layout/generic/nsIScrollableFrame.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 /*
   8  * interface that provides scroll APIs implemented by scrollable frames
   9  */
  10
  11 #ifndef nsIScrollFrame_h___
  12 #define nsIScrollFrame_h___
  13
  14 #include "nsCoord.h"
  15 #include "mozilla/dom/WindowBinding.h"  // for mozilla::dom::ScrollBehavior
  16 #include "mozilla/Maybe.h"
  17 #include "mozilla/ScrollOrigin.h"
  18 #include "mozilla/ScrollPositionUpdate.h"
  19 #include "mozilla/ScrollStyles.h"
  20 #include "mozilla/ScrollTypes.h"
  21 #include "mozilla/gfx/Point.h"
  22 #include "nsIScrollbarMediator.h"
  23 #include "Units.h"
  24 #include "FrameMetrics.h"
  25
  26 class gfxContext;
  27 class nsIScrollPositionListener;
  28 class nsIFrame;
  29 class nsPresContext;
  30 class nsIContent;
  31
  32 namespace mozilla {
  33 class DisplayItemClip;
  34 class nsDisplayListBuilder;
  35 enum class StyleScrollSnapAlignKeyword : uint8_t;
  36
  37 namespace layers {
  38 struct ScrollMetadata;
  39 class Layer;
  40 class WebRenderLayerManager;
  41 }  // namespace layers
  42 namespace layout {
  43 class ScrollAnchorContainer;
  44 }  // namespace layout
  45 }  // namespace mozilla
  46
  47 /**
  48  * Interface for frames that are scrollable. This interface exposes
  49  * APIs for examining scroll state, observing changes to scroll state,
  50  * and triggering scrolling.
  51  */
  52 class nsIScrollableFrame : public nsIScrollbarMediator {
  53  public:
  54   using CSSIntPoint = mozilla::CSSIntPoint;
  55   using ScrollSnapInfo = mozilla::ScrollSnapInfo;
  56   using ScrollAnchorContainer = mozilla::layout::ScrollAnchorContainer;
  57   using ScrollMode = mozilla::ScrollMode;
  58   using ScrollOrigin = mozilla::ScrollOrigin;
  59   using PhysicalScrollSnapAlign =
  60       std::pair<mozilla::StyleScrollSnapAlignKeyword,
  61                 mozilla::StyleScrollSnapAlignKeyword>;
  62
  63   NS_DECL_QUERYFRAME_TARGET(nsIScrollableFrame)
  64
  65   /**
  66    * Get the frame for the content that we are scrolling within
  67    * this scrollable frame.
  68    */
  69   virtual nsIFrame* GetScrolledFrame() const = 0;
  70
  71   /**
  72    * Get the overflow styles (StyleOverflow::Scroll, StyleOverflow::Hidden, or
  73    * StyleOverflow::Auto) governing the horizontal and vertical scrollbars for
  74    * this frame.
  75    *
  76    * This is special because they can be propagated from the <body> element,
  77    * unlike other styles.
  78    */
  79   virtual mozilla::ScrollStyles GetScrollStyles() const = 0;
  80
  81   /**
  82    * Returns whether this scroll frame is for a text control element with no
  83    * scrollbars (for <input>, basically).
  84    */
  85   virtual bool IsForTextControlWithNoScrollbars() const = 0;
  86
  87   /**
  88    * Returns whether we already have anonymous content nodes for all our needed
  89    * scrollbar parts (or a superset thereof).
  90    */
  91   virtual bool HasAllNeededScrollbars() const = 0;
  92
  93   /**
  94    * Get the overscroll-behavior styles.
  95    */
  96   virtual mozilla::layers::OverscrollBehaviorInfo GetOverscrollBehaviorInfo()
  97       const = 0;
  98
  99   /**
 100    * Return the scrollbars which are visible. It's OK to call this during reflow
 101    * of the scrolled contents, in which case it will reflect the current
 102    * assumptions about scrollbar visibility.
 103    */
 104   virtual mozilla::layers::ScrollDirections GetScrollbarVisibility() const = 0;
 105   /**
 106    * Returns the directions in which scrolling is allowed (if the scroll range
 107    * is at least one device pixel in that direction).
