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diff --git a/layout/base/MotionPathUtils.h b/layout/base/MotionPathUtils.h
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+++ b/layout/base/MotionPathUtils.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+#ifndef mozilla_MotionPathUtils_h
+#define mozilla_MotionPathUtils_h
+
+#include "mozilla/gfx/2D.h"
+#include "mozilla/gfx/Point.h"
+#include "mozilla/gfx/Rect.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/ServoStyleConsts.h"
+#include "Units.h"
+
+class nsIFrame;
+
+namespace nsStyleTransformMatrix {
+class TransformReferenceBox;
+}
+
+namespace mozilla {
+
+using RayFunction = StyleRayFunction<StyleAngle>;
+
+namespace layers {
+class MotionPathData;
+class PathCommand;
+}  // namespace layers
+
+struct ResolvedMotionPathData {
+  gfx::Point mTranslate;
+  float mRotate;
+  // The delta value between transform-origin and offset-anchor.
+  gfx::Point mShift;
+};
+
+struct RayReferenceData {
+  // The initial position related to the containing block.
+  CSSPoint mInitialPosition;
+  // The rect of the containing block.
+  CSSRect mContainingBlockRect;
+
+  RayReferenceData() = default;
+  explicit RayReferenceData(const nsIFrame* aFrame);
+
+  bool operator==(const RayReferenceData& aOther) const {
+    return mInitialPosition == aOther.mInitialPosition &&
+           mContainingBlockRect == aOther.mContainingBlockRect;
+  }
+};
+
+// The collected information for offset-path. We preprocess the value of
+// offset-path and use this data for resolving motion path.
+struct OffsetPathData {
+  enum class Type : uint8_t {
+    None,
+    Path,
+    Ray,
+  };
+
+  struct PathData {
+    RefPtr<gfx::Path> mGfxPath;
+    bool mIsClosedIntervals;
+  };
+
+  struct RayData {
+    const RayFunction* mRay;
+    RayReferenceData mData;
+  };
+
+  Type mType;
+  union {
+    PathData mPath;
+    RayData mRay;
+  };
+
+  static OffsetPathData None() { return OffsetPathData(); }
+  static OffsetPathData Path(const StyleSVGPathData& aPath,
+                             already_AddRefed<gfx::Path>&& aGfxPath) {
+    const auto& path = aPath._0.AsSpan();
+    return OffsetPathData(std::move(aGfxPath),
+                          !path.empty() && path.rbegin()->IsClosePath());
+  }
+  static OffsetPathData Ray(const RayFunction& aRay,
+                            const RayReferenceData& aData) {
+    return OffsetPathData(&aRay, aData);
+  }
+  static OffsetPathData Ray(const RayFunction& aRay, RayReferenceData&& aData) {
+    return OffsetPathData(&aRay, std::move(aData));
+  }
+
+  bool IsNone() const { return mType == Type::None; }
+  bool IsPath() const { return mType == Type::Path; }
+  bool IsRay() const { return mType == Type::Ray; }
+
+  const PathData& AsPath() const {
+    MOZ_ASSERT(IsPath());
+    return mPath;
+  }
+
+  const RayData& AsRay() const {
+    MOZ_ASSERT(IsRay());
+    return mRay;
+  }
+
+  ~OffsetPathData() {
+    switch (mType) {
+      case Type::Path:
+        mPath.~PathData();
+        break;
+      case Type::Ray:
+        mRay.~RayData();
+        break;
+      default:
+        break;
+    }
+  }
+
+  OffsetPathData(const OffsetPathData& aOther) : mType(aOther.mType) {
+    switch (mType) {
+      case Type::Path:
+        mPath = aOther.mPath;
+        break;
+      case Type::Ray:
+        mRay = aOther.mRay;
+        break;
+      default:
+        break;
+    }
+  }
+
+  OffsetPathData(OffsetPathData&& aOther) : mType(aOther.mType) {
+    switch (mType) {
+      case Type::Path:
+        mPath = std::move(aOther.mPath);
+        break;
+      case Type::Ray:
+        mRay = std::move(aOther.mRay);
+        break;
+      default:
+        break;
+    }
+  }
+
+ private:
+  OffsetPathData() : mType(Type::None) {}
+  OffsetPathData(already_AddRefed<gfx::Path>&& aPath, bool aIsClosed)
+      : mType(Type::Path), mPath{std::move(aPath), aIsClosed} {}
+  OffsetPathData(const RayFunction* aRay, RayReferenceData&& aRef)
+      : mType(Type::Ray), mRay{aRay, std::move(aRef)} {}
+  OffsetPathData(const RayFunction* aRay, const RayReferenceData& aRef)
+      : mType(Type::Ray), mRay{aRay, aRef} {}
+  OffsetPathData& operator=(const OffsetPathData&) = delete;
+  OffsetPathData& operator=(OffsetPathData&&) = delete;
+};
+
+// MotionPathUtils is a namespace class containing utility functions related to
+// processing motion path in the [motion-1].
