Codechange: Don't use globals for story/goal/sign/group command proc return values.

23 files changed, 105 insertions, 236 deletions

diff --git a/src/autoreplace_cmd.cpp b/src/autoreplace_cmd.cpp
index f2ef317f0..9fef03839 100644
--- a/src/autoreplace_cmd.cpp
+++ b/src/autoreplace_cmd.cpp
@@ -405,7 +405,7 @@ static CommandCost CopyHeadSpecificThings(Vehicle *old_head, Vehicle *new_head,
 	if (cost.Succeeded() && old_head != new_head) cost.AddCost(Command<CMD_CLONE_ORDER>::Do(DC_EXEC, CO_SHARE, new_head->index, old_head->index));
 
 	/* Copy group membership */
-	if (cost.Succeeded() && old_head != new_head) cost.AddCost(Command<CMD_ADD_VEHICLE_GROUP>::Do(DC_EXEC, old_head->group_id, new_head->index, false));
+	if (cost.Succeeded() && old_head != new_head) cost.AddCost(std::get<0>(Command<CMD_ADD_VEHICLE_GROUP>::Do(DC_EXEC, old_head->group_id, new_head->index, false)));
 
 	/* Perform start/stop check whether the new vehicle suits newgrf restrictions etc. */
 	if (cost.Succeeded()) {
diff --git a/src/goal.cpp b/src/goal.cpp
index 99322ec2c..447763866 100644
--- a/src/goal.cpp
+++ b/src/goal.cpp
@@ -28,8 +28,6 @@
 #include "safeguards.h"
 
 
-GoalID _new_goal_id;
-
 GoalPool _goal_pool("Goal");
 INSTANTIATE_POOL_METHODS(Goal)
 
@@ -42,43 +40,43 @@ INSTANTIATE_POOL_METHODS(Goal)
  * @param text Text of the goal.
  * @return the cost of this operation or an error
  */
-CommandCost CmdCreateGoal(DoCommandFlag flags, CompanyID company, GoalType type, GoalTypeID dest, const std::string &text)
+std::tuple<CommandCost, GoalID> CmdCreateGoal(DoCommandFlag flags, CompanyID company, GoalType type, GoalTypeID dest, const std::string &text)
 {
-	if (!Goal::CanAllocateItem()) return CMD_ERROR;
+	if (!Goal::CanAllocateItem()) return { CMD_ERROR, INVALID_GOAL };
 
-	if (_current_company != OWNER_DEITY) return CMD_ERROR;
-	if (text.empty()) return CMD_ERROR;
-	if (company != INVALID_COMPANY && !Company::IsValidID(company)) return CMD_ERROR;
+	if (_current_company != OWNER_DEITY) return { CMD_ERROR, INVALID_GOAL };
+	if (text.empty()) return { CMD_ERROR, INVALID_GOAL };
+	if (company != INVALID_COMPANY && !Company::IsValidID(company)) return { CMD_ERROR, INVALID_GOAL };
 
 	switch (type) {
 		case GT_NONE:
-			if (dest != 0) return CMD_ERROR;
+			if (dest != 0) return { CMD_ERROR, INVALID_GOAL };
 			break;
 
 		case GT_TILE:
-			if (!IsValidTile(dest)) return CMD_ERROR;
+			if (!IsValidTile(dest)) return { CMD_ERROR, INVALID_GOAL };
 			break;
 
 		case GT_INDUSTRY:
-			if (!Industry::IsValidID(dest)) return CMD_ERROR;
+			if (!Industry::IsValidID(dest)) return { CMD_ERROR, INVALID_GOAL };
 			break;
 
 		case GT_TOWN:
-			if (!Town::IsValidID(dest)) return CMD_ERROR;
+			if (!Town::IsValidID(dest)) return { CMD_ERROR, INVALID_GOAL };
 			break;
 
 		case GT_COMPANY:
-			if (!Company::IsValidID(dest)) return CMD_ERROR;
+			if (!Company::IsValidID(dest)) return { CMD_ERROR, INVALID_GOAL };
 			break;
 
 		case GT_STORY_PAGE: {
-			if (!StoryPage::IsValidID(dest)) return CMD_ERROR;
+			if (!StoryPage::IsValidID(dest)) return { CMD_ERROR, INVALID_GOAL };
 			CompanyID story_company = StoryPage::Get(dest)->company;
-			if (company == INVALID_COMPANY ? story_company != INVALID_COMPANY : story_company != INVALID_COMPANY && story_company != company) return CMD_ERROR;
+			if (company == INVALID_COMPANY ? story_company != INVALID_COMPANY : story_company != INVALID_COMPANY && story_company != company) return { CMD_ERROR, INVALID_GOAL };
 			break;
 		}
 
-		default: return CMD_ERROR;
+		default: return { CMD_ERROR, INVALID_GOAL };
 	}
 
 	if (flags & DC_EXEC) {
@@ -97,10 +95,10 @@ CommandCost CmdCreateGoal(DoCommandFlag flags, CompanyID company, GoalType type,
 		}
 		if (Goal::GetNumItems() == 1) InvalidateWindowData(WC_MAIN_TOOLBAR, 0);
 
-		_new_goal_id = g->index;
+		return { CommandCost(), g->index };
 	}
 
-	return CommandCost();
+	return { CommandCost(), INVALID_GOAL };
 }
 
 /**
diff --git a/src/goal_cmd.h b/src/goal_cmd.h
index 5c3e4954f..5be2044e2 100644
--- a/src/goal_cmd.h
+++ b/src/goal_cmd.h
@@ -14,7 +14,7 @@
 #include "command_type.h"
 #include "goal_type.h"
 
