From 685a64466a3bc25a8d0bdb0b0f932ad7e977620d Mon Sep 17 00:00:00 2001
From: Even Rouault <even.rouault@spatialys.com>
Date: Mon, 25 Nov 2019 04:54:17 +0100
Subject: normalizeForVisualization() and other methods applying on a
 ProjectedCRS: do not mess the derivingConversion object of the original
 object (fixes #1736)

normalizeForVisualization(), promoteTo3D(), demoteTo2D(), alterGeodeticCRS(),
alterCSLinearUnit() and alterParametersLinearUnit() all used the object
returned by derivingConversionRef() to create a new ProjectedCRS. While doing
so, this caused the derivingConversion of the original object to have its
targetCRS set to the object returned by normalizeForVisualization() and similar.
If that object died, then the weak pointer would be reset, and the original
ProjectedCRS() has now its derivingConversionRef()->targetCRS() nullptr

So bottom line is use derivingConversion() for anything that is not pure
reading !!!

This is confirmed to be the fix for the QGIS scenario in
https://github.com/qgis/QGIS/issues/30569#issuecomment-540060919

In QGIS use case, the issue arised when using a projected CRS with a non-GIS
friendly axis (that is where normalizeForVisualization() created a new projectedCRS)
---
 src/iso19111/crs.cpp | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

(limited to 'src')

diff --git a/src/iso19111/crs.cpp b/src/iso19111/crs.cpp
index cf533bd3..eb15b0d8 100644
--- a/src/iso19111/crs.cpp
+++ b/src/iso19111/crs.cpp
@@ -237,7 +237,7 @@ CRSNNPtr CRS::alterGeodeticCRS(const GeodeticCRSNNPtr &newGeodCRS) const {
     auto projCRS = dynamic_cast<const ProjectedCRS *>(this);
     if (projCRS) {
         return ProjectedCRS::create(createPropertyMap(this), newGeodCRS,
-                                    projCRS->derivingConversionRef(),
+                                    projCRS->derivingConversion(),
                                     projCRS->coordinateSystem());
     }
 
@@ -264,7 +264,7 @@ CRSNNPtr CRS::alterCSLinearUnit(const common::UnitOfMeasure &unit) const {
         if (projCRS) {
             return ProjectedCRS::create(
                 createPropertyMap(this), projCRS->baseCRS(),
-                projCRS->derivingConversionRef(),
+                projCRS->derivingConversion(),
                 projCRS->coordinateSystem()->alterUnit(unit));
         }
     }
@@ -675,9 +675,8 @@ CRSNNPtr CRS::normalizeForVisualization() const {
                                               axisList[0])
                     : cs::CartesianCS::create(util::PropertyMap(), axisList[1],
                                               axisList[0], axisList[2]);
-            return util::nn_static_pointer_cast<CRS>(
-                ProjectedCRS::create(props, projCRS->baseCRS(),
-                                     projCRS->derivingConversionRef(), cs));
+            return util::nn_static_pointer_cast<CRS>(ProjectedCRS::create(
+                props, projCRS->baseCRS(), projCRS->derivingConversion(), cs));
         }
     }
 
@@ -844,7 +843,7 @@ CRSNNPtr CRS::promoteTo3D(const std::string &newName,
                                         !newName.empty() ? newName : nameStr()),
                 NN_NO_CHECK(
                     util::nn_dynamic_pointer_cast<GeodeticCRS>(base3DCRS)),
-                projCRS->derivingConversionRef(), cs));
+                projCRS->derivingConversion(), cs));
         }
     }
 
@@ -3379,10 +3378,10 @@ bool ProjectedCRS::_isEquivalentTo(
 ProjectedCRSNNPtr
 ProjectedCRS::alterParametersLinearUnit(const common::UnitOfMeasure &unit,
                                         bool convertToNewUnit) const {
-    return create(createPropertyMap(this), baseCRS(),
-                  derivingConversionRef()->alterParametersLinearUnit(
-                      unit, convertToNewUnit),
-                  coordinateSystem());
+    return create(
+        createPropertyMap(this), baseCRS(),
+        derivingConversion()->alterParametersLinearUnit(unit, convertToNewUnit),
+        coordinateSystem());
 }
 //! @endcond
 
@@ -3791,7 +3790,7 @@ ProjectedCRS::demoteTo2D(const std::string &newName,
         return ProjectedCRS::create(
             util::PropertyMap().set(common::IdentifiedObject::NAME_KEY,
                                     !newName.empty() ? newName : nameStr()),
-            newBaseCRS, derivingConversionRef(), cs);
+            newBaseCRS, derivingConversion(), cs);
     }
 
     return NN_NO_CHECK(std::dynamic_pointer_cast<ProjectedCRS>(
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