renderer: Fix lock of resource reads in render entity.

Author: heinezen

libopenage/renderer/stages/world/object.cpp

@@ -62,6 +62,7 @@ void WorldObject::fetch_updates(const time::time_t &time) {
 	}
 
 	// Get data from render entity
+	auto read_lock = this->render_entity->get_read_lock();
 	this->ref_id = this->render_entity->get_id();
 	this->position.sync(this->render_entity->get_position());
 	this->animation_info.sync(this->render_entity->get_animation_path(),
@@ -78,6 +79,7 @@ void WorldObject::fetch_updates(const time::time_t &time) {
 								  }),
 	                          this->last_update);
 	this->angle.sync(this->render_entity->get_angle(), this->last_update);
+	read_lock.unlock();
 
 	// Set self to changed so that world renderer can update the renderable
 	this->changed = true;

libopenage/renderer/stages/world/render_entity.cpp

@@ -96,4 +96,8 @@ void WorldRenderEntity::clear_changed_flag() {
 	this->changed = false;
 }
 
+std::shared_lock<std::shared_mutex> WorldRenderEntity::get_read_lock() {
+	return std::shared_lock{this->mutex};
+}
+
 } // namespace openage::renderer::world

libopenage/renderer/stages/world/render_entity.h

@@ -4,6 +4,7 @@
 
 #include <cstdint>
 #include <list>
+#include <mutex>
 #include <shared_mutex>
 #include <string>
 
@@ -105,6 +106,13 @@ class WorldRenderEntity {
 	 */
 	void clear_changed_flag();
 
+	/**
+	 * Get a lock for thread-safe reading from the render entity.
+	 *
+	 * @return Lock for the render entity.
+	 */
+	std::shared_lock<std::shared_mutex> get_read_lock();
+
 private:
 	/**
 	 * Flag for determining if the render entity has been updated by the