-CommandCost CmdCreateGoal(DoCommandFlag flags, CompanyID company, GoalType type, GoalTypeID dest, const std::string &text);
+std::tuple<CommandCost, GoalID> CmdCreateGoal(DoCommandFlag flags, CompanyID company, GoalType type, GoalTypeID dest, const std::string &text);
 CommandCost CmdRemoveGoal(DoCommandFlag flags, GoalID goal);
 CommandCost CmdSetGoalText(DoCommandFlag flags, GoalID goal, const std::string &text);
 CommandCost CmdSetGoalProgress(DoCommandFlag flags, GoalID goal, const std::string &text);
diff --git a/src/goal_type.h b/src/goal_type.h
index 5bbd8c258..27ec758a9 100644
--- a/src/goal_type.h
+++ b/src/goal_type.h
@@ -37,7 +37,6 @@ static const GoalTypeID INVALID_GOALTYPE = 0xFFFFFFFF; ///< Invalid/unknown inde
 
 typedef uint16 GoalID; ///< ID of a goal
 struct Goal;
-
-extern GoalID _new_goal_id;
+static const GoalID INVALID_GOAL = 0xFFFF; ///< Constant representing a non-existing goal.
 
 #endif /* GOAL_TYPE_H */
diff --git a/src/group.h b/src/group.h
index e0f0b9196..6d55c9385 100644
--- a/src/group.h
+++ b/src/group.h
@@ -113,6 +113,4 @@ void RemoveVehicleFromGroup(const Vehicle *v);
 void RemoveAllGroupsForCompany(const CompanyID company);
 bool GroupIsInGroup(GroupID search, GroupID group);
 
-extern GroupID _new_group_id;
-
 #endif /* GROUP_H */
diff --git a/src/group_cmd.cpp b/src/group_cmd.cpp
index 4b34ad382..c8772e5c1 100644
--- a/src/group_cmd.cpp
+++ b/src/group_cmd.cpp
@@ -25,8 +25,6 @@
 
 #include "safeguards.h"
 
-GroupID _new_group_id;
-
 GroupPool _group_pool("Group");
 INSTANTIATE_POOL_METHODS(Group)
 
@@ -299,16 +297,16 @@ Group::Group(Owner owner)
  * @param parent_group parent groupid
  * @return the cost of this operation or an error
  */
-CommandCost CmdCreateGroup(DoCommandFlag flags, VehicleType vt, GroupID parent_group)
+std::tuple<CommandCost, GroupID> CmdCreateGroup(DoCommandFlag flags, VehicleType vt, GroupID parent_group)
 {
-	if (!IsCompanyBuildableVehicleType(vt)) return CMD_ERROR;
+	if (!IsCompanyBuildableVehicleType(vt)) return { CMD_ERROR, INVALID_GROUP };
 
-	if (!Group::CanAllocateItem()) return CMD_ERROR;
+	if (!Group::CanAllocateItem()) return { CMD_ERROR, INVALID_GROUP };
 
 	const Group *pg = Group::GetIfValid(parent_group);
 	if (pg != nullptr) {
-		if (pg->owner != _current_company) return CMD_ERROR;
-		if (pg->vehicle_type != vt) return CMD_ERROR;
+		if (pg->owner != _current_company) return { CMD_ERROR, INVALID_GROUP };
+		if (pg->vehicle_type != vt) return { CMD_ERROR, INVALID_GROUP };
 	}
 
 	if (flags & DC_EXEC) {
@@ -328,13 +326,13 @@ CommandCost CmdCreateGroup(DoCommandFlag flags, VehicleType vt, GroupID parent_g
 			g->flags = pg->flags;
 		}
 
-		_new_group_id = g->index;
-
 		InvalidateWindowData(GetWindowClassForVehicleType(vt), VehicleListIdentifier(VL_GROUP_LIST, vt, _current_company).Pack());
 		InvalidateWindowData(WC_COMPANY_COLOUR, g->owner, g->vehicle_type);
+
+		return { CommandCost(), g->index };
 	}
 
-	return CommandCost();
+	return { CommandCost(), INVALID_GROUP};
 }
 
 
@@ -497,26 +495,26 @@ static void AddVehicleToGroup(Vehicle *v, GroupID new_g)
  * @param add_shared Add shared vehicles as well.
  * @return the cost of this operation or an error
  */
-CommandCost CmdAddVehicleGroup(DoCommandFlag flags, GroupID group_id, VehicleID veh_id, bool add_shared)
+std::tuple<CommandCost, GroupID> CmdAddVehicleGroup(DoCommandFlag flags, GroupID group_id, VehicleID veh_id, bool add_shared)
 {
 	Vehicle *v = Vehicle::GetIfValid(veh_id);
 	GroupID new_g = group_id;
 
-	if (v == nullptr || (!Group::IsValidID(new_g) && !IsDefaultGroupID(new_g) && new_g != NEW_GROUP)) return CMD_ERROR;
+	if (v == nullptr || (!Group::IsValidID(new_g) && !IsDefaultGroupID(new_g) && new_g != NEW_GROUP)) return { CMD_ERROR, INVALID_GROUP };
 
 	if (Group::IsValidID(new_g)) {
 		Group *g = Group::Get(new_g);
-		if (g->owner != _current_company || g->vehicle_type != v->type) return CMD_ERROR;
+		if (g->owner != _current_company || g->vehicle_type != v->type) return { CMD_ERROR, INVALID_GROUP };
 	}
 
-	if (v->owner != _current_company || !v->IsPrimaryVehicle()) return CMD_ERROR;
+	if (v->owner != _current_company || !v->IsPrimaryVehicle()) return { CMD_ERROR, INVALID_GROUP };
 
 	if (new_g == NEW_GROUP) {
 		/* Create new group. */
-		CommandCost ret = CmdCreateGroup(flags, v->type, INVALID_GROUP);
-		if (ret.Failed()) return ret;
+		auto [ret, group_id] = CmdCreateGroup(flags, v->type, INVALID_GROUP);
+		if (ret.Failed()) return { ret, group_id };
 
