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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 mozilla_ScrollContainerFrame_h_
#define mozilla_ScrollContainerFrame_h_
#include "FrameMetrics.h"
#include "mozilla/Attributes.h"
#include "mozilla/dom/WindowBinding.h" // for mozilla::dom::ScrollBehavior
#include "mozilla/layout/ScrollAnchorContainer.h"
#include "mozilla/ScrollOrigin.h"
#include "mozilla/ScrollTypes.h"
#include "mozilla/TypedEnumBits.h"
#include "nsContainerFrame.h"
#include "nsExpirationTracker.h"
#include "nsIAnonymousContentCreator.h"
#include "nsIReflowCallback.h"
#include "nsIScrollbarMediator.h"
#include "nsIStatefulFrame.h"
#include "nsQueryFrame.h"
#include "nsThreadUtils.h"
#include "ScrollVelocityQueue.h"
class nsPresContext;
class nsIContent;
class nsAtom;
class nsIScrollPositionListener;
class AutoContainsBlendModeCapturer;
namespace mozilla {
struct nsDisplayListCollection;
class PresShell;
class PresState;
enum class PhysicalAxis : uint8_t;
enum class StyleScrollbarWidth : uint8_t;
class ScrollContainerFrame;
class ScrollPositionUpdate;
struct ScrollReflowInput;
struct ScrollStyles;
struct StyleScrollSnapAlign;
namespace layers {
class Layer;
class WebRenderLayerManager;
} // namespace layers
namespace layout {
class ScrollbarActivity;
} // namespace layout
} // namespace mozilla
mozilla::ScrollContainerFrame* NS_NewScrollContainerFrame(
mozilla::PresShell* aPresShell, mozilla::ComputedStyle* aStyle,
bool aIsRoot);
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 ScrollContainerFrame : public nsContainerFrame,
public nsIScrollbarMediator,
public nsIAnonymousContentCreator,
public nsIReflowCallback,
public nsIStatefulFrame {
using Element = dom::Element;
using ScrollAnchorContainer = layout::ScrollAnchorContainer;
using SnapTargetSet = nsTHashSet<RefPtr<nsIContent>>;
friend ScrollContainerFrame* ::NS_NewScrollContainerFrame(
mozilla::PresShell* aPresShell, ComputedStyle* aStyle, bool aIsRoot);
friend class layout::ScrollAnchorContainer;
void BuildDisplayList(nsDisplayListBuilder* aBuilder,
const nsDisplayListSet& aLists) override;
// 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 StyleScrollbarWidth& aStyleScrollbarWidth,
const StyleScrollbarGutter& aStyleScrollbarGutter) const;
bool GetBorderRadii(const nsSize& aFrameSize, const nsSize& aBorderArea,
nsIFrame::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(OverflowAreas& aOverflowAreas) final;
BaselineSharingGroup GetDefaultBaselineSharingGroup() const override;
nscoord SynthesizeFallbackBaseline(
WritingMode aWM, BaselineSharingGroup aBaselineGroup) const override;
Maybe<nscoord> GetNaturalBaselineBOffset(
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;
ScrollContainerFrame* GetScrollTargetFrame() const final {
return const_cast<ScrollContainerFrame*>(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;
* Get the frame for the content that we are scrolling within
* this scrollable frame.
nsIFrame* GetScrolledFrame() const { return mScrolledFrame; }
* Get the overflow styles (StyleOverflow::Scroll, StyleOverflow::Hidden, or
* StyleOverflow::Auto) governing the horizontal and vertical scrollbars for
* this frame.
* This is special because they can be propagated from the <body> element,
* unlike other styles.
ScrollStyles GetScrollStyles() const;
* Returns whether we already have anonymous content nodes for all our needed
* scrollbar parts (or a superset thereof).
bool HasAllNeededScrollbars() const {
return GetCurrentAnonymousContent().contains(GetNeededAnonymousContent());
* Get the overscroll-behavior styles.
layers::OverscrollBehaviorInfo GetOverscrollBehaviorInfo() const;
* Return the scrollbars which are visible. It's OK to call this during reflow
* of the scrolled contents, in which case it will reflect the current
* assumptions about scrollbar visibility.
