Merge branch 'master' into 'dragdrop_fix'

# Conflicts:
#   Runtime/rendering/proxy_box.cs

Runtime/Resources/UIWidgets_canvas.shader

     }
 
     CGINCLUDE
-    float2 _viewSize;
+    float4 _viewport;
-    float4 _innerCol;
-    float4 _outerCol;
+    half4 _innerCol;
+    half4 _outerCol;
+    half2 _mf_imgInc; // _mf stands for mask filter
+    int _mf_radius;
+    half _mf_kernel[25];
+        
     struct appdata_t {
         float4 vertex : POSITION;
         float2 tcoord : TEXCOORD0;
         v2f o;
         o.ftcoord = v.tcoord;
         o.fpos = v.vertex;
+        
+        float x = v.vertex.x - _viewport.x;
+        float y = v.vertex.y - _viewport.y;
-        o.vertex = float4(2.0 * v.vertex.x / _viewSize.x - 1.0, 2.0 * v.vertex.y / _viewSize.y - 1.0, 0, 1);
+        o.vertex = float4(2.0 * x / _viewport.z - 1.0, 2.0 * y / _viewport.w - 1.0, 0, 1);
-        o.vertex = float4(2.0 * v.vertex.x / _viewSize.x - 1.0, 1.0 - 2.0 * v.vertex.y / _viewSize.y, 0, 1);
+        o.vertex = float4(2.0 * x / _viewport.z - 1.0, 1.0 - 2.0 * y / _viewport.w, 0, 1);
     #endif
 
         return o;
         float2 pt = (mul(_paintMat, float3(i.fpos, 1.0))).xy;
         float d = clamp((sdroundrect(pt, _extent, _radius) + _feather * 0.5) / _feather, 0.0, 1.0);
-        float4 color = lerp(_innerCol, _outerCol, d);
+        half4 color = lerp(_innerCol, _outerCol, d);
-        return float4(0, 0, 0, 0);
+        return half4(0, 0, 0, 0);
-        float4 color = tex2D(_tex, i.ftcoord);
+        half4 color = tex2D(_tex, i.ftcoord);
-        color = float4(color.xyz * color.w, color.w);
+        color = half4(color.xyz * color.w, color.w);
-         float4 color = tex2D(_tex, i.ftcoord);
+         half4 color = tex2D(_tex, i.ftcoord);
-         color = float4(color.xyz * _innerCol.w, color.w);
+         color = half4(color.xyz * _innerCol.w, color.w);
-         float4 color = tex2D(_tex, i.ftcoord);
-         color = float4(1, 1, 1, color.w) * _innerCol; // tint color
-         color = float4(color.xyz * color.w, color.w);
+         half4 color = tex2D(_tex, i.ftcoord);
+         color = half4(1, 1, 1, color.w) * _innerCol; // tint color
+         color = half4(color.xyz * color.w, color.w);
+         return color;
+    }
+    
+    fixed4 frag_mf (v2f i) : SV_Target {
+         half4 color = half4(0, 0, 0, 0);
+         
+         float2 coord = i.ftcoord - _mf_radius * _mf_imgInc;
+         int width = _mf_radius * 2 + 1;
+         for (int i = 0; i < width; i++) {
+            color += tex2D(_tex, coord) * _mf_kernel[i];
+            coord += _mf_imgInc;
+         }
+    
+         color = color * _innerCol; // tint color
+         color = half4(color.xyz * _innerCol.w, color.w);
          return color;
     }
     
 
             CGPROGRAM
             #pragma fragment frag_texfont
+            ENDCG
+        }
+        
+        Pass { // 11, mask filter 
+            CGPROGRAM
+            #pragma fragment frag_mf
             ENDCG
         }
     }

Runtime/painting/border_radius.cs

                 return hashCode;
             }
         }
+        
+        public static bool operator ==(BorderRadius a, BorderRadius b) {
+            return Equals(a, b);
+        }
+
+        public static bool operator !=(BorderRadius a, BorderRadius b) {
+            return !Equals(a, b);
+        }
 
         public override string ToString() {
             string visual = null;

Runtime/painting/box_shadow.cs

         public Paint toPaint() {
             return new Paint {
                 color = this.color,
-                //blurSigma = this.blurSigma, TODO
+                maskFilter = MaskFilter.blur(BlurStyle.normal, this.blurSigma)
             };
         }
 