-		new_g = _new_group_id;
+		new_g = group_id;
 	}
 
 	if (flags & DC_EXEC) {
@@ -541,7 +539,7 @@ CommandCost CmdAddVehicleGroup(DoCommandFlag flags, GroupID group_id, VehicleID
 		InvalidateWindowData(WC_VEHICLE_DETAILS, v->index);
 	}
 
-	return CommandCost();
+	return { CommandCost(), new_g };
 }
 
 /**
diff --git a/src/group_cmd.h b/src/group_cmd.h
index d3c25fda1..f84e37859 100644
--- a/src/group_cmd.h
+++ b/src/group_cmd.h
@@ -23,10 +23,10 @@ enum class AlterGroupMode : byte {
 	SetParent, ///< Change group parent.
 };
 
-CommandCost CmdCreateGroup(DoCommandFlag flags, VehicleType vt, GroupID parent_group);
+std::tuple<CommandCost, GroupID> CmdCreateGroup(DoCommandFlag flags, VehicleType vt, GroupID parent_group);
 CommandCost CmdAlterGroup(DoCommandFlag flags, AlterGroupMode mode, GroupID group_id, GroupID parent_id, const std::string &text);
 CommandCost CmdDeleteGroup(DoCommandFlag flags, GroupID group_id);
-CommandCost CmdAddVehicleGroup(DoCommandFlag flags, GroupID group_id, VehicleID veh_id, bool add_shared);
+std::tuple<CommandCost, GroupID> CmdAddVehicleGroup(DoCommandFlag flags, GroupID group_id, VehicleID veh_id, bool add_shared);
 CommandCost CmdAddSharedVehicleGroup(DoCommandFlag flags, GroupID id_g, VehicleType type);
 CommandCost CmdRemoveAllVehiclesGroup(DoCommandFlag flags, GroupID group_id);
 CommandCost CmdSetGroupFlag(DoCommandFlag flags, GroupID group_id, GroupFlags flag, bool value, bool recursive);
@@ -41,7 +41,7 @@ DEF_CMD_TRAIT(CMD_REMOVE_ALL_VEHICLES_GROUP, CmdRemoveAllVehiclesGroup, 0, CMDT_
 DEF_CMD_TRAIT(CMD_SET_GROUP_FLAG,            CmdSetGroupFlag,           0, CMDT_ROUTE_MANAGEMENT)
 DEF_CMD_TRAIT(CMD_SET_GROUP_LIVERY,          CmdSetGroupLivery,         0, CMDT_ROUTE_MANAGEMENT)
 
-void CcCreateGroup(Commands cmd, const CommandCost &result, VehicleType vt, GroupID parent_group);
-void CcAddVehicleNewGroup(Commands cmd, const CommandCost &result, GroupID, VehicleID veh_id, bool);
+void CcCreateGroup(Commands cmd, const CommandCost &result, GroupID new_group, VehicleType vt, GroupID parent_group);
+void CcAddVehicleNewGroup(Commands cmd, const CommandCost &result, GroupID new_group, GroupID, VehicleID veh_id, bool);
 
 #endif /* GROUP_CMD_H */
diff --git a/src/group_gui.cpp b/src/group_gui.cpp
index f614551f7..503ddddd9 100644
--- a/src/group_gui.cpp
+++ b/src/group_gui.cpp
@@ -1143,40 +1143,42 @@ static inline VehicleGroupWindow *FindVehicleGroupWindow(VehicleType vt, Owner o
  * Opens a 'Rename group' window for newly created group.
  * @param veh_type Vehicle type.
  */
-static void CcCreateGroup(VehicleType veh_type)
+static void CcCreateGroup(GroupID gid, VehicleType veh_type)
 {
 	VehicleGroupWindow *w = FindVehicleGroupWindow(veh_type, _current_company);
-	if (w != nullptr) w->ShowRenameGroupWindow(_new_group_id, true);
+	if (w != nullptr) w->ShowRenameGroupWindow(gid, true);
 }
 
 /**
  * Opens a 'Rename group' window for newly created group.
  * @param cmd Unused.
  * @param result Did command succeed?
+ * @param new_group ID of the created group.
  * @param vt Vehicle type.
- * @param parent_group Parent group of the enw group.
+ * @param parent_group Parent group of the new group.
  * @see CmdCreateGroup
  */
-void CcCreateGroup(Commands cmd, const CommandCost &result, VehicleType vt, GroupID parent_group)
+void CcCreateGroup(Commands cmd, const CommandCost &result, GroupID new_group, VehicleType vt, GroupID parent_group)
 {
 	if (result.Failed()) return;
 
 	assert(vt <= VEH_AIRCRAFT);
-	CcCreateGroup(vt);
+	CcCreateGroup(new_group, vt);
 }
 
 /**
  * Open rename window after adding a vehicle to a new group via drag and drop.
  * @param cmd Unused.
  * @param result Did command succeed?
+ * @param new_group ID of the created group.
  * @param veh_id vehicle to add to a group
  */
-void CcAddVehicleNewGroup(Commands cmd, const CommandCost &result, GroupID, VehicleID veh_id, bool)
+void CcAddVehicleNewGroup(Commands cmd, const CommandCost &result, GroupID new_group, GroupID, VehicleID veh_id, bool)
 {
 	if (result.Failed()) return;
 
 	assert(Vehicle::IsValidID(veh_id));
-	CcCreateGroup(Vehicle::Get(veh_id)->type);
+	CcCreateGroup(new_group, Vehicle::Get(veh_id)->type);
 }
 
 /**
diff --git a/src/script/api/script_object.cpp b/src/script/api/script_object.cpp
index dad79309a..f95433bd9 100644
--- a/src/script/api/script_object.cpp
+++ b/src/script/api/script_object.cpp
@@ -161,11 +161,6 @@ ScriptObject::ActiveInstance::~ActiveInstance()
 	GetStorage()->last_command_res = res;
 	/* Also store the results of various global variables */
 	SetNewVehicleID(_new_vehicle_id);
-	SetNewSignID(_new_sign_id);
-	SetNewGroupID(_new_group_id);
-	SetNewGoalID(_new_goal_id);
-	SetNewStoryPageID(_new_story_page_id);
-	SetNewStoryPageElementID(_new_story_page_element_id);
 }
 
