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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/. */

 /* rendering object to wrap rendering objects that should be scrollable */

 #ifndef nsGfxScrollFrame_h___

 #define nsGfxScrollFrame_h___

 #include "mozilla/Attributes.h"

 #include "nsContainerFrame.h"

 #include "nsIAnonymousContentCreator.h"

 #include "nsBoxFrame.h"

 #include "nsIScrollableFrame.h"

 #include "nsIStatefulFrame.h"

 #include "nsThreadUtils.h"

 #include "nsIReflowCallback.h"

 #include "nsBoxLayoutState.h"

 #include "nsQueryFrame.h"

 #include "nsExpirationTracker.h"

 class nsPresContext;

 class nsIPresShell;

 class nsIContent;

 class nsIAtom;

 class nsIScrollFrameInternal;

 class nsPresState;

 class nsIScrollPositionListener;

 struct ScrollReflowState;

 namespace mozilla {

 namespace layout {

 class ScrollbarActivity;

 }

 }

 namespace mozilla {

 class ScrollFrameHelper : public nsIReflowCallback {

 public:

   typedef mozilla::CSSIntPoint CSSIntPoint;

   typedef mozilla::layout::ScrollbarActivity ScrollbarActivity;

   class AsyncScroll;

   ScrollFrameHelper(nsContainerFrame* aOuter, bool aIsRoot);

   ~ScrollFrameHelper();

   mozilla::ScrollbarStyles GetScrollbarStylesFromFrame() 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();

   nsresult CreateAnonymousContent(

     nsTArray<nsIAnonymousContentCreator::ContentInfo>& aElements);

   void AppendAnonymousContentTo(nsBaseContentList& aElements, uint32_t aFilter);

   nsresult FireScrollPortEvent();

   void PostOverflowEvent();

   void Destroy();

   void BuildDisplayList(nsDisplayListBuilder*   aBuilder,

                         const nsRect&           aDirtyRect,

                         const nsDisplayListSet& aLists);

   void AppendScrollPartsTo(nsDisplayListBuilder*   aBuilder,

                            const nsRect&           aDirtyRect,

                            const nsDisplayListSet& aLists,

                            bool&                   aCreateLayer,

                            bool                    aPositioned);

   bool GetBorderRadii(nscoord aRadii[8]) const;

   // nsIReflowCallback

   virtual bool ReflowFinished() MOZ_OVERRIDE;

   virtual void ReflowCallbackCanceled() MOZ_OVERRIDE;

   /**

    * @note This method might destroy the frame, pres shell and other objects.

    * Called when the 'curpos' attribute on one of the scrollbars changes.

    */

   void CurPosAttributeChanged(nsIContent* aChild);

   void PostScrollEvent();

   void FireScrollEvent();

   void PostScrolledAreaEvent();

   void FireScrolledAreaEvent();

   class ScrollEvent : public nsRunnable {

   public:

     NS_DECL_NSIRUNNABLE

     ScrollEvent(ScrollFrameHelper *helper) : mHelper(helper) {}

     void Revoke() { mHelper = nullptr; }

   private:

     ScrollFrameHelper *mHelper;

   };

   class AsyncScrollPortEvent : public nsRunnable {

   public:

     NS_DECL_NSIRUNNABLE

     AsyncScrollPortEvent(ScrollFrameHelper *helper) : mHelper(helper) {}

     void Revoke() { mHelper = nullptr; }

   private:

     ScrollFrameHelper *mHelper;

   };

   class ScrolledAreaEvent : public nsRunnable {

   public:

     NS_DECL_NSIRUNNABLE

     ScrolledAreaEvent(ScrollFrameHelper *helper) : mHelper(helper) {}

     void Revoke() { mHelper = nullptr; }

   private:

     ScrollFrameHelper *mHelper;

   };

   /**

    * @note This method might destroy the frame, pres shell and other objects.

    */

   void FinishReflowForScrollbar(nsIContent* aContent, nscoord aMinXY,

                                 nscoord aMaxXY, nscoord aCurPosXY,

                                 nscoord aPageIncrement,

                                 nscoord aIncrement);

   /**

    * @note This method might destroy the frame, pres shell and other objects.

    */

   void SetScrollbarEnabled(nsIContent* aContent, nscoord aMaxPos);

   /**

    * @note This method might destroy the frame, pres shell and other objects.

    */

   void SetCoordAttribute(nsIContent* aContent, nsIAtom* aAtom, nscoord aSize);

   nscoord GetCoordAttribute(nsIFrame* aFrame, nsIAtom* aAtom, nscoord aDefaultValue,

                             nscoord* aRangeStart, nscoord* aRangeLength);

   /**

    * @note This method might destroy the frame, pres shell and other objects.

    * Update scrollbar curpos attributes to reflect current scroll position

    */

   void UpdateScrollbarPosition();

   nsRect GetScrollPortRect() const { return mScrollPort; }

   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 = IsLTR() ?

       mScrollPort.x - mScrolledFrame->GetPosition().x :

       mScrollPort.XMost() - mScrolledFrame->GetRect().XMost();

     pt.y = mScrollPort.y - mScrolledFrame->GetPosition().y;

     return pt;

   }

   nsRect GetScrollRange() const;

   // Get the scroll range assuming the scrollport has size (aWidth, aHeight).

   nsRect GetScrollRange(nscoord aWidth, nscoord aHeight) const;

   nsSize GetScrollPositionClampingScrollPortSize() const;

   gfxSize GetResolution() const;

   void SetResolution(const gfxSize& aResolution);

 protected:

   nsRect GetScrollRangeForClamping() const;

 public:

   static void AsyncScrollCallback(void* anInstance, mozilla::TimeStamp aTime);

   /**

    * @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 ScrollTo(nsPoint aScrollPosition, nsIScrollableFrame::ScrollMode aMode,

                 const nsRect* aRange = nullptr) {

     ScrollToWithOrigin(aScrollPosition, aMode, nsGkAtoms::other, aRange);

   }

   /**

    * @note This method might destroy the frame, pres shell and other objects.

