Avoid all use of QgsCoordinateTransform pointers, replace with

copies or references

Makes the code more robust, fixes leaks and avoids potential
null pointer dereferencing

doc/api_break.dox

@@ -37,6 +37,30 @@ plugins calling these methods will need to be updated.</li>
 <li>readXML() and writeXML() have been renamed to readXml() and writeXml() for consistency</li>
 </ul>
 
+\subsection qgis_api_break_3_0_QgsCoordinateTransformCache QgsCoordinateTransformCache
+
+<ul>
+<li>transform() now returns a QgsCoordinateTransform object, not a pointer. An invalid QgsCoordinateTransform will
+be returned in place of a null pointer.</li>
+</ul>
+
+\subsection qgis_api_break_3_0_QgsDiagramLayerSettings QgsDiagramLayerSettings
+
+<ul>
+<li>coordinateTransform() now returns a QgsCoordinateTransform object, not a pointer. An invalid QgsCoordinateTransform will
+be returned in place of a null pointer.</li>
+<li>setCoordinateTransform() now takes a QgsCoordinateTransform object, not a pointer. Use an invalid QgsCoordinateTransform in
+place of a null pointer.</li>
+<li>The ct member has been removed. Use coordinateTransform() and setCoordinateTransform() instead.
+</ul>
+
+\subsection qgis_api_break_3_0_QgsDatumTransformStore QgsDatumTransformStore
+
+<ul>
+<li>transformation() now returns a QgsCoordinateTransform object, not a pointer. An invalid QgsCoordinateTransform will
+be returned in place of a null pointer.</li>
+</ul>
+
 \subsection qgis_api_break_3_0_DataProviders Data Providers
 
 <ul>
@@ -79,6 +103,43 @@ screenUpdateRequested() were removed. These members have had no effect for a num
 <li>theError parameter in appendError() and setError() were renamed to 'error'.</li>
 </ul>
 
+\subsection qgis_api_break_3_0_QgsMapRenderer QgsMapRenderer
+
+<ul>
+<li>transformation() now returns a QgsCoordinateTransform object, not a pointer. An invalid QgsCoordinateTransform will
+be returned instead of a null pointer if no transformation is required.</li>
+</ul>
+
+\subsection qgis_api_break_3_0_QgsMapRendererJob QgsMapRendererJob
+
+<ul>
+<li>reprojectToLayerExtent() now takes a QgsCoordinateTransform reference, not a pointer. An invalid QgsCoordinateTransform should
+be used instead of a null pointer if no transformation is required.</li>
+</ul>
+
+\subsection qgis_api_break_3_0_QgsMapSettings QgsMapSettings
+
+<ul>
+<li>layerTransform() now returns a QgsCoordinateTransform object, not a pointer. An invalid QgsCoordinateTransform will
+be returned instead of a null pointer if no transformation is required.</li>
+</ul>
+
+\subsection qgis_api_break_3_0_QgsRenderContext QgsRenderContext
+
+<ul>
+<li>coordinateTransform() now returns a QgsCoordinateTransform object, not a pointer. An invalid QgsCoordinateTransform will
+be returned instead of a null pointer if no transformation is required.</li>
+<li>setCoordinateTransform() now takes a QgsCoordinateTransform reference, not a pointer. An invalid QgsCoordinateTransform should be used instead of a null pointer if no transformation is required.</li>
+</ul>
+
+\subsection qgis_api_break_3_0_QgsPalLayerSettings QgsPalLayerSettings
+
+<ul>
+<li>ct is now a QgsCoordinateTransform object, not a pointer. An invalid QgsCoordinateTransform will
+be used instead of a null pointer if no transformation is required.</li>
+<li>prepareGeometry() and geometryRequiresPreparation() now take a QgsCoordinateTransform reference, not a pointer. An invalid QgsCoordinateTransform should be used instead of a null pointer if no transformation is required.</li>
+</ul>
+
 \subsection qgis_api_break_3_0_QgsJSONExporter QgsJSONExporter
 
