Move TextAlign out of TextStyle (#3789)

TextAlign applies to a whole paragraph instead of applying to an individual
text span. This patch moves the property out of TextStyle and into a separate
property on Text and RichText.

dev/manual_tests/card_collection.dart

@@ -32,13 +32,12 @@ class CardCollectionState extends State<CardCollection> {
   static const double kCardMargins = 8.0;
   static const double kFixedCardHeight = 100.0;
 
-  final TextStyle backgroundTextStyle =
-    Typography.white.title.copyWith(textAlign: TextAlign.center);
+  final TextStyle backgroundTextStyle = Typography.white.title;
 
   Map<int, Color> _primaryColor = Colors.deepPurple;
   List<CardModel> _cardModels;
   DismissDirection _dismissDirection = DismissDirection.horizontal;
-  TextStyle _textStyle = new TextStyle(textAlign: TextAlign.center);
+  TextAlign _textAlign = TextAlign.center;
   bool _editable = false;
   bool _snapToCenter = false;
   bool _fixedSizeCards = false;
@@ -143,9 +142,9 @@ class CardCollectionState extends State<CardCollection> {
           buildDrawerDirectionRadioItem("Dismiss left", DismissDirection.endToStart, _dismissDirection, _changeDismissDirection, icon: Icons.arrow_back),
           buildDrawerDirectionRadioItem("Dismiss right", DismissDirection.startToEnd, _dismissDirection, _changeDismissDirection, icon: Icons.arrow_forward),
           new Divider(),
-          buildFontRadioItem("Left-align text", new TextStyle(textAlign: TextAlign.left), _textStyle, _changeTextStyle, icon: Icons.format_align_left, enabled: !_editable),
-          buildFontRadioItem("Center-align text", new TextStyle(textAlign: TextAlign.center), _textStyle, _changeTextStyle, icon: Icons.format_align_center, enabled: !_editable),
-          buildFontRadioItem("Right-align text", new TextStyle(textAlign: TextAlign.right), _textStyle, _changeTextStyle, icon: Icons.format_align_right, enabled: !_editable),
+          buildFontRadioItem("Left-align text", TextAlign.left, _textAlign, _changeTextAlign, icon: Icons.format_align_left, enabled: !_editable),
+          buildFontRadioItem("Center-align text", TextAlign.center, _textAlign, _changeTextAlign, icon: Icons.format_align_center, enabled: !_editable),
+          buildFontRadioItem("Right-align text", TextAlign.right, _textAlign, _changeTextAlign, icon: Icons.format_align_right, enabled: !_editable),
           new Divider(),
           new DrawerItem(
             icon: Icons.dvr,
@@ -205,9 +204,9 @@ class CardCollectionState extends State<CardCollection> {
     });
   }
 
-  void _changeTextStyle(TextStyle newTextStyle) {
+  void _changeTextAlign(TextAlign newTextAlign) {
     setState(() {
-      _textStyle = newTextStyle;
+      _textAlign = newTextAlign;
     });
   }
 
@@ -260,14 +259,14 @@ class CardCollectionState extends State<CardCollection> {
     );
   }
 
-  Widget buildFontRadioItem(String label, TextStyle itemValue, TextStyle currentValue, ValueChanged<TextStyle> onChanged, { IconData icon, bool enabled: true }) {
+  Widget buildFontRadioItem(String label, TextAlign itemValue, TextAlign currentValue, ValueChanged<TextAlign> onChanged, { IconData icon, bool enabled: true }) {
     return new DrawerItem(
       icon: icon,
       onPressed: enabled ? () { onChanged(itemValue); } : null,
       child: new Row(
         children: <Widget>[
           new Flexible(child: new Text(label)),
-          new Radio<TextStyle>(
+          new Radio<TextAlign>(
             value: itemValue,
             groupValue: currentValue,
             onChanged: enabled ? onChanged : null
@@ -319,16 +318,17 @@ class CardCollectionState extends State<CardCollection> {
                 }
               )
             )
-          : new DefaultTextStyle(
-              style: DefaultTextStyle.of(context).merge(cardLabelStyle).merge(_textStyle).copyWith(
+          : new DefaultTextStyle.inherit(
+              context: context,
+              style: cardLabelStyle.copyWith(
                 fontSize: _varyFontSizes ? 5.0 + index : null
               ),
               child: new Column(
-                children: <Widget>[
-                  new Text(cardModel.inputValue.text)
-                ],
                 crossAxisAlignment: CrossAxisAlignment.stretch,
-                mainAxisAlignment: MainAxisAlignment.center
+                mainAxisAlignment: MainAxisAlignment.center,
+                children: <Widget>[
+                  new Text(cardModel.inputValue.text, textAlign: _textAlign)
+                ]
               )
             )
         )
@@ -379,7 +379,12 @@ class CardCollectionState extends State<CardCollection> {
             child: new Row(
               children: <Widget>[
                 leftArrowIcon,
-                new Flexible(child: new Text(backgroundMessage, style: backgroundTextStyle)),
+                new Flexible(
+                  child: new Text(backgroundMessage,
+                    style: backgroundTextStyle,
+                    textAlign: TextAlign.center
+                  )
+                ),
                 rightArrowIcon
               ]
             )

