Text inline widgets, TextSpan rework (#33794)

* Merge in changes for inline widgets

* Make analyzer happy, fix tests

* Fix analyzer

* Add missing doc

* Docs on RichText

* Fix analyzer some more

* Remove whitespace at end of line

* Update goldens

* Text fixes

* Analyzer

bin/internal/goldens.version

-041efaf483a1cd011f4b4f6dcd04e0d5cad9436e
+eb9c1d66709a1f8a0291076865fe387ceed96dca

dev/benchmarks/complex_layout/lib/main.dart

@@ -438,8 +438,8 @@ class ItemImageBox extends StatelessWidget {
                       borderRadius: BorderRadius.circular(2.0),
                     ),
                     padding: const EdgeInsets.all(4.0),
-                    child: const RichText(
-                      text: TextSpan(
+                    child: RichText(
+                      text: const TextSpan(
                         style: TextStyle(color: Colors.white),
                         children: <TextSpan>[
                           TextSpan(

dev/manual_tests/lib/text.dart

@@ -145,7 +145,7 @@ class _FuzzerState extends State<Fuzzer> with SingleTickerProviderStateMixin {
     return TextSpan(
       text: _fiddleWithText(node.text),
       style: _fiddleWithStyle(node.style),
-      children: _fiddleWithChildren(node.children?.map((TextSpan child) => _fiddleWith(child))?.toList() ?? <TextSpan>[]),
+      children: _fiddleWithChildren(node.children?.map((InlineSpan child) => _fiddleWith(child))?.toList() ?? <InlineSpan>[]),
     );
   }
 

packages/flutter/lib/painting.dart

@@ -17,7 +17,7 @@
 ///    painting boxes.
 library painting;
 
-export 'dart:ui' show Shadow;
+export 'dart:ui' show Shadow, PlaceholderAlignment;
 
 export 'src/painting/alignment.dart';
 export 'src/painting/basic_types.dart';
@@ -46,9 +46,11 @@ export 'src/painting/image_decoder.dart';
 export 'src/painting/image_provider.dart';
 export 'src/painting/image_resolution.dart';
 export 'src/painting/image_stream.dart';
+export 'src/painting/inline_span.dart';
 export 'src/painting/matrix_utils.dart';
 export 'src/painting/notched_shapes.dart';
 export 'src/painting/paint_utilities.dart';
+export 'src/painting/placeholder_span.dart';
 export 'src/painting/rounded_rectangle_border.dart';
 export 'src/painting/shader_warm_up.dart';
 export 'src/painting/shape_decoration.dart';

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

@@ -993,6 +993,7 @@ class _DialPainter extends CustomPainter {
         final double width = labelPainter.width * _semanticNodeSizeScale;
         final double height = labelPainter.height * _semanticNodeSizeScale;
         final Offset nodeOffset = getOffsetForTheta(labelTheta, ring) + Offset(-width / 2.0, -height / 2.0);
+        final TextSpan textSpan = labelPainter.text;
         final CustomPainterSemantics node = CustomPainterSemantics(
           rect: Rect.fromLTRB(
             nodeOffset.dx - 24.0 + width / 2,
@@ -1003,7 +1004,7 @@ class _DialPainter extends CustomPainter {
           properties: SemanticsProperties(
             sortKey: OrdinalSortKey(i.toDouble() + ordinalOffset),
             selected: label.value == selectedValue,
-            value: labelPainter.text.text,
+            value: textSpan?.text,
             textDirection: textDirection,
             onTap: label.onTap,
           ),

packages/flutter/lib/src/painting/inline_span.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 'dart:ui' as ui show ParagraphBuilder;
+
+import 'package:flutter/foundation.dart';
+
+import 'basic_types.dart';
+import 'text_painter.dart';
+import 'text_style.dart';
+
+/// Mutable wrapper of an integer that can be passed by reference to track a
+/// value across a recursive stack.
+class Accumulator {
+  /// [Accumulator] may be initialized with a specified value, otherwise, it will
+  /// initialize to zero.
+  Accumulator([this._value = 0]);
+
+  /// The integer stored in this [Accumulator].
+  int get value => _value;
+  int _value;
+
+  /// Increases the [value] by the `addend`.
+  void increment(int addend) {
+    assert(addend >= 0);
+    _value += addend;
+  }
+}
+/// Called on each span as [InlineSpan.visitChildren] walks the [InlineSpan] tree.
+///
+/// Returns true when the walk should continue, and false to stop visiting further
+/// [InlineSpan]s.
+typedef InlineSpanVisitor = bool Function(InlineSpan span);
+
+/// An immutable span of inline content which forms part of a paragraph.
+///
+///  * The subclass [TextSpan] specifies text and may contain child [InlineSpan]s.
+///  * The subclass [PlaceholderSpan] represents a placeholder that may be
+///    filled with non-text content. [PlaceholderSpan] itself defines a
+///    [ui.PlaceholderAlignemnt] and a [TextBaseline]. To be useful,
+///    [PlaceholderSpan] must be extended to define content. An instance of
+///    this is the [WidgetSpan] class in the widgets library.
+///  * The subclass [WidgetSpan] specifies embedded inline widgets.
+///
+/// {@tool sample}
+///
+/// This example shows a tree of [InlineSpan]s that make a query asking for a
+/// name with a [TextField] embedded inline.
+///
+/// ```dart
+/// Text.rich(
+///   TextSpan(
+///     text: 'My name is ',
+///     style: TextStyle(color: Colors.black),
+///     children: <InlineSpan>[
+///       WidgetSpan(
+///         alignment: PlaceholderAlignment.baseline,
+///         baseline: TextBaseline.alphabetic,
+///         child: ConstrainedBox(
+///           constraints: BoxConstraints(maxWidth: 100),
+///           child: TextField(),
+///         )
+///       ),
+///       TextSpan(
+///         text: '.',
+///       ),
+///     ],
+///   ),
+/// )
+/// ```
+/// {@end-tool}
+///
+/// See also:
+///
+///  * [Text], a widget for showing uniformly-styled text.
+///  * [RichText], a widget for finer control of text rendering.
+///  * [TextPainter], a class for painting [InlineSpan] objects on a [Canvas].
+@immutable
+abstract class InlineSpan extends DiagnosticableTree {
+  /// Creates an [InlineSpan] with the given values.
+  const InlineSpan({
+    this.style,
+  });
+
+  /// The [TextStyle] to apply to this span.
+  ///
+  /// The [style] is also applied to any child spans when this is an instance
+  /// of [TextSpan].
+  final TextStyle style;
+
+  /// Apply the properties of this object to the given [ParagraphBuilder], from
+  /// which a [Paragraph] can be obtained.
+  ///
+  /// The `textScaleFactor` parameter specifies a scale that the text and
+  /// placeholders will be scaled by. The scaling is performed before layout,
+  /// so the text will be laid out with the scaled glyphs and placeholders.
+  ///
+  /// The `dimensions` parameter specifies the sizes of the placeholders.
+  /// Each [PlaceholderSpan] must be paired with a [PlaceholderDimensions]
+  /// in the same order as defined in the [InlineSpan] tree.
+  ///
+  /// [Paragraph] objects can be drawn on [Canvas] objects.
+  void build(ui.ParagraphBuilder builder, { double textScaleFactor = 1.0, List<PlaceholderDimensions> dimensions });
+
+  /// Walks this [InlineSpan] and any descendants in pre-order and calls `visitor`
+  /// for each span that has content.
+  ///
+  /// When `visitor` returns true, the walk will continue. When `visitor` returns
+  /// false, then the walk will end.
+  bool visitChildren(InlineSpanVisitor visitor);
+
+  /// Returns the text span that contains the given position in the text.
+  InlineSpan getSpanForPosition(TextPosition position) {
+    assert(debugAssertIsValid());
+    final Accumulator offset = Accumulator();
+    InlineSpan result;
+    visitChildren((InlineSpan span) {
+      result = span.getSpanForPositionVisitor(position, offset);
+      return result == null;
+    });
+    return result;
+  }
+
+  /// Performs the check at each [InlineSpan] for if the `position` falls within the range
+  /// of the span and returns the span if it does.
+  ///
+  /// The `offset` parameter tracks the current index offset in the text buffer formed
+  /// if the contents of the [InlineSpan] tree were concatenated together starting
+  /// from the root [InlineSpan].
+  ///
+  /// This method should not be directly called. Use [getSpanForPosition] instead.
+  @protected
+  InlineSpan getSpanForPositionVisitor(TextPosition position, Accumulator offset);
+
+  /// Flattens the [InlineSpan] tree into a single string.
+  ///
+  /// Styles are not honored in this process. If `includeSemanticsLabels` is
+  /// true, then the text returned will include the [TextSpan.semanticsLabel]s
+  /// instead of the text contents for [TextSpan]s.
+  ///
+  /// When `includePlaceholders` is true, [PlaceholderSpan]s in the tree will be
+  /// represented as a 0xFFFC 'object replacement character'.
+  String toPlainText({bool includeSemanticsLabels = true, bool includePlaceholders = true}) {
+    final StringBuffer buffer = StringBuffer();
+    computeToPlainText(buffer, includeSemanticsLabels: includeSemanticsLabels, includePlaceholders: includePlaceholders);
+    return buffer.toString();
+  }
+
+  /// Walks the [InlineSpan] tree and writes the plain text representation to `buffer`.
+  ///
+  /// This method should not be directly called. Use [toPlainText] instead.
+  ///
+  /// Styles are not honored in this process. If `includeSemanticsLabels` is
+  /// true, then the text returned will include the [TextSpan.semanticsLabel]s
+  /// instead of the text contents for [TextSpan]s.
+  ///
+  /// When `includePlaceholders` is true, [PlaceholderSpan]s in the tree will be
+  /// represented as a 0xFFFC 'object replacement character'.
+  ///
+  /// The plain-text representation of this [InlineSpan] is written into the `buffer`.
+  /// This method will then recursively call [computeToPlainText] on its childen
+  /// [InlineSpan]s if available.
+  @protected
+  void computeToPlainText(StringBuffer buffer, {bool includeSemanticsLabels = true, bool includePlaceholders = true});
+
+  /// Returns the UTF-16 code unit at the given `index` in the flattened string.
+  ///
+  /// This only accounts for the [TextSpan.text] values and ignores [PlaceholderSpans].
+  ///
+  /// Returns null if the `index` is out of bounds.
+  int codeUnitAt(int index) {
+    if (index < 0)
+      return null;
+    final Accumulator offset = Accumulator();
+    int result;
+    visitChildren((InlineSpan span) {
+      result = span.codeUnitAtVisitor(index, offset);
+      return result == null;
+    });
+    return result;
+  }
+
+  /// Performs the check at each [InlineSpan] for if the `index` falls within the range
+  /// of the span and returns the corresponding code unit. Returns null otherwise.
+  ///
+  /// The `offset` parameter tracks the current index offset in the text buffer formed
+  /// if the contents of the [InlineSpan] tree were concatenated together starting
+  /// from the root [InlineSpan].
+  ///
+  /// This method should not be directly called. Use [codeUnitAt] instead.
+  @protected
+  int codeUnitAtVisitor(int index, Accumulator offset);
+
+  /// Populates the `semanticsOffsets` and `semanticsElements` with the appropriate data
+  /// to be able to construct a [SemanticsNode].
+  ///
+  /// If applicable, the beginning and end text offset are added to [semanticsOffsets].
+  /// [PlaceholderSpan]s have a text length of 1, which corresponds to the object
+  /// replacement character (0xFFFC) that is inserted to represent it.
+  ///
+  /// Any [GestureRecognizer]s are added to `semanticsElements`. Null is added to
+  /// `semanticsElements` for [PlaceholderSpan]s.
+  void describeSemantics(Accumulator offset, List<int> semanticsOffsets, List<dynamic> semanticsElements);
+
+  /// In checked mode, throws an exception if the object is not in a
+  /// valid configuration. Otherwise, returns true.
+  ///
+  /// This is intended to be used as follows:
+  ///
+  /// ```dart
+  /// assert(myInlineSpan.debugAssertIsValid());
+  /// ```
+  bool debugAssertIsValid() => true;
+
+  /// Describe the difference between this span and another, in terms of
+  /// how much damage it will make to the rendering. The comparison is deep.
+  ///
+  /// Comparing [InlineSpan] objects of different types, for example, comparing
+  /// a [TextSpan] to a [WidgetSpan], always results in [RenderComparison.layout].
+  ///
+  /// See also:
+  ///
+  ///  * [TextStyle.compareTo], which does the same thing for [TextStyle]s.
+  RenderComparison compareTo(InlineSpan other);
+
+  @override
+  bool operator ==(dynamic other) {
+    if (identical(this, other))
+      return true;
+    if (other.runtimeType != runtimeType)
+      return false;
+    final InlineSpan typedOther = other;
+    return typedOther.style == style;
+  }
+
+  @override
+  int get hashCode => style.hashCode;
+
+  @override
+  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
+    super.debugFillProperties(properties);
+    properties.defaultDiagnosticsTreeStyle = DiagnosticsTreeStyle.whitespace;
+
+    if (style != null) {
+      style.debugFillProperties(properties);
+    }
+  }
+}

