From 8426ce8d9cf48e0e87adc77698b439f5add38549 Mon Sep 17 00:00:00 2001
From: toasterbabe <rollerorbital@gmail.com>
Date: Thu, 30 Jun 2016 23:23:50 +0100
Subject: [PATCH] Minor change to fans and gas jets that makes them work on
 slopes.

- Now checks whether the player's top is below the bottom of the fan/gas jet, instead of its bottom. zdist calculation not affected.
- mo->standingslope is NULL'd so the player isn't launched off at a wacky angle. (I also did this for springs, since Prime mentioned it was a problem for them too.)
---
 src/p_map.c  | 14 +++++++++++---
 src/p_mobj.c |  6 +++---
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/src/p_map.c b/src/p_map.c
index 8621ba20..1f2d903e 100644
--- a/src/p_map.c
+++ b/src/p_map.c
@@ -129,6 +129,10 @@ boolean P_DoSpring(mobj_t *spring, mobj_t *object)
 		return false;
 	}
 
+#ifdef ESLOPE
+	object->standingslope = NULL; // Okay, now we can't return - no launching off at silly angles for you.
+#endif
+
 	object->eflags |= MFE_SPRUNG; // apply this flag asap!
 	spring->flags &= ~(MF_SOLID|MF_SPECIAL); // De-solidify
 
@@ -232,20 +236,24 @@ static void P_DoFanAndGasJet(mobj_t *spring, mobj_t *object)
 	if (p && object->state == &states[object->info->painstate]) // can't use fans and gas jets when player is in pain!
 		return;
 
-	// is object below thruster's position? if not, calculate distance between their bottoms
+	// is object's top below thruster's position? if not, calculate distance between their bottoms
 	if (spring->eflags & MFE_VERTICALFLIP)
 	{
-		if (object->z + object->height > spring->z + spring->height)
+		if (object->z > spring->z + spring->height)
 			return;
 		zdist = (spring->z + spring->height) - (object->z + object->height);
 	}
 	else
 	{
-		if (object->z < spring->z)
+		if (object->z + object->height < spring->z)
 			return;
 		zdist = object->z - spring->z;
 	}
 
+#ifdef ESLOPE
+	object->standingslope = NULL; // No launching off at silly angles for you.
+#endif
+
 	switch (spring->type)
 	{
 		case MT_FAN: // fan
diff --git a/src/p_mobj.c b/src/p_mobj.c
index c6fed993..62dee0a6 100644
--- a/src/p_mobj.c
+++ b/src/p_mobj.c
@@ -2376,9 +2376,9 @@ static boolean P_ZMovement(mobj_t *mo)
 
 #ifdef ESLOPE
 		P_CheckPosition(mo, mo->x, mo->y); // Sets mo->standingslope correctly
-		if ((mo->eflags & MFE_VERTICALFLIP) ? tmceilingslope : tmfloorslope) {
+		if (((mo->eflags & MFE_VERTICALFLIP) ? tmceilingslope : tmfloorslope) && (mo->type != MT_STEAM))
+		{
 			mo->standingslope = (mo->eflags & MFE_VERTICALFLIP) ? tmceilingslope : tmfloorslope;
-
 			P_ReverseQuantizeMomentumToSlope(&mom, mo->standingslope);
 		}
 #endif
@@ -2532,7 +2532,7 @@ static boolean P_ZMovement(mobj_t *mo)
 			mom.z = tmfloorthing->momz;
 
 #ifdef ESLOPE
-		if (mo->standingslope) {
+		if (mo->standingslope) { // MT_STEAM will never have a standingslope, see above.
 			P_QuantizeMomentumToSlope(&mom, mo->standingslope);
 		}
 #endif