Fix globalToLocal and update spinning_mixed (#6035)

* globalToLocal was just broken when there was a rotation and a
  translation at the same time. This fixes that and adds a test.

* update graphic used by spinning_mixed since the old one went 404.

* simplify some of the code in the demo.

* fix MatrixUtils.transformPoint to be consistent with how we transform
  points elsewhere.

* stop transforming points elsewhere, just use
  MatrixUtils.transformPoint.

* make the Widget binding handle not having a root element.

* make the spinning_mixed demo update its widget tree.

examples/layers/widgets/spinning_mixed.dart

@@ -51,7 +51,7 @@ void attachWidgetTreeToRenderTree(RenderProxyBox container) {
                   new RaisedButton(
                     child: new Row(
                       children: <Widget>[
-                        new Image.network('http://flutter.io/favicon.ico'),
+                        new Image.network('https://flutter.io/images/favicon.png'),
                         new Text('PRESS ME'),
                       ]
                     ),
@@ -83,9 +83,9 @@ void rotate(Duration timeStamp) {
   double delta = (timeStamp - timeBase).inMicroseconds.toDouble() / Duration.MICROSECONDS_PER_SECOND; // 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);
+
+  owner.buildScope(element);
 }
 
 void main() {
@@ -98,7 +98,7 @@ void main() {
   flexRoot.add(proxy);
   addFlexChildSolidColor(flexRoot, const Color(0xFF0000FF), flex: 1);
 
-  transformBox = new RenderTransform(child: flexRoot, transform: new Matrix4.identity());
+  transformBox = new RenderTransform(child: flexRoot, transform: new Matrix4.identity(), alignment: FractionalOffset.center);
   RenderPadding root = new RenderPadding(padding: new EdgeInsets.all(80.0), child: transformBox);
 
   binding.renderView.child = root;

packages/flutter/lib/src/animation/animation_controller.dart

@@ -5,6 +5,7 @@
 import 'dart:async';
 import 'dart:ui' as ui show lerpDouble;
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/physics.dart';
 import 'package:flutter/scheduler.dart';
 import 'package:meta/meta.dart';
@@ -184,6 +185,16 @@ class AnimationController extends Animation<double>
   ///
   /// Returns a [Future] that completes when the animation is complete.
   Future<Null> forward({ double from }) {
+    assert(() {
+      if (duration == null) {
+        throw new FlutterError(
+          'AnimationController.forward() called with no default Duration.\n'
+          'The "duration" property should be set, either in the constructor or later, before '
+          'calling the forward() function.'
+        );
+      }
+      return true;
+    });
     _direction = _AnimationDirection.forward;
     if (from != null)
       value = from;
@@ -194,6 +205,16 @@ class AnimationController extends Animation<double>
   ///
   /// Returns a [Future] that completes when the animation is complete.
   Future<Null> reverse({ double from }) {
+    assert(() {
+      if (duration == null) {
+        throw new FlutterError(
+          'AnimationController.reverse() called with no default Duration.\n'
+          'The "duration" property should be set, either in the constructor or later, before '
+          'calling the reverse() function.'
+        );
+      }
+      return true;
+    });
     _direction = _AnimationDirection.reverse;
     if (from != null)
       value = from;
@@ -206,7 +227,17 @@ class AnimationController extends Animation<double>
   Future<Null> animateTo(double target, { Duration duration, Curve curve: Curves.linear }) {
     Duration simulationDuration = duration;
     if (simulationDuration == null) {
-      assert(this.duration != null);
+      assert(() {
+        if (this.duration == null) {
+          throw new FlutterError(
+            'AnimationController.animateTo() called with no explicit Duration and no default Duration.\n'
+            'Either the "duration" argument to the animateTo() method should be provided, or the '
+            '"duration" property should be set, either in the constructor or later, before '
+            'calling the animateTo() function.'
+          );
+        }
+        return true;
+      });
       double range = upperBound - lowerBound;
       double remainingFraction = range.isFinite ? (target - _value).abs() / range : 1.0;
       simulationDuration = this.duration * remainingFraction;
@@ -233,6 +264,17 @@ class AnimationController extends Animation<double>
     min ??= lowerBound;
     max ??= upperBound;
     period ??= duration;
+    assert(() {
+      if (duration == null) {
+        throw new FlutterError(
+          'AnimationController.repeat() called with no explicit Duration and default Duration.\n'
+          'Either the "duration" argument to the repeat() method should be provided, or the '
+          '"duration" property should be set, either in the constructor or later, before '
+          'calling the repeat() function.'
+        );
+      }
+      return true;
+    });
     return animateWith(new _RepeatingSimulation(min, max, period));
   }
 

