Add setting to select cargo payment algorithm

See: #506

src/economy.cpp

@@ -1071,13 +1071,18 @@ Money GetTransportedGoodsIncome(uint num_pieces, uint dist, uint16 transit_days,
 	static const int TIME_FACTOR_FRAC_BITS = 4;
 	static const int TIME_FACTOR_FRAC = 1 << TIME_FACTOR_FRAC_BITS;
 
+	if (_settings_game.economy.payment_algorithm == CPA_TRADITIONAL) transit_days = std::min<uint16>(transit_days, 0xFFu);
+
 	const int days1 = cs->transit_days[0];
 	const int days2 = cs->transit_days[1];
 	const int days_over_days1 = std::max(   transit_days - days1, 0);
 	const int days_over_days2 = std::max(days_over_days1 - days2, 0);
-	int days_over_max = MIN_TIME_FACTOR - MAX_TIME_FACTOR;
-	if (days2 > -days_over_max) days_over_max += transit_days - days1;
-	else days_over_max += 2 * (transit_days - days1) - days2;
+	int days_over_max = 0;
+	if (_settings_game.economy.payment_algorithm == CPA_MODERN) {
+		days_over_max = MIN_TIME_FACTOR - MAX_TIME_FACTOR;
+		if (days2 > -days_over_max) days_over_max += transit_days - days1;
+		else days_over_max += 2 * (transit_days - days1) - days2;
+	}
 
 	/*
 	 * The time factor is calculated based on the time it took

src/economy_type.h

@@ -234,4 +234,11 @@ static const uint LOCK_DEPOT_TILE_FACTOR = 2;
 struct CargoPayment;
 typedef uint32 CargoPaymentID;
 
+enum CargoPaymentAlgorithm : byte {
+	CPA_BEGIN = 0,       ///< Used for iterations and limit testing
+	CPA_TRADITIONAL = 0, ///< Traditional algorithm
+	CPA_MODERN,          ///< Modern algorithm
+	CPA_END,             ///< Used for iterations and limit testing
+};
+
 #endif /* ECONOMY_TYPE_H */

src/lang/extra/english.txt

@@ -606,6 +606,11 @@ STR_CONFIG_SETTING_TOWN_GROWTH_CARGO_TRANSPORTED_HELPTEXT       :Percentage of t
 STR_CONFIG_SETTING_RANDOM_ROAD_RECONSTRUCTION                   :Probability of random town road re-construction: {STRING2}
 STR_CONFIG_SETTING_RANDOM_ROAD_RECONSTRUCTION_HELPTEXT          :The probability of town roads randomly being re-constructed (0 = off, 1000 = max)
 
+STR_CONFIG_SETTING_CARGO_PAYMENT_ALGORITHM                      :Cargo payment algorithm: {STRING2}
+STR_CONFIG_SETTING_CARGO_PAYMENT_ALGORITHM_HELPTEXT             :The algorithm to use to calculate how much money to pay for delivering cargo to its destination.
+STR_CONFIG_SETTING_CARGO_PAYMENT_ALGORITHM_TRADITIONAL          :Traditional
+STR_CONFIG_SETTING_CARGO_PAYMENT_ALGORITHM_MODERN               :Modern
+
 STR_CONFIG_SETTING_TOWN_MIN_DISTANCE                            :Minimum distance between towns: {STRING2}
 STR_CONFIG_SETTING_TOWN_MIN_DISTANCE_HELPTEXT                   :Set the minimum distance in tiles between towns for map generation and random founding
 

src/saveload/afterload.cpp

@@ -4187,6 +4187,10 @@ bool AfterLoadGame()
 		}
 	}
 
+	if (SlXvIsFeatureMissing(XSLFI_MORE_CARGO_AGE) && IsSavegameVersionBefore(SLV_MORE_CARGO_AGE)) {
+		_settings_game.economy.payment_algorithm = CPA_TRADITIONAL;
+	}
+
 	InitializeRoadGUI();
 
 	/* This needs to be done after conversion. */

src/settings_gui.cpp

@@ -2061,6 +2061,7 @@ static SettingsContainer &GetSettingsTree()
 			accounting->Add(new SettingEntry("difficulty.vehicle_costs_in_depot"));
 			accounting->Add(new SettingEntry("difficulty.vehicle_costs_when_stopped"));
 			accounting->Add(new SettingEntry("difficulty.construction_cost"));
+			accounting->Add(new SettingEntry("economy.payment_algorithm"));
 		}
 
 		SettingsPage *vehicles = main->Add(new SettingsPage(STR_CONFIG_SETTING_VEHICLES));

src/settings_type.h

@@ -705,6 +705,7 @@ struct EconomySettings {
 	uint8  day_length_factor;                ///< factor which the length of day is multiplied
 	uint16 random_road_reconstruction;       ///< chance out of 1000 per tile loop for towns to start random road re-construction
 	bool disable_inflation_newgrf_flag;      ///< Disable NewGRF inflation flag
+	CargoPaymentAlgorithm payment_algorithm; ///< Cargo payment algorithm
 };
 
 struct LinkGraphSettings {

src/table/settings/settings.ini

@@ -3237,6 +3237,20 @@ def      = false
 cat      = SC_EXPERT
 patxname = ""economy.disable_inflation_newgrf_flag""
 
+[SDT_VAR]
+var      = economy.payment_algorithm
+type     = SLE_UINT8
+flags    = SF_GUI_DROPDOWN
+def      = CPA_MODERN
+min      = CPA_BEGIN
+max      = CPA_END - 1
+interval = 1
+str      = STR_CONFIG_SETTING_CARGO_PAYMENT_ALGORITHM
+strhelp  = STR_CONFIG_SETTING_CARGO_PAYMENT_ALGORITHM_HELPTEXT
+strval   = STR_CONFIG_SETTING_CARGO_PAYMENT_ALGORITHM_TRADITIONAL
+cat      = SC_BASIC
+patxname = ""economy.payment_algorithm""
+
 ##
 [SDT_VAR]
 var      = pf.wait_for_pbs_path