[Line Heights] Add textHeightBehavior to SelectableText. (#58530)

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

@@ -221,6 +221,7 @@ class SelectableText extends StatefulWidget {
     this.enableInteractiveSelection = true,
     this.onTap,
     this.scrollPhysics,
+    this.textHeightBehavior,
     this.textWidthBasis,
   }) :  assert(showCursor != null),
         assert(autofocus != null),
@@ -270,6 +271,7 @@ class SelectableText extends StatefulWidget {
     this.enableInteractiveSelection = true,
     this.onTap,
     this.scrollPhysics,
+    this.textHeightBehavior,
     this.textWidthBasis,
   }) :  assert(showCursor != null),
     assert(autofocus != null),
@@ -406,6 +408,9 @@ class SelectableText extends StatefulWidget {
   /// {@macro flutter.widgets.editableText.scrollPhysics}
   final ScrollPhysics scrollPhysics;
 
+  /// {@macro flutter.dart:ui.textHeightBehavior}
+  final TextHeightBehavior textHeightBehavior;
+
   /// {@macro flutter.painting.textPainter.textWidthBasis}
   final TextWidthBasis textWidthBasis;
 
@@ -430,6 +435,7 @@ class SelectableText extends StatefulWidget {
     properties.add(DiagnosticsProperty<Color>('cursorColor', cursorColor, defaultValue: null));
     properties.add(FlagProperty('selectionEnabled', value: selectionEnabled, defaultValue: true, ifFalse: 'selection disabled'));
     properties.add(DiagnosticsProperty<ScrollPhysics>('scrollPhysics', scrollPhysics, defaultValue: null));
+    properties.add(DiagnosticsProperty<TextHeightBehavior>('textHeightBehavior', textHeightBehavior, defaultValue: null));
   }
 }
 
@@ -598,6 +604,7 @@ class _SelectableTextState extends State<SelectableText> with AutomaticKeepAlive
         style: effectiveTextStyle,
         readOnly: true,
         textWidthBasis: widget.textWidthBasis ?? defaultTextStyle.textWidthBasis,
+        textHeightBehavior: widget.textHeightBehavior ?? defaultTextStyle.textHeightBehavior,
         showSelectionHandles: _showSelectionHandles,
         showCursor: widget.showCursor,
         controller: _controller,

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

@@ -212,6 +212,7 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin {
     this.ignorePointer = false,
     bool readOnly = false,
     bool forceLine = true,
+    TextHeightBehavior textHeightBehavior,
     TextWidthBasis textWidthBasis = TextWidthBasis.parent,
     String obscuringCharacter = '•',
     bool obscureText = false,
@@ -264,6 +265,7 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin {
          textScaleFactor: textScaleFactor,
          locale: locale,
          strutStyle: strutStyle,
+         textHeightBehavior: textHeightBehavior,
          textWidthBasis: textWidthBasis,
        ),
        _cursorColor = cursorColor,
@@ -322,6 +324,15 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin {
   /// The default value of this property is false.
   bool ignorePointer;
 
+  /// {@macro flutter.dart:ui.textHeightBehavior}
+  TextHeightBehavior get textHeightBehavior => _textPainter.textHeightBehavior;
+  set textHeightBehavior(TextHeightBehavior value) {
+    if (_textPainter.textHeightBehavior == value)
+      return;
+    _textPainter.textHeightBehavior = value;
+    markNeedsTextLayout();
+  }
+
   /// {@macro flutter.widgets.text.DefaultTextStyle.textWidthBasis}
   TextWidthBasis get textWidthBasis => _textPainter.textWidthBasis;
   set textWidthBasis(TextWidthBasis value) {

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

@@ -375,6 +375,7 @@ class EditableText extends StatefulWidget {
     this.minLines,
     this.expands = false,
     this.forceLine = true,
+    this.textHeightBehavior,
     this.textWidthBasis = TextWidthBasis.parent,
     this.autofocus = false,
     bool showCursor,
@@ -486,6 +487,9 @@ class EditableText extends StatefulWidget {
   /// {@endtemplate}
   final bool obscureText;
 