packages/flutter/lib/src/painting/placeholder_span.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 'dart:ui' as ui show PlaceholderAlignment;
+
+import 'package:flutter/foundation.dart';
+
+import 'basic_types.dart';
+import 'inline_span.dart';
+import 'text_painter.dart';
+import 'text_span.dart';
+import 'text_style.dart';
+
+/// An immutable placeholder that is embedded inline within text.
+///
+/// [PlaceholderSpan] represents a placeholder that acts as a stand-in for other
+/// content. A [PlaceholderSpan] by itself does not contain useful
+/// information to change a [TextSpan]. Instead, this class must be extended
+/// to define contents.
+///
+/// [WidgetSpan] from the widgets library extends [PlaceholderSpan] and may be
+/// used instead to specify a widget as the contents of the placeholder.
+///
+/// See also:
+///
+///  * [WidgetSpan], a leaf node that represents an embedded inline widget.
+///  * [TextSpan], a node that represents text in a [TextSpan] tree.
+///  * [Text], a widget for showing uniformly-styled text.
+///  * [RichText], a widget for finer control of text rendering.
+///  * [TextPainter], a class for painting [TextSpan] objects on a [Canvas].
+abstract class PlaceholderSpan extends InlineSpan {
+  /// Creates a [PlaceholderSpan] with the given values.
+  ///
+  /// A [TextStyle] may be provided with the [style] property, but only the
+  /// decoration, foreground, background, and spacing options will be used.
+  const PlaceholderSpan({
+    this.alignment = ui.PlaceholderAlignment.bottom,
+    this.baseline,
+    TextStyle style,
+  }) : super(style: style,);
+
+  /// How the placeholder aligns vertically with the text.
+  ///
+  /// See [ui.PlaceholderAlignment] for details on each mode.
+  final ui.PlaceholderAlignment alignment;
+
+  /// The [TextBaseline] to align against when using [ui.PlaceholderAlignment.baseline],
+  /// [ui.PlaceholderAlignment.aboveBaseline], and [ui.PlaceholderAlignment.belowBaseline].
+  ///
+  /// This is ignored when using other alignment modes.
+  final TextBaseline baseline;
+
+  /// [PlaceholderSpan]s are flattened to a `0xFFFC` object replacement character in the
+  /// plain text representation when `includePlaceholders` is true.
+  @override
+  void computeToPlainText(StringBuffer buffer, {bool includeSemanticsLabels = true, bool includePlaceholders = true}) {
+    if (includePlaceholders) {
+      buffer.write('\uFFFC');
+    }
+  }
+
+  /// Populates the `semanticsOffsets` and `semanticsElements` with the appropriate data
+  /// to be able to construct a [SemanticsNode].
+  ///
+  /// [PlaceholderSpan]s have a text length of 1, which corresponds to the object
+  /// replacement character (0xFFFC) that is inserted to represent it.
+  ///
+  /// Null is added to `semanticsElements` for [PlaceholderSpan]s.
+  @override
+  void describeSemantics(Accumulator offset, List<int> semanticsOffsets, List<dynamic> semanticsElements) {
+    semanticsOffsets.add(offset.value);
+    semanticsOffsets.add(offset.value + 1);
+    semanticsElements.add(null); // null indicates this is a placeholder.
+    offset.increment(1);
+  }
+
+  @override
+  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
+    super.debugFillProperties(properties);
+
+    properties.add(EnumProperty<ui.PlaceholderAlignment>('alignment', alignment, defaultValue: null));
+    properties.add(EnumProperty<TextBaseline>('baseline', baseline, defaultValue: null));
+  }
+}

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

@@ -3,18 +3,82 @@
 // found in the LICENSE file.
 
 import 'dart:math' show min, max;
-import 'dart:ui' as ui show Paragraph, ParagraphBuilder, ParagraphConstraints, ParagraphStyle;
+import 'dart:ui' as ui show Paragraph, ParagraphBuilder, ParagraphConstraints, ParagraphStyle, PlaceholderAlignment;
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/services.dart';
 
 import 'basic_types.dart';
+import 'inline_span.dart';
+import 'placeholder_span.dart';
 import 'strut_style.dart';
 import 'text_span.dart';
 
 export 'package:flutter/services.dart' show TextRange, TextSelection;
 
