Do not replace equivalent navmesh tiles

components/CMakeLists.txt

@@ -182,6 +182,7 @@ add_component_dir(detournavigator
     navigator
     findrandompointaroundcircle
     raycast
+    navmeshtileview
     )
 
 set (ESM_UI ${CMAKE_SOURCE_DIR}/files/ui/contentselector.ui

components/detournavigator/navmeshcacheitem.hpp

@@ -5,6 +5,7 @@
 #include "tileposition.hpp"
 #include "navmeshtilescache.hpp"
 #include "dtstatus.hpp"
+#include "navmeshtileview.hpp"
 
 #include <components/misc/guarded.hpp>
 
@@ -141,6 +142,12 @@ namespace DetourNavigator
         template <class T>
         UpdateNavMeshStatus updateTile(const TilePosition& position, T&& navMeshData)
         {
+            const dtMeshTile* currentTile = getTile(position);
+            if (currentTile != nullptr
+                && asNavMeshTileConstView(*currentTile) == asNavMeshTileConstView(getRawData(navMeshData)))
+            {
+                return UpdateNavMeshStatus::ignored;
+            }
             const auto removed = removeTileImpl(position);
             const auto addStatus = addTileImpl(getRawData(navMeshData), getSize(navMeshData));
             if (dtStatusSucceed(addStatus))
@@ -206,6 +213,12 @@ namespace DetourNavigator
             int* const dataSize = nullptr;
             return dtStatusSucceed(mImpl->removeTile(tileRef, data, dataSize));
         }
+
+        const dtMeshTile* getTile(const TilePosition& position) const
+        {
+            const int layer = 0;
+            return mImpl->getTileAt(position.x(), position.y(), layer);
+        }
     };
 
     using GuardedNavMeshCacheItem = Misc::ScopeGuarded<NavMeshCacheItem>;

