Refactor IconThemeData.fallback (#7490)

Now IconThemeData.fallback is a factory constructor and IconThemeData.of() does
the work of computing the fallback for its clients.

Also, add tests for ImageIcon and ListItems.

examples/flutter_gallery/lib/demo/bottom_navigation_demo.dart

@@ -66,7 +66,7 @@ class NavigationIconView {
 class CustomIcon extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
-    final IconThemeData iconTheme = IconTheme.of(context).fallback();
+    final IconThemeData iconTheme = IconTheme.of(context);
     return new Container(
       margin: const EdgeInsets.all(4.0),
       width: iconTheme.size - 8.0,

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

@@ -73,7 +73,7 @@ class FlutterLogo extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final IconThemeData iconTheme = IconTheme.of(context).fallback();
+    final IconThemeData iconTheme = IconTheme.of(context);
     final double iconSize = size ?? iconTheme.size;
     return new AnimatedContainer(
       width: iconSize,

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

@@ -80,7 +80,7 @@ class Icon extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final IconThemeData iconTheme = IconTheme.of(context).fallback();
+    final IconThemeData iconTheme = IconTheme.of(context);
 
     final double iconSize = size ?? iconTheme.size;
 

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

@@ -37,7 +37,7 @@ class IconTheme extends InheritedWidget {
   }) {
     return new IconTheme(
       key: key,
-      data: IconTheme.of(context).merge(data),
+      data: _getInheritedIconThemData(context).merge(data),
       child: child
     );
   }
@@ -56,8 +56,13 @@ class IconTheme extends InheritedWidget {
   /// IconThemeData theme = IconTheme.of(context);
   /// ```
   static IconThemeData of(BuildContext context) {
-    IconTheme result = context.inheritFromWidgetOfExactType(IconTheme);
-    return result?.data ?? Theme.of(context).iconTheme;
+    IconThemeData iconThemeData = _getInheritedIconThemData(context);
+    return iconThemeData.isConcrete ? iconThemeData : const IconThemeData.fallback().merge(iconThemeData);
+  }
+
+  static IconThemeData _getInheritedIconThemData(BuildContext context) {
+    IconTheme iconTheme = context.inheritFromWidgetOfExactType(IconTheme);
+    return iconTheme?.data ?? Theme.of(context).iconTheme;
   }
 
   @override

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

@@ -19,6 +19,14 @@ class IconThemeData {
   /// is clamped between 0.0 and 1.0.
   const IconThemeData({ this.color, double opacity, this.size }) : _opacity = opacity;
 
+  /// Creates an icon them with some reasonable default values.
+  ///
+  /// The [color] is black, the [opacity] is 1.0, and the [size] is 24.0.
+  const IconThemeData.fallback()
+    : color = const Color(0xFF000000),
+      _opacity = 1.0,
+      size = 24.0;
+
   /// Creates a copy of this icon theme but with the given fields replaced with
   /// the new values.
   IconThemeData copyWith({ Color color, double opacity, double size }) {
@@ -42,22 +50,8 @@ class IconThemeData {
     );
   }
 
-  /// Creates an icon theme that is identical to this icon theme but with
-  /// any null fields filled in. Specific fallbacks can be given, but in their
-  /// absence, this method defaults to black, fully opaque, and size 24.0.
-  IconThemeData fallback({
-    Color color: const Color(0xFF000000),
-    double opacity: 1.0,
-    double size: 24.0
-  }) {
-    if (this.color != null && this.opacity != null && this.size != null)
-      return this;
-    return new IconThemeData(
-      color: this.color ?? color,
-      opacity: this.opacity ?? opacity,
-      size: this.size ?? size
-    );
-  }
+  /// Whether all the properties of this object are non-null.
+  bool get isConcrete => color != null && opacity != null && size != null;
 
   /// The default color for icons.
   final Color color;

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

@@ -53,7 +53,7 @@ class ImageIcon extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final IconThemeData iconTheme = IconTheme.of(context).fallback();
+    final IconThemeData iconTheme = IconTheme.of(context);
 
     final double iconSize = size ?? iconTheme.size;
 

