Add MediaQuery.textScaleFactor (#5936)

This feature is the implementation of an accessibility feature that changes the
size of text by a constant factor.

Fixes #5873

examples/stocks/test/icon_color_test.dart

@@ -43,9 +43,9 @@ void checkIconColor(WidgetTester tester, String label, Color color) {
   // way to find the menu item. I hope.
   Element semantics = findElementOfExactWidgetTypeGoingUp(tester.element(find.text(label)), MergeSemantics);
   expect(semantics, isNotNull);
-  Element asset = findElementOfExactWidgetTypeGoingDown(semantics, Text);
-  Text text = asset.widget;
-  expect(text.style.color, equals(color));
+  Element asset = findElementOfExactWidgetTypeGoingDown(semantics, RichText);
+  RichText richText = asset.widget;
+  expect(richText.text.style.color, equals(color));
 }
 
 void main() {

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

@@ -86,13 +86,15 @@ class Icon extends StatelessWidget {
         width: iconSize,
         height: iconSize,
         child: new Center(
-          child: new Text(
-            new String.fromCharCode(icon.codePoint),
-            style: new TextStyle(
-              inherit: false,
-              color: iconColor,
-              fontSize: iconSize,
-              fontFamily: 'MaterialIcons'
+          child: new RichText(
+            text: new TextSpan(
+              text: new String.fromCharCode(icon.codePoint),
+              style: new TextStyle(
+                inherit: false,
+                color: iconColor,
+                fontSize: iconSize,
+                fontFamily: 'MaterialIcons'
+              )
             )
           )
         )

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

@@ -251,6 +251,8 @@ class _RenderSlider extends RenderConstrainedBox implements SemanticActionHandle
     _label = newLabel;
     additionalConstraints = _getAdditionalConstraints(_label);
     if (newLabel != null) {
+      // TODO(abarth): Handle textScaleFactor.
+      // https://github.com/flutter/flutter/issues/5938
       _labelPainter
         ..text = new TextSpan(
           style: Typography.white.body1.copyWith(fontSize: 10.0),

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

@@ -301,6 +301,8 @@ List<TextPainter> _initPainters(TextTheme textTheme, List<String> labels) {
   List<TextPainter> painters = new List<TextPainter>(labels.length);
   for (int i = 0; i < painters.length; ++i) {
     String label = labels[i];
+    // TODO(abarth): Handle textScaleFactor.
+    // https://github.com/flutter/flutter/issues/5939
     painters[i] = new TextPainter(
       text: new TextSpan(style: style, text: label)
     )..layout();

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

@@ -32,9 +32,11 @@ class TextPainter {
   /// [layout].
   TextPainter({
     TextSpan text,
-    TextAlign textAlign
-  }) : _text = text, _textAlign = textAlign {
+    TextAlign textAlign,
+    double textScaleFactor: 1.0
+  }) : _text = text, _textAlign = textAlign, _textScaleFactor = textScaleFactor {
     assert(text == null || text.debugAssertIsValid());
+    assert(textScaleFactor != null);
   }
 
   ui.Paragraph _paragraph;
@@ -63,6 +65,21 @@ class TextPainter {
     _needsLayout = true;
   }
 
+  /// The number of font pixels for each logical pixel.
+  ///
+  /// For example, if the text scale factor is 1.5, text will be 50% larger than
+  /// the specified font size.
+  double get textScaleFactor => _textScaleFactor;
+  double _textScaleFactor;
+  set textScaleFactor(double value) {
+    assert(value != null);
+    if (_textScaleFactor == value)
+      return;
+    _textScaleFactor = value;
+    _paragraph = null;
+    _needsLayout = true;
+  }
+
   // Unfortunately, using full precision floating point here causes bad layouts
   // because floating point math isn't associative. If we add and subtract
   // padding, for example, we'll get different values when we estimate sizes and
@@ -144,8 +161,8 @@ class TextPainter {
     _needsLayout = false;
     if (_paragraph == null) {
       ui.ParagraphBuilder builder = new ui.ParagraphBuilder();
-      _text.build(builder);
-      ui.ParagraphStyle paragraphStyle = _text.style?.getParagraphStyle(textAlign: textAlign);
+      _text.build(builder, textScaleFactor: textScaleFactor);
+      ui.ParagraphStyle paragraphStyle = _text.style?.getParagraphStyle(textAlign: textAlign, textScaleFactor: textScaleFactor);
       paragraphStyle ??= new ui.ParagraphStyle();
       _paragraph = builder.build(paragraphStyle);
     }

