Add very and extremely slow options to town growth rate setting

src/lang/english.txt

@@ -1727,6 +1727,8 @@ STR_CONFIG_SETTING_ZOOM_LVL_OUT_64X                             :64x
 STR_CONFIG_SETTING_ZOOM_LVL_OUT_128X                            :128x
 STR_CONFIG_SETTING_TOWN_GROWTH                                  :Town growth speed: {STRING2}
 STR_CONFIG_SETTING_TOWN_GROWTH_HELPTEXT                         :Speed of town growth
+STR_CONFIG_SETTING_TOWN_GROWTH_EXTREME_SLOW                     :Extremely slow
+STR_CONFIG_SETTING_TOWN_GROWTH_VERY_SLOW                        :Very slow
 STR_CONFIG_SETTING_TOWN_GROWTH_NONE                             :None
 STR_CONFIG_SETTING_TOWN_GROWTH_SLOW                             :Slow
 STR_CONFIG_SETTING_TOWN_GROWTH_NORMAL                           :Normal

src/saveload/extended_ver_sl.cpp

@@ -77,6 +77,7 @@ const SlxiSubChunkInfo _sl_xv_sub_chunk_infos[] = {
 	{ XSLFI_CUSTOM_BRIDGE_HEADS,    XSCF_NULL,                1,   1, "custom_bridge_heads",       NULL, NULL, NULL        },
 	{ XSLFI_CHUNNEL,                XSCF_NULL,                1,   1, "chunnel",                   NULL, NULL, "TUNN"      },
 	{ XSLFI_SCHEDULED_DISPATCH,     XSCF_NULL,                1,   1, "scheduled_dispatch",        NULL, NULL, NULL        },
+	{ XSLFI_MORE_TOWN_GROWTH_RATES, XSCF_NULL,                1,   1, "more_town_growth_rates",    NULL, NULL, NULL        },
 	{ XSLFI_NULL, XSCF_NULL, 0, 0, NULL, NULL, NULL, NULL },// This is the end marker
 };
 

src/saveload/extended_ver_sl.h

@@ -51,6 +51,7 @@ enum SlXvFeatureIndex {
 	XSLFI_CUSTOM_BRIDGE_HEADS,                    ///< Custom bridge heads
 	XSLFI_CHUNNEL,                                ///< Tunnels under water (channel tunnel)
 	XSLFI_SCHEDULED_DISPATCH,                     ///< Scheduled vehicle dispatching
+	XSLFI_MORE_TOWN_GROWTH_RATES,                 ///< More town growth rates
 
 	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.cpp

@@ -1445,6 +1445,21 @@ static bool UpdateClientConfigValues(int32 p1)
 
 /* End - Callback Functions */
 
+/* Begin - GUI order callbacks */
+
+static int OrderTownGrowthRate(uint nth)
+{
+	if (nth == 0) {
+		return 0;
+	} else if (nth <= 2) {
+		return nth - 3;
+	} else {
+		return nth - 2;
+	}
+}
+
+/* End - GUI order callbacks */
+
 /**
  * Prepare for reading and old diff_custom by zero-ing the memory.
  */

src/settings_type.h

@@ -540,7 +540,7 @@ struct EconomySettings {
 	bool   give_money;                       ///< allow giving other companies money
 	bool   mod_road_rebuild;                 ///< roadworks remove unnecessary RoadBits
 	bool   multiple_industry_per_town;       ///< allow many industries of the same type per town
-	uint8  town_growth_rate;                 ///< town growth rate
+	int8   town_growth_rate;                 ///< town growth rate
 	uint8  larger_towns;                     ///< the number of cities to build. These start off larger and grow twice as fast
 	uint8  initial_city_size;                ///< multiplier for the initial size of the cities compared to towns
 	TownLayoutByte town_layout;              ///< select town layout, @see TownLayout

src/table/settings.ini

@@ -61,6 +61,8 @@ static bool CheckSharingAir(int32 p1);
 
 /* Begin - GUI order callbacks */
 
+static int OrderTownGrowthRate(uint nth);
+
 /* End - GUI order callbacks */
 
 /* Some settings do not need to be synchronised when playing in multiplayer.
@@ -1738,15 +1740,16 @@ extver   = SlXvFeatureTest(XSLFTO_AND, XSLFI_SPRINGPP)
 [SDT_VAR]
 base     = GameSettings
 var      = economy.town_growth_rate
-type     = SLE_UINT8
+type     = SLE_INT8
 from     = 54
 guiflags = SGF_MULTISTRING
 def      = 2
-min      = 0
+min      = -2
 max      = 4
 str      = STR_CONFIG_SETTING_TOWN_GROWTH
 strhelp  = STR_CONFIG_SETTING_TOWN_GROWTH_HELPTEXT
-strval   = STR_CONFIG_SETTING_TOWN_GROWTH_NONE
+strval   = STR_CONFIG_SETTING_TOWN_GROWTH_EXTREME_SLOW
+orderproc = OrderTownGrowthRate
 
 [SDT_VAR]
 base     = GameSettings

src/town_cmd.cpp

@@ -3389,9 +3389,20 @@ static void UpdateTownGrowRate(Town *t)
 
 	/* Use the normal growth rate values if new buildings have been funded in
 	 * this town and the growth rate is set to none. */
-	uint growth_multiplier = _settings_game.economy.town_growth_rate != 0 ? _settings_game.economy.town_growth_rate - 1 : 1;
+	int growth_multiplier;
+	if (_settings_game.economy.town_growth_rate == 0) {
+		growth_multiplier = 1;
+	} else if (_settings_game.economy.town_growth_rate > 0) {
+		growth_multiplier = _settings_game.economy.town_growth_rate - 1;
+	} else {
+		growth_multiplier = _settings_game.economy.town_growth_rate;
+	}
 
-	m >>= growth_multiplier;
+	if (growth_multiplier < 0) {
+		m <<= (-growth_multiplier);
+	} else {
+		m >>= growth_multiplier;
+	}
 	if (t->larger_town) m /= 2;
 
 	t->growth_rate = m / (t->cache.num_houses / 50 + 1);