From eee6356c73bc7597e2be23640526b01f3f30d91b Mon Sep 17 00:00:00 2001
From: Bryan Oltman <[email protected]>
Date: Wed, 20 May 2026 18:22:24 -0700
Subject: [PATCH] [macOS] Drop redispatched events if window is no longer key

When an unhandled renderer event is returned for system processing,
the CommandDispatcher redispatches it. If the window has lost its
"key" status (e.g., due to a focus change while the event was
in-flight), redispatching it can cause the event to be incorrectly
handled by the newly focused window.

This CL ensures that we only redispatch events if the target window
is still the key window.

Fixed: 514063409
Change-Id: I022d7f45d5c35d26a96b4efc55c0621eb73b3a80
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7864509
Reviewed-by: Avi Drissman <[email protected]>
Commit-Queue: Bryan Oltman <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1633968}
---

diff --git a/ui/base/BUILD.gn b/ui/base/BUILD.gn
index 49a345c7..1add8ac9 100644
--- a/ui/base/BUILD.gn
+++ b/ui/base/BUILD.gn
@@ -1116,6 +1116,7 @@
       "cocoa/base_view_unittest.mm",
       "cocoa/bubble_closer_unittest.mm",
       "cocoa/cocoa_base_utils_unittest.mm",
+      "cocoa/command_dispatcher_unittest.mm",
       "cocoa/constrained_window/constrained_window_animation_unittest.mm",
       "cocoa/defaults_utils_unittest.mm",
       "cocoa/nsmenu_additions_unittest.mm",
diff --git a/ui/base/cocoa/command_dispatcher.mm b/ui/base/cocoa/command_dispatcher.mm
index 5b05c78..f1b8c36 100644
--- a/ui/base/cocoa/command_dispatcher.mm
+++ b/ui/base/cocoa/command_dispatcher.mm
@@ -197,6 +197,12 @@
   CHECK(eventType == NSEventTypeKeyDown || eventType == NSEventTypeKeyUp ||
         eventType == NSEventTypeFlagsChanged);
 
+  // If the event's window is no longer the key window, don't attempt to
+  // redispatch it (https://crbug.com/514063409).
+  if (event.window && !event.window.keyWindow) {
+    return NO;
+  }
+
   // Sometimes, an event will be redispatched from a child window to a parent
   // window to allow the parent window a chance to handle it. In that case, fix
   // up the native event to reference the correct window. Failure to do this can
diff --git a/ui/base/cocoa/command_dispatcher_unittest.mm b/ui/base/cocoa/command_dispatcher_unittest.mm
new file mode 100644
index 0000000..dc78fc4
--- /dev/null
+++ b/ui/base/cocoa/command_dispatcher_unittest.mm
@@ -0,0 +1,106 @@
+// Copyright 2026 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ui/base/cocoa/command_dispatcher.h"
+
+#include "base/test/task_environment.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "testing/gtest_mac.h"
+#import "ui/base/test/cocoa_helper.h"
+
+@interface TestCommandDispatchingWindow
+    : CocoaTestHelperWindow <CommandDispatchingWindow> {
+  CommandDispatcher* __strong _dispatcher;
+}
+@end
+
+@implementation TestCommandDispatchingWindow
+
+- (instancetype)initWithContentRect:(NSRect)contentRect {
+  if ((self = [super initWithContentRect:contentRect])) {
+    _dispatcher = [[CommandDispatcher alloc] initWithOwner:self];
+  }
+  return self;
+}
+
+- (CommandDispatcher*)commandDispatcher {
+  return _dispatcher;
+}
+
+- (NSWindow<CommandDispatchingWindow>*)commandDispatchParent {
+  return nil;
+}
+
+- (void)setCommandHandler:(id<UserInterfaceItemCommandHandler>)commandHandler {
+}
+
+- (BOOL)defaultPerformKeyEquivalent:(NSEvent*)event {
+  return NO;
+}
+
+- (BOOL)defaultValidateUserInterfaceItem:
+    (id<NSValidatedUserInterfaceItem>)item {
+  return NO;
+}
+
+- (void)commandDispatch:(id)sender {
+}
+
+- (void)commandDispatchUsingKeyModifiers:(id)sender {
+}
+
+@end
+
+namespace ui {
+
+class CommandDispatcherTest : public CocoaTest {
+ public:
+  void SetUp() override {
+    CocoaTest::SetUp();
+    window_ = [[TestCommandDispatchingWindow alloc] init];
+    key_event_ = [NSEvent keyEventWithType:NSEventTypeKeyDown
+                                  location:NSZeroPoint
+                             modifierFlags:0
+                                 timestamp:0
+                              windowNumber:window_.windowNumber
+                                   context:nil
+                                characters:@"a"
+               charactersIgnoringModifiers:@"a"
+                                 isARepeat:NO
+                                   keyCode:0];
+  }
+
+  void TearDown() override {
+    key_event_ = nil;
+    [window_ close];
+    window_ = nil;
+    CocoaTest::TearDown();
+  }
+
+  TestCommandDispatchingWindow* __strong window_;
+  NSEvent* __strong key_event_;
+  base::test::TaskEnvironment task_environment_{
+      base::test::TaskEnvironment::MainThreadType::UI};
+};
+
+// Verifies that -redispatchKeyEvent: drops redispatched events (unhandled
+// renderer events returned for system processing) when the window is no longer
+// key, as they would otherwise be incorrectly redirected to the now-key window.
+TEST_F(CommandDispatcherTest, RedispatchDropsEventIfWindowNotKey) {
+  CommandDispatcher* dispatcher = [window_ commandDispatcher];
+  window_.pretendIsKeyWindow = NO;
+  EXPECT_FALSE(window_.isKeyWindow);
+  EXPECT_FALSE([dispatcher redispatchKeyEvent:key_event_]);
+}
+
+// Tests that -redispatchKeyEvent: correctly redispatches events when the
+// window is still key, allowing normal system handling of unhandled keys.
+TEST_F(CommandDispatcherTest, RedispatchSendsEventIfWindowIsKey) {
+  CommandDispatcher* dispatcher = [window_ commandDispatcher];
+  window_.pretendIsKeyWindow = YES;
+  EXPECT_TRUE(window_.isKeyWindow);
+  EXPECT_TRUE([dispatcher redispatchKeyEvent:key_event_]);
+}
+
+}  // namespace ui

