla::APZScrollAnimationType;
+  using ScrollDirections = mozilla::layers::ScrollDirections;
+  using ScrollDirection = mozilla::layers::ScrollDirection;
+  using Element = mozilla::dom::Element;
+  using SnapTargetSet = nsTHashSet<RefPtr<nsIContent>>;
+  using InScrollingGesture = nsIScrollableFrame::InScrollingGesture;
+
+  using CSSIntPoint = mozilla::CSSIntPoint;
+  using ScrollReflowInput = mozilla::ScrollReflowInput;
+  using ScrollAnchorContainer = mozilla::layout::ScrollAnchorContainer;
+  friend nsHTMLScrollFrame* NS_NewHTMLScrollFrame(
+      mozilla::PresShell* aPresShell, ComputedStyle* aStyle, bool aIsRoot);
+  friend class mozilla::layout::ScrollAnchorContainer;
+
+  NS_DECL_QUERYFRAME
+  NS_DECL_FRAMEARENA_HELPERS(nsHTMLScrollFrame)
+
+  void BuildDisplayList(nsDisplayListBuilder* aBuilder,
+                        const nsDisplayListSet& aLists) override;
+
+  bool TryLayout(ScrollReflowInput& aState, ReflowOutput* aKidMetrics,
+                 bool aAssumeHScroll, bool aAssumeVScroll, bool aForce);
+
+  // Return true if ReflowScrolledFrame is going to do something different based
+  // on the presence of a horizontal scrollbar in a horizontal writing mode or a
+  // vertical scrollbar in a vertical writing mode.
+  bool ScrolledContentDependsOnBSize(const ScrollReflowInput& aState) const;
+
+  void ReflowScrolledFrame(ScrollReflowInput& aState, bool aAssumeHScroll,
+                           bool aAssumeVScroll, ReflowOutput* aMetrics);
+  void ReflowContents(ScrollReflowInput& aState,
+                      const ReflowOutput& aDesiredSize);
+  void PlaceScrollArea(ScrollReflowInput& aState,
+                       const nsPoint& aScrollPosition);
+
+  // Return the sum of inline-size of the scrollbar gutters (if any) at the
+  // inline-start and inline-end edges of the scroll frame (for a potential
+  // scrollbar that scrolls in the block axis).
+  nscoord IntrinsicScrollbarGutterSizeAtInlineEdges(
+      gfxContext* aRenderingContext);
+
+  bool GetBorderRadii(const nsSize& aFrameSize, const nsSize& aBorderArea,
+                      Sides aSkipSides, nscoord aRadii[8]) const final;
+
+  nscoord GetMinISize(gfxContext* aRenderingContext) override;
+  nscoord GetPrefISize(gfxContext* aRenderingContext) override;
+
+  void Reflow(nsPresContext* aPresContext, ReflowOutput& aDesiredSize,
+              const ReflowInput& aReflowInput,
+              nsReflowStatus& aStatus) override;
+  void DidReflow(nsPresContext* aPresContext,
+                 const ReflowInput* aReflowInput) override;
+
+  bool ComputeCustomOverflow(mozilla::OverflowAreas& aOverflowAreas) final;
+
+  BaselineSharingGroup GetDefaultBaselineSharingGroup() const override;
+  nscoord SynthesizeFallbackBaseline(
+      mozilla::WritingMode aWM,
+      BaselineSharingGroup aBaselineGroup) const override;
+  Maybe<nscoord> GetNaturalBaselineBOffset(
+      mozilla::WritingMode aWM, BaselineSharingGroup aBaselineGroup,
+      BaselineExportContext aExportContext) const override;
+
+  // Recomputes the scrollable overflow area we store in the helper to take
+  // children that are affected by perpsective set on the outer frame and scroll
+  // at different rates.
+  void AdjustForPerspective(nsRect& aScrollableOverflow);
+
+  // Called to set the child frames. We typically have three: the scroll area,
+  // the vertical scrollbar, and the horizontal scrollbar.
+  void SetInitialChildList(ChildListID aListID,
+                           nsFrameList&& aChildList) override;
+  void AppendFrames(ChildListID aListID, nsFrameList&& aFrameList) final;
+  void InsertFrames(ChildListID aListID, nsIFrame* aPrevFrame,
+                    const nsLineList::iterator* aPrevFrameLine,
+                    nsFrameList&& aFrameList) final;
+  void RemoveFrame(DestroyContext&, ChildListID, nsIFrame*) final;
+
+  void DidSetComputedStyle(ComputedStyle* aOldComputedStyle) final;
+
+  void Destroy(DestroyContext&) override;
+
+  nsIScrollableFrame* GetScrollTargetFrame() const final {
+    return const_cast<nsHTMLScrollFrame*>(this);
+  }
+
+  nsContainerFrame* GetContentInsertionFrame() override {
+    return GetScrolledFrame()->GetContentInsertionFrame();
+  }
+
+  nsPoint GetPositionOfChildIgnoringScrolling(const nsIFrame* aChild) final {
+    nsPoint pt = aChild->GetPosition();
+    if (aChild == GetScrolledFrame()) {
+      pt += GetScrollPosition();
+    }
+    return pt;
+  }
+
+  // nsIAnonymousContentCreator
+  nsresult CreateAnonymousContent(nsTArray<ContentInfo>&) final;
+  void AppendAnonymousContentTo(nsTArray<nsIContent*>&, uint32_t aFilter) final;
+
+  // nsIScrollableFrame
+  nsIFrame* GetScrolledFrame() const final { return mScrolledFrame; }
+  mozilla::ScrollStyles GetScrollStyles() const final;
+  bool IsForTextControlWithNoScrollbars() const final;
+  bool HasAllNeededScrollbars() const final {
+    return GetCurrentAnonymousContent().contains(GetNeededAnonymousContent());
+  }
+
+  mozilla::layers::OverscrollBehaviorInfo GetOverscrollBehaviorInfo()
+      const final;
+  ScrollDirections GetAvailableScrollingDirectionsForUserInputEvents()
+      const final;
+  ScrollDirections GetScrollbarVisibility() const final {
+    ScrollDirections result;
+    if (mHasHorizontalScrollbar) {
+      result += ScrollDirection::eHorizontal;
+    }
+    if (mHasVerticalScrollbar) {
+      result += ScrollDirection::eVertical;
+    }
+    return result;
+  }
+  nsMargin GetActualScrollbarSizes(
+      nsIScrollableFrame::ScrollbarSizesOptions aOptions =
+          nsIScrollableFrame::ScrollbarSizesOptions::NONE) const final;
+  nsMargin GetDesiredScrollbarSizes() const final;
+  nsSize GetLayoutSize() const final {
+    if (mIsUsingMinimumScaleSize) {
+      return mICBSize;
+    }
+    return mScrollPort.Size();
+  }
+  /**
+   * GetScrolledRect is designed to encapsulate deciding which
+   * directions of overflow should be reachable by scrolling and which
+   * should not.  Callers should NOT depend on it having any particular
+   * behavior.