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

@@ -93,17 +93,17 @@ class TextSpan {
   /// Rather than using this directly, it's simpler to use the
   /// [TextPainter] class to paint [TextSpan] objects onto [Canvas]
   /// objects.
-  void build(ui.ParagraphBuilder builder) {
+  void build(ui.ParagraphBuilder builder, { double textScaleFactor: 1.0 }) {
     assert(debugAssertIsValid());
     final bool hasStyle = style != null;
     if (hasStyle)
-      builder.pushStyle(style.textStyle);
+      builder.pushStyle(style.getTextStyle(textScaleFactor: textScaleFactor));
     if (text != null)
       builder.addText(text);
     if (children != null) {
       for (TextSpan child in children) {
         assert(child != null);
-        child.build(builder);
+        child.build(builder, textScaleFactor: textScaleFactor);
       }
     }
     if (hasStyle)

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

@@ -35,6 +35,10 @@ class TextStyle {
   final String fontFamily;
 
   /// The size of gyphs (in logical pixels) to use when painting the text.
+  ///
+  /// During painting, the [fontSize] is multiplied by the current
+  /// `textScaleFactor` to let users make it easier to read text by increasing
+  /// its size.
   final double fontSize;
 
   /// The typeface thickness to use when painting the text (e.g., bold).
@@ -207,7 +211,7 @@ class TextStyle {
   }
 
   /// The style information for text runs, encoded for use by `dart:ui`.
-  ui.TextStyle get textStyle {
+  ui.TextStyle getTextStyle({ double textScaleFactor: 1.0 }) {
     return new ui.TextStyle(
       color: color,
       decoration: decoration,
@@ -217,7 +221,7 @@ class TextStyle {
       fontStyle: fontStyle,
       textBaseline: textBaseline,
       fontFamily: fontFamily,
-      fontSize: fontSize,
+      fontSize: fontSize == null ? null : fontSize * textScaleFactor,
       letterSpacing: letterSpacing,
       wordSpacing: wordSpacing,
       height: height
@@ -225,13 +229,13 @@ class TextStyle {
   }
 
   /// The style information for paragraphs, encoded for use by `dart:ui`.
-  ui.ParagraphStyle getParagraphStyle({ TextAlign textAlign }) {
+  ui.ParagraphStyle getParagraphStyle({ TextAlign textAlign, double textScaleFactor: 1.0 }) {
     return new ui.ParagraphStyle(
       textAlign: textAlign,
       fontWeight: fontWeight,
       fontStyle: fontStyle,
       fontFamily: fontFamily,
-      fontSize: fontSize,
+      fontSize: fontSize == null ? null : fontSize * textScaleFactor,
       lineHeight: height
     );
   }

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

@@ -44,11 +44,12 @@ class RenderEditableLine extends RenderBox {
     Color cursorColor,
     bool showCursor: false,
     Color selectionColor,
+    double textScaleFactor: 1.0,
     TextSelection selection,
     this.onSelectionChanged,
     Offset paintOffset: Offset.zero,
     this.onPaintOffsetUpdateNeeded
-  }) : _textPainter = new TextPainter(text: text),
+  }) : _textPainter = new TextPainter(text: text, textScaleFactor: textScaleFactor),
        _cursorColor = cursorColor,
        _showCursor = showCursor,
        _selection = selection,
@@ -111,6 +112,19 @@ class RenderEditableLine extends RenderBox {
     markNeedsPaint();
   }
 
+  /// The number of font pixels for each logical pixel.
+  ///
+  /// For example, if the text scale factor is 1.5, text will be 50% larger than
+  /// the specified font size.
+  double get textScaleFactor => _textPainter.textScaleFactor;
+  set textScaleFactor(double value) {
+    assert(value != null);
+    if (_textPainter.textScaleFactor == value)
+      return;
+    _textPainter.textScaleFactor = value;
+    markNeedsLayout();
+  }
+
   List<ui.TextBox> _selectionRects;
 
   /// The region of text that is selected, if any.
@@ -181,7 +195,7 @@ class RenderEditableLine extends RenderBox {
   double get _preferredHeight {
     if (_layoutTemplate == null) {
       ui.ParagraphBuilder builder = new ui.ParagraphBuilder()
-        ..pushStyle(text.style.textStyle)
+        ..pushStyle(text.style.getTextStyle(textScaleFactor: textScaleFactor))
         ..addText(_kZeroWidthSpace);
       // TODO(abarth): ParagraphBuilder#build's argument should be optional.
       // TODO(abarth): These min/max values should be the default for ui.Paragraph.

