From e8140ae3883f3618aa423407d2d8492b2fb78749 Mon Sep 17 00:00:00 2001
From: Antonio Martinez <aj@worldsbe.st>
Date: Mon, 2 Jun 2025 12:02:58 -0400
Subject: [PATCH] Relink player to kartitems

---
 src/lua_mobjlib.c |  8 ++++++++
 src/p_mobj.c      | 15 +++++++++++++++
 src/p_mobj.h      |  2 ++
 src/p_saveg.cpp   | 11 +++++++++++
 4 files changed, 36 insertions(+)

diff --git a/src/lua_mobjlib.c b/src/lua_mobjlib.c
index 158909815..dd80daf66 100644
--- a/src/lua_mobjlib.c
+++ b/src/lua_mobjlib.c
@@ -111,6 +111,7 @@ enum mobj_e {
 	mobj_reappear,
 	mobj_punt_ref,
 	mobj_owner,
+	mobj_relinkplayer,
 };
 
 static const char *const mobj_opt[] = {
@@ -201,6 +202,7 @@ static const char *const mobj_opt[] = {
 	"reappear",
 	"punt_ref",
 	"owner",
+	"relinkplayer",
 	NULL};
 
 #define UNIMPLEMENTED luaL_error(L, LUA_QL("mobj_t") " field " LUA_QS " is not implemented for Lua and cannot be accessed.", mobj_opt[field])
@@ -519,6 +521,9 @@ static int mobj_get(lua_State *L)
 		}
 		LUA_PushUserdata(L, mo->owner, META_MOBJ);
 		break;
+	case mobj_relinkplayer:
+		lua_pushinteger(L, mo->relinkplayer);
+		break;
 	default: // extra custom variables in Lua memory
 		lua_getfield(L, LUA_REGISTRYINDEX, LREG_EXTVARS);
 		I_Assert(lua_istable(L, -1));
@@ -934,6 +939,9 @@ static int mobj_set(lua_State *L)
 			P_SetTarget(&mo->owner, owner);
 		}
 		break;
+	case mobj_relinkplayer:
+		mo->relinkplayer = luaL_checkinteger(L, 3);
+		break;
 	default:
 		lua_getfield(L, LUA_REGISTRYINDEX, LREG_EXTVARS);
 		I_Assert(lua_istable(L, -1));
diff --git a/src/p_mobj.c b/src/p_mobj.c
index 98d377637..0040ccad9 100644
--- a/src/p_mobj.c
+++ b/src/p_mobj.c
@@ -10353,9 +10353,24 @@ void P_MobjThinker(mobj_t *mobj)
 	I_Assert(mobj != NULL);
 	I_Assert(!P_MobjWasRemoved(mobj));
 
+	if (P_IsKartItem(mobj->type) && mobj->target && !P_MobjWasRemoved(mobj->target))
+	{
+		player_t *link = mobj->target->player;
+		if (link && playeringame[link-players] && !link->spectator)
+			mobj->relinkplayer = (link-players) + 1;
+	}
+
 	// Remove dead target/tracer.
 	if (mobj->target && P_MobjWasRemoved(mobj->target))
+	{
 		P_SetTarget(&mobj->target, NULL);
+		if (P_IsKartItem(mobj->type) && mobj->relinkplayer && mobj->relinkplayer <= MAXPLAYERS)
+		{
+			player_t *relink = &players[mobj->relinkplayer-1];
+			if (playeringame[relink-players] && !relink->spectator && relink->mo && !P_MobjWasRemoved(relink->mo))
+				P_SetTarget(&mobj->target, relink->mo);
+		}
+	}
 	if (mobj->tracer && P_MobjWasRemoved(mobj->tracer))
 		P_SetTarget(&mobj->tracer, NULL);
 	if (mobj->hnext && P_MobjWasRemoved(mobj->hnext))
diff --git a/src/p_mobj.h b/src/p_mobj.h
index 08b41922e..353011ddf 100644
--- a/src/p_mobj.h
+++ b/src/p_mobj.h
@@ -450,6 +450,8 @@ struct mobj_t
 
 	INT32 po_movecount; // Polyobject carrying (NOT savegame, NOT Lua)
 
+	UINT8 relinkplayer; // reassociate kartitem target when it dies. ACHTUNG 1-INDEXED
+
 	// WARNING: New fields must be added separately to savegame and Lua.
 };
 
diff --git a/src/p_saveg.cpp b/src/p_saveg.cpp
index 7fc84d0f8..6e39c8174 100644
--- a/src/p_saveg.cpp
+++ b/src/p_saveg.cpp
@@ -2999,6 +2999,7 @@ typedef enum
 	MD3_REAPPEAR		= 1<<1,
 	MD3_PUNT_REF		= 1<<2,
 	MD3_OWNER			= 1<<3,
+	MD3_RELINK_PLAYER	= 1<<4,
 } mobj_diff3_t;
 
 typedef enum
@@ -3322,6 +3323,8 @@ static void SaveMobjThinker(savebuffer_t *save, const thinker_t *th, const UINT8
 		diff3 |= MD3_PUNT_REF;
 	if (mobj->owner)
 		diff3 |= MD3_OWNER;
+	if (mobj->relinkplayer)
+		diff3 |= MD3_RELINK_PLAYER;
 
 	if (diff3 != 0)
 		diff2 |= MD2_MORE;
@@ -3612,6 +3615,10 @@ static void SaveMobjThinker(savebuffer_t *save, const thinker_t *th, const UINT8
 	{
 		WRITEUINT32(save->p, mobj->owner->mobjnum);
 	}
+	if (diff3 & MD3_RELINK_PLAYER)
+	{
+		WRITEUINT8(save->p, mobj->relinkplayer);
+	}
 
 	WRITEUINT32(save->p, mobj->mobjnum);
 }
@@ -4925,6 +4932,10 @@ static thinker_t* LoadMobjThinker(savebuffer_t *save, actionf_p1 thinker)
 	{
 		mobj->owner = (mobj_t *)(size_t)READUINT32(save->p);
 	}
+	if (diff3 & MD3_OWNER)
+	{
+		mobj->relinkplayer = READUINT8(save->p);
+	}
 
 	// link tid set earlier
 	P_AddThingTID(mobj);