Lua: add lua_data

config/fxdata/lua/classes/Thing.lua

@@ -24,6 +24,7 @@
 ---@field health integer
 ---@field max_health integer If the health gets beyond this point, it will be decreased.
 ---@field picked_up boolean
+---@field lua_data table A table that can be used to store any Lua data on the thing. arbitrary data accessible from all Lua code.
 if not Thing then Thing = {} end
 
 ---@class Object: Thing

config/fxdata/lua/triggers/Builtins.lua

@@ -2,7 +2,7 @@
 -- Entry points for engine-triggered events (e.g. OnPowerCast, OnGameTick).
 -- These functions are called by the C engine and dispatch event data to the Lua trigger system.
 
----@alias event_type "PowerCast"|"Death"|"SpecialActivated"|"GameTick"|"ChatMsg"|"DungeonDestroyed"|"TrapPlaced"|"ApplyDamage"|"LevelUp"|"Rebirth"|"SlabKindChange"|"SlabOwnerChange"|"RoomOwnerChange"|"ShotHitThing"|"Destroyed"
+---@alias event_type "PowerCast"|"Death"|"SpecialActivated"|"GameTick"|"ChatMsg"|"DungeonDestroyed"|"TrapPlaced"|"ApplyDamage"|"LevelUp"|"Rebirth"|"SlabKindChange"|"SlabOwnerChange"|"RoomOwnerChange"|"ShotHitThing"|"Destroyed"|"ThingDeleted"
 
 --- Called when a spell is cast on a unit
 --- @param pwkind power_kind
@@ -153,4 +153,12 @@ function OnShotHit(shot, shooter, target, next_stl_x, next_stl_y, rebound_hit)
     eventData.next_stl_y = next_stl_y
     eventData.rebound_hit = rebound_hit
     ProcessEvent("ShotHitThing",eventData)
+end
+
+--- Called when a thing is deleted
+---@param thing Thing the thing being deleted.
+function OnThingDeleted(thing)
+    local eventData = {}
+    eventData.thing = thing
+    ProcessEvent("ThingDeleted",eventData)
 end

config/fxdata/lua/triggers/Events.lua

@@ -265,4 +265,18 @@ function RegisterOnShotHitEvent(action, shooter_type, target_type, shot_type)
         TriggerAddCondition(trigger, function(eventData, triggerData) return eventData.shot.model == triggerData.shot_type end)
     end
     return trigger
+end
+
+---Triggers when a shot hits something
+---eventData.thing contains the deleted thing
+---@param action function|string the function to call when the event happens
+---@param thing? Thing the thing that was deleted (nil for any)
+---@return table
+function RegisterThingDeletedEvent(action, thing)
+    local trigData = {thing = thing}
+    local trigger = CreateTrigger("ThingDeleted", action, trigData)
+    if thing then
+        TriggerAddCondition(trigger, function(eventData, triggerData) return eventData.thing == triggerData.thing end)
+    end
+    return trigger
 end

src/lua_api_things.c

@@ -32,12 +32,63 @@
 #include "lua_utils.h"
 
 
+#include "lua_api.h"
+
 #include "post_inc.h"
 
 /**********************************************/
 static int thing_set_field(lua_State *L);
 static int thing_get_field(lua_State *L);
 
+static void get_or_create_lua_data_table(lua_State *L, struct Thing* thing) {
+    // Get the global Game table
+    lua_getglobal(L, "Game");
+    if (!lua_istable(L, -1)) {
+        lua_pop(L, 1); // Pop whatever is on top
+        lua_newtable(L);
+        lua_setglobal(L, "Game");
+        lua_getglobal(L, "Game");
+    }
+
+    // Get or create Game.LuaData
+    lua_getfield(L, -1, "LuaData");
+    if (!lua_istable(L, -1)) {
+        lua_pop(L, 1); // Pop nil
+        lua_newtable(L);
+        lua_setfield(L, -2, "LuaData"); // Set Game.LuaData
+        lua_getfield(L, -1, "LuaData");
+    }
+
+    // Get or create Game.LuaData.Thing
+    lua_getfield(L, -1, "Thing");
+    if (!lua_istable(L, -1)) {
+        lua_pop(L, 1); // Pop nil
+        lua_newtable(L);
+        lua_setfield(L, -2, "Thing"); // Set Game.LuaData.Thing
+        lua_getfield(L, -1, "Thing");
+    }
+
+    // Now Game.LuaData.Thing is at the top of the stack.
+    // Create a unique key for the thing's data table
+    char key[40];
+    snprintf(key, sizeof(key), "thing_%d_%d", thing->index, thing->creation_turn);
+
+    // Get or create the specific table for this thing
+    lua_getfield(L, -1, key);
+    if (lua_isnil(L, -1)) {
+        lua_pop(L, 1); // Pop nil
+        lua_newtable(L);
+        lua_setfield(L, -2, key); // Set Game.LuaData.Thing[key]
+        lua_getfield(L, -1, key);
+    }
+
+    // The desired table is now at the top of the stack.
+    // We need to clean up the stack, leaving only the thing's data table.
+    lua_remove(L, -2); // Remove Game.LuaData.Thing
+    lua_remove(L, -2); // Remove Game.LuaData
+    lua_remove(L, -2); // Remove Game
+}
+
 static const struct luaL_Reg thing_methods[];
 