+   *
+   * This should only be called when the scrolled frame has been
+   * reflowed with the scroll port size given in mScrollPort.
+   *
+   * Currently it allows scrolling down and to the right for
+   * nsHTMLScrollFrames with LTR directionality, and allows scrolling down and
+   * to the left for nsHTMLScrollFrames with RTL directionality.
+   */
+  nsRect GetScrolledRect() const final;
+  nsRect GetScrollPortRect() const final { return mScrollPort; }
+  nsPoint GetScrollPosition() const final {
+    return mScrollPort.TopLeft() - mScrolledFrame->GetPosition();
+  }
+  /**
+   * For LTR frames, the logical scroll position is the offset of the top left
+   * corner of the frame from the top left corner of the scroll port (same as
+   * GetScrollPosition).
+   * For RTL frames, it is the offset of the top right corner of the frame from
+   * the top right corner of the scroll port
+   */
+  nsPoint GetLogicalScrollPosition() const final {
+    nsPoint pt;
+    pt.x = IsPhysicalLTR()
+               ? mScrollPort.x - mScrolledFrame->GetPosition().x
+               : mScrollPort.XMost() - mScrolledFrame->GetRect().XMost();
+    pt.y = mScrollPort.y - mScrolledFrame->GetPosition().y;
+    return pt;
+  }
+
+  nsRect GetScrollRange() const final { return GetLayoutScrollRange(); }
+  nsSize GetVisualViewportSize() const final;
+  nsPoint GetVisualViewportOffset() const final;
+  bool SetVisualViewportOffset(const nsPoint& aOffset, bool aRepaint) final;
+  nsRect GetVisualScrollRange() const final;
+  nsRect GetScrollRangeForUserInputEvents() const final;
+  nsSize GetLineScrollAmount() const final;
+  nsSize GetPageScrollAmount() const final;
+  nsMargin GetScrollPadding() const final;
+  /**
+   * @note This method might destroy the frame, pres shell and other objects.
+   */
+  void ScrollTo(nsPoint aScrollPosition, ScrollMode aMode,
+                const nsRect* aRange = nullptr,
+                ScrollSnapFlags aSnapFlags = ScrollSnapFlags::Disabled,
+                ScrollTriggeredByScript aTriggeredByScript =
+                    ScrollTriggeredByScript::No) final {
+    return ScrollToInternal(aScrollPosition, aMode, ScrollOrigin::Other, aRange,
+                            aSnapFlags, aTriggeredByScript);
+  }
+  /**
+   * @note This method might destroy the frame, pres shell and other objects.
+   */
+  void ScrollToCSSPixels(const CSSIntPoint& aScrollPosition,
+                         ScrollMode aMode = ScrollMode::Instant) final;
+  void ScrollToCSSPixelsForApz(const mozilla::CSSPoint& aScrollPosition,
+                               ScrollSnapTargetIds&& aLastSnapTargetIds) final;
+  /**
+   * @note This method might destroy the frame, pres shell and other objects.
+   */
+  CSSIntPoint GetScrollPositionCSSPixels() final;
+  /**
+   * @note This method might destroy the frame, pres shell and other objects.
+   */
+  void ScrollBy(nsIntPoint aDelta, mozilla::ScrollUnit aUnit, ScrollMode aMode,
+                nsIntPoint* aOverflow,
+                ScrollOrigin aOrigin = ScrollOrigin::NotSpecified,
+                nsIScrollableFrame::ScrollMomentum aMomentum =
+                    nsIScrollableFrame::NOT_MOMENTUM,
+                ScrollSnapFlags aSnapFlags = ScrollSnapFlags::Disabled) final;
+  void ScrollByCSSPixels(const CSSIntPoint& aDelta,
+                         ScrollMode aMode = ScrollMode::Instant) final {
+    return ScrollByCSSPixelsInternal(aDelta, aMode);
+  }
+  void ScrollByCSSPixelsInternal(
+      const CSSIntPoint& aDelta, ScrollMode aMode = ScrollMode::Instant,
+      // This ScrollByCSSPixels is mainly used for Element.scrollBy and
+      // Window.scrollBy. An exception is the transmogrification of
+      // ScrollToCSSPixels.
+      ScrollSnapFlags aSnapFlags = ScrollSnapFlags::IntendedDirection |
+                                   ScrollSnapFlags::IntendedEndPosition);
+
+  /**
+   * @note This method might destroy the frame, pres shell and other objects.
+   */
+  void ScrollToRestoredPosition() final;
+  /**
+   * @note This method might destroy the frame, pres shell and other objects.
+   */
+  void CurPosAttributeChanged(nsIContent* aChild) final {
+    return CurPosAttributeChangedInternal(aChild);
+  }
+  NS_IMETHOD PostScrolledAreaEventForCurrentArea() final {
+    PostScrolledAreaEvent();
+    return NS_OK;
+  }
+  bool IsScrollingActive() const final;
+  bool IsMaybeAsynchronouslyScrolled() const final {
+    // If this is true, then we'll build an ASR, and that's what we want
+    // to know I think.