 <ul>
@@ -125,13 +186,20 @@ plugins calling this method will need to be updated.</li>
 <li>subsetString() was made const. This has no effect on PyQGIS code, but c++ code implementing derived layer classes will need to update the signature of this method to match.</li>
 </ul>
 
+\subsection qgis_api_break_3_0_QgsRasterProjector QgsRasterProjector
+
+<ul>
+<li>extentSize() now takes a QgsCoordinateTransform reference, not a pointer. An invalid QgsCoordinateTransform should be used instead of a null pointer if no transformation is required.</li>
+</ul>
+
 \subsection qgis_api_break_3_0_QgsVectorFileWriter QgsVectorFileWriter
 
 <ul>
 <li>QgsVectorFileWriter now takes references instead of pointers to QgsCoordinateReferenceSystem objects. Since
 QgsCoordinateReferenceSystem is now implicitly shared, using references to QgsCoordinateReferenceSystem rather than
 pointers makes for more robust, safer code. Use an invalid (default constructed) QgsCoordinateReferenceSystem
 in code which previously passed a null pointer to QgsVectorFileWriter.</li>
+<li>writeAsVectorFormat() now takes a QgsCoordinateTransform reference, not a pointer. An invalid QgsCoordinateTransform should be used instead of a null pointer if no transformation is required.</li>
 </ul>
 
 \subsection qgis_api_break_3_0_QgsVectorLayerEditBuffer QgsVectorLayerEditBuffer

python/core/qgscrscache.sip

@@ -7,13 +7,16 @@ class QgsCoordinateTransformCache
     static QgsCoordinateTransformCache* instance();
 
     ~QgsCoordinateTransformCache();
+
     /** Returns coordinate transformation. Cache keeps ownership
         @param srcAuthId auth id string of source crs
         @param destAuthId auth id string of dest crs
         @param srcDatumTransform id of source's datum transform
         @param destDatumTransform id of destinations's datum transform
+        @returns matching transform, or an invalid transform if none could be created
      */
-    const QgsCoordinateTransform* transform( const QString& srcAuthId, const QString& destAuthId, int srcDatumTransform = -1, int destDatumTransform = -1 );
+    QgsCoordinateTransform transform( const QString& srcAuthId, const QString& destAuthId, int srcDatumTransform = -1, int destDatumTransform = -1 );
+
     /** Removes transformations where a changed crs is involved from the cache*/
     void invalidateCrs( const QString& crsAuthId );
 

python/core/qgsdatumtransformstore.sip

@@ -23,9 +23,11 @@ class QgsDatumTransformStore
 
     /** Will return transform from layer's CRS to current destination CRS.
      *  Will emit datumTransformInfoRequested signal if the layer has no entry.
-     *  Returns an instance from QgsCoordinateTransformCache
+     *  @returns transformation associated with layer, or an invalid QgsCoordinateTransform
+     *  if no transform is associated with the layer
      */
-    const QgsCoordinateTransform* transformation( QgsMapLayer* layer ) const;
+    QgsCoordinateTransform transformation( QgsMapLayer* layer ) const;
+
 
     void readXML( const QDomNode& parentNode );
 

python/core/qgsdiagramrendererv2.sip

@@ -181,28 +181,19 @@ class QgsDiagramLayerSettings
     // TODO QGIS 3.0 - make private, rename to mRenderer
     QgsDiagramRendererV2* renderer;
 
-    /** Returns the coordinate transform associated with the layer.
+    /** Returns the coordinate transform associated with the layer, or an
+     * invalid transform if no transformation is required.
      * @see setCoordinateTransform()
      * @note added in QGIS 2.16
      */
-    QgsCoordinateTransform* coordinateTransform();
-
-    /** Returns the coordinate transform associated with the layer.
-     * @see setCoordinateTransform()
-     * @note added in QGIS 2.16
-     */
-    //const QgsCoordinateTransform* coordinateTransform() const;
+    QgsCoordinateTransform coordinateTransform() const;
 
     /** Sets the coordinate transform associated with the layer.
      * @param transform coordinate transform. Ownership is transferred to the object.
      * @see coordinateTransform()
      * @note added in QGIS 2.16
      */
-    void setCoordinateTransform( QgsCoordinateTransform* transform /Transfer/ );
-
-    //! Associated coordinate transform. Owned by this object.
-    // TODO QGIS 3.0 - make private, rename to mCt
-    QgsCoordinateTransform* ct;
+    void setCoordinateTransform( const QgsCoordinateTransform& transform );
 