dev/manual_tests/drag_and_drop.dart

@@ -98,7 +98,8 @@ class ExampleDragSource extends StatelessWidget {
       size *= kHeavyMultiplier;
 
     Widget contents = new DefaultTextStyle(
-      style: Theme.of(context).textTheme.body1.copyWith(textAlign: TextAlign.center),
+      style: Theme.of(context).textTheme.body1,
+      textAlign: TextAlign.center,
       child: new Dot(
         color: color,
         size: size,
@@ -185,10 +186,8 @@ class MovableBall extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     Widget ball = new DefaultTextStyle(
-      style: Theme.of(context).textTheme.body1.copyWith(
-        textAlign: TextAlign.center,
-        color: Colors.white
-      ),
+      style: Typography.white.body1,
+      textAlign: TextAlign.center,
       child: new Dot(
         key: kBallKey,
         color: Colors.blue[700],

examples/material_gallery/lib/demo/modal_bottom_sheet_demo.dart

@@ -4,15 +4,14 @@
 
 import 'package:flutter/material.dart';
 
+final TextStyle _kTextStyle = new TextStyle(
+  color: Colors.indigo[400],
+  fontSize: 24.0
+);
+
 class ModalBottomSheetDemo extends StatelessWidget {
   static const String routeName = '/modal-bottom-sheet';
 
-  final TextStyle textStyle = new TextStyle(
-    color: Colors.indigo[400],
-    fontSize: 24.0,
-    textAlign: TextAlign.center
-  );
-
   @override
   Widget build(BuildContext context) {
     return new Scaffold(
@@ -25,7 +24,10 @@ class ModalBottomSheetDemo extends StatelessWidget {
               return new Container(
                 child: new Padding(
                   padding: const EdgeInsets.all(32.0),
-                  child: new Text('This is the modal bottom sheet. Click anywhere to dismiss.', style: textStyle)
+                  child: new Text('This is the modal bottom sheet. Click anywhere to dismiss.',
+                    style: _kTextStyle,
+                    textAlign: TextAlign.center
+                  )
                 )
               );
             });

examples/material_gallery/lib/demo/persistent_bottom_sheet_demo.dart

@@ -4,6 +4,11 @@
 
 import 'package:flutter/material.dart';
 
+final TextStyle _kTextStyle = new TextStyle(
+  color: Colors.indigo[400],
+  fontSize: 24.0
+);
+
 class PersistentBottomSheetDemo extends StatefulWidget {
   static const String routeName = '/persistent-bottom-sheet';
 
@@ -14,12 +19,6 @@ class PersistentBottomSheetDemo extends StatefulWidget {
 class _PersistentBottomSheetDemoState extends State<PersistentBottomSheetDemo> {
   final GlobalKey<ScaffoldState> _scaffoldKey = new GlobalKey<ScaffoldState>();
 
-  final TextStyle textStyle = new TextStyle(
-    color: Colors.indigo[400],
-    fontSize: 24.0,
-    textAlign: TextAlign.center
-  );
-
   VoidCallback _showBottomSheetCallback;
 
