diff --git a/src/Gui/SelectionFilter.h b/src/Gui/SelectionFilter.h
index 505b0db9c4..aff05b6715 100644
--- a/src/Gui/SelectionFilter.h
+++ b/src/Gui/SelectionFilter.h
@@ -109,6 +109,13 @@ public:
     virtual bool allow(App::Document*,App::DocumentObject*, const char*);
 
 protected:
+    static SelectionFilter* nullPointer() {
+        return nullptr;
+    }
+
+    static const char* nullString() {
+        return nullptr;
+    }
     SelectionFilterGate();
 
 protected:
diff --git a/src/Mod/Fem/Gui/FemSelectionGate.h b/src/Mod/Fem/Gui/FemSelectionGate.h
index 5c5e26e200..238a4aab30 100644
--- a/src/Mod/Fem/Gui/FemSelectionGate.h
+++ b/src/Mod/Fem/Gui/FemSelectionGate.h
@@ -38,9 +38,9 @@ class FemSelectionGate : public Gui::SelectionFilterGate
     };
 
     FemSelectionGate(ElemType type)
-        : Gui::SelectionFilterGate((Gui::SelectionFilter*)nullptr),Type(type)
+        : Gui::SelectionFilterGate(nullPointer()),Type(type)
     {
-    };
+    }
 
     ElemType Type;
 
diff --git a/src/Mod/Part/Gui/DlgExtrusion.cpp b/src/Mod/Part/Gui/DlgExtrusion.cpp
index c9c8593cf9..6e52e86d61 100644
--- a/src/Mod/Part/Gui/DlgExtrusion.cpp
+++ b/src/Mod/Part/Gui/DlgExtrusion.cpp
@@ -63,7 +63,7 @@ public:
     bool canSelect;
 
     EdgeSelection()
-        : Gui::SelectionFilterGate((Gui::SelectionFilter*)nullptr)
+        : Gui::SelectionFilterGate(nullPointer())
     {
         canSelect = false;
     }
@@ -352,7 +352,7 @@ void DlgExtrusion::autoSolid()
 void DlgExtrusion::findShapes()
 {
     App::Document* activeDoc = App::GetApplication().getActiveDocument();
-    if (!activeDoc)
+    if (!activeDoc)
         return;
     Gui::Document* activeGui = Gui::Application::Instance->getDocument(activeDoc);
     this->document = activeDoc->getName();
diff --git a/src/Mod/Part/Gui/DlgFilletEdges.cpp b/src/Mod/Part/Gui/DlgFilletEdges.cpp
index db9ce6e7dc..dd39036d34 100644
--- a/src/Mod/Part/Gui/DlgFilletEdges.cpp
+++ b/src/Mod/Part/Gui/DlgFilletEdges.cpp
@@ -172,7 +172,7 @@ namespace PartGui {
         App::DocumentObject*& object;
     public:
         EdgeFaceSelection(App::DocumentObject*& obj)
-            : Gui::SelectionFilterGate((Gui::SelectionFilter*)nullptr), allowEdge(true), object(obj)
+            : Gui::SelectionFilterGate(nullPointer()), allowEdge(true), object(obj)
         {
         }
         void selectEdges()
@@ -528,7 +528,7 @@ void DlgFilletEdges::toggleCheckState(const QModelIndex& index)
 void DlgFilletEdges::findShapes()
 {
     App::Document* activeDoc = App::GetApplication().getActiveDocument();
-    if (!activeDoc)
+    if (!activeDoc)
         return;
 
     std::vector<App::DocumentObject*> objs = activeDoc->getObjectsOfType
diff --git a/src/Mod/Part/Gui/DlgProjectionOnSurface.cpp b/src/Mod/Part/Gui/DlgProjectionOnSurface.cpp
index b6f8847314..5f56dc00b6 100644
--- a/src/Mod/Part/Gui/DlgProjectionOnSurface.cpp
+++ b/src/Mod/Part/Gui/DlgProjectionOnSurface.cpp
@@ -77,7 +77,7 @@ public:
   bool canSelect;
 
   EdgeSelection()
-    : Gui::SelectionFilterGate((Gui::SelectionFilter*)nullptr)
+    : Gui::SelectionFilterGate(nullPointer())
   {
     canSelect = false;
   }
@@ -111,7 +111,7 @@ public:
   bool canSelect;
 