+    return mWillBuildScrollableLayer;
+  }
+
+  bool DidHistoryRestore() const final { return mDidHistoryRestore; }
+  void ClearDidHistoryRestore() final { mDidHistoryRestore = false; }
+  void MarkEverScrolled() final;
+  bool IsRectNearlyVisible(const nsRect& aRect) const final;
+  nsRect ExpandRectToNearlyVisible(const nsRect& aRect) const final;
+  ScrollOrigin LastScrollOrigin() const final { return mLastScrollOrigin; }
+  using AnimationState = nsIScrollableFrame::AnimationState;
+  mozilla::EnumSet<AnimationState> ScrollAnimationState() const final;
+  mozilla::MainThreadScrollGeneration CurrentScrollGeneration() const final {
+    return mScrollGeneration;
+  }
+  mozilla::APZScrollGeneration ScrollGenerationOnApz() const final {
+    return mScrollGenerationOnApz;
+  }
+  nsPoint LastScrollDestination() final { return mDestination; }
+  nsTArray<mozilla::ScrollPositionUpdate> GetScrollUpdates() const final;
+  bool HasScrollUpdates() const final { return !mScrollUpdates.IsEmpty(); }
+  void ResetScrollInfoIfNeeded(
+      const mozilla::MainThreadScrollGeneration& aGeneration,
+      const mozilla::APZScrollGeneration& aGenerationOnApz,
+      mozilla::APZScrollAnimationType aAPZScrollAnimationType,
+      InScrollingGesture aInScrollingGesture) final;
+  bool WantAsyncScroll() const final;
+  mozilla::Maybe<mozilla::layers::ScrollMetadata> ComputeScrollMetadata(
+      mozilla::layers::WebRenderLayerManager* aLayerManager,
+      const nsIFrame* aItemFrame,
+      const nsPoint& aOffsetToReferenceFrame) const final;
+  void MarkScrollbarsDirtyForReflow() const final;
+  void InvalidateScrollbars() const final;
+
+  /**
+   * @note This method might destroy the frame, pres shell and other objects.
+   * Update scrollbar curpos attributes to reflect current scroll position
+   */
+  void UpdateScrollbarPosition() final;
+  bool DecideScrollableLayer(nsDisplayListBuilder* aBuilder,
+                             nsRect* aVisibleRect, nsRect* aDirtyRect,
+                             bool aSetBase) final {
+    return DecideScrollableLayer(aBuilder, aVisibleRect, aDirtyRect, aSetBase,
+                                 nullptr);
+  }
+  void NotifyApzTransaction() final;
+  void NotifyApproximateFrameVisibilityUpdate(bool aIgnoreDisplayPort) final;
+  bool GetDisplayPortAtLastApproximateFrameVisibilityUpdate(
+      nsRect* aDisplayPort) final;
+  void TriggerDisplayPortExpiration() final;
+
+  // nsIStatefulFrame
+  mozilla::UniquePtr<mozilla::PresState> SaveState() final;
+  NS_IMETHOD RestoreState(mozilla::PresState* aState) final;
+
+  // nsIScrollbarMediator
+  void ScrollByPage(
+      nsScrollbarFrame* aScrollbar, int32_t aDirection,
+      ScrollSnapFlags aSnapFlags = ScrollSnapFlags::Disabled) final;
+  void ScrollByWhole(
+      nsScrollbarFrame* aScrollbar, int32_t aDirection,
+      ScrollSnapFlags aSnapFlags = ScrollSnapFlags::Disabled) final;
+  void ScrollByLine(nsScrollbarFrame* aScrollbar, int32_t aDirection,
+                    ScrollSnapFlags = ScrollSnapFlags::Disabled) final;
+  void ScrollByUnit(nsScrollbarFrame* aScrollbar, ScrollMode aMode,
+                    int32_t aDirection, mozilla::ScrollUnit aUnit,
+                    ScrollSnapFlags = ScrollSnapFlags::Disabled) final;
+  void RepeatButtonScroll(nsScrollbarFrame* aScrollbar) final;
+  void ThumbMoved(nsScrollbarFrame* aScrollbar, nscoord aOldPos,
+                  nscoord aNewPos) final;
+  void ScrollbarReleased(nsScrollbarFrame* aScrollbar) final;
+  void VisibilityChanged(bool aVisible) final {}
+  nsScrollbarFrame* GetScrollbarBox(bool aVertical) final {
+    return aVertical ? mVScrollbarBox : mHScrollbarBox;
+  }
+
+  void ScrollbarActivityStarted() const final;
+  void ScrollbarActivityStopped() const final;
+
+  bool IsScrollbarOnRight() const final;
+
+  bool ShouldSuppressScrollbarRepaints() const final {
+    return mSuppressScrollbarRepaints;
+  }
+  void SetTransformingByAPZ(bool aTransforming) final;
+  bool IsTransformingByAPZ() const final { return mTransformingByAPZ; }
+  void SetScrollableByAPZ(bool aScrollable) final;
+  void SetZoomableByAPZ(bool aZoomable) final;
+  void SetHasOutOfFlowContentInsideFilter() final;
+  ScrollSnapInfo GetScrollSnapInfo() final;
+
+  void TryResnap() final;
+  void PostPendingResnapIfNeeded(const nsIFrame* aFrame) final;
+  void PostPendingResnap() final;
+  using PhysicalScrollSnapAlign = nsIScrollableFrame::PhysicalScrollSnapAlign;
+  PhysicalScrollSnapAlign GetScrollSnapAlignFor(
+      const nsIFrame* aFrame) const final;
+
+  bool DragScroll(mozilla::WidgetEvent* aEvent) final;
+
+  void AsyncScrollbarDragInitiated(
+      uint64_t aDragBlockId, mozilla::layers::ScrollDirection aDirection) final;
+
+  void AsyncScrollbarDragRejected() final;
+
+  bool IsRootScrollFrameOfDocument() const final { return mIsRoot; }
+
+  Maybe<uint32_t> IsFirstScrollableFrameSequenceNumber() const final {
+    return mIsFirstScrollableFrameSequenceNumber;
+  }
+
+  void SetIsFirstScrollableFrameSequenceNumber(Maybe<uint32_t> aValue) final {
+    mIsFirstScrollableFrameSequenceNumber = aValue;
+  }
+
+  const ScrollAnchorContainer* Anchor() const final { return &mAnchor; }
+  ScrollAnchorContainer* Anchor() final { return &mAnchor; }
+
+  // Return the scrolled frame.