   @override
@@ -40,7 +39,10 @@ class _PersistentBottomSheetDemoState extends State<PersistentBottomSheetDemo> {
         ),
         child: new Padding(
           padding: const EdgeInsets.all(32.0),
-          child: new Text('This is a Material persistent bottom sheet. Drag downwards to dismiss it.', style: textStyle)
+          child: new Text('This is a Material persistent bottom sheet. Drag downwards to dismiss it.',
+            style: _kTextStyle,
+            textAlign: TextAlign.center
+          )
         )
       );
     })

examples/material_gallery/lib/demo/tabs_fab_demo.dart

@@ -72,18 +72,18 @@ class _TabsFabDemoState extends State<TabsFabDemo> {
   Widget buildTabView(_Page page) {
     return new Builder(
       builder: (BuildContext context) {
-        final TextStyle textStyle = new TextStyle(
-          color: page.labelColor,
-          fontSize: 32.0,
-          textAlign: TextAlign.center
-        );
-
         return new Container(
           key: new ValueKey<String>(page.label),
           padding: const EdgeInsets.fromLTRB(48.0, 48.0, 48.0, 96.0),
           child: new Card(
             child: new Center(
-              child: new Text(page.label, style: textStyle)
+              child: new Text(page.label,
+                style: new TextStyle(
+                  color: page.labelColor,
+                  fontSize: 32.0
+                ),
+                textAlign: TextAlign.center
+              )
             )
           )
         );

examples/stocks/lib/stock_row.dart

@@ -100,18 +100,18 @@ class StockRow extends StatelessWidget {
                   new Flexible(
                     child: new Text(
                       lastSale,
-                      style: const TextStyle(textAlign: TextAlign.right)
+                      textAlign: TextAlign.right
                     )
                   ),
                   new Flexible(
                     child: new Text(
                       changeInPrice,
-                      style: const TextStyle(textAlign: TextAlign.right)
+                      textAlign: TextAlign.right
                     )
                   ),
                 ],
                 crossAxisAlignment: CrossAxisAlignment.baseline,
-                textBaseline: DefaultTextStyle.of(context).textBaseline
+                textBaseline: DefaultTextStyle.of(context).style.textBaseline
               )
             ),
           ]

examples/stocks/lib/stock_symbol_viewer.dart

@@ -52,7 +52,7 @@ class StockSymbolView extends StatelessWidget {
           ),
           new RichText(
             text: new TextSpan(
-              style: DefaultTextStyle.of(context).merge(new TextStyle(fontSize: 8.0)),
+              style: DefaultTextStyle.of(context).style.merge(new TextStyle(fontSize: 8.0)),
               text: 'Prices may be delayed by ',
               children: <TextSpan>[
                 new TextSpan(text: 'several', style: new TextStyle(fontStyle: FontStyle.italic)),

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

@@ -16,7 +16,6 @@ const TextStyle _errorTextStyle = const TextStyle(
   fontFamily: 'monospace',
   fontSize: 48.0,
   fontWeight: FontWeight.w900,
-  textAlign: TextAlign.right,
   decoration: TextDecoration.underline,
   decorationColor: const Color(0xFFFFFF00),
   decorationStyle: TextDecorationStyle.double

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

@@ -274,7 +274,7 @@ List<TextPainter> _initPainters(List<String> labels) {
   for (int i = 0; i < painters.length; ++i) {
     String label = labels[i];
     painters[i] = new TextPainter(
-      new TextSpan(style: style, text: label)
+      text: new TextSpan(style: style, text: label)
     )..layout();
   }
   return painters;

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

@@ -30,8 +30,11 @@ class TextPainter {
   ///
   /// The text argument is optional but [text] must be non-null before calling
   /// [layout].
-  TextPainter([ TextSpan text ]) {
-    this.text = text;
+  TextPainter({
+    TextSpan text,
+    TextAlign textAlign
+  }) : _text = text, _textAlign = textAlign {
+    assert(text == null || text.debugAssertValid());
   }
 
   ui.Paragraph _paragraph;
@@ -45,15 +48,19 @@ class TextPainter {
     if (_text == value)
       return;
     _text = value;
-    if (_text != null) {
-      ui.ParagraphBuilder builder = new ui.ParagraphBuilder();
-      _text.build(builder);
-      _paragraph = builder.build(_text.style?.paragraphStyle ?? new ui.ParagraphStyle());
-      _needsLayout = true;
-    } else {
-      _paragraph = null;
-      _needsLayout = false;
-    }
+    _paragraph = null;
+    _needsLayout = true;
+  }
+
+  /// How the text should be aligned horizontally.
+  TextAlign get textAlign => _textAlign;
+  TextAlign _textAlign;
+  void set textAlign(TextAlign value) {
+    if (_textAlign == value)
+      return;
+    _textAlign = value;
+    _paragraph = null;
+    _needsLayout = true;
   }
 