    */

   void ScrollToCSSPixels(const CSSIntPoint& aScrollPosition);

   /**

    * @note This method might destroy the frame, pres shell and other objects.

    */

   void ScrollToCSSPixelsApproximate(const mozilla::CSSPoint& aScrollPosition,

                                     nsIAtom* aOrigin = nullptr);

   CSSIntPoint GetScrollPositionCSSPixels();

   /**

    * @note This method might destroy the frame, pres shell and other objects.

    */

   void ScrollToImpl(nsPoint aScrollPosition, const nsRect& aRange, nsIAtom* aOrigin = nullptr);

   void ScrollVisual(nsPoint aOldScrolledFramePosition);

   /**

    * @note This method might destroy the frame, pres shell and other objects.

    */

   void ScrollBy(nsIntPoint aDelta, nsIScrollableFrame::ScrollUnit aUnit,

                 nsIScrollableFrame::ScrollMode aMode, nsIntPoint* aOverflow, nsIAtom *aOrigin = nullptr);

   /**

    * @note This method might destroy the frame, pres shell and other objects.

    */

   void ScrollToRestoredPosition();

   nsSize GetLineScrollAmount() const;

   nsSize GetPageScrollAmount() const;

   nsPresState* SaveState() const;

   void RestoreState(nsPresState* aState);

   nsIFrame* GetScrolledFrame() const { return mScrolledFrame; }

   nsIFrame* GetScrollbarBox(bool aVertical) const {

     return aVertical ? mVScrollbarBox : mHScrollbarBox;

   }

   void AddScrollPositionListener(nsIScrollPositionListener* aListener) {

     mListeners.AppendElement(aListener);

   }

   void RemoveScrollPositionListener(nsIScrollPositionListener* aListener) {

     mListeners.RemoveElement(aListener);

   }

   static void SetScrollbarVisibility(nsIFrame* aScrollbar, bool aVisible);

   /**

    * 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.

    */

   nsRect GetScrolledRect() const;

   /**

    * GetScrolledRectInternal 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).

    * 

    * 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.

    */

   nsRect GetScrolledRectInternal(const nsRect& aScrolledOverflowArea,

                                  const nsSize& aScrollPortSize) const;

   uint32_t GetScrollbarVisibility() const {

     return (mHasVerticalScrollbar ? nsIScrollableFrame::VERTICAL : 0) |

            (mHasHorizontalScrollbar ? nsIScrollableFrame::HORIZONTAL : 0);

   }

   nsMargin GetActualScrollbarSizes() const;

   nsMargin GetDesiredScrollbarSizes(nsBoxLayoutState* aState);

   nscoord GetNondisappearingScrollbarWidth(nsBoxLayoutState* aState);

   bool IsLTR() const;

   bool IsScrollbarOnRight() const;

   bool IsScrollingActive() const { return mScrollingActive || mShouldBuildScrollableLayer; }

   bool IsProcessingAsyncScroll() const { return mAsyncScroll != nullptr; }

   void ResetScrollPositionForLayerPixelAlignment()

   {

     mScrollPosForLayerPixelAlignment = GetScrollPosition();

   }

   bool UpdateOverflow();

   void UpdateSticky();

   bool IsRectNearlyVisible(const nsRect& aRect) const;

   // 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, bool aVertical);

   // returns true if a resizer should be visible

   bool HasResizer() { return mResizerBox && !mCollapsedResizer; }

   void LayoutScrollbars(nsBoxLayoutState& aState,

                         const nsRect& aContentArea,

                         const nsRect& aOldScrollArea);

   bool IsIgnoringViewportClipping() const;

   bool ShouldClampScrollPosition() const;

   bool IsAlwaysActive() const;

   void MarkActive();

   void MarkInactive();

   nsExpirationState* GetExpirationState() { return &mActivityExpirationState; }

   void ScheduleSyntheticMouseMove();

   static void ScrollActivityCallback(nsITimer *aTimer, void* anInstance);

   void HandleScrollbarStyleSwitching();

   nsIAtom* OriginOfLastScroll() const { return mOriginOfLastScroll; }

   uint32_t CurrentScrollGeneration() const { return mScrollGeneration; }

   void ResetOriginIfScrollAtGeneration(uint32_t aGeneration) {

     if (aGeneration == mScrollGeneration) {

       mOriginOfLastScroll = nullptr;

     }

   }

   bool WantAsyncScroll() const;

   // owning references to the nsIAnonymousContentCreator-built content

   nsCOMPtr<nsIContent> mHScrollbarContent;

   nsCOMPtr<nsIContent> mVScrollbarContent;

   nsCOMPtr<nsIContent> mScrollCornerContent;

   nsCOMPtr<nsIContent> mResizerContent;

   nsRevocableEventPtr<ScrollEvent> mScrollEvent;

   nsRevocableEventPtr<AsyncScrollPortEvent> mAsyncScrollPortEvent;

   nsRevocableEventPtr<ScrolledAreaEvent> mScrolledAreaEvent;

   nsIFrame* mHScrollbarBox;

   nsIFrame* mVScrollbarBox;

   nsIFrame* mScrolledFrame;

   nsIFrame* mScrollCornerBox;

   nsIFrame* mResizerBox;

   nsContainerFrame* mOuter;

   nsRefPtr<AsyncScroll> mAsyncScroll;

   nsRefPtr<ScrollbarActivity> mScrollbarActivity;

   nsTArray<nsIScrollPositionListener*> mListeners;

   nsIAtom* mOriginOfLastScroll;

   uint32_t mScrollGeneration;

   nsRect mScrollPort;

   // 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;

   nsPoint mScrollPosAtLastPaint;

   // 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.