Runtime/painting/decoration_image.cs

             }
 
             fit = fit ?? (centerSlice == null ? BoxFit.scaleDown : BoxFit.fill);
-            D.assert(centerSlice == null || (fit != BoxFit.none && fit != BoxFit.cover));
+            D.assert(centerSlice == null || (fit != BoxFit.none && fit != BoxFit.cover),
+                $"centerSlice was used with a BoxFit {fit} that is not supported.");            
             FittedSizes fittedSizes = FittedSizes.applyBoxFit(fit.Value, inputSize / scale, outputSize);
             Size sourceSize = fittedSizes.source * scale;
             Size destinationSize = fittedSizes.destination;
                 D.assert(sourceSize == inputSize,
-                    "centerSlice was used with a BoxFit that does not guarantee that the image is fully visible.");
+                    $"centerSlice was used with a BoxFit {fit} that does not guarantee that the image is fully visible.");
             }
 
             if (repeat != ImageRepeat.noRepeat && destinationSize == outputSize) {

Runtime/rendering/proxy_box.cs

             Color color = null,
             Color shadowColor = null
         ) : base(child: child,
-            elevation : elevation,
+            elevation: elevation,
             color: color,
             shadowColor: shadowColor ?? new Color(0xFF000000),
             clipper: clipper,

Runtime/ui/painting/canvas_impl.cs

         readonly MeshPool _meshPool;
         readonly List<RenderLayer> _layers = new List<RenderLayer>();
         int _saveCount;
-        
+
-        
+
-                0, 4, 1, 1, 4, 5,
-                0, 1, 4, 1, 5, 4,
-                1, 5, 2, 2, 5, 6,
-                1, 2, 5, 2, 6, 5,
-                2, 6, 3, 3, 6, 7,
-                2, 3, 6, 3, 7, 6,
-                4, 8, 5, 5, 8, 9,
-                4, 5, 8, 5, 9, 8,
-                5, 9, 6, 6, 9, 10,
-                5, 6, 9, 6, 10, 9,
-                6, 10, 7, 7, 10, 11,
-                6, 7, 10, 7, 11, 10,
-                8, 12, 9, 9, 12, 13,
-                8, 9, 12, 9, 13, 12,
-                9, 13, 10, 10, 13, 14,
-                9, 10, 13, 10, 14, 13,
-                10, 14, 11, 11, 14, 15,
-                10, 11, 14, 11, 15, 14,
+            0, 4, 1, 1, 4, 5,
+            0, 1, 4, 1, 5, 4,
+            1, 5, 2, 2, 5, 6,
+            1, 2, 5, 2, 6, 5,
+            2, 6, 3, 3, 6, 7,
+            2, 3, 6, 3, 7, 6,
+            4, 8, 5, 5, 8, 9,
+            4, 5, 8, 5, 9, 8,
+            5, 9, 6, 6, 9, 10,
+            5, 6, 9, 6, 10, 9,
+            6, 10, 7, 7, 10, 11,
+            6, 7, 10, 7, 11, 10,
+            8, 12, 9, 9, 12, 13,
+            8, 9, 12, 9, 13, 12,
+            9, 13, 10, 10, 13, 14,
+            9, 10, 13, 10, 14, 13,
+            10, 14, 11, 11, 14, 15,
+            10, 11, 14, 11, 15, 14,
         };
 
         public CommandBufferCanvas(RenderTexture renderTexture, float devicePixelRatio, MeshPool meshPool) {
         }
 
         public void saveLayer(Rect bounds, Paint paint) {
+            D.assert(bounds != null);
+            D.assert(bounds.width > 0);
+            D.assert(bounds.height > 0);
+            D.assert(paint != null);
+
-                (float) bounds.width * XformUtils.getScaleX(state.xform) * this._devicePixelRatio);
+                (float) bounds.width *
+                XformUtils.getScaleX(state.xform) *
+                this._devicePixelRatio);
+            textureWidth = Mathf.Max(textureWidth, 1);
+
-                (float) bounds.height * XformUtils.getScaleY(state.xform) * this._devicePixelRatio);
+                (float) bounds.height *
+                XformUtils.getScaleY(state.xform) *
+                this._devicePixelRatio);
+            textureHeight = Mathf.Max(textureHeight, 1);
 
             var parentLayer = this._getLayer();
             var layer = new RenderLayer {
 
             parentLayer.layers.Add(layer);
             this._layers.Add(layer);
-
-            state = this._getState();
-            XformUtils.transformTranslate(state.xform, (float) -bounds.left, (float) -bounds.top);
         }
 
         public void restore() {
             var vertices = new List<Vector3>(4);
             var uv = new List<Vector2>(4);
 
