Qt: Handle multiple save game files for disparate games separately (fixes #2887)

CHANGES

@@ -32,6 +32,7 @@ Misc:
  - GBA: Improve detection of valid ELF ROMs
  - mGUI: Enable auto-softpatching (closes mgba.io/i/2899)
  - Qt: Add exporting of SAV + RTC saves from Save Converter to strip RTC data
+ - Qt: Handle multiple save game files for disparate games separately (fixes mgba.io/i/2887)
  - Scripting: Add `callbacks:oneshot` for single-call callbacks
 
 0.10.2: (2023-04-23)

src/platform/qt/CoreController.cpp

@@ -878,6 +878,7 @@ void CoreController::replaceGame(const QString& path) {
 	} else {
 		mCoreLoadFile(m_threadContext.core, fname.toUtf8().constData());
 	}
+	// TODO: Make sure updating the path is handled properly by everything that calls path() and baseDirectory()
 	updateROMInfo();
 }
 
@@ -1256,16 +1257,7 @@ void CoreController::finishFrame() {
 }
 
 void CoreController::updatePlayerSave() {
-	int savePlayerId = 0;
+	int savePlayerId = m_multiplayer->saveId(this);
-	mCoreConfigGetIntValue(&m_threadContext.core->config, "savePlayerId", &savePlayerId);
-	if (savePlayerId == 0 || m_multiplayer->attached() > 1) {
-		if (savePlayerId == m_multiplayer->playerId(this) + 1) {
-			// Player 1 is using our save, so let's use theirs, at least for now.
-			savePlayerId = 1;
-		} else {
-			savePlayerId = m_multiplayer->playerId(this) + 1;
-		}
-	}
 
 	QString saveSuffix;
 	if (savePlayerId < 2) {

src/platform/qt/MultiplayerController.cpp

@@ -276,6 +276,32 @@ bool MultiplayerController::attachGame(CoreController* controller) {
 		return false;
 	}
 
+	QPair<QString, QString> path(controller->path(), controller->baseDirectory());
+	int claimed = m_claimed[path];
+
+	int saveId = 0;
+	mCoreConfigGetIntValue(&controller->thread()->core->config, "savePlayerId", &saveId);
+
+	if (claimed) {
+		player.saveId = 0;
+		for (int i = 0; i < MAX_GBAS; ++i) {
+			if (claimed & (1 << i)) {
+				continue;
+			}
+			player.saveId = i + 1;
+			break;
+		}
+		if (!player.saveId) {
+			LOG(QT, ERROR) << "Couldn't find available save ID";
+			player.saveId = 1;
+		}
+	} else if (saveId) {
+		player.saveId = saveId;
+	} else {
+		player.saveId = 1;
+	}
+	m_claimed[path] |= 1 << (player.saveId - 1);
+
 	m_pids.insert(m_nextPid, player);
 	++m_nextPid;
 	fixOrder();
@@ -337,6 +363,18 @@ void MultiplayerController::detachGame(CoreController* controller) {
 		break;
 	}
 
+	// TODO: This might change if we replace the ROM--make sure to handle this properly
+	QPair<QString, QString> path(controller->path(), controller->baseDirectory());
+	Player& p = m_pids.find(pid).value();
+	if (!p.saveId) {
+		LOG(QT, ERROR) << "Clearing invalid save ID";
+	} else {
+		m_claimed[path] &= ~(1 << (p.saveId - 1));
+		if (!m_claimed[path]) {
+			m_claimed.remove(path);
+		}
+	}
+
 	m_pids.remove(pid);
 	if (m_pids.size() == 0) {
 		m_platform = mPLATFORM_NONE;
@@ -360,6 +398,20 @@ int MultiplayerController::playerId(CoreController* controller) const {
 	return -1;
 }
 
+int MultiplayerController::saveId(CoreController* controller) const {
+	for (int i = 0; i < m_players.count(); ++i) {
+		const Player* p = player(i);
+		if (!p) {
+			LOG(QT, ERROR) << tr("Trying to get save ID for a multiplayer player that's not attached");
+			return -1;
+		}
+		if (p->controller == controller) {
+			return p->saveId;
+		}
+	}
+	return -1;
+}
+
 int MultiplayerController::attached() {
 	int num;
 	num = m_lockstep.attached;

src/platform/qt/MultiplayerController.h

@@ -40,6 +40,7 @@ public:
 
 	int attached();
 	int playerId(CoreController*) const;
+	int saveId(CoreController*) const;
 
 signals:
 	void gameAttached();
@@ -61,6 +62,7 @@ private:
 		int awake = 1;
 		int32_t cyclesPosted = 0;
 		unsigned waitMask = 0;
+		int saveId = 1;
 	};
 
 	Player* player(int id);
@@ -82,6 +84,7 @@ private:
 	QHash<int, Player> m_pids;
 	QList<int> m_players;
 	QMutex m_lock;
+	QHash<QPair<QString, QString>, int> m_claimed;
 };
 
 }