Add Drawable.

src/Drawable.h

+
+#ifndef DRAWABLE_H
+#define DRAWABLE_H
+
+template <typename T>
+class Drawable {
+  public:
+    bool draw(void *args) {
+        static_cast<T*>(this)->draw(args);
+    }
+};
+#endif /* DRAWABLE_H */

src/canvas.cc

+#include "canvas.h"
+
+std::shared_ptr<Canvas> Canvas::MakeCanvas(int width, int height, PixelTypes pixType) {
+
+}

src/canvas.h

 
 #include <memory>
+#include "Drawable.h"
 
 #ifndef CANVAS_H
 #define CANVAS_H
@@ -8,8 +9,13 @@ enum PixelTypes {};
 
 class Canvas {
 public:
-    Canvas(int width, int height, PixelTypes pixType);
+    static std::shared_ptr<Canvas> MakeCanvas(int width, int height, PixelTypes pixType);
+
+    template<typename T>
+    bool draw(Drawable<T>* drawable);
 
+protected:
+    Canvas(int width, int height, PixelTypes pixType);
 };
 
 #endif /* CANVAS_H */