     //! @deprecated will be removed in QGIS 3.0
     const QgsMapToPixel* xform;

python/core/qgsmaprenderer.sip

@@ -305,7 +305,10 @@ class QgsMapRenderer : QObject
     void addLayerCoordinateTransform( const QString& layerId, const QString& srcAuthId, const QString& destAuthId, int srcDatumTransform = -1, int destDatumTransform = -1 );
     void clearLayerCoordinateTransforms();
 
-    const QgsCoordinateTransform* transformation( const QgsMapLayer *layer ) const;
+    /** Returns the coordinate transform associated with a renderered layer,
+     * or an invalid transform is no transform is required for the layer.
+     */
+    QgsCoordinateTransform transformation( const QgsMapLayer *layer ) const;
 
     //! bridge to QgsMapSettings
     //! @note added in 2.4

python/core/qgsmaprendererjob.sip

@@ -110,7 +110,7 @@ class QgsMapRendererJob : QObject
      * source CRS coordinates, and if it was split, returns true, and
      * also sets the contents of the r2 parameter
      */
-    static bool reprojectToLayerExtent( const QgsMapLayer *ml, const QgsCoordinateTransform *ct, QgsRectangle &extent, QgsRectangle &r2 );
+    static bool reprojectToLayerExtent( const QgsMapLayer *ml, const QgsCoordinateTransform& ct, QgsRectangle &extent, QgsRectangle &r2 );
 
     //! @note not available in python bindings
     // LayerRenderJobs prepareJobs( QPainter* painter, QgsPalLabeling* labelingEngine );

python/core/qgsmapsettings.sip

@@ -218,9 +218,9 @@ class QgsMapSettings
     /**
      * @brief Return coordinate transform from layer's CRS to destination CRS
      * @param layer
-     * @return transform - may be null if the transform is not needed
+     * @return transform - may be invalid if the transform is not needed
      */
-    const QgsCoordinateTransform* layerTransform( QgsMapLayer *layer ) const;
+    QgsCoordinateTransform layerTransform( QgsMapLayer *layer ) const;
 
     //! returns current extent of layer set
     QgsRectangle fullExtent() const;

python/core/qgspallabeling.sip

@@ -662,7 +662,7 @@ class QgsPalLayerSettings
     QgsFields mCurFields;
     int fieldIndex;
     const QgsMapToPixel* xform;
-    const QgsCoordinateTransform* ct;
+    QgsCoordinateTransform ct;
 
     QgsPoint ptZero;
     QgsPoint ptOne;
@@ -916,22 +916,22 @@ class QgsPalLabeling : QgsLabelingEngineInterface
     /** Prepares a geometry for registration with PAL. Handles reprojection, rotation, clipping, etc.
      * @param geometry geometry to prepare
      * @param context render context
-     * @param ct coordinate transform
+     * @param ct coordinate transform, or invalid transform if no transformation required
      * @param clipGeometry geometry to clip features to, if applicable
      * @returns prepared geometry, the caller takes ownership
      * @note added in QGIS 2.9
      */
-    static QgsGeometry* prepareGeometry( const QgsGeometry *geometry, QgsRenderContext &context, const QgsCoordinateTransform *ct, QgsGeometry *clipGeometry = 0 ) /Factory/;
+    static QgsGeometry* prepareGeometry( const QgsGeometry *geometry, QgsRenderContext &context, const QgsCoordinateTransform& ct, QgsGeometry *clipGeometry = 0 ) /Factory/;
 
     /** Checks whether a geometry requires preparation before registration with PAL
      * @param geometry geometry to prepare
      * @param context render context
-     * @param ct coordinate transform
+     * @param @param ct coordinate transform, or invalid transform if no transformation required
      * @param clipGeometry geometry to clip features to, if applicable
      * @returns true if geometry requires preparation
      * @note added in QGIS 2.9
      */
-    static bool geometryRequiresPreparation( const QgsGeometry *geometry, QgsRenderContext &context, const QgsCoordinateTransform *ct, QgsGeometry *clipGeometry = 0 );
+    static bool geometryRequiresPreparation( const QgsGeometry *geometry, QgsRenderContext &context, const QgsCoordinateTransform& ct, QgsGeometry *clipGeometry = 0 );
 