layers::ScrollDirections GetScrollbarVisibility() const {
layers::ScrollDirections result;
if (mHasHorizontalScrollbar) {
result += layers::ScrollDirection::eHorizontal;
if (mHasVerticalScrollbar) {
result += layers::ScrollDirection::eVertical;
return result;
* Returns the directions in which scrolling is allowed (if the scroll range
* is at least one device pixel in that direction).
layers::ScrollDirections GetAvailableScrollingDirections() const;
* Returns the directions in which scrolling is allowed when taking into
* account the visual viewport size and overflow hidden. (An (apz) zoomed in
* overflow hidden scrollframe is actually user scrollable.)
layers::ScrollDirections GetAvailableScrollingDirectionsForUserInputEvents()
* Return the actual sizes of all possible scrollbars. Returns 0 for scrollbar
* positions that don't have a scrollbar or where the scrollbar is not
* visible. Do not call this while this frame's descendants are being
* reflowed, it won't be accurate.
* INCLUDE_VISUAL_VIEWPORT_SCROLLBARS means we include the size of layout
* scrollbars that are only visible to scroll the visual viewport inside the
* layout viewport (ie the layout viewport cannot be scrolled) even though
* there is no layout space set aside for these scrollbars.
enum class ScrollbarSizesOptions { NONE, INCLUDE_VISUAL_VIEWPORT_SCROLLBARS };
nsMargin GetActualScrollbarSizes(
ScrollbarSizesOptions aOptions = ScrollbarSizesOptions::NONE) const;
* Return the sizes of all scrollbars assuming that any scrollbars that could
* be visible due to overflowing content, are. This can be called during
* reflow of the scrolled contents.
nsMargin GetDesiredScrollbarSizes() const;
* Get the layout size of this frame.
* Note that this is a value which is not expanded by the minimum scale size.
* For scroll frames other than the root content document's scroll frame, this
* value will be the same as GetScrollPortRect().Size().
* This value is used for Element.clientWidth and clientHeight.
nsSize GetLayoutSize() const {
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
* ScrollContainerFrames with LTR directionality, and allows scrolling down
* and to the left for ScrollContainerFrames with RTL directionality.
nsRect GetScrolledRect() const;
* Get the area of the scrollport relative to the origin of this frame's
* border-box.
* This is the area of this frame minus border and scrollbars.
nsRect GetScrollPortRect() const { return mScrollPort; }
nsRect GetScrollPortRectAccountingForDynamicToolbar() const {
auto rect = mScrollPort;
if (mIsRoot) {
rect.height += PresContext()->GetBimodalDynamicToolbarHeightInAppUnits();
return rect;
nsRect GetScrollPortRectAccountingForMaxDynamicToolbar() const {
auto rect = mScrollPort;
if (mIsRoot) {
rect.height += PresContext()->GetDynamicToolbarMaxHeightInAppUnits();
return rect;
* Get the offset of the scrollport origin relative to the scrolled
* frame origin. Typically the position will be non-negative.
* This will always be a multiple of device pixels.
nsPoint GetScrollPosition() const {
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 {
nsPoint pt;
pt.x = IsPhysicalLTR()
? mScrollPort.x - mScrolledFrame->GetPosition().x
: mScrollPort.XMost() - mScrolledFrame->GetRect().XMost();
pt.y = mScrollPort.y - mScrolledFrame->GetPosition().y;
return pt;
* Get the area that must contain the scroll position. Typically
* (but not always, e.g. for RTL content) x and y will be 0, and
* width or height will be nonzero if the content can be scrolled in
* that direction. Since scroll positions must be a multiple of
* device pixels, the range extrema will also be a multiple of
* device pixels.
nsRect GetScrollRange() const { return GetLayoutScrollRange(); }
* Get the size of the view port to use when clamping the scroll
* position.
nsSize GetVisualViewportSize() const;
* Returns the offset of the visual viewport relative to
* the origin of the scrolled content. Note that only the RCD-RSF
* has a distinct visual viewport; for other scroll frames, the
* visual viewport always coincides with the layout viewport, and
* consequently the offset this function returns is equal to
* GetScrollPosition().
nsPoint GetVisualViewportOffset() const;
* Set the visual viewport offset associated with a root scroll frame. This is
* only valid when called on a root scroll frame and will assert otherwise.