   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.

   nsPoint mLastPos;

   // The current resolution derived from the zoom level and device pixel ratio.

   gfxSize mResolution;

   nsExpirationState mActivityExpirationState;

   nsCOMPtr<nsITimer> mScrollActivityTimer;

   nsPoint mScrollPosForLayerPixelAlignment;

   // The scroll position where we last updated image visibility.

   nsPoint mLastUpdateImagesPos;

   bool mNeverHasVerticalScrollbar:1;

   bool mNeverHasHorizontalScrollbar:1;

   bool mHasVerticalScrollbar:1;

   bool mHasHorizontalScrollbar:1;

   bool mFrameIsUpdatingScrollbar:1;

   bool mDidHistoryRestore:1;

   // Is this the scrollframe for the document's viewport?

   bool mIsRoot:1;

   // True if we should clip all descendants, false if we should only clip

   // descendants for which we are the containing block.

   bool mClipAllDescendants: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 mSupppressScrollbarUpdate:1;

   // If true, we skipped a scrollbar layout due to mSupppressScrollbarUpdate

   // being set at some point.  That means we should lay out scrollbars even if

   // it might not strictly be needed next time mSupppressScrollbarUpdate is

   // false.

   bool mSkippedScrollbarLayout:1;

   bool mHadNonInitialReflow: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 mScrollingActive:1;

   // If true, the resizer is collapsed and not displayed

   bool mCollapsedResizer:1;

   // If true, the layer should always be active because we always build a

   // scrollable layer. Used for asynchronous scrolling.

   bool mShouldBuildScrollableLayer:1;

   // True if this frame has been scrolled at least once

   bool mHasBeenScrolled:1;

   // True if the frame's resolution has been set via SetResolution or restored

   // via RestoreState.

   bool mIsResolutionSet:1;

 protected:

   /**

    * @note This method might destroy the frame, pres shell and other objects.

    */

   void ScrollToWithOrigin(nsPoint aScrollPosition,

                           nsIScrollableFrame::ScrollMode aMode,

                           nsIAtom *aOrigin, // nullptr indicates "other" origin

                           const nsRect* aRange);

   nsRect ExpandRect(const nsRect& aRect) const;

   static void EnsureImageVisPrefsCached();

   static bool sImageVisPrefsCached;

   // The number of scrollports wide/high to expand when looking for images.

   static uint32_t sHorzExpandScrollPort;

   static uint32_t sVertExpandScrollPort;

   // The fraction of the scrollport we allow to scroll by before we schedule

   // an update of image visibility.

   static int32_t sHorzScrollFraction;

   static int32_t sVertScrollFraction;

 };

 }

 /**

  * The scroll frame creates and manages the scrolling view

  *

  * It only supports having a single child frame that typically is an area

  * frame, but doesn't have to be. The child frame must have a view, though

  *

  * Scroll frames don't support incremental changes, i.e. you can't replace

  * or remove the scrolled frame

  */

 class nsHTMLScrollFrame : public nsContainerFrame,

                           public nsIScrollableFrame,

                           public nsIAnonymousContentCreator,

                           public nsIStatefulFrame {

 public:

   typedef mozilla::ScrollFrameHelper ScrollFrameHelper;

   typedef mozilla::CSSIntPoint CSSIntPoint;

   friend nsIFrame* NS_NewHTMLScrollFrame(nsIPresShell* aPresShell, nsStyleContext* aContext, bool aIsRoot);

   NS_DECL_QUERYFRAME

   NS_DECL_FRAMEARENA_HELPERS

   // Called to set the child frames. We typically have three: the scroll area,

   // the vertical scrollbar, and the horizontal scrollbar.

   virtual nsresult SetInitialChildList(ChildListID     aListID,

                                        nsFrameList&    aChildList) MOZ_OVERRIDE;

   virtual void BuildDisplayList(nsDisplayListBuilder*   aBuilder,

                                 const nsRect&           aDirtyRect,

                                 const nsDisplayListSet& aLists) MOZ_OVERRIDE {

     mHelper.BuildDisplayList(aBuilder, aDirtyRect, aLists);

   }

   bool TryLayout(ScrollReflowState* aState,

                    nsHTMLReflowMetrics* aKidMetrics,

                    bool aAssumeVScroll, bool aAssumeHScroll,

                    bool aForce, nsresult* aResult);

   bool ScrolledContentDependsOnHeight(ScrollReflowState* aState);

   nsresult ReflowScrolledFrame(ScrollReflowState* aState,

                                bool aAssumeHScroll,

                                bool aAssumeVScroll,

                                nsHTMLReflowMetrics* aMetrics,

                                bool aFirstPass);

   nsresult ReflowContents(ScrollReflowState* aState,

                           const nsHTMLReflowMetrics& aDesiredSize);

   void PlaceScrollArea(const ScrollReflowState& aState,

                        const nsPoint& aScrollPosition);

   nscoord GetIntrinsicVScrollbarWidth(nsRenderingContext *aRenderingContext);

   virtual bool GetBorderRadii(nscoord aRadii[8]) const MOZ_OVERRIDE {

     return mHelper.GetBorderRadii(aRadii);