 /* static */ bool ScriptObject::GetLastCommandRes()
@@ -193,56 +188,6 @@ ScriptObject::ActiveInstance::~ActiveInstance()
 	return GetStorage()->new_vehicle_id;
 }
 
-/* static */ void ScriptObject::SetNewSignID(SignID sign_id)
-{
-	GetStorage()->new_sign_id = sign_id;
-}
-
-/* static */ SignID ScriptObject::GetNewSignID()
-{
-	return GetStorage()->new_sign_id;
-}
-
-/* static */ void ScriptObject::SetNewGroupID(GroupID group_id)
-{
-	GetStorage()->new_group_id = group_id;
-}
-
-/* static */ GroupID ScriptObject::GetNewGroupID()
-{
-	return GetStorage()->new_group_id;
-}
-
-/* static */ void ScriptObject::SetNewGoalID(GoalID goal_id)
-{
-	GetStorage()->new_goal_id = goal_id;
-}
-
-/* static */ GroupID ScriptObject::GetNewGoalID()
-{
-	return GetStorage()->new_goal_id;
-}
-
-/* static */ void ScriptObject::SetNewStoryPageID(StoryPageID story_page_id)
-{
-	GetStorage()->new_story_page_id = story_page_id;
-}
-
-/* static */ GroupID ScriptObject::GetNewStoryPageID()
-{
-	return GetStorage()->new_story_page_id;
-}
-
-/* static */ void ScriptObject::SetNewStoryPageElementID(StoryPageElementID story_page_element_id)
-{
-	GetStorage()->new_story_page_element_id = story_page_element_id;
-}
-
-/* static */ GroupID ScriptObject::GetNewStoryPageElementID()
-{
-	return GetStorage()->new_story_page_element_id;
-}
-
 /* static */ void ScriptObject::SetAllowDoCommand(bool allow)
 {
 	GetStorage()->allow_do_command = allow;
diff --git a/src/script/api/script_object.hpp b/src/script/api/script_object.hpp
index f9a66f8a8..d90fec351 100644
--- a/src/script/api/script_object.hpp
+++ b/src/script/api/script_object.hpp
@@ -198,31 +198,6 @@ protected:
 	static VehicleID GetNewVehicleID();
 
 	/**
-	 * Get the latest stored new_sign_id.
-	 */
-	static SignID GetNewSignID();
-
-	/**
-	 * Get the latest stored new_group_id.
-	 */
-	static GroupID GetNewGroupID();
-
-	/**
-	 * Get the latest stored new_goal_id.
-	 */
-	static GoalID GetNewGoalID();
-
-	/**
-	 * Get the latest stored new_story_page_id.
-	 */
-	static StoryPageID GetNewStoryPageID();
-
-	/**
-	 * Get the latest stored new_story_page_id.
-	 */
-	static StoryPageID GetNewStoryPageElementID();
-
-	/**
 	 * Store a allow_do_command per company.
 	 * @param allow The new allow.
 	 */
@@ -305,36 +280,6 @@ private:
 	 */
 	static void SetNewVehicleID(VehicleID vehicle_id);
 
-	/**
-	 * Store a new_sign_id per company.
-	 * @param sign_id The new SignID.
-	 */
-	static void SetNewSignID(SignID sign_id);
-
-	/**
-	 * Store a new_group_id per company.
-	 * @param group_id The new GroupID.
-	 */
-	static void SetNewGroupID(GroupID group_id);
-
-	/**
-	 * Store a new_goal_id per company.
-	 * @param goal_id The new GoalID.
-	 */
-	static void SetNewGoalID(GoalID goal_id);
-
-	/**
-	 * Store a new_story_page_id per company.
-	 * @param story_page_id The new StoryPageID.
-	 */
-	static void SetNewStoryPageID(StoryPageID story_page_id);
-
-	/**
-	 * Store a new_story_page_id per company.
-	 * @param story_page_id The new StoryPageID.
-	 */
-	static void SetNewStoryPageElementID(StoryPageElementID story_page_element_id);
-
 	/* Helper functions for DoCommand. */
 	static std::tuple<bool, bool, bool> DoCommandPrep();
 	static bool DoCommandProcessResult(const CommandCost &res, Script_SuspendCallbackProc *callback, bool estimate_only);
diff --git a/src/script/script_instance.cpp b/src/script/script_instance.cpp
index 0dfdd4b2a..9d978f833 100644
--- a/src/script/script_instance.cpp
+++ b/src/script/script_instance.cpp
@@ -26,6 +26,7 @@
 #include "../company_base.h"
 #include "../company_func.h"
 #include "../fileio_func.h"
+#include "../misc/endian_buffer.hpp"
 
 #include "../safeguards.h"
 
@@ -274,27 +275,27 @@ void ScriptInstance::CollectGarbage()
 
 /* static */ void ScriptInstance::DoCommandReturnSignID(ScriptInstance *instance)
 {
-	instance->engine->InsertResult(ScriptObject::GetNewSignID());
+	instance->engine->InsertResult(EndianBufferReader::ToValue<SignID>(ScriptObject::GetLastCommandResData()));
 }
 
 /* static */ void ScriptInstance::DoCommandReturnGroupID(ScriptInstance *instance)
 {
-	instance->engine->InsertResult(ScriptObject::GetNewGroupID());
+	instance->engine->InsertResult(EndianBufferReader::ToValue<GroupID>(ScriptObject::GetLastCommandResData()));
 }
 
 /* static */ void ScriptInstance::DoCommandReturnGoalID(ScriptInstance *instance)
 {
-	instance->engine->InsertResult(ScriptObject::GetNewGoalID());
+	instance->engine->InsertResult(EndianBufferReader::ToValue<GoalID>(ScriptObject::GetLastCommandResData()));
 }
 