* aRepaint indicates if we need to ask for a main thread paint if this
* changes scrollbar positions or not. For example, if the compositor has
* already put the scrollbars at this position then they don't need to move so
* we can skip the repaint. Returns true if the offset changed and the scroll
* frame is still alive after this call.
bool SetVisualViewportOffset(const nsPoint& aOffset, bool aRepaint);
* Get the area that must contain the visual viewport offset.
nsRect GetVisualScrollRange() const;
* Like GetVisualScrollRange but also takes into account overflow: hidden.
nsRect GetScrollRangeForUserInputEvents() const;
* Return how much we would try to scroll by in each direction if
* asked to scroll by one "line" vertically and horizontally.
nsSize GetLineScrollAmount() const;
* Return how much we would try to scroll by in each direction if
* asked to scroll by one "page" vertically and horizontally.
nsSize GetPageScrollAmount() const;
* Return scroll-padding value of this frame.
nsMargin GetScrollPadding() const;
* @note This method might destroy the frame, pres shell and other objects.
* Clamps aScrollPosition to GetScrollRange and sets the scroll position
* to that value.
* @param aRange If non-null, specifies area which contains aScrollPosition
* and can be used for choosing a performance-optimized scroll position.
* Any point within this area can be chosen.
* The choosen point will be as close as possible to aScrollPosition.
void ScrollTo(nsPoint aScrollPosition, ScrollMode aMode,
const nsRect* aRange = nullptr,
ScrollSnapFlags aSnapFlags = ScrollSnapFlags::Disabled,
ScrollTriggeredByScript aTriggeredByScript =
ScrollTriggeredByScript::No) {
return ScrollToInternal(aScrollPosition, aMode, ScrollOrigin::Other, aRange,
aSnapFlags, aTriggeredByScript);
* @note This method might destroy the frame, pres shell and other objects.
* Scrolls to a particular position in integer CSS pixels.
* Keeps the exact current horizontal or vertical position if the current
* position, rounded to CSS pixels, matches aScrollPosition. If
* aScrollPosition.x/y is different from the current CSS pixel position,
* makes sure we only move in the direction given by the difference.
* When aMode is SMOOTH, INSTANT, or NORMAL, GetRoundedScrollPositionCSSPixels
* (the scroll position after rounding to CSS pixels) will be exactly
* aScrollPosition at the end of the scroll animation.
* When aMode is SMOOTH_MSD, intermediate animation frames may be outside the
* range and / or moving in any direction; GetRoundedScrollPositionCSSPixels
* will be exactly aScrollPosition at the end of the scroll animation unless
* the SMOOTH_MSD animation is interrupted.
void ScrollToCSSPixels(const CSSIntPoint& aScrollPosition,
ScrollMode aMode = ScrollMode::Instant);
* @note This method might destroy the frame, pres shell and other objects.
* Scrolls to a particular position in float CSS pixels.
* This does not guarantee that GetRoundedScrollPositionCSSPixels equals
* aScrollPosition afterward. It tries to scroll as close to
* aScrollPosition as possible while scrolling by an integer
* number of layer pixels (so the operation is fast and looks clean).
void ScrollToCSSPixelsForApz(const CSSPoint& aScrollPosition,
ScrollSnapTargetIds&& aLastSnapTargetIds);
* Returns the scroll position in integer CSS pixels, rounded to the nearest
* pixel.
CSSIntPoint GetRoundedScrollPositionCSSPixels();
* Some platforms (OSX) may generate additional scrolling events even
* after the user has stopped scrolling, simulating a momentum scrolling
* effect resulting from fling gestures.
* SYNTHESIZED_MOMENTUM_EVENT indicates that the scrolling is being requested
* by such a synthesized event and may be ignored if another scroll has
* been started since the last actual user input.
* @note This method might destroy the frame, pres shell and other objects.
* Modifies the current scroll position by aDelta units given by aUnit,
* clamping it to GetScrollRange. If WHOLE is specified as the unit,
* content is scrolled all the way in the direction(s) given by aDelta.