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

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'package:flutter/widgets.dart';
+import 'package:meta/meta.dart';
 
 import 'constants.dart';
 import 'debug.dart';
@@ -104,7 +105,7 @@ class ListItem extends StatelessWidget {
   /// See also:
   ///
   /// * [Divider], which you can use to obtain this effect manually.
-  static Iterable<Widget> divideItems({ BuildContext context, Iterable<Widget> items, Color color }) sync* {
+  static Iterable<Widget> divideItems({ BuildContext context, @required Iterable<Widget> items, Color color }) sync* {
     assert(items != null);
     assert(color != null || context != null);
 

packages/flutter/test/material/bottom_navigation_bar_test.dart

@@ -256,7 +256,7 @@ void main() {
               title: new Text('B'),
               icon: new Builder(
                 builder: (BuildContext context) {
-                  builderIconSize = IconTheme.of(context).fallback().size;
+                  builderIconSize = IconTheme.of(context).size;
                   return new SizedBox(
                     width: builderIconSize,
                     height: builderIconSize,

packages/flutter/test/material/image_icon_test.dart

@@ -4,19 +4,40 @@
 
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
+import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 
+import '../services/mocks_for_image_cache.dart';
+
+const ImageProvider _kImage = const TestImageProvider(21, 42);
+
 void main() {
   testWidgets('ImageIcon sizing - no theme, default size', (WidgetTester tester) async {
     await tester.pumpWidget(
       new Center(
-        child: const ImageIcon(null)
+        child: const ImageIcon(_kImage)
       )
     );
 
     RenderBox renderObject = tester.renderObject(find.byType(ImageIcon));
     expect(renderObject.size, equals(const Size.square(24.0)));
+    expect(find.byType(Image), findsOneWidget);
+  });
+
+  testWidgets('Icon opacity', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      new Center(
+        child: new IconTheme(
+          data: new IconThemeData(opacity: 0.5),
+          child: const ImageIcon(_kImage),
+        ),
+      ),
+    );
+
+    Image image = tester.widget(find.byType(Image));
+    expect(image, isNotNull);
+    expect(image.color.alpha, equals(128));
   });
 
   testWidgets('ImageIcon sizing - no theme, explicit size', (WidgetTester tester) async {

packages/flutter/test/material/list_item_test.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 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets('ListItem control test', (WidgetTester tester) async {
+    await tester.pumpWidget(new MaterialApp(
+      home: new Material(
+        child: new Center(
+          child: new ListItem(
+            leading: new Icon(Icons.thumb_up),
+            title: new Text('Title'),
+            subtitle: new Text('Subtitle'),
+            trailing: new Icon(Icons.info),
+            enabled: false,
+          ),
+        ),
+      ),
+    ));
+
+    expect(find.text('Title'), findsOneWidget);
+    expect(find.text('Subtitle'), findsOneWidget);
+  });
+
+  testWidgets('ListItem control test', (WidgetTester tester) async {
+    List<String> titles = <String>[ 'first', 'second', 'third' ];
+
+    await tester.pumpWidget(new MaterialApp(
+      home: new Material(
+        child: new Builder(
+          builder: (BuildContext context) {
+            return new Block(
+              children: ListItem.divideItems(
+                context: context,
+                items: titles.map((String title) => new ListItem(title: new Text(title))),
+              ).toList(),
+            );
+          },
+        ),
+      ),
+    ));
+
+    expect(find.text('first'), findsOneWidget);
+    expect(find.text('second'), findsOneWidget);
+    expect(find.text('third'), findsOneWidget);
+  });
+}

packages/flutter/test/material/time_picker_test.dart

@@ -37,18 +37,13 @@ class _TimePickerLauncher extends StatelessWidget {
 Future<Point> startPicker(WidgetTester tester, ValueChanged<TimeOfDay> onChanged) async {
   await tester.pumpWidget(new _TimePickerLauncher(onChanged: onChanged));
   await tester.tap(find.text('X'));
-
-  await tester.pump(); // start animation
-  await tester.pump(const Duration(seconds: 1));
-
+  await tester.pumpUntilNoTransientCallbacks(const Duration(seconds: 1));
   return tester.getCenter(find.byKey(new Key('time-picker-dial')));
 }
 
 Future<Null> finishPicker(WidgetTester tester) async {
   await tester.tap(find.text('OK'));
-
-  await tester.pump(); // start animation
-  await tester.pump(const Duration(seconds: 1));
+  await tester.pumpUntilNoTransientCallbacks(const Duration(seconds: 1));
 }
 
 void main() {

packages/flutter/test/services/image_cache_resize_test.dart

@@ -12,10 +12,10 @@ void main() {
 
     imageCache.maximumSize = 2;
 