packages/flutter/lib/src/painting/transforms.dart

@@ -16,24 +16,24 @@ class MatrixUtils {
   /// Returns the given [transform] matrix as Offset, if the matrix is nothing
   /// but a 2D translation.
   ///
-  /// Returns null, otherwise.
+  /// Otherwise, returns null.
   static Offset getAsTranslation(Matrix4 transform) {
     assert(transform != null);
     Float64List values = transform.storage;
     // Values are stored in column-major order.
-    if (values[0] == 1.0 &&
+    if (values[0] == 1.0 && // col 1
         values[1] == 0.0 &&
         values[2] == 0.0 &&
         values[3] == 0.0 &&
-        values[4] == 0.0 &&
+        values[4] == 0.0 && // col 2
         values[5] == 1.0 &&
         values[6] == 0.0 &&
         values[7] == 0.0 &&
-        values[8] == 0.0 &&
+        values[8] == 0.0 && // col 3
         values[9] == 0.0 &&
         values[10] == 1.0 &&
         values[11] == 0.0 &&
-        values[14] == 0.0 &&
+        values[14] == 0.0 && // bottom of col 4 (values 12 and 13 are the x and y offsets)
         values[15] == 1.0) {
       return new Offset(values[12], values[13]);
     }

packages/flutter/lib/src/rendering/box.dart

@@ -1339,7 +1339,8 @@ abstract class RenderBox extends RenderObject {
   /// function to factor those transforms into the calculation.
   ///
   /// The RenderBox implementation takes care of adjusting the matrix for the
-  /// position of the given child.
+  /// position of the given child as determined during layout and stored on the
+  /// child's [parentData] in the [BoxParentData.offset] field.
   @override
   void applyPaintTransform(RenderObject child, Matrix4 transform) {
     assert(child.parent == this);
@@ -1348,20 +1349,24 @@ abstract class RenderBox extends RenderObject {
     transform.translate(offset.dx, offset.dy);
   }
 
+  Matrix4 _collectPaintTransform() {
+    assert(attached);
+    final List<RenderObject> renderers = <RenderObject>[];
+    for (RenderObject renderer = this; renderer != null; renderer = renderer.parent)
+      renderers.add(renderer);
+    final Matrix4 transform = new Matrix4.identity();
+    for (int index = renderers.length - 1; index > 0; index -= 1)
+      renderers[index].applyPaintTransform(renderers[index - 1], transform);
+    return transform;
+  }
+
   /// Convert the given point from the global coodinate system to the local
   /// coordinate system for this box.
   ///
   /// If the transform from global coordinates to local coordinates is
   /// degenerate, this function returns Point.origin.
   Point globalToLocal(Point point) {
-    assert(attached);
-    Matrix4 transform = new Matrix4.identity();
-    RenderObject renderer = this;
-    while (renderer.parent is RenderObject) {
-      RenderObject rendererParent = renderer.parent;
-      rendererParent.applyPaintTransform(renderer, transform);
-      renderer = rendererParent;
-    }
+    final Matrix4 transform = _collectPaintTransform();
     double det = transform.invert();
     if (det == 0.0)
       return Point.origin;
@@ -1371,13 +1376,7 @@ abstract class RenderBox extends RenderObject {
   /// Convert the given point from the local coordinate system for this box to
   /// the global coordinate system.
   Point localToGlobal(Point point) {
-    List<RenderObject> renderers = <RenderObject>[];
-    for (RenderObject renderer = this; renderer != null; renderer = renderer.parent)
-      renderers.add(renderer);
-    Matrix4 transform = new Matrix4.identity();
-    for (int index = renderers.length - 1; index > 0; index -= 1)
-      renderers[index].applyPaintTransform(renderers[index - 1], transform);
-    return MatrixUtils.transformPoint(transform, point);
+    return MatrixUtils.transformPoint(_collectPaintTransform(), point);
   }
 
   /// Returns a rectangle that contains all the pixels painted by this box.

packages/flutter/lib/src/rendering/flow.dart

@@ -378,16 +378,14 @@ class RenderFlow extends RenderBox
       final Matrix4 transform = childParentData._transform;
       if (transform == null)
         continue;
-      Matrix4 inverse = new Matrix4.zero();
-      double determinate = inverse.copyInverse(transform);
+      final Matrix4 inverse = new Matrix4.zero();
+      final double determinate = inverse.copyInverse(transform);
       if (determinate == 0.0) {
         // We cannot invert the transform. That means the child doesn't appear
         // on screen and cannot be hit.
         continue;
       }
-      final Vector3 position3 = new Vector3(position.x, position.y, 0.0);
-      final Vector3 transformed3 = inverse.transform3(position3);
-      Point childPosition = new Point(transformed3.x, transformed3.y);
+      final Point childPosition = MatrixUtils.transformPoint(inverse, position);
       if (child.hitTest(result, position: childPosition))
         return true;
     }

packages/flutter/lib/src/rendering/proxy_box.dart

@@ -6,6 +6,7 @@ import 'dart:ui' as ui show ImageFilter;
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
+import 'package:flutter/painting.dart';
 import 'package:meta/meta.dart';
 import 'package:vector_math/vector_math_64.dart';
 
