add color_filter.cs and constants.cs

com.unity.uiwidgets/Runtime/rendering/layer.cs

                 }
             }
         }
-        
-        EngineLayer _engineLayer;
+
+        protected EngineLayer _engineLayer;
 
         internal virtual void updateSubtreeNeedsAddToScene() {
             _needsAddToScene = _needsAddToScene || alwaysNeedsAddToScene;
         }
     }
 
+    /// A composite layer that applies a [ColorFilter] to its children.
+    public class ColorFilterLayer : ContainerLayer {
+        /// Creates a layer that applies a [ColorFilter] to its children.
+        ///
+        /// The [colorFilter] property must be non-null before the compositing phase
+        /// of the pipeline.
+        public ColorFilterLayer(ColorFilter colorFilter = null) {
+            _colorFilter = colorFilter;
+        }
+
+        /// The color filter to apply to children.
+        ///
+        /// The scene must be explicitly recomposited after this property is changed
+        /// (as described at [Layer]).
+        public ColorFilter colorFilter {
+            get {
+                return _colorFilter;
+            }
+            set {
+                D.assert(value != null);
+                if (value != _colorFilter) {
+                    _colorFilter = value;
+                    markNeedsAddToScene();
+                }
+            }
+        }
+
+        ColorFilter _colorFilter;
+        
+        
+        //[!!!]builder.pushColorFilter?
+        /*public override void addToScene(ui.SceneBuilder builder, Offset layerOffset = null ) {
+            D.assert(colorFilter != null);
+            engineLayer =  builder.pushColorFilter(
+                colorFilter,
+                oldLayer: _engineLayer as ui.ColorFilterEngineLayer
+            );
+            addChildrenToScene(builder, layerOffset);
+            builder.pop();
+        }*/
+        
+        public override void debugFillProperties(DiagnosticPropertiesBuilder properties) {
+            base.debugFillProperties(properties);
+            properties.add(new DiagnosticsProperty<ColorFilter>("colorFilter", colorFilter));
+        }
+    }
+    
+    
     public class TransformLayer : OffsetLayer {
         public TransformLayer(Matrix4 transform = null, Offset offset = null) : base(offset) {
             _transform = transform ?? Matrix4.identity();

com.unity.uiwidgets/Runtime/rendering/object.cs

             return
                 $"{GetType()}#{GetHashCode()}(layer: {_containerLayer}, canvas bounds: {estimatedBounds}";
         }
+        
+        public ColorFilterLayer pushColorFilter(Offset offset, ColorFilter colorFilter, PaintingContextCallback painter, ColorFilterLayer oldLayer = null) {
+            D.assert(colorFilter != null);
+            ColorFilterLayer layer = oldLayer ?? new ColorFilterLayer();
+            layer.colorFilter = colorFilter;
+            pushLayer(layer, painter, offset);
+            return layer;
+        }
     }
 
     public abstract class Constraints {
             get {
                 D.assert(!isRepaintBoundary || (_layer == null || _layer is OffsetLayer));
                 return _layer;
+            }
+            set {
+                D.assert(!isRepaintBoundary);
+                _layer = value;
             }
         }
 

com.unity.uiwidgets/Runtime/widgets/color_filter.cs

+using Unity.UIWidgets.foundation;
+using Unity.UIWidgets.rendering;
+using Unity.UIWidgets.ui;
+
+namespace Unity.UIWidgets.widgets {
+    
+        public class ColorFiltered : SingleChildRenderObjectWidget {
+            /// Creates a widget that applies a [ColorFilter] to its child.
+            ///
+            /// The [colorFilter] must not be null.
+            protected ColorFiltered(ColorFilter colorFilter = null, Widget child = null, Key key = null)
+                : base(key: key, child: child) {
+                D.assert(colorFilter != null);
+            }
+
+            /// The color filter to apply to the child of this widget.
+            public readonly ColorFilter colorFilter;
+            
+            public override RenderObject createRenderObject(BuildContext context) => new _ColorFilterRenderObject(colorFilter);
+            
+            public override void updateRenderObject(BuildContext context, RenderObject renderObject) {
+                ((_ColorFilterRenderObject)renderObject).colorFilter = colorFilter;
+            }
+            
+            public override void debugFillProperties(DiagnosticPropertiesBuilder properties) {
+                base.debugFillProperties(properties);
+                properties.add(new DiagnosticsProperty<ColorFilter>("colorFilter", colorFilter));
+            }
+        }
+
+    public class _ColorFilterRenderObject : RenderProxyBox {
+        public _ColorFilterRenderObject(ColorFilter _colorFilter) {
+            this._colorFilter = _colorFilter;
+        }
+
+    public ColorFilter colorFilter {
+        get { return _colorFilter; }
+        set {
+            D.assert(value != null);
+            if (value != _colorFilter) {
+                _colorFilter = value;
+                markNeedsPaint();
+            }
+        }
+    }
+
+    ColorFilter _colorFilter;
+    
+    public  bool alwaysNeedsCompositing {
+        get { return child != null; }
+    }
+    
+    public override void paint(PaintingContext context, Offset offset) {
+        layer = context.pushColorFilter(offset, colorFilter, base.paint, oldLayer: layer as ColorFilterLayer);
+    }
+    }
+
+    
+}

com.unity.uiwidgets/Runtime/widgets/constants.cs

+namespace Unity.UIWidgets.widgets {
+    public class constants {
+        const float kMinInteractiveDimension = 48.0f;
+    }
+}