From 7290ce81c04de5bbda719d02612d79b764017f76 Mon Sep 17 00:00:00 2001
From: elsid <elsid.mail@gmail.com>
Date: Sun, 29 Oct 2023 13:38:20 +0100
Subject: [PATCH] Avoid allocating std::vector for a single element

---
 apps/openmw/mwworld/cellpreloader.cpp | 12 ++++++------
 apps/openmw/mwworld/cellpreloader.hpp |  3 ++-
 apps/openmw/mwworld/scene.cpp         |  9 ++++-----
 3 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/apps/openmw/mwworld/cellpreloader.cpp b/apps/openmw/mwworld/cellpreloader.cpp
index 4357f8ba57..2881471b25 100644
--- a/apps/openmw/mwworld/cellpreloader.cpp
+++ b/apps/openmw/mwworld/cellpreloader.cpp
@@ -165,12 +165,12 @@ namespace MWWorld
     class TerrainPreloadItem : public SceneUtil::WorkItem
     {
     public:
-        TerrainPreloadItem(const std::vector<osg::ref_ptr<Terrain::View>>& views, Terrain::World* world,
-            const std::vector<PositionCellGrid>& preloadPositions)
+        explicit TerrainPreloadItem(const std::vector<osg::ref_ptr<Terrain::View>>& views, Terrain::World* world,
+            std::span<const PositionCellGrid> preloadPositions)
             : mAbort(false)
             , mTerrainViews(views)
             , mWorld(world)
-            , mPreloadPositions(preloadPositions)
+            , mPreloadPositions(preloadPositions.begin(), preloadPositions.end())
         {
         }
 
@@ -380,10 +380,10 @@ namespace MWWorld
             mTerrainPreloadItem->abort();
             mTerrainPreloadItem->waitTillDone();
         }
-        setTerrainPreloadPositions(std::vector<PositionCellGrid>());
+        setTerrainPreloadPositions({});
     }
 
-    void CellPreloader::setTerrainPreloadPositions(const std::vector<PositionCellGrid>& positions)
+    void CellPreloader::setTerrainPreloadPositions(std::span<const PositionCellGrid> positions)
     {
         if (positions.empty())
         {
@@ -404,7 +404,7 @@ namespace MWWorld
                     mTerrainViews.emplace_back(mTerrain->createView());
             }
 
-            mTerrainPreloadPositions = positions;
+            mTerrainPreloadPositions.assign(positions.begin(), positions.end());
             if (!positions.empty())
             {
                 mTerrainPreloadItem = new TerrainPreloadItem(mTerrainViews, mTerrain, positions);
diff --git a/apps/openmw/mwworld/cellpreloader.hpp b/apps/openmw/mwworld/cellpreloader.hpp
index f8b5c87c39..405ba96a2e 100644
--- a/apps/openmw/mwworld/cellpreloader.hpp
+++ b/apps/openmw/mwworld/cellpreloader.hpp
@@ -8,6 +8,7 @@
 #include <osg/ref_ptr>
 
 #include <map>
+#include <span>
 
 namespace osg
 {
@@ -77,7 +78,7 @@ namespace MWWorld
 
         void setWorkQueue(osg::ref_ptr<SceneUtil::WorkQueue> workQueue);
 
-        void setTerrainPreloadPositions(const std::vector<PositionCellGrid>& positions);
+        void setTerrainPreloadPositions(std::span<const PositionCellGrid> positions);
 
         void syncTerrainLoad(Loading::Listener& listener);
         void abortTerrainPreloadExcept(const PositionCellGrid* exceptPos);
diff --git a/apps/openmw/mwworld/scene.cpp b/apps/openmw/mwworld/scene.cpp
index c918e2d78e..202b500fdd 100644
--- a/apps/openmw/mwworld/scene.cpp
+++ b/apps/openmw/mwworld/scene.cpp
@@ -1232,10 +1232,9 @@ namespace MWWorld
     void Scene::preloadTerrain(const osg::Vec3f& pos, ESM::RefId worldspace, bool sync)
     {
         ESM::ExteriorCellLocation cellPos = ESM::positionToExteriorCellLocation(pos.x(), pos.y(), worldspace);
-        std::vector<PositionCellGrid> vec;
-        vec.emplace_back(pos, gridCenterToBounds({ cellPos.mX, cellPos.mY }));
-        mPreloader->abortTerrainPreloadExcept(vec.data());
-        mPreloader->setTerrainPreloadPositions(vec);
+        const PositionCellGrid position{ pos, gridCenterToBounds({ cellPos.mX, cellPos.mY }) };
+        mPreloader->abortTerrainPreloadExcept(&position);
+        mPreloader->setTerrainPreloadPositions(std::span(&position, 1));
         if (!sync)
             return;
 
@@ -1249,7 +1248,7 @@ namespace MWWorld
 
     void Scene::reloadTerrain()
     {
-        mPreloader->setTerrainPreloadPositions(std::vector<PositionCellGrid>());
+        mPreloader->setTerrainPreloadPositions({});
     }
 
     struct ListFastTravelDestinationsVisitor