Attempt to write a RenderShadowedBox

sky/sdk/lib/framework/rendering/box.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import 'dart:math' as math;
 import 'dart:sky' as sky;
 import 'dart:typed_data';
 import 'node.dart';
 import 'package:vector_math/vector_math.dart';
 
@@ skipping 342 matching lines @@
     canvas.concat([
       storage[ 0], storage[ 1], storage[ 3],
       storage[ 4], storage[ 5], storage[ 7],
       storage[12], storage[13], storage[15],
     ]);
     super.paint(canvas);
     canvas.restore();
   }
 }
 
+// This must be immutable, because we won't notice when it changes
+class BoxShadow {
+  const BoxShadow({
+    this.color,
+    this.offset
+  });
+
+  final sky.Size offset;
+  final sky.Color color;
+}
+
+class RenderShadowedBox extends RenderProxyBox {
+
+  RenderShadowedBox({
+    BoxShadow shadow,
+    RenderBox child
+  }) : _shadow = shadow, super(child);
+
+  BoxShadow _shadow;
+  BoxShadow get shadow => _shadow;
+  void set shadow (BoxShadow value) {
+    if (value == _shadow)
+      return;
+    _shadow = value;
+    markNeedsPaint();
+  }
+
+  sky.Paint _createShadowPaint(BoxShadow shadow) {
+    // Make the main layer transparent for now.
+    sky.Paint paint = new sky.Paint()..color = const sky.Color.fromARGB(255, 0, 255, 0);
+    var builder = new sky.LayerDrawLooperBuilder()
+      // Shadow layer.
+      ..addLayerOnTop(
+          new sky.DrawLooperLayerInfo()
+            ..setPaintBits(-1)
+            ..setOffset(shadow.offset.toPoint())
+            ..setColorMode(sky.TransferMode.srcInMode),

[Matt Perry, 2015/06/03 19:13:59]

Did you mean to revert to srcInMode here?

+          (sky.Paint layerPaint) {
+        layerPaint.color = shadow.color;
+        // TODO(mpcomplete): blur should respect the offset?

[Matt Perry, 2015/06/03 19:13:58]

Are you saying it doesn't, or that it does but you're not sure if it should?
(FWIW I don't even know what it means for blur to respect the offset :)

+        layerPaint.setMaskFilter(
+          new sky.MaskFilter.Blur(sky.BlurStyle.normal, 5.0, highQuality: true));
+      })
+      // Main layer.
+      ..addLayerOnTop(new sky.DrawLooperLayerInfo(), (_) {});
+    paint.setDrawLooper(builder.build());
+    return paint;
+  }
+
+  void paint(RenderNodeDisplayList canvas) {
+    sky.Paint paint = _createShadowPaint(_shadow);
+    canvas.drawRect(new sky.Rect.fromLTRB(0.0, 0.0, size.width, size.height), paint);
+    super.paint(canvas);
+  }
+}
 
 // RENDER VIEW LAYOUT MANAGER
 
 class ViewConstraints {
 
   const ViewConstraints({
     this.width: 0.0, this.height: 0.0, this.orientation: null
   });
 
   final double width;
@@ skipping 88 matching lines @@
 
   void defaultPaint(RenderNodeDisplayList canvas) {
     RenderBox child = firstChild;
     while (child != null) {
       assert(child.parentData is ParentDataType);
       canvas.paintChild(child, child.parentData.position);
       child = child.parentData.nextSibling;
     }
   }
 }