 /* static */ void ScriptInstance::DoCommandReturnStoryPageID(ScriptInstance *instance)
 {
-	instance->engine->InsertResult(ScriptObject::GetNewStoryPageID());
+	instance->engine->InsertResult(EndianBufferReader::ToValue<StoryPageID>(ScriptObject::GetLastCommandResData()));
 }
 
 /* static */ void ScriptInstance::DoCommandReturnStoryPageElementID(ScriptInstance *instance)
 {
-	instance->engine->InsertResult(ScriptObject::GetNewStoryPageElementID());
+	instance->engine->InsertResult(EndianBufferReader::ToValue<StoryPageElementID>(ScriptObject::GetLastCommandResData()));
 }
 
 ScriptStorage *ScriptInstance::GetStorage()
diff --git a/src/script/script_storage.hpp b/src/script/script_storage.hpp
index b8d1038a0..f95eb7e71 100644
--- a/src/script/script_storage.hpp
+++ b/src/script/script_storage.hpp
@@ -50,11 +50,6 @@ private:
 	CommandDataBuffer last_cmd_ret;  ///< The extra data returned by the last command.
 
 	VehicleID new_vehicle_id;        ///< The ID of the new Vehicle.
-	SignID new_sign_id;              ///< The ID of the new Sign.
-	GroupID new_group_id;            ///< The ID of the new Group.
-	GoalID new_goal_id;              ///< The ID of the new Goal.
-	StoryPageID new_story_page_id;   ///< The ID of the new StoryPage.
-	StoryPageID new_story_page_element_id; ///< The ID of the new StoryPageElement.
 
 	std::vector<int> callback_value; ///< The values which need to survive a callback.
 
@@ -79,11 +74,6 @@ public:
 		last_tile         (INVALID_TILE),
 		last_cmd          (CMD_END),
 		new_vehicle_id    (0),
-		new_sign_id       (0),
-		new_group_id      (0),
-		new_goal_id       (0),
-		new_story_page_id (0),
-		new_story_page_element_id(0),
 		/* calback_value (can't be set) */
 		road_type         (INVALID_ROADTYPE),
 		rail_type         (INVALID_RAILTYPE),
diff --git a/src/signs_cmd.cpp b/src/signs_cmd.cpp
index f50e37583..139d874c6 100644
--- a/src/signs_cmd.cpp
+++ b/src/signs_cmd.cpp
@@ -23,9 +23,6 @@
 
 #include "safeguards.h"
 
-/** The last built sign. */
-SignID _new_sign_id;
-
 /**
  * Place a sign at the given coordinates. Ownership of sign has
  * no effect whatsoever except for the colour the sign gets for easy recognition,
@@ -33,15 +30,15 @@ SignID _new_sign_id;
  * @param tile tile to place sign at
  * @param flags type of operation
  * @param text contents of the sign
- * @return the cost of this operation or an error
+ * @return the cost of this operation + the ID of the new sign or an error
  */
-CommandCost CmdPlaceSign(DoCommandFlag flags, TileIndex tile, const std::string &text)
+std::tuple<CommandCost, SignID> CmdPlaceSign(DoCommandFlag flags, TileIndex tile, const std::string &text)
 {
 	/* Try to locate a new sign */
-	if (!Sign::CanAllocateItem()) return_cmd_error(STR_ERROR_TOO_MANY_SIGNS);
+	if (!Sign::CanAllocateItem()) return { CommandCost(STR_ERROR_TOO_MANY_SIGNS), INVALID_SIGN };
 
 	/* Check sign text length if any */
-	if (Utf8StringLength(text) >= MAX_LENGTH_SIGN_NAME_CHARS) return CMD_ERROR;
+	if (Utf8StringLength(text) >= MAX_LENGTH_SIGN_NAME_CHARS) return { CMD_ERROR, INVALID_SIGN };
 
 	/* When we execute, really make the sign */
 	if (flags & DC_EXEC) {
@@ -57,10 +54,10 @@ CommandCost CmdPlaceSign(DoCommandFlag flags, TileIndex tile, const std::string
 		}
 		si->UpdateVirtCoord();
 		InvalidateWindowData(WC_SIGN_LIST, 0, 0);
-		_new_sign_id = si->index;
+		return { CommandCost(), si->index };
 	}
 
-	return CommandCost();
+	return { CommandCost(), INVALID_SIGN };
 }
 
 /**
@@ -107,13 +104,13 @@ CommandCost CmdRenameSign(DoCommandFlag flags, SignID sign_id, const std::string
  * Callback function that is called after a sign is placed
  * @param cmd unused
  * @param result of the operation
- * @param tile unused
+ * @param new_sign ID of the placed sign.
  */
-void CcPlaceSign(Commands cmd, const CommandCost &result, TileIndex tile)
+void CcPlaceSign(Commands cmd, const CommandCost &result, SignID new_sign)
 {
 	if (result.Failed()) return;
 
-	ShowRenameSignWindow(Sign::Get(_new_sign_id));
+	ShowRenameSignWindow(Sign::Get(new_sign));
 	ResetObjectToPlace();
 }
 
diff --git a/src/signs_cmd.h b/src/signs_cmd.h
index 1c4e1b465..627cfa648 100644
--- a/src/signs_cmd.h
+++ b/src/signs_cmd.h
@@ -13,10 +13,12 @@
 #include "command_type.h"
 #include "signs_type.h"
 
-CommandCost CmdPlaceSign(DoCommandFlag flags, TileIndex tile, const std::string &text);
+std::tuple<CommandCost, SignID> CmdPlaceSign(DoCommandFlag flags, TileIndex tile, const std::string &text);
 CommandCost CmdRenameSign(DoCommandFlag flags, SignID sign_id, const std::string &text);
 
