M src/platform/qt/GBAApp.cpp → src/platform/qt/GBAApp.cpp

@@ -127,6 +127,9 @@ Window* w = new Window(&m_configController, m_multiplayer.attached());
 	int windowId = m_multiplayer.attached();
 	connect(w, &Window::destroyed, [this, w]() {
 		m_windows.removeAll(w);
+		for (Window* w : m_windows) {
+			w->updateMultiplayerStatus(m_windows.count() < MAX_GBAS);
+		}
 	});
 	m_windows.append(w);
 	w->setAttribute(Qt::WA_DeleteOnClose);
@@ -134,6 +137,9 @@ w->loadConfig();
 	w->show();
 	w->controller()->setMultiplayerController(&m_multiplayer);
 	w->multiplayerChanged();
+	for (Window* w : m_windows) {
+		w->updateMultiplayerStatus(m_windows.count() < MAX_GBAS);
+	}
 	return w;
 }
 

M src/platform/qt/Window.cpp → src/platform/qt/Window.cpp

@@ -1088,11 +1088,11 @@ addControlledAction(fileMenu, exportShark, "exportShark");
 #endif
 
 	fileMenu->addSeparator();
-	QAction* multiWindow = new QAction(tr("New multiplayer window"), fileMenu);
-	connect(multiWindow, &QAction::triggered, [this]() {
+	m_multiWindow = new QAction(tr("New multiplayer window"), fileMenu);
+	connect(m_multiWindow, &QAction::triggered, [this]() {
 		GBAApp::app()->newWindow();
 	});
-	addControlledAction(fileMenu, multiWindow, "multiWindow");
+	addControlledAction(fileMenu, m_multiWindow, "multiWindow");
 
 #ifndef Q_OS_MAC
 	fileMenu->addSeparator();

M src/platform/qt/Window.h → src/platform/qt/Window.h

@@ -49,6 +49,8 @@ void argumentsPassed(mArguments*);
 
 	void resizeFrame(const QSize& size);
 
+	void updateMultiplayerStatus(bool canOpenAnother) { m_multiWindow->setEnabled(canOpenAnother); }
+
 signals:
 	void startDrawing(mCoreThread*);
 	void shutdown();
@@ -160,6 +162,7 @@ QList<QAction*> m_nonMpActions;
 #ifdef M_CORE_GBA
 	QList<QAction*> m_gbaActions;
 #endif
+	QAction* m_multiWindow;
 	QMap<int, QAction*> m_frameSizes;
 	LogController m_log;
 	LogView* m_logView;