 108    */
 109   mozilla::layers::ScrollDirections GetAvailableScrollingDirections() const;
 110   /**
 111    * Returns the directions in which scrolling is allowed when taking into
 112    * account the visual viewport size and overflow hidden. (An (apz) zoomed in
 113    * overflow hidden scrollframe is actually user scrollable.)
 114    */
 115   virtual mozilla::layers::ScrollDirections
 116   GetAvailableScrollingDirectionsForUserInputEvents() const = 0;
 117   /**
 118    * Return the actual sizes of all possible scrollbars. Returns 0 for scrollbar
 119    * positions that don't have a scrollbar or where the scrollbar is not
 120    * visible. Do not call this while this frame's descendants are being
 121    * reflowed, it won't be accurate.
 122    * INCLUDE_VISUAL_VIEWPORT_SCROLLBARS means we include the size of layout
 123    * scrollbars that are only visible to scroll the visual viewport inside the
 124    * layout viewport (ie the layout viewport cannot be scrolled) even though
 125    * there is no layout space set aside for these scrollbars.
 126    */
 127   enum class ScrollbarSizesOptions { NONE, INCLUDE_VISUAL_VIEWPORT_SCROLLBARS };
 128   virtual nsMargin GetActualScrollbarSizes(
 129       ScrollbarSizesOptions aOptions = ScrollbarSizesOptions::NONE) const = 0;
 130   /**
 131    * Return the sizes of all scrollbars assuming that any scrollbars that could
 132    * be visible due to overflowing content, are. This can be called during
 133    * reflow of the scrolled contents.
 134    */
 135   virtual nsMargin GetDesiredScrollbarSizes() const = 0;
 136   /**
 137    * Get the layout size of this frame.
 138    * Note that this is a value which is not expanded by the minimum scale size.
 139    * For scroll frames other than the root content document's scroll frame, this
 140    * value will be the same as GetScrollPortRect().Size().
 141    *
 142    * This value is used for Element.clientWidth and clientHeight.
 143    */
 144   virtual nsSize GetLayoutSize() const = 0;
 145   /**
 146    * GetScrolledRect is designed to encapsulate deciding which
 147    * directions of overflow should be reachable by scrolling and which
 148    * should not.  Callers should NOT depend on it having any particular
 149    * behavior (although nsXULScrollFrame currently does).
 150    *
 151    * This should only be called when the scrolled frame has been
 152    * reflowed with the scroll port size given in mScrollPort.
 153    *
 154    * Currently it allows scrolling down and to the right for
 155    * nsHTMLScrollFrames with LTR directionality and for all
 156    * nsXULScrollFrames, and allows scrolling down and to the left for
 157    * nsHTMLScrollFrames with RTL directionality.
 158    */
 159   virtual nsRect GetScrolledRect() const = 0;
 160   /**
 161    * Get the area of the scrollport relative to the origin of this frame's
 162    * border-box.
 163    * This is the area of this frame minus border and scrollbars.
 164    */
 165   virtual nsRect GetScrollPortRect() const = 0;
 166   /**
 167    * Get the offset of the scrollport origin relative to the scrolled
 168    * frame origin. Typically the position will be non-negative.
 169    * This will always be a multiple of device pixels.
 170    */
 171   virtual nsPoint GetScrollPosition() const = 0;
 172   /**
 173    * As GetScrollPosition(), but uses the top-right as origin for RTL frames.
 174    */
 175   virtual nsPoint GetLogicalScrollPosition() const = 0;
 176
 177   /**
 178    * Get the area that must contain the scroll position. Typically
 179    * (but not always, e.g. for RTL content) x and y will be 0, and
 180    * width or height will be nonzero if the content can be scrolled in
 181    * that direction. Since scroll positions must be a multiple of
 182    * device pixels, the range extrema will also be a multiple of
 183    * device pixels.
 184    */
 185   virtual nsRect GetScrollRange() const = 0;
 186   /**
 187    * Get the size of the view port to use when clamping the scroll
 188    * position.
 189    */
 190   virtual nsSize GetVisualViewportSize() const = 0;
 191   /**
 192    * Returns the offset of the visual viewport relative to
 193    * the origin of the scrolled content. Note that only the RCD-RSF
 194    * has a distinct visual viewport; for other scroll frames, the
 195    * visual viewport always coincides with the layout viewport, and
 196    * consequently the offset this function returns is equal to
 197    * GetScrollPosition().
