diff --git a/python/gui/auto_generated/qgsmapcanvas.sip.in b/python/gui/auto_generated/qgsmapcanvas.sip.in
index 56e0929d8cb..fb3ca85f7e7 100644
--- a/python/gui/auto_generated/qgsmapcanvas.sip.in
+++ b/python/gui/auto_generated/qgsmapcanvas.sip.in
@@ -28,10 +28,10 @@ Map canvas is a class for displaying all GIS data types on a canvas.
 #include "qgsmapcanvas.h"
 %End
 %ConvertToSubClassCode
-    if ( dynamic_cast<QgsMapCanvas *>( sipCpp ) != NULL )
+    if ( qobject_cast<QgsMapCanvas *>( sipCpp ) != nullptr )
       sipType = sipType_QgsMapCanvas;
     else
-      sipType = NULL;
+      sipType = nullptr;
 %End
   public:
 
diff --git a/src/gui/qgsmapcanvas.cpp b/src/gui/qgsmapcanvas.cpp
index 0fb6ddef2da..4558acbe833 100644
--- a/src/gui/qgsmapcanvas.cpp
+++ b/src/gui/qgsmapcanvas.cpp
@@ -243,14 +243,7 @@ QgsMapCanvas::~QgsMapCanvas()
   // delete canvas items prior to deleting the canvas
   // because they might try to update canvas when it's
   // already being destructed, ends with segfault
-  QList<QGraphicsItem *> list = mScene->items();
-  QList<QGraphicsItem *>::iterator it = list.begin();
-  while ( it != list.end() )
-  {
-    QGraphicsItem *item = *it;
-    delete item;
-    ++it;
-  }
+  qDeleteAll( mScene->items() );
 
   mScene->deleteLater();  // crashes in python tests on windows
 
@@ -1567,18 +1560,15 @@ void QgsMapCanvas::paintEvent( QPaintEvent *e )
 
 void QgsMapCanvas::updateCanvasItemPositions()
 {
-  QList<QGraphicsItem *> list = mScene->items();
-  QList<QGraphicsItem *>::iterator it = list.begin();
-  while ( it != list.end() )
+  const QList<QGraphicsItem *> items = mScene->items();
+  for ( QGraphicsItem *gi : items )
   {
-    QgsMapCanvasItem *item = dynamic_cast<QgsMapCanvasItem *>( *it );
+    QgsMapCanvasItem *item = dynamic_cast<QgsMapCanvasItem *>( gi );
 
     if ( item )
     {
       item->updatePosition();
     }
-
-    ++it;
   }
 }
 
@@ -1912,7 +1902,8 @@ void QgsMapCanvas::updateAutoRefreshTimer()
   // min auto refresh interval stores the smallest interval between layer auto refreshes. We automatically
   // trigger a map refresh on this minimum interval
   int minAutoRefreshInterval = -1;
-  Q_FOREACH ( QgsMapLayer *layer, mSettings.layers() )
+  const auto layers = mSettings.layers();
+  for ( QgsMapLayer *layer : layers )
   {
     if ( layer->hasAutoRefreshEnabled() && layer->autoRefreshInterval() > 0 )
       minAutoRefreshInterval = minAutoRefreshInterval > 0 ? std::min( layer->autoRefreshInterval(), minAutoRefreshInterval ) : layer->autoRefreshInterval();
@@ -2194,11 +2185,10 @@ bool QgsMapCanvas::event( QEvent *e )
 void QgsMapCanvas::refreshAllLayers()
 {
   // reload all layers in canvas
-  for ( int i = 0; i < layerCount(); i++ )
+  const QList<QgsMapLayer *> layers = mapSettings().layers();
+  for ( QgsMapLayer *layer : layers )
   {
-    QgsMapLayer *l = layer( i );
-    if ( l )
-      l->reload();
+    layer->reload();
   }
 
   // clear the cache
@@ -2229,11 +2219,10 @@ void QgsMapCanvas::setSegmentationToleranceType( QgsAbstractGeometry::Segmentati
 QList<QgsMapCanvasAnnotationItem *> QgsMapCanvas::annotationItems() const
 {
   QList<QgsMapCanvasAnnotationItem *> annotationItemList;
-  QList<QGraphicsItem *> itemList = mScene->items();
-  QList<QGraphicsItem *>::iterator it = itemList.begin();
-  for ( ; it != itemList.end(); ++it )
+  const QList<QGraphicsItem *> items = mScene->items();
+  for ( QGraphicsItem *gi : items )
   {
-    QgsMapCanvasAnnotationItem *aItem = dynamic_cast< QgsMapCanvasAnnotationItem *>( *it );
+    QgsMapCanvasAnnotationItem *aItem = dynamic_cast< QgsMapCanvasAnnotationItem *>( gi );
     if ( aItem )
     {
       annotationItemList.push_back( aItem );
@@ -2246,7 +2235,8 @@ QList<QgsMapCanvasAnnotationItem *> QgsMapCanvas::annotationItems() const
 void QgsMapCanvas::setAnnotationsVisible( bool show )
 {
   mAnnotationsVisible = show;
-  Q_FOREACH ( QgsMapCanvasAnnotationItem *item, annotationItems() )
+  const QList<QgsMapCanvasAnnotationItem *> items = annotationItems();
+  for ( QgsMapCanvasAnnotationItem *item : items )
   {
     item->setVisible( show );
   }
@@ -2322,14 +2312,14 @@ void QgsMapCanvas::startPreviewJob( int number )
 void QgsMapCanvas::stopPreviewJobs()
 {
   mPreviewTimer.stop();
-  QList< QgsMapRendererQImageJob * >::const_iterator it = mPreviewJobs.constBegin();
-  for ( ; it != mPreviewJobs.constEnd(); ++it )
+  const auto previewJobs = mPreviewJobs;
+  for ( auto previewJob : previewJobs )
   {
-    if ( *it )
+    if ( previewJob )
     {
-      disconnect( *it, &QgsMapRendererJob::finished, this, &QgsMapCanvas::previewJobFinished );
-      connect( *it, &QgsMapRendererQImageJob::finished, *it, &QgsMapRendererQImageJob::deleteLater );
-      ( *it )->cancelWithoutBlocking();
+      disconnect( previewJob, &QgsMapRendererJob::finished, this, &QgsMapCanvas::previewJobFinished );
+      connect( previewJob, &QgsMapRendererQImageJob::finished, previewJob, &QgsMapRendererQImageJob::deleteLater );
+      previewJob->cancelWithoutBlocking();
     }
   }
   mPreviewJobs.clear();
diff --git a/src/gui/qgsmapcanvas.h b/src/gui/qgsmapcanvas.h
index 3c3a4829c0e..86d81611613 100644
--- a/src/gui/qgsmapcanvas.h
+++ b/src/gui/qgsmapcanvas.h
@@ -75,10 +75,10 @@ class GUI_EXPORT QgsMapCanvas : public QGraphicsView
 
 #ifdef SIP_RUN
     SIP_CONVERT_TO_SUBCLASS_CODE
-    if ( dynamic_cast<QgsMapCanvas *>( sipCpp ) != NULL )
+    if ( qobject_cast<QgsMapCanvas *>( sipCpp ) != nullptr )
       sipType = sipType_QgsMapCanvas;
     else
-      sipType = NULL;
+      sipType = nullptr;
     SIP_END
 #endif