   // Unfortunately, using full precision floating point here causes bad layouts
@@ -129,9 +136,17 @@ class TextPainter {
   /// width as possible while still being greater than or equal to minWidth and
   /// less than or equal to maxWidth.
   void layout({ double minWidth: 0.0, double maxWidth: double.INFINITY }) {
+    assert(_text != null);
     if (!_needsLayout && minWidth == _lastMinWidth && maxWidth == _lastMaxWidth)
       return;
     _needsLayout = false;
+    if (_paragraph == null) {
+      ui.ParagraphBuilder builder = new ui.ParagraphBuilder();
+      _text.build(builder);
+      ui.ParagraphStyle paragraphStyle = _text.style?.getParagraphStyle(textAlign: textAlign);
+      paragraphStyle ??= new ui.ParagraphStyle();
+      _paragraph = builder.build(paragraphStyle);
+    }
     _lastMinWidth = minWidth;
     _lastMaxWidth = maxWidth;
     _paragraph.layout(new ui.ParagraphConstraints(width: maxWidth));

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

@@ -18,7 +18,6 @@ class TextStyle {
     this.fontStyle,
     this.letterSpacing,
     this.wordSpacing,
-    this.textAlign,
     this.textBaseline,
     this.height,
     this.decoration,
@@ -50,10 +49,6 @@ class TextStyle {
   /// The amount of space (in logical pixels) to add at each sequence of white-space (i.e. between each word).
   final double wordSpacing;
 
-  /// How the text should be aligned (applies only to the outermost
-  /// StyledTextSpan, which establishes the container for the text).
-  final TextAlign textAlign;
-
   /// The baseline to use for aligning the text.
   final TextBaseline textBaseline;
 
@@ -82,7 +77,6 @@ class TextStyle {
     FontStyle fontStyle,
     double letterSpacing,
     double wordSpacing,
-    TextAlign textAlign,
     TextBaseline textBaseline,
     double height,
     TextDecoration decoration,
@@ -98,7 +92,6 @@ class TextStyle {
       fontStyle: fontStyle != null ? fontStyle : this.fontStyle,
       letterSpacing: letterSpacing != null ? letterSpacing : this.letterSpacing,
       wordSpacing: wordSpacing != null ? wordSpacing : this.wordSpacing,
-      textAlign: textAlign != null ? textAlign : this.textAlign,
       textBaseline: textBaseline != null ? textBaseline : this.textBaseline,
       height: height != null ? height : this.height,
       decoration: decoration != null ? decoration : this.decoration,
@@ -122,7 +115,6 @@ class TextStyle {
       fontStyle: other.fontStyle,
       letterSpacing: other.letterSpacing,
       wordSpacing: other.wordSpacing,
-      textAlign: other.textAlign,
       textBaseline: other.textBaseline,
       height: other.height,
       decoration: other.decoration,
@@ -146,7 +138,6 @@ class TextStyle {
       fontStyle: t < 0.5 ? begin.fontStyle : end.fontStyle,
       letterSpacing: ui.lerpDouble(begin.letterSpacing ?? end.letterSpacing, end.letterSpacing ?? begin.letterSpacing, t),
       wordSpacing: ui.lerpDouble(begin.wordSpacing ?? end.wordSpacing, end.wordSpacing ?? begin.wordSpacing, t),
-      textAlign: t < 0.5 ? begin.textAlign : end.textAlign,
       textBaseline: t < 0.5 ? begin.textBaseline : end.textBaseline,
       height: ui.lerpDouble(begin.height ?? end.height, end.height ?? begin.height, t),
       decoration: t < 0.5 ? begin.decoration : end.decoration,
@@ -173,7 +164,7 @@ class TextStyle {
   }
 