-    TestImageInfo a = await extractOneFrame(const TestProvider(1, 1).resolve(ImageConfiguration.empty));
-    TestImageInfo b = await extractOneFrame(const TestProvider(2, 2).resolve(ImageConfiguration.empty));
-    TestImageInfo c = await extractOneFrame(const TestProvider(3, 3).resolve(ImageConfiguration.empty));
-    TestImageInfo d = await extractOneFrame(const TestProvider(1, 4).resolve(ImageConfiguration.empty));
+    TestImageInfo a = await extractOneFrame(const TestImageProvider(1, 1).resolve(ImageConfiguration.empty));
+    TestImageInfo b = await extractOneFrame(const TestImageProvider(2, 2).resolve(ImageConfiguration.empty));
+    TestImageInfo c = await extractOneFrame(const TestImageProvider(3, 3).resolve(ImageConfiguration.empty));
+    TestImageInfo d = await extractOneFrame(const TestImageProvider(1, 4).resolve(ImageConfiguration.empty));
     expect(a.value, equals(1));
     expect(b.value, equals(2));
     expect(c.value, equals(3));
@@ -23,18 +23,18 @@ void main() {
 
     imageCache.maximumSize = 0;
 
-    TestImageInfo e = await extractOneFrame(const TestProvider(1, 5).resolve(ImageConfiguration.empty));
+    TestImageInfo e = await extractOneFrame(const TestImageProvider(1, 5).resolve(ImageConfiguration.empty));
     expect(e.value, equals(5));
 
-    TestImageInfo f = await extractOneFrame(const TestProvider(1, 6).resolve(ImageConfiguration.empty));
+    TestImageInfo f = await extractOneFrame(const TestImageProvider(1, 6).resolve(ImageConfiguration.empty));
     expect(f.value, equals(6));
 
     imageCache.maximumSize = 3;
 
-    TestImageInfo g = await extractOneFrame(const TestProvider(1, 7).resolve(ImageConfiguration.empty));
+    TestImageInfo g = await extractOneFrame(const TestImageProvider(1, 7).resolve(ImageConfiguration.empty));
     expect(g.value, equals(7));
 
-    TestImageInfo h = await extractOneFrame(const TestProvider(1, 8).resolve(ImageConfiguration.empty));
+    TestImageInfo h = await extractOneFrame(const TestImageProvider(1, 8).resolve(ImageConfiguration.empty));
     expect(h.value, equals(7));
 
   });

packages/flutter/test/services/image_cache_test.dart

@@ -12,69 +12,69 @@ void main() {
 
     imageCache.maximumSize = 3;
 
-    TestImageInfo a = await extractOneFrame(const TestProvider(1, 1).resolve(ImageConfiguration.empty));
+    TestImageInfo a = await extractOneFrame(const TestImageProvider(1, 1).resolve(ImageConfiguration.empty));
     expect(a.value, equals(1));
-    TestImageInfo b = await extractOneFrame(const TestProvider(1, 2).resolve(ImageConfiguration.empty));
+    TestImageInfo b = await extractOneFrame(const TestImageProvider(1, 2).resolve(ImageConfiguration.empty));
     expect(b.value, equals(1));
-    TestImageInfo c = await extractOneFrame(const TestProvider(1, 3).resolve(ImageConfiguration.empty));
+    TestImageInfo c = await extractOneFrame(const TestImageProvider(1, 3).resolve(ImageConfiguration.empty));
     expect(c.value, equals(1));
-    TestImageInfo d = await extractOneFrame(const TestProvider(1, 4).resolve(ImageConfiguration.empty));
+    TestImageInfo d = await extractOneFrame(const TestImageProvider(1, 4).resolve(ImageConfiguration.empty));
     expect(d.value, equals(1));
-    TestImageInfo e = await extractOneFrame(const TestProvider(1, 5).resolve(ImageConfiguration.empty));
+    TestImageInfo e = await extractOneFrame(const TestImageProvider(1, 5).resolve(ImageConfiguration.empty));
     expect(e.value, equals(1));
-    TestImageInfo f = await extractOneFrame(const TestProvider(1, 6).resolve(ImageConfiguration.empty));
+    TestImageInfo f = await extractOneFrame(const TestImageProvider(1, 6).resolve(ImageConfiguration.empty));
     expect(f.value, equals(1));
 
     expect(f, equals(a));
 