@@ -1367,9 +1368,7 @@ class RenderTransform extends RenderProxyBox {
         // doesn't appear on screen and cannot be hit.
         return false;
       }
-      Vector3 position3 = new Vector3(position.x, position.y, 0.0);
-      Vector3 transformed3 = inverse.transform3(position3);
-      position = new Point(transformed3.x, transformed3.y);
+      position = MatrixUtils.transformPoint(inverse, position);
     }
     return super.hitTest(result, position: position);
   }
@@ -1515,9 +1514,7 @@ class RenderFittedBox extends RenderProxyBox {
       // doesn't appear on screen and cannot be hit.
       return false;
     }
-    Vector3 position3 = new Vector3(position.x, position.y, 0.0);
-    Vector3 transformed3 = inverse.transform3(position3);
-    position = new Point(transformed3.x, transformed3.y);
+    position = MatrixUtils.transformPoint(inverse, position);
     return super.hitTest(result, position: position);
   }
 

packages/flutter/lib/src/rendering/rotated_box.dart

@@ -5,6 +5,7 @@
 import 'dart:math' as math;
 
 import 'package:flutter/gestures.dart';
+import 'package:flutter/painting.dart';
 import 'package:vector_math/vector_math_64.dart';
 
 import 'box.dart';
@@ -93,9 +94,7 @@ class RenderRotatedBox extends RenderBox with RenderObjectWithChildMixin<RenderB
     if (child == null || _paintTransform == null)
       return false;
     Matrix4 inverse = new Matrix4.inverted(_paintTransform);
-    Vector3 position3 = new Vector3(position.x, position.y, 0.0);
-    Vector3 transformed3 = inverse.transform3(position3);
-    return child.hitTest(result, position: new Point(transformed3.x, transformed3.y));
+    return child.hitTest(result, position: MatrixUtils.transformPoint(inverse, position));
   }
 
   void _paintChild(PaintingContext context, Offset offset) {

packages/flutter/lib/src/widgets/binding.dart

@@ -293,7 +293,8 @@ abstract class WidgetsBinding extends BindingBase implements GestureBinding, Ren
       return true;
     });
     try {
-      buildOwner.buildScope(renderViewElement);
+      if (renderViewElement != null)
+        buildOwner.buildScope(renderViewElement);
       super.beginFrame();
       buildOwner.finalizeTree();
     } finally {
@@ -340,7 +341,8 @@ abstract class WidgetsBinding extends BindingBase implements GestureBinding, Ren
   void reassembleApplication() {
     _needToReportFirstFrame = true;
     preventThisFrameFromBeingReportedAsFirstFrame();
-    buildOwner.reassemble(renderViewElement);
+    if (renderViewElement != null)
+      buildOwner.reassemble(renderViewElement);
     super.reassembleApplication();
   }
 }

packages/flutter/test/painting/text_span_test.dart

@@ -7,7 +7,7 @@ import 'package:flutter/painting.dart';
 import 'package:test/test.dart';
 
 void main() {
-  test("TextSpan equals", () {
+  test('TextSpan equals', () {
     TextSpan a1 = new TextSpan(text: 'a');
     TextSpan a2 = new TextSpan(text: 'a');
     TextSpan b1 = new TextSpan(children: <TextSpan>[ a1 ]);
@@ -28,7 +28,7 @@ void main() {
     expect(c1 == b2, isFalse);
   });
 
-  test("TextSpan ", () {
+  test('TextSpan', () {
     final TextSpan test = new TextSpan(
       text: 'a',
       style: new TextStyle(

packages/flutter/test/rendering/rendering_tester.dart

@@ -43,13 +43,20 @@ TestRenderingFlutterBinding get renderer {
   return _renderer;
 }
 
-void layout(RenderBox box, { BoxConstraints constraints, EnginePhase phase: EnginePhase.layout }) {
+/// Place the box in the render tree, at the given size and with the given
+/// alignment on the screen.
+void layout(RenderBox box, {
+  BoxConstraints constraints,
+  FractionalOffset alignment: FractionalOffset.center,
+  EnginePhase phase: EnginePhase.layout
+}) {
   assert(box != null); // If you want to just repump the last box, call pumpFrame().
   assert(box.parent == null); // We stick the box in another, so you can't reuse it easily, sorry.
 
   renderer.renderView.child = null;
   if (constraints != null) {
     box = new RenderPositionedBox(
+      alignment: alignment,
       child: new RenderConstrainedBox(
         additionalConstraints: constraints,
         child: box

packages/flutter/test/widget/fitted_box_test.dart

@@ -38,6 +38,7 @@ void main() {
     Point insidePoint = insideBox.localToGlobal(new Point(100.0, 50.0));
     Point outsidePoint = outsideBox.localToGlobal(new Point(200.0, 100.0));
 
+    expect(outsidePoint, equals(const Point(500.0, 350.0)));
     expect(insidePoint, equals(outsidePoint));
   });