* @param aOverflow if non-null, returns the amount that scrolling
* was clamped by in each direction (how far we moved the scroll position
* to bring it back into the legal range). This is never negative. The
* values are in device pixels.
void ScrollBy(nsIntPoint aDelta, ScrollUnit aUnit, ScrollMode aMode,
nsIntPoint* aOverflow = nullptr,
ScrollOrigin aOrigin = ScrollOrigin::NotSpecified,
ScrollMomentum aMomentum = NOT_MOMENTUM,
ScrollSnapFlags aSnapFlags = ScrollSnapFlags::Disabled);
void ScrollByCSSPixels(const CSSIntPoint& aDelta,
ScrollMode aMode = ScrollMode::Instant) {
return ScrollByCSSPixelsInternal(aDelta, aMode);
* Perform scroll snapping, possibly resulting in a smooth scroll to
* maintain the scroll snap position constraints. Velocity sampled from
* main thread scrolling is used to determine best matching snap point
* when called after a fling gesture on a trackpad or mouse wheel.
void ScrollSnap() { return ScrollSnap(ScrollMode::SmoothMsd); }
* @note This method might destroy the frame, pres shell and other objects.
* This tells the scroll frame to try scrolling to the scroll
* position that was restored from the history. This must be called
* at least once after state has been restored. It is called by the
* scrolled frame itself during reflow, but sometimes state can be
* restored after reflows are done...
* XXX should we take an aMode parameter here? Currently it's instant.
void ScrollToRestoredPosition();
* Add a scroll position listener. This listener must be removed
* before it is destroyed.
void AddScrollPositionListener(nsIScrollPositionListener* aListener) {
* Remove a scroll position listener.
void RemoveScrollPositionListener(nsIScrollPositionListener* aListener) {
* @note This method might destroy the frame, pres shell and other objects.
* Internal method used by scrollbars to notify their scrolling
* container of changes.
void CurPosAttributeChanged(nsIContent* aChild) {
return CurPosAttributeChangedInternal(aChild);
* Allows the docshell to request that the scroll frame post an event
* after being restored from history.
NS_IMETHOD PostScrolledAreaEventForCurrentArea() final {
return NS_OK;
* Returns true if this scrollframe is being "actively scrolled".
* This basically means that we should allocate resources in the
* expectation that scrolling is going to happen.
bool IsScrollingActive() const;
* Returns true if this scroll frame might be scrolled
* asynchronously by the compositor.
bool IsMaybeAsynchronouslyScrolled() const {
// If this is true, then we'll build an ASR, and that's what we want
// to know I think.
return mWillBuildScrollableLayer;
* Was the current presentation state for this frame restored from history?
bool DidHistoryRestore() const { return mDidHistoryRestore; }
* Clear the flag so that DidHistoryRestore() returns false until the next
* RestoreState call.
* @see nsIStatefulFrame::RestoreState
void ClearDidHistoryRestore() { mDidHistoryRestore = false; }
* Mark the frame as having been scrolled at least once, so that it remains
* active and we can also start storing its scroll position when saving state.
void MarkEverScrolled();
* Determine if the passed in rect is nearly visible according to the frame
* visibility heuristics for how close it is to the visible scrollport.
bool IsRectNearlyVisible(const nsRect& aRect) const;
* Expand the given rect taking into account which directions we can scroll
* and how far we want to expand for frame visibility purposes.
nsRect ExpandRectToNearlyVisible(const nsRect& aRect) const;
* Returns the origin that triggered the last instant scroll. Will equal
* ScrollOrigin::Apz when the compositor's replica frame metrics includes the
* latest instant scroll.
ScrollOrigin LastScrollOrigin() const { return mLastScrollOrigin; }
* Gets the async scroll animation state of this scroll frame.
* There are five possible kinds that can overlap.
* MainThread means async scroll animated by the main thread.
* APZ scroll animations that are requested from the main thread go through
* three states: 1) pending, when the main thread has recorded that it wants
* apz to do a scroll animation, 2) requested, when the main thread has sent
* the request to the compositor (but it hasn't necessarily arrived yet), and
* 3) in progress, after apz has responded to the main thread that it got the
* request.
* TriggeredByScript means that the async scroll animation was triggered by
* script, e.g. Element.scrollTo().
enum class AnimationState {
MainThread, // mAsyncScroll || mAsyncSmoothMSDScroll
APZPending, // mScrollUpdates.LastElement() is Smooth or SmoothMsd
APZRequested, // mApzAnimationRequested
APZInProgress, // mCurrentAPZScrollAnimationType !=
// APZScrollAniationType::No
TriggeredByScript // The animation was triggered with
// ScrollTriggeredByScript::Yes
EnumSet<AnimationState> ScrollAnimationState() const;
* Returns the current generation counter for the scrollframe. This counter
* increments every time the scroll position is set.
