Expose TextHeightBehavior in Text, RichText, and DefaultTextStyle. (#48346)

packages/flutter/lib/painting.dart

@@ -17,7 +17,7 @@
 ///    painting boxes.
 library painting;
 
-export 'dart:ui' show Shadow, PlaceholderAlignment;
+export 'dart:ui' show Shadow, PlaceholderAlignment, TextHeightBehavior;
 
 export 'src/painting/alignment.dart';
 export 'src/painting/basic_types.dart';

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

@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 import 'dart:math' show min, max;
-import 'dart:ui' as ui show Paragraph, ParagraphBuilder, ParagraphConstraints, ParagraphStyle, PlaceholderAlignment, LineMetrics;
+import 'dart:ui' as ui show Paragraph, ParagraphBuilder, ParagraphConstraints, ParagraphStyle, PlaceholderAlignment, LineMetrics, TextHeightBehavior;
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
@@ -142,6 +142,7 @@ class TextPainter {
     Locale locale,
     StrutStyle strutStyle,
     TextWidthBasis textWidthBasis = TextWidthBasis.parent,
+    ui.TextHeightBehavior textHeightBehavior,
   }) : assert(text == null || text.debugAssertIsValid()),
        assert(textAlign != null),
        assert(textScaleFactor != null),
@@ -155,7 +156,8 @@ class TextPainter {
        _ellipsis = ellipsis,
        _locale = locale,
        _strutStyle = strutStyle,
-       _textWidthBasis = textWidthBasis;
+       _textWidthBasis = textWidthBasis,
+       _textHeightBehavior = textHeightBehavior;
 
   ui.Paragraph _paragraph;
   bool _needsLayout = true;
@@ -340,6 +342,16 @@ class TextPainter {
     markNeedsLayout();
   }
 
+  /// {@macro flutter.dart:ui.textHeightBehavior}
+  ui.TextHeightBehavior get textHeightBehavior => _textHeightBehavior;
+  ui.TextHeightBehavior _textHeightBehavior;
+  set textHeightBehavior(ui.TextHeightBehavior value) {
+    assert(value != null);
+    if (_textHeightBehavior == value)
+      return;
+    _textHeightBehavior = value;
+    markNeedsLayout();
+  }
 
   ui.Paragraph _layoutTemplate;
 
@@ -399,6 +411,7 @@ class TextPainter {
       textDirection: textDirection ?? defaultTextDirection,
       textScaleFactor: textScaleFactor,
       maxLines: _maxLines,
+      textHeightBehavior: _textHeightBehavior,
       ellipsis: _ellipsis,
       locale: _locale,
       strutStyle: _strutStyle,
@@ -406,6 +419,7 @@ class TextPainter {
       textAlign: textAlign,
       textDirection: textDirection ?? defaultTextDirection,
       maxLines: maxLines,
+      textHeightBehavior: _textHeightBehavior,
       ellipsis: ellipsis,
       locale: locale,
     );

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

@@ -2,7 +2,7 @@
 // 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 ParagraphStyle, TextStyle, StrutStyle, lerpDouble, Shadow, FontFeature;
+import 'dart:ui' as ui show ParagraphStyle, TextStyle, StrutStyle, lerpDouble, Shadow, FontFeature, TextHeightBehavior;
 
 import 'package:flutter/foundation.dart';
 
@@ -1067,6 +1067,7 @@ class TextStyle extends Diagnosticable {
     double textScaleFactor = 1.0,
     String ellipsis,
     int maxLines,
+    ui.TextHeightBehavior textHeightBehavior,
     Locale locale,
     String fontFamily,
     double fontSize,
@@ -1087,6 +1088,7 @@ class TextStyle extends Diagnosticable {
       fontFamily: fontFamily ?? this.fontFamily,
       fontSize: (fontSize ?? this.fontSize ?? _defaultFontSize) * textScaleFactor,
       height: height ?? this.height,
+      textHeightBehavior: textHeightBehavior,
       strutStyle: strutStyle == null ? null : ui.StrutStyle(
         fontFamily: strutStyle.fontFamily,
         fontFamilyFallback: strutStyle.fontFamilyFallback,

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

@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 import 'dart:math' as math;
-import 'dart:ui' as ui show Gradient, Shader, TextBox, PlaceholderAlignment;
+import 'dart:ui' as ui show Gradient, Shader, TextBox, PlaceholderAlignment, TextHeightBehavior;
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
@@ -72,9 +72,10 @@ class RenderParagraph extends RenderBox
     TextOverflow overflow = TextOverflow.clip,
     double textScaleFactor = 1.0,
     int maxLines,
-    TextWidthBasis textWidthBasis = TextWidthBasis.parent,
     Locale locale,
     StrutStyle strutStyle,
+    TextWidthBasis textWidthBasis = TextWidthBasis.parent,
+    ui.TextHeightBehavior textHeightBehavior,
     List<RenderBox> children,
   }) : assert(text != null),
        assert(text.debugAssertIsValid()),
@@ -97,6 +98,7 @@ class RenderParagraph extends RenderBox
          locale: locale,
          strutStyle: strutStyle,
          textWidthBasis: textWidthBasis,
+         textHeightBehavior: textHeightBehavior
        ) {
     addAll(children);
     _extractPlaceholderSpans(text);
@@ -275,6 +277,16 @@ class RenderParagraph extends RenderBox
     markNeedsLayout();
   }
 