   FaceSelection()
-    : Gui::SelectionFilterGate((Gui::SelectionFilter*)nullptr)
+    : Gui::SelectionFilterGate(nullPointer())
   {
     canSelect = false;
   }
diff --git a/src/Mod/Part/Gui/DlgRevolution.cpp b/src/Mod/Part/Gui/DlgRevolution.cpp
index 787ee39b4b..08e8aea594 100644
--- a/src/Mod/Part/Gui/DlgRevolution.cpp
+++ b/src/Mod/Part/Gui/DlgRevolution.cpp
@@ -68,7 +68,7 @@ public:
     bool canSelect;
 
     EdgeSelection()
-        : Gui::SelectionFilterGate((Gui::SelectionFilter*)nullptr)
+        : Gui::SelectionFilterGate(nullPointer())
     {
         canSelect = false;
     }
@@ -329,7 +329,7 @@ void DlgRevolution::keyPressEvent(QKeyEvent* ke)
 void DlgRevolution::findShapes()
 {
     App::Document* activeDoc = App::GetApplication().getActiveDocument();
-    if (!activeDoc)
+    if (!activeDoc)
         return;
     Gui::Document* activeGui = Gui::Application::Instance->getDocument(activeDoc);
 
diff --git a/src/Mod/Part/Gui/TaskShapeBuilder.cpp b/src/Mod/Part/Gui/TaskShapeBuilder.cpp
index 1fe74024eb..b85ceb504b 100644
--- a/src/Mod/Part/Gui/TaskShapeBuilder.cpp
+++ b/src/Mod/Part/Gui/TaskShapeBuilder.cpp
@@ -62,7 +62,7 @@ namespace PartGui {
         enum Type {VERTEX, EDGE, FACE, ALL};
         Type mode;
         ShapeSelection()
-            : Gui::SelectionFilterGate((Gui::SelectionFilter*)nullptr), mode(ALL)
+            : Gui::SelectionFilterGate(nullPointer()), mode(ALL)
         {
         }
         void setMode(Type mode)
@@ -172,7 +172,7 @@ void ShapeBuilderWidget::on_createButton_clicked()
 {
     int mode = d->bg.checkedId();
     Gui::Document* doc = Gui::Application::Instance->activeDocument();
-    if (!doc)
+    if (!doc)
         return;
 
     try {
diff --git a/src/Mod/Part/Gui/TaskSweep.cpp b/src/Mod/Part/Gui/TaskSweep.cpp
index 94a720696e..7ac38137be 100644
--- a/src/Mod/Part/Gui/TaskSweep.cpp
+++ b/src/Mod/Part/Gui/TaskSweep.cpp
@@ -79,7 +79,7 @@ public:
     {
     public:
         EdgeSelection()
-            : Gui::SelectionFilterGate((Gui::SelectionFilter*)nullptr)
+            : Gui::SelectionFilterGate(nullPointer())
         {
         }
         bool allow(App::Document* /*pDoc*/, App::DocumentObject*pObj, const char*sSubName)
diff --git a/src/Mod/Part/Gui/TaskThickness.cpp b/src/Mod/Part/Gui/TaskThickness.cpp
index d6f7ff3c59..5c6f7146ff 100644
--- a/src/Mod/Part/Gui/TaskThickness.cpp
+++ b/src/Mod/Part/Gui/TaskThickness.cpp
@@ -71,7 +71,7 @@ public:
         const App::DocumentObject* object;
     public:
         FaceSelection(const App::DocumentObject* obj)
-            : Gui::SelectionFilterGate((Gui::SelectionFilter*)nullptr), object(obj)
+            : Gui::SelectionFilterGate(nullPointer()), object(obj)
         {
         }
         bool allow(App::Document* /*pDoc*/, App::DocumentObject*pObj, const char*sSubName)
diff --git a/src/Mod/PartDesign/Gui/ReferenceSelection.h b/src/Mod/PartDesign/Gui/ReferenceSelection.h
index c8805882e5..e760e68804 100644
--- a/src/Mod/PartDesign/Gui/ReferenceSelection.h
+++ b/src/Mod/PartDesign/Gui/ReferenceSelection.h
@@ -43,7 +43,7 @@ class ReferenceSelection : public Gui::SelectionFilterGate
 public:
     ReferenceSelection(const App::DocumentObject* support_,
                        AllowSelectionFlags type)
-        : Gui::SelectionFilterGate(static_cast<Gui::SelectionFilter*>(nullptr))
+        : Gui::SelectionFilterGate(nullPointer())
         , support(support_)
         , type(type)
     {
@@ -71,7 +71,7 @@ class NoDependentsSelection : public Gui::SelectionFilterGate
 