+/// Holds the [Size] and baseline required to represent the dimensions of
+/// a placeholder in text.
+///
+/// Placeholders specify an empty space in the text layout, which is used
+/// to later render arbitrary inline widgets into defined by a [WidgetSpan].
+///
+/// The [size] and [alignment] properties are required and cannot be null.
+///
+/// See also:
+///
+///  * [WidgetSpan], a subclass of [InlineSpan] and [PlaceholderSpan] that
+///    represents an inline widget embedded within text. The space this
+///    widget takes is indicated by a placeholder.
+///  * [RichText], a text widget that supports text inline widgets.
+@immutable
+class PlaceholderDimensions {
+  /// Constructs a [PlaceholderDimensions] with the specified parameters.
+  ///
+  /// The `size` and `alignment` are required as a placeholder's dimensions
+  /// require at least `size` and `alignment` to be fully defined.
+  const PlaceholderDimensions({
+    @required this.size,
+    @required this.alignment,
+    this.baseline,
+    this.baselineOffset,
+  }) : assert(size != null),
+       assert(alignment != null);
+
+  /// Width and height dimensions of the placeholder.
+  final Size size;
+
+  /// How to align the placeholder with the text.
+  ///
+  /// See also:
+  ///
+  ///  * [baseline], the baseline to align to when using
+  ///    [ui.PlaceholderAlignment.baseline],
+  ///    [ui.PlaceholderAlignment.aboveBaseline],
+  ///    or [ui.PlaceholderAlignment.underBaseline].
+  ///  * [baselineOffset], the distance of the alphabetic baseline from the upper
+  ///    edge of the placeholder.
+  final ui.PlaceholderAlignment alignment;
+
+  /// Distance of the [baseline] from the upper edge of the placeholder.
+  ///
+  /// Only used when [alignment] is [ui.PlaceholderAlignment.baseline].
+  final double baselineOffset;
+
+  /// The [TextBaseline] to align to. Used with:
+  ///
+  ///  * [ui.PlaceholderAlignment.baseline]
+  ///  * [ui.PlaceholderAlignment.aboveBaseline]
+  ///  * [ui.PlaceholderAlignment.underBaseline]
+  ///  * [ui.PlaceholderAlignment.middle]
+  final TextBaseline baseline;
+
+  @override
+  String toString() {
+    return 'PlaceholderDimensions($size, $baseline)';
+  }
+}
+
 /// The different ways of considering the width of one or more lines of text.
 ///
 /// See [Text.widthType].
@@ -30,6 +94,9 @@ enum TextWidthBasis {
   longestLine,
 }
 
+/// This is used to cache and pass the computed metrics regarding the
+/// caret's size and position. This is preferred due to the expensive
+/// nature of the calculation.
 class _CaretMetrics {
   const _CaretMetrics({this.offset, this.fullHeight});
   /// The offset of the top left corner of the caret from the top left
@@ -67,7 +134,7 @@ class TextPainter {
   ///
   /// The [maxLines] property, if non-null, must be greater than zero.
   TextPainter({
-    TextSpan text,
+    InlineSpan text,
     TextAlign textAlign = TextAlign.start,
     TextDirection textDirection,
     double textScaleFactor = 1.0,
@@ -99,9 +166,9 @@ class TextPainter {
   /// After this is set, you must call [layout] before the next call to [paint].
   ///
   /// This and [textDirection] must be non-null before you call [layout].
-  TextSpan get text => _text;
-  TextSpan _text;
-  set text(TextSpan value) {
+  InlineSpan get text => _text;
+  InlineSpan _text;
+  set text(InlineSpan value) {
     assert(value == null || value.debugAssertIsValid());
     if (_text == value)
       return;
@@ -266,6 +333,49 @@ class TextPainter {
 
   ui.Paragraph _layoutTemplate;
 
+  /// An ordered list of [TextBox]es that bound the positions of the placeholders
+  /// in the paragraph.
+  ///
+  /// Each box corresponds to a [PlaceholderSpan] in the order they were defined
+  /// in the [InlineSpan] tree.
+  List<TextBox> get inlinePlaceholderBoxes => _inlinePlaceholderBoxes;
+  List<TextBox> _inlinePlaceholderBoxes;
+
+  /// An ordered list of scales for each placeholder in the paragraph.
+  ///
+  /// The scale is used as a multiplier on the height, width and baselineOffset of
+  /// the placeholder. Scale is primarily used to handle accessibility scaling.
+  ///
+  /// Each scale corresponds to a [PlaceholderSpan] in the order they were defined
+  /// in the [InlineSpan] tree.
+  List<double> get inlinePlaceholderScales => _inlinePlaceholderScales;
+  List<double> _inlinePlaceholderScales;
+
+  /// Sets the dimensions of each placeholder in [text].
+  ///
+  /// The number of [PlaceholderDimensions] provided should be the same as the
+  /// number of [PlaceholderSpan]s in text.
+  ///
+  /// If [layout] is attempted without setting the placeholder dimensions, the
+  /// placeholders will be ignored in the text layout and no valid
+  /// [inlinePlaceholderBoxes] will be returned.
+  void setPlaceholderDimensions(List<PlaceholderDimensions> value) {
+    assert(() {
+      int placeholderCount = 0;
+      text.visitChildren((InlineSpan span) {
+        if (span is PlaceholderSpan) {
+          placeholderCount += 1;
+        }
+        return true;
+      });
+      return placeholderCount;
+    }() == value.length);
+    _placeholderDimensions = value;
+    _needsLayout = true;
+    _paragraph = null;
+  }
+  List<PlaceholderDimensions> _placeholderDimensions;
+
   ui.ParagraphStyle _createParagraphStyle([ TextDirection defaultTextDirection ]) {
     // The defaultTextDirection argument is used for preferredLineHeight in case
     // textDirection hasn't yet been set.
@@ -419,7 +529,8 @@ class TextPainter {
     _needsLayout = false;
     if (_paragraph == null) {
       final ui.ParagraphBuilder builder = ui.ParagraphBuilder(_createParagraphStyle());
-      _text.build(builder, textScaleFactor: textScaleFactor);
+      _text.build(builder, textScaleFactor: textScaleFactor, dimensions: _placeholderDimensions);
+      _inlinePlaceholderScales = builder.placeholderScales;
       _paragraph = builder.build();
     }
     _lastMinWidth = minWidth;
@@ -427,9 +538,11 @@ class TextPainter {
     _paragraph.layout(ui.ParagraphConstraints(width: maxWidth));
     if (minWidth != maxWidth) {
       final double newWidth = maxIntrinsicWidth.clamp(minWidth, maxWidth);
-      if (newWidth != width)
+      if (newWidth != width) {
         _paragraph.layout(ui.ParagraphConstraints(width: newWidth));
+      }
     }
+    _inlinePlaceholderBoxes = _paragraph.getBoxesForPlaceholders();
   }
 
   /// Paints the text onto the given canvas at the given offset.
@@ -491,7 +604,7 @@ class TextPainter {
   // TODO(garyq): Use actual extended grapheme cluster length instead of
   // an increasing cluster length amount to achieve deterministic performance.
   Rect _getRectFromUpstream(int offset, Rect caretPrototype) {
-    final String flattenedText = _text.toPlainText();
+    final String flattenedText = _text.toPlainText(includePlaceholders: false);
     final int prevCodeUnit = _text.codeUnitAt(max(0, offset - 1));
     if (prevCodeUnit == null)
       return null;
@@ -507,10 +620,12 @@ class TextPainter {
       if (boxes.isEmpty) {
         // When we are at the beginning of the line, a non-surrogate position will
         // return empty boxes. We break and try from downstream instead.
-        if (!needsSearch)
+        if (!needsSearch) {
           break; // Only perform one iteration if no search is required.
-        if (prevRuneOffset < -flattenedText.length)
+        }
+        if (prevRuneOffset < -flattenedText.length) {
           break; // Stop iterating when beyond the max length of the text.
+        }
         // Multiply by two to log(n) time cover the entire text span. This allows
         // faster discovery of very long clusters and reduces the possibility
         // of certain large clusters taking much longer than others, which can
@@ -538,7 +653,7 @@ class TextPainter {
   // TODO(garyq): Use actual extended grapheme cluster length instead of
   // an increasing cluster length amount to achieve deterministic performance.
   Rect _getRectFromDownstream(int offset, Rect caretPrototype) {
-    final String flattenedText = _text.toPlainText();
+    final String flattenedText = _text.toPlainText(includePlaceholders: false);
     // We cap the offset at the final index of the _text.
     final int nextCodeUnit = _text.codeUnitAt(min(offset, flattenedText == null ? 0 : flattenedText.length - 1));
     if (nextCodeUnit == null)
@@ -554,10 +669,12 @@ class TextPainter {
       if (boxes.isEmpty) {
         // When we are at the end of the line, a non-surrogate position will
         // return empty boxes. We break and try from upstream instead.
-        if (!needsSearch)
+        if (!needsSearch) {
           break; // Only perform one iteration if no search is required.
-        if (nextRuneOffset >= flattenedText.length << 1)
+        }
+        if (nextRuneOffset >= flattenedText.length << 1) {
           break; // Stop iterating when beyond the max length of the text.
+        }
         // Multiply by two to log(n) time cover the entire text span. This allows
         // faster discovery of very long clusters and reduces the possibility
         // of certain large clusters taking much longer than others, which can

