take this a bit further

src/frontend/qt_sdl/EmuThread.cpp

@@ -595,6 +595,36 @@ void EmuThread::handleMessages()
             emuInstance->nds->Start();
             bootResult = 1;
             break;
+
+        case msg_InsertCart:
+            bootResult = 0;
+            if (!emuInstance->loadROM(msg.param.value<QStringList>(), false))
+                break;
+
+            bootResult = 1;
+            break;
+
+        case msg_EjectCart:
+            emuInstance->ejectCart();
+            break;
+
+        case msg_InsertGBACart:
+            bootResult = 0;
+            if (!emuInstance->loadGBAROM(msg.param.value<QStringList>()))
+                break;
+
+            bootResult = 1;
+            break;
+
+        case msg_InsertGBAAddon:
+            bootResult = 0;
+            emuInstance->loadGBAAddon(msg.param.value<int>());
+            bootResult = 1;
+            break;
+
+        case msg_EjectGBACart:
+            emuInstance->ejectCart();
+            break;
         }
 
         msgSemaphore.release();
@@ -681,11 +711,10 @@ bool EmuThread::emuIsActive()
     return emuActive;
 }
 
-int EmuThread::bootROM(QStringList filename)
+int EmuThread::bootROM(const QStringList& filename)
 {
-    sendMessage(msg_EmuPause);
     sendMessage({.type = msg_BootROM, .param = filename});
-    waitMessage(2);
+    waitMessage();
     if (!bootResult)
         return bootResult;
 
@@ -696,9 +725,8 @@ int EmuThread::bootROM(QStringList filename)
 
 int EmuThread::bootFirmware()
 {
-    sendMessage(msg_EmuPause);
     sendMessage(msg_BootFirmware);
-    waitMessage(2);
+    waitMessage();
     if (!bootResult)
         return bootResult;
 
@@ -707,6 +735,28 @@ int EmuThread::bootFirmware()
     return bootResult;
 }
 
+int EmuThread::insertCart(const QStringList& filename, bool gba)
+{
+    MessageType msgtype = gba ? msg_InsertGBACart : msg_InsertCart;
+
+    sendMessage({.type = msgtype, .param = filename});
+    waitMessage();
+    return bootResult;
+}
+
+void EmuThread::ejectCart(bool gba)
+{
+    sendMessage(gba ? msg_EjectGBACart : msg_EjectCart);
+    waitMessage();
+}
+
+int EmuThread::insertGBAAddon(int type)
+{
+    sendMessage({.type = msg_InsertGBAAddon, .param = type});
+    waitMessage();
+    return bootResult;
+}
+
 void EmuThread::updateRenderer()
 {
     if (videoRenderer != lastVideoRenderer)

src/frontend/qt_sdl/EmuThread.h

@@ -71,6 +71,11 @@ public:
 
         msg_BootROM,
         msg_BootFirmware,
+        msg_InsertCart,
+        msg_EjectCart,
+        msg_InsertGBACart,
+        msg_InsertGBAAddon,
+        msg_EjectGBACart,
     };
 
     struct Message
@@ -100,8 +105,11 @@ public:
     void emuFrameStep();
     void emuReset();
 
-    int bootROM(QStringList filename);
+    int bootROM(const QStringList& filename);
     int bootFirmware();
+    int insertCart(const QStringList& filename, bool gba);
+    void ejectCart(bool gba);
+    int insertGBAAddon(int type);
 
     bool emuIsRunning();
     bool emuIsActive();

src/frontend/qt_sdl/Window.cpp

@@ -1330,56 +1330,35 @@ void MainWindow::onBootFirmware()
 
 void MainWindow::onInsertCart()
 {
-    emuThread->emuPause();
-
     QStringList file = pickROM(false);
     if (file.isEmpty())
+        return;
+
+    if (!emuThread->insertCart(file, false))
     {
-        emuThread->emuUnpause();
         return;
     }
 
-    if (!emuInstance->loadROM(file, false))
-    {
-        emuThread->emuUnpause();
-        return;
-    }
-
-    emuThread->emuUnpause();
-
     updateCartInserted(false);
 }
 
 void MainWindow::onEjectCart()
 {
-    emuThread->emuPause();
-
-    emuInstance->ejectCart();
-
-    emuThread->emuUnpause();
-
+    emuThread->ejectCart(false);
     updateCartInserted(false);
 }
 
 void MainWindow::onInsertGBACart()
 {
-    emuThread->emuPause();
-
     QStringList file = pickROM(true);
     if (file.isEmpty())
+        return;
+
+    if (!emuThread->insertCart(file, true))
     {
-        emuThread->emuUnpause();
         return;
     }
 
-    if (!emuInstance->loadGBAROM(file))
-    {
-        emuThread->emuUnpause();
-        return;
-    }
-
-    emuThread->emuUnpause();
-
     updateCartInserted(true);
 }
 
@@ -1388,23 +1367,13 @@ void MainWindow::onInsertGBAAddon()
     QAction* act = (QAction*)sender();
     int type = act->data().toInt();
 
-    emuThread->emuPause();
-
-    emuInstance->loadGBAAddon(type);
-
-    emuThread->emuUnpause();
-
+    emuThread->insertGBAAddon(type);
     updateCartInserted(true);
 }
 
 void MainWindow::onEjectGBACart()
 {
-    emuThread->emuPause();
-
-    emuInstance->ejectGBACart();
-
-    emuThread->emuUnpause();
-
+    emuThread->ejectCart(true);
     updateCartInserted(true);
 }