Don't respond to the insertionPointColor selector on iOS 17+ (#46373)

Fixes flutter/flutter#132548

[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style

Author: LongCatIsLooong

shell/platform/darwin/ios/framework/Source/FlutterTextInputPlugin.mm

@@ -902,7 +902,14 @@ - (UITextContentType)textContentType {
 
 // Prevent UIKit from showing selection handles or highlights. This is needed
 // because Scribble interactions require the view to have it's actual frame on
-// the screen.
+// the screen. They're not needed on iOS 17 with the new
+// UITextSelectionDisplayInteraction API.
+//
+// These are undocumented methods. On iOS 17, the insertion point color is also
+// used as the highlighted background of the selected IME candidate:
+// https://github.com/flutter/flutter/issues/132548
+// So the respondsToSelector method is overridden to return NO for this method
+// on iOS 17+.
 - (UIColor*)insertionPointColor {
   return [UIColor clearColor];
 }
@@ -930,6 +937,16 @@ - (UIInputViewController*)inputViewController {
   return _textInputPlugin.textInputDelegate;
 }
 
+- (BOOL)respondsToSelector:(SEL)selector {
+  if (@available(iOS 17.0, *)) {
+    // See the comment on this method.
+    if (selector == @selector(insertionPointColor)) {
+      return NO;
+    }
+  }
+  return [super respondsToSelector:selector];
+}
+
 - (void)setTextInputClient:(int)client {
   _textInputClient = client;
   _hasPlaceholder = NO;

shell/platform/darwin/ios/framework/Source/FlutterTextInputPluginTest.mm

@@ -786,6 +786,17 @@ - (void)testDisablingAutocorrectDisablesSpellChecking {
   XCTAssertEqual(inputView.spellCheckingType, UITextSpellCheckingTypeNo);
 }
 
+- (void)testFlutterTextInputViewOnlyRespondsToInsertionPointColorBelowIOS17 {
+  FlutterTextInputView* inputView = [[FlutterTextInputView alloc] initWithOwner:textInputPlugin];
+  BOOL respondsToInsertionPointColor =
+      [inputView respondsToSelector:@selector(insertionPointColor)];
+  if (@available(iOS 17, *)) {
+    XCTAssertFalse(respondsToInsertionPointColor);
+  } else {
+    XCTAssertTrue(respondsToInsertionPointColor);
+  }
+}
+
 #pragma mark - TextEditingDelta tests
 - (void)testTextEditingDeltasAreGeneratedOnTextInput {
   FlutterTextInputView* inputView = [[FlutterTextInputView alloc] initWithOwner:textInputPlugin];