+  void AppendDirectlyOwnedAnonBoxes(nsTArray<OwnedAnonBox>& aResult) final {
+    aResult.AppendElement(OwnedAnonBox(GetScrolledFrame()));
+  }
+
+  bool SmoothScrollVisual(
+      const nsPoint& aVisualViewportOffset,
+      mozilla::layers::FrameMetrics::ScrollOffsetUpdateType aUpdateType) final;
+
+  bool IsSmoothScroll(mozilla::dom::ScrollBehavior aBehavior) const final;
+
+#ifdef DEBUG_FRAME_DUMP
+  nsresult GetFrameName(nsAString& aResult) const override;
+#endif
+
+#ifdef ACCESSIBILITY
+  mozilla::a11y::AccType AccessibleType() override;
+#endif
+
+ protected:
+  nsHTMLScrollFrame(ComputedStyle* aStyle, nsPresContext* aPresContext,
+                    bool aIsRoot)
+      : nsHTMLScrollFrame(aStyle, aPresContext, kClassID, aIsRoot) {}
+  nsHTMLScrollFrame(ComputedStyle* aStyle, nsPresContext* aPresContext,
+                    nsIFrame::ClassID aID, bool aIsRoot);
+  ~nsHTMLScrollFrame();
+  void SetSuppressScrollbarUpdate(bool aSuppress) {
+    mSuppressScrollbarUpdate = aSuppress;
+  }
+  bool GuessHScrollbarNeeded(const ScrollReflowInput& aState);
+  bool GuessVScrollbarNeeded(const ScrollReflowInput& aState);
+
+  bool IsScrollbarUpdateSuppressed() const { return mSuppressScrollbarUpdate; }
+
+  // Return whether we're in an "initial" reflow.  Some reflows with
+  // NS_FRAME_FIRST_REFLOW set are NOT "initial" as far as we're concerned.
+  bool InInitialReflow() const;
+
+  /**
+   * Override this to return false if computed bsize/min-bsize/max-bsize
+   * should NOT be propagated to child content.
+   * nsListControlFrame uses this.
+   */
+  virtual bool ShouldPropagateComputedBSizeToScrolledContent() const {
+    return true;
+  }
+
+ private:
+  class AsyncScroll;
+  class AsyncSmoothMSDScroll;
+
+  enum class AnonymousContentType {
+    VerticalScrollbar,
+    HorizontalScrollbar,
+    Resizer,
+  };
+  mozilla::EnumSet<AnonymousContentType> GetNeededAnonymousContent() const;
+  mozilla::EnumSet<AnonymousContentType> GetCurrentAnonymousContent() const;
+
+  // If a child frame was added or removed on the scrollframe,
+  // reload our child frame list.
+  // We need this if a scrollbar frame is recreated.
+  void ReloadChildFrames();
+
+ public:
+  enum class OverflowState : uint32_t {
+    None = 0,
+    Vertical = (1 << 0),
+    Horizontal = (1 << 1),
+  };
+
+ protected:
+  OverflowState GetOverflowState() const;
+
+  MOZ_CAN_RUN_SCRIPT nsresult FireScrollPortEvent();
+  void PostScrollEndEvent();
+  MOZ_CAN_RUN_SCRIPT void FireScrollEndEvent();
+  void PostOverflowEvent();
+
+  // Add display items for the top-layer (which includes things like
+  // the fullscreen element, its backdrop, and text selection carets)
+  // to |aLists|.
+  // This is a no-op for scroll frames other than the viewport's
+  // root scroll frame.
+  // This should be called with an nsDisplayListSet that will be
+  // wrapped in the async zoom container, if we're building one.
+  // It should not be called with an ASR setter on the stack, as the
+  // top-layer items handle setting up their own ASRs.
+  void MaybeCreateTopLayerAndWrapRootItems(
+      nsDisplayListBuilder*, mozilla::nsDisplayListCollection&,
+      bool aCreateAsyncZoom,
+      AutoContainsBlendModeCapturer* aAsyncZoomBlendCapture,
+      const nsRect& aAsyncZoomClipRect, nscoord* aRadii);
+
+  void AppendScrollPartsTo(nsDisplayListBuilder* aBuilder,
+                           const nsDisplayListSet& aLists, bool aCreateLayer,
+                           bool aPositioned);
+
+  // nsIReflowCallback
+  bool ReflowFinished() final;
+  void ReflowCallbackCanceled() final;
+
+  /**
+   * @note This method might destroy the frame, pres shell and other objects.
+   * Called when the 'curpos' attribute on one of the scrollbars changes.
+   */
+  void CurPosAttributeChangedInternal(nsIContent*, bool aDoScroll = true);
+
+  void PostScrollEvent(bool aDelayed = false);
+  MOZ_CAN_RUN_SCRIPT void FireScrollEvent();
+  void PostScrolledAreaEvent();
+  MOZ_CAN_RUN_SCRIPT void FireScrolledAreaEvent();
+
+  /**
+   * @note This method might destroy the frame, pres shell and other objects.
+   */
+  void FinishReflowForScrollbar(Element* aElement, nscoord aMinXY,
+                                nscoord aMaxXY, nscoord aCurPosXY,
+                                nscoord aPageIncrement, nscoord aIncrement);
+  /**
+   * @note This method might destroy the frame, pres shell and other objects.
+   */
+  void SetScrollbarEnabled(Element* aElement, nscoord aMaxPos);
+  /**
+   * @note This method might destroy the frame, pres shell and other objects.
+   */
+  void SetCoordAttribute(Element* aElement, nsAtom* aAtom, nscoord aSize);
+
+  nscoord GetCoordAttribute(nsIFrame* aFrame, nsAtom* aAtom,
+                            nscoord aDefaultValue, nscoord* aRangeStart,
+                            nscoord* aRangeLength);
+
+  nsRect GetLayoutScrollRange() const;
+  // Get the scroll range assuming the viewport has size (aWidth, aHeight).