     // cache still only has one entry in it: 1(1)
 
-    TestImageInfo g = await extractOneFrame(const TestProvider(2, 7).resolve(ImageConfiguration.empty));
+    TestImageInfo g = await extractOneFrame(const TestImageProvider(2, 7).resolve(ImageConfiguration.empty));
     expect(g.value, equals(7));
 
     // cache has two entries in it: 1(1), 2(7)
 
-    TestImageInfo h = await extractOneFrame(const TestProvider(1, 8).resolve(ImageConfiguration.empty));
+    TestImageInfo h = await extractOneFrame(const TestImageProvider(1, 8).resolve(ImageConfiguration.empty));
     expect(h.value, equals(1));
 
     // cache still has two entries in it: 2(7), 1(1)
 
-    TestImageInfo i = await extractOneFrame(const TestProvider(3, 9).resolve(ImageConfiguration.empty));
+    TestImageInfo i = await extractOneFrame(const TestImageProvider(3, 9).resolve(ImageConfiguration.empty));
     expect(i.value, equals(9));
 
     // cache has three entries in it: 2(7), 1(1), 3(9)
 
-    TestImageInfo j = await extractOneFrame(const TestProvider(1, 10).resolve(ImageConfiguration.empty));
+    TestImageInfo j = await extractOneFrame(const TestImageProvider(1, 10).resolve(ImageConfiguration.empty));
     expect(j.value, equals(1));
 
     // cache still has three entries in it: 2(7), 3(9), 1(1)
 
-    TestImageInfo k = await extractOneFrame(const TestProvider(4, 11).resolve(ImageConfiguration.empty));
+    TestImageInfo k = await extractOneFrame(const TestImageProvider(4, 11).resolve(ImageConfiguration.empty));
     expect(k.value, equals(11));
 
     // cache has three entries: 3(9), 1(1), 4(11)
 
-    TestImageInfo l = await extractOneFrame(const TestProvider(1, 12).resolve(ImageConfiguration.empty));
+    TestImageInfo l = await extractOneFrame(const TestImageProvider(1, 12).resolve(ImageConfiguration.empty));
     expect(l.value, equals(1));
 
     // cache has three entries: 3(9), 4(11), 1(1)
 
-    TestImageInfo m = await extractOneFrame(const TestProvider(2, 13).resolve(ImageConfiguration.empty));
+    TestImageInfo m = await extractOneFrame(const TestImageProvider(2, 13).resolve(ImageConfiguration.empty));
     expect(m.value, equals(13));
 
     // cache has three entries: 4(11), 1(1), 2(13)
 
-    TestImageInfo n = await extractOneFrame(const TestProvider(3, 14).resolve(ImageConfiguration.empty));
+    TestImageInfo n = await extractOneFrame(const TestImageProvider(3, 14).resolve(ImageConfiguration.empty));
     expect(n.value, equals(14));
 
     // cache has three entries: 1(1), 2(13), 3(14)
 
-    TestImageInfo o = await extractOneFrame(const TestProvider(4, 15).resolve(ImageConfiguration.empty));
+    TestImageInfo o = await extractOneFrame(const TestImageProvider(4, 15).resolve(ImageConfiguration.empty));
     expect(o.value, equals(15));
 
     // cache has three entries: 2(13), 3(14), 4(15)
 
-    TestImageInfo p = await extractOneFrame(const TestProvider(1, 16).resolve(ImageConfiguration.empty));
+    TestImageInfo p = await extractOneFrame(const TestImageProvider(1, 16).resolve(ImageConfiguration.empty));
     expect(p.value, equals(16));
 
     // cache has three entries: 3(14), 4(15), 1(16)

packages/flutter/test/services/mocks_for_image_cache.dart

@@ -23,8 +23,8 @@ class TestImageInfo implements ImageInfo {
   String toString() => '$runtimeType($value)';
 }
 
-class TestProvider extends ImageProvider<int> {
-  const TestProvider(this.key, this.imageValue);
+class TestImageProvider extends ImageProvider<int> {
+  const TestImageProvider(this.key, this.imageValue);
   final int key;
   final int imageValue;