-            float uvx0 = 0.0f;
-            float uvx1 = 1.0f;
-            float uvy0 = 1.0f;
-            float uvy1 = 0.0f;
+            const float uvx0 = 0.0f;
+            const float uvx1 = 1.0f;
+            const float uvy0 = 1.0f;
+            const float uvy1 = 0.0f;
 
             float x, y;
             var bounds = layer.layerBounds;
                 (float) bounds.right, (float) bounds.top);
             vertices.Add(new Vector2(x, y));
             uv.Add(new Vector2(uvx1, uvy0));
-            
+
             var mesh = new MeshMesh(vertices, _imageTriangles, uv);
 
             if (!this._applyClip(mesh.bounds)) {
 
         MaterialPropertyBlock _getMatProps(Paint paint, float alpha = 1.0f) {
             var properties = new MaterialPropertyBlock();
-            properties.SetVector("_viewSize", this._getViewSize());
-
-            if (paint.shader is Gradient) {
-                var gradient = (Gradient) paint.shader;
+            properties.SetVector("_viewport", this._getViewport());
+            if (paint.shader is Gradient gradient) {
                 var innerCol = gradient.innerColor;
                 var outerCol = gradient.outerColor;
 
 
         bool _applyClip(Rect queryBounds) {
             var layer = this._getLayer();
-            var layerBounds = Rect.fromLTRB(0, 0, layer.layerBounds.width, layer.layerBounds.height);
+            var layerBounds = layer.layerBounds;
             ReducedClip reducedClip = new ReducedClip(layer.clipStack, layerBounds, queryBounds);
             if (reducedClip.isEmpty()) {
                 return false;
             var deviceScissor = Rect.fromLTRB(
-                scissor.left, layerBounds.height - scissor.bottom,
-                scissor.right, layerBounds.height - scissor.top
+                scissor.left - layerBounds.left, layerBounds.bottom - scissor.bottom,
+                scissor.right - layerBounds.left, layerBounds.bottom - scissor.top
-                deviceScissor = deviceScissor,
+                deviceScissor = deviceScissor.roundOut(),
-                properties.SetVector("_viewSize", this._getViewSize());
+                properties.SetVector("_viewport", this._getViewport());
 
                 var boundsMesh = new MeshMesh(reducedClip.scissor);
                 this._getLayer().draws.Add(new RenderDraw {
             return true;
         }
 