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

@@ -1728,7 +1728,10 @@ abstract class RenderBox extends RenderObject {
       return true;
     }());
     _size = value;
-    assert(() { debugAssertDoesMeetConstraints(); return true; }());
+    assert(() {
+      debugAssertDoesMeetConstraints();
+      return true;
+    }());
   }
 
   /// Claims ownership of the given [Size].

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

@@ -284,8 +284,8 @@ mixin DebugOverflowIndicatorMixin on RenderObject {
     final List<_OverflowRegionData> overflowRegions = _calculateOverflowRegions(overflow, containerRect);
     for (_OverflowRegionData region in overflowRegions) {
       context.canvas.drawRect(region.rect.shift(offset), _indicatorPaint);
-
-      if (_indicatorLabel[region.side.index].text?.text != region.label) {
+      final TextSpan textSpan = _indicatorLabel[region.side.index].text;
+      if (textSpan?.text != region.label) {
         _indicatorLabel[region.side.index].text = TextSpan(
           text: region.label,
           style: _indicatorTextStyle,

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

@@ -12,6 +12,7 @@ import 'package:flutter/services.dart';
 import 'debug.dart';
 import 'framework.dart';
 import 'localizations.dart';
+import 'widget_span.dart';
 
 export 'package:flutter/animation.dart';
 export 'package:flutter/foundation.dart' show
@@ -4913,7 +4914,9 @@ class Flow extends MultiChildRenderObjectWidget {
 ///  * [TextSpan], which is used to describe the text in a paragraph.
 ///  * [Text], which automatically applies the ambient styles described by a
 ///    [DefaultTextStyle] to a single string.
-class RichText extends LeafRenderObjectWidget {
+///  * [Text.rich], a const text widget that provides similar functionality
+///    as [RichText]. [Text.rich] will inherit [TextStyle] from [DefaultTextStyle].
+class RichText extends MultiChildRenderObjectWidget {
   /// Creates a paragraph of rich text.
   ///
   /// The [text], [textAlign], [softWrap], [overflow], and [textScaleFactor]
@@ -4924,7 +4927,7 @@ class RichText extends LeafRenderObjectWidget {
   ///
   /// The [textDirection], if null, defaults to the ambient [Directionality],
   /// which in that case must not be null.
-  const RichText({
+  RichText({
     Key key,
     @required this.text,
     this.textAlign = TextAlign.start,
@@ -4943,10 +4946,23 @@ class RichText extends LeafRenderObjectWidget {
        assert(textScaleFactor != null),
        assert(maxLines == null || maxLines > 0),
        assert(textWidthBasis != null),
-       super(key: key);
+       super(key: key, children: _extractChildren(text));
+
+  // Traverses the InlineSpan tree and depth-first collects the list of
+  // child widgets that are created in WidgetSpans.
+  static List<Widget> _extractChildren(InlineSpan span) {
+    final List<Widget> result = <Widget>[];
+    span.visitChildren((InlineSpan span) {
+      if (span is WidgetSpan) {
+        result.add(span.child);
+      }
+      return true;
+    });
+    return result;
+  }
 
   /// The text to display in this widget.
-  final TextSpan text;
+  final InlineSpan text;
 
   /// How the text should be aligned horizontally.
   final TextAlign textAlign;

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

@@ -256,9 +256,16 @@ class Text extends StatelessWidget {
        textSpan = null,
        super(key: key);
 
-  /// Creates a text widget with a [TextSpan].
+  /// Creates a text widget with a [InlineSpan].
+  ///
+  /// The following subclasses of [InlineSpan] may be used to build rich text:
+  ///
+  /// * [TextSpan]s define text and children [InlineSpan]s.
+  /// * [WidgetSpan]s define embedded inline widgets.
   ///
   /// The [textSpan] parameter must not be null.
+  ///
+  /// See [RichText] which provides a lower-level way to draw text.
   const Text.rich(
     this.textSpan, {
     Key key,
@@ -285,10 +292,10 @@ class Text extends StatelessWidget {
   /// This will be null if a [textSpan] is provided instead.
   final String data;
 
-  /// The text to display as a [TextSpan].
+  /// The text to display as a [InlineSpan].
   ///
   /// This will be null if [data] is provided instead.
-  final TextSpan textSpan;
+  final InlineSpan textSpan;
 
   /// If non-null, the style to use for this text.
   ///

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

@@ -2752,7 +2752,8 @@ class _InspectorOverlayLayer extends Layer {
   ) {
     canvas.save();
     final double maxWidth = size.width - 2 * (_kScreenEdgeMargin + _kTooltipPadding);
-    if (_textPainter == null || _textPainter.text.text != message || _textPainterMaxWidth != maxWidth) {
+    final TextSpan textSpan = _textPainter?.text;
+    if (_textPainter == null || textSpan.text != message || _textPainterMaxWidth != maxWidth) {
       _textPainterMaxWidth = maxWidth;
       _textPainter = TextPainter()
         ..maxLines = _kMaxTooltipLines