MainThreadScrollGeneration CurrentScrollGeneration() const {
return mScrollGeneration;
* The APZ scroll generation associated with the last APZ scroll offset for
* which we processed a repaint request.
APZScrollGeneration ScrollGenerationOnApz() const {
return mScrollGenerationOnApz;
* LastScrollDestination returns the destination of the most recently
* requested smooth scroll animation.
nsPoint LastScrollDestination() { return mDestination; }
* Returns the list of scroll position updates since the last call to
* NotifyApzTransaction().
nsTArray<ScrollPositionUpdate> GetScrollUpdates() const;
* Returns true if the scroll frame has any scroll position updates since
* the last call to NotifyApzTransaction().
bool HasScrollUpdates() const { return !mScrollUpdates.IsEmpty(); }
* Clears the "origin of last scroll" property stored in this frame, if
* the generation counter passed in matches the current scroll generation
* counter, and clears the "origin of last smooth scroll" property if the
* generation counter matches. It also resets whether there's an ongoing apz
* animation.
enum class InScrollingGesture : bool { No, Yes };
void ResetScrollInfoIfNeeded(const MainThreadScrollGeneration& aGeneration,
const APZScrollGeneration& aGenerationOnApz,
APZScrollAnimationType aAPZScrollAnimationType,
InScrollingGesture aInScrollingGesture);
* Determine whether it is desirable to be able to asynchronously scroll this
* scroll frame.
bool WantAsyncScroll() const;
* Returns the ScrollMetadata contributed by this frame, if there is one.
Maybe<layers::ScrollMetadata> ComputeScrollMetadata(
layers::WebRenderLayerManager* aLayerManager, const nsIFrame* aItemFrame,
const nsPoint& aOffsetToReferenceFrame) const;
* Mark the scrollbar frames for reflow.
void MarkScrollbarsDirtyForReflow() const;
* Invalidate the scrollbar after the marks have been changed.
void InvalidateScrollbars() const;
* @note This method might destroy the frame, pres shell and other objects.
* Update scrollbar curpos attributes to reflect current scroll position
void UpdateScrollbarPosition();
void SetTransformingByAPZ(bool aTransforming);
bool IsTransformingByAPZ() const { return mTransformingByAPZ; }
* Notify this scroll frame that it can be scrolled by APZ. In particular,
* this is called *after* the APZ code has created an APZC for this scroll
* frame and verified that it is not a scrollinfo layer. Therefore, setting an
* async transform on it is actually user visible.
void SetScrollableByAPZ(bool aScrollable);
* Notify this scroll frame that it can be zoomed by APZ.
void SetZoomableByAPZ(bool aZoomable);
* Mark this scroll frame as having out-of-flow content inside a CSS filter.
* Such content will move incorrectly during async-scrolling; to mitigate
* this, paint skipping is disabled for such scroll frames.
void SetHasOutOfFlowContentInsideFilter();
* Determine if we should build a scrollable layer for this scroll frame and
* return the result. It will also record this result on the scroll frame.
* Pass the visible rect in aVisibleRect. On return it will be set to the
* displayport if there is one.
* Pass the dirty rect in aDirtyRect. On return it will be set to the
* dirty rect inside the displayport (ie the dirty rect that should be used).
* This function will set the display port base rect if aSetBase is true.
* aSetBase is only allowed to be false if there has been a call with it
* set to true before on the same paint.
bool DecideScrollableLayer(nsDisplayListBuilder* aBuilder,
nsRect* aVisibleRect, nsRect* aDirtyRect,
bool aSetBase) {
return DecideScrollableLayer(aBuilder, aVisibleRect, aDirtyRect, aSetBase,
* Notify the scrollframe that the current scroll offset and origin have been
* sent over in a layers transaction.
* This sets a flag on the scrollframe that indicates subsequent changes
* to the scroll position by "weaker" origins are permitted to overwrite the
* the scroll origin. Scroll origins that
* nsLayoutUtils::CanScrollOriginClobberApz returns false for are considered
* "weaker" than scroll origins for which that function returns true.