-        public void drawPath(Path path, Paint paint) {
+        RenderLayer _createMaskLayer(Path path, Paint paint, RenderLayer parentLayer, Rect maskBounds) {
+            var textureWidth = Mathf.CeilToInt(
+                (float) maskBounds.width * this._devicePixelRatio);
+            textureWidth = Mathf.Max(1, textureWidth);
+            
+            var textureHeight = Mathf.
+                CeilToInt((float) maskBounds.height * this._devicePixelRatio);
+            textureHeight = Mathf.Max(1, textureHeight);
+
+            var maskLayer = new RenderLayer {
+                rtID = Shader.PropertyToID("_rtID_" + this._layers.Count + "_" + parentLayer.layers.Count),
+                width = textureWidth,
+                height = textureHeight,
+                layerBounds = maskBounds,
+            };
+
+            parentLayer.layers.Add(maskLayer);
+            this._layers.Add(maskLayer);
+
+            var parentState = parentLayer.states.Last();
+            var maskState = maskLayer.states.Last();
+            XformUtils.transformCopy(maskState.xform, parentState.xform);
+
+            var maskPaint = Paint.shapeOnly(paint);
+            this._drawPath(path, maskPaint);
+
+            var removed = this._layers.removeLast();
+            D.assert(removed == maskLayer);
+
+            return maskLayer;
+        }
+
+        RenderLayer _createBlurLayer(RenderLayer maskLayer, float sigma, RenderLayer parentLayer) {
+            sigma = BlurUtils.adjustSigma(sigma, out var scaleFactor, out var radius);
+
+            var textureWidth = Mathf.CeilToInt((float) maskLayer.width / scaleFactor);
+            textureWidth = Mathf.Max(1, textureWidth);
+            
+            var textureHeight = Mathf.CeilToInt((float) maskLayer.height / scaleFactor);
+            textureHeight = Mathf.Max(1, textureHeight);
+
+            var blurXLayer = new RenderLayer {
+                rtID = Shader.PropertyToID("_rtID_" + this._layers.Count + "_" + parentLayer.layers.Count),
+                width = textureWidth,
+                height = textureHeight,
+                layerBounds = maskLayer.layerBounds,
+            };
+            
+            parentLayer.layers.Add(blurXLayer);
+            
+            var blurYLayer = new RenderLayer {
+                rtID = Shader.PropertyToID("_rtID_" + this._layers.Count + "_" + parentLayer.layers.Count),
+                width = textureWidth,
+                height = textureHeight,
+                layerBounds = maskLayer.layerBounds,
+            };
+            
+            parentLayer.layers.Add(blurYLayer);
+            
+            var vertices = new List<Vector3>(4);
+            var uv = new List<Vector2>(4);
+
+            const float uvx0 = 0.0f;
+            const float uvx1 = 1.0f;
+            const float uvy0 = 1.0f;
+            const float uvy1 = 0.0f;
+
+            vertices.Add(new Vector2((float) maskLayer.layerBounds.left, (float) maskLayer.layerBounds.top));
+            uv.Add(new Vector2(uvx0, uvy0));
+            vertices.Add(new Vector2((float) maskLayer.layerBounds.left, (float) maskLayer.layerBounds.bottom));
+            uv.Add(new Vector2(uvx0, uvy1));
+            vertices.Add(new Vector2((float) maskLayer.layerBounds.right, (float) maskLayer.layerBounds.bottom));
+            uv.Add(new Vector2(uvx1, uvy1));
+            vertices.Add(new Vector2((float) maskLayer.layerBounds.right, (float) maskLayer.layerBounds.top));
+            uv.Add(new Vector2(uvx1, uvy0));
+
+            var blurMesh = new MeshMesh(vertices, _imageTriangles, uv);
+
+            var emptyPaint = new Paint();
+
+            var kernel = BlurUtils.get1DGaussianKernel(sigma, radius);
+
+            this._layers.Add(blurXLayer);
+
+            {
+                var mat = this._getMat(emptyPaint);
+                var properties = this._getMatPropsForImage(null, emptyPaint);
+
+                properties.SetFloat("_mf_radius", radius);
+                properties.SetVector("_mf_imgInc", new Vector2(1f / textureWidth, 0));
+                properties.SetFloatArray("_mf_kernel", kernel);
+
+                blurXLayer.draws.Add(
+                    new RenderDraw {
+                        mesh = blurMesh,
+                        pass = CanvasShaderPass.mfPass0,
+                        material = mat,
+                        properties = properties,
+                        layer = maskLayer
+                    }
+                );
+            }
+
+
+            var removed = this._layers.removeLast();
+            D.assert(removed == blurXLayer);
+
+            this._layers.Add(blurYLayer);
+
+            {
+                var mat = this._getMat(emptyPaint);
+                var properties = this._getMatPropsForImage(null, emptyPaint);
+
+                properties.SetFloat("_mf_radius", radius);
+                properties.SetVector("_mf_imgInc", new Vector2(0, -1f / textureHeight));
+                properties.SetFloatArray("_mf_kernel", kernel);
+
+                blurYLayer.draws.Add(
+                    new RenderDraw {
+                        mesh = blurMesh,
+                        pass = CanvasShaderPass.mfPass0,
+                        material = mat,
+                        properties = properties,
+                        layer = blurXLayer
+                    }
+                );
+            }
+
+            removed = this._layers.removeLast();
+            D.assert(removed == blurYLayer);
+            
+            return blurYLayer;
+        }
+        
+        void _drawPathWithMaskFilter(Path path, Paint paint, MaskFilter maskFilter) {
+            var layer = this._getLayer();
+            var clipBounds = layer.layerBounds;
+
+            Rect stackBounds;
+            bool iior;
+            layer.clipStack.getBounds(out stackBounds, out iior);
+
+            if (stackBounds != null) {
+                clipBounds = clipBounds.intersect(stackBounds);
+            }
+
+            if (clipBounds.isEmpty) {
+                return;
+            }
+
+            var state = this._getState();
+            var cache = path.flatten(state.xform, this._devicePixelRatio);
+
+            bool convex;
+            var mesh = cache.getFillMesh(out convex);
+            var meshBounds = mesh.bounds;
+
+            float sigma = XformUtils.mapRadius(state.xform, (float) maskFilter.sigma);
+            if (sigma <= 0) {
+                return;
+            }
+
+            float sigma3 = 3 * sigma;
+            var maskBounds = meshBounds.inflate(sigma3);
+            maskBounds = maskBounds.intersect(clipBounds.inflate(sigma3));
+            if (maskBounds.isEmpty) {
+                return;
+            }
+
+            var maskLayer = this._createMaskLayer(path, paint, layer, maskBounds);
+
+            var blurLayer = this._createBlurLayer(maskLayer, sigma, layer);
+
+            var vertices = new List<Vector3>(4);
+            var uv = new List<Vector2>(4);
+
+            const float uvx0 = 0.0f;
+            const float uvx1 = 1.0f;
+            const float uvy0 = 1.0f;
+            const float uvy1 = 0.0f;
+
+            vertices.Add(new Vector2((float) maskBounds.left, (float) maskBounds.top));
+            uv.Add(new Vector2(uvx0, uvy0));
+            vertices.Add(new Vector2((float) maskBounds.left, (float) maskBounds.bottom));
+            uv.Add(new Vector2(uvx0, uvy1));
+            vertices.Add(new Vector2((float) maskBounds.right, (float) maskBounds.bottom));
+            uv.Add(new Vector2(uvx1, uvy1));
+            vertices.Add(new Vector2((float) maskBounds.right, (float) maskBounds.top));
+            uv.Add(new Vector2(uvx1, uvy0));
+
+            var blurMesh = new MeshMesh(vertices, _imageTriangles, uv);
+
+            if (!this._applyClip(blurMesh.bounds)) {
+                return;
+            }
+
+            var mat = this._getMat(paint);
+            var properties = this._getMatPropsForImage(null, paint);
+
+            layer.draws.Add(
+                new RenderDraw {
+                    mesh = blurMesh,
+                    pass = CanvasShaderPass.texrtPass0,
+                    material = mat,
+                    properties = properties,
+                    layer = blurLayer
+                }
+            );
+        }
+
+        void _drawPath(Path path, Paint paint) {
             D.assert(path != null);
             D.assert(paint != null);
 