   /// The style information for paragraphs, encoded for use by `dart:ui`.
-  ui.ParagraphStyle get paragraphStyle {
+  ui.ParagraphStyle getParagraphStyle({ TextAlign textAlign }) {
     return new ui.ParagraphStyle(
       textAlign: textAlign,
       textBaseline: textBaseline,
@@ -200,7 +191,6 @@ class TextStyle {
            fontStyle == typedOther.fontStyle &&
            letterSpacing == typedOther.letterSpacing &&
            wordSpacing == typedOther.wordSpacing &&
-           textAlign == typedOther.textAlign &&
            textBaseline == typedOther.textBaseline &&
            height == typedOther.height &&
            decoration == typedOther.decoration &&
@@ -219,7 +209,6 @@ class TextStyle {
       fontStyle,
       letterSpacing,
       wordSpacing,
-      textAlign,
       textBaseline,
       height,
       decoration,
@@ -283,19 +272,6 @@ class TextStyle {
       result.add('${prefix}letterSpacing: ${letterSpacing}x');
     if (wordSpacing != null)
       result.add('${prefix}wordSpacing: ${wordSpacing}x');
-    if (textAlign != null) {
-      switch (textAlign) {
-        case TextAlign.left:
-          result.add('${prefix}align: left');
-          break;
-        case TextAlign.right:
-          result.add('${prefix}align: right');
-          break;
-        case TextAlign.center:
-          result.add('${prefix}align: center');
-          break;
-      }
-    }
     if (textBaseline != null) {
       switch (textBaseline) {
         case TextBaseline.alphabetic:

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

@@ -287,8 +287,9 @@ class RenderChildView extends RenderBox {
       _child._setChildProperties(_physicalWidth, _physicalHeight, scale);
       assert(() {
         if (_view == null) {
-          _debugErrorMessage ??= new TextPainter()
-            ..text = new TextSpan(text: 'Child view are supported only when running in Mojo shell.');
+          _debugErrorMessage ??= new TextPainter(
+            text: new TextSpan(text: 'Child views are supported only when running in Mojo shell.')
+          );
           _debugErrorMessage.layout(minWidth: size.width, maxWidth: size.width);
         }
         return true;

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

@@ -42,7 +42,7 @@ class RenderEditableLine extends RenderBox {
     this.onSelectionChanged,
     Offset paintOffset: Offset.zero,
     this.onPaintOffsetUpdateNeeded
-  }) : _textPainter = new TextPainter(text),
+  }) : _textPainter = new TextPainter(text: text),
        _cursorColor = cursorColor,
        _showCursor = showCursor,
        _selection = selection,

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

@@ -11,9 +11,9 @@ import 'semantics.dart';
 /// A render object that displays a paragraph of text
 class RenderParagraph extends RenderBox {
 
-  RenderParagraph(
-    TextSpan text
-  ) : _textPainter = new TextPainter(text) {
+  RenderParagraph(TextSpan text, {
+    TextAlign textAlign
+  }) : _textPainter = new TextPainter(text: text, textAlign: textAlign) {
     assert(text != null);
     assert(text.debugAssertValid());
   }
@@ -23,13 +23,22 @@ class RenderParagraph extends RenderBox {
   /// The text to display
   TextSpan get text => _textPainter.text;
   void set text(TextSpan value) {
-    assert(value.debugAssertValid());
+    assert(value != null);
     if (_textPainter.text == value)
       return;
     _textPainter.text = value;
     markNeedsLayout();
   }
 
+  /// How the text should be aligned horizontally.
+  TextAlign get textAlign => _textPainter.textAlign;
+  void set textAlign(TextAlign value) {
+    if (_textPainter.textAlign == value)
+      return;
+    _textPainter.textAlign = value;
+    markNeedsPaint();
+  }
+
   void _layoutText(BoxConstraints constraints) {
     assert(constraints != null);
     assert(constraints.debugAssertIsValid());
@@ -101,6 +110,9 @@ class RenderParagraph extends RenderBox {
     //
     // TODO(abarth): Make computing the min/max intrinsic width/height
     // a non-destructive operation.
+    //
+    // If you remove this call, make sure that changing the textAlign still
+    // works properly.
     _layoutText(constraints);
     _textPainter.paint(context.canvas, offset);
   }

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

@@ -15,7 +15,6 @@ const TextStyle _kTextStyles = const TextStyle(
   color: const Color(0xFFFFFFFF),
   fontSize: _kHeight * 0.85,
   fontWeight: FontWeight.w900,
-  textAlign: TextAlign.center,
   height: 1.0
 );
 
