Remove strut migration flag from `TextPainter` (#144242)

Fixes https://github.com/flutter/flutter/issues/142969.

G3fix: cl/610790040

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

@@ -683,12 +683,6 @@ class TextPainter {
     }
   }
 
-  @Deprecated(  // flutter_ignore: deprecation_syntax (see analyze.dart)
-    'The disableStrutHalfLeading flag is for internal migration purposes only and should not be used.'
-  )
-  /// Migration only flag, do not use.
-  static bool disableStrutHalfLeading = true;
-
   // Whether textWidthBasis has changed after the most recent `layout` call.
   bool _debugNeedsRelayout = true;
   // The result of the most recent `layout` call.
@@ -1024,25 +1018,6 @@ class TextPainter {
   ui.ParagraphStyle _createParagraphStyle([ TextAlign? textAlignOverride ]) {
     assert(textDirection != null, 'TextPainter.textDirection must be set to a non-null value before using the TextPainter.');
     final TextStyle baseStyle = _text?.style ?? const TextStyle();
-    final StrutStyle? strutStyle = _strutStyle;
-
-    final bool applyMigration = !kIsWeb && TextPainter.disableStrutHalfLeading
-                             && strutStyle != null && (strutStyle.forceStrutHeight ?? false)
-                             && strutStyle.leadingDistribution == TextLeadingDistribution.even;
-    final StrutStyle? strutStyleForMigration = !applyMigration
-      ? strutStyle
-      : StrutStyle(
-        fontFamily: strutStyle.fontFamily,
-        fontFamilyFallback: strutStyle.fontFamilyFallback,
-        fontSize: strutStyle.fontSize,
-        height: strutStyle.height,
-        leadingDistribution: TextLeadingDistribution.proportional,
-        leading: strutStyle.leading,
-        fontWeight: strutStyle.fontWeight,
-        fontStyle: strutStyle.fontStyle,
-        forceStrutHeight: strutStyle.forceStrutHeight,
-      );
-
     return baseStyle.getParagraphStyle(
       textAlign: textAlignOverride ?? textAlign,
       textDirection: textDirection,
@@ -1051,7 +1026,7 @@ class TextPainter {
       textHeightBehavior: _textHeightBehavior,
       ellipsis: _ellipsis,
       locale: _locale,
-      strutStyle: strutStyleForMigration,
+      strutStyle: _strutStyle,
     );
   }
 

packages/flutter/test/painting/text_painter_test.dart

@@ -1632,7 +1632,7 @@ void main() {
       expect(painter.computeDistanceToActualBaseline(TextBaseline.alphabetic), 10 + 10 * 7.5);
     });
 
-    test('force strut height', () {
+    test('strut no half leading + force strut height', () {
       const StrutStyle strut = StrutStyle(height: 10, fontSize: 10, forceStrutHeight: true);
       final TextPainter painter = TextPainter(
         textDirection: TextDirection.ltr,
@@ -1646,6 +1646,34 @@ void main() {
         const <ui.TextBox>[TextBox.fromLTRBD(0, baseline - 15, 20, baseline + 5, TextDirection.ltr)],
       );
     });
+
+    test('strut half leading + force strut height', () {
+      const StrutStyle strut = StrutStyle(height: 10, fontSize: 10, forceStrutHeight: true, leadingDistribution: TextLeadingDistribution.even);
+      final TextPainter painter = TextPainter(
+        textDirection: TextDirection.ltr,
+        text: const TextSpan(text: 'A', style: TextStyle(fontSize: 20)),
+        strutStyle: strut,
+      )..layout();
+      expect(painter.height, 100);
+      const double baseline = 45 + 7.5;
+      expect(
+        painter.getBoxesForSelection(const TextSelection(baseOffset: 0, extentOffset: 1)),
+        const <ui.TextBox>[TextBox.fromLTRBD(0, baseline - 15, 20, baseline + 5, TextDirection.ltr)],
+      );
+    });
+
+   test('force strut height applies to widget spans', () {
+      const Size placeholderSize = Size(1000, 1000);
+      const StrutStyle strut = StrutStyle(height: 10, fontSize: 10, forceStrutHeight: true);
+      final TextPainter painter = TextPainter(
+        textDirection: TextDirection.ltr,
+        text: const WidgetSpan(child: SizedBox()),
+        strutStyle: strut,
+      )
+      ..setPlaceholderDimensions(const <PlaceholderDimensions>[PlaceholderDimensions(size: placeholderSize, alignment: PlaceholderAlignment.bottom)])
+      ..layout();
+      expect(painter.height, 100);
+    });
   }, skip: kIsWeb && !isCanvasKit); // [intended] strut spport for HTML renderer https://github.com/flutter/flutter/issues/32243.
 
   test('TextPainter dispatches memory events', () async {