fix(macos): three Fabric focus regressions (blur, sendAccessibilityEvent, VirtualView)

[tvinhas]

Summary

Three independent focus / first-responder regressions on the macOS Fabric path, surfaced while validating the "Verify focus changes" item on the Road to 0.83 tracking issue (#2901). Each one is small, localized, and mirrors an
existing working pattern elsewhere in the codebase.

---

1. RCTViewComponentView.mm — blur() calls a method that doesn't exist on NSWindow

React/Fabric/Mounting/ComponentViews/View/RCTViewComponentView.mm

// Before
- (void)blur
{
  [[self window] resignFirstResponder];
}

// After
- (void)blur
{
  [[self window] makeFirstResponder:nil];
}

NSWindow does not implement resignFirstResponder — only NSResponder subclasses inherit it. Calling that selector on the window is a silent no-op (Objective-C runtime swallows it), so programmatic ref.blur() from JS leaves focus stuck on
the view. The correct AppKit equivalent is makeFirstResponder:nil, which clears the current first responder. This mirrors the working pattern already in RCTTextInputComponentView.mm:995-997 for TextInput.blur().

2. RCTMountingManager.mm — Fabric sendAccessibilityEvent("focus") is a silent no-op on macOS

React/Fabric/Mounting/RCTMountingManager.mm, synchronouslyDispatchAccessbilityEventOnUIThread:

// Before
if ([@"focus" isEqualToString:eventType]) {
  RCTUIView<RCTComponentViewProtocol> *componentView = [_componentViewRegistry findComponentViewWithTag:reactTag];
#if !TARGET_OS_OSX
  UIAccessibilityPostNotification(UIAccessibilityLayoutChangedNotification, componentView);
#endif
  // ↑ macOS branch is empty
}

// After
if ([@"focus" isEqualToString:eventType]) {
  RCTUIView<RCTComponentViewProtocol> *componentView = [_componentViewRegistry findComponentViewWithTag:reactTag];
#if !TARGET_OS_OSX
  UIAccessibilityPostNotification(UIAccessibilityLayoutChangedNotification, componentView);
#else
  if (componentView != nil) {
    [[componentView window] makeFirstResponder:componentView];
    NSAccessibilityPostNotification(componentView, NSAccessibilityFocusedUIElementChangedNotification);
  }
#endif
}

The Fabric path for AccessibilityInfo.setAccessibilityFocus(reactTag) was an unconditional no-op on macOS because the #if !TARGET_OS_OSX guard left no #else branch. The fix mirrors the working old-arch path in
RCTAccessibilityManager.mm:setAccessibilityFocus: (makeFirstResponder: + NSAccessibilityPostNotification(NSAccessibilityFocusedUIElementChangedNotification)) which has been correct for years.

3. RCTVirtualViewComponentView.mm — macOS keyboard-nav hooks for the hideOffscreenVirtualViewsOnIOS optimization

React/Fabric/Mounting/ComponentViews/VirtualView/RCTVirtualViewComponentView.mm

The iOS branch wires accessibilityElementCount and focusItemsInRect: to trigger _unhideIfNeeded when keyboard navigation or VoiceOver reaches a flagged-offscreen view. The macOS branch only had accessibilityChildren (VoiceOver path);
keyboard / Tab navigation had no hook.

Added two AppKit hooks in the macOS branch:

- (BOOL)acceptsFirstResponder
{
  [self _unhideIfNeeded];
  return [super acceptsFirstResponder];
}

- (id)accessibilityHitTest:(NSPoint)point
{
  [self _unhideIfNeeded];
  return [super accessibilityHitTest:point];
}

Partial fix — fully solving Tab-into-fully-hidden-views on macOS requires changing the hide strategy from self.hidden = YES (which removes the view from AppKit's responder chain entirely, so acceptsFirstResponder is never queried) to
something that keeps it in the chain (zero-alpha layer, out-of-bounds frame, etc.). That's a deeper redesign than scoped here. The added hooks catch every case where the view IS visible but flagged offscreen, which is the common case
during scroll, and the comment in-file documents the deeper limitation as a follow-up.

---
Closes the "Verify focus changes" item on #2901 for the three concrete regressions identified. The VirtualView fix is intentionally partial and a follow-up issue can track the hide-strategy redesign separately.

Test Plan

- blur fix: code review against the working TextInput.blur() pattern at RCTTextInputComponentView.mm:995-997. Same call shape ([[<window>] makeFirstResponder:nil]) which has been correct on macOS since the file was added. The
resignFirstResponder line silently no-ops at runtime today; no regression possible from removing it.
- sendAccessibilityEvent fix: code review against the working old-arch path at RCTAccessibilityManager.mm:setAccessibilityFocus: (lines 422-426). Same call shape (makeFirstResponder: +
NSAccessibilityPostNotification(...FocusedUIElementChanged...)). The Fabric path was previously empty on macOS, so any behavior is strictly an improvement.
- VirtualView fix: code review — both new hooks delegate to _unhideIfNeeded and then [super ...]. _unhideIfNeeded is idempotent and fast-pathed when the view is not hidden. No behavior change for visible / non-hidden cases.
- pod install in packages/rn-tester on 0.83-merge succeeds with 86 deps / 85 installed (validated locally; build-system unchanged, this PR only touches .mm files).
- All three changes preserve existing iOS/visionOS behavior — every change is inside a #if TARGET_OS_OSX / #else branch or is a swap of one AppKit-only call for another.

Related

- #2901 — Road to 0.83 tracking issue (closes the "Verify focus changes" item for these three regressions; flags VirtualView hide-strategy redesign as a follow-up)
- RCTAccessibilityManager.mm (old-arch focus path, mirrored by fix #2)
- RCTTextInputComponentView.mm (working blur pattern, mirrored by fix #1)

[Saadnajmi]

closing in favor of #3015 as this authors fork is still locked and can't be updated. Original commit cherry-picked to keep credit.