             }
         }
 
+        public void drawPath(Path path, Paint paint) {
+            D.assert(path != null);
+            D.assert(paint != null);
+
+            if (paint.maskFilter != null) {
+                this._drawPathWithMaskFilter(path, paint, paint.maskFilter);
+                return;
+            }
+
+            this._drawPath(path, paint);
+        }
+
         public void drawImage(Image image, Offset offset, Paint paint) {
             D.assert(image != null);
             D.assert(offset != null);
                 paint);
         }
 
-        Vector2 _getViewSize() {
+        Vector4 _getViewport() {
-            return new Vector2((float) layer.layerBounds.width, (float) layer.layerBounds.height);
+            return new Vector4(
+                (float) layer.layerBounds.left,
+                (float) layer.layerBounds.top,
+                (float) layer.layerBounds.width,
+                (float) layer.layerBounds.height);
         }
 
         static Dictionary<BlendMode, Material> _materials = new Dictionary<BlendMode, Material>();
 
         MaterialPropertyBlock _getMatPropsForImage(Texture image, Paint paint) {
             var properties = new MaterialPropertyBlock();
-            properties.SetVector("_viewSize", this._getViewSize());
+            properties.SetVector("_viewport", this._getViewport());
             properties.SetVector("_innerCol", _color(paint.color));
             if (image != null) {
                 image.filterMode = paint.filterMode;
             XformUtils.transformTranslate(xform, (float) offset.dx, (float) offset.dy);
             XformUtils.transformMultiply(xform, state.xform); // xform = state.xform * xform
 
-            var scale = XformUtils.getAverageScale(xform) * this._devicePixelRatio;            
+            var scale = XformUtils.getAverageScale(xform) * this._devicePixelRatio;
             var mesh = MeshGenerator.generateMesh(textBlob, scale).transform(xform);
 
             if (!this._applyClip(mesh.bounds)) {
             this._layers.Clear();
             this._layers.Add(firstLayer);
         }
-        
+
         void _drawLayer(RenderLayer layer, CommandBuffer cmdBuf) {
             foreach (var subLayer in layer.layers) {
                 cmdBuf.GetTemporaryRT(subLayer.rtID, new RenderTextureDescriptor(
                     useMipMap = false,
                     autoGenerateMips = false,
-                });
+                }, FilterMode.Bilinear);
                 this._drawLayer(subLayer, cmdBuf);
             }
 
 
                 if (!this.meshObj) {
                     this.meshObj = canvas._meshPool.getMesh();
-                    
+
-                    
+
                     this.meshObj.SetVertices(this.mesh.vertices);
                     this.meshObj.SetTriangles(this.mesh.triangles, 0, false);
                     this.meshObj.SetUVs(0, this.mesh.uv);
         public const int stencilIntersect0 = 8;
         public const int stencilIntersect1 = 9;
         public const int texfontPass0 = 10;
+        public const int mfPass0 = 11;
+        public static void transformCopy(float[] t, float[] s) {
+            t[0] = s[0];
+            t[1] = s[1];
+            t[2] = s[2];
+            t[3] = s[3];
+            t[4] = s[4];
+            t[5] = s[5];
+        }
+
         public static void transformIdentity(float[] t) {
             t[0] = 1.0f;
             t[1] = 0.0f;
             t[5] = 0.0f;
         }
 
-        
         // t = s * t;
         public static void transformMultiply(float[] t, float[] s) {
             float t0 = t[0] * s[0] + t[1] * s[2];
             t[4] = t4;
         }
 
+        // t = t * s;
         public static void transformPremultiply(float[] t, float[] s) {
             float[] s2 = {s[0], s[1], s[2], s[3], s[4], s[5]};
             transformMultiply(s2, t);
             return (getScaleX(t) + getScaleY(t)) * 0.5f;
         }
 
+        public static float getMaxScale(float[] t) {
+            return Mathf.Max(getScaleX(t), getScaleY(t));
+        }
+
         public static float getScaleX(float[] t) {
             return Mathf.Sqrt(t[0] * t[0] + t[2] * t[2]);
         }
         }
 
