Store state ticks directly in savegame instead of the offset

Initialise the state ticks value to a constant for new games,
instead of using an implicit offset of 0

src/date.cpp

@@ -33,7 +33,7 @@ uint64_t _tick_counter;                    ///< Ever incrementing tick counter f
 uint8_t _tick_skip_counter;                ///< Counter for ticks, when only vehicles are moving and nothing else happens
 uint64_t _scaled_tick_counter;             ///< Tick counter in daylength-scaled ticks
 StateTicks _state_ticks;                   ///< Current state tick
-StateTicks _state_ticks_offset;            ///< Offset to add when calculating a StateTicks value from a date/date fract/tick skip counter
+StateTicksDelta _state_ticks_offset;       ///< Offset to add when calculating a StateTicks value from a date/date fract/tick skip counter
 uint32_t    _quit_after_days;              ///< Quit after this many days of run time
 
 YearMonthDay _game_load_cur_date_ymd;
@@ -45,14 +45,14 @@ extern void ClearOutOfDateSignalSpeedRestrictions();
 void CheckStateTicksWrap()
 {
 	StateTicksDelta tick_adjust = 0;
-	auto get_tick_adjust = [&](StateTicks target) {
+	auto get_tick_adjust = [&](StateTicksDelta target) {
 		int32_t rounding = _settings_time.time_in_minutes * 1440;
-		return target.AsDelta() - (target.base() % rounding);
+		return target - (target.base() % rounding);
 	};
 	if (_state_ticks >= ((int64_t)1 << 60)) {
-		tick_adjust = get_tick_adjust(_state_ticks);
+		tick_adjust = get_tick_adjust(_state_ticks - INITIAL_STATE_TICKS_VALUE);
 	} else if (_state_ticks <= -((int64_t)1 << 60)) {
-		tick_adjust = -get_tick_adjust(-(_state_ticks.base()));
+		tick_adjust = -get_tick_adjust(INITIAL_STATE_TICKS_VALUE - _state_ticks);
 	} else {
 		return;
 	}
@@ -70,23 +70,12 @@ void CheckStateTicksWrap()
 	AdjustLinkGraphStateTicksBase(-tick_adjust);
 }
 
-void RebaseStateTicksBase()
-{
-	StateTicks old_state_ticks = _state_ticks;
-	SetScaledTickVariables();
-	_state_ticks_offset += (old_state_ticks - _state_ticks);
-	SetScaledTickVariables();
-	assert(old_state_ticks == _state_ticks);
-
-	CheckStateTicksWrap();
-}
-
 /**
  * Set the date.
  * @param date  New date
  * @param fract The number of ticks that have passed on this date.
  */
-void SetDate(Date date, DateFract fract, bool preserve_state_tick)
+void SetDate(Date date, DateFract fract)
 {
 	assert(fract < DAY_TICKS);
 
@@ -94,17 +83,18 @@ void SetDate(Date date, DateFract fract, bool preserve_state_tick)
 	_date_fract = fract;
 	YearMonthDay ymd = ConvertDateToYMD(date);
 	_cur_date_ymd = ymd;
-	if (preserve_state_tick) {
+	RecalculateStateTicksOffset();
-		RebaseStateTicksBase();
-	} else {
-		SetScaledTickVariables();
-	}
 	UpdateCachedSnowLine();
 }
 
-void SetScaledTickVariables()
+StateTicks GetStateTicksFromCurrentDateWithoutOffset()
+{
+	return ((int64_t)(DateToDateTicks(_date, _date_fract).base()) * _settings_game.economy.day_length_factor) + _tick_skip_counter;
+}
+
+void RecalculateStateTicksOffset()
 {
-	_state_ticks = ((int64_t)(DateToDateTicks(_date, _date_fract).base()) * _settings_game.economy.day_length_factor) + _tick_skip_counter + _state_ticks_offset;
+	_state_ticks_offset = _state_ticks - GetStateTicksFromCurrentDateWithoutOffset();
 }
 