+  /// {@macro flutter.dart:ui.textHeightBehavior}
+  ui.TextHeightBehavior get textHeightBehavior => _textPainter.textHeightBehavior;
+  set textHeightBehavior(ui.TextHeightBehavior value) {
+    if (_textPainter.textHeightBehavior == value)
+      return;
+    _textPainter.textHeightBehavior = value;
+    _overflowShader = null;
+    markNeedsLayout();
+  }
+
   @override
   double computeMinIntrinsicWidth(double height) {
     if (!_canComputeIntrinsics()) {

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

@@ -2,7 +2,7 @@
 // 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 Image, ImageFilter;
+import 'dart:ui' as ui show Image, ImageFilter, TextHeightBehavior;
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
@@ -5063,6 +5063,7 @@ class RichText extends MultiChildRenderObjectWidget {
     this.locale,
     this.strutStyle,
     this.textWidthBasis = TextWidthBasis.parent,
+    this.textHeightBehavior,
   }) : assert(text != null),
        assert(textAlign != null),
        assert(softWrap != null),
@@ -5144,6 +5145,9 @@ class RichText extends MultiChildRenderObjectWidget {
   /// {@macro flutter.widgets.text.DefaultTextStyle.textWidthBasis}
   final TextWidthBasis textWidthBasis;
 
+  /// {@macro flutter.dart:ui.textHeightBehavior}
+  final ui.TextHeightBehavior textHeightBehavior;
+
   @override
   RenderParagraph createRenderObject(BuildContext context) {
     assert(textDirection != null || debugCheckHasDirectionality(context));
@@ -5156,6 +5160,7 @@ class RichText extends MultiChildRenderObjectWidget {
       maxLines: maxLines,
       strutStyle: strutStyle,
       textWidthBasis: textWidthBasis,
+      textHeightBehavior: textHeightBehavior,
       locale: locale ?? Localizations.localeOf(context, nullOk: true),
     );
   }
@@ -5173,6 +5178,7 @@ class RichText extends MultiChildRenderObjectWidget {
       ..maxLines = maxLines
       ..strutStyle = strutStyle
       ..textWidthBasis = textWidthBasis
+      ..textHeightBehavior = textHeightBehavior
       ..locale = locale ?? Localizations.localeOf(context, nullOk: true);
   }
 

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

@@ -2,6 +2,8 @@
 // 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 TextHeightBehavior;
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/painting.dart';
 
@@ -43,6 +45,7 @@ class DefaultTextStyle extends InheritedTheme {
     this.overflow = TextOverflow.clip,
     this.maxLines,
     this.textWidthBasis = TextWidthBasis.parent,
+    this.textHeightBehavior,
     @required Widget child,
   }) : assert(style != null),
        assert(softWrap != null),
@@ -65,6 +68,7 @@ class DefaultTextStyle extends InheritedTheme {
       maxLines = null,
       overflow = TextOverflow.clip,
       textWidthBasis = TextWidthBasis.parent,
+      textHeightBehavior = null,
       super(key: key, child: null);
 
   /// Creates a default text style that overrides the text styles in scope at
@@ -141,6 +145,9 @@ class DefaultTextStyle extends InheritedTheme {
   /// See [TextWidthBasis] for possible values and their implications.
   final TextWidthBasis textWidthBasis;
 
+  /// {@macro flutter.dart:ui.textHeightBehavior}
+  final ui.TextHeightBehavior textHeightBehavior;
+
   /// The closest instance of this class that encloses the given context.
   ///
   /// If no such instance exists, returns an instance created by
@@ -162,7 +169,8 @@ class DefaultTextStyle extends InheritedTheme {
         softWrap != oldWidget.softWrap ||
         overflow != oldWidget.overflow ||
         maxLines != oldWidget.maxLines ||
-        textWidthBasis != oldWidget.textWidthBasis;
+        textWidthBasis != oldWidget.textWidthBasis ||
+        textHeightBehavior != oldWidget.textHeightBehavior;
   }
 