+  nsRect GetScrollRange(nscoord aWidth, nscoord aHeight) const;
+
+  const nsRect& ScrollPort() const { return mScrollPort; }
+  void SetScrollPort(const nsRect& aNewScrollPort) {
+    if (!mScrollPort.IsEqualEdges(aNewScrollPort)) {
+      mMayScheduleScrollAnimations = true;
+    }
+    mScrollPort = aNewScrollPort;
+  }
+
+  /**
+   * Return the 'optimal viewing region' as a rect suitable for use by
+   * scroll anchoring. This rect is in the same coordinate space as
+   * 'GetScrollPortRect', and accounts for 'scroll-padding' as defined by:
+   *
+   * https://drafts.csswg.org/css-scroll-snap-1/#optimal-viewing-region
+   */
+  nsRect GetVisualOptimalViewingRect() const;
+
+  /**
+   * For LTR frames, this is the same as GetVisualViewportOffset().
+   * For RTL frames, we take the offset from the top right corner of the frame
+   * to the top right corner of the visual viewport.
+   */
+  nsPoint GetLogicalVisualViewportOffset() const {
+    nsPoint pt = GetVisualViewportOffset();
+    if (!IsPhysicalLTR()) {
+      pt.x += GetVisualViewportSize().width - mScrolledFrame->GetRect().width;
+    }
+    return pt;
+  }
+  void ScrollSnap() final { return ScrollSnap(ScrollMode::SmoothMsd); }
+  void ScrollSnap(ScrollMode aMode);
+  void ScrollSnap(const nsPoint& aDestination,
+                  ScrollMode aMode = ScrollMode::SmoothMsd);
+
+  bool HasPendingScrollRestoration() const {
+    return mRestorePos != nsPoint(-1, -1);
+  }
+
+  bool IsProcessingScrollEvent() const { return mProcessingScrollEvent; }
+
+ public:
+  static void AsyncScrollCallback(nsHTMLScrollFrame* aInstance,
+                                  mozilla::TimeStamp aTime);
+  static void AsyncSmoothMSDScrollCallback(nsHTMLScrollFrame* aInstance,
+                                           mozilla::TimeDuration aDeltaTime);
+  /**
+   * @note This method might destroy the frame, pres shell and other objects.
+   * aRange is the range of allowable scroll positions around the desired
+   * aScrollPosition. Null means only aScrollPosition is allowed.
+   * This is a closed-ended range --- aRange.XMost()/aRange.YMost() are allowed.
+   */
+  void ScrollToInternal(
+      nsPoint aScrollPosition, ScrollMode aMode,
+      ScrollOrigin aOrigin = ScrollOrigin::NotSpecified,
+      const nsRect* aRange = nullptr,
+      ScrollSnapFlags aSnapFlags = ScrollSnapFlags::Disabled,
+      ScrollTriggeredByScript aTriggeredByScript = ScrollTriggeredByScript::No);
+  /**
+   * @note This method might destroy the frame, pres shell and other objects.
+   */
+  void ScrollToImpl(
+      nsPoint aPt, const nsRect& aRange,
+      ScrollOrigin aOrigin = ScrollOrigin::NotSpecified,
+      ScrollTriggeredByScript aTriggeredByScript = ScrollTriggeredByScript::No);
+  void ScrollVisual();
+
+  enum class LoadingState { Loading, Stopped, Loaded };
+
+  LoadingState GetPageLoadingState();
+
+  /**
+   * GetSnapPointForDestination determines which point to snap to after
+   * scrolling. aStartPos gives the position before scrolling and aDestination
+   * gives the position after scrolling, with no snapping. Behaviour is
+   * dependent on the value of aUnit.
+   * Returns true if a suitable snap point could be found and aDestination has
+   * been updated to a valid snapping position.
+   */
+  Maybe<mozilla::SnapTarget> GetSnapPointForDestination(
+      mozilla::ScrollUnit aUnit, ScrollSnapFlags aFlags,
+      const nsPoint& aStartPos, const nsPoint& aDestination);
+
+  Maybe<mozilla::SnapTarget> GetSnapPointForResnap();
+  bool NeedsResnap();
+
+  void SetLastSnapTargetIds(mozilla::UniquePtr<ScrollSnapTargetIds> aId);
+  void AddScrollPositionListener(nsIScrollPositionListener* aListener) final {
+    mListeners.AppendElement(aListener);
+  }
+  void RemoveScrollPositionListener(
+      nsIScrollPositionListener* aListener) final {
+    mListeners.RemoveElement(aListener);
+  }
+
+  static void SetScrollbarVisibility(nsIFrame* aScrollbar, bool aVisible);
+
+  /**
+   * GetUnsnappedScrolledRectInternal is designed to encapsulate deciding which
+   * directions of overflow should be reachable by scrolling and which
+   * should not.  Callers should NOT depend on it having any particular
+   * behavior.
+   *
+   * Currently it allows scrolling down and to the right for
+   * nsHTMLScrollFrames with LTR directionality, and allows scrolling down and
+   * to the left for nsHTMLScrollFrames with RTL directionality.
+   */
+  nsRect GetUnsnappedScrolledRectInternal(const nsRect& aScrolledOverflowArea,
+                                          const nsSize& aScrollPortSize) const;
+
+  bool IsPhysicalLTR() const { return GetWritingMode().IsPhysicalLTR(); }
+  bool IsBidiLTR() const { return GetWritingMode().IsBidiLTR(); }
+
+ private:
+  // NOTE: Use GetScrollStylesFromFrame() if you want to know `overflow`
+  // and `overflow-behavior` properties.
+  nsIFrame* GetFrameForStyle() const;
+
+  // Compute all scroll snap related information and store eash snap target
+  // element in |mSnapTargets|.
+  ScrollSnapInfo ComputeScrollSnapInfo();
+
+  bool NeedsScrollSnap() const;
+
+  // Returns the snapport size of this scroll container.
+  // https://drafts.csswg.org/css-scroll-snap/#scroll-snapport
+  nsSize GetSnapportSize() const;
+
+  // Schedule the scroll-driven animations.
+  void ScheduleScrollAnimations();
+  void TryScheduleScrollAnimations() {
+    if (!mMayScheduleScrollAnimations) {
+      return;
+    }
+    ScheduleScrollAnimations();
+    mMayScheduleScrollAnimations = false;
+  }
+
+ public:
+  void UpdateSticky();
+
+  void UpdatePrevScrolledRect();
+
+  // adjust the scrollbar rectangle aRect to account for any visible resizer.
+  // aHasResizer specifies if there is a content resizer, however this method
+  // will also check if a widget resizer is present as well.