 198    */
 199   virtual nsPoint GetVisualViewportOffset() const = 0;
 200   /**
 201    * Set the visual viewport offset associated with a root scroll frame. This is
 202    * only valid when called on a root scroll frame and will assert otherwise.
 203    * aRepaint indicates if we need to ask for a main thread paint if this
 204    * changes scrollbar positions or not. For example, if the compositor has
 205    * already put the scrollbars at this position then they don't need to move so
 206    * we can skip the repaint. Returns true if the offset changed and the scroll
 207    * frame is still alive after this call.
 208    */
 209   virtual bool SetVisualViewportOffset(const nsPoint& aOffset,
 210                                        bool aRepaint) = 0;
 211   /**
 212    * Get the area that must contain the visual viewport offset.
 213    */
 214   virtual nsRect GetVisualScrollRange() const = 0;
 215   /**
 216    * Like GetVisualScrollRange but also takes into account overflow: hidden.
 217    */
 218   virtual nsRect GetScrollRangeForUserInputEvents() const = 0;
 219   /**
 220    * Return how much we would try to scroll by in each direction if
 221    * asked to scroll by one "line" vertically and horizontally.
 222    */
 223   virtual nsSize GetLineScrollAmount() const = 0;
 224   /**
 225    * Return how much we would try to scroll by in each direction if
 226    * asked to scroll by one "page" vertically and horizontally.
 227    */
 228   virtual nsSize GetPageScrollAmount() const = 0;
 229
 230   /**
 231    * Return scroll-padding value of this frame.
 232    */
 233   virtual nsMargin GetScrollPadding() const = 0;
 234   /**
 235    * Some platforms (OSX) may generate additional scrolling events even
 236    * after the user has stopped scrolling, simulating a momentum scrolling
 237    * effect resulting from fling gestures.
 238    * SYNTHESIZED_MOMENTUM_EVENT indicates that the scrolling is being requested
 239    * by such a synthesized event and may be ignored if another scroll has
 240    * been started since the last actual user input.
 241    */
 242   enum ScrollMomentum { NOT_MOMENTUM, SYNTHESIZED_MOMENTUM_EVENT };
 243   /**
 244    * @note This method might destroy the frame, pres shell and other objects.
 245    * Clamps aScrollPosition to GetScrollRange and sets the scroll position
 246    * to that value.
 247    * @param aRange If non-null, specifies area which contains aScrollPosition
 248    * and can be used for choosing a performance-optimized scroll position.
 249    * Any point within this area can be chosen.
 250    * The choosen point will be as close as possible to aScrollPosition.
 251    */
 252   virtual void ScrollTo(
 253       nsPoint aScrollPosition, ScrollMode aMode, const nsRect* aRange = nullptr,
 254       mozilla::ScrollSnapFlags aSnapFlags = mozilla::ScrollSnapFlags::Disabled,
 255       mozilla::ScrollTriggeredByScript aTriggeredByScript =
 256           mozilla::ScrollTriggeredByScript::No) = 0;
 257   /**
 258    * @note This method might destroy the frame, pres shell and other objects.
 259    * Scrolls to a particular position in integer CSS pixels.
 260    * Keeps the exact current horizontal or vertical position if the current
 261    * position, rounded to CSS pixels, matches aScrollPosition. If
 262    * aScrollPosition.x/y is different from the current CSS pixel position,
 263    * makes sure we only move in the direction given by the difference.
 264    *
 265    * When aMode is SMOOTH, INSTANT, or NORMAL, GetScrollPositionCSSPixels (the
 266    * scroll position after rounding to CSS pixels) will be exactly
 267    * aScrollPosition at the end of the scroll animation.
 268    *
 269    * When aMode is SMOOTH_MSD, intermediate animation frames may be outside the
 270    * range and / or moving in any direction; GetScrollPositionCSSPixels will be
 271    * exactly aScrollPosition at the end of the scroll animation unless the
 272    * SMOOTH_MSD animation is interrupted.