 public:
     NoDependentsSelection(const App::DocumentObject* support_)
-        : Gui::SelectionFilterGate((Gui::SelectionFilter*)nullptr), support(support_)
+        : Gui::SelectionFilterGate(nullPointer()), support(support_)
     {
     }
     /**
@@ -87,7 +87,7 @@ class CombineSelectionFilterGates: public Gui::SelectionFilterGate
 
 public:
     CombineSelectionFilterGates(std::unique_ptr<Gui::SelectionFilterGate> &filter1_, std::unique_ptr<Gui::SelectionFilterGate> &filter2_)
-        : Gui::SelectionFilterGate((Gui::SelectionFilter*)nullptr), filter1(std::move(filter1_)), filter2(std::move(filter2_))
+        : Gui::SelectionFilterGate(nullPointer()), filter1(std::move(filter1_)), filter2(std::move(filter2_))
     {
     }
     bool allow(App::Document* pDoc, App::DocumentObject* pObj, const char* sSubName) override;
diff --git a/src/Mod/Sketcher/Gui/CommandConstraints.cpp b/src/Mod/Sketcher/Gui/CommandConstraints.cpp
index ffe9002c73..239b42ba5f 100644
--- a/src/Mod/Sketcher/Gui/CommandConstraints.cpp
+++ b/src/Mod/Sketcher/Gui/CommandConstraints.cpp
@@ -605,7 +605,7 @@ namespace SketcherGui {
         App::DocumentObject* object;
     public:
         GenericConstraintSelection(App::DocumentObject* obj)
-            : Gui::SelectionFilterGate((Gui::SelectionFilter*)nullptr)
+            : Gui::SelectionFilterGate(nullPointer())
             , object(obj), allowedSelTypes(0)
         {}
 
diff --git a/src/Mod/Sketcher/Gui/CommandCreateGeo.cpp b/src/Mod/Sketcher/Gui/CommandCreateGeo.cpp
index c7b4376c6d..b894a5eac1 100644
--- a/src/Mod/Sketcher/Gui/CommandCreateGeo.cpp
+++ b/src/Mod/Sketcher/Gui/CommandCreateGeo.cpp
@@ -5688,7 +5688,7 @@ namespace SketcherGui {
         App::DocumentObject* object;
     public:
         FilletSelection(App::DocumentObject* obj)
-            : Gui::SelectionFilterGate((Gui::SelectionFilter*)nullptr), object(obj)
+            : Gui::SelectionFilterGate(nullPointer()), object(obj)
         {}
 
         bool allow(App::Document * /*pDoc*/, App::DocumentObject *pObj, const char *sSubName)
@@ -6101,7 +6101,7 @@ namespace SketcherGui {
         App::DocumentObject* object;
     public:
         TrimmingSelection(App::DocumentObject* obj)
-            : Gui::SelectionFilterGate((Gui::SelectionFilter*)nullptr), object(obj)
+            : Gui::SelectionFilterGate(nullPointer()), object(obj)
         {}
 
         bool allow(App::Document * /*pDoc*/, App::DocumentObject *pObj, const char *sSubName)
@@ -6264,7 +6264,7 @@ namespace SketcherGui {
         App::DocumentObject* object;
     public:
         ExtendSelection(App::DocumentObject* obj)
-            : Gui::SelectionFilterGate((Gui::SelectionFilter*)nullptr)
+            : Gui::SelectionFilterGate(nullPointer())
             , object(obj)
             , disabled(false)
         {}
@@ -6579,7 +6579,7 @@ namespace SketcherGui {
         App::DocumentObject* object;
     public:
         SplittingSelection(App::DocumentObject* obj)
-            : Gui::SelectionFilterGate((Gui::SelectionFilter*)nullptr), object(obj)
+            : Gui::SelectionFilterGate(nullPointer()), object(obj)
         {}
 
         bool allow(App::Document * /*pDoc*/, App::DocumentObject *pObj, const char *sSubName)
@@ -6697,7 +6697,7 @@ namespace SketcherGui {
         App::DocumentObject* object;
     public:
         ExternalSelection(App::DocumentObject* obj)
-            : Gui::SelectionFilterGate((Gui::SelectionFilter*)nullptr), object(obj)
+            : Gui::SelectionFilterGate(nullPointer()), object(obj)
         {}
 