+  void AdjustScrollbarRectForResizer(
+      nsIFrame* aFrame, nsPresContext* aPresContext, nsRect& aRect,
+      bool aHasResizer, mozilla::layers::ScrollDirection aDirection);
+  void LayoutScrollbars(ScrollReflowInput& aState,
+                        const nsRect& aInsideBorderArea,
+                        const nsRect& aOldScrollPort);
+
+  void LayoutScrollbarPartAtRect(const ScrollReflowInput&,
+                                 ReflowInput& aKidReflowInput, const nsRect&);
+
+  bool IsAlwaysActive() const;
+  void MarkRecentlyScrolled();
+  void MarkNotRecentlyScrolled();
+  nsExpirationState* GetExpirationState() { return &mActivityExpirationState; }
+
+  bool UsesOverlayScrollbars() const;
+  bool IsLastSnappedTarget(const nsIFrame* aFrame) const;
+
+  static bool ShouldActivateAllScrollFrames();
+  nsRect RestrictToRootDisplayPort(const nsRect& aDisplayportBase);
+  bool DecideScrollableLayer(nsDisplayListBuilder* aBuilder,
+                             nsRect* aVisibleRect, nsRect* aDirtyRect,
+                             bool aSetBase,
+                             bool* aDirtyRectHasBeenOverriden = nullptr);
+  bool AllowDisplayPortExpiration();
+  void ResetDisplayPortExpiryTimer();
+
+  void ScheduleSyntheticMouseMove();
+  static void ScrollActivityCallback(nsITimer* aTimer, void* anInstance);
+
+  void HandleScrollbarStyleSwitching();
+
+  bool IsApzAnimationInProgress() const {
+    return mCurrentAPZScrollAnimationType != APZScrollAnimationType::No;
+  }
+  nsPoint LastScrollDestination() const { return mDestination; }
+
+  bool IsLastScrollUpdateAnimating() const;
+  bool IsLastScrollUpdateTriggeredByScriptAnimating() const;
+
+  // Update minimum-scale size.  The minimum-scale size will be set/used only
+  // if there is overflow-x:hidden region.
+  void UpdateMinimumScaleSize(const nsRect& aScrollableOverflow,
+                              const nsSize& aICBSize);
+
+  // Return the scroll frame's "true outer size".
+  // This is GetSize(), except when we've been sized to reflect a virtual
+  // (layout) viewport in which case this returns the outer size used to size
+  // the physical (visual) viewport.
+  nsSize TrueOuterSize(nsDisplayListBuilder* aBuilder) const;
+
+  already_AddRefed<Element> MakeScrollbar(mozilla::dom::NodeInfo* aNodeInfo,
+                                          bool aVertical,
+                                          mozilla::AnonymousContentKey& aKey);
+
+  void AppendScrollUpdate(const mozilla::ScrollPositionUpdate& aUpdate);
+
+  // owning references to the nsIAnonymousContentCreator-built content
+  nsCOMPtr<Element> mHScrollbarContent;
+  nsCOMPtr<Element> mVScrollbarContent;
+  nsCOMPtr<Element> mScrollCornerContent;
+  nsCOMPtr<Element> mResizerContent;
+
+  class ScrollEvent;
+  class ScrollEndEvent;
+  class AsyncScrollPortEvent;
+  class ScrolledAreaEvent;
+
+  RefPtr<ScrollEvent> mScrollEvent;
+  RefPtr<ScrollEndEvent> mScrollEndEvent;
+  nsRevocableEventPtr<AsyncScrollPortEvent> mAsyncScrollPortEvent;
+  nsRevocableEventPtr<ScrolledAreaEvent> mScrolledAreaEvent;
+  nsScrollbarFrame* mHScrollbarBox;
+  nsScrollbarFrame* mVScrollbarBox;
+  nsIFrame* mScrolledFrame;
+  nsIFrame* mScrollCornerBox;
+  nsIFrame* mResizerBox;
+  const nsIFrame* mReferenceFrameDuringPainting;
+  RefPtr<AsyncScroll> mAsyncScroll;
+  RefPtr<AsyncSmoothMSDScroll> mAsyncSmoothMSDScroll;
+  RefPtr<ScrollbarActivity> mScrollbarActivity;
+  nsTArray<nsIScrollPositionListener*> mListeners;
+  ScrollOrigin mLastScrollOrigin;
+  Maybe<nsPoint> mApzSmoothScrollDestination;
+  mozilla::MainThreadScrollGeneration mScrollGeneration;
+  mozilla::APZScrollGeneration mScrollGenerationOnApz;
+
+  nsTArray<mozilla::ScrollPositionUpdate> mScrollUpdates;
+
+  nsSize mMinimumScaleSize;
+
+  // Stores the ICB size for the root document if this frame is using the
+  // minimum scale size for |mScrollPort|.
+  nsSize mICBSize;
+
+  // Where we're currently scrolling to, if we're scrolling asynchronously.
+  // If we're not in the middle of an asynchronous scroll then this is
+  // just the current scroll position. ScrollBy will choose its
+  // destination based on this value.
+  nsPoint mDestination;
+
+  // A goal position to try to scroll to as content loads. As long as mLastPos
+  // matches the current logical scroll position, we try to scroll to
+  // mRestorePos after every reflow --- because after each time content is
+  // loaded/added to the scrollable element, there will be a reflow.
+  // Note that for frames where layout and visual viewport aren't one and the
+  // same thing, this scroll position will be the logical scroll position of
+  // the *visual* viewport, as its position will be more relevant to the user.
+  nsPoint mRestorePos;
+  // The last logical position we scrolled to while trying to restore
+  // mRestorePos, or 0,0 when this is a new frame. Set to -1,-1 once we've
+  // scrolled for any reason other than trying to restore mRestorePos.
+  // Just as with mRestorePos, this position will be the logical position of
+  // the *visual* viewport where available.
+  nsPoint mLastPos;
+
+  // The latest scroll position we've sent or received from APZ. This
+  // represents the main thread's best knowledge of the APZ scroll position,
+  // and is used to calculate relative scroll offset updates.
