Respect transform contexts when tracing

Author: nyalldawson

doc/api_break.dox

@@ -2133,6 +2133,12 @@ loadDefaultStyle argument.
 signals now accept a QgsRasterBlockFeedback argument for reporting progress updates.
 
 
+QgsRasterLayerSaveAsDialog        {#qgis_api_break_3_0_QgsRasterLayerSaveAsDialog}
+--------------------------
+
+- The currentExtent and currentCrs arguments have been dropped from the constructor. Use setMapCanvas() instead.
+
+
 QgsRasterProjector        {#qgis_api_break_3_0_QgsRasterProjector}
 ------------------
 
@@ -2524,6 +2530,8 @@ QgsTracer        {#qgis_api_break_3_0_QgsTracer}
 ---------
 
 - hasCrsTransformEnabled() and setCrsTransformEnabled() were removed. CRS transformation is now always enabled when required.
+- setDestinationCrs() now requires a QgsCoordinateTransformContext argument.
+
 
 QgsTransaction        {#qgis_api_break_3_0_QgsTransaction}
 --------------

python/core/qgstracer.sip

@@ -43,11 +43,16 @@ Set layers used for tracing
 
     QgsCoordinateReferenceSystem destinationCrs() const;
 %Docstring
-Get CRS used for tracing
+Returns the CRS used for tracing.
+
+.. seealso:: :py:func:`setDestinationCrs()`
 %End
-    void setDestinationCrs( const QgsCoordinateReferenceSystem &crs );
+
+    void setDestinationCrs( const QgsCoordinateReferenceSystem &crs, const QgsCoordinateTransformContext &context );
 %Docstring
-Set CRS used for tracing
+Sets the ``crs`` and transform ``context`` used for tracing.
+
+.. seealso:: :py:func:`destinationCrs()`
 %End
 
     QgsRectangle extent() const;

python/gui/qgsmapcanvas.sip

@@ -898,6 +898,13 @@ Emitted when zoom next status changed
 Emitted when map CRS has changed
 
 .. versionadded:: 2.4
+%End
+
+    void transformContextChanged();
+%Docstring
+Emitted when the canvas transform context is changed.
+
+.. versionadded:: 3.0
 %End
 
     void currentLayerChanged( QgsMapLayer *layer );

src/core/qgstracer.cpp

@@ -473,37 +473,20 @@ bool QgsTracer::initGraph()
 
   t1.start();
   int featuresCounted = 0;
-  Q_FOREACH ( QgsVectorLayer *vl, mLayers )
+  for ( QgsVectorLayer *vl : qgis::as_const( mLayers ) )
   {
-    Q_NOWARN_DEPRECATED_PUSH
-    QgsCoordinateTransform ct( vl->crs(), mCRS );
-    Q_NOWARN_DEPRECATED_POP
-
     QgsFeatureRequest request;
     request.setSubsetOfAttributes( QgsAttributeList() );
+    request.setDestinationCrs( mCRS, mTransformContext );
     if ( !mExtent.isEmpty() )
-      request.setFilterRect( ct.transformBoundingBox( mExtent, QgsCoordinateTransform::ReverseTransform ) );
+      request.setFilterRect( mExtent );
 
     QgsFeatureIterator fi = vl->getFeatures( request );
     while ( fi.nextFeature( f ) )
     {
       if ( !f.hasGeometry() )
         continue;
 
-      if ( !ct.isShortCircuited() )
-      {
-        try
-        {
-          QgsGeometry transformedGeom = f.geometry();
-          transformedGeom.transform( ct );
-          f.setGeometry( transformedGeom );
-        }
-        catch ( QgsCsException & )
-        {
-          continue; // ignore if the transform failed
-        }
-      }
-
       extractLinework( f.geometry(), mpl );
 
       ++featuresCounted;
@@ -596,12 +579,10 @@ void QgsTracer::setLayers( const QList<QgsVectorLayer *> &layers )
   invalidateGraph();
 }
 