packages/flutter/lib/src/widgets/widget_span.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 'dart:ui' as ui show ParagraphBuilder, PlaceholderAlignment;
+
+import 'package:flutter/painting.dart';
+
+import 'framework.dart';
+
+/// An immutable widget that is embedded inline within text.
+///
+/// The [child] property is the widget that will be embedded. Children are
+/// constrained by the width of the paragraph.
+///
+/// The [child] property may contain its own [Widget] children (if applicable),
+/// including [Text] and [RichText] widgets which may include additional
+/// [WidgetSpan]s. Child [Text] and [RichText] widgets will be laid out
+/// independently and occupy a rectangular space in the parent text layout.
+///
+/// [WidgetSpan]s will be ignored when passed into a [TextPainter] directly.
+/// To properly layout and paint the [child] widget, [WidgetSpan] should be
+/// passed into a [Text.rich] widget.
+///
+/// {@tool sample}
+///
+/// A card with `Hello World!` embedded inline within a TextSpan tree.
+///
+/// ```dart
+/// Text.rich(
+///   TextSpan(
+///     children: <InlineSpan>[
+///       TextSpan(text: 'Flutter is'),
+///       WidgetSpan(
+///         child: SizedBox(
+///           width: 120,
+///           height: 50,
+///           child: Card(
+///             child: Center(
+///               child: Text('Hello World!')
+///             )
+///           ),
+///         )
+///       ),
+///       TextSpan(text: 'the best!'),
+///     ],
+///   )
+/// )
+/// ```
+/// {@end-tool}
+///
+/// [WidgetSpan] contributes the semantics of the [WidgetSpan.child] to the
+/// semantics tree.
+///
+/// See also:
+///
+///  * [TextSpan], a node that represents text in an [InlineSpan] tree.
+///  * [Text], a widget for showing uniformly-styled text.
+///  * [RichText], a widget for finer control of text rendering.
+///  * [TextPainter], a class for painting [InlineSpan] objects on a [Canvas].
+@immutable
+class WidgetSpan extends PlaceholderSpan {
+  /// Creates a [WidgetSpan] with the given values.
+  ///
+  /// The [child] property must be non-null. [WidgetSpan] is a leaf node in
+  /// the [InlineSpan] tree. Child widgets are constrained by the width of the
+  /// paragraph they occupy. Child widget heights are unconstrained, and may
+  /// cause the text to overflow and be ellipsized/truncated.
+  ///
+  /// A [TextStyle] may be provided with the [style] property, but only the
+  /// decoration, foreground, background, and spacing options will be used.
+  const WidgetSpan({
+    @required this.child,
+    ui.PlaceholderAlignment alignment = ui.PlaceholderAlignment.bottom,
+    TextBaseline baseline,
+    TextStyle style,
+  }) : assert(child != null),
+       assert((identical(alignment, ui.PlaceholderAlignment.aboveBaseline) ||
+              identical(alignment, ui.PlaceholderAlignment.belowBaseline) ||
+              identical(alignment, ui.PlaceholderAlignment.baseline)) ? baseline != null : true),
+       super(
+         alignment: alignment,
+         baseline: baseline,
+         style: style,
+       );
+
+  /// The widget to embed inline within text.
+  final Widget child;
+
+  /// Adds a placeholder box to the paragraph builder if a size has been
+  /// calculated for the widget.
+  ///
+  /// Sizes are provided through `dimensions`, which should contain a 1:1
+  /// in-order mapping of widget to laid-out dimensions. If no such dimension
+  /// is provided, the widget will be skipped.
+  ///
+  /// The `textScaleFactor` will be applied to the laid-out size of the widget.
+  @override
+  void build(ui.ParagraphBuilder builder, { double textScaleFactor = 1.0, @required List<PlaceholderDimensions> dimensions }) {
+    assert(debugAssertIsValid());
+    assert(dimensions != null);
+    final bool hasStyle = style != null;
+    if (hasStyle) {
+      builder.pushStyle(style.getTextStyle(textScaleFactor: textScaleFactor));
+    }
+    assert(builder.placeholderCount < dimensions.length);
+    final PlaceholderDimensions currentDimensions = dimensions[builder.placeholderCount];
+    builder.addPlaceholder(
+      currentDimensions.size.width,
+      currentDimensions.size.height,
+      alignment,
+      scale: textScaleFactor,
+      baseline: currentDimensions.baseline,
+      baselineOffset: currentDimensions.baselineOffset,
+    );
+    if (hasStyle) {
+      builder.pop();
+    }
+  }
+
+  /// Calls `visitor` on this [WidgetSpan]. There are no children spans to walk.
+  @override
+  bool visitChildren(InlineSpanVisitor visitor) {
+    return visitor(this);
+  }
+
+  @override
+  InlineSpan getSpanForPositionVisitor(TextPosition position, Accumulator offset) {
+    return null;
+  }
+
+  @override
+  int codeUnitAtVisitor(int index, Accumulator offset) {
+    return null;
+  }
+
+  @override
+  RenderComparison compareTo(InlineSpan other) {
+    if (identical(this, other))
+      return RenderComparison.identical;
+    if (other.runtimeType != runtimeType)
+      return RenderComparison.layout;
+    if ((style == null) != (other.style == null))
+      return RenderComparison.layout;
+    final WidgetSpan typedOther = other;
+    if (child != typedOther.child || alignment != typedOther.alignment) {
+      return RenderComparison.layout;
+    }
+    RenderComparison result = RenderComparison.identical;
+    if (style != null) {
+      final RenderComparison candidate = style.compareTo(other.style);
+      if (candidate.index > result.index)
+        result = candidate;
+      if (result == RenderComparison.layout)
+        return result;
+    }
+    return result;
+  }
+
+  @override
+  bool operator ==(dynamic other) {
+    if (identical(this, other))
+      return true;
+    if (other.runtimeType != runtimeType)
+      return false;
+    if (super != other)
+      return false;
+    final WidgetSpan typedOther = other;
+    return typedOther.child == child
+        && typedOther.alignment == alignment
+        && typedOther.baseline == baseline;
+  }
+
+  @override
+  int get hashCode => hashValues(super.hashCode, child, alignment, baseline);
+
+  /// Returns the text span that contains the given position in the text.
+  @override
+  InlineSpan getSpanForPosition(TextPosition position) {
+    assert(debugAssertIsValid());
+    return null;
+  }
+
+  /// In debug mode, throws an exception if the object is not in a
+  /// valid configuration. Otherwise, returns true.
+  ///
+  /// This is intended to be used as follows:
+  ///
+  /// ```dart
+  /// assert(myWidgetSpan.debugAssertIsValid());
+  /// ```
+  @override
+  bool debugAssertIsValid() {
+    // WidgetSpans are always valid as asserts prevent invalid WidgetSpans
+    // from being constructed.
+    return true;
+  }
+}

packages/flutter/lib/widgets.dart

@@ -108,4 +108,5 @@ export 'src/widgets/value_listenable_builder.dart';
 export 'src/widgets/viewport.dart';
 export 'src/widgets/visibility.dart';
 export 'src/widgets/widget_inspector.dart';
+export 'src/widgets/widget_span.dart';
 export 'src/widgets/will_pop_scope.dart';

packages/flutter/test/painting/text_painter_rtl_test.dart

@@ -43,7 +43,8 @@ void main() {
            //      0       12345678      9      101234567       18     90123456       27
       style: TextStyle(fontFamily: 'Ahem', fontSize: 10.0),
     );
-    expect(painter.text.text.length, 28);
+    TextSpan textSpan = painter.text;
+    expect(textSpan.text.length, 28);
     painter.layout();
 
     // The skips here are because the old rendering code considers the bidi formatting characters
@@ -127,7 +128,8 @@ void main() {
     );
 
     final List<List<TextBox>> list = <List<TextBox>>[];
-    for (int index = 0; index < painter.text.text.length; index += 1)
+    textSpan = painter.text;
+    for (int index = 0; index < textSpan.text.length; index += 1)
       list.add(painter.getBoxesForSelection(TextSelection(baseOffset: index, extentOffset: index + 1)));
     expect(list, const <List<TextBox>>[
       <TextBox>[], // U+202E, non-printing Unicode bidi formatting character
@@ -172,7 +174,8 @@ void main() {
            //      0       12345678      9      101234567       18     90123456       27
       style: TextStyle(fontFamily: 'Ahem', fontSize: 10.0),
     );
-    expect(painter.text.text.length, 28);
+    final TextSpan textSpan = painter.text;
+    expect(textSpan.text.length, 28);
     painter.layout();
 
     final TextRange hebrew1 = painter.getWordBoundary(const TextPosition(offset: 4, affinity: TextAffinity.downstream));
@@ -261,7 +264,8 @@ void main() {
       text: 'A\u05D0', // A, Alef
       style: TextStyle(fontFamily: 'Ahem', fontSize: 10.0),
     );
-    expect(painter.text.text.length, 2);
+    final TextSpan textSpan = painter.text;
+    expect(textSpan.text.length, 2);
     painter.layout(maxWidth: 10.0);
 
     for (int index = 0; index <= 2; index += 1) {

packages/flutter/test/painting/text_painter_test.dart

@@ -5,6 +5,7 @@
 import 'dart:ui' as ui;
 