 #define M(a, b) ((a << 5) | b)
@@ -270,7 +260,7 @@ static void OnNewYear()
 		LinkGraphSchedule::instance.ShiftDates(-days_this_year);
 		ShiftOrderDates(-days_this_year);
 		ShiftVehicleDates(-days_this_year);
-		_state_ticks_offset += ((int64_t)days_this_year) * (DAY_TICKS * _settings_game.economy.day_length_factor);
+		RecalculateStateTicksOffset();
 
 		/* Because the _date wraps here, and text-messages expire by game-days, we have to clean out
 		 *  all of them if the date is set back, else those messages will hang for ever */

src/date_func.h

@@ -21,17 +21,18 @@ extern uint64_t  _tick_counter;
 extern uint8_t   _tick_skip_counter;
 extern uint64_t  _scaled_tick_counter;
 extern StateTicks _state_ticks;
-extern StateTicks _state_ticks_offset;
+extern StateTicksDelta _state_ticks_offset;
 extern uint32_t  _quit_after_days;
 
 extern YearMonthDay _game_load_cur_date_ymd;
 extern DateFract _game_load_date_fract;
 extern uint8_t _game_load_tick_skip_counter;
 
-void SetDate(Date date, DateFract fract, bool preserve_scaled_ticks = true);
+void SetDate(Date date, DateFract fract);
 YearMonthDay ConvertDateToYMD(Date date);
 Date ConvertYMDToDate(Year year, Month month, Day day);
-void SetScaledTickVariables();
+StateTicks GetStateTicksFromCurrentDateWithoutOffset();
+void RecalculateStateTicksOffset();
 
 inline Date ConvertYMDToDate(const YearMonthDay &ymd)
 {

src/date_type.h

@@ -200,6 +200,9 @@ static const Year MAX_YEAR  = 5000000;
 /** The number of days till the last day */
 static constexpr Date MAX_DATE = DateAtStartOfYear(MAX_YEAR + 1) - 1;
 
+/** An initial value for StateTicks when starting a new game */
+static constexpr StateTicks INITIAL_STATE_TICKS_VALUE = 1 << 24;
+
 /**
  * Data structure to convert between Date and triplet (year, month, and day).
  * @see ConvertDateToYMD(), ConvertYMDToDate()

src/misc.cpp

@@ -131,6 +131,7 @@ void InitializeGame(uint size_x, uint size_y, bool reset_date, bool reset_settin
 	_tick_counter = 0;
 	_tick_skip_counter = 0;
 	_scaled_tick_counter = 0;
+	_state_ticks = INITIAL_STATE_TICKS_VALUE;
 	_state_ticks_offset = 0;
 	_cur_tileloop_tile = 1;
 	_aux_tileloop_tile = 1;
@@ -153,10 +154,10 @@ void InitializeGame(uint size_x, uint size_y, bool reset_date, bool reset_settin
 	_newgrf_profilers.clear();
 
 	if (reset_date) {
-		SetDate(ConvertYMDToDate(_settings_game.game_creation.starting_year, 0, 1), 0, false);
+		SetDate(ConvertYMDToDate(_settings_game.game_creation.starting_year, 0, 1), 0);
 		InitializeOldNames();
 	} else {
-		SetScaledTickVariables();
+		RecalculateStateTicksOffset();
 	}
 	SetupTileLoopCounts();
 	UpdateCargoScalers();

src/newgrf.cpp

@@ -11605,7 +11605,8 @@ void LoadNewGRF(uint load_index, uint num_baseset)
 	uint64_t tick_counter  = _tick_counter;
 	uint8_t tick_skip_counter = _tick_skip_counter;
 	uint64_t scaled_tick_counter = _scaled_tick_counter;
-	StateTicks state_ticks_offset = _state_ticks_offset;
+	StateTicks state_ticks = _state_ticks;
+	StateTicksDelta state_ticks_offset = _state_ticks_offset;
 	byte display_opt     = _display_opt;
 
 	if (_networking) {
@@ -11615,10 +11616,10 @@ void LoadNewGRF(uint load_index, uint num_baseset)
 		_tick_counter = 0;
 		_tick_skip_counter = 0;
 		_scaled_tick_counter = 0;
-		_state_ticks_offset = 0;
+		_state_ticks = 0;
 		_display_opt  = 0;
 		UpdateCachedSnowLine();
-		SetScaledTickVariables();
+		RecalculateStateTicksOffset();
 	}
 
