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_;
 

app/node/node.cpp

@@ -268,6 +268,15 @@ QList<NodeOutput *> Node::GetOutputs() const
   return {output_};
 }
 
+bool Node::HasGizmos() const
+{
+  return false;
+}
+
+void Node::DrawGizmos(QPainter *, const QRect &) const
+{
+}
+
 void Node::CopyInputs(Node *source, Node *destination, bool include_connections)
 {
   Q_ASSERT(source->id() == destination->id());

app/node/node.h

@@ -23,6 +23,7 @@
 
 #include <QCryptographicHash>
 #include <QObject>
+#include <QPainter>
 #include <QPointF>
 #include <QXmlStreamWriter>
 
@@ -352,6 +353,10 @@ public:
 
   QList<NodeOutput*> GetOutputs() const;
 
+  virtual bool HasGizmos() const;
+
+  virtual void DrawGizmos(QPainter* p, const QRect &viewport) const;
+
 protected:
   void AddInput(NodeInput* input);