Fixed `Path_Tick_Scaled`, `Path_Tick_Scaled_Stroke_8px` and `Path_Expander_With_Border` for Skia

src/Skia/Perspex.Skia/DrawingContextImpl.cs

@@ -37,18 +37,13 @@ namespace Perspex.Skia
         public void DrawGeometry(Brush brush, Pen pen, Geometry geometry)
         {
             var impl = ((StreamGeometryImpl) geometry.PlatformImpl);
-            var oldTransform = Transform;
-            if (!impl.Transform.IsIdentity)
-                Transform = impl.Transform*Transform;
-            
             var size = geometry.Bounds.Size;
             using(var fill = brush!=null?CreateBrush(brush, size):null)
             using (var stroke = pen?.Brush != null ? CreateBrush(pen, size) : null)
             {
-                MethodTable.Instance.DrawGeometry(Handle, impl.Path.Handle, fill != null ? fill.Brush : null,
+                MethodTable.Instance.DrawGeometry(Handle, impl.EffectivePath, fill != null ? fill.Brush : null,
                     stroke != null ? stroke.Brush : null, impl.FillRule == FillRule.EvenOdd);
             }
-            Transform = oldTransform;
         }
 
         unsafe NativeBrushContainer CreateBrush(Brush brush, Size targetSize)
@@ -196,14 +191,7 @@ namespace Perspex.Skia
                 if(_currentTransform == value)
                     return;
                 _currentTransform = value;
-                _fmatrix[0] = (float)value.M11;
-                _fmatrix[1] = (float)value.M21;
-                _fmatrix[2] = (float)value.M31;
-
-                _fmatrix[3] = (float)value.M12;
-                _fmatrix[4] = (float)value.M22;
-                _fmatrix[5] = (float)value.M32;
-                MethodTable.Instance.SetTransform(Handle, _fmatrix);
+                MethodTable.Instance.SetTransform(Handle, value);
             } 
         }
     }

src/Skia/Perspex.Skia/MethodTable.cs

@@ -47,9 +47,9 @@ namespace Perspex.Skia
         public _PopClip PopClip;
 
         [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
-        public delegate void _SetTransform(IntPtr ctx, float[] matrix6);
+        public delegate void _SetTransform(IntPtr ctx, void* matrix6);
 
-        public _SetTransform SetTransform;
+        public _SetTransform SetTransformNative;
 
         [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
         public delegate void _DrawLine(IntPtr ctx, void* brush, float x1, float y1, float x2, float y2);
@@ -66,6 +66,11 @@ namespace Perspex.Skia
 
         public _DisposePath DisposePath;
 
+        [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+        public delegate IntPtr _TransformPath(IntPtr path, void* matrix6);
+
+        public _TransformPath TransformPathNative;
+
         [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
         public delegate void _DrawGeometry(IntPtr ctx, IntPtr path, void* fill, void* stroke, bool useEvenOdd);
 
@@ -185,10 +190,34 @@ namespace Perspex.Skia
             typeof (_RebuildFormattedText),
             typeof (_DestroyFormattedText),
             typeof (_DrawFormattedText),
-            typeof (_SetOption)
+            typeof (_SetOption),
+            typeof (_TransformPath)
         };
 
+        void ConvertMatrix(Matrix value, float* target)
+        {
+            target[0] = (float)value.M11;
+            target[1] = (float)value.M21;
+            target[2] = (float)value.M31;
+
+            target[3] = (float)value.M12;
+            target[4] = (float)value.M22;
+            target[5] = (float)value.M32;
+        }
 
+        public unsafe IntPtr TransformPath(IntPtr path, Matrix matrix)
+        {
+            var tmp = stackalloc float[6];
+            ConvertMatrix(matrix, tmp);
+            return TransformPathNative(path, tmp);
+        }
+
+        public unsafe void SetTransform(IntPtr ctx, Matrix matrix)
+        {
+            var tmp = stackalloc float[6];
+            ConvertMatrix(matrix, tmp);
+            SetTransformNative(ctx, tmp);
+        }
 
