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ScrollSnapInfo.h (4674B)

      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 #ifndef mozilla_layout_ScrollSnapInfo_h_
      8 #define mozilla_layout_ScrollSnapInfo_h_
      9 
     10 #include "mozilla/Maybe.h"
     11 #include "mozilla/ScrollSnapTargetId.h"
     12 #include "mozilla/ScrollTypes.h"
     13 #include "mozilla/ServoStyleConsts.h"
     14 #include "mozilla/layers/LayersTypes.h"
     15 #include "nsPoint.h"
     16 
     17 class nsIContent;
     18 class nsIFrame;
     19 struct nsRect;
     20 struct nsSize;
     21 struct nsStyleDisplay;
     22 
     23 namespace mozilla {
     24 
     25 enum class StyleScrollSnapStrictness : uint8_t;
     26 class WritingMode;
     27 
     28 struct SnapPoint {
     29  SnapPoint() = default;
     30  explicit SnapPoint(const nsPoint& aPoint)
     31      : mX(Some(aPoint.x)), mY(Some(aPoint.y)) {}
     32  SnapPoint(Maybe<nscoord>&& aX, Maybe<nscoord>&& aY)
     33      : mX(std::move(aX)), mY(std::move(aY)) {}
     34 
     35  bool operator==(const SnapPoint&) const = default;
     36 
     37  Maybe<nscoord> mX;
     38  Maybe<nscoord> mY;
     39 };
     40 
     41 struct ScrollSnapInfo {
     42  using ScrollDirection = layers::ScrollDirection;
     43  ScrollSnapInfo();
     44 
     45  bool operator==(const ScrollSnapInfo&) const = default;
     46 
     47  bool HasScrollSnapping() const;
     48  bool HasSnapPositions() const;
     49 
     50  void InitializeScrollSnapStrictness(WritingMode aWritingMode,
     51                                      const nsStyleDisplay* aDisplay);
     52 
     53  // The scroll frame's scroll-snap-type.
     54  StyleScrollSnapStrictness mScrollSnapStrictnessX;
     55  StyleScrollSnapStrictness mScrollSnapStrictnessY;
     56 
     57  struct SnapTarget {
     58    // The scroll positions corresponding to scroll-snap-align values.
     59    SnapPoint mSnapPoint;
     60 
     61    // https://drafts.csswg.org/css-scroll-snap/#scroll-snap-area
     62    nsRect mSnapArea;
     63 
     64    // https://drafts.csswg.org/css-scroll-snap/#propdef-scroll-snap-stop
     65    StyleScrollSnapStop mScrollSnapStop = StyleScrollSnapStop::Normal;
     66 
     67    // Use for tracking the last snapped target.
     68    ScrollSnapTargetId mTargetId = ScrollSnapTargetId::None;
     69 
     70    SnapTarget() = default;
     71 
     72    SnapTarget(Maybe<nscoord>&& aSnapPositionX, Maybe<nscoord>&& aSnapPositionY,
     73               const nsRect& aSnapArea, StyleScrollSnapStop aScrollSnapStop,
     74               ScrollSnapTargetId aTargetId)
     75        : mSnapPoint(std::move(aSnapPositionX), std::move(aSnapPositionY)),
     76          mSnapArea(aSnapArea),
     77          mScrollSnapStop(aScrollSnapStop),
     78          mTargetId(aTargetId) {}
     79 
     80    bool operator==(const SnapTarget& aOther) const = default;
     81  };
     82 
     83  CopyableTArray<SnapTarget> mSnapTargets;
     84 
     85  // A utility function to iterate over the valid snap targets for the given
     86  // |aDestination| until |aFunc| returns false.
     87  void ForEachValidTargetFor(
     88      const nsPoint& aDestination,
     89      const std::function<bool(const SnapTarget&)>& aFunc) const;
     90 
     91  struct ScrollSnapRange {
     92    ScrollSnapRange() = default;
     93 
     94    ScrollSnapRange(const nsRect& aSnapArea, ScrollDirection aDirection,
     95                    ScrollSnapTargetId aTargetId)
     96        : mSnapArea(aSnapArea), mDirection(aDirection), mTargetId(aTargetId) {}
     97 
     98    nsRect mSnapArea;
     99    ScrollDirection mDirection;
    100    ScrollSnapTargetId mTargetId;
    101 
    102    bool operator==(const ScrollSnapRange& aOther) const = default;
    103 
    104    nscoord Start() const {
    105      return mDirection == ScrollDirection::eHorizontal ? mSnapArea.X()
    106                                                        : mSnapArea.Y();
    107    }
    108 
    109    nscoord End() const {
    110      return mDirection == ScrollDirection::eHorizontal ? mSnapArea.XMost()
    111                                                        : mSnapArea.YMost();
    112    }
    113 
    114    // Returns true if |aPoint| is a valid snap position in this range.
    115    bool IsValid(nscoord aPoint, nscoord aSnapportSize) const {
    116      MOZ_ASSERT(End() - Start() > aSnapportSize);
    117      return Start() <= aPoint && aPoint <= End() - aSnapportSize;
    118    }
    119  };
    120  // An array of the range that the target element is larger than the snapport
    121  // on the axis.
    122  // Snap positions in this range will be valid snap positions in the case where
    123  // the distance between the closest snap position and the second closest snap
    124  // position is still larger than the snapport size.
    125  // See https://drafts.csswg.org/css-scroll-snap-1/#snap-overflow
    126  //
    127  // Note: This range contains scroll-margin values.
    128  CopyableTArray<ScrollSnapRange> mXRangeWiderThanSnapport;
    129  CopyableTArray<ScrollSnapRange> mYRangeWiderThanSnapport;
    130 
    131  // Note: This snapport size has been already deflated by scroll-padding.
    132  nsSize mSnapportSize;
    133 };
    134 
    135 }  // namespace mozilla
    136 
    137 #endif  // mozilla_layout_ScrollSnapInfo_h_