gecko-dev/layout/generic/nsIScrollableFrame.h

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/*
* interface that provides scroll APIs implemented by scrollable frames
*/
#ifndef nsIScrollFrame_h___
#define nsIScrollFrame_h___
#include "nsCoord.h"
#include "DisplayItemClip.h"
#include "ScrollbarStyles.h"
#include "mozilla/Maybe.h"
#include "mozilla/gfx/Point.h"
#include "nsIScrollbarMediator.h"
#include "Units.h"
#include "FrameMetrics.h"
#define NS_DEFAULT_VERTICAL_SCROLL_DISTANCE 3
#define NS_DEFAULT_HORIZONTAL_SCROLL_DISTANCE 5
class nsBoxLayoutState;
class nsIScrollPositionListener;
class nsIFrame;
class nsPresContext;
class nsIContent;
class nsRenderingContext;
class nsIAtom;
class nsDisplayListBuilder;
namespace mozilla {
struct ContainerLayerParameters;
namespace layers {
class Layer;
} // namespace layers
} // 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 {
public:
typedef mozilla::CSSIntPoint CSSIntPoint;
typedef mozilla::ContainerLayerParameters ContainerLayerParameters;
typedef mozilla::layers::FrameMetrics FrameMetrics;
typedef mozilla::layers::ScrollSnapInfo ScrollSnapInfo;
NS_DECL_QUERYFRAME_TARGET(nsIScrollableFrame)
/**
* Get the frame for the content that we are scrolling within
* this scrollable frame.
*/
virtual nsIFrame* GetScrolledFrame() const = 0;
/**
* Get the styles (NS_STYLE_OVERFLOW_SCROLL, NS_STYLE_OVERFLOW_HIDDEN,
* or NS_STYLE_OVERFLOW_AUTO) governing the horizontal and vertical
* scrollbars for this frame.
*/
virtual mozilla::ScrollbarStyles GetScrollbarStyles() const = 0;
enum { HORIZONTAL = 0x01, VERTICAL = 0x02 };
/**
* 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 uint32_t GetScrollbarVisibility() const = 0;
/**
* Returns the directions in which scrolling is perceived to be allowed.
* A direction is perceived to be allowed if there is a visible scrollbar
* for that direction or if the scroll range is at least one device pixel.
*/
uint32_t GetPerceivedScrollingDirections() const;
/**
* 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.
*/
virtual nsMargin GetActualScrollbarSizes() 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(nsBoxLayoutState* aState) = 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(nsPresContext* aPresContext,
nsRenderingContext* aRC) = 0;
/**
* Return the width for non-disappearing scrollbars.
*/
virtual nscoord
GetNondisappearingScrollbarWidth(nsPresContext* aPresContext,
nsRenderingContext* aRC,
mozilla::WritingMode aWM) = 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 (although nsXULScrollFrame currently does).
*
* 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 for all
* nsXULScrollFrames, 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;
/**
* As GetScrollPosition(), but uses the top-right as origin for RTL frames.
*/
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 scroll port to use when clamping the scroll
* position.
*/
virtual nsSize GetScrollPositionClampingScrollPortSize() 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;
/**
* When a scroll operation is requested, we ask for instant, smooth,
* smooth msd, or normal scrolling.
*
* SMOOTH scrolls have a symmetrical acceleration and deceleration curve
* modeled with a set of splines that guarantee that the destination will be
* reached over a fixed time interval. SMOOTH will only be smooth if smooth
* scrolling is actually enabled. This behavior is utilized by keyboard and
* mouse wheel scrolling events.
*
* SMOOTH_MSD implements a physically based model that approximates the
* behavior of a mass-spring-damper system. SMOOTH_MSD scrolls have a
* non-symmetrical acceleration and deceleration curve, can potentially
* overshoot the destination on intermediate frames, and complete over a
* variable time interval. SMOOTH_MSD will only be smooth if cssom-view
* smooth-scrolling is enabled.
*
* INSTANT is always synchronous, NORMAL can be asynchronous.
*
* If an INSTANT scroll request happens while a SMOOTH or async scroll is
* already in progress, the async scroll is interrupted and we instantly
* scroll to the destination.
*
* If an INSTANT or SMOOTH scroll request happens while a SMOOTH_MSD scroll
* is already in progress, the SMOOTH_MSD scroll is interrupted without
* first scrolling to the destination.
*/
enum ScrollMode { INSTANT, SMOOTH, SMOOTH_MSD, NORMAL };
/**
* 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.
*/
enum ScrollMomentum { NOT_MOMENTUM, SYNTHESIZED_MOMENTUM_EVENT };
/**
* @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,
nsIScrollbarMediator::ScrollSnapMode aSnap
= nsIScrollbarMediator::DISABLE_SNAP) = 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, GetScrollPositionCSSPixels (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; GetScrollPositionCSSPixels will be
* exactly aScrollPosition at the end of the scroll animation unless the
* SMOOTH_MSD animation is interrupted.