         bool allow(App::Document *pDoc, App::DocumentObject *pObj, const char *sSubName)
@@ -6884,7 +6884,7 @@ namespace SketcherGui {
         App::DocumentObject* object;
     public:
         CarbonCopySelection(App::DocumentObject* obj)
-        : Gui::SelectionFilterGate((Gui::SelectionFilter*)nullptr), object(obj)
+        : Gui::SelectionFilterGate(nullPointer()), object(obj)
         {}
 
         bool allow(App::Document *pDoc, App::DocumentObject *pObj, const char *sSubName)
diff --git a/src/Mod/Surface/Gui/TaskFilling.cpp b/src/Mod/Surface/Gui/TaskFilling.cpp
index d45e3adba5..e0d0c86ff7 100644
--- a/src/Mod/Surface/Gui/TaskFilling.cpp
+++ b/src/Mod/Surface/Gui/TaskFilling.cpp
@@ -184,7 +184,7 @@ class FillingPanel::ShapeSelection : public Gui::SelectionFilterGate
 {
 public:
     ShapeSelection(FillingPanel::SelectionMode& mode, Surface::Filling* editedObject)
-        : Gui::SelectionFilterGate(static_cast<Gui::SelectionFilter*>(nullptr))
+        : Gui::SelectionFilterGate(nullPointer())
         , mode(mode)
         , editedObject(editedObject)
     {
diff --git a/src/Mod/Surface/Gui/TaskFillingEdge.cpp b/src/Mod/Surface/Gui/TaskFillingEdge.cpp
index f5c34415f6..0f5db36719 100644
--- a/src/Mod/Surface/Gui/TaskFillingEdge.cpp
+++ b/src/Mod/Surface/Gui/TaskFillingEdge.cpp
@@ -56,7 +56,7 @@ class FillingEdgePanel::ShapeSelection : public Gui::SelectionFilterGate
 {
 public:
     ShapeSelection(FillingEdgePanel::SelectionMode& mode, Surface::Filling* editedObject)
-        : Gui::SelectionFilterGate(static_cast<Gui::SelectionFilter*>(nullptr))
+        : Gui::SelectionFilterGate(nullPointer())
         , mode(mode)
         , editedObject(editedObject)
     {
diff --git a/src/Mod/Surface/Gui/TaskFillingVertex.cpp b/src/Mod/Surface/Gui/TaskFillingVertex.cpp
index 371187c54d..59ea024c37 100644
--- a/src/Mod/Surface/Gui/TaskFillingVertex.cpp
+++ b/src/Mod/Surface/Gui/TaskFillingVertex.cpp
@@ -55,7 +55,7 @@ class FillingVertexPanel::VertexSelection : public Gui::SelectionFilterGate
 {
 public:
     VertexSelection(FillingVertexPanel::SelectionMode& mode, Surface::Filling* editedObject)
-        : Gui::SelectionFilterGate(static_cast<Gui::SelectionFilter*>(nullptr))
+        : Gui::SelectionFilterGate(nullPointer())
         , mode(mode)
         , editedObject(editedObject)
     {
diff --git a/src/Mod/Surface/Gui/TaskGeomFillSurface.cpp b/src/Mod/Surface/Gui/TaskGeomFillSurface.cpp
index ef3b359511..d14029663d 100644
--- a/src/Mod/Surface/Gui/TaskGeomFillSurface.cpp
+++ b/src/Mod/Surface/Gui/TaskGeomFillSurface.cpp
@@ -140,7 +140,7 @@ class GeomFillSurface::EdgeSelection : public Gui::SelectionFilterGate
 {
 public:
     EdgeSelection(bool appendEdges, Surface::GeomFillSurface* editedObject)
-        : Gui::SelectionFilterGate(static_cast<Gui::SelectionFilter*>(nullptr))
+        : Gui::SelectionFilterGate(nullPointer())
         , appendEdges(appendEdges)
         , editedObject(editedObject)
     {
diff --git a/src/Mod/Surface/Gui/TaskSections.cpp b/src/Mod/Surface/Gui/TaskSections.cpp
index d1ee741d54..6182253a28 100644
--- a/src/Mod/Surface/Gui/TaskSections.cpp
+++ b/src/Mod/Surface/Gui/TaskSections.cpp
@@ -188,7 +188,7 @@ class SectionsPanel::ShapeSelection : public Gui::SelectionFilterGate
 {
 public:
     ShapeSelection(SectionsPanel::SelectionMode& mode, Surface::Sections* editedObject)
-        : Gui::SelectionFilterGate(static_cast<Gui::SelectionFilter*>(nullptr))
+        : Gui::SelectionFilterGate(nullPointer())
         , mode(mode)
         , editedObject(editedObject)
     {