     /** Splits a text string to a list of separate lines, using a specified wrap character.
      * The text string will be split on either newline characters or the wrap character.

python/core/qgsrendercontext.sip

@@ -55,7 +55,10 @@ class QgsRenderContext
     QPainter* painter();
     const QPainter* constPainter() const;
 
-    const QgsCoordinateTransform* coordinateTransform() const;
+    /** Returns the current coordinate transform for the context, or an invalid
+     * transform is no coordinate transformation is required.
+     */
+    QgsCoordinateTransform coordinateTransform() const;
 
     const QgsRectangle& extent() const;
 
@@ -99,8 +102,9 @@ class QgsRenderContext
 
     //setters
 
-    /** Sets coordinate transformation. QgsRenderContext does not take ownership*/
-    void setCoordinateTransform( const QgsCoordinateTransform* t );
+    /** Sets coordinate transformation.*/
+    void setCoordinateTransform( const QgsCoordinateTransform& t );
+
     void setMapToPixel( const QgsMapToPixel& mtp );
     void setExtent( const QgsRectangle& extent );
 

python/core/qgsvectorfilewriter.sip

@@ -179,7 +179,8 @@ class QgsVectorFileWriter
      * @param layer layer to write
      * @param fileName file name to write to
      * @param fileEncoding encoding to use
-     * @param ct pointer to coordinate transform to reproject exported geometries with
+     * @param ct coordinate transform to reproject exported geometries with, or invalid transform
+     * for no transformation
      * @param driverName OGR driver to use
      * @param onlySelected write only selected features of layer
      * @param errorMessage pointer to buffer fo error message
@@ -201,7 +202,7 @@ class QgsVectorFileWriter
     static WriterError writeAsVectorFormat( QgsVectorLayer* layer,
                                             const QString& fileName,
                                             const QString& fileEncoding,
-                                            const QgsCoordinateTransform* ct,
+                                            const QgsCoordinateTransform& ct,
                                             const QString& driverName = "ESRI Shapefile",
                                             bool onlySelected = false,
                                             QString *errorMessage = 0,

python/core/raster/qgsrasterprojector.sip

@@ -81,7 +81,7 @@ class QgsRasterProjector : QgsRasterInterface
                          QgsRectangle& theDestExtent, int& theDestXSize, int& theDestYSize );
 
     /** Calculate destination extent and size from source extent and size */
-    static bool extentSize( const QgsCoordinateTransform* ct,
+    static bool extentSize( const QgsCoordinateTransform& ct,
                             const QgsRectangle& theSrcExtent, int theSrcXSize, int theSrcYSize,
                             QgsRectangle& theDestExtent, int& theDestXSize, int& theDestYSize );
 };