+  nsPoint mApzScrollPos;
+
+  nsExpirationState mActivityExpirationState;
+
+  nsCOMPtr<nsITimer> mScrollActivityTimer;
+
+  // The scroll position where we last updated frame visibility.
+  nsPoint mLastUpdateFramesPos;
+  nsRect mDisplayPortAtLastFrameUpdate;
+
+  nsRect mPrevScrolledRect;
+
+  ScrollableLayerGuid::ViewID mScrollParentID;
+
+  // Timer to remove the displayport some time after scrolling has stopped
+  nsCOMPtr<nsITimer> mDisplayPortExpiryTimer;
+
+  ScrollAnchorContainer mAnchor;
+
+  // We keep holding a strong reference for each snap target element until the
+  // next snapping happens so that it avoids using the same nsIContent* pointer
+  // for newly created contents in this scroll container. Otherwise we will try
+  // to match different nsIContent(s) generated at the same address during
+  // re-snapping.
+  SnapTargetSet mSnapTargets;
+
+  // Representing there's an APZ animation is in progress and what caused the
+  // animation. Note that this is only set when repainted via APZ, which means
+  // that there may be a request for an APZ animation in flight for example,
+  // while this is still `No`. In order to answer "is an APZ animation in the
+  // process of starting or in progress" you need to check mScrollUpdates,
+  // mApzAnimationRequested, and this type.
+  APZScrollAnimationType mCurrentAPZScrollAnimationType;
+
+  // The paint sequence number if the scroll frame is the first scrollable frame
+  // encountered.
+  Maybe<uint32_t> mIsFirstScrollableFrameSequenceNumber;
+
+  // Representing whether the APZC corresponding to this frame is now in the
+  // middle of handling a gesture (e.g. a pan gesture).
+  InScrollingGesture mInScrollingGesture : 1;
+
+  bool mAllowScrollOriginDowngrade : 1;
+  bool mHadDisplayPortAtLastFrameUpdate : 1;
+
+  // True if the most recent reflow of the scroll container frame has
+  // the vertical scrollbar shown.
+  bool mHasVerticalScrollbar : 1;
+  // True if the most recent reflow of the scroll container frame has the
+  // horizontal scrollbar shown.
+  bool mHasHorizontalScrollbar : 1;
+
+  // If mHas(Vertical|Horizontal)Scrollbar is true then
+  // mOnlyNeed(V|H)ScrollbarToScrollVVInsideLV indicates if the only reason we
+  // need that scrollbar is to scroll the visual viewport inside the layout
+  // viewport. These scrollbars are special in that even if they are layout
+  // scrollbars they do not take up any layout space.
+  bool mOnlyNeedVScrollbarToScrollVVInsideLV : 1;
+  bool mOnlyNeedHScrollbarToScrollVVInsideLV : 1;
+  bool mFrameIsUpdatingScrollbar : 1;
+  bool mDidHistoryRestore : 1;
+  // Is this the scrollframe for the document's viewport?
+  bool mIsRoot : 1;
+  // If true, don't try to layout the scrollbars in Reflow().  This can be
+  // useful if multiple passes are involved, because we don't want to place the
+  // scrollbars at the wrong size.
+  bool mSuppressScrollbarUpdate : 1;
+  // If true, we skipped a scrollbar layout due to mSuppressScrollbarUpdate
+  // being set at some point.  That means we should lay out scrollbars even if
+  // it might not strictly be needed next time mSuppressScrollbarUpdate is
+  // false.
+  bool mSkippedScrollbarLayout : 1;
+
+  bool mHadNonInitialReflow : 1;
+  // Initially true; first call to ReflowFinished() sets it to false.
+  bool mFirstReflow : 1;
+  // State used only by PostScrollEvents so we know
+  // which overflow states have changed.
+  bool mHorizontalOverflow : 1;
+  bool mVerticalOverflow : 1;
+  bool mPostedReflowCallback : 1;
+  bool mMayHaveDirtyFixedChildren : 1;
+  // If true, need to actually update our scrollbar attributes in the
+  // reflow callback.
+  bool mUpdateScrollbarAttributes : 1;
+  // If true, we should be prepared to scroll using this scrollframe
+  // by placing descendant content into its own layer(s)
+  bool mHasBeenScrolledRecently : 1;
+
+  // If true, the scroll frame should always be active because we always build
+  // a scrollable layer. Used for asynchronous scrolling.
+  bool mWillBuildScrollableLayer : 1;
+
+  // If true, the scroll frame is an ancestor of other "active" scrolling
+  // frames, where "active" means has a non-minimal display port if
+  // ShouldActivateAllScrollFrames is true, or has a display port if
+  // ShouldActivateAllScrollFrames is false. And this means that we shouldn't
+  // expire the display port (if ShouldActivateAllScrollFrames is true then
+  // expiring a display port means making it minimal, otherwise it means
+  // removing the display port). If those descendant scrollframes have their
+  // display ports removed or made minimal, then we expire our display port.
+  bool mIsParentToActiveScrollFrames : 1;
+
+  // True if this frame has been scrolled at least once
+  bool mHasBeenScrolled : 1;
+
+  // True if the events synthesized by OSX to produce momentum scrolling should
+  // be ignored.  Reset when the next real, non-synthesized scroll event occurs.
+  bool mIgnoreMomentumScroll : 1;
+
+  // True if the APZ is in the process of async-transforming this scrollframe,
+  // (as best as we can tell on the main thread, anyway).
+  bool mTransformingByAPZ : 1;
+
+  // True if APZ can scroll this frame asynchronously (i.e. it has an APZC
+  // set up for this frame and it's not a scrollinfo layer).
+  bool mScrollableByAPZ : 1;
+
+  // True if the APZ is allowed to zoom this scrollframe.
+  bool mZoomableByAPZ : 1;
+
+  // True if the scroll frame contains out-of-flow content and is inside
+  // a CSS filter.
+  bool mHasOutOfFlowContentInsideFilter : 1;
+
+  // True if we don't want the scrollbar to repaint itself right now.
+  bool mSuppressScrollbarRepaints : 1;
+
+  // True if we are using the minimum scale size instead of ICB for scroll port.
+  bool mIsUsingMinimumScaleSize : 1;
+
+  // True if the minimum scale size has been changed since the last reflow.