   }

   virtual nscoord GetMinWidth(nsRenderingContext *aRenderingContext) MOZ_OVERRIDE;

   virtual nscoord GetPrefWidth(nsRenderingContext *aRenderingContext) MOZ_OVERRIDE;

   virtual nsresult GetPadding(nsMargin& aPadding) MOZ_OVERRIDE;

   virtual bool IsCollapsed() MOZ_OVERRIDE;

   virtual nsresult Reflow(nsPresContext*           aPresContext,

                           nsHTMLReflowMetrics&     aDesiredSize,

                           const nsHTMLReflowState& aReflowState,

                           nsReflowStatus&          aStatus) MOZ_OVERRIDE;

   virtual bool UpdateOverflow() MOZ_OVERRIDE {

     return mHelper.UpdateOverflow();

   }

   // Because there can be only one child frame, these two function return

   // NS_ERROR_FAILURE

   virtual nsresult AppendFrames(ChildListID     aListID,

                                 nsFrameList&    aFrameList) MOZ_OVERRIDE;

   virtual nsresult InsertFrames(ChildListID     aListID,

                                 nsIFrame*       aPrevFrame,

                                 nsFrameList&    aFrameList) MOZ_OVERRIDE;

   virtual void DestroyFrom(nsIFrame* aDestructRoot) MOZ_OVERRIDE;

   virtual nsresult RemoveFrame(ChildListID     aListID,

                                nsIFrame*       aOldFrame) MOZ_OVERRIDE;

   virtual nsIScrollableFrame* GetScrollTargetFrame() MOZ_OVERRIDE {

     return this;

   }

   virtual nsIFrame* GetContentInsertionFrame() MOZ_OVERRIDE {

     return mHelper.GetScrolledFrame()->GetContentInsertionFrame();

   }

   virtual bool DoesClipChildren() MOZ_OVERRIDE { return true; }

   virtual nsSplittableType GetSplittableType() const MOZ_OVERRIDE;

   virtual nsPoint GetPositionOfChildIgnoringScrolling(nsIFrame* aChild) MOZ_OVERRIDE

   { nsPoint pt = aChild->GetPosition();

     if (aChild == mHelper.GetScrolledFrame()) pt += GetScrollPosition();

     return pt;

   }

   // nsIAnonymousContentCreator

   virtual nsresult CreateAnonymousContent(nsTArray<ContentInfo>& aElements) MOZ_OVERRIDE;

   virtual void AppendAnonymousContentTo(nsBaseContentList& aElements,

                                         uint32_t aFilter) MOZ_OVERRIDE;

   // nsIScrollbarOwner

   virtual nsIFrame* GetScrollbarBox(bool aVertical) MOZ_OVERRIDE {

     return mHelper.GetScrollbarBox(aVertical);

   }

   virtual void ScrollbarActivityStarted() const MOZ_OVERRIDE;

   virtual void ScrollbarActivityStopped() const MOZ_OVERRIDE;

   // nsIScrollableFrame

   virtual nsIFrame* GetScrolledFrame() const MOZ_OVERRIDE {

     return mHelper.GetScrolledFrame();

   }

   virtual mozilla::ScrollbarStyles GetScrollbarStyles() const MOZ_OVERRIDE {

     return mHelper.GetScrollbarStylesFromFrame();

   }

   virtual uint32_t GetScrollbarVisibility() const MOZ_OVERRIDE {

     return mHelper.GetScrollbarVisibility();

   }

   virtual nsMargin GetActualScrollbarSizes() const MOZ_OVERRIDE {

     return mHelper.GetActualScrollbarSizes();

   }

   virtual nsMargin GetDesiredScrollbarSizes(nsBoxLayoutState* aState) MOZ_OVERRIDE {

     return mHelper.GetDesiredScrollbarSizes(aState);

   }

   virtual nsMargin GetDesiredScrollbarSizes(nsPresContext* aPresContext,

           nsRenderingContext* aRC) MOZ_OVERRIDE {

     nsBoxLayoutState bls(aPresContext, aRC, 0);

     return GetDesiredScrollbarSizes(&bls);

   }

   virtual nscoord GetNondisappearingScrollbarWidth(nsPresContext* aPresContext,

           nsRenderingContext* aRC) MOZ_OVERRIDE {

     nsBoxLayoutState bls(aPresContext, aRC, 0);

     return mHelper.GetNondisappearingScrollbarWidth(&bls);

   }

   virtual nsRect GetScrolledRect() const MOZ_OVERRIDE {

     return mHelper.GetScrolledRect();

   }

   virtual nsRect GetScrollPortRect() const MOZ_OVERRIDE {

     return mHelper.GetScrollPortRect();

   }

   virtual nsPoint GetScrollPosition() const MOZ_OVERRIDE {

     return mHelper.GetScrollPosition();

   }

   virtual nsPoint GetLogicalScrollPosition() const MOZ_OVERRIDE {

     return mHelper.GetLogicalScrollPosition();

   }

   virtual nsRect GetScrollRange() const MOZ_OVERRIDE {

     return mHelper.GetScrollRange();

   }

   virtual nsSize GetScrollPositionClampingScrollPortSize() const MOZ_OVERRIDE {

     return mHelper.GetScrollPositionClampingScrollPortSize();

   }

   virtual gfxSize GetResolution() const MOZ_OVERRIDE {

     return mHelper.GetResolution();

   }

   virtual void SetResolution(const gfxSize& aResolution) MOZ_OVERRIDE {

     return mHelper.SetResolution(aResolution);

   }

   virtual nsSize GetLineScrollAmount() const MOZ_OVERRIDE {

     return mHelper.GetLineScrollAmount();

   }

   virtual nsSize GetPageScrollAmount() const MOZ_OVERRIDE {

     return mHelper.GetPageScrollAmount();

   }

   /**

    * @note This method might destroy the frame, pres shell and other objects.