 273    */
 274   virtual void ScrollToCSSPixels(const CSSIntPoint& aScrollPosition,
 275                                  ScrollMode aMode = ScrollMode::Instant) = 0;
 276   /**
 277    * @note This method might destroy the frame, pres shell and other objects.
 278    * Scrolls to a particular position in float CSS pixels.
 279    * This does not guarantee that GetScrollPositionCSSPixels equals
 280    * aScrollPosition afterward. It tries to scroll as close to
 281    * aScrollPosition as possible while scrolling by an integer
 282    * number of layer pixels (so the operation is fast and looks clean).
 283    */
 284   virtual void ScrollToCSSPixelsForApz(
 285       const mozilla::CSSPoint& aScrollPosition,
 286       mozilla::ScrollSnapTargetIds&& aLastSnapTargetIds) = 0;
 287
 288   /**
 289    * Returns the scroll position in integer CSS pixels, rounded to the nearest
 290    * pixel.
 291    */
 292   virtual CSSIntPoint GetScrollPositionCSSPixels() = 0;
 293   /**
 294    * @note This method might destroy the frame, pres shell and other objects.
 295    * Modifies the current scroll position by aDelta units given by aUnit,
 296    * clamping it to GetScrollRange. If WHOLE is specified as the unit,
 297    * content is scrolled all the way in the direction(s) given by aDelta.
 298    * @param aOverflow if non-null, returns the amount that scrolling
 299    * was clamped by in each direction (how far we moved the scroll position
 300    * to bring it back into the legal range). This is never negative. The
 301    * values are in device pixels.
 302    */
 303   virtual void ScrollBy(nsIntPoint aDelta, mozilla::ScrollUnit aUnit,
 304                         ScrollMode aMode, nsIntPoint* aOverflow = nullptr,
 305                         ScrollOrigin aOrigin = ScrollOrigin::NotSpecified,
 306                         ScrollMomentum aMomentum = NOT_MOMENTUM,
 307                         mozilla::ScrollSnapFlags aSnapFlags =
 308                             mozilla::ScrollSnapFlags::Disabled) = 0;
 309
 310   virtual void ScrollByCSSPixels(const CSSIntPoint& aDelta,
 311                                  ScrollMode aMode = ScrollMode::Instant) = 0;
 312
 313   /**
 314    * Perform scroll snapping, possibly resulting in a smooth scroll to
 315    * maintain the scroll snap position constraints.  Velocity sampled from
 316    * main thread scrolling is used to determine best matching snap point
 317    * when called after a fling gesture on a trackpad or mouse wheel.
 318    */
 319   virtual void ScrollSnap() = 0;
 320
 321   /**
 322    * @note This method might destroy the frame, pres shell and other objects.
 323    * This tells the scroll frame to try scrolling to the scroll
 324    * position that was restored from the history. This must be called
 325    * at least once after state has been restored. It is called by the
 326    * scrolled frame itself during reflow, but sometimes state can be
 327    * restored after reflows are done...
 328    * XXX should we take an aMode parameter here? Currently it's instant.
 329    */
 330   virtual void ScrollToRestoredPosition() = 0;
 331
 332   /**
 333    * Add a scroll position listener. This listener must be removed
 334    * before it is destroyed.
 335    */
 336   virtual void AddScrollPositionListener(
 337       nsIScrollPositionListener* aListener) = 0;
 338   /**
 339    * Remove a scroll position listener.
 340    */
 341   virtual void RemoveScrollPositionListener(
 342       nsIScrollPositionListener* aListener) = 0;
 343
 344   /**
 345    * Internal method used by scrollbars to notify their scrolling
 346    * container of changes.
 347    */
 348   virtual void CurPosAttributeChanged(nsIContent* aChild) = 0;
 349
 350   /**
 351    * Allows the docshell to request that the scroll frame post an event
 352    * after being restored from history.
 353    */
 354   NS_IMETHOD PostScrolledAreaEventForCurrentArea() = 0;
 355
 356   /**
 357    * Returns true if this scrollframe is being "actively scrolled".
 358    * This basically means that we should allocate resources in the
 359    * expectation that scrolling is going to happen.
 360    */
 361   virtual bool IsScrollingActive() const = 0;
 362
 363   /**
 364    * Returns true if this scroll frame might be scrolled
 365    * asynchronously by the compositor.
