allow user_choice in prestart for invisible choices

src/persist_var.cpp

@@ -50,6 +50,7 @@ struct persist_choice: mp_sync::user_choice {
 	virtual config random_choice() const {
 		return config();
 	}
+	virtual bool is_visible() const { return false; }
 };
 
 static void get_global_variable(persist_context &ctx, const vconfig &pcfg)

src/replay.cpp

@@ -1125,14 +1125,12 @@ config mp_sync::get_user_choice(const std::string &name, const mp_sync::user_cho
 		WRN_REPLAY << "MP synchronization called during an unsynced context.";; 
 		return uch.query_user();
 	}
-	if(is_too_early)
+	if(is_too_early && uch.is_visible())
 	{
 		//We are in a prestart event or even earlier.
 		//Although we are able to sync them, we cannot use query_user,
 		//because we cannot (or shouldn't) put things on the screen inside a prestart event, this is true for SP and MP games.
 		//Quotation form event wiki: "For things displayed on-screen such as character dialog, use start instead"
-		//Note, that there are also user choices that don't require on-screen dialogs like [get_global_variable]
-		//TODO: find a solution in these cases.
 		return uch.random_choice();
 	}
 	//in start events it's unclear to decide on which side the function should be executed (default= side1 still). 

src/replay.hpp

@@ -190,6 +190,9 @@ struct user_choice
 	virtual ~user_choice() {}
 	virtual config query_user() const = 0;
 	virtual config random_choice() const = 0;
+	///whether the choice is visible for the user like an advacement choice
+	///a non-visible choice is for example get_global_variable
+	virtual bool is_visible() const { return true; }
 };
 
 /**

src/scripting/lua.cpp

@@ -2677,6 +2677,10 @@ namespace {
 		{
 			return config();
 		}
+		//Although luas sync_choice can show a dialog, (and will in most cases)
+		//we return false to enable other possible things that do not contain UI things.
+		//it's in the responsbility of the umc dev to not show dialogs durign prestart events.
+		virtual bool is_visible() const { return false; }
 	};
 }//unnamed namespace for lua_synchronize