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

@@ -29,15 +29,17 @@ class RenderParagraph extends RenderBox {
   /// The [text], [overflow], and [softWrap] arguments must not be null.
   RenderParagraph(TextSpan text, {
     TextAlign textAlign,
+    bool softWrap: true,
     TextOverflow overflow: TextOverflow.clip,
-    bool softWrap: true
+    double textScaleFactor: 1.0
   }) : _softWrap = softWrap,
        _overflow = overflow,
-       _textPainter = new TextPainter(text: text, textAlign: textAlign) {
+       _textPainter = new TextPainter(text: text, textAlign: textAlign, textScaleFactor: textScaleFactor) {
     assert(text != null);
     assert(text.debugAssertIsValid());
-    assert(overflow != null);
     assert(softWrap != null);
+    assert(overflow != null);
+    assert(textScaleFactor != null);
   }
 
   final TextPainter _textPainter;
@@ -87,6 +89,21 @@ class RenderParagraph extends RenderBox {
     markNeedsPaint();
   }
 
+  /// The number of font pixels for each logical pixel.
+  ///
+  /// For example, if the text scale factor is 1.5, text will be 50% larger than
+  /// the specified font size.
+  double get textScaleFactor => _textPainter.textScaleFactor;
+  set textScaleFactor(double value) {
+    assert(value != null);
+    if (_textPainter.textScaleFactor == value)
+      return;
+    _textPainter.textScaleFactor = value;
+    _overflowPainter = null;
+    _overflowShader = null;
+    markNeedsLayout();
+  }
+
   void _layoutText({ double minWidth: 0.0, double maxWidth: double.INFINITY }) {
     _textPainter.layout(minWidth: minWidth, maxWidth: _softWrap ? maxWidth : double.INFINITY);
   }
@@ -171,7 +188,8 @@ class RenderParagraph extends RenderBox {
         case TextOverflow.fade:
         case TextOverflow.ellipsis:
           _overflowPainter ??= new TextPainter(
-            text: new TextSpan(style: _textPainter.text.style, text: '\u2026')
+            text: new TextSpan(style: _textPainter.text.style, text: '\u2026'),
+            textScaleFactor: textScaleFactor
           )..layout();
           final double overflowUnit = _overflowPainter.width;
           double fadeEnd = size.width;

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

@@ -18,6 +18,7 @@ import 'media_query.dart';
 import 'navigator.dart';
 import 'performance_overlay.dart';
 import 'semantics_debugger.dart';
+import 'text.dart';
 import 'title.dart';
 
 /// Signature for a function that is called when the operating system changes the current locale.
@@ -183,7 +184,7 @@ class _WidgetsAppState extends State<WidgetsApp> implements WidgetsBindingObserv
       )
     );
     if (config.textStyle != null) {
-      new DefaultTextStyle(
+      result = new DefaultTextStyle(
         style: config.textStyle,
         child: result
       );

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

@@ -2128,11 +2128,13 @@ class RichText extends LeafRenderObjectWidget {
     @required this.text,
     this.textAlign,
     this.softWrap: true,
-    this.overflow: TextOverflow.clip
+    this.overflow: TextOverflow.clip,
+    this.textScaleFactor: 1.0
   }) : super(key: key) {
     assert(text != null);
     assert(softWrap != null);
     assert(overflow != null);
+    assert(textScaleFactor != null);
   }
 
   /// The text to display in this widget.
@@ -2149,12 +2151,19 @@ class RichText extends LeafRenderObjectWidget {
   /// How visual overflow should be handled.
   final TextOverflow overflow;
 
+  /// The number of font pixels for each logical pixel.
+  ///
+  /// For example, if the text scale factor is 1.5, text will be 50% larger than
+  /// the specified font size.
+  final double textScaleFactor;
+
   @override
   RenderParagraph createRenderObject(BuildContext context) {
     return new RenderParagraph(text,
       textAlign: textAlign,
       softWrap: softWrap,
-      overflow: overflow
+      overflow: overflow,
+      textScaleFactor: textScaleFactor
     );
   }
 