   @override
@@ -175,6 +183,7 @@ class DefaultTextStyle extends InheritedTheme {
       overflow: overflow,
       maxLines: maxLines,
       textWidthBasis: textWidthBasis,
+      textHeightBehavior: textHeightBehavior,
       child: child,
     );
   }
@@ -188,6 +197,7 @@ class DefaultTextStyle extends InheritedTheme {
     properties.add(EnumProperty<TextOverflow>('overflow', overflow, defaultValue: null));
     properties.add(IntProperty('maxLines', maxLines, defaultValue: null));
     properties.add(EnumProperty<TextWidthBasis>('textWidthBasis', textWidthBasis, defaultValue: TextWidthBasis.parent));
+    properties.add(DiagnosticsProperty<ui.TextHeightBehavior>('textHeightBehavior', textHeightBehavior, defaultValue: null));
   }
 }
 
@@ -283,6 +293,7 @@ class Text extends StatelessWidget {
     this.maxLines,
     this.semanticsLabel,
     this.textWidthBasis,
+    this.textHeightBehavior,
   }) : assert(
          data != null,
          'A non-null String must be provided to a Text widget.',
@@ -314,6 +325,7 @@ class Text extends StatelessWidget {
     this.maxLines,
     this.semanticsLabel,
     this.textWidthBasis,
+    this.textHeightBehavior,
   }) : assert(
          textSpan != null,
          'A non-null TextSpan must be provided to a Text.rich widget.',
@@ -416,6 +428,9 @@ class Text extends StatelessWidget {
   /// {@macro flutter.painting.textPainter.textWidthBasis}
   final TextWidthBasis textWidthBasis;
 
+  /// {@macro flutter.dart:ui.textHeightBehavior}
+  final ui.TextHeightBehavior textHeightBehavior;
+
   @override
   Widget build(BuildContext context) {
     final DefaultTextStyle defaultTextStyle = DefaultTextStyle.of(context);
@@ -434,6 +449,7 @@ class Text extends StatelessWidget {
       maxLines: maxLines ?? defaultTextStyle.maxLines,
       strutStyle: strutStyle,
       textWidthBasis: textWidthBasis ?? defaultTextStyle.textWidthBasis,
+      textHeightBehavior: textHeightBehavior ?? defaultTextStyle.textHeightBehavior,
       text: TextSpan(
         style: effectiveTextStyle,
         text: data,
@@ -467,6 +483,8 @@ class Text extends StatelessWidget {
     properties.add(EnumProperty<TextOverflow>('overflow', overflow, defaultValue: null));
     properties.add(DoubleProperty('textScaleFactor', textScaleFactor, defaultValue: null));
     properties.add(IntProperty('maxLines', maxLines, defaultValue: null));
+    properties.add(EnumProperty<TextWidthBasis>('textWidthBasis', textWidthBasis, defaultValue: null));
+    properties.add(DiagnosticsProperty<ui.TextHeightBehavior>('textHeightBehavior', textHeightBehavior, defaultValue: null));
     if (semanticsLabel != null) {
       properties.add(StringProperty('semanticsLabel', semanticsLabel));
     }

packages/flutter/test/material/theme_test.dart

@@ -829,6 +829,7 @@ class _TextStyleProxy implements TextStyle {
     double textScaleFactor = 1.0,
     String ellipsis,
     int maxLines,
+    ui.TextHeightBehavior textHeightBehavior,
     Locale locale,
     String fontFamily,
     double fontSize,

packages/flutter/test/widgets/text_golden_test.dart

@@ -1316,4 +1316,47 @@ void main() {
       matchesGoldenFile('text_golden.TextInlineWidgetMiddle.1.png'),
     );
   });
+
+  testWidgets('Text TextHeightBehavior', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      Center(
+        child: RepaintBoundary(
+          child: Container(
+            width: 200.0,
+            height: 700.0,
+            decoration: const BoxDecoration(
+              color: Color(0xff00ff00),
+            ),
+            child: Column(
+              children: const <Widget>[
+                Text('Hello\nLine 2\nLine 3',
+                  textDirection: TextDirection.ltr,
+                  style: TextStyle(height: 5,),
+                ),
+                Text('Hello\nLine 2\nLine 3',
+                  textDirection: TextDirection.ltr,
+                  style: TextStyle(height: 5,),
+                  textHeightBehavior: TextHeightBehavior(
+                    applyHeightToFirstAscent: false,
+                    applyHeightToLastDescent: false,
+                  ),
+                ),
+                Text('Hello',
+                  textDirection: TextDirection.ltr,
+                  style: TextStyle(height: 5,),
+                  textHeightBehavior: TextHeightBehavior(
+                    applyHeightToFirstAscent: false,
+                  ),
+                ),
+              ],
+            ),
+          ),
+        ),
+      ),
+    );
+    await expectLater(
+      find.byType(Container),
+      matchesGoldenFile('text_golden.TextHeightBehavior.1.png'),
+    );
+  });
 }