+  /// {@macro flutter.dart:ui.textHeightBehavior},
+  final TextHeightBehavior textHeightBehavior;
+
   /// {@macro flutter.widgets.text.DefaultTextStyle.textWidthBasis}
   final TextWidthBasis textWidthBasis;
 
@@ -1146,6 +1150,7 @@ class EditableText extends StatefulWidget {
     properties.add(DiagnosticsProperty<ScrollController>('scrollController', scrollController, defaultValue: null));
     properties.add(DiagnosticsProperty<ScrollPhysics>('scrollPhysics', scrollPhysics, defaultValue: null));
     properties.add(DiagnosticsProperty<Iterable<String>>('autofillHints', autofillHints, defaultValue: null));
+    properties.add(DiagnosticsProperty<TextHeightBehavior>('textHeightBehavior', textHeightBehavior, defaultValue: null));
   }
 }
 
@@ -2085,6 +2090,7 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
                 textAlign: widget.textAlign,
                 textDirection: _textDirection,
                 locale: widget.locale,
+                textHeightBehavior: widget.textHeightBehavior,
                 textWidthBasis: widget.textWidthBasis,
                 obscuringCharacter: widget.obscuringCharacter,
                 obscureText: widget.obscureText,
@@ -2149,6 +2155,7 @@ class _Editable extends LeafRenderObjectWidget {
     this.showCursor,
     this.forceLine,
     this.readOnly,
+    this.textHeightBehavior,
     this.textWidthBasis,
     this.hasFocus,
     this.maxLines,
@@ -2206,6 +2213,7 @@ class _Editable extends LeafRenderObjectWidget {
   final Locale locale;
   final String obscuringCharacter;
   final bool obscureText;
+  final TextHeightBehavior textHeightBehavior;
   final TextWidthBasis textWidthBasis;
   final bool autocorrect;
   final SmartDashesType smartDashesType;
@@ -2255,6 +2263,7 @@ class _Editable extends LeafRenderObjectWidget {
       ignorePointer: rendererIgnoresPointer,
       obscuringCharacter: obscuringCharacter,
       obscureText: obscureText,
+      textHeightBehavior: textHeightBehavior,
       textWidthBasis: textWidthBasis,
       cursorWidth: cursorWidth,
       cursorRadius: cursorRadius,
@@ -2295,6 +2304,7 @@ class _Editable extends LeafRenderObjectWidget {
       ..onSelectionChanged = onSelectionChanged
       ..onCaretChanged = onCaretChanged
       ..ignorePointer = rendererIgnoresPointer
+      ..textHeightBehavior = textHeightBehavior
       ..textWidthBasis = textWidthBasis
       ..obscuringCharacter = obscuringCharacter
       ..obscureText = obscureText

packages/flutter/test/widgets/selectable_text_test.dart

@@ -374,6 +374,30 @@ void main() {
     expect(textBox.size, const Size(633.0, 28.0));
   });
 
+  testWidgets('can switch between textHeightBehavior', (WidgetTester tester) async {
+    const String text = 'selectable text';
+    const TextHeightBehavior textHeightBehavior = TextHeightBehavior(
+      applyHeightToFirstAscent: false,
+      applyHeightToLastDescent: false,
+    );
+    await tester.pumpWidget(
+      boilerplate(
+        child: const SelectableText(text),
+      ),
+    );
+    expect(findRenderEditable(tester).textHeightBehavior, isNull);
+
+    await tester.pumpWidget(
+      boilerplate(
+        child: const SelectableText(
+          text,
+          textHeightBehavior: textHeightBehavior,
+        ),
+      ),
+    );
+    expect(findRenderEditable(tester).textHeightBehavior, textHeightBehavior);
+  });
+
   testWidgets('Cursor blinks when showCursor is true', (WidgetTester tester) async {
     await tester.pumpWidget(
       overlay(