From 8244ba8957403c6a6b0e0981b97547f9a8fbadc8 Mon Sep 17 00:00:00 2001
From: cc9cii <cc9c@iinet.net.au>
Date: Tue, 10 Aug 2021 19:39:46 +1000
Subject: [PATCH] Erase old record instead (i.e. assume an empty Pathgrid
 record was placed in purpose)

---
 apps/openmw/mwworld/store.cpp | 38 +++++++++++++++++++++++++++++++----
 1 file changed, 34 insertions(+), 4 deletions(-)

diff --git a/apps/openmw/mwworld/store.cpp b/apps/openmw/mwworld/store.cpp
index 5b223544b0..957a01faf6 100644
--- a/apps/openmw/mwworld/store.cpp
+++ b/apps/openmw/mwworld/store.cpp
@@ -866,10 +866,6 @@ namespace MWWorld
 
         pathgrid.load(esm, isDeleted);
 
-        // deal with MODs that have empty pathgrid records (Issue #6209)
-        if (pathgrid.mPoints.empty() || pathgrid.mEdges.empty())
-            return RecordId("", isDeleted);
-
         // Unfortunately the Pathgrid record model does not specify whether the pathgrid belongs to an interior or exterior cell.
         // For interior cells, mCell is the cell name, but for exterior cells it is either the cell name or if that doesn't exist, the cell's region name.
         // mX and mY will be (0,0) for interior cells, but there is also an exterior cell with the coordinates of (0,0), so that doesn't help.
@@ -877,6 +873,40 @@ namespace MWWorld
         // A proper fix should be made for future versions of the file format.
         bool interior = pathgrid.mData.mX == 0 && pathgrid.mData.mY == 0 && mCells->search(pathgrid.mCell) != nullptr;
 
+        // deal with MODs that have empty pathgrid records (Issue #6209)
+        // we assume that these records are empty on purpose (i.e. to remove old pathgrid on an updated cell)
+        if (pathgrid.mPoints.empty() || pathgrid.mEdges.empty())
+        {
+            std::string contentfile = esm.getContext().filename;
+            size_t pos = contentfile.find_last_of("/\\");
+            if (pos != std::string::npos)
+                contentfile = contentfile.substr(pos+1);
+
+            if (interior)
+            {
+                Interior::iterator it = mInt.find(pathgrid.mCell);
+                if (it != mInt.end())
+                {
+                    mInt.erase(it);
+
+                    Log(Debug::Warning) << "Warning: Empty pathgrid overwriting cell '"
+                        << pathgrid.mCell << "' : " << contentfile;
+                }
+            }
+            else
+            {
+                Exterior::iterator it = mExt.find(std::make_pair(pathgrid.mData.mX, pathgrid.mData.mY));
+                if (it != mExt.end())
+                {
+                    mExt.erase(it);
+                    Log(Debug::Warning) << "Warning: Empty pathgrid overwriting cell ("
+                        << pathgrid.mData.mX << ", " << pathgrid.mData.mY << ") : " << contentfile;
+                }
+            }
+
+            return RecordId("", isDeleted);
+        }
+
         // Try to overwrite existing record
         if (interior)
         {