 	InitializeGRFSpecial();
@@ -11722,10 +11723,10 @@ void LoadNewGRF(uint load_index, uint num_baseset)
 	_tick_counter = tick_counter;
 	_tick_skip_counter = tick_skip_counter;
 	_scaled_tick_counter = scaled_tick_counter;
+	_state_ticks = state_ticks;
 	_state_ticks_offset = state_ticks_offset;
 	_display_opt  = display_opt;
 	UpdateCachedSnowLine();
-	SetScaledTickVariables();
 }
 
 /**

src/openttd.cpp

@@ -2149,7 +2149,7 @@ void StateGameLoop()
 		_tick_skip_counter++;
 		_scaled_tick_counter++;
 		if (_game_mode != GM_MENU && _game_mode != GM_BOOTSTRAP) {
-			_state_ticks++;   // This must update in lock-step with _tick_skip_counter, such that it always matches what SetScaledTickVariables would return.
+			_state_ticks++;   // This must update in lock-step with _tick_skip_counter, such that _state_ticks_offset doesn't need to be changed.
 		}
 
 		if (!(_game_mode == GM_MENU || _game_mode == GM_BOOTSTRAP) && !_settings_client.gui.autosave_realtime &&

src/saveload/afterload.cpp

@@ -862,10 +862,13 @@ bool AfterLoadGame()
 	if (SlXvIsFeatureMissing(XSLFI_VARIABLE_DAY_LENGTH, 3)) {
 		_scaled_tick_counter = (uint64_t)((_tick_counter * _settings_game.economy.day_length_factor) + _tick_skip_counter);
 	}
+	if (SlXvIsFeaturePresent(XSLFI_VARIABLE_DAY_LENGTH, 1, 3)) {
+		_state_ticks = GetStateTicksFromCurrentDateWithoutOffset() + _state_ticks_offset;
+	}
 
 	/* Update current year
 	 * must be done before loading sprites as some newgrfs check it */
-	SetDate(_date, _date_fract, false);
+	SetDate(_date, _date_fract);
 	SetupTileLoopCounts();
 
 	/*
@@ -1796,7 +1799,7 @@ bool AfterLoadGame()
 	 * Account for this in older games by adding an offset */
 	if (IsSavegameVersionBefore(SLV_31)) {
 		_date += DAYS_TILL_ORIGINAL_BASE_YEAR.AsDelta();
-		SetScaledTickVariables();
+		RecalculateStateTicksOffset();
 		_cur_date_ymd = ConvertDateToYMD(_date);
 		UpdateCachedSnowLine();
 

src/settings.cpp

@@ -1850,8 +1850,7 @@ static bool DayLengthPreChange(int32_t &new_value)
 
 static void DayLengthChanged(int32_t new_value)
 {
-	extern void RebaseStateTicksBase();
+	RecalculateStateTicksOffset();
-	RebaseStateTicksBase();
 