+        public static float mapRadius(float[] t, float radius) {
+            // mapped point of (radius, 0) and (0, radius)
+            var x0 = radius * t[0] + t[4];
+            var y0 = radius * t[1] + t[5];
+            var x1 = radius * t[2] + t[4];
+            var y1 = radius * t[3] + t[5];
+
+            // geometric mean of len0 and len1.
+            return Mathf.Sqrt(Mathf.Sqrt((x0 * x0 + y0 * y0) * (x1 * x1 + y1 * y1)));
+        }
+
+        public static void transformPoint(out float dx, out float dy, float[] t, float sx, float sy) {
+            dx = sx * t[0] + sy * t[2] + t[4];
+            dy = sx * t[1] + sy * t[3] + t[5];
+        }
+
         public static float[] fromMatrix3(Matrix3 matrix) {
             return new[] {
                 matrix.getScaleX(), matrix.getSkewY(),
                 xform[1], xform[3], xform[5],
                 0, 0, 1
             );
+        }
+    }
+
+    static class BlurUtils {
+        static readonly Dictionary<_GaussianKernelKey, float[]> _gaussianKernels
+            = new Dictionary<_GaussianKernelKey, float[]>();
+
+        public static float[] get1DGaussianKernel(float gaussianSigma, int radius) {
+            var width = 2 * radius + 1;
+            D.assert(width <= 25);
+            
+            var key = new _GaussianKernelKey(gaussianSigma, radius);
+            return _gaussianKernels.putIfAbsent(key, () => {
+                var kernel = new float[25];
+                float twoSigmaSqrd = 2.0f * gaussianSigma * gaussianSigma;
+
+                if (ScalarUtils.ScalarNearlyZero(twoSigmaSqrd)) {
+                    for (int i = 0; i < width; ++i) {
+                        kernel[i] = 0.0f;
+                    }
+                    return kernel;
+                }
+
+                float denom = 1.0f / twoSigmaSqrd;
+
+                float sum = 0.0f;
+                for (int i = 0; i < width; ++i) {
+                    float x = i - radius;
+                    // Note that the constant term (1/(sqrt(2*pi*sigma^2)) of the Gaussian
+                    // is dropped here, since we renormalize the kernel below.
+                    kernel[i] = Mathf.Exp(-x * x * denom);
+                    sum += kernel[i];
+                }
+                // Normalize the kernel
+                float scale = 1.0f / sum;
+                for (int i = 0; i < width; ++i) {
+                    kernel[i] *= scale;
+                }
+
+                return kernel;
+            });
+        }
+
+        public static float adjustSigma(float sigma, out int scaleFactor, out int radius) {
+            scaleFactor = 1;
+
+            const int maxTextureSize = 16384;
+            const float MAX_BLUR_SIGMA = 4.0f;
+            
+            while (sigma > MAX_BLUR_SIGMA) {
+                scaleFactor *= 2;
+                sigma *= 0.5f;
+
+                if (scaleFactor > maxTextureSize) {
+                    scaleFactor = maxTextureSize;
+                    sigma = MAX_BLUR_SIGMA;
+                }
+            }
+
+            radius = Mathf.CeilToInt(sigma * 3.0f);
+            D.assert(radius <= 3 * MAX_BLUR_SIGMA);
+            return sigma;
+        }
+
+        class _GaussianKernelKey : IEquatable<_GaussianKernelKey> {
+            public readonly float gaussianSigma;
+            public readonly int radius;
+
+            public _GaussianKernelKey(float gaussianSigma, int radius) {
+                this.gaussianSigma = gaussianSigma;
+                this.radius = radius;
+            }
+
+            public bool Equals(_GaussianKernelKey other) {
+                if (ReferenceEquals(null, other)) {
+                    return false;
+                }
+                if (ReferenceEquals(this, other)) {
+                    return true;
+                }
+                return this.gaussianSigma.Equals(other.gaussianSigma) &&
+                       this.radius == other.radius;
+            }
+
+            public override bool Equals(object obj) {
+                if (ReferenceEquals(null, obj)) {
+                    return false;
+                }
+                if (ReferenceEquals(this, obj)) {
+                    return true;
+                }
+                if (obj.GetType() != this.GetType()) {
+                    return false;
+                }
+                return this.Equals((_GaussianKernelKey) obj);
+            }
+
+            public override int GetHashCode() {
+                unchecked {
+                    var hashCode = this.gaussianSigma.GetHashCode();
+                    hashCode = (hashCode * 397) ^ this.radius;
+                    return hashCode;
+                }
+            }
+
+            public static bool operator ==(_GaussianKernelKey left, _GaussianKernelKey right) {
+                return Equals(left, right);
+            }
+
+            public static bool operator !=(_GaussianKernelKey left, _GaussianKernelKey right) {
+                return !Equals(left, right);
+            }
+
+            public override string ToString() {
+                return $"_GaussianKernelKey(gaussianSigma: {this.gaussianSigma:F1}, radius: {this.radius})";
+            }
         }
     }
 }

