From acc9dffab7f33d70435a8ebc86ff778b3687e0d4 Mon Sep 17 00:00:00 2001
From: Jonathan G Rennison <j.g.rennison@gmail.com>
Date: Mon, 24 Jan 2022 01:18:35 +0000
Subject: [PATCH] Add object mapped variables for slope after foundation
 applied

---
 src/newgrf_extension.cpp |  2 ++
 src/newgrf_extension.h   |  2 ++
 src/newgrf_object.cpp    | 22 ++++++++++++++++++++++
 src/object_cmd.cpp       |  4 ++--
 4 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/src/newgrf_extension.cpp b/src/newgrf_extension.cpp
index 908ee081a9..dee1d52b93 100644
--- a/src/newgrf_extension.cpp
+++ b/src/newgrf_extension.cpp
@@ -79,6 +79,8 @@ extern const GRFPropertyMapDefinition _grf_action0_remappable_properties[] = {
 
 /** Action14 Action2 remappable variable list */
 extern const GRFVariableMapDefinition _grf_action2_remappable_variables[] = {
+	GRFVariableMapDefinition(GSF_OBJECTS, A2VRI_OBJECT_FOUNDATION_SLOPE, "object_foundation_tile_slope"),
+	GRFVariableMapDefinition(GSF_OBJECTS, A2VRI_OBJECT_FOUNDATION_SLOPE_CHANGE, "object_foundation_change_tile_slope"),
 	GRFVariableMapDefinition(),
 };
 
diff --git a/src/newgrf_extension.h b/src/newgrf_extension.h
index f36d182e61..e5f069a84e 100644
--- a/src/newgrf_extension.h
+++ b/src/newgrf_extension.h
@@ -39,6 +39,8 @@ enum Action0RemapPropertyIds {
 
 
 enum Action2VariableRemapIds {
+	A2VRI_OBJECT_FOUNDATION_SLOPE = 0x100,
+	A2VRI_OBJECT_FOUNDATION_SLOPE_CHANGE,
 };
 
 /** Action14 feature definition */
diff --git a/src/newgrf_object.cpp b/src/newgrf_object.cpp
index ba09802c07..01e3f36970 100644
--- a/src/newgrf_object.cpp
+++ b/src/newgrf_object.cpp
@@ -22,6 +22,7 @@
 #include "water.h"
 #include "clear_func.h"
 #include "newgrf_animation_base.h"
+#include "newgrf_extension.h"
 
 #include "safeguards.h"
 
@@ -263,6 +264,12 @@ static uint32 GetCountAndDistanceOfClosestInstance(byte local_id, uint32 grfid,
 			/* Object view */
 			case 0x48: return this->view;
 
+			case A2VRI_OBJECT_FOUNDATION_SLOPE:
+				return GetTileSlope(this->tile);
+
+			case A2VRI_OBJECT_FOUNDATION_SLOPE_CHANGE:
+				return 0;
+
 			/*
 			 * Disallow the rest:
 			 * 0x40: Relative position is passed as parameter during construction.
@@ -333,6 +340,21 @@ static uint32 GetCountAndDistanceOfClosestInstance(byte local_id, uint32 grfid,
 
 		/* Count of object, distance of closest instance */
 		case 0x64: return GetCountAndDistanceOfClosestInstance(parameter, this->ro.grffile->grfid, this->tile, this->obj);
+
+		case A2VRI_OBJECT_FOUNDATION_SLOPE: {
+			extern Foundation GetFoundation_Object(TileIndex tile, Slope tileh);
+			Slope slope = GetTileSlope(this->tile);
+			ApplyFoundationToSlope(GetFoundation_Object(this->tile, slope), &slope);
+			return slope;
+		}
+
+		case A2VRI_OBJECT_FOUNDATION_SLOPE_CHANGE: {
+			extern Foundation GetFoundation_Object(TileIndex tile, Slope tileh);
+			Slope slope = GetTileSlope(this->tile);
+			Slope orig_slope = slope;
+			ApplyFoundationToSlope(GetFoundation_Object(this->tile, slope), &slope);
+			return slope ^ orig_slope;
+		}
 	}
 
 unhandled:
diff --git a/src/object_cmd.cpp b/src/object_cmd.cpp
index e0d46b92b1..3aa8c2da17 100644
--- a/src/object_cmd.cpp
+++ b/src/object_cmd.cpp
@@ -566,7 +566,7 @@ CommandCost CmdBuildObjectArea(TileIndex tile, DoCommandFlag flags, uint32 p1, u
 }
 
 
-static Foundation GetFoundation_Object(TileIndex tile, Slope tileh);
+Foundation GetFoundation_Object(TileIndex tile, Slope tileh);
 
 static void DrawTile_Object(TileInfo *ti, DrawTileProcParams params)
 {
@@ -670,7 +670,7 @@ static int GetSlopePixelZ_Object(TileIndex tile, uint x, uint y)
 	}
 }
 
-static Foundation GetFoundation_Object(TileIndex tile, Slope tileh)
+Foundation GetFoundation_Object(TileIndex tile, Slope tileh)
 {
 	if (tileh == SLOPE_FLAT) return FOUNDATION_NONE;
 	switch (GetObjectEffectiveFoundationType(tile)) {