Change: Switch town growth rate and counter to actual game ticks (#6763)

8 files changed, 68 insertions, 37 deletions

diff --git a/src/newgrf_town.cpp b/src/newgrf_town.cpp
index 820e2be68..00fcf76b6 100644
--- a/src/newgrf_town.cpp
+++ b/src/newgrf_town.cpp
@@ -50,7 +50,7 @@
 		case 0x81: return GB(this->t->xy, 8, 8);
 		case 0x82: return ClampToU16(this->t->cache.population);
 		case 0x83: return GB(ClampToU16(this->t->cache.population), 8, 8);
-		case 0x8A: return this->t->grow_counter;
+		case 0x8A: return this->t->grow_counter / TOWN_GROWTH_TICKS;
 		case 0x92: return this->t->flags;  // In original game, 0x92 and 0x93 are really one word. Since flags is a byte, this is to adjust
 		case 0x93: return 0;
 		case 0x94: return ClampToU16(this->t->cache.squared_town_zone_radius[0]);
@@ -82,7 +82,7 @@
 		case 0xAE: return this->t->have_ratings;
 		case 0xB2: return this->t->statues;
 		case 0xB6: return ClampToU16(this->t->cache.num_houses);
-		case 0xB9: return this->t->growth_rate & (~TOWN_GROW_RATE_CUSTOM);
+		case 0xB9: return this->t->growth_rate / TOWN_GROWTH_TICKS;
 		case 0xBA: return ClampToU16(this->t->supplied[CT_PASSENGERS].new_max);
 		case 0xBB: return GB(ClampToU16(this->t->supplied[CT_PASSENGERS].new_max), 8, 8);
 		case 0xBC: return ClampToU16(this->t->supplied[CT_MAIL].new_max);
diff --git a/src/saveload/afterload.cpp b/src/saveload/afterload.cpp
index f01afb425..33c49fb61 100644
--- a/src/saveload/afterload.cpp
+++ b/src/saveload/afterload.cpp
@@ -2969,6 +2969,19 @@ bool AfterLoadGame()
 #endif
 	}
 
+	if (IsSavegameVersionBefore(198)) {
+		/* Convert towns growth_rate and grow_counter to ticks */
+		Town *t;
+		FOR_ALL_TOWNS(t) {
+			/* 0x8000 = TOWN_GROWTH_RATE_CUSTOM previously */
+			if (t->growth_rate & 0x8000) SetBit(t->flags, TOWN_CUSTOM_GROWTH);
+			if (t->growth_rate != TOWN_GROWTH_RATE_NONE) {
+				t->growth_rate = TownTicksToGameTicks(t->growth_rate & ~0x8000);
+			}
+			/* Add t->index % TOWN_GROWTH_TICKS to spread growth across ticks. */
+			t->grow_counter = TownTicksToGameTicks(t->grow_counter) + t->index % TOWN_GROWTH_TICKS;
+		}
+	}
 
 	/* Station acceptance is some kind of cache */
 	if (IsSavegameVersionBefore(127)) {
diff --git a/src/saveload/saveload.cpp b/src/saveload/saveload.cpp
index cea80b59d..d06214e23 100644
--- a/src/saveload/saveload.cpp
+++ b/src/saveload/saveload.cpp
@@ -265,8 +265,9 @@
  *  195   27572   1.6.x
  *  196   27778   1.7.x
  *  197   27978   1.8.x
+ *  198
  */
-extern const uint16 SAVEGAME_VERSION = 197; ///< Current savegame version of OpenTTD.
+extern const uint16 SAVEGAME_VERSION = 198; ///< Current savegame version of OpenTTD.
 
 SavegameType _savegame_type; ///< type of savegame we are loading
 FileToSaveLoad _file_to_saveload; ///< File to save or load in the openttd loop.
diff --git a/src/script/api/script_town.cpp b/src/script/api/script_town.cpp
index d81704ae3..4cdd6a9d0 100644
--- a/src/script/api/script_town.cpp
+++ b/src/script/api/script_town.cpp
@@ -159,24 +159,24 @@
 /* static */ bool ScriptTown::SetGrowthRate(TownID town_id, uint32 days_between_town_growth)
 {
 	EnforcePrecondition(false, IsValidTown(town_id));
-
+	uint16 growth_rate;
 	switch (days_between_town_growth) {
 		case TOWN_GROWTH_NORMAL:
-			days_between_town_growth = 0;
+			growth_rate = 0;
 			break;
 
 		case TOWN_GROWTH_NONE:
-			days_between_town_growth = TOWN_GROW_RATE_CUSTOM_NONE;
+			growth_rate = TOWN_GROWTH_RATE_NONE;
 			break;
 
 		default:
-			days_between_town_growth = days_between_town_growth * DAY_TICKS / TOWN_GROWTH_TICKS;
-			EnforcePrecondition(false, days_between_town_growth < TOWN_GROW_RATE_CUSTOM);
-			if (days_between_town_growth == 0) days_between_town_growth = 1; // as fast as possible
+			EnforcePrecondition(false, days_between_town_growth <= MAX_TOWN_GROWTH_TICKS);
+			/* Don't use growth_rate 0 as it means GROWTH_NORMAL */
+			growth_rate = max(days_between_town_growth * DAY_TICKS, 2u) - 1;
 			break;
 	}
 
