Add vehicle introduction randomisation setting and update logic

src/engine.cpp

@@ -737,7 +737,11 @@ void StartupOneEngine(Engine *e, const TimerGameCalendar::YearMonthDay &aging_ym
 	/* Don't randomise the start-date in the first two years after gamestart to ensure availability
 	 * of engines in early starting games.
 	 * Note: TTDP uses fixed 1922 */
-	e->intro_date = ei->base_intro <= TimerGameCalendar::ConvertYMDToDate(_settings_game.game_creation.starting_year + 2, 0, 1) ? ei->base_intro : (TimerGameCalendar::Date)GB(r, 0, 9) + ei->base_intro;
+	if (_settings_game.vehicle.vehicle_intro_randomisation) {
+		e->intro_date = ei->base_intro <= TimerGameCalendar::ConvertYMDToDate(_settings_game.game_creation.starting_year + 2, 0, 1) ? ei->base_intro : (TimerGameCalendar::Date)GB(r, 0, 9) + ei->base_intro;
+	} else {
+		e->intro_date = ei->base_intro;
+	}
 	if (e->intro_date <= TimerGameCalendar::date) {
 		TimerGameCalendar::YearMonthDay intro_ymd = TimerGameCalendar::ConvertDateToYMD(e->intro_date);
 		int aging_months = aging_ymd.year.base() * 12 + aging_ymd.month;

src/lang/english.txt

@@ -1511,6 +1511,9 @@ STR_CONFIG_SETTING_NEVER_EXPIRE_VEHICLES_HELPTEXT               :When enabled, a
 STR_CONFIG_SETTING_OFFER_VEHICLE_PREVIEW                        :Show vehicle previews: {STRING2}
 STR_CONFIG_SETTING_OFFER_VEHICLE_PREVIEW_HELPTEXT               :When enabled, the top performing company is sometimes offered a 1 year exclusive preview of a vehicle
 
+STR_CONFIG_SETTING_VEHICLE_INTRO_RANDOMISATION                  :Randomise vehicle introduction dates: {STRING2}
+STR_CONFIG_SETTING_VEHICLE_INTRO_RANDOMISATION_HELPTEXT         :When enabled, randomises vehicle introduction dates by up to 511 extra days from their original date
+
 STR_CONFIG_SETTING_TIMEKEEPING_UNITS                            :Timekeeping: {STRING2}
 STR_CONFIG_SETTING_TIMEKEEPING_UNITS_HELPTEXT                   :Select the timekeeping units of the game. This cannot be changed later.{}{}Calendar-based is the classic OpenTTD experience, with a year consisting of 12 months, and each month having 28-31 days.{}{}In Wallclock-based time, cargo production and financials are instead based on one-minute increments, which is about as long as a 30 day month takes in Calendar-based mode. These are grouped into 12-minute periods, equivalent to a year in Calendar-based mode.{}{}In either mode there is always a classic calendar, which is used for introduction dates of vehicles, houses, and other infrastructure
 ###length 2

src/settingentry_gui.cpp

@@ -821,6 +821,7 @@ SettingsContainer &GetSettingsTree()
 			limitations->Add(new SettingEntry("station.never_expire_airports"));
 			limitations->Add(new SettingEntry("vehicle.never_expire_vehicles"));
 			limitations->Add(new SettingEntry("vehicle.offer_vehicle_preview"));
+			limitations->Add(new SettingEntry("vehicle.vehicle_intro_randomisation"));
 			limitations->Add(new SettingEntry("vehicle.max_trains"));
 			limitations->Add(new SettingEntry("vehicle.max_roadveh"));
 			limitations->Add(new SettingEntry("vehicle.max_aircraft"));

src/settings_type.h

@@ -512,6 +512,7 @@ struct VehicleSettings {
 	bool   dynamic_engines;                  ///< enable dynamic allocation of engine data
 	bool   never_expire_vehicles;            ///< never expire vehicles
 	bool   offer_vehicle_preview;            ///< offer vehicle preview to companies
+	bool   vehicle_intro_randomisation;      ///< randomise the introduction dates of vehicles
 	uint8_t extend_vehicle_life;              ///< extend vehicle life by this many years
 	uint8_t road_side;                        ///< the side of the road vehicles drive on
 	uint8_t  plane_crashes;                    ///< number of plane crashes, 0 = none, 1 = reduced, 2 = normal

src/table/settings/game_settings.ini

@@ -248,6 +248,13 @@ def      = true
 str      = STR_CONFIG_SETTING_OFFER_VEHICLE_PREVIEW
 strhelp  = STR_CONFIG_SETTING_OFFER_VEHICLE_PREVIEW_HELPTEXT
 
+[SDT_BOOL]
+var      = vehicle.vehicle_intro_randomisation
+flags    = SettingFlag::NoNetwork
+def      = true
+str      = STR_CONFIG_SETTING_VEHICLE_INTRO_RANDOMISATION
+strhelp  = STR_CONFIG_SETTING_VEHICLE_INTRO_RANDOMISATION_HELPTEXT
+
 [SDT_VAR]
 var      = vehicle.max_trains
 type     = SLE_UINT16