NewGRF: Add generic town callback to set town zone radii

src/newgrf.cpp

@@ -6194,6 +6194,10 @@ static void NewSpriteGroup(ByteReader *buf)
 					break;
 				}
 
+				case GSF_FAKE_TOWNS:
+					act_group = NewCallbackResultSpriteGroupNoTransform(CALLBACK_FAILED);
+					break;
+
 				/* Loading of Tile Layout and Production Callback groups would happen here */
 				default: grfmsg(1, "NewSpriteGroup: Unsupported feature %s, skipping", GetFeatureString(feature));
 			}

src/newgrf_callbacks.h

@@ -282,6 +282,11 @@ enum CallbackID {
 
 	/** Called to determine the engine name to show. */
 	CBID_VEHICLE_NAME                    = 0x161, // 15 bit callback
+
+	/** Extended/non-standard callbacks follow */
+
+	/** Called to set town zones */
+	XCBID_TOWN_ZONES                     = 0xEC008001,
 };
 
 /**

src/newgrf_debug_gui.cpp

@@ -1642,6 +1642,7 @@ const char *GetNewGRFCallbackName(CallbackID cbid)
 		CBID(CBID_INDUSTRY_PROD_CHANGE_BUILD)
 		CBID(CBID_VEHICLE_SPAWN_VISUAL_EFFECT)
 		CBID(CBID_VEHICLE_NAME)
+		CBID(XCBID_TOWN_ZONES)
 		default: return nullptr;
 	}
 }

src/newgrf_extension.cpp

@@ -64,6 +64,7 @@ extern const GRFFeatureInfo _grf_feature_list[] = {
 	GRFFeatureInfo("more_action2_ids", 1, GFTOF_MORE_ACTION2_IDS),
 	GRFFeatureInfo("town_feature", 1),
 	GRFFeatureInfo("town_uncapped_variables", 1),
+	GRFFeatureInfo("town_zone_callback", 1, GFTOF_TOWN_ZONE_CALLBACK),
 	GRFFeatureInfo(),
 };
 

src/newgrf_extension.h

@@ -99,6 +99,7 @@ enum Action2VariableRemapIds {
 enum GRFFeatureTestObservationFlag : uint8 {
 	GFTOF_MORE_OBJECTS_PER_GRF = 0,
 	GFTOF_MORE_ACTION2_IDS,
+	GFTOF_TOWN_ZONE_CALLBACK,
 
 	GFTOF_INVALID = 0xFF,
 };

src/newgrf_generic.cpp

@@ -13,7 +13,10 @@
 #include "industrytype.h"
 #include "core/random_func.hpp"
 #include "newgrf_sound.h"
+#include "newgrf_town.h"
+#include "newgrf_extension.h"
 #include "water_map.h"
+#include "string_func.h"
 #include <list>
 
 #include "safeguards.h"
@@ -261,3 +264,38 @@ void AmbientSoundEffectCallback(TileIndex tile)
 
 	if (callback != CALLBACK_FAILED) PlayTileSound(grf_file, callback, tile);
 }
+
+uint16 GetTownZonesCallback(Town *t)
+{
+	TownResolverObject object(nullptr, t, true);
+	object.callback = XCBID_TOWN_ZONES;
+
+	const uint16 MAX_RETURN_VERSION = 0;
+
+	for (GenericCallbackList::const_iterator it = _gcl[GSF_FAKE_TOWNS].begin(); it != _gcl[GSF_FAKE_TOWNS].end(); ++it) {
+		if (!HasBit(it->file->observed_feature_tests, GFTOF_TOWN_ZONE_CALLBACK)) continue;
+		object.grffile = it->file;
+		object.root_spritegroup = it->group;
+		uint16 result = object.ResolveCallback();
+		if (result == CALLBACK_FAILED || result > MAX_RETURN_VERSION) continue;
+
+		return result;
+	}
+
+	return CALLBACK_FAILED;
+}
+
+void DumpGenericCallbackSpriteGroups(GrfSpecFeature feature, DumpSpriteGroupPrinter print)
+{
+	SpriteGroupDumper dumper(print);
+	bool first = true;
+	for (GenericCallbackList::const_iterator it = _gcl[feature].begin(); it != _gcl[feature].end(); ++it) {
+		if (!first) print(nullptr, DSGPO_PRINT, 0, "");
+		char buffer[64];
+		seprintf(buffer, lastof(buffer), "GRF: %08X, town zone cb enabled: %s",
+				BSWAP32(it->file->grfid), HasBit(it->file->observed_feature_tests, GFTOF_TOWN_ZONE_CALLBACK) ? "yes" : "no");
+		print(nullptr, DSGPO_PRINT, 0, buffer);
+		first = false;
+		dumper.DumpSpriteGroup(it->group, 0);
+	}
+}

src/newgrf_generic.h

@@ -49,6 +49,7 @@ void AddGenericCallback(GrfSpecFeature feature, const GRFFile *file, const Sprit
 
 uint16 GetAiPurchaseCallbackResult(GrfSpecFeature feature, CargoID cargo_type, uint8 default_selection, IndustryType src_industry, IndustryType dst_industry, uint8 distance, AIConstructionEvent event, uint8 count, uint8 station_size, const GRFFile **file);
 void AmbientSoundEffectCallback(TileIndex tile);
+uint16 GetTownZonesCallback(Town *t);
 