src/app/nodetool/qgsmaptoolnodetool.cpp

@@ -97,8 +97,8 @@ void QgsMapToolNodeTool::createTopologyRubberBands()
         rb->setBrushStyle( Qt::NoBrush );
         rb->setOutlineWidth( settings.value( "/qgis/digitizing/line_width", 1 ).toInt() );
         QgsAbstractGeometryV2* rbGeom = feature.constGeometry()->geometry()->clone();
-        if ( mCanvas->mapSettings().layerTransform( vlayer ) )
-          rbGeom->transform( *mCanvas->mapSettings().layerTransform( vlayer ) );
+        if ( mCanvas->mapSettings().layerTransform( vlayer ).isValid() )
+          rbGeom->transform( mCanvas->mapSettings().layerTransform( vlayer ) );
         rb->setGeometry( rbGeom );
         mMoveRubberBands.insert( snapFeatureId, rb );
       }
@@ -140,8 +140,8 @@ void QgsMapToolNodeTool::canvasMoveEvent( QgsMapMouseEvent* e )
       rb->setBrushStyle( Qt::NoBrush );
       rb->setOutlineWidth( settings.value( "/qgis/digitizing/line_width", 1 ).toInt() );
       QgsAbstractGeometryV2* rbGeom = mSelectedFeature->geometry()->geometry()->clone();
-      if ( mCanvas->mapSettings().layerTransform( vlayer ) )
-        rbGeom->transform( *mCanvas->mapSettings().layerTransform( vlayer ) );
+      if ( mCanvas->mapSettings().layerTransform( vlayer ).isValid() )
+        rbGeom->transform( mCanvas->mapSettings().layerTransform( vlayer ) );
       rb->setGeometry( rbGeom );
       mMoveRubberBands.insert( mSelectedFeature->featureId(), rb );
       Q_FOREACH ( const QgsVertexEntry* vertexEntry, mSelectedFeature->vertexMap() )
@@ -402,8 +402,8 @@ void QgsMapToolNodeTool::updateSelectFeature( QgsGeometry &geom )
 
     QgsAbstractGeometryV2* rbGeom = geom.geometry()->clone();
     QgsVectorLayer *vlayer = mSelectedFeature->vlayer();
-    if ( mCanvas->mapSettings().layerTransform( vlayer ) )
-      rbGeom->transform( *mCanvas->mapSettings().layerTransform( vlayer ) );
+    if ( mCanvas->mapSettings().layerTransform( vlayer ).isValid() )
+      rbGeom->transform( mCanvas->mapSettings().layerTransform( vlayer ) );
     mSelectRubberBand->setGeometry( rbGeom );
   }
   else

src/app/qgisapp.cpp

@@ -6177,12 +6177,12 @@ void QgisApp::saveAsVectorFileGeneral( QgsVectorLayer* vlayer, bool symbologyOpt
     bool autoGeometryType = dialog->automaticGeometryType();
     QgsWKBTypes::Type forcedGeometryType = dialog->geometryType();
 
-    QgsCoordinateTransform* ct = nullptr;
+    QgsCoordinateTransform ct;
     destCRS = QgsCRSCache::instance()->crsBySrsId( dialog->crs() );
 
     if ( destCRS.isValid() && destCRS != vlayer->crs() )
     {
-      ct = new QgsCoordinateTransform( vlayer->crs(), destCRS );
+      ct = QgsCoordinateTransform( vlayer->crs(), destCRS );
 
       //ask user about datum transformation
       QSettings settings;
@@ -6195,13 +6195,13 @@ void QgisApp::saveAsVectorFileGeneral( QgsVectorLayer* vlayer, bool symbologyOpt
           QList< int > sdt = d.selectedDatumTransform();
           if ( !sdt.isEmpty() )
           {
-            ct->setSourceDatumTransform( sdt.at( 0 ) );
+            ct.setSourceDatumTransform( sdt.at( 0 ) );
           }
           if ( sdt.size() > 1 )
           {
-            ct->setDestinationDatumTransform( sdt.at( 1 ) );
+            ct.setDestinationDatumTransform( sdt.at( 1 ) );
           }
-          ct->initialise();
+          ct.initialise();
         }
       }
     }
@@ -6235,8 +6235,6 @@ void QgisApp::saveAsVectorFileGeneral( QgsVectorLayer* vlayer, bool symbologyOpt
               converterPtr
             );
 
-    delete ct;
-
     QApplication::restoreOverrideCursor();
 
     if ( error == QgsVectorFileWriter::NoError )

src/core/composer/qgsatlascomposition.cpp

@@ -925,7 +925,7 @@ QgsGeometry QgsAtlasComposition::currentGeometry( const QgsCoordinateReferenceSy
   }
 
   QgsGeometry transformed = *mCurrentFeature.constGeometry();
-  transformed.transform( *QgsCoordinateTransformCache::instance()->transform( mCoverageLayer->crs().authid(), crs.authid() ) );
+  transformed.transform( QgsCoordinateTransformCache::instance()->transform( mCoverageLayer->crs().authid(), crs.authid() ) );
   mGeometryCache[crs.srsid()] = transformed;
   return transformed;
 }