Fix error cursor position for left and right arrow event after text selection (#68402)

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

@@ -676,14 +676,24 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin {
         }
       } else {
         if (rightArrow && newSelection.extentOffset < _plainText.length) {
-          final int nextExtent = nextCharacter(newSelection.extentOffset, _plainText);
+          int nextExtent;
+          if (!shift && !wordModifier && !lineModifier && newSelection.start != newSelection.end) {
+            nextExtent = newSelection.end;
+          } else {
+            nextExtent = nextCharacter(newSelection.extentOffset, _plainText);
+          }
           final int distance = nextExtent - newSelection.extentOffset;
           newSelection = newSelection.copyWith(extentOffset: nextExtent);
           if (shift) {
             _cursorResetLocation += distance;
           }
         } else if (leftArrow && newSelection.extentOffset > 0) {
-          final int previousExtent = previousCharacter(newSelection.extentOffset, _plainText);
+          int previousExtent;
+          if (!shift && !wordModifier && !lineModifier && newSelection.start != newSelection.end) {
+            previousExtent = newSelection.start;
+          } else {
+            previousExtent = previousCharacter(newSelection.extentOffset, _plainText);
+          }
           final int distance = newSelection.extentOffset - previousExtent;
           newSelection = newSelection.copyWith(extentOffset: previousExtent);
           if (shift) {

packages/flutter/test/material/text_field_test.dart

@@ -4331,7 +4331,7 @@ void main() {
     await tester.sendKeyUpEvent(LogicalKeyboardKey.controlRight);
     await tester.pumpAndSettle();
 
-    const String expected = 'a big a bighouse\njumped over a mouse';
+    const String expected = 'a biga big house\njumped over a mouse';
     expect(find.text(expected), findsOneWidget, reason: 'Because text contains ${controller.text}');
   });
 

packages/flutter/test/rendering/editable_test.dart

@@ -935,6 +935,68 @@ void main() {
     expect(delegate.textEditingValue.text, '');
   }, skip: isBrowser); // https://github.com/flutter/flutter/issues/61021
 
+  test('arrow keys with selection text', () async {
+    final TextSelectionDelegate delegate = FakeEditableTextState();
+    final ViewportOffset viewportOffset = ViewportOffset.zero();
+    late TextSelection currentSelection;
+    final RenderEditable editable = RenderEditable(
+      backgroundCursorColor: Colors.grey,
+      selectionColor: Colors.black,
+      textDirection: TextDirection.ltr,
+      cursorColor: Colors.red,
+      offset: viewportOffset,
+      textSelectionDelegate: delegate,
+      onSelectionChanged: (TextSelection selection, RenderEditable renderObject, SelectionChangedCause cause) {
+        currentSelection = selection;
+      },
+      startHandleLayerLink: LayerLink(),
+      endHandleLayerLink: LayerLink(),
+      text: const TextSpan(
+        text: '012345',  // Thumbs up
+        style: TextStyle(height: 1.0, fontSize: 10.0, fontFamily: 'Ahem'),
+      ),
+      selection: const TextSelection.collapsed(
+        offset: 0,
+      ),
+    );
+
+    layout(editable);
+    editable.hasFocus = true;
+
+    editable.selection = const TextSelection(baseOffset: 2, extentOffset: 4);
+    pumpFrame();
+
+    await simulateKeyDownEvent(LogicalKeyboardKey.arrowRight);
+    await simulateKeyUpEvent(LogicalKeyboardKey.arrowRight);
+    expect(currentSelection.isCollapsed, true);
+    expect(currentSelection.baseOffset, 4);
+
+    editable.selection = const TextSelection(baseOffset: 4, extentOffset: 2);
+    pumpFrame();
+
+    await simulateKeyDownEvent(LogicalKeyboardKey.arrowRight);
+    await simulateKeyUpEvent(LogicalKeyboardKey.arrowRight);
+    expect(currentSelection.isCollapsed, true);
+    expect(currentSelection.baseOffset, 4);
+
+    editable.selection = const TextSelection(baseOffset: 2, extentOffset: 4);
+    pumpFrame();
+
+    await simulateKeyDownEvent(LogicalKeyboardKey.arrowLeft);
+    await simulateKeyUpEvent(LogicalKeyboardKey.arrowLeft);
+    expect(currentSelection.isCollapsed, true);
+    expect(currentSelection.baseOffset, 2);
+
+    editable.selection = const TextSelection(baseOffset: 4, extentOffset: 2);
+    pumpFrame();
+
+    await simulateKeyDownEvent(LogicalKeyboardKey.arrowLeft);
+    await simulateKeyUpEvent(LogicalKeyboardKey.arrowLeft);
+    expect(currentSelection.isCollapsed, true);
+    expect(currentSelection.baseOffset, 2);
+
+  }, skip: isBrowser); // https://github.com/flutter/flutter/issues/58068
+
   test('getEndpointsForSelection handles empty characters', () {
     final TextSelectionDelegate delegate = FakeEditableTextState();
     final RenderEditable editable = RenderEditable(

packages/flutter/test/widgets/editable_text_test.dart

@@ -3989,7 +3989,6 @@ void main() {
       reason: 'on $platform',
     );
 
-    // Move forward one character to reset the selection.
     await sendKeys(
       tester,
       <LogicalKeyboardKey>[
@@ -4002,8 +4001,8 @@ void main() {
       selection,
       equals(
         const TextSelection(
-          baseOffset: 21,
-          extentOffset: 21,
+          baseOffset: 20,
+          extentOffset: 20,
           affinity: TextAffinity.downstream,
         ),
       ),
@@ -4024,8 +4023,8 @@ void main() {
       selection,
       equals(
         const TextSelection(
-          baseOffset: 21,
-          extentOffset: 40,
+          baseOffset: 20,
+          extentOffset: 39,
           affinity: TextAffinity.downstream,
         ),
       ),
@@ -4049,7 +4048,7 @@ void main() {
       selection,
       equals(
         const TextSelection(
-          baseOffset: 21,
+          baseOffset: 20,
           extentOffset: testText.length,
           affinity: TextAffinity.downstream,
         ),
@@ -4071,8 +4070,8 @@ void main() {
       selection,
       equals(
         const TextSelection(
-          baseOffset: 21,
-          extentOffset: 58,
+          baseOffset: 20,
+          extentOffset: 57,
           affinity: TextAffinity.downstream,
         ),
       ),
@@ -4094,7 +4093,7 @@ void main() {
       selection,
       equals(
         const TextSelection(
-          baseOffset: 21,
+          baseOffset: 20,
           extentOffset: 72,
           affinity: TextAffinity.downstream,
         ),
@@ -4117,7 +4116,7 @@ void main() {
       selection,
       equals(
         const TextSelection(
-          baseOffset: 21,
+          baseOffset: 20,
           extentOffset: 55,
           affinity: TextAffinity.downstream,
         ),