Split Size into Size and Offset.

sky/sdk/lib/example/raw/painting.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:sky' as sky;
 import 'dart:math' as math;
 import 'dart:typed_data';
 
 void beginFrame(double timeStamp) {
+  sky.Size size = new sky.Size(sky.view.width, sky.view.height);
   sky.PictureRecorder recorder = new sky.PictureRecorder();
-  Canvas canvas = new Canvas(recorder, sky.view.width, 200.0);
+  sky.Canvas canvas = new sky.Canvas(recorder, size);
 
   sky.Paint paint = new sky.Paint();
-  sky.Point mid = new sky.Point(sky.view.width / 2.0, sky.view.height / 2.0);
-  double radius = math.min(mid.x, mid.y);
+  sky.Point mid = size.center(sky.Point.origin);
+  double radius = size.shortestSide / 2.0;
 
   canvas.drawPaint(new sky.Paint()..color = const sky.Color(0xFFFFFFFF));
 
   canvas.save();
 
   canvas.translate(-mid.x/2.0, sky.view.height*2.0);
   canvas.clipRect(
       new sky.Rect.fromLTRB(0.0, -sky.view.height, sky.view.width, radius));
 
   canvas.translate(mid.x, mid.y);
   paint.color = const sky.Color.fromARGB(128, 255, 0, 255);
   canvas.rotate(math.PI/4.0);
 
   sky.Gradient yellowBlue = new sky.Gradient.linear(
       [new sky.Point(-radius, -radius), new sky.Point(0.0, 0.0)],
       [const sky.Color(0xFFFFFF00), const sky.Color(0xFF0000FF)]);
   canvas.drawRect(new sky.Rect.fromLTRB(-radius, -radius, radius, radius),
                    new sky.Paint()..setShader(yellowBlue));
 
   // Scale x and y by 0.5.
   var scaleMatrix = new Float32List.fromList([
       0.5, 0.0, 0.0, 0.0,
       0.0, 0.5, 0.0, 0.0,
       0.0, 0.0, 0.0, 0.0,
       0.0, 0.0, 0.0, 1.0,
   ]);
   canvas.concat(scaleMatrix);
   paint.color = const sky.Color.fromARGB(128, 0, 255, 0);
-  canvas.drawCircle(0.0, 0.0, radius, paint);
+  canvas.drawCircle(sky.Point.origin, radius, paint);
 
   canvas.restore();
 
   canvas.translate(0.0, 50.0);
   var builder = new sky.LayerDrawLooperBuilder()
       ..addLayerOnTop(
           new sky.DrawLooperLayerInfo()
-            ..setOffset(const sky.Point(150.0, 0.0))
+            ..setOffset(const sky.Offset(150.0, 0.0))
             ..setColorMode(sky.TransferMode.src)
             ..setPaintBits(sky.PaintBits.all),
           (sky.Paint layerPaint) {
         layerPaint.color = const sky.Color.fromARGB(128, 255, 255, 0);
         layerPaint.setColorFilter(new sky.ColorFilter.mode(
             const sky.Color.fromARGB(128, 0, 0, 255), sky.TransferMode.srcIn));
         layerPaint.setMaskFilter(new sky.MaskFilter.blur(
             sky.BlurStyle.normal, 3.0, highQuality: true));
       })
       ..addLayerOnTop(
           new sky.DrawLooperLayerInfo()
-            ..setOffset(const sky.Point(75.0, 75.0))
+            ..setOffset(const sky.Offset(75.0, 75.0))
             ..setColorMode(sky.TransferMode.src)
             ..setPaintBits(sky.PaintBits.shader),
           (sky.Paint layerPaint) {
         sky.Gradient redYellow = new sky.Gradient.radial(
             new sky.Point(0.0, 0.0), radius/3.0,
             [const sky.Color(0xFFFFFF00), const sky.Color(0xFFFF0000)],
             null, sky.TileMode.mirror);
         layerPaint.setShader(redYellow);
         // Since we're don't set sky.PaintBits.maskFilter, this has no effect.
         layerPaint.setMaskFilter(new sky.MaskFilter.blur(
             sky.BlurStyle.normal, 50.0, highQuality: true));
       })
       ..addLayerOnTop(
-          new sky.DrawLooperLayerInfo()..setOffset(const sky.Point(225.0, 75.0)),
+          new sky.DrawLooperLayerInfo()..setOffset(const sky.Offset(225.0, 75.0)),
           (sky.Paint layerPaint) {
         // Since this layer uses a DST color mode, this has no effect.
         layerPaint.color = const sky.Color.fromARGB(128, 255, 0, 0);
       });
   paint.setDrawLooper(builder.build());
-  canvas.drawCircle(0.0, 0.0, radius, paint);
+  canvas.drawCircle(sky.Point.origin, radius, paint);
 
   sky.view.picture = recorder.endRecording();
 }
 
 void main() {
   sky.view.setBeginFrameCallback(beginFrame);
   sky.view.scheduleFrame();
 }