*/
virtual void ScrollToCSSPixels(const CSSIntPoint& aScrollPosition,
nsIScrollableFrame::ScrollMode aMode
= nsIScrollableFrame::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 GetScrollPositionCSSPixels 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 ScrollToCSSPixelsApproximate(const mozilla::CSSPoint& aScrollPosition,
nsIAtom *aOrigin = nullptr) = 0;
/**
* Returns the scroll position in integer CSS pixels, rounded to the nearest
* pixel.
*/
virtual CSSIntPoint GetScrollPositionCSSPixels() = 0;
/**
* When scrolling by a relative amount, we can choose various units.
*/
enum ScrollUnit { DEVICE_PIXELS, LINES, PAGES, WHOLE };
/**
* @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, ScrollUnit aUnit, ScrollMode aMode,
nsIntPoint* aOverflow = nullptr,
nsIAtom* aOrigin = nullptr,
ScrollMomentum aMomentum = NOT_MOMENTUM,
nsIScrollbarMediator::ScrollSnapMode aSnap
= nsIScrollbarMediator::DISABLE_SNAP) = 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(nsDisplayListBuilder* aBuilder) = 0;
/**
* Returns true if the scrollframe is currently processing an async
* or smooth scroll.
*/
virtual bool IsProcessingAsyncScroll() = 0;
/**
* Call this when the layer(s) induced by active scrolling are being
* completely redrawn.
*/
virtual void ResetScrollPositionForLayerPixelAlignment() = 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;
/**
* 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) = 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
* nsGkAtoms::apz when the compositor's replica frame metrics includes the
* latest instant scroll.
*/
virtual nsIAtom* LastScrollOrigin() = 0;
/**
* Sets a flag on the scrollframe that indicates the current scroll origin
* has been sent over in a layers transaction, and 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.
*/
virtual void AllowScrollOriginDowngrade() = 0;
/**
* Returns the origin that triggered the last smooth scroll.
* Will equal nsGkAtoms::apz when the compositor's replica frame
* metrics includes the latest smooth scroll. The compositor will always
* perform an instant scroll prior to instantiating any smooth scrolls
* if LastScrollOrigin and LastSmoothScrollOrigin indicate that
* an instant scroll and a smooth scroll have occurred since the last
* replication of the frame metrics.
*
* This is set to nullptr to when the compositor thread acknowledges that
* the smooth scroll has been started. If the smooth scroll has been stomped
* by an instant scroll before the smooth scroll could be started by the
* compositor, this is set to nullptr to clear the smooth scroll.
*/
virtual nsIAtom* LastSmoothScrollOrigin() = 0;
/**
* Returns the current generation counter for the scroll. This counter
* increments every time the scroll position is set.
*/
virtual uint32_t CurrentScrollGeneration() = 0;
/**
* LastScrollDestination returns the destination of the most recently
* requested smooth scroll animation.
*/
virtual nsPoint LastScrollDestination() = 0;
/**
* Clears the "origin of last scroll" property stored in this frame, if
* the generation counter passed in matches the current scroll generation
* counter.
*/
virtual void ResetScrollInfoIfGeneration(uint32_t aGeneration) = 0;
/**
* Determine whether it is desirable to be able to asynchronously scroll this
* scroll frame.
*/
virtual bool WantAsyncScroll() const = 0;
/**
* aLayer's animated geometry root is this frame. If there needs to be a
* ScrollMetadata contributed by this frame, append it to aOutput.
*/
virtual mozilla::Maybe<mozilla::layers::ScrollMetadata> ComputeScrollMetadata(
mozilla::layers::Layer* aLayer,
nsIFrame* aContainerReferenceFrame,
const ContainerLayerParameters& aParameters,
const mozilla::DisplayItemClip* aClip) const = 0;
/**
* If this scroll frame is ignoring viewporting clipping
*/
virtual bool IsIgnoringViewportClipping() const = 0;
/**
* Mark the scrollbar frames for reflow.
*/
virtual void MarkScrollbarsDirtyForReflow() const = 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;
/**
* Whether or not this frame uses containerful scrolling.
*/
virtual bool UsesContainerScrolling() const = 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 dirty rect in aDirtyRect. On return it will be set to the
* displayport if there is one (ie the dirty rect that should be used).
* This function may create a display port where one did not exist before if
* aAllowCreateDisplayPort is true. It 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(nsDisplayListBuilder* aBuilder,
nsRect* aDirtyRect,
bool aAllowCreateDisplayPort) = 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() 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 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;
};
#endif