components/detournavigator/navmeshtileview.cpp

@@ -0,0 +1,183 @@
+#include "navmeshtileview.hpp"
+
+#include <DetourCommon.h>
+#include <DetourNavMesh.h>
+
+#include <algorithm>
+#include <cassert>
+#include <stdexcept>
+#include <tuple>
+
+namespace
+{
+    template <typename T>
+    struct Ref
+    {
+        T& mRef;
+
+        explicit Ref(T& ref) : mRef(ref) {}
+
+        friend bool operator==(const Ref& lhs, const Ref& rhs)
+        {
+            return lhs.mRef == rhs.mRef;
+        }
+    };
+
+    template <typename T, std::size_t size>
+    struct ArrayRef
+    {
+        T (&mRef)[size];
+
+        explicit ArrayRef(T (&ref)[size]) : mRef(ref) {}
+
+        friend bool operator==(const ArrayRef& lhs, const ArrayRef& rhs)
+        {
+            return std::equal(std::begin(lhs.mRef), std::end(lhs.mRef), std::begin(rhs.mRef));
+        }
+    };
+
+    template <typename T>
+    struct Span
+    {
+        T* mBegin;
+        T* mEnd;
+
+        explicit Span(T* data, int size) : mBegin(data), mEnd(data + static_cast<std::size_t>(size)) {}
+
+        friend bool operator==(const Span& lhs, const Span& rhs)
+        {
+            // size is already equal if headers are equal
+            assert((lhs.mEnd - lhs.mBegin) == (rhs.mEnd - rhs.mBegin));
+            return std::equal(lhs.mBegin, lhs.mEnd, rhs.mBegin);
+        }
+    };
+
+    auto makeTuple(const dtMeshHeader& v)
+    {
+        return std::tuple(
+            v.x,
+            v.y,
+            v.layer,
+            v.userId,
+            v.polyCount,
+            v.vertCount,
+            v.maxLinkCount,
+            v.detailMeshCount,
+            v.detailVertCount,
+            v.detailTriCount,
+            v.bvNodeCount,
+            v.offMeshConCount,
+            v.offMeshBase,
+            v.walkableHeight,
+            v.walkableRadius,
+            v.walkableClimb,
+            v.detailVertCount,
+            ArrayRef(v.bmin),
+            ArrayRef(v.bmax),
+            v.bvQuantFactor
+        );
+    }
+
+    auto makeTuple(const dtPoly& v)
+    {
+        return std::tuple(ArrayRef(v.verts), ArrayRef(v.neis), v.flags, v.vertCount, v.areaAndtype);
+    }
+
+    auto makeTuple(const dtPolyDetail& v)
+    {
+        return std::tuple(v.vertBase, v.triBase, v.vertCount, v.triCount);
+    }
+
+    auto makeTuple(const dtBVNode& v)
+    {
+        return std::tuple(ArrayRef(v.bmin), ArrayRef(v.bmax), v.i);
+    }
+
+    auto makeTuple(const dtOffMeshConnection& v)
+    {
+        return std::tuple(ArrayRef(v.pos), v.rad, v.poly, v.flags, v.side, v.userId);
+    }
+
+    auto makeTuple(const DetourNavigator::NavMeshTileConstView& v)
+    {
+        return std::tuple(
+            Ref(*v.mHeader),
+            Span(v.mPolys, v.mHeader->polyCount),
+            Span(v.mVerts, v.mHeader->vertCount),
+            Span(v.mDetailMeshes, v.mHeader->detailMeshCount),
+            Span(v.mDetailVerts, v.mHeader->detailVertCount),
+            Span(v.mDetailTris, v.mHeader->detailTriCount),
+            Span(v.mBvTree, v.mHeader->bvNodeCount),
+            Span(v.mOffMeshCons, v.mHeader->offMeshConCount)
+        );
+    }
+}
+
+template <class T>
+inline auto operator==(const T& lhs, const T& rhs)
+    -> std::enable_if_t<std::is_same_v<std::void_t<decltype(makeTuple(lhs))>, void>, bool>
+{
+    return makeTuple(lhs) == makeTuple(rhs);
+}
+
+namespace DetourNavigator
+{
+    NavMeshTileConstView asNavMeshTileConstView(const unsigned char* data)
+    {
+        const dtMeshHeader* header = reinterpret_cast<const dtMeshHeader*>(data);
+
+        if (header->magic != DT_NAVMESH_MAGIC)
+            throw std::logic_error("Invalid navmesh magic");
+
+        if (header->version != DT_NAVMESH_VERSION)
+            throw std::logic_error("Invalid navmesh version");
+
+        // Similar code to https://github.com/recastnavigation/recastnavigation/blob/c5cbd53024c8a9d8d097a4371215e3342d2fdc87/Detour/Source/DetourNavMesh.cpp#L978-L996
+        const int headerSize = dtAlign4(sizeof(dtMeshHeader));
+        const int vertsSize = dtAlign4(sizeof(float) * 3 * header->vertCount);
+        const int polysSize = dtAlign4(sizeof(dtPoly) * header->polyCount);
+        const int linksSize = dtAlign4(sizeof(dtLink) * (header->maxLinkCount));
+        const int detailMeshesSize = dtAlign4(sizeof(dtPolyDetail) * header->detailMeshCount);
+        const int detailVertsSize = dtAlign4(sizeof(float) * 3 * header->detailVertCount);
+        const int detailTrisSize = dtAlign4(sizeof(unsigned char) * 4 * header->detailTriCount);
+        const int bvtreeSize = dtAlign4(sizeof(dtBVNode) * header->bvNodeCount);
+        const int offMeshLinksSize = dtAlign4(sizeof(dtOffMeshConnection) * header->offMeshConCount);
+
+        const unsigned char* ptr = data + headerSize;
+
+        NavMeshTileConstView view;
+
+        view.mHeader = header;
+        view.mVerts = dtGetThenAdvanceBufferPointer<const float>(ptr, vertsSize);
+        view.mPolys = dtGetThenAdvanceBufferPointer<const dtPoly>(ptr, polysSize);
+        ptr += linksSize;
+        view.mDetailMeshes = dtGetThenAdvanceBufferPointer<const dtPolyDetail>(ptr, detailMeshesSize);
+        view.mDetailVerts = dtGetThenAdvanceBufferPointer<const float>(ptr, detailVertsSize);
+        view.mDetailTris = dtGetThenAdvanceBufferPointer<const unsigned char>(ptr, detailTrisSize);
+        view.mBvTree = dtGetThenAdvanceBufferPointer<const dtBVNode>(ptr, bvtreeSize);
+        view.mOffMeshCons = dtGetThenAdvanceBufferPointer<const dtOffMeshConnection>(ptr, offMeshLinksSize);
+
+        return view;
+    }
+
+    NavMeshTileConstView asNavMeshTileConstView(const dtMeshTile& tile)
+    {
+        NavMeshTileConstView view;
+
+        view.mHeader = tile.header;
+        view.mPolys = tile.polys;
+        view.mVerts = tile.verts;
+        view.mDetailMeshes = tile.detailMeshes;
+        view.mDetailVerts = tile.detailVerts;
+        view.mDetailTris = tile.detailTris;
+        view.mBvTree = tile.bvTree;
+        view.mOffMeshCons = tile.offMeshCons;
+
+        return view;
+    }
+
+    bool operator==(const NavMeshTileConstView& lhs, const NavMeshTileConstView& rhs)
+    {
+        return makeTuple(lhs) == makeTuple(rhs);
+    }
+}

components/detournavigator/navmeshtileview.hpp

@@ -0,0 +1,31 @@
+#ifndef OPENMW_COMPONENTS_DETOURNAVIGATOR_NAVMESHTILEVIEW_H
+#define OPENMW_COMPONENTS_DETOURNAVIGATOR_NAVMESHTILEVIEW_H
+
+struct dtMeshHeader;
+struct dtPoly;
+struct dtPolyDetail;
+struct dtBVNode;
+struct dtOffMeshConnection;
+struct dtMeshTile;
+
+namespace DetourNavigator
+{
+    struct NavMeshTileConstView
+    {
+        const dtMeshHeader* mHeader;
+        const dtPoly* mPolys;
+        const float* mVerts;
+        const dtPolyDetail* mDetailMeshes;
+        const float* mDetailVerts;
+        const unsigned char* mDetailTris;
+        const dtBVNode* mBvTree;
+        const dtOffMeshConnection* mOffMeshCons;
+
+        friend bool operator==(const NavMeshTileConstView& lhs, const NavMeshTileConstView& rhs);
+    };
+
+    NavMeshTileConstView asNavMeshTileConstView(const unsigned char* data);
+    NavMeshTileConstView asNavMeshTileConstView(const dtMeshTile& tile);
+}
+
+#endif