tvOS: Back on the main screen goes to the home screen, like on Android

tvOS only does that with a Back press it gets to see, so the view controller
lets controller events through to UIKit while the top screen is top level
(the new TOP_LEVEL_CHANGED notification), and passes presses that aren't
keyboard keys on to super. Elsewhere Back stays ours.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Common/System/System.h

@@ -277,6 +277,7 @@ enum class SystemNotification {
 	PAD_STATE_CHANGED,
 	CONFIG_LOADED,
 	BEFORE_CONFIG_SAVE_ON_EXIT,
+	TOP_LEVEL_CHANGED,  // NativeIsAtTopLevel() changed. From the render thread.
 };
 
 // I guess it's not super great architecturally to centralize this, since it's not general - but same with a lot of

Common/UI/ScreenManager.cpp

@@ -1,4 +1,5 @@
 #include "Common/System/Display.h"
+#include "Common/System/System.h"
 #include "Common/Data/Collections/TinySet.h"
 #include "Common/UI/ScreenManager.h"
 #include "Common/UI/Root.h"
@@ -133,13 +134,15 @@ void ScreenManager::Update() {
 		overlayScreen_->update();
 	}
 
+	bool topLevel = false;
 	if (!stack_.empty()) {
 		Screen *backScreen = stack_.back().screen;
 		backScreen->update();
 		passInputToMapper_ = backScreen->PassInputToMapper();
-		topIsTopLevel_ = backScreen->isTopLevel();
-	} else {
-		topIsTopLevel_ = false;
+		topLevel = backScreen->isTopLevel();
+	}
+	if (topIsTopLevel_.exchange(topLevel) != topLevel) {
+		System_Notify(SystemNotification::TOP_LEVEL_CHANGED);
 	}
 }
 

ios/ViewController.h

@@ -46,6 +46,7 @@
 - (void)willResignActive;
 
 - (void)uiStateChanged;
+- (void)topLevelChanged;
 - (void)pickPhoto:(NSString *)saveFilename requestId:(int)requestId;
 - (void)updateResolutionWithView:(UIView *)view;
 

ios/ViewController.mm

@@ -202,7 +202,7 @@ static int GetPickerRequestId(id picker) {
 		[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(controllerDidDisconnect:) name:GCControllerDidDisconnectNotification object:nil];
 
 #if PPSSPP_PLATFORM(TVOS)
-		// Already the default. Should become YES at the top level menu, so the Menu button goes home.
+		// Already the default. See topLevelChanged.
 		self.controllerUserInteractionEnabled = NO;
 #else
 		// Observe orientation changes
@@ -392,6 +392,15 @@ static int GetPickerRequestId(id picker) {
 	}
 }
 
+// Like Android, Back on the main screen leaves the app. tvOS only does that with a Back press it
+// gets to see, so let controller events through to UIKit there. They still reach GCController.
+- (void)topLevelChanged {
+#if PPSSPP_PLATFORM(TVOS)
+	self.controllerUserInteractionEnabled = NativeIsAtTopLevel() ? YES : NO;
+	INFO_LOG(Log::System, "Controller events to UIKit: %s", self.controllerUserInteractionEnabled ? "yes" : "no");
+#endif
+}
+
 - (void)setupController:(GCController *)controller {
 	self.gameController = controller;
 	if (!InitController(controller)) {
@@ -698,16 +707,36 @@ extern float g_safeInsetBottom;
 	return YES;
 }
 
+// Presses that aren't keyboard keys, like the remote's buttons, go on up the responder chain. On
+// tvOS, that's what takes Back on the main screen to the home screen (see topLevelChanged).
+static NSSet<UIPress *> *NonKeyboardPresses(NSSet<UIPress *> *presses) {
+	return [presses objectsPassingTest:^BOOL(UIPress *press, BOOL *stop) {
+		return press.key == nil;
+	}];
+}
+
 - (void)pressesBegan:(NSSet<UIPress *> *)presses withEvent:(UIPressesEvent *)event {
 	KeyboardPressesBegan(presses, event);
+	NSSet<UIPress *> *others = NonKeyboardPresses(presses);
+	if (others.count) {
+		[super pressesBegan:others withEvent:event];
+	}
 }
 
 - (void)pressesEnded:(NSSet<UIPress *> *)presses withEvent:(UIPressesEvent *)event {
 	KeyboardPressesEnded(presses, event);
+	NSSet<UIPress *> *others = NonKeyboardPresses(presses);
+	if (others.count) {
+		[super pressesEnded:others withEvent:event];
+	}
 }
 
 - (void)pressesCancelled:(NSSet<UIPress *> *)presses withEvent:(UIPressesEvent *)event {
 	KeyboardPressesEnded(presses, event);
+	NSSet<UIPress *> *others = NonKeyboardPresses(presses);
+	if (others.count) {
+		[super pressesCancelled:others withEvent:event];
+	}
 }
 
 #pragma mark - Status Bar Control

ios/main.mm

@@ -438,6 +438,13 @@ void System_Notify(SystemNotification notification) {
 			}
 		});
 		break;
+	case SystemNotification::TOP_LEVEL_CHANGED:
+		dispatch_async(dispatch_get_main_queue(), ^{
+			if (sharedViewController) {
+				[sharedViewController topLevelChanged];
+			}
+		});
+		break;
 	case SystemNotification::AUDIO_MODE_CHANGED:
 		dispatch_async(dispatch_get_main_queue(), ^{
 			iOSCoreAudioUpdateSession();