diff --git a/ui/base/cocoa/command_dispatcher_unittest.mm b/ui/base/cocoa/command_dispatcher_unittest.mm
new file mode 100644
index 0000000..dc78fc4
--- /dev/null
+++ b/ui/base/cocoa/command_dispatcher_unittest.mm
@@ -0,0 +1,106 @@
+// Copyright 2026 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ui/base/cocoa/command_dispatcher.h"
+
+#include "base/test/task_environment.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "testing/gtest_mac.h"
+#import "ui/base/test/cocoa_helper.h"
+
+@interface TestCommandDispatchingWindow
+    : CocoaTestHelperWindow <CommandDispatchingWindow> {
+  CommandDispatcher* __strong _dispatcher;
+}
+@end
+
+@implementation TestCommandDispatchingWindow
+
+- (instancetype)initWithContentRect:(NSRect)contentRect {
+  if ((self = [super initWithContentRect:contentRect])) {
+    _dispatcher = [[CommandDispatcher alloc] initWithOwner:self];
+  }
+  return self;
+}
+
+- (CommandDispatcher*)commandDispatcher {
+  return _dispatcher;
+}
+
+- (NSWindow<CommandDispatchingWindow>*)commandDispatchParent {
+  return nil;
+}
+
+- (void)setCommandHandler:(id<UserInterfaceItemCommandHandler>)commandHandler {
+}
+
+- (BOOL)defaultPerformKeyEquivalent:(NSEvent*)event {
+  return NO;
+}
+
+- (BOOL)defaultValidateUserInterfaceItem:
+    (id<NSValidatedUserInterfaceItem>)item {
+  return NO;
+}
+
+- (void)commandDispatch:(id)sender {
+}
+
+- (void)commandDispatchUsingKeyModifiers:(id)sender {
+}
+
+@end
+
+namespace ui {
+
+class CommandDispatcherTest : public CocoaTest {
+ public:
+  void SetUp() override {
+    CocoaTest::SetUp();
+    window_ = [[TestCommandDispatchingWindow alloc] init];
+    key_event_ = [NSEvent keyEventWithType:NSEventTypeKeyDown
+                                  location:NSZeroPoint
+                             modifierFlags:0
+                                 timestamp:0
+                              windowNumber:window_.windowNumber
+                                   context:nil
+                                characters:@"a"
+               charactersIgnoringModifiers:@"a"
+                                 isARepeat:NO
+                                   keyCode:0];
+  }
+
+  void TearDown() override {
+    key_event_ = nil;
+    [window_ close];
+    window_ = nil;
+    CocoaTest::TearDown();
+  }
+
+  TestCommandDispatchingWindow* __strong window_;
+  NSEvent* __strong key_event_;
+  base::test::TaskEnvironment task_environment_{
+      base::test::TaskEnvironment::MainThreadType::UI};
+};
+
+// Verifies that -redispatchKeyEvent: drops redispatched events (unhandled
+// renderer events returned for system processing) when the window is no longer
+// key, as they would otherwise be incorrectly redirected to the now-key window.
+TEST_F(CommandDispatcherTest, RedispatchDropsEventIfWindowNotKey) {
+  CommandDispatcher* dispatcher = [window_ commandDispatcher];
+  window_.pretendIsKeyWindow = NO;
+  EXPECT_FALSE(window_.isKeyWindow);
+  EXPECT_FALSE([dispatcher redispatchKeyEvent:key_event_]);
+}
+
+// Tests that -redispatchKeyEvent: correctly redispatches events when the
+// window is still key, allowing normal system handling of unhandled keys.
+TEST_F(CommandDispatcherTest, RedispatchSendsEventIfWindowIsKey) {
+  CommandDispatcher* dispatcher = [window_ commandDispatcher];
+  window_.pretendIsKeyWindow = YES;
+  EXPECT_TRUE(window_.isKeyWindow);
+  EXPECT_TRUE([dispatcher redispatchKeyEvent:key_event_]);
+}
+
+}  // namespace ui