From 32313adde6237d53c7a94963af071bced7c74151 Mon Sep 17 00:00:00 2001
From: NepDisk <nepdisk@noreply.codeberg.org>
Date: Fri, 1 Aug 2025 16:45:51 -0400
Subject: [PATCH] Add mobj_t.gravity

https://codeberg.org/srb2classic/srb2classic/pulls/39
---
 src/lua_mobjlib.c |  8 ++++++++
 src/p_mobj.c      |  3 ++-
 src/p_mobj.h      |  1 +
 src/p_saveg.c     | 17 ++++++++++++++++-
 4 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/src/lua_mobjlib.c b/src/lua_mobjlib.c
index 2c1412683..fa83ec123 100644
--- a/src/lua_mobjlib.c
+++ b/src/lua_mobjlib.c
@@ -83,6 +83,7 @@ enum mobj_e {
 	mobj_tracer,
 	mobj_friction,
 	mobj_movefactor,
+	mobj_gravity,
 	mobj_fuse,
 	mobj_watertop,
 	mobj_waterbottom,
@@ -171,6 +172,7 @@ static const char *const mobj_opt[] = {
 	"tracer",
 	"friction",
 	"movefactor",
+	"gravity",
 	"fuse",
 	"watertop",
 	"waterbottom",
@@ -479,6 +481,9 @@ static int mobj_get(lua_State *L)
 	case mobj_movefactor:
 		lua_pushfixed(L, mo->movefactor);
 		break;
+	case mobj_gravity:
+		lua_pushfixed(L, mo->gravity);
+		break;
 	case mobj_fuse:
 		lua_pushinteger(L, mo->fuse);
 		break;
@@ -955,6 +960,9 @@ static int mobj_set(lua_State *L)
 	case mobj_movefactor:
 		mo->movefactor = luaL_checkfixed(L, 3);
 		break;
+	case mobj_gravity:
+		mo->gravity = luaL_checkfixed(L, 3);
+		break;
 	case mobj_fuse:
 		mo->fuse = luaL_checkinteger(L, 3);
 		break;
diff --git a/src/p_mobj.c b/src/p_mobj.c
index afd1dc364..abe8fee73 100644
--- a/src/p_mobj.c
+++ b/src/p_mobj.c
@@ -1143,7 +1143,7 @@ fixed_t P_GetMobjGravity(mobj_t *mo)
 	if (!gravsector) // If there is no 3D floor gravity, check sector's gravity
 		gravsector = mo->subsector->sector;
 
-	gravityadd = -FixedMul(gravity, P_GetSectorGravityFactor(gravsector));
+	gravityadd = -FixedMul(FixedMul(gravity, mo->gravity), P_GetSectorGravityFactor(gravsector));
 
 	if ((gravsector->flags & MSF_GRAVITYFLIP) && gravityadd > 0)
 	{
@@ -10909,6 +10909,7 @@ mobj_t *P_SpawnMobj(fixed_t x, fixed_t y, fixed_t z, mobjtype_t type)
 	mobj->friction = ORIG_FRICTION;
 
 	mobj->movefactor = FRACUNIT;
+	mobj->gravity = FRACUNIT;
 
 	// All mobjs are created at 100% scale.
 	mobj->scale = FRACUNIT;
diff --git a/src/p_mobj.h b/src/p_mobj.h
index 11df861ed..1e3346681 100644
--- a/src/p_mobj.h
+++ b/src/p_mobj.h
@@ -386,6 +386,7 @@ struct mobj_t
 
 	fixed_t friction;
 	fixed_t movefactor;
+	fixed_t gravity;
 	fixed_t lastmomz;
 
 	INT32 fuse; // Does something in P_MobjThinker on reaching 0.
diff --git a/src/p_saveg.c b/src/p_saveg.c
index c9c2aac7b..7887a7a67 100644
--- a/src/p_saveg.c
+++ b/src/p_saveg.c
@@ -2069,7 +2069,8 @@ typedef enum
 	MD2_ITNEXT       = 1<<27,
 	MD2_LASTMOMZ     = 1<<28,
 	MD2_TERRAIN      = 1<<29,
-	MD2_LIGHTLEVEL   = (INT32)(1U<<30),
+	MD2_LIGHTLEVEL   = 1<<30,
+	MD2_GRAVITY      = (INT32)(1U<<31)
 } mobj_diff2_t;
 
 typedef enum
@@ -2375,6 +2376,8 @@ static void SaveMobjThinker(savebuffer_t *save, const thinker_t *th, const UINT8
 		diff2 |= MD2_LASTMOMZ;
 	if (mobj->terrain != NULL || mobj->terrainOverlay != NULL)
 		diff2 |= MD2_TERRAIN;
+	if (mobj->gravity != FRACUNIT)
+		diff2 |= MD2_GRAVITY;
 
 	if (diff2 != 0)
 		diff |= MD_MORE;
@@ -2641,6 +2644,10 @@ static void SaveMobjThinker(savebuffer_t *save, const thinker_t *th, const UINT8
 		WRITEUINT32(save->p, K_GetTerrainHeapIndex(mobj->terrain));
 		WRITEUINT32(save->p, SaveMobjnum(mobj->terrainOverlay));
 	}
+	if (diff2 & MD2_GRAVITY)
+	{
+		WRITEFIXED(save->p, mobj->gravity);
+	}
 
 	WRITEUINT32(save->p, mobj->mobjnum);
 }
@@ -3882,6 +3889,14 @@ static thinker_t* LoadMobjThinker(savebuffer_t *save, actionf_p1 thinker)
 	{
 		mobj->terrain = NULL;
 	}
+	if (diff2 & MD2_GRAVITY)
+	{
+		mobj->gravity = READFIXED(save->p);
+	}
+	else
+	{
+		mobj->gravity = FRACUNIT;
+	}
 
 	// Reset some non-synch values
 	mobj->sloperoll = 0;