 import 'package:flutter/painting.dart';
+import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 void main() {
@@ -634,4 +635,98 @@ void main() {
     expect(caretOffset.dx, closeTo(0.0, 0.0001));
     expect(caretOffset.dy, closeTo(0.0, 0.0001));
   });
+
+  test('TextPainter widget span', () {
+    final TextPainter painter = TextPainter()
+      ..textDirection = TextDirection.ltr;
+
+    const String text = 'test';
+    painter.text = const TextSpan(
+      text: text,
+      children: <InlineSpan>[
+        WidgetSpan(child: SizedBox(width: 50, height: 30)),
+        TextSpan(text: text),
+        WidgetSpan(child: SizedBox(width: 50, height: 30)),
+        WidgetSpan(child: SizedBox(width: 50, height: 30)),
+        TextSpan(text: text),
+        WidgetSpan(child: SizedBox(width: 50, height: 30)),
+        WidgetSpan(child: SizedBox(width: 50, height: 30)),
+        WidgetSpan(child: SizedBox(width: 50, height: 30)),
+        WidgetSpan(child: SizedBox(width: 50, height: 30)),
+        WidgetSpan(child: SizedBox(width: 50, height: 30)),
+        WidgetSpan(child: SizedBox(width: 50, height: 30)),
+        WidgetSpan(child: SizedBox(width: 50, height: 30)),
+        WidgetSpan(child: SizedBox(width: 50, height: 30)),
+        WidgetSpan(child: SizedBox(width: 50, height: 30)),
+        WidgetSpan(child: SizedBox(width: 50, height: 30)),
+        WidgetSpan(child: SizedBox(width: 50, height: 30)),
+      ]
+    );
+
+    // We provide dimensions for the widgets
+    painter.setPlaceholderDimensions(const <PlaceholderDimensions>[
+      PlaceholderDimensions(size: Size(50, 30), baselineOffset: 25, alignment: ui.PlaceholderAlignment.bottom),
+      PlaceholderDimensions(size: Size(50, 30), baselineOffset: 25, alignment: ui.PlaceholderAlignment.bottom),
+      PlaceholderDimensions(size: Size(50, 30), baselineOffset: 25, alignment: ui.PlaceholderAlignment.bottom),
+      PlaceholderDimensions(size: Size(50, 30), baselineOffset: 25, alignment: ui.PlaceholderAlignment.bottom),
+      PlaceholderDimensions(size: Size(50, 30), baselineOffset: 25, alignment: ui.PlaceholderAlignment.bottom),
+      PlaceholderDimensions(size: Size(50, 30), baselineOffset: 25, alignment: ui.PlaceholderAlignment.bottom),
+      PlaceholderDimensions(size: Size(50, 30), baselineOffset: 25, alignment: ui.PlaceholderAlignment.bottom),
+      PlaceholderDimensions(size: Size(50, 30), baselineOffset: 25, alignment: ui.PlaceholderAlignment.bottom),
+      PlaceholderDimensions(size: Size(50, 30), baselineOffset: 25, alignment: ui.PlaceholderAlignment.bottom),
+      PlaceholderDimensions(size: Size(50, 30), baselineOffset: 25, alignment: ui.PlaceholderAlignment.bottom),
+      PlaceholderDimensions(size: Size(50, 30), baselineOffset: 25, alignment: ui.PlaceholderAlignment.bottom),
+      PlaceholderDimensions(size: Size(50, 30), baselineOffset: 25, alignment: ui.PlaceholderAlignment.bottom),
+      PlaceholderDimensions(size: Size(51, 30), baselineOffset: 25, alignment: ui.PlaceholderAlignment.bottom),
+      PlaceholderDimensions(size: Size(50, 30), baselineOffset: 25, alignment: ui.PlaceholderAlignment.bottom),
+    ]);
+
+    painter.layout(maxWidth: 500);
+
+    // Now, each of the WidgetSpans will have their own placeholder 'hole'.
+    Offset caretOffset = painter.getOffsetForCaret(const ui.TextPosition(offset: 1), ui.Rect.zero);
+    expect(caretOffset.dx, 14);
+    caretOffset = painter.getOffsetForCaret(const ui.TextPosition(offset: 4), ui.Rect.zero);
+    expect(caretOffset.dx, 56);
+    caretOffset = painter.getOffsetForCaret(const ui.TextPosition(offset: 5), ui.Rect.zero);
+    expect(caretOffset.dx, 106);
+    caretOffset = painter.getOffsetForCaret(const ui.TextPosition(offset: 6), ui.Rect.zero);
+    expect(caretOffset.dx, 120);
+    caretOffset = painter.getOffsetForCaret(const ui.TextPosition(offset: 10), ui.Rect.zero);
+    expect(caretOffset.dx, 212);
+    caretOffset = painter.getOffsetForCaret(const ui.TextPosition(offset: 11), ui.Rect.zero);
+    expect(caretOffset.dx, 262);
+    caretOffset = painter.getOffsetForCaret(const ui.TextPosition(offset: 12), ui.Rect.zero);
+    expect(caretOffset.dx, 276);
+    caretOffset = painter.getOffsetForCaret(const ui.TextPosition(offset: 13), ui.Rect.zero);
+    expect(caretOffset.dx, 290);
+    caretOffset = painter.getOffsetForCaret(const ui.TextPosition(offset: 14), ui.Rect.zero);
+    expect(caretOffset.dx, 304);
+    caretOffset = painter.getOffsetForCaret(const ui.TextPosition(offset: 15), ui.Rect.zero);
+    expect(caretOffset.dx, 318);
+    caretOffset = painter.getOffsetForCaret(const ui.TextPosition(offset: 16), ui.Rect.zero);
+    expect(caretOffset.dx, 368);
+    caretOffset = painter.getOffsetForCaret(const ui.TextPosition(offset: 17), ui.Rect.zero);
+    expect(caretOffset.dx, 418);
+    caretOffset = painter.getOffsetForCaret(const ui.TextPosition(offset: 18), ui.Rect.zero);
+    expect(caretOffset.dx, 0);
+    caretOffset = painter.getOffsetForCaret(const ui.TextPosition(offset: 19), ui.Rect.zero);
+    expect(caretOffset.dx, 50);
+    caretOffset = painter.getOffsetForCaret(const ui.TextPosition(offset: 23), ui.Rect.zero);
+    expect(caretOffset.dx, 250);
+
+    expect(painter.inlinePlaceholderBoxes.length, 14);
+    expect(painter.inlinePlaceholderBoxes[0], const TextBox.fromLTRBD(56, 0, 106, 30, TextDirection.ltr));
+    expect(painter.inlinePlaceholderBoxes[2], const TextBox.fromLTRBD(212, 0, 262, 30, TextDirection.ltr));
+    expect(painter.inlinePlaceholderBoxes[3], const TextBox.fromLTRBD(318, 0, 368, 30, TextDirection.ltr));
+    expect(painter.inlinePlaceholderBoxes[4], const TextBox.fromLTRBD(368, 0, 418, 30, TextDirection.ltr));
+    expect(painter.inlinePlaceholderBoxes[5], const TextBox.fromLTRBD(418, 0, 468, 30, TextDirection.ltr));
+    // line should break here
+    expect(painter.inlinePlaceholderBoxes[6], const TextBox.fromLTRBD(0, 30, 50, 60, TextDirection.ltr));
+    expect(painter.inlinePlaceholderBoxes[7], const TextBox.fromLTRBD(50, 30, 100, 60, TextDirection.ltr));
+    expect(painter.inlinePlaceholderBoxes[10], const TextBox.fromLTRBD(200, 30, 250, 60, TextDirection.ltr));
+    expect(painter.inlinePlaceholderBoxes[11], const TextBox.fromLTRBD(250, 30, 300, 60, TextDirection.ltr));
+    expect(painter.inlinePlaceholderBoxes[12], const TextBox.fromLTRBD(300, 30, 351, 60, TextDirection.ltr));
+    expect(painter.inlinePlaceholderBoxes[13], const TextBox.fromLTRBD(351, 30, 401, 60, TextDirection.ltr));
+  });
 }

packages/flutter/test/painting/text_span_test.dart

@@ -3,17 +3,17 @@
 // found in the LICENSE file.
 
 import 'package:flutter/painting.dart';
-import 'package:flutter_test/flutter_test.dart' show nonconst;
+import 'package:flutter/widgets.dart';
 import '../flutter_test_alternative.dart';
 
 void main() {
   test('TextSpan equals', () {
-    final TextSpan a1 = TextSpan(text: nonconst('a'));
-    final TextSpan a2 = TextSpan(text: nonconst('a'));
-    final TextSpan b1 = TextSpan(children: <TextSpan>[ a1 ]);
-    final TextSpan b2 = TextSpan(children: <TextSpan>[ a2 ]);
-    final TextSpan c1 = TextSpan(text: nonconst(null));
-    final TextSpan c2 = TextSpan(text: nonconst(null));
+    const TextSpan a1 = TextSpan(text: 'a');
+    const TextSpan a2 = TextSpan(text: 'a');
+    const TextSpan b1 = TextSpan(children: <TextSpan>[ a1 ]);
+    const TextSpan b2 = TextSpan(children: <TextSpan>[ a2 ]);
+    const TextSpan c1 = TextSpan(text: null);
+    const TextSpan c2 = TextSpan(text: null);
 
     expect(a1 == a2, isTrue);
     expect(b1 == b2, isTrue);
@@ -73,6 +73,18 @@ void main() {
     expect(textSpan.toPlainText(), 'abc');
   });
 
