Trigger save slot display from UI code.

Core shouldn't be calling UI code.

Core/SaveState.cpp

@@ -379,10 +379,7 @@ namespace SaveState
 
 	void NextSlot()
 	{
-		I18NCategory *sy = GetI18NCategory("System");
 		g_Config.iCurrentStateSlot = (g_Config.iCurrentStateSlot + 1) % NUM_SLOTS;
-		std::string msg = StringFromFormat("%s: %d", sy->T("Savestate Slot"), g_Config.iCurrentStateSlot + 1);
-		osm.Show(msg);
 	}
 
 	void LoadSlot(const std::string &gameFilename, int slot, Callback callback, void *cbUserData)

UI/EmuScreen.cpp

@@ -398,6 +398,7 @@ void EmuScreen::onVKeyDown(int virtualKeyCode) {
 		break;
 	case VIRTKEY_NEXT_SLOT:
 		SaveState::NextSlot();
+		NativeMessageReceived("savestate_displayslot", "");
 		break;
 	case VIRTKEY_TOGGLE_FULLSCREEN:
 		System_SendMessage("toggle_fullscreen", "");

UI/NativeApp.cpp

@@ -766,6 +766,11 @@ void HandleGlobalMessage(const std::string &msg, const std::string &value) {
 			g_Config.sNickName = inputboxValue[1];
 		inputboxValue.clear();
 	}
+	if (msg == "savestate_displayslot") {
+		I18NCategory *sy = GetI18NCategory("System");
+		std::string msg = StringFromFormat("%s: %d", sy->T("Savestate Slot"), SaveState::GetCurrentSlot() + 1);
+		osm.Show(msg);
+	}
 }
 
 void NativeUpdate(InputState &input) {

Windows/MainWindowMenu.cpp

@@ -580,6 +580,7 @@ namespace MainWindow {
 		case ID_FILE_SAVESTATE_NEXT_SLOT:
 		{
 			SaveState::NextSlot();
+			NativeMessageReceived("savestate_displayslot", "");
 			break;
 		}
 
@@ -588,6 +589,7 @@ namespace MainWindow {
 			if (KeyMap::g_controllerMap[VIRTKEY_NEXT_SLOT].empty())
 			{
 				SaveState::NextSlot();
+				NativeMessageReceived("savestate_displayslot", "");
 			}
 			break;
 		}