-	return ScriptObject::DoCommand(::Town::Get(town_id)->xy, town_id, days_between_town_growth, CMD_TOWN_GROWTH_RATE);
+	return ScriptObject::DoCommand(::Town::Get(town_id)->xy, town_id, growth_rate, CMD_TOWN_GROWTH_RATE);
 }
 
 /* static */ int32 ScriptTown::GetGrowthRate(TownID town_id)
@@ -185,9 +185,9 @@
 
 	const Town *t = ::Town::Get(town_id);
 
-	if (t->growth_rate == TOWN_GROW_RATE_CUSTOM_NONE) return TOWN_GROWTH_NONE;
+	if (t->growth_rate == TOWN_GROWTH_RATE_NONE) return TOWN_GROWTH_NONE;
 
-	return ((t->growth_rate & ~TOWN_GROW_RATE_CUSTOM) * TOWN_GROWTH_TICKS + DAY_TICKS) / DAY_TICKS;
+	return RoundDivSU(t->growth_rate + 1, DAY_TICKS);
 }
 
 /* static */ int32 ScriptTown::GetDistanceManhattanToTile(TownID town_id, TileIndex tile)
diff --git a/src/script/api/script_town.hpp b/src/script/api/script_town.hpp
index 03868e67a..7fdf8a6b3 100644
--- a/src/script/api/script_town.hpp
+++ b/src/script/api/script_town.hpp
@@ -259,7 +259,7 @@ public:
 	 * @param town_id The index of the town.
 	 * @param days_between_town_growth The amount of days between town growth, TOWN_GROWTH_NONE or TOWN_GROWTH_NORMAL.
 	 * @pre IsValidTown(town_id).
-	 * @pre days_between_town_growth <= 30000 || days_between_town_growth == TOWN_GROWTH_NONE || days_between_town_growth == TOWN_GROWTH_NORMAL.
+	 * @pre days_between_town_growth <= 880 || days_between_town_growth == TOWN_GROWTH_NONE || days_between_town_growth == TOWN_GROWTH_NORMAL.
 	 * @return True if the action succeeded.
 	 * @note Even when setting a growth rate, towns only grow when the conditions for growth (SetCargoCoal) are met,
 	 *       and the game settings (economy.town_growth_rate) allow town growth at all.
diff --git a/src/town.h b/src/town.h
index 010c7c216..75deb7cca 100644
--- a/src/town.h
+++ b/src/town.h
@@ -35,8 +35,8 @@ static const uint INVALID_TOWN = 0xFFFF;
 
 static const uint TOWN_GROWTH_WINTER = 0xFFFFFFFE; ///< The town only needs this cargo in the winter (any amount)
 static const uint TOWN_GROWTH_DESERT = 0xFFFFFFFF; ///< The town needs the cargo for growth when on desert (any amount)
-static const uint16 TOWN_GROW_RATE_CUSTOM      = 0x8000; ///< If this mask is applied to Town::growth_rate, the grow_counter will not be calculated by the system (but assumed to be set by scripts)
-static const uint16 TOWN_GROW_RATE_CUSTOM_NONE = 0xFFFF; ///< Special value for Town::growth_rate to disable town growth.
+static const uint16 TOWN_GROWTH_RATE_NONE = 0xFFFF; ///< Special value for Town::growth_rate to disable town growth.
+static const uint16 MAX_TOWN_GROWTH_TICKS = 930; ///< Max amount of original town ticks that still fit into uint16, about equal to UINT16_MAX / TOWN_GROWTH_TICKS but sligtly less to simplify calculations
 
 typedef Pool<Town, TownID, 64, 64000> TownPool;
 extern TownPool _town_pool;
@@ -165,6 +165,7 @@ enum TownFlags {
 	TOWN_IS_GROWING     = 0,   ///< Conditions for town growth are met. Grow according to Town::growth_rate.
 	TOWN_HAS_CHURCH     = 1,   ///< There can be only one church by town.
 	TOWN_HAS_STADIUM    = 2,   ///< There can be only one stadium by town.
+	TOWN_CUSTOM_GROWTH  = 3,   ///< Growth rate is controlled by GS.
 };
 
