From 0a258f95ea6466daa5366065a826c0f78a333411 Mon Sep 17 00:00:00 2001
From: Christoph Oelckers <coelckers@zdoom.fake>
Date: Fri, 9 Aug 2013 16:25:16 +0200
Subject: [PATCH] - added gravity property to UDMF things. Positive values are
 multiplied with the class's gravity property, negative values are used as
 their absolute.

---
 specs/udmf_zdoom.txt | 2 ++
 src/doomdata.h       | 1 +
 src/p_buildmap.cpp   | 1 +
 src/p_mobj.cpp       | 4 ++++
 src/p_setup.cpp      | 2 ++
 src/p_udmf.cpp       | 6 ++++++
 6 files changed, 16 insertions(+)

diff --git a/specs/udmf_zdoom.txt b/specs/udmf_zdoom.txt
index 4fc57f8565..a6d8acb5df 100644
--- a/specs/udmf_zdoom.txt
+++ b/specs/udmf_zdoom.txt
@@ -204,6 +204,8 @@ Note: All <bool> fields default to false unless mentioned otherwise.
                                 // Parameter is the conversation ID, 0 meaning none.
       countsecret = <bool>;     // Picking up this actor counts as a secret.
       arg0str = <string>;       // Alternate string-based version of arg0
+	  gravity = <float>;		// Set per-actor gravity. Positive values are multiplied with the class's property, 
+	                            // negative values are used as their absolute. Default = 1.0.
 
       * Note about arg0str
 
diff --git a/src/doomdata.h b/src/doomdata.h
index eeff13e2e5..46af9d6a4f 100644
--- a/src/doomdata.h
+++ b/src/doomdata.h
@@ -342,6 +342,7 @@ struct FMapThing
 	int			special;
 	int			args[5];
 	int			Conversation;
+	fixed_t		gravity;
 
 	void Serialize (FArchive &);
 };
diff --git a/src/p_buildmap.cpp b/src/p_buildmap.cpp
index 417343f211..f2fd7b0bf8 100644
--- a/src/p_buildmap.cpp
+++ b/src/p_buildmap.cpp
@@ -698,6 +698,7 @@ static int LoadSprites (spritetype *sprites, Xsprite *xsprites, int numsprites,
 		mapthings[count].SkillFilter = 0xffff;
 		mapthings[count].flags = MTF_SINGLE|MTF_COOPERATIVE|MTF_DEATHMATCH;
 		mapthings[count].special = 0;
+		mapthings[count].gravity = FRACUNIT;
 
 		if (xsprites != NULL && sprites[i].lotag == 710)
 		{ // Blood ambient sound
diff --git a/src/p_mobj.cpp b/src/p_mobj.cpp
index 3b11ec415d..14607a6823 100644
--- a/src/p_mobj.cpp
+++ b/src/p_mobj.cpp
@@ -4712,6 +4712,10 @@ AActor *P_SpawnMapThing (FMapThing *mthing, int position)
 	mobj->SpawnPoint[2] = mthing->z;
 	mobj->SpawnAngle = mthing->angle;
 	mobj->SpawnFlags = mthing->flags;
+	if (mthing->gravity < 0) mobj->gravity = -mthing->gravity;
+	else if (mthing->gravity > 0) mobj->gravity = FixedMul(mobj->gravity, mthing->gravity);
+	else mobj->flags &= ~MF_NOGRAVITY;
+
 	P_FindFloorCeiling(mobj, FFCF_SAMESECTOR | FFCF_ONLY3DFLOORS | FFCF_3DRESTRICT);
 
 	if (!(mobj->flags2 & MF2_ARGSDEFINED))
diff --git a/src/p_setup.cpp b/src/p_setup.cpp
index 2535641a59..784e6946fd 100644
--- a/src/p_setup.cpp
+++ b/src/p_setup.cpp
@@ -1750,6 +1750,7 @@ void P_LoadThings (MapData * map)
 
 		memset (&mti[i], 0, sizeof(mti[i]));
 
+		mti[i].gravity = FRACUNIT;
 		mti[i].Conversation = 0;
 		mti[i].SkillFilter = MakeSkill(flags);
 		mti[i].ClassFilter = 0xffff;	// Doom map format doesn't have class flags so spawn for all player classes
@@ -1825,6 +1826,7 @@ void P_LoadThings2 (MapData * map)
 		mti[i].ClassFilter = (mti[i].flags & MTF_CLASS_MASK) >> MTF_CLASS_SHIFT;
 		mti[i].flags &= ~(MTF_SKILLMASK|MTF_CLASS_MASK);
 		mti[i].Conversation = 0;
+		mti[i].gravity = FRACUNIT;
 	}
 	delete[] mtp;
 }
diff --git a/src/p_udmf.cpp b/src/p_udmf.cpp
index 91e4c85650..6d935ba63e 100644
--- a/src/p_udmf.cpp
+++ b/src/p_udmf.cpp
@@ -475,6 +475,7 @@ public:
 		FString arg0str, arg1str;
 
 		memset(th, 0, sizeof(*th));
+		th->gravity = FRACUNIT;
 		sc.MustGetToken('{');
 		while (!sc.CheckToken('}'))
 		{
@@ -515,6 +516,11 @@ public:
 				th->special = CheckInt(key);
 				break;
 
+			case NAME_Gravity:
+				CHECK_N(Zd | Zdt)
+				th->gravity = CheckFixed(key);
+				break;
+
 			case NAME_Arg0:
 			case NAME_Arg1:
 			case NAME_Arg2: