layout/generic/ScrollSnapInfo.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 #ifndef mozilla_layout_ScrollSnapInfo_h_
   8 #define mozilla_layout_ScrollSnapInfo_h_
   9
  10 #include <memory>
  11 #include "mozilla/ScrollTypes.h"
  12 #include "mozilla/ScrollSnapTargetId.h"
  13 #include "mozilla/ServoStyleConsts.h"
  14 #include "mozilla/Maybe.h"
  15 #include "mozilla/layers/LayersTypes.h"
  16 #include "nsPoint.h"
  17
  18 class nsIContent;
  19 class nsIFrame;
  20 struct nsRect;
  21 struct nsSize;
  22 struct nsStyleDisplay;
  23
  24 namespace mozilla {
  25
  26 enum class StyleScrollSnapStrictness : uint8_t;
  27 class WritingMode;
  28
  29 struct SnapPoint {
  30   SnapPoint() = default;
  31   explicit SnapPoint(const nsPoint& aPoint)
  32       : mX(Some(aPoint.x)), mY(Some(aPoint.y)) {}
  33   SnapPoint(Maybe<nscoord>&& aX, Maybe<nscoord>&& aY)
  34       : mX(std::move(aX)), mY(std::move(aY)) {}
  35
  36   bool operator==(const SnapPoint& aOther) const {
  37     return mX == aOther.mX && mY == aOther.mY;
  38   }
  39
  40   Maybe<nscoord> mX;
  41   Maybe<nscoord> mY;
  42 };
  43
  44 struct ScrollSnapInfo {
  45   using ScrollDirection = layers::ScrollDirection;
  46   ScrollSnapInfo();
  47
  48   bool operator==(const ScrollSnapInfo& aOther) const {
  49     return mScrollSnapStrictnessX == aOther.mScrollSnapStrictnessX &&
  50            mScrollSnapStrictnessY == aOther.mScrollSnapStrictnessY &&
  51            mSnapTargets == aOther.mSnapTargets &&
  52            mXRangeWiderThanSnapport == aOther.mXRangeWiderThanSnapport &&
  53            mYRangeWiderThanSnapport == aOther.mYRangeWiderThanSnapport &&
  54            mSnapportSize == aOther.mSnapportSize;
  55   }
  56
  57   bool HasScrollSnapping() const;
  58   bool HasSnapPositions() const;
  59
  60   void InitializeScrollSnapStrictness(WritingMode aWritingMode,
  61                                       const nsStyleDisplay* aDisplay);
  62
  63   // The scroll frame's scroll-snap-type.
  64   StyleScrollSnapStrictness mScrollSnapStrictnessX;
  65   StyleScrollSnapStrictness mScrollSnapStrictnessY;
  66
  67   struct SnapTarget {
  68     // The scroll positions corresponding to scroll-snap-align values.
  69     SnapPoint mSnapPoint;
  70
  71     // https://drafts.csswg.org/css-scroll-snap/#scroll-snap-area
  72     nsRect mSnapArea;
  73
  74     // https://drafts.csswg.org/css-scroll-snap/#propdef-scroll-snap-stop
  75     StyleScrollSnapStop mScrollSnapStop = StyleScrollSnapStop::Normal;
  76
  77     // Use for tracking the last snapped target.
  78     ScrollSnapTargetId mTargetId = ScrollSnapTargetId::None;
  79
  80     SnapTarget() = default;
  81
  82     SnapTarget(Maybe<nscoord>&& aSnapPositionX, Maybe<nscoord>&& aSnapPositionY,
  83                const nsRect& aSnapArea, StyleScrollSnapStop aScrollSnapStop,
  84                ScrollSnapTargetId aTargetId)
  85         : mSnapPoint(std::move(aSnapPositionX), std::move(aSnapPositionY)),
  86           mSnapArea(aSnapArea),
  87           mScrollSnapStop(aScrollSnapStop),
  88           mTargetId(aTargetId) {}
  89
  90     bool operator==(const SnapTarget& aOther) const {
  91       return mSnapPoint == aOther.mSnapPoint && mSnapArea == aOther.mSnapArea &&
  92              mScrollSnapStop == aOther.mScrollSnapStop &&
  93              mTargetId == aOther.mTargetId;
  94     }
  95   };
  96
  97   CopyableTArray<SnapTarget> mSnapTargets;
  98
  99   // A utility function to iterate over the valid snap targets for the given
 100   // |aDestination| until |aFunc| returns false.
 101   void ForEachValidTargetFor(
 102       const nsPoint& aDestination,
 103       const std::function<bool(const SnapTarget&)>& aFunc) const;
 104
 105   struct ScrollSnapRange {
 106     ScrollSnapRange() = default;
 107
 108     ScrollSnapRange(const nsRect& aSnapArea, ScrollDirection aDirection,
 109                     ScrollSnapTargetId aTargetId)
 110         : mSnapArea(aSnapArea), mDirection(aDirection), mTargetId(aTargetId) {}
 111
 112     nsRect mSnapArea;
 113     ScrollDirection mDirection;
 114     ScrollSnapTargetId mTargetId;
 115
 116     bool operator==(const ScrollSnapRange& aOther) const {
 117       return mDirection == aOther.mDirection && mSnapArea == aOther.mSnapArea &&
 118              mTargetId == aOther.mTargetId;
 119     }
 120
 121     nscoord Start() const {
 122       return mDirection == ScrollDirection::eHorizontal ? mSnapArea.X()
 123                                                         : mSnapArea.Y();
 124     }
 125
 126     nscoord End() const {
 127       return mDirection == ScrollDirection::eHorizontal ? mSnapArea.XMost()
 128                                                         : mSnapArea.YMost();
 129     }
 130
 131     // Returns true if |aPoint| is a valid snap position in this range.
 132     bool IsValid(nscoord aPoint, nscoord aSnapportSize) const {
 133       MOZ_ASSERT(End() - Start() > aSnapportSize);
 134       return Start() <= aPoint && aPoint <= End() - aSnapportSize;
 135     }
 136   };
 137   // An array of the range that the target element is larger than the snapport
 138   // on the axis.
 139   // Snap positions in this range will be valid snap positions in the case where
 140   // the distance between the closest snap position and the second closest snap
 141   // position is still larger than the snapport size.
 142   // See https://drafts.csswg.org/css-scroll-snap-1/#snap-overflow
 143   //
 144   // Note: This range contains scroll-margin values.
 145   CopyableTArray<ScrollSnapRange> mXRangeWiderThanSnapport;
 146   CopyableTArray<ScrollSnapRange> mYRangeWiderThanSnapport;
 147
 148   // Note: This snapport size has been already deflated by scroll-padding.
 149   nsSize mSnapportSize;
 150 };
 151
 152 }  // namespace mozilla
 153
 154 #endif  // mozilla_layout_ScrollSnapInfo_h_