Source code

Revision control

Copy as Markdown

Other Tools

/* -*- 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 */
* interface that provides scroll APIs implemented by scrollable frames
#ifndef nsIScrollFrame_h___
#define nsIScrollFrame_h___
#include "nsCoord.h"
#include "mozilla/dom/WindowBinding.h" // for mozilla::dom::ScrollBehavior
#include "mozilla/Maybe.h"
#include "mozilla/ScrollOrigin.h"
#include "mozilla/ScrollPositionUpdate.h"
#include "mozilla/ScrollStyles.h"
#include "mozilla/ScrollTypes.h"
#include "mozilla/gfx/Point.h"
#include "nsIScrollbarMediator.h"
#include "Units.h"
#include "FrameMetrics.h"
class gfxContext;
class nsIScrollPositionListener;
class nsIFrame;
class nsPresContext;
class nsIContent;
namespace mozilla {
class DisplayItemClip;
class nsDisplayListBuilder;
enum class StyleScrollSnapAlignKeyword : uint8_t;
namespace layers {
struct ScrollMetadata;
class Layer;
class WebRenderLayerManager;
} // namespace layers
namespace layout {
class ScrollAnchorContainer;
} // namespace layout
} // namespace mozilla
* Interface for frames that are scrollable. This interface exposes
* APIs for examining scroll state, observing changes to scroll state,
* and triggering scrolling.
class nsIScrollableFrame : public nsIScrollbarMediator {
using CSSIntPoint = mozilla::CSSIntPoint;
using ScrollSnapInfo = mozilla::ScrollSnapInfo;
using ScrollAnchorContainer = mozilla::layout::ScrollAnchorContainer;
using ScrollMode = mozilla::ScrollMode;
using ScrollOrigin = mozilla::ScrollOrigin;
using PhysicalScrollSnapAlign =
* Get the frame for the content that we are scrolling within
* this scrollable frame.
virtual nsIFrame* GetScrolledFrame() const = 0;
* 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.
virtual mozilla::ScrollStyles GetScrollStyles() const = 0;
* Returns whether this scroll frame is for a text control element with no
* scrollbars (for <input>, basically).
virtual bool IsForTextControlWithNoScrollbars() const = 0;
* Returns whether we already have anonymous content nodes for all our needed
* scrollbar parts (or a superset thereof).
virtual bool HasAllNeededScrollbars() const = 0;
* Get the overscroll-behavior styles.
virtual mozilla::layers::OverscrollBehaviorInfo GetOverscrollBehaviorInfo()
const = 0;
* 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.
virtual mozilla::layers::ScrollDirections GetScrollbarVisibility() const = 0;
* Returns the directions in which scrolling is allowed (if the scroll range
* is at least one device pixel in that direction).
mozilla::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.)
virtual mozilla::layers::ScrollDirections
GetAvailableScrollingDirectionsForUserInputEvents() const = 0;
* 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 };
virtual nsMargin GetActualScrollbarSizes(
ScrollbarSizesOptions aOptions = ScrollbarSizesOptions::NONE) const = 0;
* 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.
virtual nsMargin GetDesiredScrollbarSizes() const = 0;
* 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.
virtual nsSize GetLayoutSize() const = 0;
* GetScrolledRect is designed to encapsulate deciding which
* directions of overflow should be reachable by scrolling and which
* should not. Callers should NOT depend on it having any particular
* behavior.
* This should only be called when the scrolled frame has been
* reflowed with the scroll port size given in mScrollPort.
* Currently it allows scrolling down and to the right for
* nsHTMLScrollFrames with LTR directionality, and allows scrolling down and
* to the left for nsHTMLScrollFrames with RTL directionality.
virtual nsRect GetScrolledRect() const = 0;
* 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.
virtual nsRect GetScrollPortRect() const = 0;
* 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.
virtual nsPoint GetScrollPosition() const = 0;
* 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.
virtual nsPoint GetLogicalScrollPosition() const = 0;
* 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.
virtual nsRect GetScrollRange() const = 0;
* Get the size of the view port to use when clamping the scroll
* position.
virtual nsSize GetVisualViewportSize() const = 0;
* 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().
virtual nsPoint GetVisualViewportOffset() const = 0;
* 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.
virtual bool SetVisualViewportOffset(const nsPoint& aOffset,
bool aRepaint) = 0;
* Get the area that must contain the visual viewport offset.
virtual nsRect GetVisualScrollRange() const = 0;
* Like GetVisualScrollRange but also takes into account overflow: hidden.
virtual nsRect GetScrollRangeForUserInputEvents() const = 0;
* Return how much we would try to scroll by in each direction if
* asked to scroll by one "line" vertically and horizontally.
virtual nsSize GetLineScrollAmount() const = 0;
* Return how much we would try to scroll by in each direction if
* asked to scroll by one "page" vertically and horizontally.
virtual nsSize GetPageScrollAmount() const = 0;
* Return scroll-padding value of this frame.
virtual nsMargin GetScrollPadding() const = 0;
* 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.