 
@@ -481,6 +532,8 @@ static int thing_get_field(lua_State *L) {
         lua_pushboolean(L, thing_is_picked_up(thing));
     } else if (strcmp(key, "thing_class") == 0) {
         lua_pushstring(L, thing_class_code_name(thing->class_id));
+    } else if (strcmp(key, "lua_data") == 0) {
+        get_or_create_lua_data_table(L, thing);
     } else if (try_get_from_methods(L, 1, key)) {
         return 1;
     }

src/lua_triggers.c

@@ -23,6 +23,40 @@
 
 #include "post_inc.h"
 
+static void delete_thing_lua_data(lua_State *L, struct Thing* thing) {
+
+    // Get Game.LuaData.Thing table
+    lua_getglobal(L, "Game");
+    if (!lua_istable(L, -1)) { lua_pop(L, 1); return; }
+    lua_getfield(L, -1, "LuaData");
+    if (!lua_istable(L, -1)) { lua_pop(L, 2); return; }
+    lua_getfield(L, -1, "Thing");
+    if (!lua_istable(L, -1)) { lua_pop(L, 3); return; }
+
+    char key[40];
+    snprintf(key, sizeof(key), "thing_%d_%d", thing->index, thing->creation_turn);
+    lua_pushnil(L);
+    lua_setfield(L, -2, key);
+
+    lua_pop(L, 3);
+}
+
+void lua_on_thing_deleted(struct Thing *thing)
+{
+	SYNCDBG(6, "Starting");
+	delete_thing_lua_data(Lvl_script, thing);
+	lua_getglobal(Lvl_script, "OnThingDeleted");
+	if (lua_isfunction(Lvl_script, -1))
+	{
+		lua_pushThing(Lvl_script, thing);
+		CheckLua(Lvl_script, lua_pcall(Lvl_script, 1, 0, 0), "OnThingDeleted");
+	}
+	else
+	{
+		lua_pop(Lvl_script, 1);
+	}
+}
+
 void lua_on_dungeon_destroyed(PlayerNumber plyr_idx)
 {
 	SYNCDBG(6,"Starting");

src/lua_triggers.h

@@ -43,6 +43,7 @@ void lua_on_slab_kind_change(MapSlabCoord slb_x, MapSlabCoord slb_y, SlabKind ol
 void lua_on_slab_owner_change(MapSlabCoord slb_x, MapSlabCoord slb_y, PlayerNumber old_owner);
 void lua_on_room_owner_change(struct Room *room, PlayerNumber old_owner);
 void lua_on_shot_hit(struct Thing *shot, struct Thing *shooter, struct Thing *target, MapSubtlCoord next_stl_x, MapSubtlCoord next_stl_y, bool rebound_hit);
+void lua_on_thing_deleted(struct Thing *thing);
 
 #ifdef __cplusplus
 }

src/thing_data.c

@@ -36,6 +36,7 @@
 #include "engine_arrays.h"
 #include "kjm_input.h"
 #include "gui_topmsg.h"
+#include "lua_triggers.h"
 #include "post_inc.h"
 
 #ifdef __cplusplus
@@ -159,6 +160,7 @@ void delete_thing_structure_f(struct Thing *thing, TbBool deleting_everything, c
         remove_first_creature(thing);
     }
     if (!deleting_everything) {
+        lua_on_thing_deleted(thing);
         struct CreatureControl *cctrl = creature_control_get_from_thing(thing);
         if (!creature_control_invalid(cctrl)) {
             if (creature_under_spell_effect(thing, CSAfF_Armour)) {