@@ -64,9 +63,10 @@ class BannerPainter extends CustomPainter {
       ..drawRect(_kRect, paintBanner);
 
     final double width = _kOffset * 2.0;
-    final TextPainter textPainter = new TextPainter()
-      ..text = new TextSpan(style: _kTextStyles, text: message)
-      ..layout(minWidth: width, maxWidth: width);
+    final TextPainter textPainter = new TextPainter(
+      text: new TextSpan(style: _kTextStyles, text: message),
+      textAlign: TextAlign.center
+    )..layout(minWidth: width, maxWidth: width);
 
     textPainter.paint(canvas, _kRect.topLeft.toOffset() + new Offset(0.0, (_kRect.height - textPainter.height) / 2.0));
   }

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

@@ -1904,40 +1904,84 @@ class RichText extends LeafRenderObjectWidget {
   /// Creates a paragraph of rich text.
   ///
   /// The [text] argument is required to be non-null.
-  RichText({ Key key, this.text }) : super(key: key) {
+  RichText({ Key key, this.text, this.textAlign }) : super(key: key) {
     assert(text != null);
   }
 
   /// The text to display in this widget.
   final TextSpan text;
 
+  /// How the text should be aligned horizontally.
+  final TextAlign textAlign;
+
   @override
-  RenderParagraph createRenderObject(BuildContext context) => new RenderParagraph(text);
+  RenderParagraph createRenderObject(BuildContext context) {
+    return new RenderParagraph(text, textAlign: textAlign);
+  }
 
   @override
   void updateRenderObject(BuildContext context, RenderParagraph renderObject) {
-    renderObject.text = text;
+    renderObject
+      ..text = text
+      ..textAlign = textAlign;
   }
 }
 
 /// 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,
     this.style,
+    this.textAlign,
     Widget child
   }) : super(key: key, child: child) {
     assert(style != 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;
+
+  /// 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,
+    BuildContext context,
+    TextStyle style,
+    TextAlign textAlign,
+    Widget child
+  }) {
+    DefaultTextStyle parent = DefaultTextStyle.of(context);
+    return new DefaultTextStyle(
+      key: key,
+      style: parent.style.merge(style),
+      textAlign: textAlign ?? parent.textAlign,
+      child: child
+    );
+  }
+
   /// The text style to apply.
   final TextStyle style;
 
-  /// The style from the closest instance of this class that encloses the given context.
-  static TextStyle of(BuildContext context) {
-    DefaultTextStyle result = context.inheritFromWidgetOfExactType(DefaultTextStyle);
-    return result?.style ?? const TextStyle();
+  /// How the text should be aligned horizontally.
+  final TextAlign textAlign;
+
+  /// 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
@@ -1975,7 +2019,7 @@ class Text extends StatelessWidget {
   ///
   /// If the [style] argument is null, the text will use the style from the
   /// closest enclosing [DefaultTextStyle].
-  Text(this.data, { Key key, this.style }) : super(key: key) {
+  Text(this.data, { Key key, this.style, this.textAlign }) : super(key: key) {
     assert(data != null);
   }
 
@@ -1989,18 +2033,26 @@ class Text extends StatelessWidget {
   /// replace the closest enclosing [DefaultTextStyle].
   final TextStyle style;
 
-  TextStyle _getEffectiveStyle(BuildContext context) {
-    if (style == null || style.inherit)
-      return DefaultTextStyle.of(context).merge(style);
-    else
-      return style;
-  }
+  /// How the text should be aligned horizontally.
+  final TextAlign textAlign;
 
   @override
   Widget build(BuildContext context) {
+    DefaultTextStyle defaultTextStyle;
+    TextStyle effectiveTextStyle = style;
+    if (style == null || style.inherit) {
+      defaultTextStyle ??= DefaultTextStyle.of(context);
+      effectiveTextStyle = defaultTextStyle.style.merge(style);
+    }
+    TextAlign effectiveTextAlign = textAlign;
+    if (effectiveTextAlign == null) {
+      defaultTextStyle ??= DefaultTextStyle.of(context);
+      effectiveTextAlign = defaultTextStyle.textAlign;
+    }
     return new RichText(
+      textAlign: effectiveTextAlign,
       text: new TextSpan(
-        style: _getEffectiveStyle(context),
+        style: effectiveTextStyle,
         text: data
       )
     );

