Fix iOS 17 Metal errors when TextInput caret is hidden

[levibuzolic]

Summary:

Fixes#58157.

On iOS 17.2, caretHidden makes a single-line TextInput return CGRectZero from caretRectForPosition:. When the caret moves, Core Animation repeatedly logs Surface 1073741823 x 1073741823 is too large. This activity can prevent XCUITest from detecting an idle app.

This change keeps the caret geometry intact and hides a collapsed caret with a transparent tint. It restores the requested selectionColor for non-empty selections so the highlight and handles remain visible. Fabric also reapplies selectionColor after switching between single-line and multiline backing views.

Changelog:

[IOS] [FIXED] - Prevent hidden TextInput carets from causing repeated Metal surface errors.

Test Plan:

• Ran clang-format on all changed Objective-C files:

  yarn clang-format packages/react-native/Libraries/Text/TextInput/Singleline/RCTUITextField.mm packages/react-native/React/Fabric/Mounting/ComponentViews/TextInput/RCTTextInputComponentView.mm packages/react-native/React/Tests/Text/RCTUITextFieldTests.mm

  Result: passed.

• Built the from-source HelloWorld app:

  xcodebuild -workspace private/helloworld/ios/HelloWorld.xcworkspace -scheme HelloWorld -configuration Debug -sdk iphonesimulator -destination 'generic/platform=iOS Simulator' CODE_SIGNING_ALLOWED=NO build

  Result: BUILD SUCCEEDED.

• Syntax-checked the new Objective-C++ test file:

  RN_SIM_SDK=$(xcrun --sdk iphonesimulator --show-sdk-path)
  RN_SIM_PLATFORM=$(xcrun --sdk iphonesimulator --show-sdk-platform-path)
  xcrun clang++ -fsyntax-only -x objective-c++ -std=c++20 -fobjc-arc -fmodules -fcxx-modules -target arm64-apple-ios15.1-simulator -isysroot "$RN_SIM_SDK" -F "$RN_SIM_PLATFORM/Developer/Library/Frameworks" -I private/helloworld/ios/Pods/Headers/Public/React-Core packages/react-native/React/Tests/Text/RCTUITextFieldTests.mm

  Result: passed.

• Tested private/helloworld on an iPhone SE 3 simulator with iOS 17.2:

  • Before this change: 615 matching Core Animation errors in 15 seconds.
  • After this change: 0 matching errors in 15 seconds.
  • The caret remained hidden while typing, after refocusing, in dark mode, and with a dimmed tint.
  • A non-empty selection kept its configured red highlight and handles.
  • caretHidden={false} kept its visible red caret.

• Tested the same states on iOS 18.0. Both the hidden caret and selection highlight behaved correctly, with no matching errors.

• Tested a native Mac Catalyst harness on macOS 26. A transparent tint hid the caret.

Caret-hiding experiments

These results came from iOS 17.2 during 10 seconds of caret movement:

Strategy	Caret hidden	Errors
Normal caret	No	0
CGRectZero	Yes	160
Zero width, valid origin and height	Yes	66
Zero height, valid origin and width	Yes	160
Valid rectangle moved off-screen	Yes	164
Valid rectangle above the text	Yes	158
CGRectNull	Yes	169
0.01pt width	No	0
Transparent tintColor	Yes	0

References

Apple documentation:

• caretRect(for:)
• UIView.tintColor
• UIView.TintAdjustmentMode.dimmed — returns a desaturated tint colour; measurements showed alpha is scaled rather than reset, so a transparent tint stays transparent.
• UITextSelectionDisplayInteraction — the iOS 17 API behind the rejected alternative.
• WWDC23: What's new with text and text interactions

Repository history:

• e13b9c6e49 (2017-05-29) — the CGRectZero override already existed at this point, so the implementation predates iOS 17 by several years. It was correct when written; iOS 17 changed caret rendering underneath it.
• #38679 — the scrollRangeToVisible: no-op referenced in RCTUITextField.mm.

Apple's documentation does not mention the oversized-surface behaviour, and no public report of the Surface 1073741823 x 1073741823 is too large message could be found. The version range in this document comes from local measurement.