Cherry Pick: [SuperTextField][iOS] Fix selection highlight (Resolves #2346) (#2486)

Author: github-actions[bot]

super_editor/lib/src/super_textfield/ios/ios_textfield.dart

@@ -629,17 +629,17 @@ class SuperIOSTextFieldState extends State<SuperIOSTextField>
         return Stack(
           clipBehavior: Clip.none,
           children: [
-            if (widget.textController?.selection.isValid == true)
+            if (_textEditingController.selection.isValid == true)
               // Selection highlight beneath the text.
               TextLayoutSelectionHighlight(
                 textLayout: textLayout,
                 style: SelectionHighlightStyle(
                   color: widget.selectionColor,
                 ),
-                selection: widget.textController?.selection,
+                selection: _textEditingController.selection,
               ),
             // Underline beneath the composing region.
-            if (widget.textController?.composingRegion.isValid == true && widget.showComposingUnderline)
+            if (_textEditingController.composingRegion.isValid == true && widget.showComposingUnderline)
               TextUnderlineLayer(
                 textLayout: textLayout,
                 style: StraightUnderlineStyle(
@@ -648,7 +648,7 @@ class SuperIOSTextFieldState extends State<SuperIOSTextField>
                 ),
                 underlines: [
                   TextLayoutUnderline(
-                    range: widget.textController!.composingRegion,
+                    range: _textEditingController.composingRegion,
                   ),
                 ],
               ),

super_editor/test/super_textfield/ios/super_textfield_ios_selection_test.dart

@@ -4,7 +4,9 @@ import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter_test_runners/flutter_test_runners.dart';
 import 'package:super_editor/src/infrastructure/platforms/ios/toolbar.dart';
+import 'package:super_editor/super_editor_test.dart';
 import 'package:super_editor/super_text_field.dart';
+import 'package:super_text_layout/super_text_layout.dart';
 
 import '../super_textfield_inspector.dart';
 import '../super_textfield_robot.dart';
@@ -108,6 +110,41 @@ void main() {
       // Ensure that the text field toolbar is visible.
       expect(find.byType(IOSTextEditingFloatingToolbar), findsOneWidget);
     });
+
+    testWidgetsOnIos('displays selection highlight when controller is not provided', (tester) async {
+      // Pump a tree with a SuperIOSTextField without providing it a controller to make sure
+      // SuperIOSTextField does not rely on the provided controller to show the selection highlight.
+      //
+      // See https://github.com/superlistapp/super_editor/issues/2346 for details.
+      await tester.pumpWidget(
+        MaterialApp(
+          home: Scaffold(
+            body: ConstrainedBox(
+              constraints: const BoxConstraints(minWidth: 300),
+              child: const SuperIOSTextField(
+                padding: EdgeInsets.all(12),
+                caretStyle: CaretStyle(color: Colors.red),
+                selectionColor: defaultSelectionColor,
+                handlesColor: Colors.red,
+                textStyleBuilder: defaultTextFieldStyleBuilder,
+              ),
+            ),
+          ),
+        ),
+      );
+
+      // Place the caret at the beginning of the text.
+      await tester.placeCaretInSuperTextField(0, find.byType(SuperIOSTextField));
+
+      // Type some text.
+      await tester.typeImeText('This is some text');
+
+      // Double tap to select the word "some".
+      await tester.doubleTapAtSuperTextField(10, find.byType(SuperIOSTextField));
+
+      // Ensure the selection highlight is displayed.
+      expect(find.byType(TextLayoutSelectionHighlight), findsOneWidget);
+    });
   });
 }