+  test('WidgetSpan toPlainText', () {
+    const TextSpan textSpan = TextSpan(
+      text: 'a',
+      children: <InlineSpan>[
+        TextSpan(text: 'b'),
+        WidgetSpan(child: SizedBox(width: 10, height: 10)),
+        TextSpan(text: 'c'),
+      ],
+    );
+    expect(textSpan.toPlainText(), 'ab\uFFFCc');
+  });
+
   test('TextSpan toPlainText with semanticsLabel', () {
     const TextSpan textSpan = TextSpan(
       text: 'a',
@@ -84,4 +96,117 @@ void main() {
     expect(textSpan.toPlainText(), 'afooc');
     expect(textSpan.toPlainText(includeSemanticsLabels: false), 'abc');
   });
+
+  test('TextSpan widget change test', () {
+    const TextSpan textSpan1 = TextSpan(
+      text: 'a',
+      children: <InlineSpan>[
+        TextSpan(text: 'b'),
+        WidgetSpan(child: SizedBox(width: 10, height: 10)),
+        TextSpan(text: 'c'),
+      ],
+    );
+
+    const TextSpan textSpan2 = TextSpan(
+      text: 'a',
+      children: <InlineSpan>[
+        TextSpan(text: 'b'),
+        WidgetSpan(child: SizedBox(width: 10, height: 10)),
+        TextSpan(text: 'c'),
+      ],
+    );
+
+    const TextSpan textSpan3 = TextSpan(
+      text: 'a',
+      children: <InlineSpan>[
+        TextSpan(text: 'b'),
+        WidgetSpan(child: SizedBox(width: 11, height: 10)),
+        TextSpan(text: 'c'),
+      ],
+    );
+
+    const TextSpan textSpan4 = TextSpan(
+      text: 'a',
+      children: <InlineSpan>[
+        TextSpan(text: 'b'),
+        WidgetSpan(child: Text('test')),
+        TextSpan(text: 'c'),
+      ],
+    );
+
+    const TextSpan textSpan5 = TextSpan(
+      text: 'a',
+      children: <InlineSpan>[
+        TextSpan(text: 'b'),
+        WidgetSpan(child: Text('different!')),
+        TextSpan(text: 'c'),
+      ],
+    );
+
+    const TextSpan textSpan6 = TextSpan(
+      text: 'a',
+      children: <InlineSpan>[
+        TextSpan(text: 'b'),
+        WidgetSpan(
+          child: SizedBox(width: 10, height: 10),
+          alignment: PlaceholderAlignment.top,
+        ),
+        TextSpan(text: 'c'),
+      ],
+    );
+
+    expect(textSpan1.compareTo(textSpan3), RenderComparison.layout);
+    expect(textSpan1.compareTo(textSpan4), RenderComparison.layout);
+    expect(textSpan1.compareTo(textSpan1), RenderComparison.identical);
+    expect(textSpan2.compareTo(textSpan2), RenderComparison.identical);
+    expect(textSpan3.compareTo(textSpan3), RenderComparison.identical);
+    expect(textSpan2.compareTo(textSpan3), RenderComparison.layout);
+    expect(textSpan4.compareTo(textSpan5), RenderComparison.layout);
+    expect(textSpan3.compareTo(textSpan5), RenderComparison.layout);
+    expect(textSpan2.compareTo(textSpan5), RenderComparison.layout);
+    expect(textSpan1.compareTo(textSpan5), RenderComparison.layout);
+    expect(textSpan1.compareTo(textSpan6), RenderComparison.layout);
+  });
+
+  test('TextSpan nested widget change test', () {
+    const TextSpan textSpan1 = TextSpan(
+      text: 'a',
+      children: <InlineSpan>[
+        TextSpan(text: 'b'),
+        WidgetSpan(
+          child: Text.rich(
+            TextSpan(
+              children: <InlineSpan>[
+                WidgetSpan(child: SizedBox(width: 10, height: 10)),
+                TextSpan(text: 'The sky is falling :)')
+              ],
+            )
+          ),
+        ),
+        TextSpan(text: 'c'),
+      ],
+    );
+
+    const TextSpan textSpan2 = TextSpan(
+      text: 'a',
+      children: <InlineSpan>[
+        TextSpan(text: 'b'),
+        WidgetSpan(
+          child: Text.rich(
+            TextSpan(
+              children: <InlineSpan>[
+                WidgetSpan(child: SizedBox(width: 10, height: 11)),
+                TextSpan(text: 'The sky is falling :)')
+              ],
+            )
+          ),
+        ),
+        TextSpan(text: 'c'),
+      ],
+    );
+
+    expect(textSpan1.compareTo(textSpan2), RenderComparison.layout);
+    expect(textSpan1.compareTo(textSpan1), RenderComparison.identical);
+    expect(textSpan2.compareTo(textSpan2), RenderComparison.identical);
+  });
 }

packages/flutter/test/rendering/paragraph_test.dart

@@ -5,6 +5,7 @@
 import 'dart:ui' as ui show TextBox;
 
 import 'package:flutter/rendering.dart';
+import 'package:flutter/widgets.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 
@@ -324,4 +325,93 @@ void main() {
     expect(paragraph.locale, const Locale('ja', 'JP'));
   });
 
+  test('inline widgets test', () {
+    const TextSpan text = TextSpan(
+      text: 'a',
+      style: TextStyle(fontSize: 10.0),
+      children: <InlineSpan>[
+        WidgetSpan(child: SizedBox(width: 21, height: 21)),
+        WidgetSpan(child: SizedBox(width: 21, height: 21)),
+        TextSpan(text: 'a'),
+        WidgetSpan(child: SizedBox(width: 21, height: 21)),
+      ],
+    );
+    // Fake the render boxes that correspond to the WidgetSpans. We use
+    // RenderParagraph to reduce dependencies this test has.
+    final List<RenderBox> renderBoxes = <RenderBox>[];
+    renderBoxes.add(RenderParagraph(const TextSpan(text: 'b'), textDirection: TextDirection.ltr));
+    renderBoxes.add(RenderParagraph(const TextSpan(text: 'b'), textDirection: TextDirection.ltr));
+    renderBoxes.add(RenderParagraph(const TextSpan(text: 'b'), textDirection: TextDirection.ltr));
+
+    final RenderParagraph paragraph = RenderParagraph(
+      text,
+      textDirection: TextDirection.ltr,
+      children: renderBoxes,
+    );
+    layout(paragraph, constraints: const BoxConstraints(maxWidth: 100.0));
+
+    final List<ui.TextBox> boxes = paragraph.getBoxesForSelection(
+        const TextSelection(baseOffset: 0, extentOffset: 8)
+    );
+
+    expect(boxes.length, equals(5));
+    expect(boxes[0], const TextBox.fromLTRBD(0.0, 4.0, 10.0, 14.0, TextDirection.ltr));
+    expect(boxes[1], const TextBox.fromLTRBD(10.0, 0.0, 24.0, 14.0, TextDirection.ltr));
+    expect(boxes[2], const TextBox.fromLTRBD(24.0, 0.0, 38.0, 14.0, TextDirection.ltr));
+    expect(boxes[3], const TextBox.fromLTRBD(38.0, 4.0, 48.0, 14.0, TextDirection.ltr));
+    expect(boxes[4], const TextBox.fromLTRBD(48.0, 0.0, 62.0, 14.0, TextDirection.ltr));
+  // Ahem-based tests don't yet quite work on Windows or some MacOS environments
+  }, skip: isWindows || isMacOS);
+
+  test('inline widgets multiline test', () {
+    const TextSpan text = TextSpan(
+      text: 'a',
+      style: TextStyle(fontSize: 10.0),
+      children: <InlineSpan>[
+        WidgetSpan(child: SizedBox(width: 21, height: 21)),
+        WidgetSpan(child: SizedBox(width: 21, height: 21)),
+        TextSpan(text: 'a'),
+        WidgetSpan(child: SizedBox(width: 21, height: 21)),
+        WidgetSpan(child: SizedBox(width: 21, height: 21)),
+        WidgetSpan(child: SizedBox(width: 21, height: 21)),
+        WidgetSpan(child: SizedBox(width: 21, height: 21)),
+        WidgetSpan(child: SizedBox(width: 21, height: 21)),
+      ],
+    );
+    // Fake the render boxes that correspond to the WidgetSpans. We use
+    // RenderParagraph to reduce dependencies this test has.
+    final List<RenderBox> renderBoxes = <RenderBox>[];
+    renderBoxes.add(RenderParagraph(const TextSpan(text: 'b'), textDirection: TextDirection.ltr));
+    renderBoxes.add(RenderParagraph(const TextSpan(text: 'b'), textDirection: TextDirection.ltr));
+    renderBoxes.add(RenderParagraph(const TextSpan(text: 'b'), textDirection: TextDirection.ltr));
+    renderBoxes.add(RenderParagraph(const TextSpan(text: 'b'), textDirection: TextDirection.ltr));
+    renderBoxes.add(RenderParagraph(const TextSpan(text: 'b'), textDirection: TextDirection.ltr));
+    renderBoxes.add(RenderParagraph(const TextSpan(text: 'b'), textDirection: TextDirection.ltr));
+    renderBoxes.add(RenderParagraph(const TextSpan(text: 'b'), textDirection: TextDirection.ltr));
+
+    final RenderParagraph paragraph = RenderParagraph(
+      text,
+      textDirection: TextDirection.ltr,
+      children: renderBoxes,
+    );
+    layout(paragraph, constraints: const BoxConstraints(maxWidth: 50.0));
+
+    final List<ui.TextBox> boxes = paragraph.getBoxesForSelection(
+        const TextSelection(baseOffset: 0, extentOffset: 12)
+    );
+
+    expect(boxes.length, equals(9));
+    expect(boxes[0], const TextBox.fromLTRBD(0.0, 4.0, 10.0, 14.0, TextDirection.ltr));
+    expect(boxes[1], const TextBox.fromLTRBD(10.0, 0.0, 24.0, 14.0, TextDirection.ltr));
+    expect(boxes[2], const TextBox.fromLTRBD(24.0, 0.0, 38.0, 14.0, TextDirection.ltr));
+    expect(boxes[3], const TextBox.fromLTRBD(38.0, 4.0, 48.0, 14.0, TextDirection.ltr));
+    // Wraps
+    expect(boxes[4], const TextBox.fromLTRBD(0.0, 14.0, 14.0, 28.0 , TextDirection.ltr));
+    expect(boxes[5], const TextBox.fromLTRBD(14.0, 14.0, 28.0, 28.0, TextDirection.ltr));
+    expect(boxes[6], const TextBox.fromLTRBD(28.0, 14.0, 42.0, 28.0, TextDirection.ltr));
+    // Wraps
+    expect(boxes[7], const TextBox.fromLTRBD(0.0, 28.0, 14.0, 42.0, TextDirection.ltr));
+    expect(boxes[8], const TextBox.fromLTRBD(14.0, 28.0, 28.0, 42.0 , TextDirection.ltr));
+  // Ahem-based tests don't yet quite work on Windows or some MacOS environments
+  }, skip: isWindows || isMacOS);
 }