    */

   virtual void ScrollTo(nsPoint aScrollPosition, ScrollMode aMode,

                         const nsRect* aRange = nullptr) MOZ_OVERRIDE {

     mHelper.ScrollTo(aScrollPosition, aMode, aRange);

   }

   /**

    * @note This method might destroy the frame, pres shell and other objects.

    */

   virtual void ScrollToCSSPixels(const CSSIntPoint& aScrollPosition) MOZ_OVERRIDE {

     mHelper.ScrollToCSSPixels(aScrollPosition);

   }

   virtual void ScrollToCSSPixelsApproximate(const mozilla::CSSPoint& aScrollPosition,

                                             nsIAtom* aOrigin = nullptr) MOZ_OVERRIDE {

     mHelper.ScrollToCSSPixelsApproximate(aScrollPosition, aOrigin);

   }

   /**

    * @note This method might destroy the frame, pres shell and other objects.

    */

   virtual CSSIntPoint GetScrollPositionCSSPixels() MOZ_OVERRIDE {

     return mHelper.GetScrollPositionCSSPixels();

   }

   /**

    * @note This method might destroy the frame, pres shell and other objects.

    */

   virtual void ScrollBy(nsIntPoint aDelta, ScrollUnit aUnit, ScrollMode aMode,

                         nsIntPoint* aOverflow, nsIAtom *aOrigin = nullptr) MOZ_OVERRIDE {

     mHelper.ScrollBy(aDelta, aUnit, aMode, aOverflow, aOrigin);

   }

   /**

    * @note This method might destroy the frame, pres shell and other objects.

    */

   virtual void ScrollToRestoredPosition() MOZ_OVERRIDE {

     mHelper.ScrollToRestoredPosition();

   }

   virtual void AddScrollPositionListener(nsIScrollPositionListener* aListener) MOZ_OVERRIDE {

     mHelper.AddScrollPositionListener(aListener);

   }

   virtual void RemoveScrollPositionListener(nsIScrollPositionListener* aListener) MOZ_OVERRIDE {

     mHelper.RemoveScrollPositionListener(aListener);

   }

   /**

    * @note This method might destroy the frame, pres shell and other objects.

    */

   virtual void CurPosAttributeChanged(nsIContent* aChild) MOZ_OVERRIDE {

     mHelper.CurPosAttributeChanged(aChild);

   }

   NS_IMETHOD PostScrolledAreaEventForCurrentArea() MOZ_OVERRIDE {

     mHelper.PostScrolledAreaEvent();

     return NS_OK;

   }

   virtual bool IsScrollingActive() MOZ_OVERRIDE {

     return mHelper.IsScrollingActive();

   }

   virtual bool IsProcessingAsyncScroll() MOZ_OVERRIDE {

     return mHelper.IsProcessingAsyncScroll();

   }

   virtual void ResetScrollPositionForLayerPixelAlignment() MOZ_OVERRIDE {

     mHelper.ResetScrollPositionForLayerPixelAlignment();

   }

   virtual bool IsResolutionSet() const MOZ_OVERRIDE {

     return mHelper.mIsResolutionSet;

   }

   virtual bool DidHistoryRestore() const MOZ_OVERRIDE {

     return mHelper.mDidHistoryRestore;

   }

   virtual void ClearDidHistoryRestore() MOZ_OVERRIDE {

     mHelper.mDidHistoryRestore = false;

   }

   virtual bool IsRectNearlyVisible(const nsRect& aRect) MOZ_OVERRIDE {

     return mHelper.IsRectNearlyVisible(aRect);

   }

   virtual nsIAtom* OriginOfLastScroll() MOZ_OVERRIDE {

     return mHelper.OriginOfLastScroll();

   }

   virtual uint32_t CurrentScrollGeneration() MOZ_OVERRIDE {

     return mHelper.CurrentScrollGeneration();

   }

   virtual void ResetOriginIfScrollAtGeneration(uint32_t aGeneration) MOZ_OVERRIDE {

     mHelper.ResetOriginIfScrollAtGeneration(aGeneration);

   }

   virtual bool WantAsyncScroll() const MOZ_OVERRIDE {

     return mHelper.WantAsyncScroll();

   }

   // nsIStatefulFrame

   NS_IMETHOD SaveState(nsPresState** aState) MOZ_OVERRIDE {

     NS_ENSURE_ARG_POINTER(aState);

     *aState = mHelper.SaveState();

     return NS_OK;

   }

   NS_IMETHOD RestoreState(nsPresState* aState) MOZ_OVERRIDE {

     NS_ENSURE_ARG_POINTER(aState);

     mHelper.RestoreState(aState);

     return NS_OK;

