gizmos: implemented pathway for node to draw on the viewer

app/node/generator/matrix/matrix.cpp

@@ -110,6 +110,17 @@ NodeValueTable MatrixGenerator::Value(NodeValueDatabase &value) const
   return output;
 }
 
+bool MatrixGenerator::HasGizmos() const
+{
+  return true;
+}
+
+void MatrixGenerator::DrawGizmos(QPainter *p, const QRect& viewport) const
+{
+  p->setPen(Qt::white);
+  p->drawEllipse(viewport);
+}
+
 void MatrixGenerator::UniformScaleChanged()
 {
   scale_input_->set_property("disabley", uniform_scale_input_->get_standard_value().toBool());

app/node/generator/matrix/matrix.h

@@ -42,6 +42,9 @@ public:
 
   virtual NodeValueTable Value(NodeValueDatabase& value) const override;
 
+  virtual bool HasGizmos() const override;
+  virtual void DrawGizmos(QPainter *p, const QRect &viewport) const override;
+
 private:
   NodeInput* position_input_;