Fix Selection center marks

- CenterMarks were difficult to select due to small
  pick radius.  Pick radius is now an adjustable
  parameter.

src/Mod/TechDraw/Gui/QGICMark.cpp

@@ -87,3 +87,26 @@ void QGICMark::paint(QPainter *painter, const QStyleOptionGraphicsItem *option,
 
     QGIVertex::paint (painter, &myOption, widget);
 }
+
+QRectF QGICMark::boundingRect() const
+{
+    return shape().controlPointRect();
+}
+
+QPainterPath QGICMark::shape() const
+{
+    QPainterPath outline;
+    QPainterPathStroker stroker;
+    stroker.setWidth(getMarkFuzz());
+    outline = stroker.createStroke(path());
+    return outline;
+}
+
+ double QGICMark::getMarkFuzz(void) const
+{
+    Base::Reference<ParameterGrp> hGrp = App::GetApplication().GetUserParameter().GetGroup("BaseApp")->
+                                         GetGroup("Preferences")->GetGroup("Mod/TechDraw/General");
+    double result = hGrp->GetFloat("MarkFuzz",20.0);
+    return result;
+}
+

src/Mod/TechDraw/Gui/QGICMark.h

@@ -38,6 +38,9 @@ public:
     int type() const { return Type;}
     virtual void paint(QPainter * painter, const QStyleOptionGraphicsItem * option, QWidget * widget = 0 );
 
+    virtual QRectF boundingRect() const override;
+    virtual QPainterPath shape() const override;
+
     int getProjIndex() const { return projIndex; }
 
     void draw(void);
@@ -47,6 +50,8 @@ public:
     void setThick(float t);
     virtual void setPrettyNormal();
 
+    double getMarkFuzz(void) const;
+
 protected:
     int projIndex;
     QColor getCMarkColor();