Revert "[macOS] performKeyEquivalent cleanup (#45946)" (flutter/engine#46374)

This broke some keyboard shortcut handling (e.g. cmd-a to select all).

This reverts commit 0deacc6c70.


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engine/src/flutter/shell/platform/darwin/macos/framework/Source/FlutterViewController.mm

@@ -164,6 +164,8 @@ NSData* currentKeyboardLayoutData() {
 
 - (void)setBackgroundColor:(NSColor*)color;
 
+- (BOOL)performKeyEquivalent:(NSEvent*)event;
+
 @end
 
 /**
@@ -240,6 +242,37 @@ NSData* currentKeyboardLayoutData() {
 
 @end
 
+#pragma mark - NSEvent (KeyEquivalentMarker) protocol
+
+@interface NSEvent (KeyEquivalentMarker)
+
+// Internally marks that the event was received through performKeyEquivalent:.
+// When text editing is active, keyboard events that have modifier keys pressed
+// are received through performKeyEquivalent: instead of keyDown:. If such event
+// is passed to TextInputContext but doesn't result in a text editing action it
+// needs to be forwarded by FlutterKeyboardManager to the next responder.
+- (void)markAsKeyEquivalent;
+
+// Returns YES if the event is marked as a key equivalent.
+- (BOOL)isKeyEquivalent;
+
+@end
+
+@implementation NSEvent (KeyEquivalentMarker)
+
+// This field doesn't need a value because only its address is used as a unique identifier.
+static char markerKey;
+
+- (void)markAsKeyEquivalent {
+  objc_setAssociatedObject(self, &markerKey, @true, OBJC_ASSOCIATION_RETAIN);
+}
+
+- (BOOL)isKeyEquivalent {
+  return [objc_getAssociatedObject(self, &markerKey) boolValue] == YES;
+}
+
+@end
+
 #pragma mark - Private dependant functions
 
 namespace {
@@ -279,15 +312,19 @@ void OnKeyboardLayoutChanged(CFNotificationCenterRef center,
 }
 
 - (BOOL)performKeyEquivalent:(NSEvent*)event {
-  // Do not intercept the event if flutterView is not first responder, otherwise this would
-  // interfere with TextInputPlugin, which also handles key equivalents.
-  //
-  // Also do not intercept the event if key equivalent is a product of an event being
-  // redispatched by the TextInputPlugin, in which case it needs to bubble up so that menus
-  // can handle key equivalents.
-  if (self.window.firstResponder != _flutterView || [_controller isDispatchingKeyEvent:event]) {
+  if ([_controller isDispatchingKeyEvent:event]) {
+    // When NSWindow is nextResponder, keyboard manager will send to it
+    // unhandled events (through [NSWindow keyDown:]). If event has both
+    // control and cmd modifiers set (i.e. cmd+control+space - emoji picker)
+    // NSWindow will then send this event as performKeyEquivalent: to first
+    // responder, which might be FlutterTextInputPlugin. If that's the case, the
+    // plugin must not handle the event, otherwise the emoji picker would not
+    // work (due to first responder returning YES from performKeyEquivalent:)
+    // and there would be an infinite loop, because FlutterViewController will
+    // send the event back to [keyboardManager handleEvent:].
     return NO;
   }
+  [event markAsKeyEquivalent];
   [_flutterView keyDown:event];
   return YES;
 }

engine/src/flutter/shell/platform/darwin/macos/framework/Source/FlutterViewControllerTest.mm

@@ -331,13 +331,6 @@ TEST(FlutterViewControllerTest, testViewControllerIsReleased) {
   const uint64_t kPhysicalKeyTab = 0x7002b;
 
   [viewController viewWillAppear];  // Initializes the event channel.
-  // Creates a NSWindow so that FlutterView view can be first responder.
-  NSWindow* window = [[NSWindow alloc] initWithContentRect:NSMakeRect(0, 0, 800, 600)
-                                                 styleMask:NSBorderlessWindowMask
-                                                   backing:NSBackingStoreBuffered
-                                                     defer:NO];
-  window.contentView = viewController.view;
-  [window makeFirstResponder:viewController.flutterView];
   [viewController.view performKeyEquivalent:event];
 
   EXPECT_TRUE(called);