* 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.
virtual void ScrollTo(
nsPoint aScrollPosition, ScrollMode aMode, const nsRect* aRange = nullptr,
mozilla::ScrollSnapFlags aSnapFlags = mozilla::ScrollSnapFlags::Disabled,
mozilla::ScrollTriggeredByScript aTriggeredByScript =
mozilla::ScrollTriggeredByScript::No) = 0;
* @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.
virtual void ScrollToCSSPixels(const CSSIntPoint& aScrollPosition,
ScrollMode aMode = ScrollMode::Instant) = 0;
* @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).
virtual void ScrollToCSSPixelsForApz(
const mozilla::CSSPoint& aScrollPosition,
mozilla::ScrollSnapTargetIds&& aLastSnapTargetIds) = 0;
* Returns the scroll position in integer CSS pixels, rounded to the nearest
* pixel.
virtual CSSIntPoint GetRoundedScrollPositionCSSPixels() = 0;
* @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.
virtual void ScrollBy(nsIntPoint aDelta, mozilla::ScrollUnit aUnit,
ScrollMode aMode, nsIntPoint* aOverflow = nullptr,
ScrollOrigin aOrigin = ScrollOrigin::NotSpecified,
ScrollMomentum aMomentum = NOT_MOMENTUM,
mozilla::ScrollSnapFlags aSnapFlags =
mozilla::ScrollSnapFlags::Disabled) = 0;
virtual void ScrollByCSSPixels(const CSSIntPoint& aDelta,
ScrollMode aMode = ScrollMode::Instant) = 0;
* 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.
virtual void ScrollSnap() = 0;
* @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.
virtual void ScrollToRestoredPosition() = 0;
* Add a scroll position listener. This listener must be removed
* before it is destroyed.
virtual void AddScrollPositionListener(
nsIScrollPositionListener* aListener) = 0;
* Remove a scroll position listener.
virtual void RemoveScrollPositionListener(
nsIScrollPositionListener* aListener) = 0;
* Internal method used by scrollbars to notify their scrolling
* container of changes.
virtual void CurPosAttributeChanged(nsIContent* aChild) = 0;
* Allows the docshell to request that the scroll frame post an event
* after being restored from history.
NS_IMETHOD PostScrolledAreaEventForCurrentArea() = 0;
* 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.
virtual bool IsScrollingActive() const = 0;
* Returns true if this scroll frame might be scrolled
* asynchronously by the compositor.
virtual bool IsMaybeAsynchronouslyScrolled() const = 0;
* Was the current presentation state for this frame restored from history?
virtual bool DidHistoryRestore() const = 0;
* Clear the flag so that DidHistoryRestore() returns false until the next
* RestoreState call.
* @see nsIStatefulFrame::RestoreState
virtual void ClearDidHistoryRestore() = 0;
* 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.
virtual void MarkEverScrolled() = 0;
* Determine if the passed in rect is nearly visible according to the frame
* visibility heuristics for how close it is to the visible scrollport.
virtual bool IsRectNearlyVisible(const nsRect& aRect) const = 0;
* Expand the given rect taking into account which directions we can scroll
* and how far we want to expand for frame visibility purposes.
virtual nsRect ExpandRectToNearlyVisible(const nsRect& aRect) const = 0;
* 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.
virtual ScrollOrigin LastScrollOrigin() const = 0;
* 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
virtual mozilla::EnumSet<AnimationState> ScrollAnimationState() const = 0;
* Returns the current generation counter for the scrollframe. This counter
* increments every time the scroll position is set.
virtual mozilla::MainThreadScrollGeneration CurrentScrollGeneration()
const = 0;
* The APZ scroll generation associated with the last APZ scroll offset for
* which we processed a repaint request.
virtual mozilla::APZScrollGeneration ScrollGenerationOnApz() const = 0;
* LastScrollDestination returns the destination of the most recently
* requested smooth scroll animation.
virtual nsPoint LastScrollDestination() = 0;
* Returns the list of scroll position updates since the last call to
* NotifyApzTransaction().
