From 0495190a0890270cb41689474b4ed75290a2727d Mon Sep 17 00:00:00 2001
From: NepDisk <nepdisk@noreply.codeberg.org>
Date: Thu, 13 Mar 2025 05:36:35 -0400
Subject: [PATCH] Fix Stepup issues for the most aprt.

This fixes midtexture stepover and extreme stepup such as the jank line in greenhils
---
 src/p_map.c | 105 ++++++++++++++++++++++++++++++++--------------------
 1 file changed, 65 insertions(+), 40 deletions(-)

diff --git a/src/p_map.c b/src/p_map.c
index d2bf1a689..6d06a7a33 100644
--- a/src/p_map.c
+++ b/src/p_map.c
@@ -2520,6 +2520,20 @@ fixed_t P_GetThingStepUp(mobj_t *thing, fixed_t destX, fixed_t destY)
 	return maxstep;
 }
 
+// Used for averging height values for step up.
+static fixed_t avgheight(fixed_t a, fixed_t b)
+{
+	if (((b > 0) && (a > (INT32_MAX - b))) ||
+	((b < 0) && (a < (INT32_MIN - b))))
+	{
+		return b + (a - b) / 2;
+	}
+	else
+	{
+		return (a + b) / 2;
+	}
+}
+
 static boolean
 increment_move
 (		mobj_t * thing,
@@ -2624,51 +2638,62 @@ increment_move
 
 			thingtop = thing->z + thing->height;
 
-			// Step up
-			if (thing->z < g_tm.floorz)
+			if (maxstep > 0)
 			{
-				if (g_tm.floorz - thing->z <= maxstep)
-				{
-					thing->z = thing->floorz = g_tm.floorz;
-					thing->eflags |= MFE_JUSTSTEPPEDDOWN;
-				}
-				else
-				{
-					return false; // mobj must raise itself to fit
-				}
-			}
-			else if (g_tm.ceilingz < thingtop)
-			{
-				if (thingtop - g_tm.ceilingz <= maxstep)
-				{
-					thing->z = ( thing->ceilingz = g_tm.ceilingz ) - thing->height;
-					thing->eflags |= MFE_JUSTSTEPPEDDOWN;
-				}
-				else
-				{
-					return false; // mobj must lower itself to fit
-				}
-			}
-			else if (maxstep > 0 && !(
-				thing->player && (
-				P_MobjTouchingSectorSpecialFlag(thing, SSF_NOSTEPDOWN)
-					|| (R_PointInSubsector(x, y)->sector->specialflags & SSF_NOSTEPDOWN))
-				)) // Step down
-			{
-				// If the floor difference is MAXSTEPMOVE or less, and the sector isn't Section1:14, ALWAYS
-				// step down! Formerly required a Section1:13 sector for the full MAXSTEPMOVE, but no more.
+				fixed_t stepheight;
 
-				if (thingtop == thing->ceilingz && g_tm.ceilingz > thingtop && g_tm.ceilingz - thingtop <= maxstep)
+				// Step up
+				if (thing->z < g_tm.floorz)
 				{
-					thing->z = (thing->ceilingz = g_tm.ceilingz) - thing->height;
-					thing->eflags |= MFE_JUSTSTEPPEDDOWN;
-					thing->ceilingdrop = 0;
+					stepheight = avgheight(g_tm.floorz - thing->z, g_tm.floorstep);
+
+					if (stepheight <= maxstep)
+					{
+						thing->z = thing->floorz = g_tm.floorz;
+						thing->floorrover = g_tm.floorrover;
+						thing->eflags |= MFE_JUSTSTEPPEDDOWN;
+					}
+					else
+					{
+						return false; // mobj must raise itself to fit
+					}
 				}
-				else if (thing->z == thing->floorz && g_tm.floorz < thing->z && thing->z - g_tm.floorz <= maxstep)
+				else if (g_tm.ceilingz < thingtop)
 				{
-					thing->z = thing->floorz = g_tm.floorz;
-					thing->eflags |= MFE_JUSTSTEPPEDDOWN;
-					thing->floordrop = 0;
+					stepheight = avgheight(thingtop - g_tm.ceilingz, g_tm.ceilingstep);
+
+					if (stepheight <= maxstep)
+					{
+						thing->z = ( thing->ceilingz = g_tm.ceilingz ) - thing->height;
+						thing->ceilingrover = g_tm.ceilingrover;
+						thing->eflags |= MFE_JUSTSTEPPEDDOWN;
+					}
+					else
+					{
+						return false; // mobj must lower itself to fit
+					}
+				}
+				else if (thing->momz * P_MobjFlip(thing) <= 0 // Step down requires moving down.
+					&& !(P_MobjTouchingSectorSpecialFlag(thing, SSF_NOSTEPDOWN)
+					|| (R_PointInSubsector(x, y)->sector->specialflags & SSF_NOSTEPDOWN)))
+				{
+					// If the floor difference is MAXSTEPMOVE or less, and the sector isn't Section1:14, ALWAYS
+					// step down! Formerly required a Section1:13 sector for the full MAXSTEPMOVE, but no more.
+
+					if (thingtop == thing->ceilingz && g_tm.ceilingz > thingtop && g_tm.ceilingz - thingtop <= maxstep)
+					{
+						thing->z = (thing->ceilingz = g_tm.ceilingz) - thing->height;
+						thing->ceilingrover = g_tm.ceilingrover;
+						thing->eflags |= MFE_JUSTSTEPPEDDOWN;
+						thing->ceilingdrop = 0;
+					}
+					else if (thing->z == thing->floorz && g_tm.floorz < thing->z && thing->z - g_tm.floorz <= maxstep)
+					{
+						thing->z = thing->floorz = g_tm.floorz;
+						thing->floorrover = g_tm.floorrover;
+						thing->eflags |= MFE_JUSTSTEPPEDDOWN;
+						thing->floordrop = 0;
+					}
 				}
 			}