@@ -2164,178 +2173,8 @@ class RichText extends LeafRenderObjectWidget {
       ..text = text
       ..textAlign = textAlign
       ..softWrap = softWrap
-      ..overflow = overflow;
-  }
-}
-
-/// The text style to apply to descendant [Text] widgets without explicit style.
-class DefaultTextStyle extends InheritedWidget {
-  /// Creates a default text style for the given subtree.
-  ///
-  /// Consider using [DefaultTextStyle.inherit] to inherit styling information
-  /// from a the current default text style for a given [BuildContext].
-  DefaultTextStyle({
-    Key key,
-    @required this.style,
-    this.textAlign,
-    this.softWrap: true,
-    this.overflow: TextOverflow.clip,
-    Widget child
-  }) : super(key: key, child: child) {
-    assert(style != null);
-    assert(softWrap != null);
-    assert(overflow != null);
-    assert(child != null);
-  }
-
-  /// A const-constructible default text style that provides fallback values.
-  ///
-  /// Returned from [of] when the given [BuildContext] doesn't have an enclosing default text style.
-  const DefaultTextStyle.fallback()
-    : style = const TextStyle(),
-      textAlign = null,
-      softWrap = true,
-      overflow = TextOverflow.clip;
-
-  /// Creates a default text style that inherits from the given [BuildContext].
-  ///
-  /// The given [style] is merged with the [style] from the default text style
-  /// for the given [BuildContext] and, if non-null, the given [textAlign]
-  /// replaces the [textAlign] from the default text style for the given
-  /// [BuildContext].
-  factory DefaultTextStyle.inherit({
-    Key key,
-    @required BuildContext context,
-    TextStyle style,
-    TextAlign textAlign,
-    bool softWrap,
-    TextOverflow overflow,
-    Widget child
-  }) {
-    assert(context != null);
-    assert(child != null);
-    DefaultTextStyle parent = DefaultTextStyle.of(context);
-    return new DefaultTextStyle(
-      key: key,
-      style: parent.style.merge(style),
-      textAlign: textAlign ?? parent.textAlign,
-      softWrap: softWrap ?? parent.softWrap,
-      overflow: overflow ?? parent.overflow,
-      child: child
-    );
-  }
-
-  /// The text style to apply.
-  final TextStyle style;
-
-  /// How the text should be aligned horizontally.
-  final TextAlign textAlign;
-
-  /// Whether the text should break at soft line breaks.
-  ///
-  /// If false, the glyphs in the text will be positioned as if there was unlimited horizontal space.
-  final bool softWrap;
-
-  /// How visual overflow should be handled.
-  final TextOverflow overflow;
-
-  /// The closest instance of this class that encloses the given context.
-  ///
-  /// If no such instance exists, returns an instance created by
-  /// [DefaultTextStyle.fallback], which contains fallback values.
-  static DefaultTextStyle of(BuildContext context) {
-    return context.inheritFromWidgetOfExactType(DefaultTextStyle) ?? const DefaultTextStyle.fallback();
-  }
-
-  @override
-  bool updateShouldNotify(DefaultTextStyle old) => style != old.style;
-
-  @override
-  void debugFillDescription(List<String> description) {
-    super.debugFillDescription(description);
-    '$style'.split('\n').forEach(description.add);
-  }
-}
-
-/// A run of text with a single style.
-///
-/// The [Text] widget displays a string of text with single style. The string
-/// might break across multiple lines or might all be displayed on the same line
-/// depending on the layout constraints.
-///
-/// The [style] argument is optional. When omitted, the text will use the style
-/// from the closest enclosing [DefaultTextStyle]. If the given style's
-/// [TextStyle.inherit] property is true, the given style will be merged with
-/// the closest enclosing [DefaultTextStyle]. This merging behavior is useful,
-/// for example, to make the text bold while using the default font family and
-/// size.
-///
-/// To display text that uses multiple styles (e.g., a paragraph with some bold
-/// words), use [RichText].
-///
-/// See also:
-///
-///  * [RichText]
-///  * [DefaultTextStyle]
-class Text extends StatelessWidget {
-  /// Creates a text widget.
-  ///
-  /// If the [style] argument is null, the text will use the style from the
-  /// closest enclosing [DefaultTextStyle].
-  Text(this.data, {
-    Key key,
-    this.style,
-    this.textAlign,
-    this.softWrap,
-    this.overflow
-  }) : super(key: key) {
-    assert(data != null);
-  }
-
-  /// The text to display.
-  final String data;
-
-  /// If non-null, the style to use for this text.
-  ///
-  /// If the style's "inherit" property is true, the style will be merged with
-  /// the closest enclosing [DefaultTextStyle]. Otherwise, the style will
-  /// replace the closest enclosing [DefaultTextStyle].
-  final TextStyle style;
-
-  /// How the text should be aligned horizontally.
-  final TextAlign textAlign;
-
-  /// Whether the text should break at soft line breaks.
-  ///
-  /// If false, the glyphs in the text will be positioned as if there was unlimited horizontal space.
-  final bool softWrap;
-
-  /// How visual overflow should be handled.
-  final TextOverflow overflow;
-
-  @override
-  Widget build(BuildContext context) {
-    DefaultTextStyle defaultTextStyle = DefaultTextStyle.of(context);
-    TextStyle effectiveTextStyle = style;
-    if (style == null || style.inherit)
-      effectiveTextStyle = defaultTextStyle.style.merge(style);
-    return new RichText(
-      textAlign: textAlign ?? defaultTextStyle.textAlign,
-      softWrap: softWrap ?? defaultTextStyle.softWrap,
-      overflow: overflow ?? defaultTextStyle.overflow,
-      text: new TextSpan(
-        style: effectiveTextStyle,
-        text: data
-      )
-    );
-  }
-
-  @override
-  void debugFillDescription(List<String> description) {
-    super.debugFillDescription(description);
-    description.add('"$data"');
-    if (style != null)
-      '$style'.split('\n').forEach(description.add);
+      ..overflow = overflow
+      ..textScaleFactor = textScaleFactor;
   }
 }
 