 DEF_CMD_TRAIT(CMD_PLACE_SIGN,  CmdPlaceSign,  CMD_DEITY, CMDT_OTHER_MANAGEMENT)
 DEF_CMD_TRAIT(CMD_RENAME_SIGN, CmdRenameSign, CMD_DEITY, CMDT_OTHER_MANAGEMENT)
 
+void CcPlaceSign(Commands cmd, const CommandCost &result, SignID new_sign);
+
 #endif /* SIGNS_CMD_H */
diff --git a/src/signs_func.h b/src/signs_func.h
index af677201c..18f27fc81 100644
--- a/src/signs_func.h
+++ b/src/signs_func.h
@@ -14,7 +14,6 @@
 #include "tile_type.h"
 
 struct Window;
-extern SignID _new_sign_id;
 
 void UpdateAllSignVirtCoords();
 void PlaceProc_Sign(TileIndex tile);
diff --git a/src/story.cpp b/src/story.cpp
index 259bfbd61..8de4df89f 100644
--- a/src/story.cpp
+++ b/src/story.cpp
@@ -30,8 +30,6 @@
 #include "safeguards.h"
 
 
-StoryPageElementID _new_story_page_element_id;
-StoryPageID _new_story_page_id;
 uint32 _story_page_element_next_sort_value;
 uint32 _story_page_next_sort_value;
 
@@ -202,12 +200,12 @@ bool StoryPageButtonData::ValidateVehicleType() const
  * @param text Title of the story page. Null is allowed in which case a generic page title is provided by OpenTTD.
  * @return the cost of this operation or an error
  */
-CommandCost CmdCreateStoryPage(DoCommandFlag flags, CompanyID company, const std::string &text)
+std::tuple<CommandCost, StoryPageID> CmdCreateStoryPage(DoCommandFlag flags, CompanyID company, const std::string &text)
 {
-	if (!StoryPage::CanAllocateItem()) return CMD_ERROR;
+	if (!StoryPage::CanAllocateItem()) return { CMD_ERROR, INVALID_STORY_PAGE };
 
-	if (_current_company != OWNER_DEITY) return CMD_ERROR;
-	if (company != INVALID_COMPANY && !Company::IsValidID(company)) return CMD_ERROR;
+	if (_current_company != OWNER_DEITY) return { CMD_ERROR, INVALID_STORY_PAGE };
+	if (company != INVALID_COMPANY && !Company::IsValidID(company)) return { CMD_ERROR, INVALID_STORY_PAGE };
 
 	if (flags & DC_EXEC) {
 		if (_story_page_pool.items == 0) {
@@ -228,11 +226,11 @@ CommandCost CmdCreateStoryPage(DoCommandFlag flags, CompanyID company, const std
 		InvalidateWindowClassesData(WC_STORY_BOOK, -1);
 		if (StoryPage::GetNumItems() == 1) InvalidateWindowData(WC_MAIN_TOOLBAR, 0);
 
-		_new_story_page_id = s->index;
 		_story_page_next_sort_value++;
+		return { CommandCost(), s->index };
 	}
 
-	return CommandCost();
+	return { CommandCost(), INVALID_STORY_PAGE };
 }
 
 /**
@@ -245,20 +243,21 @@ CommandCost CmdCreateStoryPage(DoCommandFlag flags, CompanyID company, const std
  * @param text Text content in case it is a text or location page element
  * @return the cost of this operation or an error
  */
-CommandCost CmdCreateStoryPageElement(DoCommandFlag flags, TileIndex tile, StoryPageID page_id, StoryPageElementType type, uint32 reference, const std::string &text)
+std::tuple<CommandCost, StoryPageElementID> CmdCreateStoryPageElement(DoCommandFlag flags, TileIndex tile, StoryPageID page_id, StoryPageElementType type, uint32 reference, const std::string &text)
 {
-	if (!StoryPageElement::CanAllocateItem()) return CMD_ERROR;
+	if (!StoryPageElement::CanAllocateItem()) return { CMD_ERROR, INVALID_STORY_PAGE_ELEMENT };
 
 	/* Allow at most 128 elements per page. */
 	uint16 element_count = 0;
 	for (StoryPageElement *iter : StoryPageElement::Iterate()) {
 		if (iter->page == page_id) element_count++;
 	}
-	if (element_count >= 128) return CMD_ERROR;
+	if (element_count >= 128) return { CMD_ERROR, INVALID_STORY_PAGE_ELEMENT };
+
+	if (_current_company != OWNER_DEITY) return { CMD_ERROR, INVALID_STORY_PAGE_ELEMENT };
+	if (!StoryPage::IsValidID(page_id)) return { CMD_ERROR, INVALID_STORY_PAGE_ELEMENT };
+	if (!VerifyElementContentParameters(page_id, type, tile, reference, text.c_str())) return { CMD_ERROR, INVALID_STORY_PAGE_ELEMENT };
 
-	if (_current_company != OWNER_DEITY) return CMD_ERROR;
-	if (!StoryPage::IsValidID(page_id)) return CMD_ERROR;
-	if (!VerifyElementContentParameters(page_id, type, tile, reference, text.c_str())) return CMD_ERROR;
 
 	if (flags & DC_EXEC) {
 		if (_story_page_element_pool.items == 0) {
@@ -274,11 +273,11 @@ CommandCost CmdCreateStoryPageElement(DoCommandFlag flags, TileIndex tile, Story
 
 		InvalidateWindowClassesData(WC_STORY_BOOK, page_id);
 
-		_new_story_page_element_id = pe->index;
 		_story_page_element_next_sort_value++;
+		return { CommandCost(), pe->index };
 	}
 
-	return CommandCost();
+	return { CommandCost(), INVALID_STORY_PAGE_ELEMENT };
 }
 
 /**
diff --git a/src/story_cmd.h b/src/story_cmd.h
index 9dbfd412a..29b1b45f2 100644
--- a/src/story_cmd.h
+++ b/src/story_cmd.h
@@ -16,8 +16,8 @@
 #include "story_type.h"
 #include "vehicle_type.h"
 