+  bool mMinimumScaleSizeChanged : 1;
+
+  // True if we're processing an scroll event.
+  bool mProcessingScrollEvent : 1;
+
+  // This is true from the time a scroll animation is requested of APZ to the
+  // time that APZ responds with an up-to-date repaint request. More precisely,
+  // this is flipped to true if a repaint request is dispatched to APZ where
+  // the most recent scroll request is a smooth scroll, and it is cleared when
+  // mApzAnimationInProgress is updated.
+  bool mApzAnimationRequested : 1;
+
+  // Similar to above mApzAnimationRequested but the request came from script,
+  // e.g., scrollBy().
+  bool mApzAnimationTriggeredByScriptRequested : 1;
+
+  // Whether we need to reclamp the visual viewport offset in ReflowFinished.
+  bool mReclampVVOffsetInReflowFinished : 1;
+
+  // Whether we need to schedule the scroll-driven animations.
+  bool mMayScheduleScrollAnimations : 1;
+
+#ifdef MOZ_WIDGET_ANDROID
+  // True if this scrollable frame was vertically overflowed on the last reflow.
+  bool mHasVerticalOverflowForDynamicToolbar : 1;
+#endif
+
+  mozilla::layout::ScrollVelocityQueue mVelocityQueue;
+
+ protected:
+  class AutoScrollbarRepaintSuppression;
+  friend class AutoScrollbarRepaintSuppression;
+  class AutoScrollbarRepaintSuppression {
+   public:
+    AutoScrollbarRepaintSuppression(nsHTMLScrollFrame* aFrame,
+                                    AutoWeakFrame& aWeakOuter, bool aSuppress)
+        : mFrame(aFrame),
+          mWeakOuter(aWeakOuter),
+          mOldSuppressValue(aFrame->mSuppressScrollbarRepaints) {
+      mFrame->mSuppressScrollbarRepaints = aSuppress;
+    }
+
+    ~AutoScrollbarRepaintSuppression() {
+      if (mWeakOuter.IsAlive()) {
+        mFrame->mSuppressScrollbarRepaints = mOldSuppressValue;
+      }
+    }
+
+   private:
+    nsHTMLScrollFrame* mFrame;
+    AutoWeakFrame& mWeakOuter;
+    bool mOldSuppressValue;
+  };
+
+  struct ScrollOperationParams {
+    ScrollOperationParams(const ScrollOperationParams&) = delete;
+    ScrollOperationParams(ScrollMode aMode, ScrollOrigin aOrigin)
+        : mMode(aMode), mOrigin(aOrigin) {}
+    ScrollOperationParams(ScrollMode aMode, ScrollOrigin aOrigin,
+                          ScrollSnapTargetIds&& aSnapTargetIds)
+        : ScrollOperationParams(aMode, aOrigin) {
+      mTargetIds = std::move(aSnapTargetIds);
+    }
+    ScrollOperationParams(ScrollMode aMode, ScrollOrigin aOrigin,
+                          ScrollSnapFlags aSnapFlags,
+                          ScrollTriggeredByScript aTriggeredByScript)
+        : ScrollOperationParams(aMode, aOrigin) {
+      mSnapFlags = aSnapFlags;
+      mTriggeredByScript = aTriggeredByScript;
+    }
+
+    ScrollMode mMode;
+    ScrollOrigin mOrigin;
+    ScrollSnapFlags mSnapFlags = ScrollSnapFlags::Disabled;
+    ScrollTriggeredByScript mTriggeredByScript = ScrollTriggeredByScript::No;
+    ScrollSnapTargetIds mTargetIds;
+
+    bool IsInstant() const { return mMode == ScrollMode::Instant; }
+    bool IsSmoothMsd() const { return mMode == ScrollMode::SmoothMsd; }
+    bool IsSmooth() const { return mMode == ScrollMode::Smooth; }
+    bool IsScrollSnapDisabled() const {
+      return mSnapFlags == ScrollSnapFlags::Disabled;
+    }
+  };
+
+  /**
+   * @note This method might destroy the frame, pres shell and other objects.
+   *
+   * A caller can ask this ScrollToWithOrigin() function to perform snapping by
+   * passing in aParams.mSnapFlags != ScrollSnapFlags::Disabled. Alternatively,
+   * a caller may want to do its own snapping, in which case it should pass
+   * ScrollSnapFlags::Disabled and populate aParams.mTargetIds based on the
+   * result of the snapping.
+   */
+  void ScrollToWithOrigin(nsPoint aScrollPosition, const nsRect* aRange,
+                          ScrollOperationParams&& aParams);
+
+  void CompleteAsyncScroll(
+      const nsPoint& aScrollPosition, const nsRect& aRange,
+      mozilla::UniquePtr<ScrollSnapTargetIds> aSnapTargetIds,
+      ScrollOrigin aOrigin = ScrollOrigin::NotSpecified);
+
+  bool HasPerspective() const { return ChildrenHavePerspective(); }
+  bool HasBgAttachmentLocal() const;
+  mozilla::StyleDirection GetScrolledFrameDir() const;
+
+  // Ask APZ to smooth scroll to |aDestination|.
+  // This method does not clamp the destination; callers should clamp it to
+  // either the layout or the visual scroll range (APZ will happily smooth
+  // scroll to either).
+  void ApzSmoothScrollTo(
+      const nsPoint& aDestination, ScrollOrigin,
+      mozilla::ScrollTriggeredByScript,
+      mozilla::UniquePtr<ScrollSnapTargetIds> aSnapTargetIds);
+
+  // Check whether APZ can scroll in the provided directions, keeping in mind
+  // that APZ currently cannot scroll along axes which are overflow:hidden.
+  bool CanApzScrollInTheseDirections(
+      mozilla::layers::ScrollDirections aDirections);
+
+  // Removes any RefreshDriver observers we might have registered.
+  void RemoveObservers();
+
+ private:
+  // NOTE: On mobile this value might be factoring into overflow:hidden region
+  // in the case of the top level document.
+  nsRect mScrollPort;
+  mozilla::UniquePtr<ScrollSnapTargetIds> mLastSnapTargetIds;
+};
+
+MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(nsHTMLScrollFrame::OverflowState)
+
+#endif /* nsGfxScrollFrame_h___ */