various node UI improvements

app/node/generator/solid/solid.cpp

@@ -1,11 +1,15 @@
 #include "solid.h"
 
-SolidGenerator::SolidGenerator(QObject *parent) :
-  Node(parent),
+SolidGenerator::SolidGenerator() :
   texture_(nullptr)
 {
-  texture_output_ = new NodeOutput(this);
+  color_input_ = new NodeInput();
+  color_input_->add_data_input(NodeParam::kColor);
+  AddParameter(color_input_);
+
+  texture_output_ = new NodeOutput();
   texture_output_->set_data_type(NodeOutput::kTexture);
+  AddParameter(texture_output_);
 }
 
 QString SolidGenerator::Name()

app/node/generator/solid/solid.h

@@ -9,7 +9,7 @@ class SolidGenerator : public Node
 {
   Q_OBJECT
 public:
-  SolidGenerator(QObject* parent = nullptr);
+  SolidGenerator();
 
   virtual QString Name() override;
   virtual QString Category() override;
@@ -21,6 +21,8 @@ public slots:
   virtual void Process(const rational &time) override;
 
 private:
+  NodeInput* color_input_;
+
   NodeOutput* texture_output_;
 
   QOpenGLTexture* texture_;