Runtime/ui/painting/painting.cs

 using System;
+using Unity.UIWidgets.foundation;
 using UnityEngine;
 
 namespace Unity.UIWidgets.ui {
         bevel,
     }
 
-    public class ColorFilter {
-        public Color color;
-        public BlendMode blendMode;
+    public enum BlurStyle {
+        normal, // only normal for now.
+        solid,
+        outer,
+        inner,
+    }
+
+    public class MaskFilter : IEquatable<MaskFilter> {
+        MaskFilter(BlurStyle style, double sigma) {
+            this.style = style;
+            this.sigma = sigma;
+        }
+
+        public static MaskFilter blur(BlurStyle style, double sigma) {
+            return new MaskFilter(style, sigma);
+        }
+
+        public readonly BlurStyle style;
+        public readonly double sigma;
+
+        public bool Equals(MaskFilter other) {
+            if (ReferenceEquals(null, other)) {
+                return false;
+            }
+            if (ReferenceEquals(this, other)) {
+                return true;
+            }
+            return this.style == other.style && this.sigma.Equals(other.sigma);
+        }
+
+        public override bool Equals(object obj) {
+            if (ReferenceEquals(null, obj)) {
+                return false;
+            }
+            if (ReferenceEquals(this, obj)) {
+                return true;
+            }
+            if (obj.GetType() != this.GetType()) {
+                return false;
+            }
+            return this.Equals((MaskFilter) obj);
+        }
+
+        public override int GetHashCode() {
+            unchecked {
+                return ((int) this.style * 397) ^ this.sigma.GetHashCode();
+            }
+        }
+
+        public static bool operator ==(MaskFilter left, MaskFilter right) {
+            return Equals(left, right);
+        }
+
+        public static bool operator !=(MaskFilter left, MaskFilter right) {
+            return !Equals(left, right);
+        }
+
+        public override string ToString() {
+            return $"MaskFilter.blur(${this.style}, ${this.sigma:F1})";
+        }
+    }
+
+    public class ColorFilter : IEquatable<ColorFilter> {
+        ColorFilter(Color color, BlendMode blendMode) {
+            D.assert(color != null);
+            this.color = color;
+            this.blendMode = blendMode;
+        }
+
+        public static ColorFilter mode(Color color, BlendMode blendMode) {
+            return new ColorFilter(color, blendMode);
+        }
+
+        public readonly Color color;
+
+        public readonly BlendMode blendMode;
+
+        public bool Equals(ColorFilter other) {
+            if (ReferenceEquals(null, other)) {
+                return false;
+            }
+            if (ReferenceEquals(this, other)) {
+                return true;
+            }
+            return Equals(this.color, other.color) && this.blendMode == other.blendMode;
+        }
+
+        public override bool Equals(object obj) {
+            if (ReferenceEquals(null, obj)) {
+                return false;
+            }
+            if (ReferenceEquals(this, obj)) {
+                return true;
+            }
+            if (obj.GetType() != this.GetType()) {
+                return false;
+            }
+            return this.Equals((ColorFilter) obj);
+        }
+
+        public override int GetHashCode() {
+            unchecked {
+                return ((this.color != null ? this.color.GetHashCode() : 0) * 397) ^ (int) this.blendMode;
+            }
+        }
+
+        public static bool operator ==(ColorFilter left, ColorFilter right) {
+            return Equals(left, right);
+        }
+
+        public static bool operator !=(ColorFilter left, ColorFilter right) {
+            return !Equals(left, right);
+        }
+
+        public override string ToString() {
+            return $"ColorFilter({this.color}, {this.blendMode})";
+        }
     }
 
     public enum TileMode {
 
         public ColorFilter colorFilter = null;
 
+        public MaskFilter maskFilter = null;
+
-        public double blurSigma;
+        public bool invertColors;
+
+        public Paint() {
+        }
+
+        public Paint(Paint paint) {
+            D.assert(paint != null);
-        public bool invertColors;
+            this.color = paint.color;
+            this.blendMode = paint.blendMode;
+            this.style = paint.style;
+            this.strokeWidth = paint.strokeWidth;
+            this.strokeCap = paint.strokeCap;
+            this.strokeJoin = paint.strokeJoin;
+            this.strokeMiterLimit = paint.strokeMiterLimit;
+            this.filterMode = paint.filterMode;
+            this.colorFilter = paint.colorFilter;
+            this.maskFilter = paint.maskFilter;
+            this.shader = paint.shader;
+            this.invertColors = paint.invertColors;
+        }
+
+        public static Paint shapeOnly(Paint paint) {
+            return new Paint {
+                style = paint.style,
+                strokeWidth = paint.strokeWidth,
+                strokeCap = paint.strokeCap,
+                strokeJoin = paint.strokeJoin,
+                strokeMiterLimit = paint.strokeMiterLimit,
+            };
+        }
     }
 