-CommandCost CmdCreateStoryPage(DoCommandFlag flags, CompanyID company, const std::string &text);
-CommandCost CmdCreateStoryPageElement(DoCommandFlag flags, TileIndex tile, StoryPageID page_id, StoryPageElementType type, uint32 reference, const std::string &text);
+std::tuple<CommandCost, StoryPageID> CmdCreateStoryPage(DoCommandFlag flags, CompanyID company, const std::string &text);
+std::tuple<CommandCost, StoryPageElementID> CmdCreateStoryPageElement(DoCommandFlag flags, TileIndex tile, StoryPageID page_id, StoryPageElementType type, uint32 reference, const std::string &text);
 CommandCost CmdUpdateStoryPageElement(DoCommandFlag flags, TileIndex tile, StoryPageElementID page_element_id, uint32 reference, const std::string &text);
 CommandCost CmdSetStoryPageTitle(DoCommandFlag flags, StoryPageID page_id, const std::string &text);
 CommandCost CmdSetStoryPageDate(DoCommandFlag flags, StoryPageID page_id, Date date);
diff --git a/src/story_type.h b/src/story_type.h
index e919564a7..386abe5e2 100644
--- a/src/story_type.h
+++ b/src/story_type.h
@@ -18,8 +18,6 @@ struct StoryPageElement;
 struct StoryPage;
 enum StoryPageElementType : byte;
 
-extern StoryPageElementID _new_story_page_element_id;
-extern StoryPageID _new_story_page_id;
 static const StoryPageElementID INVALID_STORY_PAGE_ELEMENT = 0xFFFF; ///< Constant representing a non-existing story page element.
 static const StoryPageID INVALID_STORY_PAGE = 0xFFFF; ///< Constant representing a non-existing story page.
 
diff --git a/src/terraform_cmd.h b/src/terraform_cmd.h
index 861e0d994..4daeeac48 100644
--- a/src/terraform_cmd.h
+++ b/src/terraform_cmd.h
@@ -21,7 +21,6 @@ DEF_CMD_TRAIT(CMD_TERRAFORM_LAND, CmdTerraformLand, CMD_ALL_TILES | CMD_AUTO,
 DEF_CMD_TRAIT(CMD_LEVEL_LAND,     CmdLevelLand,     CMD_ALL_TILES | CMD_AUTO | CMD_NO_TEST, CMDT_LANDSCAPE_CONSTRUCTION) // test run might clear tiles multiple times, in execution that only happens once
 
 CommandCallback CcPlaySound_EXPLOSION;
-CommandCallback CcPlaceSign;
 CommandCallback CcTerraform;
 
 #endif /* TERRAFORM_CMD_H */
diff --git a/src/town.h b/src/town.h
index e186951e6..294be7b53 100644
--- a/src/town.h
+++ b/src/town.h
@@ -228,7 +228,6 @@ enum TownActions {
 DECLARE_ENUM_AS_BIT_SET(TownActions)
 
 extern const byte _town_action_costs[TACT_COUNT];
-extern TownID _new_town_id;
 
 /**
  * Set the default name for a depot/waypoint
diff --git a/src/town_cmd.cpp b/src/town_cmd.cpp
index ea5a81eb7..5afc1d2c9 100644
--- a/src/town_cmd.cpp
+++ b/src/town_cmd.cpp
@@ -59,8 +59,6 @@
 
 #include "safeguards.h"
 
-TownID _new_town_id;
-
 /* Initialize the town-pool */
 TownPool _town_pool("Town");
 INSTANTIATE_POOL_METHODS(Town)
@@ -1937,41 +1935,41 @@ static bool IsUniqueTownName(const std::string &name)
  * @param text Custom name for the town. If empty, the town name parts will be used.
  * @return the cost of this operation or an error
  */
-CommandCost CmdFoundTown(DoCommandFlag flags, TileIndex tile, TownSize size, bool city, TownLayout layout, bool random_location, uint32 townnameparts, const std::string &text)
+std::tuple<CommandCost, TownID> CmdFoundTown(DoCommandFlag flags, TileIndex tile, TownSize size, bool city, TownLayout layout, bool random_location, uint32 townnameparts, const std::string &text)
 {
 	TownNameParams par(_settings_game.game_creation.town_name);
 
-	if (size >= TSZ_END) return CMD_ERROR;
-	if (layout >= NUM_TLS) return CMD_ERROR;
+	if (size >= TSZ_END) return { CMD_ERROR, INVALID_TOWN };
+	if (layout >= NUM_TLS) return { CMD_ERROR, INVALID_TOWN };
 
 	/* Some things are allowed only in the scenario editor and for game scripts. */
 	if (_game_mode != GM_EDITOR && _current_company != OWNER_DEITY) {
-		if (_settings_game.economy.found_town == TF_FORBIDDEN) return CMD_ERROR;
-		if (size == TSZ_LARGE) return CMD_ERROR;
-		if (random_location) return CMD_ERROR;
+		if (_settings_game.economy.found_town == TF_FORBIDDEN) return { CMD_ERROR, INVALID_TOWN };
+		if (size == TSZ_LARGE) return { CMD_ERROR, INVALID_TOWN };
+		if (random_location) return { CMD_ERROR, INVALID_TOWN };
 		if (_settings_game.economy.found_town != TF_CUSTOM_LAYOUT && layout != _settings_game.economy.town_layout) {
-			return CMD_ERROR;
+			return { CMD_ERROR, INVALID_TOWN };
 		}
 	} else if (_current_company == OWNER_DEITY && random_location) {
 		/* Random parameter is not allowed for Game Scripts. */
-		return CMD_ERROR;
+		return { CMD_ERROR, INVALID_TOWN };
 	}
 