 366    */
 367   virtual bool IsMaybeAsynchronouslyScrolled() const = 0;
 368
 369   /**
 370    * Was the current presentation state for this frame restored from history?
 371    */
 372   virtual bool DidHistoryRestore() const = 0;
 373   /**
 374    * Clear the flag so that DidHistoryRestore() returns false until the next
 375    * RestoreState call.
 376    * @see nsIStatefulFrame::RestoreState
 377    */
 378   virtual void ClearDidHistoryRestore() = 0;
 379   /**
 380    * Mark the frame as having been scrolled at least once, so that it remains
 381    * active and we can also start storing its scroll position when saving state.
 382    */
 383   virtual void MarkEverScrolled() = 0;
 384   /**
 385    * Determine if the passed in rect is nearly visible according to the frame
 386    * visibility heuristics for how close it is to the visible scrollport.
 387    */
 388   virtual bool IsRectNearlyVisible(const nsRect& aRect) const = 0;
 389   /**
 390    * Expand the given rect taking into account which directions we can scroll
 391    * and how far we want to expand for frame visibility purposes.
 392    */
 393   virtual nsRect ExpandRectToNearlyVisible(const nsRect& aRect) const = 0;
 394   /**
 395    * Returns the origin that triggered the last instant scroll. Will equal
 396    * ScrollOrigin::Apz when the compositor's replica frame metrics includes the
 397    * latest instant scroll.
 398    */
 399   virtual ScrollOrigin LastScrollOrigin() const = 0;
 400
 401   /**
 402    * Gets the async scroll animation state of this scroll frame.
 403    *
 404    * There are five possible kinds that can overlap.
 405    * MainThread means async scroll animated by the main thread.
 406    * APZ scroll animations that are requested from the main thread go through
 407    * three states: 1) pending, when the main thread has recorded that it wants
 408    * apz to do a scroll animation, 2) requested, when the main thread has sent
 409    * the request to the compositor (but it hasn't necessarily arrived yet), and
 410    * 3) in progress, after apz has responded to the main thread that it got the
 411    * request.
 412    * TriggeredByScript means that the async scroll animation was triggered by
 413    * script, e.g. Element.scrollTo().
 414    */
 415   enum class AnimationState {
 416     MainThread,        // mAsyncScroll || mAsyncSmoothMSDScroll
 417     APZPending,        // mScrollUpdates.LastElement() is Smooth or SmoothMsd
 418     APZRequested,      // mApzAnimationRequested
 419     APZInProgress,     // mCurrentAPZScrollAnimationType !=
 420                        // APZScrollAniationType::No
 421     TriggeredByScript  // The animation was triggered with
 422                        // ScrollTriggeredByScript::Yes
 423   };
 424   virtual mozilla::EnumSet<AnimationState> ScrollAnimationState() const = 0;
 425
 426   /**
 427    * Returns the current generation counter for the scrollframe. This counter
 428    * increments every time the scroll position is set.
 429    */
 430   virtual mozilla::MainThreadScrollGeneration CurrentScrollGeneration()
 431       const = 0;
 432   /**
 433    * The APZ scroll generation associated with the last APZ scroll offset for
 434    * which we processed a repaint request.
 435    */
 436   virtual mozilla::APZScrollGeneration ScrollGenerationOnApz() const = 0;
 437   /**
 438    * LastScrollDestination returns the destination of the most recently
 439    * requested smooth scroll animation.
 440    */
 441   virtual nsPoint LastScrollDestination() = 0;
 442   /**
 443    * Returns the list of scroll position updates since the last call to
 444    * NotifyApzTransaction().
 445    */
 446   virtual nsTArray<mozilla::ScrollPositionUpdate> GetScrollUpdates() const = 0;
 447   /**
 448    * Returns true if the scroll frame has any scroll position updates since
 449    * the last call to NotifyApzTransaction().
 450    */
 451   virtual bool HasScrollUpdates() const = 0;
 452
 453   enum class InScrollingGesture : bool { No, Yes };
 454   /**
 455    * Clears the "origin of last scroll" property stored in this frame, if
 456    * the generation counter passed in matches the current scroll generation
 457    * counter, and clears the "origin of last smooth scroll" property if the
 458    * generation counter matches. It also resets whether there's an ongoing apz
 459    * animation.
