IconThemeData.size (#4633)

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

@@ -26,29 +26,34 @@ import 'theme.dart';
 ///
 /// See also:
 ///
-///  * [IconButton], for interactive icons
+///  * [IconButton], for interactive icons.
-///  * [Icons], for the list of available icons for use with this class
+///  * [Icons], for the list of available icons for use with this class.
+///  * [IconTheme], which provides ambient configuration for icons.
 class Icon extends StatelessWidget {
   /// Creates an icon.
   ///
-  /// The [size] argument most not be null.
+  /// The [size] and [color] default to the value given by the current [IconTheme].
-  Icon({
+  const Icon({
     Key key,
     this.icon,
-    this.size: 24.0,
+    this.size,
     this.color
-  }) : super(key: key) {
+  }) : super(key: key);
-    assert(size != null);
+
-  }
+  /// The icon to display. The available icons are described in [Icons].
+  ///
+  /// If null, no icon is shown.
+  final IconData icon;
 
   /// The size of the icon in logical pixels.
   ///
   /// Icons occupy a square with width and height equal to size.
+  ///
+  /// Defaults to the current [IconTheme] size, if any. If there is no
+  /// [IconTheme], or it does not specify an explicit size, then it defaults to
+  /// 24.0.
   final double size;
 
-  /// The icon to display. The available icons are described in [Icons].
-  final IconData icon;
-
   /// The color to use when drawing the icon.
   ///
   /// Defaults to the current [IconTheme] color, if any. If there is
@@ -56,6 +61,9 @@ class Icon extends StatelessWidget {
   /// and black if the theme is light. See [Theme] to set the current
   /// theme and [ThemeData.brightness] for setting the current theme's
   /// brightness.
+  ///
+  /// The given color will be adjusted by the opacity of the current
+  /// [IconTheme], if any.
   final Color color;
 
   Color _getDefaultColorForBrightness(Brightness brightness) {
@@ -75,8 +83,10 @@ class Icon extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    final double iconSize = size ?? IconTheme.of(context)?.size ?? 24.0;
+
     if (icon == null)
-      return new SizedBox(width: size, height: size);
+      return new SizedBox(width: iconSize, height: iconSize);
 
     final double iconOpacity = IconTheme.of(context)?.opacity ?? 1.0;
     Color iconColor = color ?? _getDefaultColor(context);
@@ -85,15 +95,15 @@ class Icon extends StatelessWidget {
 
     return new ExcludeSemantics(
       child: new SizedBox(
-        width: size,
+        width: iconSize,
-        height: size,
+        height: iconSize,
         child: new Center(
           child: new Text(
             new String.fromCharCode(icon.codePoint),
             style: new TextStyle(
               inherit: false,
               color: iconColor,
-              fontSize: size,
+              fontSize: iconSize,
               fontFamily: 'MaterialIcons'
             )
           )
@@ -105,9 +115,14 @@ class Icon extends StatelessWidget {
   @override
   void debugFillDescription(List<String> description) {
     super.debugFillDescription(description);
-    description.add('$icon');
+    if (icon != null) {
-    description.add('size: $size');
+      description.add('$icon');
-    if (this.color != null)
+    } else {
+      description.add('<empty>');
+    }
+    if (size != null)
+      description.add('size: $size');
+    if (color != null)
       description.add('color: $color');
   }
 }

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

@@ -7,9 +7,10 @@ import 'package:meta/meta.dart';
 
 import 'icon_theme_data.dart';
 
-/// Controls the color and opacity of icons in a widget subtree.
+/// Controls the default color, opacity, and size of icons in a widget subtree.
 class IconTheme extends InheritedWidget {
-  /// Creates an icon theme that controls the color and opacity of descendant widgets.
+  /// Creates an icon theme that controls the color, opacity, and size of
+  /// descendant widgets.
   ///
   /// Both [data] and [child] arguments must not be null.
   IconTheme({
@@ -21,7 +22,7 @@ class IconTheme extends InheritedWidget {
     assert(child != null);
   }
 
-  /// The color and opacity to use for icons in this subtree.
+  /// The color, opacity, and size to use for icons in this subtree.
   final IconThemeData data;
 
   /// The data from the closest instance of this class that encloses the given context.