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

@@ -146,8 +146,7 @@ class _SemanticsDebuggerEntry {
   static const TextStyle textStyles = const TextStyle(
     color: const Color(0xFF000000),
     fontSize: 10.0,
-    height: 0.8,
-    textAlign: TextAlign.center
+    height: 0.8
   );
 
   TextPainter textPainter;
@@ -185,6 +184,7 @@ class _SemanticsDebuggerEntry {
       textPainter ??= new TextPainter();
       textPainter
         ..text = new TextSpan(style: textStyles, text: message)
+        ..textAlign = TextAlign.center
         ..layout(maxWidth: rect.width);
     } else {
       textPainter = null;

packages/flutter_markdown/lib/src/markdown_raw.dart

@@ -387,7 +387,7 @@ class _Block {
         if (listIndents.last == 'ul') {
           bullet = new Text(
             '•',
-            style: new TextStyle(textAlign: TextAlign.center)
+            textAlign: TextAlign.center
           );
         }
         else {
@@ -395,7 +395,7 @@ class _Block {
             padding: new EdgeInsets.only(right: 5.0),
             child: new Text(
               "${blockPosition + 1}.",
-              style: new TextStyle(textAlign: TextAlign.right)
+              textAlign: TextAlign.right
             )
           );
         }

packages/flutter_sprites/lib/src/label.dart

@@ -3,47 +3,46 @@ part of flutter_sprites;
 /// Labels are used to display a string of text in a the node tree. To align
 /// the label, the textAlign property of the [TextStyle] can be set.
 class Label extends Node {
-  /// Creates a new Label with the provided [_text] and [_textStyle].
-  Label(this._text, [this._textStyle]) {
-    if (_textStyle == null) {
-      _textStyle = new TextStyle();
-    }
-  }
-
-  String _text;
+  /// Creates a new Label with the provided [text] and [textStyle].
+  Label(this._text, {
+    TextStyle textStyle,
+    TextAlign textAlign
+  }) : _textStyle = textStyle ?? const TextStyle(),
+       textAlign = textAlign ?? TextAlign.left;
 
   /// The text being drawn by the label.
   String get text => _text;
-
+  String _text;
   void set text(String text) {
     _text = text;
     _painter = null;
   }
 
-  TextStyle _textStyle;
-
   /// The style to draw the text in.
   TextStyle get textStyle => _textStyle;
-
+  TextStyle _textStyle;
   void set textStyle(TextStyle textStyle) {
     _textStyle = textStyle;
     _painter = null;
   }
 
+  /// How the text should be aligned horizontally.
+  TextAlign textAlign;
+
   TextPainter _painter;
   double _width;
 
   @override
   void paint(Canvas canvas) {
     if (_painter == null) {
-      _painter = new TextPainter(new TextSpan(style: _textStyle, text: _text))
+      _painter = new TextPainter(text: new TextSpan(style: _textStyle, text: _text))
         ..layout();
     }
 
     Offset offset = Offset.zero;
-    if (_textStyle.textAlign == TextAlign.center) {
+    if (textAlign == TextAlign.center) {
       offset = new Offset(-_width / 2.0, 0.0);
-    } else if (_textStyle.textAlign == TextAlign.right) {
+    } else if (textAlign == TextAlign.right) {
       offset = new Offset(-_width, 0.0);
     }
 

packages/playfair/lib/src/base.dart

@@ -174,7 +174,7 @@ class ChartPainter {
         style: _textTheme.body1,
         text: '${gridline.value}'
       );
-      gridline.labelPainter = new TextPainter(text)
+      gridline.labelPainter = new TextPainter(text: text)
         ..layout(maxWidth: _rect.width);
       _horizontalGridlines.add(gridline);
       yScaleWidth = math.max(yScaleWidth, gridline.labelPainter.maxIntrinsicWidth);
@@ -220,7 +220,7 @@ class ChartPainter {
           style: _textTheme.body1,
           text: '${data.indicatorText}'
         );
-        _indicator.labelPainter = new TextPainter(text)
+        _indicator.labelPainter = new TextPainter(text: text)
           ..layout(maxWidth: markerRect.width);
         _indicator.labelPosition = new Point(
           ((_indicator.start.x + _indicator.end.x) / 2.0) - _indicator.labelPainter.maxIntrinsicWidth / 2.0,