add missing APIs for pathmetric

com.unity.uiwidgets/Runtime/ui2/painting.cs

         public Path() : base(Path_constructor()) {
         }
 
-        private Path(IntPtr ptr) : base(ptr) {
+        public Path(IntPtr ptr) : base(ptr) {
         }
 
         protected override void DisposePtr(IntPtr ptr) {
         }
     }
 
+    public class Tangent {
+        public Tangent(Offset position, Offset vector) {
+            D.assert(position != null);
+            D.assert(vector != null);
+
+            this.position = position;
+            this.vector = vector;
+        }
+
+        public static Tangent fromAngle(Offset position, float angle) {
+            return new Tangent(position, new Offset(Mathf.Cos(angle), Mathf.Sin(angle)));
+        }
+
+        public readonly Offset position;
+
+        public readonly Offset vector;
+
+        public float angle => -Mathf.Atan2(vector.dy, vector.dx);
+    }
+
     public class PathMetric {
         public PathMetric(_PathMeasure measure) {
             D.assert(measure != null);
         public readonly int contourIndex;
 
         readonly _PathMeasure _measure;
+
+        public Tangent getTangentForOffset(float distance) {
+            return _measure.getTangentForOffset(contourIndex, distance);
+        }
+
+        public Path extractPath(float start, float end, bool startWithMoveTo = true) {
+            return _measure.extractPath(contourIndex, start, end, startWithMoveTo);
+        }
+
+        public override string ToString() {
+            return $"{GetType()}: length: {length}, isClosed: {isClosed}, contourIndex: {contourIndex}";
+        }
     }
 
 
             return PathMeasure_length(contourIndex);
         }
 
+        public unsafe Tangent getTangentForOffset(int contourIndex, float distance) {
+            D.assert(contourIndex <= currentContourIndex, () => $"Iterator must be advanced before index {contourIndex} can be used.");
+            float[] posTan = new float[5];
+            fixed (float* posTanPtr = posTan) {
+                PathMeasure_getPosTan(contourIndex, distance, posTanPtr);
+            }
+
+            if (posTan[0] == 0.0f) {
+                return null;
+            }
+            else {
+                return new Tangent(
+                    new Offset(posTan[1], posTan[2]),
+                    new Offset(posTan[3], posTan[4])
+                    );
+            }
+        }
+
+        public Path extractPath(int contourIndex, float start, float end, bool startWithMoveTo = true) {
+            D.assert(contourIndex <= currentContourIndex,
+                () => $"Iterator must be advanced before index {contourIndex} can be used.");
+            IntPtr pathPtr = PathMeasure_getSegment(contourIndex, start, end, startWithMoveTo);
+            return new Path(pathPtr);
+        }
+
         public bool isClosed(int contourIndex) {
             D.assert(contourIndex <= currentContourIndex, () => $"Iterator must be advanced before index {contourIndex} can be used.");
             return PathMeasure_isClosed(contourIndex);
 
         [DllImport(NativeBindings.dllName)]
         static extern float PathMeasure_length(int contourIndex);
+
+        [DllImport(NativeBindings.dllName)]
+        static extern unsafe void PathMeasure_getPosTan(int contourIndex, float distance, float* posTan);
+
+        [DllImport(NativeBindings.dllName)]
+        static extern IntPtr PathMeasure_getSegment(int contourIndex, float start, float end,
+            bool startWithMoveTo);
 
         
         [DllImport(NativeBindings.dllName)]

engine/src/lib/ui/painting/path.h

     return fml::MakeRefCounted<CanvasPath>();
   }
 
+  static fml::RefPtr<CanvasPath> CreateFrom(const SkPath& src) {
+    fml::RefPtr<CanvasPath> path = CanvasPath::CreateNew();
+    path->path_ = src;
+    return path;
+  }
+
   int getFillType();
   void setFillType(int fill_type);
 

engine/src/lib/ui/painting/path_measure.cc

   return -1;
 }
 
+void CanvasPathMeasure::getPosTan(int contour_index, float distance, float* posTan) {
+  posTan[0] = 0;
+  if (static_cast<std::vector<sk_sp<SkContourMeasure>>::size_type>(
+          contour_index) >= measures_.size()) {
+    return;
+  }
+
+  SkPoint pos;
+  SkVector tan;
+  bool success = measures_[contour_index]->getPosTan(distance, &pos, &tan);
+
+  if (success) {
+    posTan[0] = 1;  // dart code will check for this for success
+    posTan[1] = pos.x();
+    posTan[2] = pos.y();
+    posTan[3] = tan.x();
+    posTan[4] = tan.y();
+  }
+}
+
+fml::RefPtr<CanvasPath> CanvasPathMeasure::getSegment(int contour_index,
+                                   float start_d, float stop_d,
+                                   bool start_with_move_to) {
+  if (static_cast<std::vector<sk_sp<SkContourMeasure>>::size_type>(
+          contour_index) >= measures_.size()) {
+		return CanvasPath::CreateNew();
+  }
+  SkPath dst;
+  bool success = measures_[contour_index]->getSegment(start_d, stop_d, &dst,
+                                                      start_with_move_to);
+  if (!success) {
+    return CanvasPath::CreateNew();
+  } else {
+    return CanvasPath::CreateFrom(dst);
+  }
+}
+
 bool CanvasPathMeasure::isClosed(int contour_index) {
   if (static_cast<std::vector<sk_sp<SkContourMeasure>>::size_type>(
           contour_index) < measures_.size()) {
 
 UIWIDGETS_API(float) PathMeasure_length(PathMeasure* ptr, int contourIndex) {
   return ptr->getLength(contourIndex);
+}
+
+UIWIDGETS_API(void)
+PathMeasure_getPosTan(PathMeasure* ptr, int contour_index, float distance,
+                      float* posTan) {
+  ptr->getPosTan(contour_index, distance, posTan);
+}
+
+UIWIDGETS_API(CanvasPath*)
+PathMeasure_getSegment(PathMeasure* ptr, int contour_index, float start_d,
+	float stop_d,
+	bool start_with_move_to) {
+  const auto path = ptr->getSegment(contour_index, start_d, stop_d, start_with_move_to);
+  path->AddRef();
+  return path.get();
 }
 
 UIWIDGETS_API(bool) PathMeasure_isClosed(PathMeasure* ptr, int contourIndex) {

engine/src/lib/ui/painting/path_measure.h

 
   void setPath(const CanvasPath* path, bool isClosed);
   float getLength(int contour_index);
+  void getPosTan(int contour_index, float distance, float* posTan);
+  fml::RefPtr<CanvasPath> getSegment(int contour_index, float start_d,
+                  float stop_d, bool start_with_move_to);
   bool isClosed(int contour_index);
   bool nextContour();