* This function must be called for a scrollframe after all calls to
* ComputeScrollMetadata in a layers transaction have been completed.
void NotifyApzTransaction();
* Notification that this scroll frame is getting its frame visibility
* updated. aIgnoreDisplayPort indicates that the display port was ignored
* (because there was no suitable base rect)
void NotifyApproximateFrameVisibilityUpdate(bool aIgnoreDisplayPort);
* Returns true if this scroll frame had a display port at the last frame
* visibility update and fills in aDisplayPort with that displayport. Returns
* false otherwise, and doesn't touch aDisplayPort.
bool GetDisplayPortAtLastApproximateFrameVisibilityUpdate(
nsRect* aDisplayPort);
* This is called when a descendant scrollframe's has its displayport expired.
* This function will check to see if this scrollframe may safely expire its
* own displayport and schedule a timer to do that if it is safe.
void TriggerDisplayPortExpiration();
* Returns information required to determine where to snap to after a scroll.
ScrollSnapInfo GetScrollSnapInfo();
void TryResnap();
* Post a pending re-snap request if the given |aFrame| is one of the snap
* points on the last scroll operation.
void PostPendingResnapIfNeeded(const nsIFrame* aFrame);
void PostPendingResnap();
* Returns a pair of the scroll-snap-align property value both on X and Y axes
* for the given |aFrame| considering the scroll-snap-type of this scroll
* container. For example, if the scroll-snap-type is `none`, the pair of
* scroll-snap-align is also `none none`.
using PhysicalScrollSnapAlign =
std::pair<StyleScrollSnapAlignKeyword, StyleScrollSnapAlignKeyword>;
PhysicalScrollSnapAlign GetScrollSnapAlignFor(const nsIFrame* aFrame) const;
* Given the drag event aEvent, determine whether the mouse is near the edge
* of the scrollable area, and scroll the view in the direction of that edge
* if so. If scrolling occurred, true is returned. When false is returned, the
* caller should look for an ancestor to scroll.
bool DragScroll(WidgetEvent* aEvent);
void AsyncScrollbarDragInitiated(uint64_t aDragBlockId,
layers::ScrollDirection aDirection);
void AsyncScrollbarDragRejected();
* Returns whether this scroll frame is the root scroll frame of the document
* that it is in. Note that some documents don't have root scroll frames at
* all (ie XUL documents) even though they may contain other scroll frames.
bool IsRootScrollFrameOfDocument() const { return mIsRoot; }
* Returns the paint sequence number if this scroll frame was the first
* scrollable frame for the paint.
Maybe<uint32_t> IsFirstScrollableFrameSequenceNumber() const {
return mIsFirstScrollableFrameSequenceNumber;
* Set the paint sequence number for the paint in which this was the first
* scrollable frame that was encountered.
void SetIsFirstScrollableFrameSequenceNumber(Maybe<uint32_t> aValue) {
mIsFirstScrollableFrameSequenceNumber = aValue;
* Returns the scroll anchor associated with this scrollable frame. This is
* never null.
const ScrollAnchorContainer* Anchor() const { return &mAnchor; }
ScrollAnchorContainer* Anchor() { return &mAnchor; }
bool SmoothScrollVisual(
const nsPoint& aVisualViewportOffset,
layers::FrameMetrics::ScrollOffsetUpdateType aUpdateType);
* Returns true if this scroll frame should perform smooth scroll with the
* given |aBehavior|.
bool IsSmoothScroll(
dom::ScrollBehavior aBehavior = dom::ScrollBehavior::Auto) const;
static nscoord GetNonOverlayScrollbarSize(const nsPresContext*,
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 |
// nsIReflowCallback
bool ReflowFinished() final;
void ReflowCallbackCanceled() final;
// nsIStatefulFrame
UniquePtr<PresState> SaveState() final;
NS_IMETHOD RestoreState(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, 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;
// Return the scrolled frame.
void AppendDirectlyOwnedAnonBoxes(nsTArray<OwnedAnonBox>& aResult) final {
nsresult GetFrameName(nsAString& aResult) const override;
a11y::AccType AccessibleType() override;
static void AsyncScrollCallback(ScrollContainerFrame* aInstance,
TimeStamp aTime);
static void AsyncSmoothMSDScrollCallback(ScrollContainerFrame* aInstance,
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<SnapDestination> GetSnapPointForDestination(
ScrollUnit aUnit, ScrollSnapFlags aFlags, const nsPoint& aStartPos,
const nsPoint& aDestination);
Maybe<SnapDestination> GetSnapPointForResnap();
bool NeedsResnap();
void SetLastSnapTargetIds(UniquePtr<ScrollSnapTargetIds> aId);
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
* ScrollContainerFrames with LTR directionality, and allows scrolling down
* and to the left for ScrollContainerFrames with RTL directionality.