+// https://drafts.fxtf.org/motion-1/
+class MotionPathUtils final {
+  using TransformReferenceBox = nsStyleTransformMatrix::TransformReferenceBox;
+
+ public:
+  // SVG frames (unlike other frames) have a reference box that can be (and
+  // typically is) offset from the TopLeft() of the frame.
+  //
+  // In motion path, we have to make sure the object is aligned with offset-path
+  // when using content area, so we should tweak the anchor point by a given
+  // offset.
+  static CSSPoint ComputeAnchorPointAdjustment(const nsIFrame& aFrame);
+
+  /**
+   * Generate the motion path transform result. This function may be called on
+   * the compositor thread.
+   */
+  static Maybe<ResolvedMotionPathData> ResolveMotionPath(
+      const OffsetPathData& aPath, const LengthPercentage& aDistance,
+      const StyleOffsetRotate& aRotate, const StylePositionOrAuto& aAnchor,
+      const CSSPoint& aTransformOrigin, TransformReferenceBox&,
+      const CSSPoint& aAnchorPointAdjustment);
+
+  /**
+   * Generate the motion path transform result with |nsIFrame|. This is only
+   * called in the main thread.
+   */
+  static Maybe<ResolvedMotionPathData> ResolveMotionPath(
+      const nsIFrame* aFrame, TransformReferenceBox&);
+
+  /**
+   * Generate the motion path transfrom result with styles and
+   * layers::MotionPathData.
+   * This is only called by the compositor.
+   */
+  static Maybe<ResolvedMotionPathData> ResolveMotionPath(
+      const StyleOffsetPath* aPath, const StyleLengthPercentage* aDistance,
+      const StyleOffsetRotate* aRotate, const StylePositionOrAuto* aAnchor,
+      const Maybe<layers::MotionPathData>& aMotionPathData,
+      TransformReferenceBox&, gfx::Path* aCachedMotionPath);
+
+  /**
+   * Normalize StyleSVGPathData.
+   *
+   * The algorithm of normalization is the same as normalize() in
+   * servo/components/style/values/specified/svg_path.rs
+   * FIXME: Bug 1489392: We don't have to normalize the path here if we accept
+   * the spec issue which would like to normalize svg paths at computed time.
+   * https://github.com/w3c/svgwg/issues/321
+   */
+  static StyleSVGPathData NormalizeSVGPathData(const StyleSVGPathData& aPath);
+
+  /**
+   * Build a gfx::Path from the computed svg path. We should give it a path
+   * builder. If |aPathBuilder| is nullptr, we return null path.
+   * */
+  static already_AddRefed<gfx::Path> BuildPath(const StyleSVGPathData& aPath,
+                                               gfx::PathBuilder* aPathBuilder);
+
+  /**
+   * Get a path builder for compositor.
+   */
+  static already_AddRefed<gfx::PathBuilder> GetCompositorPathBuilder();
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_MotionPathUtils_h