     public static class Conversions {

Runtime/ui/painting/path.cs

 
         public MeshMesh(List<Vector3> vertices, List<int> triangles, List<Vector2> uv = null) {
             D.assert(vertices != null);
-            D.assert(vertices.Count > 0);
+            D.assert(vertices.Count >= 0);
-            D.assert(triangles.Count > 0);
+            D.assert(triangles.Count >= 0);
             D.assert(uv == null || uv.Count == vertices.Count);
 
             this.vertices = vertices;
-            double minX = vertices[0].x;
-            double maxX = vertices[0].x;
-            double minY = vertices[0].y;
-            double maxY = vertices[0].y;
+            if (vertices.Count > 0) {
+                double minX = vertices[0].x;
+                double maxX = vertices[0].x;
+                double minY = vertices[0].y;
+                double maxY = vertices[0].y;
-            for (int i = 1; i < vertices.Count; i++) {
-                var vertex = vertices[i];
-                if (vertex.x < minX) {
-                    minX = vertex.x;
-                }
-                if (vertex.x > maxX) {
-                    maxX = vertex.x;
-                }
-                if (vertex.y < minY) {
-                    minY = vertex.y;
+                for (int i = 1; i < vertices.Count; i++) {
+                    var vertex = vertices[i];
+                    if (vertex.x < minX) {
+                        minX = vertex.x;
+                    }
+                    if (vertex.x > maxX) {
+                        maxX = vertex.x;
+                    }
+                    if (vertex.y < minY) {
+                        minY = vertex.y;
+                    }
+                    if (vertex.y > maxY) {
+                        maxY = vertex.y;
+                    }
-                if (vertex.y > maxY) {
-                    maxY = vertex.y;
-                }
+
+                this.bounds = Rect.fromLTRB(minX, minY, maxX, maxY);
+            } else {
+                this.bounds = Rect.zero;
-
-            this.bounds = Rect.fromLTRB(minX, minY, maxX, maxY);
         }
 
         public MeshMesh transform(float[] xform) {

Runtime/ui/text.cs

             return this.width.GetHashCode();
         }
 
+        public static bool operator ==(ParagraphConstraints left, ParagraphConstraints right) {
+            return Equals(left, right);
+        }
+
+        public static bool operator !=(ParagraphConstraints left, ParagraphConstraints right) {
+            return !Equals(left, right);
+        }
+
         public override string ToString() {
             return $"Width: {this.width}";
         }
         public readonly double letterSpacing = 0.0;
         public readonly double wordSpacing = 0.0;
         public readonly TextBaseline textBaseline = TextBaseline.alphabetic;
-        public double height = 1.0;
+        public readonly double height = 1.0;
         public readonly TextDecoration decoration = TextDecoration.none;
         public readonly Color decorationColor;
         public readonly TextDecorationStyle decorationStyle = TextDecorationStyle.solid;

Tests/Editor/CanvasAndLayers.cs

 
             var widthPaint = new Paint {
                 color = new Color(0xFFFF0000),
+                style = PaintingStyle.stroke,
                 strokeWidth = 4,
             };
 
         }
 
         void drawRectShadow() {
-//            var canvas = new CanvasImpl();
-//
-//            var paint = new Paint {
-//                color = new Color(0xFF00FF00),
-//                blurSigma = 3.0,
-//            };
-//
-//            canvas.drawRectShadow(
-//                Rect.fromLTWH(10, 10, 100, 100),
-//                paint);
-//
-//            paint = new Paint {
-//                color = new Color(0xFFFFFF00),
-//                blurSigma = 2.0,
-//            };
-//
-//            canvas.drawRectShadow(
-//                Rect.fromLTWH(10, 150, 100, 100),
-//                paint);
+            var canvas = new CommandBufferCanvas(this._renderTexture, (float) Window.instance.devicePixelRatio, this._meshPool);
+
+            var paint = new Paint {
+                color = new Color(0xFF00FF00),
+                maskFilter = MaskFilter.blur(BlurStyle.normal, 3),
+            };
+            
+            canvas.clipRect(Unity.UIWidgets.ui.Rect.fromLTWH(25, 25, 300, 300));
+                
+            canvas.rotate(-Math.PI/8.0);
+            
+
+            canvas.drawRect(
+                Unity.UIWidgets.ui.Rect.fromLTWH(10, 10, 100, 100),
+                paint);
+
+            paint = new Paint {
+                color = new Color(0xFFFFFF00),
+                maskFilter = MaskFilter.blur(BlurStyle.normal, 15),
+            };
+
+            canvas.drawRect(
+                Unity.UIWidgets.ui.Rect.fromLTWH(10, 150, 200, 200),
+                paint);
+            
+            canvas.flush();
         }
 
         void drawPicture() {
 
             paint = new Paint {
                 color = new Color(0xFF00FFFF),
-                blurSigma = 3,
+                maskFilter = MaskFilter.blur(BlurStyle.normal, 3),
             };
             canvas.drawRect(
                 Unity.UIWidgets.ui.Rect.fromLTWH(150, 150, 110, 120),