virtual nsTArray<mozilla::ScrollPositionUpdate> GetScrollUpdates() const = 0;
* Returns true if the scroll frame has any scroll position updates since
* the last call to NotifyApzTransaction().
virtual bool HasScrollUpdates() const = 0;
enum class InScrollingGesture : bool { No, Yes };
* 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.
virtual void ResetScrollInfoIfNeeded(
const mozilla::MainThreadScrollGeneration& aGeneration,
const mozilla::APZScrollGeneration& aGenerationOnApz,
mozilla::APZScrollAnimationType aAPZScrollAnimationType,
InScrollingGesture aInScrollingGesture) = 0;
* Determine whether it is desirable to be able to asynchronously scroll this
* scroll frame.
virtual bool WantAsyncScroll() const = 0;
* Returns the ScrollMetadata contributed by this frame, if there is one.
virtual mozilla::Maybe<mozilla::layers::ScrollMetadata> ComputeScrollMetadata(
mozilla::layers::WebRenderLayerManager* aLayerManager,
const nsIFrame* aItemFrame,
const nsPoint& aOffsetToReferenceFrame) const = 0;
* Mark the scrollbar frames for reflow.
virtual void MarkScrollbarsDirtyForReflow() const = 0;
* Invalidate the scrollbar after the marks have been changed.
virtual void InvalidateScrollbars() const = 0;
virtual void UpdateScrollbarPosition() = 0;
virtual void SetTransformingByAPZ(bool aTransforming) = 0;
virtual bool IsTransformingByAPZ() const = 0;
* 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.
virtual void SetScrollableByAPZ(bool aScrollable) = 0;
* Notify this scroll frame that it can be zoomed by APZ.
virtual void SetZoomableByAPZ(bool aZoomable) = 0;
* 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.
virtual void SetHasOutOfFlowContentInsideFilter() = 0;
* 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.
virtual bool DecideScrollableLayer(mozilla::nsDisplayListBuilder* aBuilder,
nsRect* aVisibleRect, nsRect* aDirtyRect,
bool aSetBase) = 0;
* 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.
virtual void NotifyApzTransaction() = 0;
* 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)
virtual void NotifyApproximateFrameVisibilityUpdate(
bool aIgnoreDisplayPort) = 0;
* 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.
virtual bool GetDisplayPortAtLastApproximateFrameVisibilityUpdate(
nsRect* aDisplayPort) = 0;
* 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.
virtual void TriggerDisplayPortExpiration() = 0;
* Returns information required to determine where to snap to after a scroll.
virtual ScrollSnapInfo GetScrollSnapInfo() = 0;
virtual void TryResnap() = 0;
* Post a pending re-snap request if the given |aFrame| is one of the snap
* points on the last scroll operation.
virtual void PostPendingResnapIfNeeded(const nsIFrame* aFrame) = 0;
virtual void PostPendingResnap() = 0;
* 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`.
virtual PhysicalScrollSnapAlign GetScrollSnapAlignFor(
const nsIFrame* aFrame) const = 0;
* 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.
virtual bool DragScroll(mozilla::WidgetEvent* aEvent) = 0;
virtual void AsyncScrollbarDragInitiated(
uint64_t aDragBlockId, mozilla::layers::ScrollDirection aDirection) = 0;
virtual void AsyncScrollbarDragRejected() = 0;
* 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.
virtual bool IsRootScrollFrameOfDocument() const = 0;
* Returns the paint sequence number if this scroll frame was the first
* scrollable frame for the paint.
virtual mozilla::Maybe<uint32_t> IsFirstScrollableFrameSequenceNumber()
const = 0;
* Set the paint sequence number for the paint in which this was the first
* scrollable frame that was encountered.
virtual void SetIsFirstScrollableFrameSequenceNumber(
mozilla::Maybe<uint32_t> aValue) = 0;
* Returns the scroll anchor associated with this scrollable frame. This is
* never null.
virtual const ScrollAnchorContainer* Anchor() const = 0;
virtual ScrollAnchorContainer* Anchor() = 0;
virtual bool SmoothScrollVisual(
const nsPoint& aVisualViewportOffset,
mozilla::layers::FrameMetrics::ScrollOffsetUpdateType aUpdateType) = 0;
* Returns true if this scroll frame should perform smooth scroll with the
* given |aBehavior|.
virtual bool IsSmoothScroll(mozilla::dom::ScrollBehavior aBehavior =
mozilla::dom::ScrollBehavior::Auto) const = 0;