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

@@ -10,10 +10,11 @@ import 'package:meta/meta.dart';
 import 'package:sky_services/editing/editing.mojom.dart' as mojom;
 
 import 'basic.dart';
-import 'framework.dart';
 import 'focus.dart';
-import 'scrollable.dart';
+import 'framework.dart';
+import 'media_query.dart';
 import 'scroll_behavior.dart';
+import 'scrollable.dart';
 import 'text_selection.dart';
 
 export 'package:flutter/painting.dart' show TextSelection;
@@ -166,6 +167,7 @@ class RawInputLine extends Scrollable {
     this.hideText: false,
     this.style,
     this.cursorColor,
+    this.textScaleFactor,
     this.selectionColor,
     this.selectionHandleBuilder,
     this.selectionToolbarBuilder,
@@ -193,6 +195,14 @@ class RawInputLine extends Scrollable {
   /// The text style to use for the editable text.
   final TextStyle style;
 
+  /// The number of font pixels for each logical pixel.
+  ///
+  /// For example, if the text scale factor is 1.5, text will be 50% larger than
+  /// the specified font size.
+  ///
+  /// Defaults to [MediaQuery.textScaleFactor].
+  final double textScaleFactor;
+
   /// The color to use when painting the cursor.
   final Color cursorColor;
 
@@ -438,6 +448,7 @@ class RawInputLineState extends ScrollableState<RawInputLine> {
       cursorColor: config.cursorColor,
       showCursor: _showCursor,
       selectionColor: config.selectionColor,
+      textScaleFactor: config.textScaleFactor ?? MediaQuery.of(context).textScaleFactor,
       hideText: config.hideText,
       onSelectionChanged: _handleSelectionChanged,
       paintOffset: scrollOffsetToPixelDelta(scrollOffset),
@@ -454,6 +465,7 @@ class _EditableLineWidget extends LeafRenderObjectWidget {
     this.cursorColor,
     this.showCursor,
     this.selectionColor,
+    this.textScaleFactor,
     this.hideText,
     this.onSelectionChanged,
     this.paintOffset,
@@ -465,6 +477,7 @@ class _EditableLineWidget extends LeafRenderObjectWidget {
   final Color cursorColor;
   final bool showCursor;
   final Color selectionColor;
+  final double textScaleFactor;
   final bool hideText;
   final SelectionChangedHandler onSelectionChanged;
   final Offset paintOffset;
@@ -477,6 +490,7 @@ class _EditableLineWidget extends LeafRenderObjectWidget {
       cursorColor: cursorColor,
       showCursor: showCursor,
       selectionColor: selectionColor,
+      textScaleFactor: textScaleFactor,
       selection: value.selection,
       onSelectionChanged: onSelectionChanged,
       paintOffset: paintOffset,
@@ -491,6 +505,7 @@ class _EditableLineWidget extends LeafRenderObjectWidget {
       ..cursorColor = cursorColor
       ..showCursor = showCursor
       ..selectionColor = selectionColor
+      ..textScaleFactor = textScaleFactor
       ..selection = value.selection
       ..onSelectionChanged = onSelectionChanged
       ..paintOffset = paintOffset

