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The Tor Browser
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StickyScrollContainer.h (3570B)

      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 * compute sticky positioning, both during reflow and when the scrolling
      9 * container scrolls
     10 */
     11 
     12 #ifndef StickyScrollContainer_h
     13 #define StickyScrollContainer_h
     14 
     15 #include "mozilla/DepthOrderedFrameList.h"
     16 #include "nsPoint.h"
     17 #include "nsRectAbsolute.h"
     18 #include "nsTArray.h"
     19 
     20 struct nsRect;
     21 class nsIFrame;
     22 
     23 namespace mozilla {
     24 
     25 class ScrollContainerFrame;
     26 
     27 class StickyScrollContainer final {
     28 public:
     29  /**
     30   * Find (and create if necessary) the StickyScrollContainer associated with
     31   * the scroll container of the given frame, if a scroll container exists.
     32   */
     33  static StickyScrollContainer* GetOrCreateForFrame(nsIFrame*);
     34 
     35  void AddFrame(nsIFrame* aFrame) { mFrames.Add(aFrame); }
     36  void RemoveFrame(nsIFrame* aFrame) { mFrames.Remove(aFrame); }
     37 
     38  ScrollContainerFrame* ScrollContainer() const {
     39    return mScrollContainerFrame;
     40  }
     41 
     42  // Compute the offsets for a sticky position element
     43  static void ComputeStickyOffsets(nsIFrame* aFrame);
     44 
     45  /**
     46   * Compute the position of a sticky positioned frame, based on information
     47   * stored in its properties along with our scroll frame and scroll position.
     48   */
     49  nsPoint ComputePosition(nsIFrame* aFrame) const;
     50 
     51  /**
     52   * Compute where a frame should not scroll with the page, represented by the
     53   * difference of two rectangles.
     54   */
     55  void GetScrollRanges(nsIFrame* aFrame, nsRectAbsolute* aOuter,
     56                       nsRectAbsolute* aInner) const;
     57 
     58  /**
     59   * Compute and set the position of a frame and its following continuations.
     60   */
     61  void PositionContinuations(nsIFrame* aFrame);
     62 
     63  /**
     64   * Compute and set the position of all sticky frames, given the current
     65   * scroll position of the scroll frame. If not in reflow, aSubtreeRoot should
     66   * be null; otherwise, overflow-area updates will be limited to not affect
     67   * aSubtreeRoot or its ancestors.
     68   */
     69  void UpdatePositions(nsPoint aScrollPosition, nsIFrame* aSubtreeRoot);
     70 
     71  void ScrollPositionDidChange(const nsPoint&);
     72 
     73  ~StickyScrollContainer();
     74 
     75  const DepthOrderedFrameList& GetFrames() const { return mFrames; }
     76 
     77  /**
     78   * Returns true if the frame is "stuck" in the y direction, ie it's acting
     79   * like fixed position. aFrame should be in GetFrames().
     80   */
     81  bool IsStuckInYDirection(nsIFrame* aFrame) const;
     82 
     83  /**
     84   * Calls FrameNeedsReflow on all sticky position children.
     85   */
     86  void MarkFramesForReflow();
     87 
     88  void SetShouldFlatten(bool aShouldFlatten) {
     89    mShouldFlatten = aShouldFlatten;
     90  }
     91  bool ShouldFlattenAway() const { return mShouldFlatten; }
     92 
     93  explicit StickyScrollContainer(ScrollContainerFrame* aScrollContainerFrame);
     94 
     95 private:
     96  /**
     97   * Compute two rectangles that determine sticky positioning: |aStick|, based
     98   * on the scroll container, and |aContain|, based on the containing block.
     99   * Sticky positioning keeps the frame position (its upper-left corner) always
    100   * within |aContain| and secondarily within |aStick|.
    101   */
    102  void ComputeStickyLimits(nsIFrame* aFrame, nsRect* aStick,
    103                           nsRect* aContain) const;
    104 
    105  ScrollContainerFrame* const mScrollContainerFrame;
    106  DepthOrderedFrameList mFrames;
    107  nsPoint mScrollPosition;
    108  bool mShouldFlatten = false;
    109 };
    110 
    111 }  // namespace mozilla
    112 
    113 #endif /* StickyScrollContainer_h */