/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2003 Robert Osfield 
 *
 * This library is open source and may be redistributed and/or modified under  
 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or 
 * (at your option) any later version.  The full license is in LICENSE file
 * included with this distribution, and on the openscenegraph.org website.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
 * OpenSceneGraph Public License for more details.
*/

#include <osgUtil/Optimizer>
#include <osgDB/ReadFile>
#include <osgProducer/Viewer>

#include <osg/Material>
#include <osg/Geode>
#include <osg/BlendFunc>
#include <osg/Depth>
#include <osg/Projection>
#include <osg/PolygonOffset>
#include <osg/MatrixTransform>

#include <osgText/Text>


osg::Node* createHUD()
{
    osg::Geode* geode = new osg::Geode();
    
    std::string timesFont("fonts/arial.ttf");

    // turn lighting off for the text and disable depth test to ensure its always ontop.
    osg::StateSet* stateset = geode->getOrCreateStateSet();
    stateset->setMode(GL_LIGHTING,osg::StateAttribute::OFF);

#if 0
    // to ensure the hud appears on top we can either use osg::Depth to force the 
    // depth fragments to be placed at the front of the screen.
    stateset->setAttribute(new osg::Depth(osg::Depth::LESS,0.0,0.0001));
#else
    // or disable depth test, and make sure that the hud is drawn after everything 
    // else so that it always appears ontop.
    stateset->setMode(GL_DEPTH_TEST,osg::StateAttribute::OFF);
    stateset->setRenderBinDetails(11,"RenderBin");
#endif

    osg::Vec3 position(150.0f,800.0f,0.0f);
    osg::Vec3 delta(0.0f,-120.0f,0.0f);

    {
        osgText::Text* text = new  osgText::Text;
        geode->addDrawable( text );

        text->setFont(timesFont);
        text->setPosition(position);
        text->setText("Head Up Displays are simple :-)");
        
        position += delta;
    }    


    {
        osgText::Text* text = new  osgText::Text;
        geode->addDrawable( text );

        text->setFont(timesFont);
        text->setPosition(position);
        text->setText("All you need to do is create your text in a subgraph.");
        
        position += delta;
    }    


    {
        osgText::Text* text = new  osgText::Text;
        geode->addDrawable( text );

        text->setFont(timesFont);
        text->setPosition(position);
        text->setText("Disable depth test in this subgraph to ensure its always ontop.");
        
        position += delta;
    }    

    {
        osgText::Text* text = new  osgText::Text;
        geode->addDrawable( text );

        text->setFont(timesFont);
        text->setPosition(position);
        text->setText("Then place an osg::Projection node above the subgraph\nto create an orthographic projection.");
        
        position += delta;
    }    

    {
        osgText::Text* text = new  osgText::Text;
        geode->addDrawable( text );

        text->setFont(timesFont);
        text->setPosition(position);
        text->setText("And add an osg::ModelViewMatrix set to ABSOLUTE to ensure\nit remains independent from any external model view matrices.");
        
        position += delta;
    } 
    
    
    
    {
        osg::BoundingBox bb;
        for(unsigned int i=0;i<geode->getNumDrawables();++i)
        {
            bb.expandBy(geode->getDrawable(i)->getBound());
        }

        osg::Geometry* geom = new osg::Geometry;

        osg::Vec3Array* vertices = new osg::Vec3Array;
        float depth = bb.zMin()-0.1;
        vertices->push_back(osg::Vec3(bb.xMin(),bb.yMax(),depth));
        vertices->push_back(osg::Vec3(bb.xMin(),bb.yMin(),depth));
        vertices->push_back(osg::Vec3(bb.xMax(),bb.yMin(),depth));
        vertices->push_back(osg::Vec3(bb.xMax(),bb.yMax(),depth));
        geom->setVertexArray(vertices);

        osg::Vec3Array* normals = new osg::Vec3Array;
        normals->push_back(osg::Vec3(0.0f,0.0f,1.0f));
        geom->setNormalArray(normals);
        geom->setNormalBinding(osg::Geometry::BIND_OVERALL);

        osg::Vec4Array* colors = new osg::Vec4Array;
        colors->push_back(osg::Vec4(1.0f,1.0,0.8f,0.2f));
        geom->setColorArray(colors);
        geom->setColorBinding(osg::Geometry::BIND_OVERALL);

        geom->addPrimitiveSet(new osg::DrawArrays(GL_QUADS,0,4));
        
        osg::StateSet* stateset = geom->getOrCreateStateSet();
        stateset->setMode(GL_BLEND,osg::StateAttribute::ON);
        //stateset->setAttribute(new osg::PolygonOffset(1.0f,1.0f),osg::StateAttribute::ON);
        stateset->setRenderingHint(osg::StateSet::TRANSPARENT_BIN);

        geode->addDrawable(geom);
    }

    // create the hud.
    osg::MatrixTransform* modelview_abs = new osg::MatrixTransform;
    modelview_abs->setReferenceFrame(osg::Transform::RELATIVE_TO_ABSOLUTE);
    modelview_abs->setMatrix(osg::Matrix::identity());
    modelview_abs->addChild(geode);

    osg::Projection* projection = new osg::Projection;
    projection->setMatrix(osg::Matrix::ortho2D(0,1280,0,1024));
    projection->addChild(modelview_abs);

    return projection;

}

int main( int argc, char **argv )
{

    // use an ArgumentParser object to manage the program arguments.
    osg::ArgumentParser arguments(&argc,argv);
    
    // set up the usage document, in case we need to print out how to use this program.
    arguments.getApplicationUsage()->setDescription(arguments.getApplicationName()+" is the example which demonstrates how to do Head Up Displays.");
    arguments.getApplicationUsage()->setCommandLineUsage(arguments.getApplicationName()+" [options] [filename] ...");
    arguments.getApplicationUsage()->addCommandLineOption("-h or --help","Display this information");
    

    // construct the viewer.
    osgProducer::Viewer viewer(arguments);

    // set up the value with sensible default event handlers.
    viewer.setUpViewer(osgProducer::Viewer::STANDARD_SETTINGS);

    // get details on keyboard and mouse bindings used by the viewer.
    viewer.getUsage(*arguments.getApplicationUsage());

    // if user request help write it out to cout.
    if (arguments.read("-h") || arguments.read("--help"))
    {
        arguments.getApplicationUsage()->write(std::cout);
        return 1;
    }

    // any option left unread are converted into errors to write out later.
    arguments.reportRemainingOptionsAsUnrecognized();

    // report any errors if they have occured when parsing the program aguments.
    if (arguments.errors())
    {
        arguments.writeErrorMessages(std::cout);
        return 1;
    }
    
    // read the scene from the list of file specified commandline args.
    osg::ref_ptr<osg::Node> scene = osgDB::readNodeFiles(arguments);

    osg::ref_ptr<osg::Group> group = dynamic_cast<osg::Group*>(scene.get());
    if (!group)
    {
        group = new osg::Group;
        group->addChild(scene.get());
    }

    // add the HUD subgraph.    
    group->addChild(createHUD());

    // set the scene to render
    viewer.setSceneData(group.get());

    // create the windows and run the threads.
    viewer.realize();

    while( !viewer.done() )
    {
        // wait for all cull and draw threads to complete.
        viewer.sync();

        // update the scene by traversing it with the the update visitor which will
        // call all node update callbacks and animations.
        viewer.update();
         
        // fire off the cull and draw traversals of the scene.
        viewer.frame();
        
    }
    
    // wait for all cull and draw threads to complete before exit.
    viewer.sync();
    
    return 0;
}