 460    */
 461   virtual void ResetScrollInfoIfNeeded(
 462       const mozilla::MainThreadScrollGeneration& aGeneration,
 463       const mozilla::APZScrollGeneration& aGenerationOnApz,
 464       mozilla::APZScrollAnimationType aAPZScrollAnimationType,
 465       InScrollingGesture aInScrollingGesture) = 0;
 466   /**
 467    * Determine whether it is desirable to be able to asynchronously scroll this
 468    * scroll frame.
 469    */
 470   virtual bool WantAsyncScroll() const = 0;
 471   /**
 472    * Returns the ScrollMetadata contributed by this frame, if there is one.
 473    */
 474   virtual mozilla::Maybe<mozilla::layers::ScrollMetadata> ComputeScrollMetadata(
 475       mozilla::layers::WebRenderLayerManager* aLayerManager,
 476       const nsIFrame* aItemFrame,
 477       const nsPoint& aOffsetToReferenceFrame) const = 0;
 478
 479   /**
 480    * Mark the scrollbar frames for reflow.
 481    */
 482   virtual void MarkScrollbarsDirtyForReflow() const = 0;
 483
 484   /**
 485    * Invalidate the scrollbar after the marks have been changed.
 486    */
 487   virtual void InvalidateScrollbars() const = 0;
 488
 489   virtual void UpdateScrollbarPosition() = 0;
 490
 491   virtual void SetTransformingByAPZ(bool aTransforming) = 0;
 492   virtual bool IsTransformingByAPZ() const = 0;
 493
 494   /**
 495    * Notify this scroll frame that it can be scrolled by APZ. In particular,
 496    * this is called *after* the APZ code has created an APZC for this scroll
 497    * frame and verified that it is not a scrollinfo layer. Therefore, setting an
 498    * async transform on it is actually user visible.
 499    */
 500   virtual void SetScrollableByAPZ(bool aScrollable) = 0;
 501
 502   /**
 503    * Notify this scroll frame that it can be zoomed by APZ.
 504    */
 505   virtual void SetZoomableByAPZ(bool aZoomable) = 0;
 506
 507   /**
 508    * Mark this scroll frame as having out-of-flow content inside a CSS filter.
 509    * Such content will move incorrectly during async-scrolling; to mitigate
 510    * this, paint skipping is disabled for such scroll frames.
 511    */
 512   virtual void SetHasOutOfFlowContentInsideFilter() = 0;
 513
 514   /**
 515    * Determine if we should build a scrollable layer for this scroll frame and
 516    * return the result. It will also record this result on the scroll frame.
 517    * Pass the visible rect in aVisibleRect. On return it will be set to the
 518    * displayport if there is one.
 519    * Pass the dirty rect in aDirtyRect. On return it will be set to the
 520    * dirty rect inside the displayport (ie the dirty rect that should be used).
 521    * This function will set the display port base rect if aSetBase is true.
 522    * aSetBase is only allowed to be false if there has been a call with it
 523    * set to true before on the same paint.
 524    */
 525   virtual bool DecideScrollableLayer(mozilla::nsDisplayListBuilder* aBuilder,
 526                                      nsRect* aVisibleRect, nsRect* aDirtyRect,
 527                                      bool aSetBase) = 0;
 528
 529   /**
 530    * Notify the scrollframe that the current scroll offset and origin have been
 531    * sent over in a layers transaction.
 532    *
 533    * This sets a flag on the scrollframe that indicates subsequent changes
 534    * to the scroll position by "weaker" origins are permitted to overwrite the
 535    * the scroll origin. Scroll origins that
 536    * nsLayoutUtils::CanScrollOriginClobberApz returns false for are considered
 537    * "weaker" than scroll origins for which that function returns true.
 538    *
 539    * This function must be called for a scrollframe after all calls to
 540    * ComputeScrollMetadata in a layers transaction have been completed.
