Respect transform context in point locator

doc/api_break.dox

@@ -2002,7 +2002,8 @@ QgsPointLocator        {#qgis_api_break_3_0_QgsPointLocator}
 ---------------
 
 - The constructor now takes a reference rather than a pointer to a CRS.  This has no effect on PyQGIS code, but c++
-plugins calling this method will need to be updated.
+plugins calling this method will need to be updated. The constructor now requires a QgsCoordinateTransformContext argument
+when a destination crs is specified.
 - The destCRS parameter in the constructor has been renamed to destinationCrs.
 - destCRS() has been renamed to destinationCrs()
 - destinationCrs() now returns a copy instead of a reference to the CRS. This has no effect on PyQGIS code, but c++

python/core/qgspointlocator.sip

@@ -30,12 +30,15 @@ Works with one layer.
   public:
 
     explicit QgsPointLocator( QgsVectorLayer *layer, const QgsCoordinateReferenceSystem &destinationCrs = QgsCoordinateReferenceSystem(),
+                              const QgsCoordinateTransformContext &transformContext = QgsCoordinateTransformContext(),
                               const QgsRectangle *extent = 0 );
 %Docstring
 Construct point locator for a ``layer``.
 
 If a valid QgsCoordinateReferenceSystem is passed for ``destinationCrs`` then the locator will
-do the searches on data reprojected to the given CRS.
+do the searches on data reprojected to the given CRS. For accurate reprojection it is important
+to set the correct ``transformContext`` if a ``destinationCrs`` is specified. This is usually taken
+from the current :py:func:`QgsProject.transformContext()`
 
 If ``extent`` is not null, the locator will index only a subset of the layer which falls within that extent.
 %End

python/core/qgssnappingutils.sip

@@ -181,6 +181,11 @@ Called when starting to index - can be overridden and e.g. progress dialog can b
     virtual void prepareIndexProgress( int index );
 %Docstring
 Called when finished indexing a layer. When index == count the indexing is complete
+%End
+
+    void clearAllLocators();
+%Docstring
+Deletes all existing locators (e.g. when destination CRS has changed and we need to reindex)
 %End
 
 };

src/core/qgspointlocator.cpp

@@ -620,15 +620,13 @@ class QgsPointLocator_DumpTree : public SpatialIndex::IQueryStrategy
 ////////////////////////////////////////////////////////////////////////////
 
 
-QgsPointLocator::QgsPointLocator( QgsVectorLayer *layer, const QgsCoordinateReferenceSystem &destCRS, const QgsRectangle *extent )
+QgsPointLocator::QgsPointLocator( QgsVectorLayer *layer, const QgsCoordinateReferenceSystem &destCRS, const QgsCoordinateTransformContext &transformContext, const QgsRectangle *extent )
   : mIsEmptyLayer( false )
   , mLayer( layer )
 {
   if ( destCRS.isValid() )
   {
-    Q_NOWARN_DEPRECATED_PUSH
-    mTransform = QgsCoordinateTransform( layer->crs(), destCRS );
-    Q_NOWARN_DEPRECATED_POP
+    mTransform = QgsCoordinateTransform( layer->crs(), destCRS, transformContext );
   }
 
   setExtent( extent );

src/core/qgspointlocator.h

@@ -55,12 +55,15 @@ class CORE_EXPORT QgsPointLocator : public QObject
     /**
      * Construct point locator for a \a layer.
      *
-     *  If a valid QgsCoordinateReferenceSystem is passed for \a destinationCrs then the locator will
-     *  do the searches on data reprojected to the given CRS.
+     * If a valid QgsCoordinateReferenceSystem is passed for \a destinationCrs then the locator will
+     * do the searches on data reprojected to the given CRS. For accurate reprojection it is important
+     * to set the correct \a transformContext if a \a destinationCrs is specified. This is usually taken
+     * from the current QgsProject::transformContext().
      *
-     *  If \a extent is not null, the locator will index only a subset of the layer which falls within that extent.
+     * If \a extent is not null, the locator will index only a subset of the layer which falls within that extent.
      */
     explicit QgsPointLocator( QgsVectorLayer *layer, const QgsCoordinateReferenceSystem &destinationCrs = QgsCoordinateReferenceSystem(),
+                              const QgsCoordinateTransformContext &transformContext = QgsCoordinateTransformContext(),
                               const QgsRectangle *extent = nullptr );
 
     ~QgsPointLocator() override;

src/core/qgssnappingutils.cpp

@@ -39,7 +39,7 @@ QgsPointLocator *QgsSnappingUtils::locatorForLayer( QgsVectorLayer *vl )
 
   if ( !mLocators.contains( vl ) )
   {
-    QgsPointLocator *vlpl = new QgsPointLocator( vl, destinationCrs() );
+    QgsPointLocator *vlpl = new QgsPointLocator( vl, destinationCrs(), mMapSettings.transformContext() );
     mLocators.insert( vl, vlpl );
   }
   return mLocators.value( vl );
@@ -72,7 +72,7 @@ QgsPointLocator *QgsSnappingUtils::temporaryLocatorForLayer( QgsVectorLayer *vl,
 
   QgsRectangle rect( pointMap.x() - tolerance, pointMap.y() - tolerance,
                      pointMap.x() + tolerance, pointMap.y() + tolerance );
-  QgsPointLocator *vlpl = new QgsPointLocator( vl, destinationCrs(), &rect );
+  QgsPointLocator *vlpl = new QgsPointLocator( vl, destinationCrs(), mMapSettings.transformContext(), &rect );
   mTemporaryLocators.insert( vl, vlpl );
   return mTemporaryLocators.value( vl );
 }

src/core/qgssnappingutils.h

@@ -184,14 +184,14 @@ class CORE_EXPORT QgsSnappingUtils : public QObject
     //! Called when finished indexing a layer. When index == count the indexing is complete
     virtual void prepareIndexProgress( int index ) { Q_UNUSED( index ); }
 
