I want to create a VisualPlugin , I tried following the tutorial in the gazebo website , which uses a WorldPlugin , and going along those lines I created the following class

#include <gazebo/common/Plugin.hh>
#include <gazebo/rendering/Visual.hh>


namespace gazebo
{   


 class GZ_PLUGIN_VISIBLE WorldPluginTutorial : public VisualPlugin
{
public: WorldPluginTutorial() 
        {
          printf("Hello World!\n");
        }



 public: virtual void Load(rendering::VisualPtr _visual,
    sdf::ElementPtr _sdf)
    {
        printf("loaded!");
    if (!_visual || !_sdf)
    {
            gzerr << "No visual or SDF element specified. Plugin won't load." <<
            std::endl;
            return;
    }


    }


 /* following the model shown in the basic plugin tutorial in the gazebo website   
public: void Load(physics::WorldPtr _world, sdf::ElementPtr _sdf)
        {
            printf("Loaded!\n");
        }
*/


};
GZ_REGISTER_VISUAL_PLUGIN(WorldPluginTutorial)

 }

which creates libgazebolineplugin.so shared library However the Load() function does not seem to be working, It prints Hello World! and then does nothing.

I used the following sdf file a part of blink_visual.world

<?xml version="1.0" ?>
<sdf version="1.5">
<world name="default">
<include>
  <uri>model://ground_plane</uri>
</include>
<include>
  <uri>model://sun</uri>
</include>
<model name="box_sim">
  <pose>0 0 0.5 0 0 0</pose>
  <link name="link">
    <collision name="collision">
      <geometry>
        <box>
          <size>1 1 1</size>
        </box>
      </geometry>
    </collision>
    <visual name="visual">
      <geometry>
        <box>
          <size>1 1 1</size>
        </box>
      </geometry>
      <plugin name="gazebo_line_plugin" filename="libgazebo_line_plugin.so">
        <color_a>1 0 0 1</color_a>
        <color_b>1 0 0 0</color_b>
        <period>10</period>
      </plugin>
    </visual>
  </link>
</model>
</world>
</sdf>

I would really appreciate it if someone told me what I was doing wrong , and how I can correct it.