Add CupertinoSwitch (#7326)

This patch contains a first draft of an iOS-style switch. We'll likely need to
tweak the constants upon closer study, but the basics are here.

packages/flutter/flutter.iml

@@ -9,6 +9,7 @@
       <excludeFolder url="file://$MODULE_DIR$/packages" />
       <excludeFolder url="file://$MODULE_DIR$/test/animation/packages" />
       <excludeFolder url="file://$MODULE_DIR$/test/cassowary/packages" />
+      <excludeFolder url="file://$MODULE_DIR$/test/cupertino/packages" />
       <excludeFolder url="file://$MODULE_DIR$/test/engine/packages" />
       <excludeFolder url="file://$MODULE_DIR$/test/examples/packages" />
       <excludeFolder url="file://$MODULE_DIR$/test/foundation/packages" />

packages/flutter/lib/cupertino.dart

+// Copyright 2017 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.
+
+/// Flutter widgets implementing the current iOS design language.
+///
+/// To use, import `package:flutter/cupertino.dart`.
+library cupertino;
+
+export 'src/cupertino/switch.dart';

packages/flutter/lib/src/material/switch.dart

@@ -290,12 +290,12 @@ class _RenderSwitch extends RenderToggleable {
   HorizontalDragGestureRecognizer _drag;
 
   void _handleDragStart(DragStartDetails details) {
-    if (onChanged != null)
+    if (isInteractive)
       reactionController.forward();
   }
 
   void _handleDragUpdate(DragUpdateDetails details) {
-    if (onChanged != null) {
+    if (isInteractive) {
       position
         ..curve = null
         ..reverseCurve = null;

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

@@ -526,13 +526,20 @@ class BoxShadow {
   /// The amount the box should be inflated prior to applying the blur.
   final double spreadRadius;
 
-  /// The [blurRadius] in sigmas instead of logical pixels.
+  /// Converts a blur radius in pixels to sigmas.
   ///
   /// See the sigma argument to [MaskFilter.blur].
-  ///
+  //
   // See SkBlurMask::ConvertRadiusToSigma().
   // <https://github.com/google/skia/blob/bb5b77db51d2e149ee66db284903572a5aac09be/src/effects/SkBlurMask.cpp#L23>
-  double get blurSigma => blurRadius * 0.57735 + 0.5;
+  static double convertRadiusToSigma(double radius) {
+    return radius * 0.57735 + 0.5;
+  }
+
+  /// The [blurRadius] in sigmas instead of logical pixels.
+  ///
+  /// See the sigma argument to [MaskFilter.blur].
+  double get blurSigma => convertRadiusToSigma(blurRadius);
 
   /// Returns a new box shadow with its offset, blurRadius, and spreadRadius scaled by the given factor.
   BoxShadow scale(double factor) {

packages/flutter/test/cupertino/switch_test.dart

+// Copyright 2017 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 'package:flutter/cupertino.dart';
+import 'package:flutter/widgets.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets('Switch can toggle on tap', (WidgetTester tester) async {
+    Key switchKey = new UniqueKey();
+    bool value = false;
+    await tester.pumpWidget(
+      new StatefulBuilder(
+        builder: (BuildContext context, StateSetter setState) {
+          return new Center(
+            child: new CupertinoSwitch(
+              key: switchKey,
+              value: value,
+              onChanged: (bool newValue) {
+                setState(() {
+                  value = newValue;
+                });
+              },
+            ),
+          );
+        },
+      ),
+    );
+
+    expect(value, isFalse);
+    await tester.tap(find.byKey(switchKey));
+    expect(value, isTrue);
+  });
+}

packages/flutter_tools/flutter_tools.iml

@@ -7,6 +7,21 @@
       <excludeFolder url="file://$MODULE_DIR$/bin/packages" />
       <excludeFolder url="file://$MODULE_DIR$/build" />
       <excludeFolder url="file://$MODULE_DIR$/packages" />
+      <excludeFolder url="file://$MODULE_DIR$/test/data/dart_dependencies_test/good/.pub" />
+      <excludeFolder url="file://$MODULE_DIR$/test/data/dart_dependencies_test/good/build" />
+      <excludeFolder url="file://$MODULE_DIR$/test/data/dart_dependencies_test/good/lib/packages" />
+      <excludeFolder url="file://$MODULE_DIR$/test/data/dart_dependencies_test/good/packages" />
+      <excludeFolder url="file://$MODULE_DIR$/test/data/dart_dependencies_test/packages" />
+      <excludeFolder url="file://$MODULE_DIR$/test/data/dart_dependencies_test/syntax_error/.pub" />
+      <excludeFolder url="file://$MODULE_DIR$/test/data/dart_dependencies_test/syntax_error/build" />
+      <excludeFolder url="file://$MODULE_DIR$/test/data/dart_dependencies_test/syntax_error/packages" />
+      <excludeFolder url="file://$MODULE_DIR$/test/data/intellij/packages" />
+      <excludeFolder url="file://$MODULE_DIR$/test/data/intellij/plugins/Dart/lib/packages" />
+      <excludeFolder url="file://$MODULE_DIR$/test/data/intellij/plugins/Dart/packages" />
+      <excludeFolder url="file://$MODULE_DIR$/test/data/intellij/plugins/packages" />
+      <excludeFolder url="file://$MODULE_DIR$/test/data/packages" />
+      <excludeFolder url="file://$MODULE_DIR$/test/data/process_manager/packages" />
+      <excludeFolder url="file://$MODULE_DIR$/test/data/process_manager/replay/packages" />
       <excludeFolder url="file://$MODULE_DIR$/test/packages" />
       <excludeFolder url="file://$MODULE_DIR$/test/src/ios/packages" />
       <excludeFolder url="file://$MODULE_DIR$/test/src/packages" />