Add setting for inflation dates mode

src/economy.cpp

@@ -768,7 +768,11 @@ bool AddInflation(bool check_year)
 	 * inflation doesn't add anything after that either; it even makes playing
 	 * it impossible due to the diverging cost and income rates.
 	 */
-	if (check_year && (_cur_year < ORIGINAL_BASE_YEAR || _cur_year >= ORIGINAL_MAX_YEAR)) return true;
+	if (_settings_game.economy.inflation_fixed_dates) {
+		if (check_year && (_cur_year < ORIGINAL_BASE_YEAR || _cur_year >= ORIGINAL_MAX_YEAR)) return true;
+	} else {
+		if (check_year && (_cur_year - _settings_game.game_creation.starting_year) >= (ORIGINAL_MAX_YEAR - ORIGINAL_BASE_YEAR)) return true;
+	}
 
 	if (_economy.inflation_prices == MAX_INFLATION || _economy.inflation_payment == MAX_INFLATION) return true;
 
@@ -960,7 +964,7 @@ void StartupEconomy()
 	_economy.infl_amount_pr = max(0, _settings_game.difficulty.initial_interest - 1);
 	_economy.fluct = GB(Random(), 0, 8) + 168;
 
-	if (_settings_game.economy.inflation) {
+	if (_settings_game.economy.inflation && _settings_game.economy.inflation_fixed_dates) {
 		/* Apply inflation that happened before our game start year. */
 		int months = (min(_cur_year, ORIGINAL_MAX_YEAR) - ORIGINAL_BASE_YEAR) * 12;
 		for (int i = 0; i < months; i++) {

src/lang/english.txt

@@ -1248,6 +1248,8 @@ STR_CONFIG_SETTING_DISTANT_JOIN_STATIONS                        :Allow to join s
 STR_CONFIG_SETTING_DISTANT_JOIN_STATIONS_HELPTEXT               :Allow adding parts to a station without directly touching the existing parts. Needs Ctrl+Click while placing the new parts
 STR_CONFIG_SETTING_INFLATION                                    :Inflation: {STRING2}
 STR_CONFIG_SETTING_INFLATION_HELPTEXT                           :Enable inflation in the economy, where costs are slightly faster rising than payments
+STR_CONFIG_SETTING_INFLATION_FIXED_DATES                        :Apply inflation from 1920 to 2090: {STRING2}
+STR_CONFIG_SETTING_INFLATION_FIXED_DATES_HELPTEXT               :If enabled, inflation is always applied from 1920 to 2090, regardless of the game start date. This is the inflation model used since OpenTTD 1.11.{}If disabled, inflation is applied from the game start date for 170 years. This is the inflation model used until OpenTTD 1.10.
 STR_CONFIG_SETTING_MAX_BRIDGE_LENGTH                            :Maximum bridge length: {STRING2}
 STR_CONFIG_SETTING_MAX_BRIDGE_LENGTH_HELPTEXT                   :Maximum length for building bridges
 STR_CONFIG_SETTING_MAX_BRIDGE_HEIGHT                            :Maximum bridge height: {STRING2}

src/saveload/afterload.cpp

@@ -3831,6 +3831,10 @@ bool AfterLoadGame()
 		UpdateAllAnimatedTileSpeeds();
 	}
 
+	if (SlXvIsFeatureMissing(XSLFI_INFLATION_FIXED_DATES)) {
+		_settings_game.economy.inflation_fixed_dates = !IsSavegameVersionBefore(SLV_GS_INDUSTRY_CONTROL);
+	}
+
 	InitializeRoadGUI();
 
 	/* This needs to be done after conversion. */

src/saveload/extended_ver_sl.cpp

@@ -144,6 +144,7 @@ const SlxiSubChunkInfo _sl_xv_sub_chunk_infos[] = {
 	{ XSLFI_NEWGRF_INFO_EXTRA,      XSCF_NULL,                1,   1, "newgrf_info_extra",         nullptr, nullptr, nullptr        },
 	{ XSLFI_INDUSTRY_CARGO_ADJ,     XSCF_IGNORABLE_UNKNOWN,   1,   1, "industry_cargo_adj",        nullptr, nullptr, nullptr        },
 	{ XSLFI_REALISTIC_TRAIN_BRAKING,XSCF_NULL,                1,   1, "realistic_train_braking",   nullptr, nullptr, "VLKA"         },
+	{ XSLFI_INFLATION_FIXED_DATES,  XSCF_IGNORABLE_ALL,       1,   1, "inflation_fixed_dates",     nullptr, nullptr, nullptr        },
 	{ XSLFI_NULL, XSCF_NULL, 0, 0, nullptr, nullptr, nullptr, nullptr },// This is the end marker
 };
 

src/saveload/extended_ver_sl.h

@@ -98,6 +98,7 @@ enum SlXvFeatureIndex {
 	XSLFI_NEWGRF_INFO_EXTRA,                      ///< Extra NewGRF info in savegame
 	XSLFI_INDUSTRY_CARGO_ADJ,                     ///< Industry cargo adjustment patch
 	XSLFI_REALISTIC_TRAIN_BRAKING,                ///< Realistic train braking
+	XSLFI_INFLATION_FIXED_DATES,                  ///< Inflation is applied between fixed dates
 
 	XSLFI_RIFF_HEADER_60_BIT,                     ///< Size field in RIFF chunk header is 60 bit
 	XSLFI_HEIGHT_8_BIT,                           ///< Map tile height is 8 bit instead of 4 bit, but savegame version may be before this became true in trunk

src/settings_gui.cpp

@@ -1798,6 +1798,7 @@ static SettingsContainer &GetSettingsTree()
 		SettingsPage *accounting = main->Add(new SettingsPage(STR_CONFIG_SETTING_ACCOUNTING));
 		{
 			accounting->Add(new SettingEntry("economy.inflation"));
+			accounting->Add(new SettingEntry("economy.inflation_fixed_dates"));
 			accounting->Add(new SettingEntry("economy.day_length_factor"));
 			accounting->Add(new SettingEntry("difficulty.initial_interest"));
 			accounting->Add(new SettingEntry("difficulty.max_loan"));

src/settings_type.h

@@ -571,6 +571,7 @@ struct VehicleSettings {
 /** Settings related to the economy. */
 struct EconomySettings {
 	bool   inflation;                        ///< disable inflation
+	bool   inflation_fixed_dates;            ///< whether inflation is applied between fixed dates
 	bool   bribe;                            ///< enable bribing the local authority
 	EconomyType type;                        ///< economy type (original/smooth/frozen)
 	bool   allow_shares;                     ///< allow the buying/selling of shares

src/table/settings.ini

@@ -2029,6 +2029,14 @@ str      = STR_CONFIG_SETTING_INFLATION
 strhelp  = STR_CONFIG_SETTING_INFLATION_HELPTEXT
 cat      = SC_BASIC
 
+[SDT_BOOL]
+base     = GameSettings
+var      = economy.inflation_fixed_dates
+def      = true
+str      = STR_CONFIG_SETTING_INFLATION_FIXED_DATES
+strhelp  = STR_CONFIG_SETTING_INFLATION_FIXED_DATES_HELPTEXT
+patxname = ""inflation_fixed_dates.economy.inflation_fixed_dates""
+
 [SDT_VAR]
 base     = GameSettings
 var      = economy.day_length_factor