Add TryGetSegment

src/Avalonia.Headless/HeadlessPlatformRenderInterface.cs

@@ -142,6 +142,12 @@ namespace Avalonia.Headless
                 tangent = new Point();
                 return false;
             }
+
+            public bool TryGetSegment(float startDistance, float stopDistance, bool startOnBeginFigure, out IGeometryImpl segmentGeometry)
+            {
+                segmentGeometry = null;
+                return false;
+            }
         }
 
         class HeadlessTransformedGeometryStub : HeadlessGeometryStub, ITransformedGeometryImpl

src/Avalonia.Visuals/Platform/IGeometryImpl.cs

@@ -73,5 +73,18 @@ namespace Avalonia.Platform
         /// <param name="tangent">The tangent in the specified distance.</param>
         /// <returns>If there's valid point and tangent at the specified distance.</returns>
         bool TryGetPointAndTangentAtDistance(double distance, out Point point, out Point tangent);
+        
+        /// <summary>
+        /// Attempts to get the corresponding path segment
+        /// given by the two distances specified.
+        /// Imagine it like snipping a part of the current
+        /// geometry.
+        /// </summary>
+        /// <param name="startDistance">The contour distance to start snipping from.</param>
+        /// <param name="stopDistance">The contour distance to stop snipping to.</param>
+        /// <param name="startOnBeginFigure">If ture, the resulting snipped path will start with a BeginFigure call.</param>
+        /// <param name="segmentGeometry">The resulting snipped path.</param>
+        /// <returns>If the snipping operation is successful.</returns>
+        bool TryGetSegment (float startDistance, float stopDistance, bool startOnBeginFigure, out IGeometryImpl segmentGeometry);
     }
 }

src/Skia/Avalonia.Skia/GeometryImpl.cs

@@ -138,6 +138,28 @@ namespace Avalonia.Skia
             return res;
         }
 
+        public bool TryGetSegment(float startDistance, float stopDistance, bool startOnBeginFigure, out IGeometryImpl segmentGeometry)
+        {
+            if (_pathCache.CachePathMeasure is null)
+            {
+                segmentGeometry = null;
+                return false;
+            }
+            
+            segmentGeometry = null;
+
+            SKPath _skPathSegment = null;
+
+            var res = _pathCache.CachePathMeasure.GetSegment(startDistance, stopDistance, _skPathSegment, startOnBeginFigure);
+
+            if (res)
+            {
+                segmentGeometry = new StreamGeometryImpl(_skPathSegment);
+            }
+            
+            return res;
+        }
+
         /// <summary>
         /// Invalidate all caches. Call after chaining path contents.
         /// </summary>

src/Windows/Avalonia.Direct2D1/Media/GeometryImpl.cs

@@ -82,6 +82,15 @@ namespace Avalonia.Direct2D1.Media
             return false;
         }
 
+        public bool TryGetSegment(float startDistance, float stopDistance, bool startOnBeginFigure, out IGeometryImpl segmentGeometry)
+        {
+            // Direct2D doesnt have this too sadly.
+            Logger.TryGet(LogEventLevel.Warning, LogArea.Visual)?.Log(this, "TryGetSegment is not available in Direct2D.");
+
+            segmentGeometry = null;
+            return false;
+        }
+
         protected virtual Geometry GetSourceGeometry() => Geometry;
     }
 }

tests/Avalonia.UnitTests/MockStreamGeometryImpl.cs

@@ -84,6 +84,12 @@ namespace Avalonia.UnitTests
             return false;
         }
 
+        public bool TryGetSegment(float startDistance, float stopDistance, bool startOnBeginFigure, out IGeometryImpl segmentGeometry)
+        {
+            segmentGeometry = null;
+            return false;
+        }
+
         class MockStreamGeometryContext : IStreamGeometryContextImpl
         {
             private List<Point> points = new List<Point>();

tests/Avalonia.Visuals.UnitTests/VisualTree/MockRenderInterface.cs

@@ -163,6 +163,11 @@ namespace Avalonia.Visuals.UnitTests.VisualTree
                 throw new NotImplementedException();
             }
 
+            public bool TryGetSegment(float startDistance, float stopDistance, bool startOnBeginFigure, out IGeometryImpl segmentGeometry)
+            {
+                throw new NotImplementedException();
+            }
+
             class MockStreamGeometryContext : IStreamGeometryContextImpl
             {
                 private List<Point> points = new List<Point>();