From 2975e065bddab5fcf677c344f82c221cb2462101 Mon Sep 17 00:00:00 2001
From: Even Rouault <even.rouault@spatialys.com>
Date: Wed, 6 Mar 2024 17:49:52 +0100
Subject: [PATCH] OGRGeoJSONWriteLayer::ICreateFeature(): simplify using
 OGRGeometry::roundCoordinates() and SetPrecision()

---
 .../geojson/ogrgeojsonwritelayer.cpp          | 55 +++++--------------
 1 file changed, 13 insertions(+), 42 deletions(-)

diff --git a/ogr/ogrsf_frmts/geojson/ogrgeojsonwritelayer.cpp b/ogr/ogrsf_frmts/geojson/ogrgeojsonwritelayer.cpp
index 34ce6ef631ec..f866bcd40167 100644
--- a/ogr/ogrsf_frmts/geojson/ogrgeojsonwritelayer.cpp
+++ b/ogr/ogrsf_frmts/geojson/ogrgeojsonwritelayer.cpp
@@ -243,42 +243,32 @@ OGRErr OGRGeoJSONWriteLayer::ICreateFeature(OGRFeature *poFeature)
 
     // Special processing to detect and repair invalid geometries due to
     // coordinate precision.
+    // Normally drivers shouldn't do that as similar code is triggered by
+    // setting the OGR_APPLY_GEOM_SET_PRECISION=YES configuration option by
+    // the generic OGRLayer::CreateFeature() code path. But this code predates
+    // its introduction and RFC99, and can be useful in RFC7946 mode due to
+    // coordinate reprojection.
     OGRGeometry *poOrigGeom = poFeature->GetGeometryRef();
     if (OGRGeometryFactory::haveGEOS() &&
         oWriteOptions_.nXYCoordPrecision >= 0 && poOrigGeom &&
         wkbFlatten(poOrigGeom->getGeometryType()) != wkbPoint &&
         IsValid(poOrigGeom))
     {
-        struct CoordinateRoundingVisitor : public OGRDefaultGeometryVisitor
-        {
-            const double dfFactor_;
-            const double dfInvFactor_;
-
-            explicit CoordinateRoundingVisitor(int nCoordPrecision)
-                : dfFactor_(std::pow(10.0, double(nCoordPrecision))),
-                  dfInvFactor_(std::pow(10.0, double(-nCoordPrecision)))
-            {
-            }
-
-            using OGRDefaultGeometryVisitor::visit;
-            void visit(OGRPoint *p) override
-            {
-                p->setX(std::round(p->getX() * dfFactor_) * dfInvFactor_);
-                p->setY(std::round(p->getY() * dfFactor_) * dfInvFactor_);
-            }
-        };
-
-        CoordinateRoundingVisitor oVisitor(oWriteOptions_.nXYCoordPrecision);
+        const double dfXYResolution =
+            std::pow(10.0, double(-oWriteOptions_.nXYCoordPrecision));
         auto poNewGeom = poFeature == poFeatureToWrite
                              ? poOrigGeom->clone()
                              : poFeatureToWrite->GetGeometryRef();
         bool bDeleteNewGeom = (poFeature == poFeatureToWrite);
-        poNewGeom->accept(&oVisitor);
+        OGRGeomCoordinatePrecision sPrecision;
+        sPrecision.dfXYResolution = dfXYResolution;
+        poNewGeom->roundCoordinates(sPrecision);
         if (!IsValid(poNewGeom))
         {
-            CPLDebug("GeoJSON", "Running MakeValid() to correct an invalid "
+            CPLDebug("GeoJSON", "Running SetPrecision() to correct an invalid "
                                 "geometry due to reduced precision output");
-            auto poValidGeom = poNewGeom->MakeValid();
+            auto poValidGeom =
+                poOrigGeom->SetPrecision(dfXYResolution, /* nFlags = */ 0);
             if (poValidGeom)
             {
                 if (poFeature == poFeatureToWrite)
@@ -288,25 +278,6 @@ OGRErr OGRGeoJSONWriteLayer::ICreateFeature(OGRFeature *poFeature)
                     poFeatureToWrite->SetFID(poFeature->GetFID());
                 }
 
-                // It may happen that after MakeValid(), and rounding again,
-                // we end up with an invalid result. Run MakeValid() again...
-                poValidGeom->accept(&oVisitor);
-                if (!IsValid(poValidGeom))
-                {
-                    auto poValidGeom2 = poValidGeom->MakeValid();
-                    if (poValidGeom2)
-                    {
-                        delete poValidGeom;
-                        poValidGeom = poValidGeom2;
-                        if (!IsValid(poValidGeom))
-                        {
-                            // hopefully should not happen
-                            CPLDebug("GeoJSON",
-                                     "... still not valid! Giving up");
-                        }
-                    }
-                }
-
                 poFeatureToWrite->SetGeometryDirectly(poValidGeom);
             }
         }