 /** Play an ambient sound effect for an empty tile. */
 static inline void AmbientSoundEffect(TileIndex tile)

src/newgrf_town.cpp

@@ -11,6 +11,7 @@
 #include "debug.h"
 #include "town.h"
 #include "newgrf_town.h"
+#include "newgrf_extension.h"
 
 #include "safeguards.h"
 

src/table/newgrf_debug_data.h

@@ -1593,6 +1593,7 @@ static const NIVariable _niv_towns[] = {
 
 class NIHTown : public NIHelper {
 	bool IsInspectable(uint index) const override        { return Town::IsValidID(index); }
+	bool ShowSpriteDumpButton(uint index) const override { return true; }
 	uint GetParent(uint index) const override            { return UINT32_MAX; }
 	const void *GetInstance(uint index)const override    { return Town::Get(index); }
 	const void *GetSpec(uint index) const override       { return nullptr; }
@@ -1660,6 +1661,12 @@ class NIHTown : public NIHelper {
 			}
 		}
 	}
+
+	/* virtual */ void SpriteDump(uint index, DumpSpriteGroupPrinter print) const override
+	{
+		extern void DumpGenericCallbackSpriteGroups(GrfSpecFeature feature, DumpSpriteGroupPrinter print);
+		DumpGenericCallbackSpriteGroups(GSF_FAKE_TOWNS, std::move(print));
+	}
 };
 
 static const NIFeature _nif_town = {

src/town_cmd.cpp

@@ -2052,21 +2052,37 @@ void UpdateTownRadius(Town *t)
 		{121, 81,  0, 49, 36}, // 88
 	};
 
-	if (_settings_game.economy.town_zone_calc_mode && t->larger_town) {
+	if (_settings_game.economy.town_zone_calc_mode) {
 		int mass = t->cache.num_houses / 8;
-		t->cache.squared_town_zone_radius[0] = mass * _settings_game.economy.city_zone_0_mult;
-		t->cache.squared_town_zone_radius[1] = mass * _settings_game.economy.city_zone_1_mult;
-		t->cache.squared_town_zone_radius[2] = mass * _settings_game.economy.city_zone_2_mult;
-		t->cache.squared_town_zone_radius[3] = mass * _settings_game.economy.city_zone_3_mult;
-		t->cache.squared_town_zone_radius[4] = mass * _settings_game.economy.city_zone_4_mult;
-	} else if (_settings_game.economy.town_zone_calc_mode) {
-		int mass = t->cache.num_houses / 8;
-		t->cache.squared_town_zone_radius[0] = mass * _settings_game.economy.town_zone_0_mult;
-		t->cache.squared_town_zone_radius[1] = mass * _settings_game.economy.town_zone_1_mult;
-		t->cache.squared_town_zone_radius[2] = mass * _settings_game.economy.town_zone_2_mult;
-		t->cache.squared_town_zone_radius[3] = mass * _settings_game.economy.town_zone_3_mult;
-		t->cache.squared_town_zone_radius[4] = mass * _settings_game.economy.town_zone_4_mult;
-	} else if (t->cache.num_houses < 92) {
+		if (t->larger_town) {
+			t->cache.squared_town_zone_radius[0] = mass * _settings_game.economy.city_zone_0_mult;
+			t->cache.squared_town_zone_radius[1] = mass * _settings_game.economy.city_zone_1_mult;
+			t->cache.squared_town_zone_radius[2] = mass * _settings_game.economy.city_zone_2_mult;
+			t->cache.squared_town_zone_radius[3] = mass * _settings_game.economy.city_zone_3_mult;
+			t->cache.squared_town_zone_radius[4] = mass * _settings_game.economy.city_zone_4_mult;
+		} else {
+			t->cache.squared_town_zone_radius[0] = mass * _settings_game.economy.town_zone_0_mult;
+			t->cache.squared_town_zone_radius[1] = mass * _settings_game.economy.town_zone_1_mult;
+			t->cache.squared_town_zone_radius[2] = mass * _settings_game.economy.town_zone_2_mult;
+			t->cache.squared_town_zone_radius[3] = mass * _settings_game.economy.town_zone_3_mult;
+			t->cache.squared_town_zone_radius[4] = mass * _settings_game.economy.town_zone_4_mult;
+		}
+		return;
+	}
+
+	MemSetT(t->cache.squared_town_zone_radius, 0, lengthof(t->cache.squared_town_zone_radius));
+
+	uint16 cb_result = GetTownZonesCallback(t);
+	if (cb_result == 0) {
+		t->cache.squared_town_zone_radius[0] = GetRegister(0x100);
+		t->cache.squared_town_zone_radius[1] = GetRegister(0x101);
+		t->cache.squared_town_zone_radius[2] = GetRegister(0x102);
+		t->cache.squared_town_zone_radius[3] = GetRegister(0x103);
+		t->cache.squared_town_zone_radius[4] = GetRegister(0x104);
+		return;
+	}
+
+	if (t->cache.num_houses < 92) {
 		memcpy(t->cache.squared_town_zone_radius, _town_squared_town_zone_radius_data[t->cache.num_houses / 4], sizeof(t->cache.squared_town_zone_radius));
 	} else {
 		int mass = t->cache.num_houses / 8;