Fix tracing

Author: m-kuhn

src/gui/qgsmapcanvastracer.cpp

@@ -24,16 +24,13 @@
 
 #include <QAction>
 
-QHash<QgsMapCanvas*, QgsMapCanvasTracer*> QgsMapCanvasTracer::sTracers;
-
-
 QgsMapCanvasTracer::QgsMapCanvasTracer( QgsMapCanvas* canvas, QgsMessageBar* messageBar )
     : mCanvas( canvas )
     , mMessageBar( messageBar )
     , mLastMessage( nullptr )
     , mActionEnableTracing( nullptr )
 {
-  sTracers.insert( canvas, this );
+  tracers().insert( mCanvas, this );
 
   // when things change we just invalidate the graph - and set up new parameters again only when necessary
   connect( canvas, SIGNAL( destinationCrsChanged() ), this, SLOT( invalidateGraph() ) );
@@ -49,12 +46,12 @@ QgsMapCanvasTracer::QgsMapCanvasTracer( QgsMapCanvas* canvas, QgsMessageBar* mes
 
 QgsMapCanvasTracer::~QgsMapCanvasTracer()
 {
-  sTracers.remove( mCanvas );
+  tracers().remove( mCanvas );
 }
 
 QgsMapCanvasTracer* QgsMapCanvasTracer::tracerForCanvas( QgsMapCanvas* canvas )
 {
-  return sTracers.value( canvas, 0 );
+  return tracers().value( canvas );
 }
 
 void QgsMapCanvasTracer::reportError( QgsTracer::PathError err, bool addingVertex )
@@ -137,3 +134,9 @@ void QgsMapCanvasTracer::onCurrentLayerChanged()
   if ( mCanvas->snappingUtils()->snapToMapMode() == QgsSnappingUtils::SnapCurrentLayer )
     invalidateGraph();
 }
+
+QHash<QgsMapCanvas*, QgsMapCanvasTracer*> &QgsMapCanvasTracer::tracers()
+{
+  static QHash<QgsMapCanvas*, QgsMapCanvasTracer*> sTracers;
+  return sTracers;
+}

src/gui/qgsmapcanvastracer.h

@@ -67,13 +67,13 @@ class GUI_EXPORT QgsMapCanvasTracer : public QgsTracer
     void onCurrentLayerChanged();
 
   private:
+    static QHash<QgsMapCanvas*, QgsMapCanvasTracer*>& tracers();
+
     QgsMapCanvas* mCanvas;
     QgsMessageBar* mMessageBar;
     QgsMessageBarItem* mLastMessage;
 
     QAction* mActionEnableTracing;
-
-    static QHash<QgsMapCanvas*, QgsMapCanvasTracer*> sTracers;
 };
 
 #endif // QGSMAPCANVASTRACER_H