From d41cec35054a73101ce1f5a1a307a47d817ee06b Mon Sep 17 00:00:00 2001
From: heinezen <heinezen@hotmail.de>
Date: Thu, 3 Oct 2024 14:48:09 +0200
Subject: [PATCH] renderer: Fix lock of resource reads in hud render entity.

---
 libopenage/renderer/stages/hud/object.cpp        | 7 +++++++
 libopenage/renderer/stages/hud/render_entity.cpp | 6 +++++-
 libopenage/renderer/stages/hud/render_entity.h   | 9 ++++++++-
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/libopenage/renderer/stages/hud/object.cpp b/libopenage/renderer/stages/hud/object.cpp
index a5ac552a78..6e23b6663a 100644
--- a/libopenage/renderer/stages/hud/object.cpp
+++ b/libopenage/renderer/stages/hud/object.cpp
@@ -38,8 +38,15 @@ void HudDragObject::fetch_updates(const time::time_t &time) {
 
 	// Get data from render entity
 	this->drag_start = this->render_entity->get_drag_start();
+
+	// Thread-safe access to curves needs a lock on the render entity's mutex
+	auto read_lock = this->render_entity->get_read_lock();
+
 	this->drag_pos.sync(this->render_entity->get_drag_pos() /* , this->last_update */);
 
+	// Unlock the render entity mutex
+	read_lock.unlock();
+
 	// Set self to changed so that world renderer can update the renderable
 	this->changed = true;
 	this->render_entity->clear_changed_flag();
diff --git a/libopenage/renderer/stages/hud/render_entity.cpp b/libopenage/renderer/stages/hud/render_entity.cpp
index 5aaea81a84..2ff3f75649 100644
--- a/libopenage/renderer/stages/hud/render_entity.cpp
+++ b/libopenage/renderer/stages/hud/render_entity.cpp
@@ -24,10 +24,14 @@ void DragRenderEntity::update(const coord::input drag_pos,
 }
 
 const curve::Continuous<coord::input> &DragRenderEntity::get_drag_pos() {
+	std::shared_lock lock{this->mutex};
+
 	return this->drag_pos;
 }
 
-const coord::input &DragRenderEntity::get_drag_start() {
+const coord::input DragRenderEntity::get_drag_start() {
+	std::shared_lock lock{this->mutex};
+
 	return this->drag_start;
 }
 
diff --git a/libopenage/renderer/stages/hud/render_entity.h b/libopenage/renderer/stages/hud/render_entity.h
index bfc255814a..9d15204386 100644
--- a/libopenage/renderer/stages/hud/render_entity.h
+++ b/libopenage/renderer/stages/hud/render_entity.h
@@ -28,6 +28,8 @@ class DragRenderEntity final : public renderer::RenderEntity {
 	 * Update the render entity with information from the gamestate
 	 * or input system.
 	 *
+	 * Updating the render entity with this method is thread-safe.
+	 *
 	 * @param drag_pos Position of the dragged corner.
 	 * @param time Current simulation time.
 	 */
@@ -37,6 +39,9 @@ class DragRenderEntity final : public renderer::RenderEntity {
 	/**
 	 * Get the position of the dragged corner.
 	 *
+	 * Accessing the drag position curve REQUIRES a read lock on the render entity
+	 * (using \p get_read_lock()) to ensure thread safety.
+	 *
 	 * @return Coordinates of the dragged corner.
 	 */
 	const curve::Continuous<coord::input> &get_drag_pos();
@@ -44,9 +49,11 @@ class DragRenderEntity final : public renderer::RenderEntity {
 	/**
 	 * Get the position of the start corner.
 	 *
+	 * Accessing the drag start is thread-safe.
+	 *
 	 * @return Coordinates of the start corner.
 	 */
-	const coord::input &get_drag_start();
+	const coord::input get_drag_start();
 
 private:
 	/**