   }

   /**

    * Get the "type" of the frame

    *

    * @see nsGkAtoms::scrollFrame

    */

   virtual nsIAtom* GetType() const MOZ_OVERRIDE;

 #ifdef DEBUG_FRAME_DUMP

   virtual nsresult GetFrameName(nsAString& aResult) const MOZ_OVERRIDE;

 #endif

 #ifdef ACCESSIBILITY

   virtual mozilla::a11y::AccType AccessibleType() MOZ_OVERRIDE;

 #endif

 protected:

   nsHTMLScrollFrame(nsIPresShell* aShell, nsStyleContext* aContext, bool aIsRoot);

   void SetSuppressScrollbarUpdate(bool aSuppress) {

     mHelper.mSupppressScrollbarUpdate = aSuppress;

   }

   bool GuessHScrollbarNeeded(const ScrollReflowState& aState);

   bool GuessVScrollbarNeeded(const ScrollReflowState& aState);

   bool IsScrollbarUpdateSuppressed() const {

     return mHelper.mSupppressScrollbarUpdate;

   }

   // Return whether we're in an "initial" reflow.  Some reflows with

   // NS_FRAME_FIRST_REFLOW set are NOT "initial" as far as we're concerned.

   bool InInitialReflow() const;

   /**

    * Override this to return false if computed height/min-height/max-height

    * should NOT be propagated to child content.

    * nsListControlFrame uses this.

    */

   virtual bool ShouldPropagateComputedHeightToScrolledContent() const { return true; }

 private:

   friend class mozilla::ScrollFrameHelper;

   ScrollFrameHelper mHelper;

 };

 /**

  * 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 nsXULScrollFrame : public nsBoxFrame,

                          public nsIScrollableFrame,

                          public nsIAnonymousContentCreator,

                          public nsIStatefulFrame {

 public:

   typedef mozilla::ScrollFrameHelper ScrollFrameHelper;

   typedef mozilla::CSSIntPoint CSSIntPoint;

   NS_DECL_QUERYFRAME

   NS_DECL_FRAMEARENA_HELPERS

   friend nsIFrame* NS_NewXULScrollFrame(nsIPresShell* aPresShell, nsStyleContext* aContext,

                                         bool aIsRoot, bool aClipAllDescendants);

   // Called to set the child frames. We typically have three: the scroll area,

   // the vertical scrollbar, and the horizontal scrollbar.

   virtual nsresult SetInitialChildList(ChildListID     aListID,

                                        nsFrameList&    aChildList) MOZ_OVERRIDE;

   virtual void BuildDisplayList(nsDisplayListBuilder*   aBuilder,

                                 const nsRect&           aDirtyRect,

                                 const nsDisplayListSet& aLists) MOZ_OVERRIDE {

     mHelper.BuildDisplayList(aBuilder, aDirtyRect, aLists);

   }

   // XXXldb Is this actually used?

 #if 0

   virtual nscoord GetMinWidth(nsRenderingContext *aRenderingContext) MOZ_OVERRIDE;

 #endif

   virtual bool UpdateOverflow() MOZ_OVERRIDE {

     return mHelper.UpdateOverflow();

   }

   // Because there can be only one child frame, these two function return

   // NS_ERROR_FAILURE

   virtual nsresult AppendFrames(ChildListID     aListID,

                                 nsFrameList&    aFrameList) MOZ_OVERRIDE;

   virtual nsresult InsertFrames(ChildListID     aListID,

                                 nsIFrame*       aPrevFrame,

                                 nsFrameList&    aFrameList) MOZ_OVERRIDE;

   virtual void DestroyFrom(nsIFrame* aDestructRoot) MOZ_OVERRIDE;

   virtual nsresult RemoveFrame(ChildListID     aListID,

                                nsIFrame*       aOldFrame) MOZ_OVERRIDE;

   virtual nsIScrollableFrame* GetScrollTargetFrame() MOZ_OVERRIDE {

     return this;

   }

   virtual nsIFrame* GetContentInsertionFrame() MOZ_OVERRIDE {

     return mHelper.GetScrolledFrame()->GetContentInsertionFrame();

   }

   virtual bool DoesClipChildren() MOZ_OVERRIDE { return true; }

   virtual nsSplittableType GetSplittableType() const MOZ_OVERRIDE;

   virtual nsPoint GetPositionOfChildIgnoringScrolling(nsIFrame* aChild) MOZ_OVERRIDE

   { nsPoint pt = aChild->GetPosition();

     if (aChild == mHelper.GetScrolledFrame())

       pt += mHelper.GetLogicalScrollPosition();

     return pt;

   }

   // nsIAnonymousContentCreator

   virtual nsresult CreateAnonymousContent(nsTArray<ContentInfo>& aElements) MOZ_OVERRIDE;

   virtual void AppendAnonymousContentTo(nsBaseContentList& aElements,

                                         uint32_t aFilter) MOZ_OVERRIDE;

   virtual nsSize GetMinSize(nsBoxLayoutState& aBoxLayoutState) MOZ_OVERRIDE;

   virtual nsSize GetPrefSize(nsBoxLayoutState& aBoxLayoutState) MOZ_OVERRIDE;

   virtual nsSize GetMaxSize(nsBoxLayoutState& aBoxLayoutState) MOZ_OVERRIDE;

   virtual nscoord GetBoxAscent(nsBoxLayoutState& aBoxLayoutState) MOZ_OVERRIDE;