 CommandCost CheckforTownRating(DoCommandFlag flags, Town *t, TownRatingCheckType type);
@@ -194,7 +195,6 @@ uint GetMaskOfTownActions(int *nump, CompanyID cid, const Town *t);
 bool GenerateTowns(TownLayout layout);
 const CargoSpec *FindFirstCargoWithTownEffect(TownEffect effect);
 
-
 /** Town actions of a company. */
 enum TownActions {
 	TACT_NONE             = 0x00, ///< Empty action set.
@@ -284,6 +284,15 @@ void MakeDefaultName(T *obj)
 	obj->town_cn = (uint16)next; // set index...
 }
 
+/*
+ * Converts original town ticks counters to plain game ticks. Note that
+ * tick 0 is a valid tick so actual amount is one more than the counter value.
+ */
+static inline uint16 TownTicksToGameTicks(uint16 ticks) {
+	return (min(ticks, MAX_TOWN_GROWTH_TICKS) + 1) * TOWN_GROWTH_TICKS - 1;
+}
+
+
 extern uint32 _town_cargoes_accepted;
 
 #endif /* TOWN_H */
diff --git a/src/town_cmd.cpp b/src/town_cmd.cpp
index 5973dfbc1..0001de00d 100644
--- a/src/town_cmd.cpp
+++ b/src/town_cmd.cpp
@@ -780,12 +780,13 @@ static bool GrowTown(Town *t);
 static void TownTickHandler(Town *t)
 {
 	if (HasBit(t->flags, TOWN_IS_GROWING)) {
-		int i = t->grow_counter - 1;
+		int i = (int)t->grow_counter - 1;
 		if (i < 0) {
 			if (GrowTown(t)) {
-				i = t->growth_rate & (~TOWN_GROW_RATE_CUSTOM);
+				i = t->growth_rate;
 			} else {
-				i = 0;
+				/* If growth failed wait a bit before retrying */
+				i = min(t->growth_rate, TOWN_GROWTH_TICKS - 1);
 			}
 		}
 		t->grow_counter = i;
@@ -798,10 +799,7 @@ void OnTick_Town()
 
 	Town *t;
 	FOR_ALL_TOWNS(t) {
-		/* Run town tick at regular intervals, but not all at once. */
-		if ((_tick_counter + t->index) % TOWN_GROWTH_TICKS == 0) {
-			TownTickHandler(t);
-		}
+		TownTickHandler(t);
 	}
 }
 
@@ -1596,8 +1594,10 @@ static void DoCreateTown(Town *t, TileIndex tile, uint32 townnameparts, TownSize
 	UpdateTownRadius(t);
 	t->flags = 0;
 	t->cache.population = 0;
-	t->grow_counter = 0;
-	t->growth_rate = 250;
+	/* Spread growth across ticks so even if there are many
+	 * similar towns they're unlikely to grow all in one tick */
+	t->grow_counter = t->index % TOWN_GROWTH_TICKS;
+	t->growth_rate = TownTicksToGameTicks(250);
 
 	/* Set the default cargo requirement for town growth */
 	switch (_settings_game.game_creation.landscape) {
@@ -2613,14 +2613,13 @@ CommandCost CmdTownSetText(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
  * @param tile Unused.
  * @param flags Type of operation.
  * @param p1 Town ID to cargo game of.
- * @param p2 Amount of days between growth, or TOWN_GROW_RATE_CUSTOM_NONE, or 0 to reset custom growth rate.
+ * @param p2 Amount of days between growth, or TOWN_GROWTH_RATE_NONE, or 0 to reset custom growth rate.
  * @param text Unused.
  * @return Empty cost or an error.
  */
 CommandCost CmdTownGrowthRate(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	if (_current_company != OWNER_DEITY) return CMD_ERROR;
-	if ((p2 & TOWN_GROW_RATE_CUSTOM) != 0 && p2 != TOWN_GROW_RATE_CUSTOM_NONE) return CMD_ERROR;
 	if (GB(p2, 16, 16) != 0) return CMD_ERROR;
 