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

@@ -8,6 +8,7 @@ import 'package:vector_math/vector_math_64.dart';
 import 'basic.dart';
 import 'container.dart';
 import 'framework.dart';
+import 'text.dart';
 
 /// An interpolation between two [BoxConstraint]s.
 class BoxConstraintsTween extends Tween<BoxConstraints> {

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

@@ -31,12 +31,18 @@ class MediaQueryData {
   ///
   /// Consider using [MediaQueryData.fromWindow] to create data based on a
   /// [ui.Window].
-  const MediaQueryData({ this.size, this.devicePixelRatio, this.padding });
+  const MediaQueryData({
+    this.size: Size.zero,
+    this.devicePixelRatio: 1.0,
+    this.textScaleFactor: 1.0,
+    this.padding: EdgeInsets.zero
+  });
 
   /// Creates data for a media query based on the given window.
   MediaQueryData.fromWindow(ui.Window window)
     : size = window.physicalSize / window.devicePixelRatio,
       devicePixelRatio = window.devicePixelRatio,
+      textScaleFactor = 1.0, // TODO(abarth): Read this value from window.
       padding = new EdgeInsets.fromWindowPadding(window.padding, window.devicePixelRatio);
 
   /// The size of the media in logical pixel (e.g, the size of the screen).
@@ -52,6 +58,12 @@ class MediaQueryData {
   /// the Nexus 6 has a device pixel ratio of 3.5.
   final double devicePixelRatio;
 
+  /// The number of font pixels for each logical pixel.
+  ///
+  /// For example, if the text scale factor is 1.5, text will be 50% larger than
+  /// the specified font size.
+  final double textScaleFactor;
+
   /// The padding around the edges of the media (e.g., the screen).
   final EdgeInsets padding;
 
@@ -66,19 +78,16 @@ class MediaQueryData {
       return false;
     MediaQueryData typedOther = other;
     return typedOther.size == size
-        && typedOther.padding == padding
-        && typedOther.devicePixelRatio == devicePixelRatio;
+        && typedOther.devicePixelRatio == devicePixelRatio
+        && typedOther.textScaleFactor == textScaleFactor
+        && typedOther.padding == padding;
   }
 
   @override
-  int get hashCode => hashValues(
-    size.hashCode,
-    padding.hashCode,
-    devicePixelRatio.hashCode
-  );
+  int get hashCode => hashValues(size, devicePixelRatio, textScaleFactor, padding);
 
   @override
-  String toString() => '$runtimeType(size: $size, devicePixelRatio: $devicePixelRatio, padding: $padding)';
+  String toString() => '$runtimeType(size: $size, devicePixelRatio: $devicePixelRatio, textScaleFactor: $textScaleFactor, padding: $padding)';
 }
 
 /// Establishes a subtree in which media queries resolve to the given data.

