Invalidate the TextPainter line metrics cache when redoing text layout (#97446)

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

@@ -648,7 +648,8 @@ class TextPainter {
       _createParagraph();
     _lastMinWidth = minWidth;
     _lastMaxWidth = maxWidth;
-    // A change in layout invalidates the cached caret metrics as well.
+    // A change in layout invalidates the cached caret and line metrics as well.
+    _lineMetricsCache = null;
     _previousCaretPosition = null;
     _previousCaretPrototype = null;
     _layoutParagraph(minWidth, maxWidth);

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

@@ -2416,7 +2416,7 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin,
     // ui.LineMetrics, then we can get rid of this.
     final Offset offset = _textPainter.getOffsetForCaret(startPosition, Rect.zero);
     for (final ui.LineMetrics lineMetrics in metrics) {
-      if (lineMetrics.baseline + lineMetrics.descent > offset.dy) {
+      if (lineMetrics.baseline > offset.dy) {
         return MapEntry<int, Offset>(lineMetrics.lineNumber, Offset(offset.dx, lineMetrics.baseline));
       }
     }

packages/flutter/test/painting/text_painter_test.dart

@@ -996,6 +996,26 @@ void main() {
         ui.Rect.zero);
     expect(caretOffset.dx, painter.width);
   }, skip: kIsWeb && !isCanvasKit); // https://github.com/flutter/flutter/issues/87545
+
+  test('TextPainter line metrics update after layout', () {
+    final TextPainter painter = TextPainter()
+      ..textDirection = TextDirection.ltr;
+
+    const String text = 'word1 word2 word3';
+    painter.text = const TextSpan(
+      text: text,
+    );
+
+    painter.layout(maxWidth: 80);
+
+    List<ui.LineMetrics> lines = painter.computeLineMetrics();
+    expect(lines.length, 3);
+
+    painter.layout(maxWidth: 1000);
+
+    lines = painter.computeLineMetrics();
+    expect(lines.length, 1);
+  }, skip: kIsWeb && !isCanvasKit); // https://github.com/flutter/flutter/issues/62819
 }
 
 class MockCanvas extends Fake implements Canvas {