+    //! Deletes all existing locators (e.g. when destination CRS has changed and we need to reindex)
+    void clearAllLocators();
+
   private:
     void onIndividualLayerSettingsChanged( const QHash<QgsVectorLayer *, QgsSnappingConfig::IndividualLayerSettings> &layerSettings );
     //! Get destination CRS from map settings, or an invalid CRS if projections are disabled
     QgsCoordinateReferenceSystem destinationCrs() const;
 
-    //! delete all existing locators (e.g. when destination CRS has changed and we need to reindex)
-    void clearAllLocators();
-
     //! return a locator (temporary or not) according to the indexing strategy
     QgsPointLocator *locatorForLayerUsingStrategy( QgsVectorLayer *vl, const QgsPointXY &pointMap, double tolerance );
     //! return a temporary locator with index only for a small area (will be replaced by another one on next request)

src/gui/qgsmapcanvassnappingutils.cpp

@@ -29,6 +29,7 @@ QgsMapCanvasSnappingUtils::QgsMapCanvasSnappingUtils( QgsMapCanvas *canvas, QObj
   connect( canvas, &QgsMapCanvas::destinationCrsChanged, this, &QgsMapCanvasSnappingUtils::canvasMapSettingsChanged );
   connect( canvas, &QgsMapCanvas::layersChanged, this, &QgsMapCanvasSnappingUtils::canvasMapSettingsChanged );
   connect( canvas, &QgsMapCanvas::currentLayerChanged, this, &QgsMapCanvasSnappingUtils::canvasCurrentLayerChanged );
+  connect( canvas, &QgsMapCanvas::transformContextChanged, this, &QgsMapCanvasSnappingUtils::canvasTransformContextChanged );
   canvasMapSettingsChanged();
   canvasCurrentLayerChanged();
 }
@@ -38,6 +39,13 @@ void QgsMapCanvasSnappingUtils::canvasMapSettingsChanged()
   setMapSettings( mCanvas->mapSettings() );
 }
 
+void QgsMapCanvasSnappingUtils::canvasTransformContextChanged()
+{
+  // can't trust any of our previous locators, as we don't know exactly how datum transform changes would affect these
+  clearAllLocators();
+  setMapSettings( mCanvas->mapSettings() );
+}
+
 void QgsMapCanvasSnappingUtils::canvasCurrentLayerChanged()
 {
   setCurrentLayer( qobject_cast<QgsVectorLayer *>( mCanvas->currentLayer() ) );

src/gui/qgsmapcanvassnappingutils.h

@@ -40,6 +40,7 @@ class GUI_EXPORT QgsMapCanvasSnappingUtils : public QgsSnappingUtils
 
   private slots:
     void canvasMapSettingsChanged();
+    void canvasTransformContextChanged();
     void canvasCurrentLayerChanged();
 
   private:

tests/src/core/testqgspointlocator.cpp

@@ -248,13 +248,13 @@ class TestQgsPointLocator : public QObject
     void testExtent()
     {
       QgsRectangle bbox1( 10, 10, 11, 11 ); // out of layer's bounds
-      QgsPointLocator loc1( mVL, QgsCoordinateReferenceSystem(), &bbox1 );
+      QgsPointLocator loc1( mVL, QgsCoordinateReferenceSystem(), QgsCoordinateTransformContext(), &bbox1 );
 
       QgsPointLocator::Match m1 = loc1.nearestVertex( QgsPointXY( 2, 2 ), 999 );
       QVERIFY( !m1.isValid() );
 
       QgsRectangle bbox2( 0, 0, 1, 1 ); // in layer's bounds
-      QgsPointLocator loc2( mVL, QgsCoordinateReferenceSystem(), &bbox2 );
+      QgsPointLocator loc2( mVL, QgsCoordinateReferenceSystem(), QgsCoordinateTransformContext(), &bbox2 );
 
       QgsPointLocator::Match m2 = loc2.nearestVertex( QgsPointXY( 2, 2 ), 999 );
       QVERIFY( m2.isValid() );
@@ -270,7 +270,7 @@ class TestQgsPointLocator : public QObject
       flist << ff;
       vlNullGeom->dataProvider()->addFeatures( flist );
 
-      QgsPointLocator loc( vlNullGeom, QgsCoordinateReferenceSystem(), nullptr );
+      QgsPointLocator loc( vlNullGeom, QgsCoordinateReferenceSystem(), QgsCoordinateTransformContext(), nullptr );
 
       QgsPointLocator::Match m1 = loc.nearestVertex( QgsPointXY( 2, 2 ), std::numeric_limits<double>::max() );
       QVERIFY( !m1.isValid() );
@@ -292,7 +292,7 @@ class TestQgsPointLocator : public QObject
       flist << ff;
       vlEmptyGeom->dataProvider()->addFeatures( flist );
 
-      QgsPointLocator loc( vlEmptyGeom, QgsCoordinateReferenceSystem(), nullptr );
+      QgsPointLocator loc( vlEmptyGeom, QgsCoordinateReferenceSystem(), QgsCoordinateTransformContext(), nullptr );
 
       QgsPointLocator::Match m1 = loc.nearestVertex( QgsPointXY( 2, 2 ), std::numeric_limits<double>::max() );
       QVERIFY( !m1.isValid() );