Move source to src.

src/trail.h

@@ -0,0 +1,36 @@
+// -*- C++ -*-
+
+#ifndef MBOSTOCK_TRAIL_H
+#define MBOSTOCK_TRAIL_H
+
+#include <vector>
+
+#include "model.h"
+#include "physics/vector.h"
+
+namespace mbostock {
+
+  class Trail {
+  public:
+    Trail(const Vector& origin);
+
+    bool add(const Vector& p);
+    inline const std::vector<Vector>& points() const { return points_; }
+
+  private:
+    std::vector<Vector> points_;
+  };
+
+  class TrailModel : public Model {
+  public:
+    TrailModel(const Trail& trail);
+
+    virtual void display();
+
+  private:
+    const Trail& trail_;
+  };
+
+}
+
+#endif