-void QgsTracer::setDestinationCrs( const QgsCoordinateReferenceSystem &crs )
+void QgsTracer::setDestinationCrs( const QgsCoordinateReferenceSystem &crs, const QgsCoordinateTransformContext &context )
 {
-  if ( mCRS == crs )
-    return;
-
   mCRS = crs;
+  mTransformContext = context;
   invalidateGraph();
 }
 

src/core/qgstracer.h

@@ -53,10 +53,17 @@ class CORE_EXPORT QgsTracer : public QObject
     //! Set layers used for tracing
     void setLayers( const QList<QgsVectorLayer *> &layers );
 
-    //! Get CRS used for tracing
+    /**
+     * Returns the CRS used for tracing.
+     * \see setDestinationCrs()
+     */
     QgsCoordinateReferenceSystem destinationCrs() const { return mCRS; }
-    //! Set CRS used for tracing
-    void setDestinationCrs( const QgsCoordinateReferenceSystem &crs );
+
+    /**
+     * Sets the \a crs and transform \a context used for tracing.
+     * \see destinationCrs()
+     */
+    void setDestinationCrs( const QgsCoordinateReferenceSystem &crs, const QgsCoordinateTransformContext &context );
 
     //! Get extent to which graph's features will be limited (empty extent means no limit)
     QgsRectangle extent() const { return mExtent; }
@@ -161,6 +168,8 @@ class CORE_EXPORT QgsTracer : public QObject
     QList<QgsVectorLayer *> mLayers;
     //! Destination CRS in which graph is built and tracing done
     QgsCoordinateReferenceSystem mCRS;
+    //! Coordinate transform context
+    QgsCoordinateTransformContext mTransformContext;
     //! Extent for graph building (empty extent means no limit)
     QgsRectangle mExtent;
 

src/gui/qgsmapcanvas.cpp

@@ -144,6 +144,7 @@ QgsMapCanvas::QgsMapCanvas( QWidget *parent )
            this, [ = ]
   {
     mSettings.setTransformContext( QgsProject::instance()->transformContext() );
+    emit transformContextChanged();
     refresh();
   } );
 

src/gui/qgsmapcanvas.h

@@ -801,6 +801,12 @@ class GUI_EXPORT QgsMapCanvas : public QGraphicsView
      */
     void destinationCrsChanged();
 
+    /**
+     * Emitted when the canvas transform context is changed.
+     * \since QGIS 3.0
+     */
+    void transformContextChanged();
+
     /**
      * Emitted when the current layer is changed
      * \since QGIS 2.8

src/gui/qgsmapcanvastracer.cpp

@@ -39,6 +39,7 @@ QgsMapCanvasTracer::QgsMapCanvasTracer( QgsMapCanvas *canvas, QgsMessageBar *mes
 
   // when things change we just invalidate the graph - and set up new parameters again only when necessary
   connect( canvas, &QgsMapCanvas::destinationCrsChanged, this, &QgsMapCanvasTracer::invalidateGraph );
+  connect( canvas, &QgsMapCanvas::transformContextChanged, this, &QgsMapCanvasTracer::invalidateGraph );
   connect( canvas, &QgsMapCanvas::layersChanged, this, &QgsMapCanvasTracer::invalidateGraph );
   connect( canvas, &QgsMapCanvas::extentsChanged, this, &QgsMapCanvasTracer::invalidateGraph );
   connect( canvas, &QgsMapCanvas::currentLayerChanged, this, &QgsMapCanvasTracer::onCurrentLayerChanged );
@@ -96,7 +97,7 @@ void QgsMapCanvasTracer::reportError( QgsTracer::PathError err, bool addingVerte
 
 void QgsMapCanvasTracer::configure()
 {
-  setDestinationCrs( mCanvas->mapSettings().destinationCrs() );
+  setDestinationCrs( mCanvas->mapSettings().destinationCrs(), mCanvas->mapSettings().transformContext() );
   setExtent( mCanvas->extent() );
 
   QList<QgsVectorLayer *> layers;

tests/src/core/testqgstracer.cpp

@@ -313,7 +313,8 @@ void TestQgsTracer::testReprojection()
 
   QgsTracer tracer;
   tracer.setLayers( QList<QgsVectorLayer *>() << vl );
-  tracer.setDestinationCrs( dstCrs );
+  QgsCoordinateTransformContext context;
+  tracer.setDestinationCrs( dstCrs, context );
   tracer.init();
 
   QgsPolylineXY points1 = tracer.findShortestPath( p1, p2 );