import com.sun.opengl.util.*;
import com.sun.opengl.util.texture.*;
import javax.media.opengl.*;
import javax.media.opengl.glu.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;

public class BasicGLSL implements GLEventListener {

   private String textureImageFile = "C:/data/nhs/images/flower.jpg";

   public int vertexShaderId, fragmentShaderId, shaderProgramId;

   private Texture texture;
   
   private float red = 1.f, green = 0.f, blue = 0.5f;
   
   

   public void init(GLAutoDrawable drawable) {
      GL gl = drawable.getGL();

      // create texture
      try {
         texture = TextureIO.newTexture(new File(textureImageFile), false);
      } catch (Exception e) {
         System.err.println("texture creation failed.");
      }

      //create and compile vertex shader

      /*
       void main(){ 
       gl_Position = ftransform(); 
       }
       */
      
      String vertexShaderSource = "void main(){ gl_Position = ftransform(); }";
      
      
      vertexShaderId = gl.glCreateShaderObjectARB(GL.GL_VERTEX_SHADER_ARB);
      gl.glShaderSourceARB(vertexShaderId, 1, new String[] { vertexShaderSource },
            new int[] { vertexShaderSource.length() }, 0);
      gl.glCompileShaderARB(vertexShaderId);

      
      // create and compile fragment shader
      
      /* 
       uniform vec4 colour; 
       uniform sampler2D tex;
       void main (void) { 
       gl_FragColor = colour*texture2D(tex,gl_TexCoord[0].st); 
       }
       */
      
      String fragmentShaderSource = "uniform vec4 colour;\n";
      fragmentShaderSource +="uniform sampler2D tex;\n";
      fragmentShaderSource +="void main (void){gl_FragColor = colour*texture2D(tex, gl_TexCoord[0].st);}";
      
      fragmentShaderId = gl
            .glCreateShaderObjectARB(GL.GL_FRAGMENT_SHADER_ARB);
      gl.glShaderSourceARB(fragmentShaderId, 1,
            new String[] { fragmentShaderSource }, new int[] { fragmentShaderSource
                  .length() }, 0);
      gl.glCompileShaderARB(fragmentShaderId);
      shaderProgramId = gl.glCreateProgramObjectARB();

      // link shader program
      gl.glAttachObjectARB(shaderProgramId, vertexShaderId);
      gl.glAttachObjectARB(shaderProgramId, fragmentShaderId);
      gl.glLinkProgramARB(shaderProgramId);

      // 
      gl.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
      gl.glClearDepth(1.0f);
      gl.setSwapInterval(1);
   }

   public void display(GLAutoDrawable drawable) {
      GL gl = drawable.getGL();

      gl.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);

      texture.bind();
      texture.enable();

      gl.glUseProgramObjectARB(shaderProgramId);

      int colourVarNr = gl.glGetUniformLocationARB(shaderProgramId, "colour");
      gl.glUniform4fARB(colourVarNr, red, green, blue, 1);

      int texSampler = gl.glGetUniformLocationARB(shaderProgramId, "tex");
      gl.glUniform1i(texSampler, 0);

      gl.glActiveTexture(GL.GL_TEXTURE0);
      gl.glEnable(GL.GL_TEXTURE_2D);

      gl.glBegin(GL.GL_TRIANGLE_STRIP);
      gl.glTexCoord2f(0, 1);
      gl.glVertex3f(-1, 1, 0);
      gl.glTexCoord2f(0, 0);
      gl.glVertex3f(-1, -1, 0);
      gl.glTexCoord2f(1, 1);
      gl.glVertex3f(1, 1, 0);
      gl.glTexCoord2f(1, 0);
      gl.glVertex3f(1, -1, 0);
      gl.glEnd();

      gl.glUseProgramObjectARB(0);

      texture.disable();
   }

   public void displayChanged(GLAutoDrawable drawable, boolean modeChanged,
         boolean deviceChanged) {
   }

   public void reshape(GLAutoDrawable drawable, int x, int y, int width,
         int height) {
      final float h = (float) width / (float) height;
      GL gl = drawable.getGL();
      GLU glu = new GLU();
      gl.glViewport(0, 0, width, height);
      gl.glMatrixMode(GL.GL_PROJECTION);
      gl.glLoadIdentity();
      glu.gluPerspective(80, h, 0.1f, 20.f);
      gl.glMatrixMode(GL.GL_MODELVIEW);
      gl.glLoadIdentity();
      glu.gluLookAt(0, 0, 2, 0, 0, 0, 0, 1, 0);
   }

   // /////////////////////////////////////////////////////////
   // MAIN
   // /////////////////////////////////////////////////////////

   public static void main(String[] args) {
      GLCanvas canvas = new GLCanvas();
      canvas.addGLEventListener(new BasicGLSL());
      final Animator animator = new Animator(canvas);
      Frame frame = new Frame("BasicGLSL");
      frame.setSize(400, 400);
      frame.add(canvas);
      frame.addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent e) {
            runExit(animator);
         }
      });
      frame.setVisible(true);
      canvas.requestFocus();
      animator.start();
   }

   protected static void runExit(final Animator animator) {
      new Thread(new Runnable() {
         public void run() {
            animator.stop();
            System.exit(0);
         }
      }).start();
   }

}