From 613ba689ff5883f1ee7f64813c39eeb1be6f483a Mon Sep 17 00:00:00 2001
From: Lars Mueller <appgurulars@gmx.de>
Date: Mon, 28 Jul 2025 09:27:13 +0200
Subject: [PATCH] Work around #16221 by updating parent chains

---
 src/client/content_cao.cpp | 18 ++++++++++++++++++
 src/client/content_cao.h   |  7 +++++++
 2 files changed, 25 insertions(+)

diff --git a/src/client/content_cao.cpp b/src/client/content_cao.cpp
index 81f193e9b..410059354 100644
--- a/src/client/content_cao.cpp
+++ b/src/client/content_cao.cpp
@@ -7,6 +7,7 @@
 #include <ICameraSceneNode.h>
 #include <IMeshManipulator.h>
 #include <IAnimatedMeshSceneNode.h>
+#include <ISceneNode.h>
 #include "client/client.h"
 #include "client/renderingengine.h"
 #include "client/sound.h"
@@ -343,6 +344,18 @@ bool GenericCAO::getSelectionBox(aabb3f *toset) const
 	return true;
 }
 
+void GenericCAO::updateParentChain() const
+{
+	if (!m_matrixnode)
+		return;
+	// Update the entire chain of nodes to ensure absolute position is correct
+	std::vector<scene::ISceneNode *> chain;
+	for (scene::ISceneNode *node = m_matrixnode; node; node = node->getParent())
+		chain.push_back(node);
+	for (auto it = chain.rbegin(); it != chain.rend(); ++it)
+		(*it)->updateAbsolutePosition();
+}
+
 const v3f GenericCAO::getPosition() const
 {
 	if (!getParent())
@@ -350,6 +363,11 @@ const v3f GenericCAO::getPosition() const
 
 	// Calculate real position in world based on MatrixNode
 	if (m_matrixnode) {
+		// FIXME work around #16221 which is caused by the camera position and thus
+		// offset not being in sync with the player (parent) CAO position.
+		// A better solution might restrict this update to the local player only
+		// or keep player and camera position in sync.
+		GenericCAO::updateParentChain();
 		v3s16 camera_offset = m_env->getCameraOffset();
 		return m_matrixnode->getAbsolutePosition() +
 				intToFloat(camera_offset, BS);
diff --git a/src/client/content_cao.h b/src/client/content_cao.h
index 798b1674c..e780cf204 100644
--- a/src/client/content_cao.h
+++ b/src/client/content_cao.h
@@ -149,6 +149,7 @@ private:
 	bool visualExpiryRequired(const ObjectProperties &newprops) const;
 
 public:
+
 	GenericCAO(Client *client, ClientEnvironment *env);
 
 	~GenericCAO();
@@ -299,4 +300,10 @@ public:
 	}
 
 	void updateMeshCulling();
+
+private:
+
+	/// Update the parent chain so getPosition() returns an up to date position.
+	void updateParentChain() const;
+
 };