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/* -*- 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 */
/* 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;
enum class StyleScrollbarWidth : uint8_t;
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 {
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::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 CSSPoint = mozilla::CSSPoint;
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;
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() const;
// Return the size of space created by scrollbar-gutter or actual scrollbars,
// assuming that the content is *not* overflowing the container. In other
// words, this space is created by stable scrollbar-gutter or by scrollbars
// due to "overflow: scroll".
nsMargin IntrinsicScrollbarGutterSize() const;
// Compute stable scrollbar-gutter from scrollbar-width and scrollbar-gutter
// properties.
// Note: this method doesn't consider overflow property and the space created
// by the actual scrollbars. That is, if scrollbar-gutter is 'auto', this
// method just returns empty result.
nsMargin ComputeStableScrollbarGutter(
const mozilla::StyleScrollbarWidth& aStyleScrollbarWidth,
const mozilla::StyleScrollbarGutter& aStyleScrollbarGutter) const;
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;
static nscoord GetNonOverlayScrollbarSize(const nsPresContext*,
nsSize GetLayoutSize() const final {
if (mIsUsingMinimumScaleSize) {
return mICBSize;
return mScrollPort.Size();
nsRect GetScrolledRect() const final;
nsRect GetScrollPortRect() const final { return mScrollPort; }
nsPoint GetScrollPosition() const final {
return mScrollPort.TopLeft() - mScrolledFrame->GetPosition();
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 GetRoundedScrollPositionCSSPixels() 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 =
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 |
* @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 {
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,
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 {
bool SmoothScrollVisual(
const nsPoint& aVisualViewportOffset,
mozilla::layers::FrameMetrics::ScrollOffsetUpdateType aUpdateType) final;
bool IsSmoothScroll(mozilla::dom::ScrollBehavior aBehavior) const final;
nsresult GetFrameName(nsAString& aResult) const override;
mozilla::a11y::AccType AccessibleType() override;
nsHTMLScrollFrame(ComputedStyle* aStyle, nsPresContext* aPresContext,
bool aIsRoot)
: nsHTMLScrollFrame(aStyle, aPresContext, kClassID, aIsRoot) {}
nsHTMLScrollFrame(ComputedStyle* aStyle, nsPresContext* aPresContext,
nsIFrame::ClassID aID, bool aIsRoot);
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;
class AsyncScroll;
class AsyncSmoothMSDScroll;
enum class AnonymousContentType {
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();
enum class OverflowState : uint32_t {
None = 0,
Vertical = (1 << 0),
Horizontal = (1 << 1),
OverflowState GetOverflowState() const;
MOZ_CAN_RUN_SCRIPT nsresult FireScrollPortEvent();
void PostScrollEndEvent(bool aDelayed = false);
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:
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; }
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::SnapDestination> GetSnapPointForDestination(
mozilla::ScrollUnit aUnit, ScrollSnapFlags aFlags,
const nsPoint& aStartPos, const nsPoint& aDestination);
Maybe<mozilla::SnapDestination> GetSnapPointForResnap();
bool NeedsResnap();
void SetLastSnapTargetIds(mozilla::UniquePtr<ScrollSnapTargetIds> aId);
void AddScrollPositionListener(nsIScrollPositionListener* aListener) final {
void RemoveScrollPositionListener(
nsIScrollPositionListener* aListener) final {
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(); }
// 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.
nsSize GetSnapportSize() const;
// Schedule the scroll-driven animations.
void ScheduleScrollAnimations();
void TryScheduleScrollAnimations() {
if (!mMayScheduleScrollAnimations) {
mMayScheduleScrollAnimations = false;
CSSPoint GetScrollPositionCSSPixels() const {
return CSSPoint::FromAppUnits(GetScrollPosition());
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;
// True if this scrollable frame was vertically overflowed on the last reflow.
bool mHasVerticalOverflowForDynamicToolbar : 1;
mozilla::layout::ScrollVelocityQueue mVelocityQueue;
class AutoScrollbarRepaintSuppression;
friend class AutoScrollbarRepaintSuppression;
class AutoScrollbarRepaintSuppression {
AutoScrollbarRepaintSuppression(nsHTMLScrollFrame* aFrame,
AutoWeakFrame& aWeakOuter, bool aSuppress)
: mFrame(aFrame),
mOldSuppressValue(aFrame->mSuppressScrollbarRepaints) {
mFrame->mSuppressScrollbarRepaints = aSuppress;
~AutoScrollbarRepaintSuppression() {
if (mWeakOuter.IsAlive()) {
mFrame->mSuppressScrollbarRepaints = mOldSuppressValue;
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, ScrollMode, ScrollOrigin,
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();
// 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;
#endif /* nsGfxScrollFrame_h___ */