         protected MethodTable(IntPtr methodTable)
         {

src/Skia/Perspex.Skia/PerspexHandleHolder.cs

@@ -44,4 +44,63 @@ namespace Perspex.Skia
             Dispose();
         }
     }
+
+    class RefCountable<T> : IDisposable where T : PerspexHandleHolder
+    {
+        class Shared
+        {
+            public readonly T Target;
+            private int _refCount = 1;
+
+            public Shared(T target)
+            {
+                Target = target;
+            }
+
+            public void AddRef() => _refCount++;
+            public void Release()
+            {
+                _refCount--;
+                if (_refCount <= 0)
+                    Target.Dispose();
+            }
+        }
+
+        public bool IsDisposed => _shared == null;
+        private Shared _shared;
+        public void CheckDisposed()
+        {
+            if (IsDisposed)
+                throw new ObjectDisposedException(GetType().FullName);
+        }
+
+        public IntPtr Handle
+        {
+            get
+            {
+                CheckDisposed();
+                return _shared.Target.Handle;
+            }
+        }
+
+        public RefCountable(T handle)
+        {
+            _shared = new Shared(handle);
+        }
+
+        public RefCountable(RefCountable<T> other)
+        {
+            other._shared.Target.CheckDisposed();
+            other._shared.AddRef();
+            _shared = other._shared;
+        }
+
+        public RefCountable<T> Clone() => new RefCountable<T>(this);
+
+        public void Dispose()
+        {
+            _shared?.Release();
+            _shared = null;
+        }
+    }
 }

src/Skia/Perspex.Skia/StreamGeometryImpl.cs

@@ -41,7 +41,11 @@ namespace Perspex.Skia
 
     class StreamGeometryImpl : IStreamGeometryImpl
     {
-        public SkPath Path;
+        RefCountable<SkPath> _path;
+        RefCountable<SkPath> _transformedPath;
+        private Matrix _transform = Matrix.Identity;
+        
+        public IntPtr EffectivePath => (_transformedPath ?? _path).Handle;
 
         public Rect GetRenderBounds(double strokeThickness)
         {
@@ -51,11 +55,35 @@ namespace Perspex.Skia
 
         public Rect Bounds { get; private set; }
 
-        public Matrix Transform { get; set; } = Matrix.Identity;
+        public Matrix Transform
+        {
+            get { return _transform; }
+            set
+            {
+                if(_transform == value)
+                    return;
+                _transform = value;
+                ApplyTransform();
+            }
+        }
+
+        void ApplyTransform()
+        {
+            if(_path == null)
+                return;
+            if (_transformedPath != null)
+            {
+                _transformedPath.Dispose();
+                _transformedPath = null;
+            }
+            if (!_transform.IsIdentity)
+                _transformedPath =
+                    new RefCountable<SkPath>(new SkPath(MethodTable.Instance.TransformPath(_path.Handle, Transform)));
+        }
 
         public IStreamGeometryImpl Clone()
         {
-            return new StreamGeometryImpl() {Path = Path, Transform = Transform, Bounds = Bounds};
+            return new StreamGeometryImpl {_path = _path?.Clone(), _transformedPath = _transformedPath?.Clone(), _transform = Transform, Bounds = Bounds};
         }
 
         public IStreamGeometryContextImpl Open()
@@ -77,7 +105,11 @@ namespace Perspex.Skia
             {
                 var arr = _elements.ToArray();
                 SkRect rc;
-                _geometryImpl.Path = new SkPath(MethodTable.Instance.CreatePath(arr, arr.Length, out rc));
+                _geometryImpl._path?.Dispose();
+                _geometryImpl._path =
+                    new RefCountable<SkPath>(new SkPath(MethodTable.Instance.CreatePath(arr, arr.Length, out rc)));
+                _geometryImpl.ApplyTransform();
+
                 _geometryImpl.Bounds = rc.ToRect();
 
             }

tests/Perspex.RenderTests/Shapes/PathTests.cs

@@ -46,11 +46,7 @@ namespace Perspex.Direct2D1.RenderTests.Shapes
             CompareImages();
         }
 
-#if PERSPEX_SKIA
-        [Fact(Skip = "FIXME")]
-#else
         [Fact]
-#endif
         public void Path_Tick_Scaled()
         {
             Decorator target = new Decorator
@@ -73,11 +69,7 @@ namespace Perspex.Direct2D1.RenderTests.Shapes
             CompareImages();
         }
 
-#if PERSPEX_SKIA
-        [Fact(Skip = "FIXME")]
-#else
         [Fact]
-#endif
         public void Path_Tick_Scaled_Stroke_8px()
         {
             Decorator target = new Decorator
@@ -100,11 +92,7 @@ namespace Perspex.Direct2D1.RenderTests.Shapes
             CompareImages();
         }
 
-#if PERSPEX_SKIA
-        [Fact(Skip = "FIXME")]
-#else
         [Fact]
-#endif
         public void Path_Expander_With_Border()
         {
             Decorator target = new Decorator