Integrate the linear constraint solver into Sky as a RenderBox subclass.

sky/sdk/example/rendering/simple_autolayout.dart

Index: sky/sdk/example/rendering/simple_autolayout.dart
diff --git a/sky/sdk/example/rendering/simple_autolayout.dart b/sky/sdk/example/rendering/simple_autolayout.dart
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+++ b/sky/sdk/example/rendering/simple_autolayout.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';
+import 'package:sky/rendering/box.dart';
+import 'package:sky/rendering/object.dart';
+import 'package:sky/rendering/sky_binding.dart';
+import 'package:sky/rendering/auto_layout.dart';
+import 'package:cassowary/cassowary.dart' as al;
+
+void main() {
+  var c1 = new RenderDecoratedBox(

[Hixie, 2015/07/09 00:53:14]

don't use 'var'

[Chinmay, 2015/07/09 21:44:19]

ack

+    decoration: new BoxDecoration(backgroundColor: const Color(0xFFFF0000))
+  );
+
+  var c2 = new RenderDecoratedBox(
+    decoration: new BoxDecoration(backgroundColor: const Color(0xFF00FF00))
+  );
+
+  var c3 = new RenderDecoratedBox(
+    decoration: new BoxDecoration(backgroundColor: const Color(0xFF0000FF))
+  );
+
+  var c4 = new RenderDecoratedBox(
+    decoration: new BoxDecoration(backgroundColor: const Color(0xFFFFFFFF))
+  );
+
+  var root = new RenderAutoLayout(children: [c1, c2, c3, c4]);
+
+  AutoLayoutParentData p1 = c1.parentData;
+  AutoLayoutParentData p2 = c2.parentData;
+  AutoLayoutParentData p3 = c3.parentData;
+  AutoLayoutParentData p4 = c4.parentData;
+
+  root.addConstraints(<al.Constraint>[
+    // Sum of widths of each box must be equal to that of the container
+    (p1.width + p2.width + p3.width == root.width) as al.Constraint,
+
+    // The boxes must be stacked left to right
+    p1.rightEdge <= p2.leftEdge,
+    p2.rightEdge <= p3.leftEdge,
+
+    // The widths of the first and the third boxes should be equal
+    (p1.width == p3.width) as al.Constraint,
+
+    // The width of the second box should be twice as much as that of the first
+    // and third
+    (p2.width * al.CM(2.0) == p1.width) as al.Constraint,
+
+    // The height of the three boxes should be equal to that of the container
+    (p1.height == p2.height) as al.Constraint,
+    (p2.height == p3.height) as al.Constraint,
+    (p3.height == root.height) as al.Constraint,
+
+    // The fourth box should be half as wide as the second and must be attached
+    // to the right edge of the same (by its center)
+    (p4.width == p2.width / al.CM(2.0)) as al.Constraint,
+    (p4.height == al.CM(50.0)) as al.Constraint,
+    (p4.horizontalCenter == p2.rightEdge) as al.Constraint,
+    (p4.verticalCenter == p2.height / al.CM(2.0)) as al.Constraint,
+  ]);
+
+  new SkyBinding(root: root);
+}