 	SetupTileLoopCounts();
 	UpdateCargoScalers();

src/sl/extended_ver_sl.cpp

@@ -103,7 +103,7 @@ const SlxiSubChunkInfo _sl_xv_sub_chunk_infos[] = {
 	{ XSLFI_VEHICLE_REPAIR_COST,              XSCF_NULL,                2,   2, "vehicle_repair_cost",              nullptr, nullptr, nullptr          },
 	{ XSLFI_ENH_VIEWPORT_PLANS,               XSCF_IGNORABLE_ALL,       4,   4, "enh_viewport_plans",               nullptr, nullptr, "PLAN"           },
 	{ XSLFI_INFRA_SHARING,                    XSCF_NULL,                2,   2, "infra_sharing",                    nullptr, nullptr, "CPDP"           },
-	{ XSLFI_VARIABLE_DAY_LENGTH,              XSCF_NULL,                3,   3, "variable_day_length",              nullptr, nullptr, nullptr          },
+	{ XSLFI_VARIABLE_DAY_LENGTH,              XSCF_NULL,                4,   4, "variable_day_length",              nullptr, nullptr, nullptr          },
 	{ XSLFI_ORDER_OCCUPANCY,                  XSCF_NULL,                2,   2, "order_occupancy",                  nullptr, nullptr, nullptr          },
 	{ XSLFI_MORE_COND_ORDERS,                 XSCF_NULL,               17,  17, "more_cond_orders",                 nullptr, nullptr, nullptr          },
 	{ XSLFI_EXTRA_LARGE_MAP,                  XSCF_NULL,                0,   1, "extra_large_map",                  nullptr, nullptr, nullptr          },

src/sl/misc_sl.cpp

@@ -91,7 +91,8 @@ static const SaveLoad _date_desc[] = {
 	SLEG_CONDVAR_X(_tick_counter,         SLE_UINT64,                  SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_U64_TICK_COUNTER)),
 	SLEG_CONDVAR_X(_tick_skip_counter,    SLE_UINT8,                   SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_VARIABLE_DAY_LENGTH)),
 	SLEG_CONDVAR_X(_scaled_tick_counter,  SLE_UINT64,                  SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_VARIABLE_DAY_LENGTH, 3)),
-	SLEG_CONDVAR_X(_state_ticks_offset,   SLE_INT64,                   SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_VARIABLE_DAY_LENGTH, 3)),
+	SLEG_CONDVAR_X(_state_ticks_offset,   SLE_INT64,                   SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_VARIABLE_DAY_LENGTH, 3, 3)),
+	SLEG_CONDVAR_X(_state_ticks,          SLE_INT64,                   SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_VARIABLE_DAY_LENGTH, 4)),
 	SLE_CONDNULL(2, SL_MIN_VERSION, SLV_157), // _vehicle_id_ctr_day
 	SLEG_CONDVAR(_age_cargo_skip_counter, SLE_UINT8,                   SL_MIN_VERSION, SLV_162),
 	SLE_CONDNULL(1, SL_MIN_VERSION, SLV_46),
@@ -128,7 +129,8 @@ static const SaveLoad _date_check_desc[] = {
 	SLE_CONDNULL_X(8, SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_U64_TICK_COUNTER)),       // _tick_counter
 	SLE_CONDNULL_X(1, SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_VARIABLE_DAY_LENGTH)), // _tick_skip_counter
 	SLE_CONDNULL_X(8, SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_VARIABLE_DAY_LENGTH, 3)), // _scaled_tick_counter
-	SLE_CONDNULL_X(8, SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_VARIABLE_DAY_LENGTH, 3)), // _state_ticks_offset
+	SLE_CONDNULL_X(8, SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_VARIABLE_DAY_LENGTH, 3, 3)), // _state_ticks_offset
+	SLE_CONDNULL_X(8, SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_VARIABLE_DAY_LENGTH, 4)), // _state_ticks
 	SLE_CONDNULL(2, SL_MIN_VERSION, SLV_157),               // _vehicle_id_ctr_day
 	SLE_CONDNULL(1, SL_MIN_VERSION, SLV_162),               // _age_cargo_skip_counter
 	SLE_CONDNULL(1, SL_MIN_VERSION, SLV_46),
@@ -160,7 +162,6 @@ static const SaveLoad _date_check_desc[] = {
 static void SaveLoad_DATE()
 {
 	SlGlobList(_date_desc);
-	SetScaledTickVariables();
 }
 
 static void Check_DATE()