From 4a78062f5438ff55d14f9607dc40e32c6e776cc3 Mon Sep 17 00:00:00 2001
From: Matt <5415177+ZehMatt@users.noreply.github.com>
Date: Sun, 17 Nov 2024 19:49:47 +0200
Subject: [PATCH] Fix #23206: Desyncs when using uncapped FPS

Because the position is one tick behind the spatial mapping was incorrect, it's not allowed to modify that during interpolation.
---
 distribution/changelog.txt             |  1 +
 src/openrct2/entity/EntityRegistry.cpp | 20 ++++++++++----------
 src/openrct2/entity/EntityRegistry.h   |  1 -
 src/openrct2/entity/EntityTweener.cpp  |  6 +-----
 4 files changed, 12 insertions(+), 16 deletions(-)

diff --git a/distribution/changelog.txt b/distribution/changelog.txt
index 758103600b..7411f41770 100644
--- a/distribution/changelog.txt
+++ b/distribution/changelog.txt
@@ -3,6 +3,7 @@
 - Feature: [#23166] Add Galician translation.
 - Improved: [#23051] Add large sloped turns and new inversions to the Twister, Vertical Drop, Hyper and Flying Roller Coasters.
 - Improved: [#23123] Improve sorting of roller coasters in build new ride menu.
+- Fix: [#23206] Multiplayer desyncs when FPS is uncapped.
 
 0.4.16 (2024-11-03)
 ------------------------------------------------------------------------
diff --git a/src/openrct2/entity/EntityRegistry.cpp b/src/openrct2/entity/EntityRegistry.cpp
index b3a5f76991..4d7e883689 100644
--- a/src/openrct2/entity/EntityRegistry.cpp
+++ b/src/openrct2/entity/EntityRegistry.cpp
@@ -481,6 +481,16 @@ void EntityBase::SetLocation(const CoordsXYZ& newLocation)
     SpatialIndex |= kSpatialIndexDirtyMask;
 }
 
+static void EntitySetCoordinates(const CoordsXYZ& entityPos, EntityBase* entity)
+{
+    auto screenCoords = Translate3DTo2DWithZ(GetCurrentRotation(), entityPos);
+
+    entity->SpriteData.SpriteRect = ScreenRect(
+        screenCoords - ScreenCoordsXY{ entity->SpriteData.Width, entity->SpriteData.HeightMin },
+        screenCoords + ScreenCoordsXY{ entity->SpriteData.Width, entity->SpriteData.HeightMax });
+    entity->SetLocation(entityPos);
+}
+
 void EntityBase::MoveTo(const CoordsXYZ& newLocation)
 {
     if (x != kLocationNull)
@@ -506,16 +516,6 @@ void EntityBase::MoveTo(const CoordsXYZ& newLocation)
     }
 }
 
-void EntitySetCoordinates(const CoordsXYZ& entityPos, EntityBase* entity)
-{
-    auto screenCoords = Translate3DTo2DWithZ(GetCurrentRotation(), entityPos);
-
-    entity->SpriteData.SpriteRect = ScreenRect(
-        screenCoords - ScreenCoordsXY{ entity->SpriteData.Width, entity->SpriteData.HeightMin },
-        screenCoords + ScreenCoordsXY{ entity->SpriteData.Width, entity->SpriteData.HeightMax });
-    entity->SetLocation(entityPos);
-}
-
 /**
  * Frees any dynamically attached memory to the entity, such as peep name.
  */
diff --git a/src/openrct2/entity/EntityRegistry.h b/src/openrct2/entity/EntityRegistry.h
index b33230e710..a370f38f44 100644
--- a/src/openrct2/entity/EntityRegistry.h
+++ b/src/openrct2/entity/EntityRegistry.h
@@ -67,7 +67,6 @@ void ResetAllEntities();
 void ResetEntitySpatialIndices();
 void UpdateAllMiscEntities();
 void UpdateMoneyEffect();
-void EntitySetCoordinates(const CoordsXYZ& entityPos, EntityBase* entity);
 void EntityRemove(EntityBase* entity);
 uint16_t RemoveFloatingEntities();
 void UpdateEntitiesSpatialIndex();
diff --git a/src/openrct2/entity/EntityTweener.cpp b/src/openrct2/entity/EntityTweener.cpp
index 52bc453237..acd5e38ccf 100644
--- a/src/openrct2/entity/EntityTweener.cpp
+++ b/src/openrct2/entity/EntityTweener.cpp
@@ -101,8 +101,6 @@ void EntityTweener::Tween(float alpha)
                       static_cast<int32_t>(std::round(posB.y * alpha + posA.y * inv)),
                       static_cast<int32_t>(std::round(posB.z * alpha + posA.z * inv)) });
     }
-
-    UpdateEntitiesSpatialIndex();
 }
 
 void EntityTweener::Restore()
@@ -113,9 +111,7 @@ void EntityTweener::Restore()
         if (ent == nullptr)
             continue;
 
-        ent->Invalidate();
-        EntitySetCoordinates(PostPos[i], ent);
-        ent->Invalidate();
+        ent->MoveTo(PostPos[i]);
     }
 }