 541    *
 542    */
 543   virtual void NotifyApzTransaction() = 0;
 544
 545   /**
 546    * Notification that this scroll frame is getting its frame visibility
 547    * updated. aIgnoreDisplayPort indicates that the display port was ignored
 548    * (because there was no suitable base rect)
 549    */
 550   virtual void NotifyApproximateFrameVisibilityUpdate(
 551       bool aIgnoreDisplayPort) = 0;
 552
 553   /**
 554    * Returns true if this scroll frame had a display port at the last frame
 555    * visibility update and fills in aDisplayPort with that displayport. Returns
 556    * false otherwise, and doesn't touch aDisplayPort.
 557    */
 558   virtual bool GetDisplayPortAtLastApproximateFrameVisibilityUpdate(
 559       nsRect* aDisplayPort) = 0;
 560
 561   /**
 562    * This is called when a descendant scrollframe's has its displayport expired.
 563    * This function will check to see if this scrollframe may safely expire its
 564    * own displayport and schedule a timer to do that if it is safe.
 565    */
 566   virtual void TriggerDisplayPortExpiration() = 0;
 567
 568   /**
 569    * Returns information required to determine where to snap to after a scroll.
 570    */
 571   virtual ScrollSnapInfo GetScrollSnapInfo() = 0;
 572
 573   virtual void TryResnap() = 0;
 574   /**
 575    * Post a pending re-snap request if the given |aFrame| is one of the snap
 576    * points on the last scroll operation.
 577    */
 578   virtual void PostPendingResnapIfNeeded(const nsIFrame* aFrame) = 0;
 579   virtual void PostPendingResnap() = 0;
 580
 581   /**
 582    * Returns a pair of the scroll-snap-align property value both on X and Y axes
 583    * for the given |aFrame| considering the scroll-snap-type of this scroll
 584    * container. For example, if the scroll-snap-type is `none`, the pair of
 585    * scroll-snap-align is also `none none`.
 586    */
 587   virtual PhysicalScrollSnapAlign GetScrollSnapAlignFor(
 588       const nsIFrame* aFrame) const = 0;
 589
 590   /**
 591    * Given the drag event aEvent, determine whether the mouse is near the edge
 592    * of the scrollable area, and scroll the view in the direction of that edge
 593    * if so. If scrolling occurred, true is returned. When false is returned, the
 594    * caller should look for an ancestor to scroll.
 595    */
 596   virtual bool DragScroll(mozilla::WidgetEvent* aEvent) = 0;
 597
 598   virtual void AsyncScrollbarDragInitiated(
 599       uint64_t aDragBlockId, mozilla::layers::ScrollDirection aDirection) = 0;
 600   virtual void AsyncScrollbarDragRejected() = 0;
 601
 602   /**
 603    * Returns whether this scroll frame is the root scroll frame of the document
 604    * that it is in. Note that some documents don't have root scroll frames at
 605    * all (ie XUL documents) even though they may contain other scroll frames.
 606    */
 607   virtual bool IsRootScrollFrameOfDocument() const = 0;
 608
 609   /**
 610    * Returns the paint sequence number if this scroll frame was the first
 611    * scrollable frame for the paint.
 612    */
 613   virtual mozilla::Maybe<uint32_t> IsFirstScrollableFrameSequenceNumber()
 614       const = 0;
 615
 616   /**
 617    * Set the paint sequence number for the paint in which this was the first
 618    * scrollable frame that was encountered.
 619    */
 620   virtual void SetIsFirstScrollableFrameSequenceNumber(
 621       mozilla::Maybe<uint32_t> aValue) = 0;
 622
 623   /**
 624    * Returns the scroll anchor associated with this scrollable frame. This is
 625    * never null.
 626    */
 627   virtual const ScrollAnchorContainer* Anchor() const = 0;
 628   virtual ScrollAnchorContainer* Anchor() = 0;
 629
 630   virtual bool SmoothScrollVisual(
 631       const nsPoint& aVisualViewportOffset,
 632       mozilla::layers::FrameMetrics::ScrollOffsetUpdateType aUpdateType) = 0;
 633
 634   /**
 635    * Returns true if this scroll frame should perform smooth scroll with the
 636    * given |aBehavior|.
 637    */
 638   virtual bool IsSmoothScroll(mozilla::dom::ScrollBehavior aBehavior =
 639                                   mozilla::dom::ScrollBehavior::Auto) const = 0;
 640 };
 641
 642 #endif