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

@@ -5,16 +5,16 @@
 import 'dart:ui' as ui show lerpDouble;
 import 'dart:ui' show Color, hashValues;
 
-/// Defines the color and opacity of icons.
+/// Defines the color, opacity, and size of icons.
 ///
-/// Used by [IconTheme] to control the color and opacity of icons in a widget
+/// Used by [IconTheme] to control the color, opacity, and size of icons in a
-/// subtree.
+/// widget subtree.
 class IconThemeData {
   /// Creates an icon theme data.
   ///
   /// The opacity applies to both explicit and default icon colors. The value
   /// is clamped between 0.0 and 1.0.
-  const IconThemeData({ this.color, double opacity: 1.0 }) : _opacity = opacity;
+  const IconThemeData({ this.color, double opacity: 1.0, this.size }) : _opacity = opacity;
 
   /// The default color for icons.
   final Color color;
@@ -23,25 +23,42 @@ class IconThemeData {
   double get opacity => (_opacity ?? 1.0).clamp(0.0, 1.0);
   final double _opacity;
 
+  /// The default size for icons.
+  final double size;
+
   /// Linearly interpolate between two icon theme data objects.
   static IconThemeData lerp(IconThemeData begin, IconThemeData end, double t) {
     return new IconThemeData(
       color: Color.lerp(begin.color, end.color, t),
-      opacity: ui.lerpDouble(begin.opacity, end.opacity, t)
+      opacity: ui.lerpDouble(begin.opacity, end.opacity, t),
+      size: ui.lerpDouble(begin.size, end.size, t)
     );
   }
 
   @override
   bool operator ==(dynamic other) {
-    if (other is! IconThemeData)
+    if (other.runtimeType != runtimeType)
       return false;
     final IconThemeData typedOther = other;
-    return color == typedOther.color && opacity == typedOther.opacity;
+    return color == typedOther.color
+        && opacity == typedOther.opacity
+        && size == typedOther.size;
   }
 
   @override
-  int get hashCode => hashValues(color, opacity);
+  int get hashCode => hashValues(color, opacity, size);
 
   @override
-  String toString() => '$color';
+  String toString() {
+    List<String> result = <String>[];
+    if (color != null)
+      result.add('color: $color');
+    if (opacity != 1.0)
+      result.add('opacity: $opacity');
+    if (size != null)
+      result.add('size: $size');
+    if (result.length == 0)
+      return '<no theme>';
+    return result.join(', ');
+  }
 }

packages/flutter/test/material/icon_test.dart

@@ -0,0 +1,78 @@
+// 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/rendering.dart';
+import 'package:flutter/widgets.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets('Icon sizing - no theme, default size', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      new Center(
+        child: new Icon()
+      )
+    );
+
+    RenderBox renderObject = tester.renderObject(find.byType(Icon));
+    expect(renderObject.size, equals(const Size.square(24.0)));
+  });
+
+  testWidgets('Icon sizing - no theme, explicit size', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      new Center(
+        child: new Icon(
+          size: 96.0
+        )
+      )
+    );
+
+    RenderBox renderObject = tester.renderObject(find.byType(Icon));
+    expect(renderObject.size, equals(const Size.square(96.0)));
+  });
+
+  testWidgets('Icon sizing - sized theme', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      new Center(
+        child: new IconTheme(
+          data: new IconThemeData(size: 36.0),
+          child: new Icon()
+        )
+      )
+    );
+
+    RenderBox renderObject = tester.renderObject(find.byType(Icon));
+    expect(renderObject.size, equals(const Size.square(36.0)));
+  });
+
+  testWidgets('Icon sizing - sized theme, explicit size', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      new Center(
+        child: new IconTheme(
+          data: new IconThemeData(size: 36.0),
+          child: new Icon(
+            size: 48.0
+          )
+        )
+      )
+    );
+
+    RenderBox renderObject = tester.renderObject(find.byType(Icon));
+    expect(renderObject.size, equals(const Size.square(48.0)));
+  });
+
+  testWidgets('Icon sizing - sizeless theme, default size', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      new Center(
+        child: new IconTheme(
+          data: new IconThemeData(),
+          child: new Icon()
+        )
+      )
+    );
+
+    RenderBox renderObject = tester.renderObject(find.byType(Icon));
+    expect(renderObject.size, equals(const Size.square(24.0)));
+  });
+}