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

+// Copyright 2016 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:meta/meta.dart';
+
+import 'basic.dart';
+import 'framework.dart';
+import 'media_query.dart';
+
+/// The text style to apply to descendant [Text] widgets without explicit style.
+class DefaultTextStyle extends InheritedWidget {
+  /// Creates a default text style for the given subtree.
+  ///
+  /// Consider using [DefaultTextStyle.inherit] to inherit styling information
+  /// from a the current default text style for a given [BuildContext].
+  DefaultTextStyle({
+    Key key,
+    @required this.style,
+    this.textAlign,
+    this.softWrap: true,
+    this.overflow: TextOverflow.clip,
+    Widget child
+  }) : super(key: key, child: child) {
+    assert(style != null);
+    assert(softWrap != null);
+    assert(overflow != null);
+    assert(child != null);
+  }
+
+  /// A const-constructible default text style that provides fallback values.
+  ///
+  /// Returned from [of] when the given [BuildContext] doesn't have an enclosing default text style.
+  const DefaultTextStyle.fallback()
+    : style = const TextStyle(),
+      textAlign = null,
+      softWrap = true,
+      overflow = TextOverflow.clip;
+
+  /// Creates a default text style that inherits from the given [BuildContext].
+  ///
+  /// The given [style] is merged with the [style] from the default text style
+  /// for the given [BuildContext] and, if non-null, the given [textAlign]
+  /// replaces the [textAlign] from the default text style for the given
+  /// [BuildContext].
+  factory DefaultTextStyle.inherit({
+    Key key,
+    @required BuildContext context,
+    TextStyle style,
+    TextAlign textAlign,
+    bool softWrap,
+    TextOverflow overflow,
+    Widget child
+  }) {
+    assert(context != null);
+    assert(child != null);
+    DefaultTextStyle parent = DefaultTextStyle.of(context);
+    return new DefaultTextStyle(
+      key: key,
+      style: parent.style.merge(style),
+      textAlign: textAlign ?? parent.textAlign,
+      softWrap: softWrap ?? parent.softWrap,
+      overflow: overflow ?? parent.overflow,
+      child: child
+    );
+  }
+
+  /// The text style to apply.
+  final TextStyle style;
+
+  /// How the text should be aligned horizontally.
+  final TextAlign textAlign;
+
+  /// Whether the text should break at soft line breaks.
+  ///
+  /// If false, the glyphs in the text will be positioned as if there was unlimited horizontal space.
+  final bool softWrap;
+
+  /// How visual overflow should be handled.
+  final TextOverflow overflow;
+
+  /// The closest instance of this class that encloses the given context.
+  ///
+  /// If no such instance exists, returns an instance created by
+  /// [DefaultTextStyle.fallback], which contains fallback values.
+  static DefaultTextStyle of(BuildContext context) {
+    return context.inheritFromWidgetOfExactType(DefaultTextStyle) ?? const DefaultTextStyle.fallback();
+  }
+
+  @override
+  bool updateShouldNotify(DefaultTextStyle old) => style != old.style;
+
+  @override
+  void debugFillDescription(List<String> description) {
+    super.debugFillDescription(description);
+    '$style'.split('\n').forEach(description.add);
+  }
+}
+
+/// A run of text with a single style.
+///
+/// The [Text] widget displays a string of text with single style. The string
+/// might break across multiple lines or might all be displayed on the same line
+/// depending on the layout constraints.
+///
+/// The [style] argument is optional. When omitted, the text will use the style
+/// from the closest enclosing [DefaultTextStyle]. If the given style's
+/// [TextStyle.inherit] property is true, the given style will be merged with
+/// the closest enclosing [DefaultTextStyle]. This merging behavior is useful,
+/// for example, to make the text bold while using the default font family and
+/// size.
+///
+/// To display text that uses multiple styles (e.g., a paragraph with some bold
+/// words), use [RichText].
+///
+/// See also:
+///
+///  * [RichText]
+///  * [DefaultTextStyle]
+class Text extends StatelessWidget {
+  /// Creates a text widget.
+  ///
+  /// If the [style] argument is null, the text will use the style from the
+  /// closest enclosing [DefaultTextStyle].
+  Text(this.data, {
+    Key key,
+    this.style,
+    this.textAlign,
+    this.softWrap,
+    this.overflow,
+    this.textScaleFactor
+  }) : super(key: key) {
+    assert(data != null);
+  }
+
+  /// The text to display.
+  final String data;
+
+  /// If non-null, the style to use for this text.
+  ///
+  /// If the style's "inherit" property is true, the style will be merged with
+  /// the closest enclosing [DefaultTextStyle]. Otherwise, the style will
+  /// replace the closest enclosing [DefaultTextStyle].
+  final TextStyle style;
+
+  /// How the text should be aligned horizontally.
+  final TextAlign textAlign;
+
+  /// Whether the text should break at soft line breaks.
+  ///
+  /// If false, the glyphs in the text will be positioned as if there was unlimited horizontal space.
+  final bool softWrap;
+
+  /// How visual overflow should be handled.
+  final TextOverflow overflow;
+
+  /// The number of font pixels for each logical pixel.
+  ///
+  /// For example, if the text scale factor is 1.5, text will be 50% larger than
+  /// the specified font size.
+  ///
+  /// Defaults to [MediaQuery.textScaleFactor].
+  final double textScaleFactor;
+
+  @override
+  Widget build(BuildContext context) {
+    DefaultTextStyle defaultTextStyle = DefaultTextStyle.of(context);
+    TextStyle effectiveTextStyle = style;
+    if (style == null || style.inherit)
+      effectiveTextStyle = defaultTextStyle.style.merge(style);
+    return new RichText(
+      textAlign: textAlign ?? defaultTextStyle.textAlign,
+      softWrap: softWrap ?? defaultTextStyle.softWrap,
+      overflow: overflow ?? defaultTextStyle.overflow,
+      textScaleFactor: textScaleFactor ?? MediaQuery.of(context).textScaleFactor,
+      text: new TextSpan(
+        style: effectiveTextStyle,
+        text: data
+      )
+    );
+  }
+
+  @override
+  void debugFillDescription(List<String> description) {
+    super.debugFillDescription(description);
+    description.add('"$data"');
+    if (style != null)
+      '$style'.split('\n').forEach(description.add);
+  }
+}