nsRect GetUnsnappedScrolledRectInternal(const nsRect& aScrolledOverflowArea,
const nsSize& aScrollPortSize) const;
bool IsPhysicalLTR() const { return GetWritingMode().IsPhysicalLTR(); }
bool IsBidiLTR() const { return GetWritingMode().IsBidiLTR(); }
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);
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(dom::NodeInfo* aNodeInfo,
bool aVertical,
AnonymousContentKey& aKey);
void AppendScrollUpdate(const ScrollPositionUpdate& aUpdate);
ScrollContainerFrame(ComputedStyle* aStyle, nsPresContext* aPresContext,
bool aIsRoot)
: ScrollContainerFrame(aStyle, aPresContext, kClassID, aIsRoot) {}
ScrollContainerFrame(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;
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);
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,
layers::ScrollDirection aDirection);
void LayoutScrollbars(ScrollReflowInput& aState,
const nsRect& aInsideBorderArea,
const nsRect& aOldScrollPort);
void LayoutScrollbarPartAtRect(const ScrollReflowInput&,
ReflowInput& aKidReflowInput, const nsRect&);
* 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;
PhysicalAxes GetOverflowAxes() 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*, nsDisplayListCollection&, bool aCreateAsyncZoom,
AutoContainsBlendModeCapturer* aAsyncZoomBlendCapture,
const nsRect& aAsyncZoomClipRect, nscoord* aRadii);
void AppendScrollPartsTo(nsDisplayListBuilder* aBuilder,
const nsDisplayListSet& aLists, bool aCreateLayer,
bool aPositioned);
* @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(ScrollMode aMode);
void ScrollSnap(const nsPoint& aDestination,
ScrollMode aMode = ScrollMode::SmoothMsd);
bool HasPendingScrollRestoration() const {
return mRestorePos != nsPoint(-1, -1);
bool IsProcessingScrollEvent() const { return mProcessingScrollEvent; }
class AutoScrollbarRepaintSuppression;
friend class AutoScrollbarRepaintSuppression;
class AutoScrollbarRepaintSuppression {
AutoScrollbarRepaintSuppression(ScrollContainerFrame* aFrame,
AutoWeakFrame& aWeakOuter, bool aSuppress)
: mFrame(aFrame),
mOldSuppressValue(aFrame->mSuppressScrollbarRepaints) {
mFrame->mSuppressScrollbarRepaints = aSuppress;
~AutoScrollbarRepaintSuppression() {
if (mWeakOuter.IsAlive()) {
mFrame->mSuppressScrollbarRepaints = mOldSuppressValue;
ScrollContainerFrame* 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& aStartPosition, const nsRect& aRange,
UniquePtr<ScrollSnapTargetIds> aSnapTargetIds,
ScrollOrigin aOrigin = ScrollOrigin::NotSpecified);
bool HasPerspective() const { return ChildrenHavePerspective(); }
bool HasBgAttachmentLocal() const;
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,
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(layers::ScrollDirections aDirections);
// Removes any RefreshDriver observers we might have registered.
void RemoveObservers();
class AsyncScroll;
class AsyncSmoothMSDScroll;
class AutoMinimumScaleSizeChangeDetector;
enum class AnonymousContentType {
EnumSet<AnonymousContentType> GetNeededAnonymousContent() const;
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();
// 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());
static void RemoveDisplayPortCallback(nsITimer* aTimer, void* aClosure);
// 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<layout::ScrollbarActivity> mScrollbarActivity;
nsTArray<nsIScrollPositionListener*> mListeners;
ScrollOrigin mLastScrollOrigin;
Maybe<nsPoint> mApzSmoothScrollDestination;
MainThreadScrollGeneration mScrollGeneration;
APZScrollGeneration mScrollGenerationOnApz;
nsTArray<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;
layers::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;
layout::ScrollVelocityQueue mVelocityQueue;
// NOTE: On mobile this value might be factoring into overflow:hidden region
// in the case of the top level document.
nsRect mScrollPort;
UniquePtr<ScrollSnapTargetIds> mLastSnapTargetIds;
} // namespace mozilla
#endif /* mozilla_ScrollContainerFrame_h_ */