Add an example of an app that manipulates both a RenderObject tree and has some fn logic in it.

sky/examples/widgets/spinning_mixed.dart

Index: sky/examples/widgets/spinning_mixed.dart
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+// 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:sky' as sky;
+
+import 'package:sky/framework/rendering/box.dart';
+import 'package:sky/framework/rendering/flex.dart';
+import 'package:sky/framework/scheduler.dart';
+import 'package:sky/framework/widgets/ui_node.dart';
+import 'package:sky/framework/widgets/wrappers.dart';
+import 'package:vector_math/vector_math.dart';
+
+import '../lib/solid_color_box.dart';
+
+// Solid colour, RenderObject version
+void addFlexChildSolidColor(RenderFlex parent, sky.Color backgroundColor, { int flex: 0 }) {
+  RenderSolidColorBox child = new RenderSolidColorBox(backgroundColor);
+  parent.add(child);
+  child.parentData.flex = flex;
+}
+
+// Solid colour, Widget version
+class Rectangle extends Component {
+  Rectangle(this.color, { Object key }) : super(key: key);
+  final Color color;
+  UINode build() {
+    return new FlexExpandingChild(
+      new Container(
+        decoration: new BoxDecoration(backgroundColor: color)
+      )
+    );
+  }
+}
+
+UINode builder() {
+  return new Flex([
+      new Rectangle(const Color(0xFF00FFFF), key: 'a'),
+      new Container(
+        padding: new EdgeDims.all(10.0),
+        margin: new EdgeDims.all(10.0),
+        decoration: new BoxDecoration(backgroundColor: const Color(0xFFCCCCCC)),
+        child: new Image(src: "https://www.dartlang.org/logos/dart-logo.png",
+          size: new Size(300.0, 300.0),
+          key: 1
+        )
+      ),
+      new Rectangle(const Color(0xFFFFFF00), key: 'b'),
+    ],
+    direction: FlexDirection.vertical,
+    justifyContent: FlexJustifyContent.spaceBetween
+  );
+}
+
+double timeBase;
+RenderTransform transformBox;
+
+void rotate(double timeStamp) {
+  if (timeBase == null)
+    timeBase = timeStamp;
+  double delta = (timeStamp - timeBase) / 1000; // radians
+
+  transformBox.setIdentity();
+  transformBox.translate(transformBox.size.width / 2.0, transformBox.size.height / 2.0);
+  transformBox.rotateZ(delta);
+  transformBox.translate(-transformBox.size.width / 2.0, -transformBox.size.height / 2.0);
+}
+
+void main() {
+  RenderFlex flexRoot = new RenderFlex(direction: FlexDirection.vertical);
+
+  RenderProxyBox proxy = new RenderProxyBox();
+  new RenderObjectToUINodeAdapter(proxy, builder); // adds itself to proxy
+
+  addFlexChildSolidColor(flexRoot, const sky.Color(0xFFFF00FF), flex: 1);
+  flexRoot.add(proxy);
+  addFlexChildSolidColor(flexRoot, const sky.Color(0xFF0000FF), flex: 1);
+
+  transformBox = new RenderTransform(child: flexRoot, transform: new Matrix4.identity());
+  RenderPadding root = new RenderPadding(padding: new EdgeDims.all(20.0), child: transformBox);
+
+  // Because we're going to use UINodes, we want to initialise its
+  // AppView, not use the default one. We don't really need to do
+  // this, because RenderObjectToUINodeAdapter does it for us, but
+  // it's good practice in case we happen to not have a
+  // RenderObjectToUINodeAdapter in our tree at startup.
+  UINodeAppView.initUINodeAppView();
+  UINodeAppView.appView.root = root;
+
+  addPersistentFrameCallback(rotate);
+}