 	Town *t = Town::GetIfValid(p1);
@@ -2628,10 +2627,10 @@ CommandCost CmdTownGrowthRate(TileIndex tile, DoCommandFlag flags, uint32 p1, ui
 
 	if (flags & DC_EXEC) {
 		if (p2 == 0) {
-			/* Clear TOWN_GROW_RATE_CUSTOM, UpdateTownGrowRate will determine a proper value */
-			t->growth_rate = 0;
+			/* Just clear the flag, UpdateTownGrowRate will determine a proper growth rate */
+			ClrBit(t->flags, TOWN_CUSTOM_GROWTH);
 		} else {
-			uint old_rate = t->growth_rate & ~TOWN_GROW_RATE_CUSTOM;
+			uint old_rate = t->growth_rate;
 			if (t->grow_counter >= old_rate) {
 				/* This also catches old_rate == 0 */
 				t->grow_counter = p2;
@@ -2639,7 +2638,8 @@ CommandCost CmdTownGrowthRate(TileIndex tile, DoCommandFlag flags, uint32 p1, ui
 				/* Scale grow_counter, so half finished houses stay half finished */
 				t->grow_counter = t->grow_counter * p2 / old_rate;
 			}
-			t->growth_rate = p2 | TOWN_GROW_RATE_CUSTOM;
+			t->growth_rate = p2;
+			SetBit(t->flags, TOWN_CUSTOM_GROWTH);
 		}
 		UpdateTownGrowRate(t);
 		InvalidateWindowData(WC_TOWN_VIEW, p1);
@@ -2924,14 +2924,22 @@ static CommandCost TownActionFundBuildings(Town *t, DoCommandFlag flags)
 	if (!_settings_game.economy.fund_buildings) return CMD_ERROR;
 
 	if (flags & DC_EXEC) {
-		/* Build next tick */
-		t->grow_counter = 1;
 		/* And grow for 3 months */
 		t->fund_buildings_months = 3;
 
 		/* Enable growth (also checking GameScript's opinion) */
 		UpdateTownGrowRate(t);
 
+		/* Build a new house, but add a small delay to make sure
+		 * that spamming funding doesn't let town grow any faster
+		 * than 1 house per 2 * TOWN_GROWTH_TICKS ticks.
+		 * Also emulate original behaviour when town was only growing in
+		 * TOWN_GROWTH_TICKS intervals, to make sure that it's not too
+		 * tick-perfect and gives player some time window where he can
+		 * spam funding with the exact same effeciency.
+		 */
+		t->grow_counter = min(t->grow_counter, 2 * TOWN_GROWTH_TICKS - (t->growth_rate - t->grow_counter) % TOWN_GROWTH_TICKS);
+
 		SetWindowDirty(WC_TOWN_VIEW, t->index);
 	}
 	return CommandCost();
@@ -3148,8 +3156,8 @@ static void UpdateTownGrowRate(Town *t)
 		}
 	}
 
-	if ((t->growth_rate & TOWN_GROW_RATE_CUSTOM) != 0) {
-		if (t->growth_rate != TOWN_GROW_RATE_CUSTOM_NONE) SetBit(t->flags, TOWN_IS_GROWING);
+	if (HasBit(t->flags, TOWN_CUSTOM_GROWTH)) {
+		if (t->growth_rate != TOWN_GROWTH_RATE_NONE) SetBit(t->flags, TOWN_IS_GROWING);
 		SetWindowDirty(WC_TOWN_VIEW, t->index);
 		return;
 	}
@@ -3190,7 +3198,7 @@ static void UpdateTownGrowRate(Town *t)
 	m >>= growth_multiplier;
 	if (t->larger_town) m /= 2;
 
-	t->growth_rate = m / (t->cache.num_houses / 50 + 1);
+	t->growth_rate = TownTicksToGameTicks(m / (t->cache.num_houses / 50 + 1));
 	t->grow_counter = min(t->growth_rate, t->grow_counter);
 
 	SetBit(t->flags, TOWN_IS_GROWING);
diff --git a/src/town_gui.cpp b/src/town_gui.cpp
index a87c29367..1d604634d 100644
--- a/src/town_gui.cpp
+++ b/src/town_gui.cpp
@@ -392,7 +392,7 @@ public:
 		}
 
 		if (HasBit(this->town->flags, TOWN_IS_GROWING)) {
-			SetDParam(0, ((this->town->growth_rate & (~TOWN_GROW_RATE_CUSTOM)) * TOWN_GROWTH_TICKS + DAY_TICKS) / DAY_TICKS);
+			SetDParam(0, RoundDivSU(this->town->growth_rate + 1, DAY_TICKS));
 			DrawString(r.left + WD_FRAMERECT_LEFT, r.right - WD_FRAMERECT_LEFT, y += FONT_HEIGHT_NORMAL, this->town->fund_buildings_months == 0 ? STR_TOWN_VIEW_TOWN_GROWS_EVERY : STR_TOWN_VIEW_TOWN_GROWS_EVERY_FUNDED);
 		} else {
 			DrawString(r.left + WD_FRAMERECT_LEFT, r.right - WD_FRAMERECT_LEFT, y += FONT_HEIGHT_NORMAL, STR_TOWN_VIEW_TOWN_GROW_STOPPED);