From 03d7418f51ac6016ea0b0ccf24a7b16475651ad2 Mon Sep 17 00:00:00 2001
From: Christoph Oelckers <c.oelckers@zdoom.fake>
Date: Thu, 21 Jan 2016 10:23:20 +0100
Subject: [PATCH] - fixed: Since sector movement is done after P_PlayerThink is
 called, any player position change induced by this is not factored into
 player_t::viewz and needs to be added explicitly.

This fixes the infamous 'view squats down a bit when riding up an elevator' effect. It is also there in the other cases but far less pronounced.
---
 src/p_map.cpp | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/src/p_map.cpp b/src/p_map.cpp
index 43c7f6af0..d096beb0d 100644
--- a/src/p_map.cpp
+++ b/src/p_map.cpp
@@ -5268,6 +5268,7 @@ int P_PushDown(AActor *thing, FChangePosition *cpos)
 void PIT_FloorDrop(AActor *thing, FChangePosition *cpos)
 {
 	fixed_t oldfloorz = thing->floorz;
+	fixed_t oldz = thing->Z();
 
 	P_AdjustFloorCeil(thing, cpos);
 
@@ -5297,6 +5298,10 @@ void PIT_FloorDrop(AActor *thing, FChangePosition *cpos)
 			P_CheckFakeFloorTriggers(thing, oldz);
 		}
 	}
+	if (thing->player && thing->player->mo == thing)
+	{
+		thing->player->viewz += thing->Z() - oldz;
+	}
 }
 
 //=============================================================================
@@ -5348,6 +5353,10 @@ void PIT_FloorRaise(AActor *thing, FChangePosition *cpos)
 		thing->SetZ(oldz);
 		break;
 	}
+	if (thing->player && thing->player->mo == thing)
+	{
+		thing->player->viewz += thing->Z() - oldz;
+	}
 }
 
 //=============================================================================
@@ -5359,6 +5368,7 @@ void PIT_FloorRaise(AActor *thing, FChangePosition *cpos)
 void PIT_CeilingLower(AActor *thing, FChangePosition *cpos)
 {
 	bool onfloor;
+	fixed_t oldz = thing->Z();
 
 	onfloor = thing->Z() <= thing->floorz;
 	P_AdjustFloorCeil(thing, cpos);
@@ -5395,6 +5405,10 @@ void PIT_CeilingLower(AActor *thing, FChangePosition *cpos)
 			break;
 		}
 	}
+	if (thing->player && thing->player->mo == thing)
+	{
+		thing->player->viewz += thing->Z() - oldz;
+	}
 }
 
 //=============================================================================
@@ -5406,6 +5420,7 @@ void PIT_CeilingLower(AActor *thing, FChangePosition *cpos)
 void PIT_CeilingRaise(AActor *thing, FChangePosition *cpos)
 {
 	bool isgood = P_AdjustFloorCeil(thing, cpos);
+	fixed_t oldz = thing->Z();
 
 	if (thing->flags4 & MF4_ACTLIKEBRIDGE) return; // do not move bridge things
 
@@ -5432,6 +5447,10 @@ void PIT_CeilingRaise(AActor *thing, FChangePosition *cpos)
 			thing->SetZ( MIN(thing->ceilingz - thing->height, onmobj->Top()));
 		}
 	}
+	if (thing->player && thing->player->mo == thing)
+	{
+		thing->player->viewz += thing->Z() - oldz;
+	}
 }
 
 //=============================================================================