#include <osg/Geode>
#include <osg/Geometry>
#include <osg/PointSprite>
#include <osgViewer/Viewer>
#include <osgViewer/ViewerEventHandlers>

osg::Node* createCircle(const osg::Vec4f& color, float radius)
{
    osg::Geode* geode = new osg::Geode;
    osg::Geometry* geom = new osg::Geometry;

    // Draw a simple circle, every 3 degrees
    osg::Vec3Array* vertices = new osg::Vec3Array();
    for (int k = 0; k < 120; ++k)
    {
      double asRadians = osg::DegreesToRadians(3.0 * k);
      vertices->push_back(osg::Vec3(radius * sin(asRadians), 0.0, radius * cos(asRadians)));
    }

    osg::Vec4Array* colors = new osg::Vec4Array(osg::Array::BIND_OVERALL);
    colors->push_back(color);

    geom->addPrimitiveSet(new osg::DrawArrays(GL_POINTS, 0, 120));
    geom->setVertexArray(vertices);
    geom->setColorArray(colors);
    geode->addDrawable(geom);

    return geode;
}

osg::Node* createScene()
{
    osg::Group* group = new osg::Group;
    group->addChild(createCircle(osg::Vec4f(0.5, 1, 0.5, 1), 85.f));

    osgText::Text* text = new osgText::Text;
    text->setText("Press any key to turn on PointSprite.");
    text->setCharacterSize(10.f);
    text->setFont("fonts/times.ttf");
    text->setAxisAlignment(osgText::Text::XZ_PLANE);
    text->setAlignment(osgText::Text::CENTER_CENTER);
    group->addChild(text);

    return group;
}

struct PointSpriteAdder : public osgGA::GUIEventHandler
{
  explicit PointSpriteAdder(osg::StateSet* stateSet)
    : stateSet_(stateSet)
  {
  }

  virtual bool handle(const osgGA::GUIEventAdapter& ea, osgGA::GUIActionAdapter& aa, osg::Object* obj, osg::NodeVisitor* nv)
  {
    if (ea.getEventType() == ea.KEYDOWN)
    {
      //////////////////////////////////////////////////////////////
      // PointSprite::checkValidityOfModes() never gets called here
      OSG_NOTICE << "Turning on Point Sprite.\n";
      stateSet_->setTextureAttributeAndModes(0, new osg::PointSprite);
    }
    return GUIEventHandler::handle(ea, aa, obj, nv);
  }

  osg::ref_ptr<osg::StateSet> stateSet_;
};

int main(int argc, char** argv)
{
    osg::ArgumentParser arguments(&argc, argv);

    // construct the viewer.
    osgViewer::Viewer viewer(arguments);
    osg::Node* scene = createScene();
    viewer.setSceneData(scene);
    viewer.setUpViewInWindow(100, 100, 800, 600);
    viewer.addEventHandler(new osgViewer::StatsHandler());

    OSG_NOTICE << "Point Sprite Mode Validity Tester\n";
    OSG_NOTICE << "Arguments:\n";
    OSG_NOTICE << "  --camera    Apply osg::PointSprite to Camera's state set only\n";
    OSG_NOTICE << "  --scene     Apply osg::PointSprite to Scene's state set only\n";
    OSG_NOTICE << "\n";

    if (arguments.read("--camera"))
    {
      OSG_NOTICE << "--camera was detected; this will not call PointSprite::checkValidityOfModes().\n";
      OSG_NOTICE << "Try calling with --scene to see 'correct' behavior.\n";

      //////////////////////////////////////////////////////////////
      // PointSprite::checkValidityOfModes() never gets called here
      viewer.getCamera()->getOrCreateStateSet()->setTextureAttributeAndModes(0, new osg::PointSprite);
    }
    else if (arguments.read("--scene"))
    {
      OSG_NOTICE << "--scene was detected; this WILL correctly call PointSprite::checkValidityOfModes().\n";

      //////////////////////////////////////////////////////////////
      // PointSprite::checkValidityOfModes() will get called here, because the scene
      // is traversed by GLObjectsVisitor during first render after setSceneData() call.
      // Therefore, this correctly sets up the mode validity on GL_POINT_SPRITE.
      scene->getOrCreateStateSet()->setTextureAttributeAndModes(0, new osg::PointSprite);
    }
    else
    {
      OSG_NOTICE << "No arguments detected; this will not correctly call PointSprite::checkValidityOfModes().\n";
      OSG_NOTICE << "Try calling with --scene to see 'correct' behavior.\n";
    }

    viewer.addEventHandler(new PointSpriteAdder(scene->getOrCreateStateSet()));

    return viewer.run();
}