From 55add9883f07d49f88b16fe764a897cdc24ba8bf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=CE=B6eh=20Matt?= <5415177+ZehMatt@users.noreply.github.com>
Date: Tue, 24 Aug 2021 13:57:13 -0700
Subject: [PATCH] Implement DirectionFlipXAxis

---
 src/openrct2/interface/Viewport.cpp | 4 +---
 src/openrct2/paint/Paint.cpp        | 7 ++-----
 src/openrct2/world/Location.hpp     | 8 ++++++++
 3 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/src/openrct2/interface/Viewport.cpp b/src/openrct2/interface/Viewport.cpp
index 6aa028ae56..4f68f8ba27 100644
--- a/src/openrct2/interface/Viewport.cpp
+++ b/src/openrct2/interface/Viewport.cpp
@@ -1148,11 +1148,9 @@ void rct_viewport::Invalidate() const
 
 CoordsXY viewport_coord_to_map_coord(const ScreenCoordsXY& coords, int32_t z)
 {
-    constexpr uint8_t inverseRotationMapping[NumOrthogonalDirections] = { 0, 3, 2, 1 };
-
     // Reverse of translate_3d_to_2d_with_z
     CoordsXY ret = { coords.y - coords.x / 2 + z, coords.y + coords.x / 2 + z };
-    auto inverseRotation = inverseRotationMapping[get_current_rotation()];
+    auto inverseRotation = DirectionFlipXAxis(get_current_rotation());
     return ret.Rotate(inverseRotation);
 }
 
diff --git a/src/openrct2/paint/Paint.cpp b/src/openrct2/paint/Paint.cpp
index 45b8a63e88..a27565383e 100644
--- a/src/openrct2/paint/Paint.cpp
+++ b/src/openrct2/paint/Paint.cpp
@@ -145,7 +145,7 @@ static paint_struct* CreateNormalPaintStruct(
         return nullptr;
     }
 
-    const uint8_t swappedRotation = (session->CurrentRotation * 3) % 4; // swaps 1 and 3
+    const auto swappedRotation = DirectionFlipXAxis(session->CurrentRotation);
     auto swappedRotCoord = CoordsXYZ{ offset.Rotate(swappedRotation), offset.z };
     swappedRotCoord += session->SpritePosition;
 
@@ -231,10 +231,7 @@ template<uint8_t direction> void PaintSessionGenerateRotate(paint_session* sessi
 void PaintSessionGenerate(paint_session* session)
 {
     session->CurrentRotation = get_current_rotation();
-
-    // Extracted from viewport_coord_to_map_coord
-    constexpr uint8_t inverseRotationMapping[NumOrthogonalDirections] = { 0, 3, 2, 1 };
-    switch (inverseRotationMapping[session->CurrentRotation])
+    switch (DirectionFlipXAxis(session->CurrentRotation))
     {
         case 0:
             PaintSessionGenerateRotate<0>(session);
diff --git a/src/openrct2/world/Location.hpp b/src/openrct2/world/Location.hpp
index 560bcb91e8..120cb502d7 100644
--- a/src/openrct2/world/Location.hpp
+++ b/src/openrct2/world/Location.hpp
@@ -545,6 +545,14 @@ constexpr Direction ALL_DIRECTIONS[] = { 0, 1, 2, 3 };
     }
 }
 
+/*
+ * Flips the X axis so 1 and 3 are swapped 0 and 2 will stay the same.
+ */
+inline constexpr Direction DirectionFlipXAxis(Direction direction)
+{
+    return (direction * 3) % 4;
+}
+
 struct CoordsXYZD : public CoordsXYZ
 {
     Direction direction{};