import java.awt.GridLayout;
import java.nio.ByteBuffer;
import java.nio.FloatBuffer;
import javax.media.opengl.GL;
import javax.media.opengl.GL2;
import javax.media.opengl.GLAutoDrawable;
import javax.media.opengl.GLEventListener;
import javax.media.opengl.awt.GLCanvas;
import javax.media.opengl.awt.GLJPanel;
import javax.media.opengl.glu.GLU;
import javax.swing.JFrame;


public class Renderer extends GLCanvas implements GLEventListener {
    
    private final int triangleSizeInBytes = 4*3*3;
    private final FloatBuffer triangle;
    private final GLU glu = new GLU();
        
    private boolean useVertexArray = true;

    public static void main(String[] args) {
        JFrame frame = new JFrame("JOGL Test");
        frame.setLayout(new GridLayout(1, 1));
        frame.add(new Renderer());
        frame.setSize(400, 300);
        frame.setVisible(true);
    }
    
    public Renderer() {
        addGLEventListener(this);
        triangle = ByteBuffer.allocateDirect(triangleSizeInBytes).asFloatBuffer();
        float[] triangleArray = { -1.0f, -1.0f, 0.0f,
                                   1.0f, -1.0f, 0.0f,
                                   0.0f,  1.0f, 0.0f };
        triangle.put(triangleArray).flip();
    }

    @Override
    public void init(GLAutoDrawable drawable) {
        GL2 gl = drawable.getGL().getGL2();
        gl.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
    }

    @Override
    public void dispose(GLAutoDrawable drawable) {
    }

    @Override
    public void display(GLAutoDrawable drawable) {
        GL2 gl = drawable.getGL().getGL2();
        gl.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);
        gl.glLoadIdentity();
        
        gl.glTranslatef(0.0f, 0.0f, -4.0f);
        
        gl.glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
        
        if (useVertexArray) {
            gl.glEnableClientState(GL2.GL_VERTEX_ARRAY);
            gl.glVertexPointer(3, GL2.GL_FLOAT, 0, triangle);
            gl.glDrawArrays(GL2.GL_TRIANGLES, 0, 3);
            gl.glDisableClientState(GL2.GL_VERTEX_ARRAY);
        } else {
            gl.glBegin(GL2.GL_TRIANGLES);
            gl.glVertex3f(triangle.get(0), triangle.get(1), triangle.get(2));
            gl.glVertex3f(triangle.get(3), triangle.get(4), triangle.get(5));
            gl.glVertex3f(triangle.get(6), triangle.get(7), triangle.get(8));
            gl.glEnd();
        }
    }

    @Override
    public void reshape(GLAutoDrawable drawable, int x, int y, int width, int height) {
        GL2 gl = drawable.getGL().getGL2();
        if (height <= 0) // avoid a divide by zero error!
            height = 1;
        final float h = (float) width / (float) height;
        gl.glViewport(0, 0, width, height);
        gl.glMatrixMode(GL2.GL_PROJECTION);
        gl.glLoadIdentity();
        glu.gluPerspective(45.0f, h, 1.0f, 1000.0f);
        gl.glMatrixMode(GL2.GL_MODELVIEW);
        gl.glLoadIdentity();
    }
    
}