Use strut box heights to calculate selection rectangles in order to ensure...

Use strut box heights to calculate selection rectangles in order to ensure that they remain within visible bounds (#50354)

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

@@ -591,7 +591,7 @@ class _SelectableTextState extends State<SelectableText> with AutomaticKeepAlive
         showCursor: widget.showCursor,
         controller: _controller,
         focusNode: focusNode,
-        strutStyle: widget.strutStyle ?? StrutStyle.disabled,
+        strutStyle: widget.strutStyle ?? const StrutStyle(),
         textAlign: widget.textAlign ?? defaultTextStyle.textAlign ?? TextAlign.start,
         textDirection: widget.textDirection,
         textScaleFactor: widget.textScaleFactor,

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

@@ -641,7 +641,9 @@ class TextPainter {
     List<TextBox> boxes = <TextBox>[];
     while (boxes.isEmpty && flattenedText != null) {
       final int prevRuneOffset = offset - graphemeClusterLength;
-      boxes = _paragraph.getBoxesForRange(prevRuneOffset, offset);
+      // Use BoxHeightStyle.strut to ensure that the caret's height fits within
+      // the line's height and is consistent throughout the line.
+      boxes = _paragraph.getBoxesForRange(prevRuneOffset, offset, boxHeightStyle: ui.BoxHeightStyle.strut);
       // When the range does not include a full cluster, no boxes will be returned.
       if (boxes.isEmpty) {
         // When we are at the beginning of the line, a non-surrogate position will
@@ -690,7 +692,9 @@ class TextPainter {
     List<TextBox> boxes = <TextBox>[];
     while (boxes.isEmpty && flattenedText != null) {
       final int nextRuneOffset = offset + graphemeClusterLength;
-      boxes = _paragraph.getBoxesForRange(offset, nextRuneOffset);
+      // Use BoxHeightStyle.strut to ensure that the caret's height fits within
+      // the line's height and is consistent throughout the line.
+      boxes = _paragraph.getBoxesForRange(offset, nextRuneOffset, boxHeightStyle: ui.BoxHeightStyle.strut);
       // When the range does not include a full cluster, no boxes will be returned.
       if (boxes.isEmpty) {
         // When we are at the end of the line, a non-surrogate position will

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

@@ -564,7 +564,7 @@ class EditableText extends StatefulWidget {
   /// [TextStyle] instead. See [StrutStyle.inheritFromTextStyle].
   StrutStyle get strutStyle {
     if (_strutStyle == null) {
-      return style != null ? StrutStyle.fromTextStyle(style, forceStrutHeight: true) : StrutStyle.disabled;
+      return style != null ? StrutStyle.fromTextStyle(style, forceStrutHeight: true) : const StrutStyle();
     }
     return _strutStyle.inheritFromTextStyle(style);
   }

packages/flutter/test/cupertino/text_field_test.dart

@@ -4028,7 +4028,8 @@ void main() {
 
     await tester.longPressAt(textfieldStart + const Offset(50.0, 2.0));
     await tester.pump(const Duration(milliseconds: 150));
-    await tester.tapAt(textfieldStart + const Offset(20.0, 146.0));
+    // Tap the Select All button.
+    await tester.tapAt(textfieldStart + const Offset(20.0, 100.0));
     await tester.pump(const Duration(milliseconds: 300));
 
     await expectLater(
@@ -4074,7 +4075,8 @@ void main() {
 
     await tester.longPressAt(textfieldStart + const Offset(50.0, 2.0));
     await tester.pump(const Duration(milliseconds: 150));
-    await tester.tapAt(textfieldStart + const Offset(20.0, 146.0));
+    // Tap the Select All button.
+    await tester.tapAt(textfieldStart + const Offset(20.0, 100.0));
     await tester.pump(const Duration(milliseconds: 300));
 
     await expectLater(

packages/flutter/test/material/text_field_test.dart

@@ -2352,7 +2352,6 @@ void main() {
           controller: controller,
           style: const TextStyle(color: Colors.black, fontSize: 34.0),
           maxLines: 3,
-          strutStyle: StrutStyle.disabled,
         ),
       ),
     );
@@ -3740,7 +3739,6 @@ void main() {
               child: TextField(
                 controller: controller,
                 maxLines: 3,
-                strutStyle: StrutStyle.disabled,
               ),
             ),
           ),

packages/flutter/test/painting/text_painter_test.dart

@@ -4,6 +4,7 @@
 
 import 'dart:ui' as ui;
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/painting.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -816,4 +817,20 @@ void main() {
   // issue or similar. See https://github.com/flutter/flutter/issues/43763
   // for more info.
   }, skip: true);
+
+  test('TextPainter caret height and line height', () {
+    final TextPainter painter = TextPainter()
+      ..textDirection = TextDirection.ltr
+      ..strutStyle = const StrutStyle(fontSize: 50.0);
+
+    const String text = 'A';
+    painter.text = const TextSpan(text: text, style: TextStyle(height: 1.0));
+    painter.layout();
+
+    final double caretHeight = painter.getFullHeightForCaret(
+      const ui.TextPosition(offset: 0),
+      ui.Rect.zero,
+    );
+    expect(caretHeight, 50.0);
+  }, skip: kIsWeb);
 }

packages/flutter/test/widgets/editable_text_cursor_test.dart

@@ -658,7 +658,6 @@ void main() {
               controller: controller,
               focusNode: focusNode,
               style: textStyle,
-              strutStyle: StrutStyle.disabled,
             ),
           ),
         ),

packages/flutter/test/widgets/selectable_text_test.dart

@@ -995,7 +995,6 @@ void main() {
           dragStartBehavior: DragStartBehavior.down,
           style: TextStyle(color: Colors.black, fontSize: 34.0),
           maxLines: 3,
-          strutStyle: StrutStyle.disabled,
         ),
       ),
     );
@@ -1316,7 +1315,6 @@ void main() {
               child: SelectableText(
                 text,
                 maxLines: 3,
-                strutStyle: StrutStyle.disabled,
               ),
             ),
           ),