packages/flutter/test/widgets/backdrop_filter_test.dart

@@ -10,6 +10,7 @@ import 'package:flutter/material.dart';
 
 void main() {
   testWidgets('BackdropFilter\'s cull rect does not shrink', (WidgetTester tester) async {
+    tester.binding.addTime(const Duration(seconds: 15));
     await tester.pumpWidget(
       MaterialApp(
         home: Scaffold(

packages/flutter/test/widgets/basic_test.dart

@@ -8,7 +8,6 @@ import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/rendering.dart';
 
-
 void main() {
   group('PhysicalShape', () {
     testWidgets('properties', (WidgetTester tester) async {

packages/flutter/test/widgets/editable_text_test.dart

@@ -1870,8 +1870,9 @@ void main() {
     final RenderEditable renderEditable = findRenderEditable(tester);
     // The actual text span is split into 3 parts with the middle part underlined.
     expect(renderEditable.text.children.length, 3);
-    expect(renderEditable.text.children[1].text, 'composing');
-    expect(renderEditable.text.children[1].style.decoration, TextDecoration.underline);
+    final TextSpan textSpan = renderEditable.text.children[1];
+    expect(textSpan.text, 'composing');
+    expect(textSpan.style.decoration, TextDecoration.underline);
 
     focusNode.unfocus();
     await tester.pump();

packages/flutter/test/widgets/text_test.dart

@@ -2,11 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'package:flutter/gestures.dart';
 import 'package:flutter_test/flutter_test.dart';
-import 'package:flutter/widgets.dart';
 import 'package:flutter/foundation.dart';
+import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter/widgets.dart';
 
 import '../rendering/mock_canvas.dart';
 import 'semantics_tester.dart';
@@ -294,6 +294,140 @@ void main() {
     semantics.dispose();
   }, skip: true); // TODO(jonahwilliams): correct once https://github.com/flutter/flutter/issues/20891 is resolved.
 
+  testWidgets('inline widgets generate semantic nodes', (WidgetTester tester) async {
+    final SemanticsTester semantics = SemanticsTester(tester);
+    const TextStyle textStyle = TextStyle(fontFamily: 'Ahem');
+    await tester.pumpWidget(
+      Text.rich(
+        TextSpan(
+          children: <InlineSpan>[
+            const TextSpan(text: 'a '),
+            TextSpan(text: 'pebble', recognizer: TapGestureRecognizer()..onTap = () { }),
+            const TextSpan(text: ' in the '),
+            WidgetSpan(
+              child: SizedBox(
+                width: 20,
+                height: 40,
+                child: Card(
+                  child: RichText(
+                    text: const TextSpan(text: 'INTERRUPTION'),
+                    textDirection: TextDirection.rtl,
+                  ),
+                ),
+              ),
+            ),
+            const TextSpan(text: 'sky'),
+          ],
+          style: textStyle,
+        ),
+        textDirection: TextDirection.ltr,
+      ),
+    );
+    final TestSemantics expectedSemantics = TestSemantics.root(
+      children: <TestSemantics>[
+        TestSemantics.rootChild(
+          children: <TestSemantics>[
+            TestSemantics(
+              label: 'a ',
+              textDirection: TextDirection.ltr,
+            ),
+            TestSemantics(
+              label: 'pebble',
+              textDirection: TextDirection.ltr,
+              actions: <SemanticsAction>[
+                SemanticsAction.tap,
+              ],
+            ),
+            TestSemantics(
+              label: ' in the ',
+              textDirection: TextDirection.ltr,
+            ),
+            TestSemantics(
+              label: 'INTERRUPTION',
+              textDirection: TextDirection.rtl,
+            ),
+            TestSemantics(
+              label: 'sky',
+              textDirection: TextDirection.ltr,
+            ),
+          ],
+        ),
+      ],
+    );
+    expect(semantics, hasSemantics(expectedSemantics, ignoreTransform: true, ignoreId: true, ignoreRect: true));
+    semantics.dispose();
+  });
+
+  testWidgets('inline widgets semantic nodes scale', (WidgetTester tester) async {
+    final SemanticsTester semantics = SemanticsTester(tester);
+    const TextStyle textStyle = TextStyle(fontFamily: 'Ahem');
+    await tester.pumpWidget(
+      Text.rich(
+        TextSpan(
+          children: <InlineSpan>[
+            const TextSpan(text: 'a '),
+            TextSpan(text: 'pebble', recognizer: TapGestureRecognizer()..onTap = () { }),
+            const TextSpan(text: ' in the '),
+            WidgetSpan(
+              child: SizedBox(
+                width: 20,
+                height: 40,
+                child: Card(
+                  child: RichText(
+                    text: const TextSpan(text: 'INTERRUPTION'),
+                    textDirection: TextDirection.rtl,
+                  ),
+                ),
+              ),
+            ),
+            const TextSpan(text: 'sky'),
+          ],
+          style: textStyle,
+        ),
+        textDirection: TextDirection.ltr,
+        textScaleFactor: 2,
+      ),
+    );
+    final TestSemantics expectedSemantics = TestSemantics.root(
+      children: <TestSemantics>[
+        TestSemantics.rootChild(
+          rect: const Rect.fromLTRB(0.0, 0.0, 800.0, 600.0),
+          children: <TestSemantics>[
+            TestSemantics(
+              label: 'a ',
+              textDirection: TextDirection.ltr,
+              rect: const Rect.fromLTRB(-4.0, 48.0, 60.0, 84.0),
+            ),
+            TestSemantics(
+              label: 'pebble',
+              textDirection: TextDirection.ltr,
+              actions: <SemanticsAction>[
+                SemanticsAction.tap,
+              ],
+              rect: const Rect.fromLTRB(52.0, 48.0, 228.0, 84.0),
+            ),
+            TestSemantics(
+              label: ' in the ',
+              textDirection: TextDirection.ltr,
+              rect: const Rect.fromLTRB(220.0, 48.0, 452.0, 84.0),
+            ),
+            TestSemantics(
+              label: 'INTERRUPTION',
+              textDirection: TextDirection.rtl,
+              rect: const Rect.fromLTRB(448.0, 0.0, 488.0, 80.0),
+            ),
+            TestSemantics(
+              label: 'sky',
+              textDirection: TextDirection.ltr,
+              rect: const Rect.fromLTRB(484.0, 48.0, 576.0, 84.0),
+            ),
+          ],
+        ),
+      ],
+    );
+    expect(semantics, hasSemantics(expectedSemantics, ignoreTransform: true, ignoreId: true,));
+    semantics.dispose();
+  });
 
   testWidgets('Overflow is clipping correctly - short text with overflow: clip', (WidgetTester tester) async {
     await _pumpTextWidget(

packages/flutter/test/widgets/widget_inspector_test.dart

@@ -329,7 +329,10 @@ class TestWidgetInspectorService extends Object with WidgetInspectorService {
       }
       // State type is private, hence using dynamic.
       dynamic getInspectorState() => inspectorKey.currentState;
-      String paragraphText(RenderParagraph paragraph) => paragraph.text.text;
+      String paragraphText(RenderParagraph paragraph) {
+        final TextSpan textSpan = paragraph.text;
+        return textSpan.text;
+      }
 
       await tester.pumpWidget(
         Directionality(