   NS_IMETHOD DoLayout(nsBoxLayoutState& aBoxLayoutState) MOZ_OVERRIDE;

   virtual nsresult GetPadding(nsMargin& aPadding) MOZ_OVERRIDE;

   virtual bool GetBorderRadii(nscoord aRadii[8]) const MOZ_OVERRIDE {

     return mHelper.GetBorderRadii(aRadii);

   }

   nsresult Layout(nsBoxLayoutState& aState);

   void LayoutScrollArea(nsBoxLayoutState& aState, const nsPoint& aScrollPosition);

   static bool AddRemoveScrollbar(bool& aHasScrollbar, 

                                    nscoord& aXY, 

                                    nscoord& aSize, 

                                    nscoord aSbSize, 

                                    bool aOnRightOrBottom, 

                                    bool aAdd);

   bool AddRemoveScrollbar(nsBoxLayoutState& aState, 

                             bool aOnRightOrBottom, 

                             bool aHorizontal, 

                             bool aAdd);

   bool AddHorizontalScrollbar (nsBoxLayoutState& aState, bool aOnBottom);

   bool AddVerticalScrollbar   (nsBoxLayoutState& aState, bool aOnRight);

   void RemoveHorizontalScrollbar(nsBoxLayoutState& aState, bool aOnBottom);

   void RemoveVerticalScrollbar  (nsBoxLayoutState& aState, bool aOnRight);

   static void AdjustReflowStateForPrintPreview(nsBoxLayoutState& aState, bool& aSetBack);

   static void AdjustReflowStateBack(nsBoxLayoutState& aState, bool aSetBack);

   // nsIScrollbarOwner

   virtual nsIFrame* GetScrollbarBox(bool aVertical) MOZ_OVERRIDE {

     return mHelper.GetScrollbarBox(aVertical);

   }

   virtual void ScrollbarActivityStarted() const MOZ_OVERRIDE;

   virtual void ScrollbarActivityStopped() const MOZ_OVERRIDE;

   // nsIScrollableFrame

   virtual nsIFrame* GetScrolledFrame() const MOZ_OVERRIDE {

     return mHelper.GetScrolledFrame();

   }

   virtual mozilla::ScrollbarStyles GetScrollbarStyles() const MOZ_OVERRIDE {

     return mHelper.GetScrollbarStylesFromFrame();

   }

   virtual uint32_t GetScrollbarVisibility() const MOZ_OVERRIDE {

     return mHelper.GetScrollbarVisibility();

   }

   virtual nsMargin GetActualScrollbarSizes() const MOZ_OVERRIDE {

     return mHelper.GetActualScrollbarSizes();

   }

   virtual nsMargin GetDesiredScrollbarSizes(nsBoxLayoutState* aState) MOZ_OVERRIDE {

     return mHelper.GetDesiredScrollbarSizes(aState);

   }

   virtual nsMargin GetDesiredScrollbarSizes(nsPresContext* aPresContext,

           nsRenderingContext* aRC) MOZ_OVERRIDE {

     nsBoxLayoutState bls(aPresContext, aRC, 0);

     return GetDesiredScrollbarSizes(&bls);

   }

   virtual nscoord GetNondisappearingScrollbarWidth(nsPresContext* aPresContext,

           nsRenderingContext* aRC) MOZ_OVERRIDE {

     nsBoxLayoutState bls(aPresContext, aRC, 0);

     return mHelper.GetNondisappearingScrollbarWidth(&bls);

   }

   virtual nsRect GetScrolledRect() const MOZ_OVERRIDE {

     return mHelper.GetScrolledRect();

   }

   virtual nsRect GetScrollPortRect() const MOZ_OVERRIDE {

     return mHelper.GetScrollPortRect();

   }

   virtual nsPoint GetScrollPosition() const MOZ_OVERRIDE {

     return mHelper.GetScrollPosition();

   }

   virtual nsPoint GetLogicalScrollPosition() const MOZ_OVERRIDE {

     return mHelper.GetLogicalScrollPosition();

   }

   virtual nsRect GetScrollRange() const MOZ_OVERRIDE {

     return mHelper.GetScrollRange();

   }

   virtual nsSize GetScrollPositionClampingScrollPortSize() const MOZ_OVERRIDE {

     return mHelper.GetScrollPositionClampingScrollPortSize();

   }

   virtual gfxSize GetResolution() const MOZ_OVERRIDE {

     return mHelper.GetResolution();

   }

   virtual void SetResolution(const gfxSize& aResolution) MOZ_OVERRIDE {

     return mHelper.SetResolution(aResolution);

   }

   virtual nsSize GetLineScrollAmount() const MOZ_OVERRIDE {

     return mHelper.GetLineScrollAmount();

   }

   virtual nsSize GetPageScrollAmount() const MOZ_OVERRIDE {

     return mHelper.GetPageScrollAmount();

   }

   /**

    * @note This method might destroy the frame, pres shell and other objects.

    */

   virtual void ScrollTo(nsPoint aScrollPosition, ScrollMode aMode,

                         const nsRect* aRange = nullptr) MOZ_OVERRIDE {

     mHelper.ScrollTo(aScrollPosition, aMode, aRange);

   }

   /**

    * @note This method might destroy the frame, pres shell and other objects.

    */

   virtual void ScrollToCSSPixels(const CSSIntPoint& aScrollPosition) MOZ_OVERRIDE {

     mHelper.ScrollToCSSPixels(aScrollPosition);

   }

   virtual void ScrollToCSSPixelsApproximate(const mozilla::CSSPoint& aScrollPosition,

                                             nsIAtom* aOrigin = nullptr) MOZ_OVERRIDE {

     mHelper.ScrollToCSSPixelsApproximate(aScrollPosition, aOrigin);

   }

   virtual CSSIntPoint GetScrollPositionCSSPixels() MOZ_OVERRIDE {

     return mHelper.GetScrollPositionCSSPixels();

   }

   /**

    * @note This method might destroy the frame, pres shell and other objects.

