From 7a1be2aeacf75d68a980b81c88e7929611b26e27 Mon Sep 17 00:00:00 2001
From: NepDisk <16447892+NepDisk@users.noreply.github.com>
Date: Sat, 14 Sep 2024 09:19:22 -0400
Subject: [PATCH] Fix terrain friction and rework closer to sector friction

---
 src/k_terrain.c | 90 ++++++++++++++++++++++++++++++++++++++++++++++++-
 src/k_terrain.h | 20 ++---------
 src/p_map.c     |  2 +-
 3 files changed, 92 insertions(+), 20 deletions(-)

diff --git a/src/k_terrain.c b/src/k_terrain.c
index 62ca483ca..a5e0f7f2a 100644
--- a/src/k_terrain.c
+++ b/src/k_terrain.c
@@ -464,6 +464,87 @@ void K_UpdateMobjTerrain(mobj_t *mo, INT32 flatID)
 	mo->terrain = K_GetTerrainForFlatNum(flatID);
 }
 
+/*--------------------------------------------------
+	void K_SetTerrainFriction(mobj_t *mo)
+
+		Applies friction from Terrain definition.
+	
+		Input Arguments:-
+		mo - The object to apply friction to.
+		
+--------------------------------------------------*/
+static void K_SetTerrainFriction(mobj_t *mo)
+{
+	boolean isPlayer = false;
+	fixed_t strength = mo->terrain->friction;
+	terrain_t *terrain = NULL;
+	fixed_t newFriction = INT32_MAX;
+	fixed_t newMovefactor = INT32_MAX;
+
+	if (mo == NULL || P_MobjWasRemoved(mo) == true)
+	{
+		// Invalid object.
+		return;
+	}
+
+	isPlayer = (mo->player != NULL);
+	terrain = mo->terrain;
+	
+	if (isPlayer && !((terrain->flags & TRF_BYPASSBOOST) 
+		|| (mo->player->invincibilitytimer == 0 && mo->player->hyudorotimer == 0
+		&& mo->player->sneakertimer == 0 && mo->player->growshrinktimer <= 0)))
+	{
+		// I want this to be consistent with sector friction
+		// so boosts bypass friction unless specficied otherwise
+		return;
+	}
+
+	mo->friction = ORIG_FRICTION;
+
+	if (isPlayer == true)
+	{
+		mo->movefactor = FRACUNIT;
+	}
+
+	if (strength > 0) // sludge
+	{
+		strength = strength * 2; // otherwise, the maximum sludginess value is +967...
+	}
+
+	// The following might seem odd. At the time of movement,
+	// the move distance is multiplied by 'friction/0x10000', so a
+	// higher friction value actually means 'less friction'.
+	newFriction = ORIG_FRICTION - FixedMul(0x1EB8, strength) / 0x80; // ORIG_FRICTION is 0xE800
+
+	if (newFriction > FRACUNIT)
+	{
+		newFriction = FRACUNIT;
+	}
+
+	if (newFriction < 0)
+	{
+		newFriction = 0;
+	}
+
+	mo->friction = newFriction;
+
+	if (isPlayer == true)
+	{
+		newMovefactor = FixedDiv(ORIG_FRICTION, newFriction);
+
+		if (newMovefactor < FRACUNIT)
+		{
+			newMovefactor = 19*newMovefactor - 18*FRACUNIT;
+		}
+		else
+		{
+			newMovefactor = FRACUNIT;
+		}
+
+		mo->movefactor = newMovefactor;
+	}
+}
+
 /*--------------------------------------------------
 	void K_ProcessTerrainEffect(mobj_t *mo)
 
@@ -488,6 +569,9 @@ void K_ProcessTerrainEffect(mobj_t *mo)
 
 	terrain = mo->terrain;
 	player = mo->player;
+	
+	if (terrain->friction) // Handle Friction set here so mobjs are affected as well.
+		K_SetTerrainFriction(mo);
 
 	if (player == NULL)
 	{
@@ -676,7 +760,7 @@ void K_ProcessTerrainEffect(mobj_t *mo)
 		if (!terrain->springStrength)
 			K_DoPogoSpring(player->mo, 0, 1);
 		else
-			S_StartSound(mo, sfx_kc2f);
+			S_StartSound(player->mo, sfx_kc2f);
 	}
 
 	// (Offroad is handled elsewhere!)
@@ -1673,6 +1757,10 @@ static void K_ParseTerrainParameter(size_t i, char *param, char *val)
 	{
 		K_FlagBoolean(&terrain->flags, TRF_REMAP, val);
 	}
+	else if (stricmp(param, "fricfix") == 0 || stricmp(param, "frictionfix") == 0 || stricmp(param, "boostbypass") == 0)
+	{
+		K_FlagBoolean(&terrain->flags, TRF_BYPASSBOOST, val);
+	}
 }
 
 /*--------------------------------------------------
diff --git a/src/k_terrain.h b/src/k_terrain.h
index f22db4a94..faae4df18 100644
--- a/src/k_terrain.h
+++ b/src/k_terrain.h
@@ -96,7 +96,8 @@ typedef enum
 	TRF_SNEAKERPANEL = 1<<1, // Texture is a booster
 	TRF_WATERRUNPANEL = 1<<2, // Texture is a waterrun panel
 	TRF_TRIPWIRE = 1<<3, // Texture is a tripwire when used as a midtexture
-	TRF_REMAP = 1<<4 // Texture colors may be remapped with ENCOREMAP or TWEAKMAP
+	TRF_REMAP = 1<<4, // Texture colors may be remapped with ENCOREMAP or TWEAKMAP
+	TRF_BYPASSBOOST = 1<<5 // Texture bypasses boost friction resistence
 } terrain_flags_t;
 
 typedef struct terrain_s
@@ -517,23 +518,6 @@ void K_UpdateMobjTerrain(mobj_t *mo, INT32 flatID);
 void K_ProcessTerrainEffect(mobj_t *mo);
 
 
-/*--------------------------------------------------
-	void K_SetDefaultFriction(mobj_t *mo);
-
-		Resets an object to their default friction values.
-		If they are on terrain with different friction,
-		they will update to that value.
-
-	Input Arguments:-
-		mo - The object to reset the friction values of.
-
-	Return:-
-		None
---------------------------------------------------*/
-
-void K_SetDefaultFriction(mobj_t *mo);
-
-
 /*--------------------------------------------------
 	void K_SpawnSplashForMobj(mobj_t *mo, fixed_t impact);
 
diff --git a/src/p_map.c b/src/p_map.c
index bc977db93..63d28f86c 100644
--- a/src/p_map.c
+++ b/src/p_map.c
@@ -614,7 +614,7 @@ static BlockItReturn_t PIT_CheckThing(mobj_t *thing)
 			return BMIT_CONTINUE; // underneath
 		if (thing->player && thing->flags & MF_SHOOTABLE && tm.thing->health > 0)
 		{
-			UINT32 damagetype = (tm.thing->info->mass & 0xFF);
+			UINT32 damagetype = (tm.thing->info->mass & DMG_TYPEMASK);
 			P_DamageMobj(thing, tm.thing, tm.thing, 1, damagetype);
 		}
 		return BMIT_CONTINUE;