 	if (text.empty()) {
 		/* If supplied name is empty, townnameparts has to generate unique automatic name */
-		if (!VerifyTownName(townnameparts, &par)) return_cmd_error(STR_ERROR_NAME_MUST_BE_UNIQUE);
+		if (!VerifyTownName(townnameparts, &par)) return { CommandCost(STR_ERROR_NAME_MUST_BE_UNIQUE), INVALID_TOWN };
 	} else {
 		/* If name is not empty, it has to be unique custom name */
-		if (Utf8StringLength(text) >= MAX_LENGTH_TOWN_NAME_CHARS) return CMD_ERROR;
-		if (!IsUniqueTownName(text)) return_cmd_error(STR_ERROR_NAME_MUST_BE_UNIQUE);
+		if (Utf8StringLength(text) >= MAX_LENGTH_TOWN_NAME_CHARS) return { CMD_ERROR, INVALID_TOWN };
+		if (!IsUniqueTownName(text)) return { CommandCost(STR_ERROR_NAME_MUST_BE_UNIQUE), INVALID_TOWN };
 	}
 
 	/* Allocate town struct */
-	if (!Town::CanAllocateItem()) return_cmd_error(STR_ERROR_TOO_MANY_TOWNS);
+	if (!Town::CanAllocateItem()) return { CommandCost(STR_ERROR_TOO_MANY_TOWNS), INVALID_TOWN };
 
 	if (!random_location) {
 		CommandCost ret = TownCanBePlacedHere(tile);
-		if (ret.Failed()) return ret;
+		if (ret.Failed()) return { ret, INVALID_TOWN };
 	}
 
 	static const byte price_mult[][TSZ_RANDOM + 1] = {{ 15, 25, 40, 25 }, { 20, 35, 55, 35 }};
@@ -1984,10 +1982,11 @@ CommandCost CmdFoundTown(DoCommandFlag flags, TileIndex tile, TownSize size, boo
 	cost.MultiplyCost(mult);
 
 	/* Create the town */
+	TownID new_town = INVALID_TOWN;
 	if (flags & DC_EXEC) {
 		if (cost.GetCost() > GetAvailableMoneyForCommand()) {
 			_additional_cash_required = cost.GetCost();
-			return CommandCost(EXPENSES_OTHER);
+			return { CommandCost(EXPENSES_OTHER), INVALID_TOWN };
 		}
 
 		Backup<bool> old_generating_world(_generating_world, true, FILE_LINE);
@@ -1998,7 +1997,7 @@ CommandCost CmdFoundTown(DoCommandFlag flags, TileIndex tile, TownSize size, boo
 			if (t == nullptr) {
 				cost = CommandCost(STR_ERROR_NO_SPACE_FOR_TOWN);
 			} else {
-				_new_town_id = t->index;
+				new_town = t->index;
 			}
 		} else {
 			t = new Town(tile);
@@ -2032,7 +2031,7 @@ CommandCost CmdFoundTown(DoCommandFlag flags, TileIndex tile, TownSize size, boo
 			Game::NewEvent(new ScriptEventTownFounded(t->index));
 		}
 	}
-	return cost;
+	return { cost, new_town };
 }
 
 /**
diff --git a/src/town_cmd.h b/src/town_cmd.h
index 4c9782e48..e98fa571e 100644
--- a/src/town_cmd.h
+++ b/src/town_cmd.h
@@ -16,7 +16,7 @@
 
 enum TownEffect : byte;
 
-CommandCost CmdFoundTown(DoCommandFlag flags, TileIndex tile, TownSize size, bool city, TownLayout layout, bool random_location, uint32 townnameparts, const std::string &text);
+std::tuple<CommandCost, TownID> CmdFoundTown(DoCommandFlag flags, TileIndex tile, TownSize size, bool city, TownLayout layout, bool random_location, uint32 townnameparts, const std::string &text);
 CommandCost CmdRenameTown(DoCommandFlag flags, TownID town_id, const std::string &text);
 CommandCost CmdDoTownAction(DoCommandFlag flags, TownID town_id, uint8 action);
 CommandCost CmdTownGrowthRate(DoCommandFlag flags, TownID town_id, uint16 growth_rate);
@@ -37,6 +37,6 @@ DEF_CMD_TRAIT(CMD_EXPAND_TOWN,      CmdExpandTown,     CMD_DEITY,
 DEF_CMD_TRAIT(CMD_DELETE_TOWN,      CmdDeleteTown,     CMD_OFFLINE,              CMDT_LANDSCAPE_CONSTRUCTION)
 
 CommandCallback CcFoundTown;
-CommandCallback CcFoundRandomTown;
+void CcFoundRandomTown(Commands cmd, const CommandCost &result, TownID town_id);
 
 #endif /* TOWN_CMD_H */
diff --git a/src/town_gui.cpp b/src/town_gui.cpp
index 0c5f86ab7..fbc6a842a 100644
--- a/src/town_gui.cpp
+++ b/src/town_gui.cpp
@@ -1017,9 +1017,9 @@ void CcFoundTown(Commands cmd, const CommandCost &result, TileIndex tile)
 	if (!_settings_client.gui.persistent_buildingtools) ResetObjectToPlace();
 }
 
-void CcFoundRandomTown(Commands cmd, const CommandCost &result, TileIndex tile)
+void CcFoundRandomTown(Commands cmd, const CommandCost &result, TownID town_id)
 {
-	if (result.Succeeded()) ScrollMainWindowToTile(Town::Get(_new_town_id)->xy);
+	if (result.Succeeded()) ScrollMainWindowToTile(Town::Get(town_id)->xy);
 }
 
 static const NWidgetPart _nested_found_town_widgets[] = {
@@ -1150,7 +1150,8 @@ public:
 		this->SetDirty();
 	}
 
-	void ExecuteFoundTownCommand(TileIndex tile, bool random, StringID errstr, CommandCallback cc)
+	template <typename Tcallback>
+	void ExecuteFoundTownCommand(TileIndex tile, bool random, StringID errstr, Tcallback cc)
 	{
 		std::string name;