packages/flutter/lib/widgets.dart

@@ -56,6 +56,7 @@ export 'src/widgets/size_changed_layout_notifier.dart';
 export 'src/widgets/status_transitions.dart';
 export 'src/widgets/table.dart';
 export 'src/widgets/text_selection.dart';
+export 'src/widgets/text.dart';
 export 'src/widgets/title.dart';
 export 'src/widgets/transitions.dart';
 export 'src/widgets/unique_widget.dart';

packages/flutter/test/painting/text_style_test.dart

@@ -89,10 +89,10 @@ void main() {
     expect(s5.height, 123.0);
     expect(s5.color, isNull);
 
-    ui.TextStyle ts5 = s5.textStyle;
+    ui.TextStyle ts5 = s5.getTextStyle();
     expect(ts5, equals(new ui.TextStyle(fontWeight: FontWeight.w700, fontSize: 12.0, height: 123.0)));
     expect(ts5.toString(), 'TextStyle(color: unspecified, decoration: unspecified, decorationColor: unspecified, decorationStyle: unspecified, fontWeight: FontWeight.w700, fontStyle: unspecified, textBaseline: unspecified, fontFamily: unspecified, fontSize: 12.0, letterSpacing: unspecified, wordSpacing: unspecified, height: 123.0x)');
-    ui.TextStyle ts2 = s2.textStyle;
+    ui.TextStyle ts2 = s2.getTextStyle();
     expect(ts2, equals(new ui.TextStyle(color: const Color(0xFF00FF00), fontWeight: FontWeight.w800, fontSize: 10.0, height: 100.0)));
     expect(ts2.toString(), 'TextStyle(color: Color(0xff00ff00), decoration: unspecified, decorationColor: unspecified, decorationStyle: unspecified, fontWeight: FontWeight.w800, fontStyle: unspecified, textBaseline: unspecified, fontFamily: unspecified, fontSize: 10.0, letterSpacing: unspecified, wordSpacing: unspecified, height: 100.0x)');
 

packages/flutter/test/widget/icon_test.dart

@@ -16,7 +16,7 @@ void main() {
         child: new Icon(Icons.add)
       )
     );
-    Text text = tester.widget(find.byType(Text));
-    expect(text.style.color, equals(Colors.green[500].withOpacity(0.5)));
+    RichText text = tester.widget(find.byType(RichText));
+    expect(text.text.style.color, equals(Colors.green[500].withOpacity(0.5)));
   });
 }

packages/flutter/test/widget/reparent_state_harder_test.dart

@@ -2,9 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'package:flutter/src/widgets/basic.dart';
-import 'package:flutter/src/widgets/framework.dart';
-import 'package:flutter/src/widgets/layout_builder.dart';
+import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart' hide TypeMatcher;
 
 // This is a regression test for https://github.com/flutter/flutter/issues/5588.

packages/flutter/test/widget/text_test.dart

+// Copyright 2016 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_test/flutter_test.dart';
+import 'package:flutter/widgets.dart';
+
+void main() {
+  testWidgets('Text respects media query', (WidgetTester tester) async {
+    await tester.pumpWidget(new MediaQuery(
+      data: new MediaQueryData(textScaleFactor: 1.5),
+      child: new Center(
+        child: new Text('Hello')
+      )
+    ));
+
+    RichText text = tester.firstWidget(find.byType(RichText));
+    expect(text, isNotNull);
+    expect(text.textScaleFactor, 1.5);
+
+    await tester.pumpWidget(new Center(
+      child: new Text('Hello')
+    ));
+
+    text = tester.firstWidget(find.byType(RichText));
+    expect(text, isNotNull);
+    expect(text.textScaleFactor, 1.0);
+
+    await tester.pumpWidget(new Center(
+      child: new Text('Hello', textScaleFactor: 3.0)
+    ));
+
+    text = tester.firstWidget(find.byType(RichText));
+    expect(text, isNotNull);
+    expect(text.textScaleFactor, 3.0);
+  });
+}