    */

   virtual void ScrollBy(nsIntPoint aDelta, ScrollUnit aUnit, ScrollMode aMode,

                         nsIntPoint* aOverflow, nsIAtom* aOrigin = nullptr) MOZ_OVERRIDE {

     mHelper.ScrollBy(aDelta, aUnit, aMode, aOverflow, aOrigin);

   }

   /**

    * @note This method might destroy the frame, pres shell and other objects.

    */

   virtual void ScrollToRestoredPosition() MOZ_OVERRIDE {

     mHelper.ScrollToRestoredPosition();

   }

   virtual void AddScrollPositionListener(nsIScrollPositionListener* aListener) MOZ_OVERRIDE {

     mHelper.AddScrollPositionListener(aListener);

   }

   virtual void RemoveScrollPositionListener(nsIScrollPositionListener* aListener) MOZ_OVERRIDE {

     mHelper.RemoveScrollPositionListener(aListener);

   }

   /**

    * @note This method might destroy the frame, pres shell and other objects.

    */

   virtual void CurPosAttributeChanged(nsIContent* aChild) MOZ_OVERRIDE {

     mHelper.CurPosAttributeChanged(aChild);

   }

   NS_IMETHOD PostScrolledAreaEventForCurrentArea() MOZ_OVERRIDE {

     mHelper.PostScrolledAreaEvent();

     return NS_OK;

   }

   virtual bool IsScrollingActive() MOZ_OVERRIDE {

     return mHelper.IsScrollingActive();

   }

   virtual bool IsProcessingAsyncScroll() MOZ_OVERRIDE {

     return mHelper.IsProcessingAsyncScroll();

   }

   virtual void ResetScrollPositionForLayerPixelAlignment() MOZ_OVERRIDE {

     mHelper.ResetScrollPositionForLayerPixelAlignment();

   }

   virtual bool IsResolutionSet() const MOZ_OVERRIDE {

     return mHelper.mIsResolutionSet;

   }

   virtual bool DidHistoryRestore() const MOZ_OVERRIDE {

     return mHelper.mDidHistoryRestore;

   }

   virtual void ClearDidHistoryRestore() MOZ_OVERRIDE {

     mHelper.mDidHistoryRestore = false;

   }

   virtual bool IsRectNearlyVisible(const nsRect& aRect) MOZ_OVERRIDE {

     return mHelper.IsRectNearlyVisible(aRect);

   }

   virtual nsIAtom* OriginOfLastScroll() MOZ_OVERRIDE {

     return mHelper.OriginOfLastScroll();

   }

   virtual uint32_t CurrentScrollGeneration() MOZ_OVERRIDE {

     return mHelper.CurrentScrollGeneration();

   }

   virtual void ResetOriginIfScrollAtGeneration(uint32_t aGeneration) MOZ_OVERRIDE {

     mHelper.ResetOriginIfScrollAtGeneration(aGeneration);

   }

   virtual bool WantAsyncScroll() const MOZ_OVERRIDE {

     return mHelper.WantAsyncScroll();

   }

   // nsIStatefulFrame

   NS_IMETHOD SaveState(nsPresState** aState) MOZ_OVERRIDE {

     NS_ENSURE_ARG_POINTER(aState);

     *aState = mHelper.SaveState();

     return NS_OK;

   }

   NS_IMETHOD RestoreState(nsPresState* aState) MOZ_OVERRIDE {

     NS_ENSURE_ARG_POINTER(aState);

     mHelper.RestoreState(aState);

     return NS_OK;

   }

   /**

    * Get the "type" of the frame

    *

    * @see nsGkAtoms::scrollFrame

    */

   virtual nsIAtom* GetType() const MOZ_OVERRIDE;

   virtual bool IsFrameOfType(uint32_t aFlags) const MOZ_OVERRIDE

   {

     // Override bogus IsFrameOfType in nsBoxFrame.

     if (aFlags & (nsIFrame::eReplacedContainsBlock | nsIFrame::eReplaced))

       return false;

     return nsBoxFrame::IsFrameOfType(aFlags);

   }

 #ifdef DEBUG_FRAME_DUMP

   virtual nsresult GetFrameName(nsAString& aResult) const MOZ_OVERRIDE;

 #endif

 protected:

   nsXULScrollFrame(nsIPresShell* aShell, nsStyleContext* aContext, bool aIsRoot,

                    bool aClipAllDescendants);

   void ClampAndSetBounds(nsBoxLayoutState& aState, 

                          nsRect& aRect,

                          nsPoint aScrollPosition,

                          bool aRemoveOverflowAreas = false) {

     /* 

      * For RTL frames, restore the original scrolled position of the right

      * edge, then subtract the current width to find the physical position.

      */

     if (!mHelper.IsLTR()) {

       aRect.x = mHelper.mScrollPort.XMost() - aScrollPosition.x - aRect.width;

     }

     mHelper.mScrolledFrame->SetBounds(aState, aRect, aRemoveOverflowAreas);

   }

 private:

   friend class mozilla::ScrollFrameHelper;

   ScrollFrameHelper mHelper;

 };

 #endif /* nsGfxScrollFrame_h___ */