Why can´t I print a GL_POINTS?

OpenGL OpenGL: Basic Coding
1

I am trying to print a point using GL_POINTS, but the point is not beeing printed.

When I try to output a GL_QUAD, then it works, but not GL_POINTS. What am a doing wrong?

The reshape() method contains these two lines:

...
gl.glLoadIdentity();
glu.gluOrtho2D(0.0, 500.0, 0.0, 300.0);

my display() function contains this:

GL gl = drawable.getGL();
gl.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);
gl.glLoadIdentity();

gl.glColor3f(1.5f, 1.5f, 1.5f);
gl.glPointSize(5.0f);
gl.glBegin(GL.GL_POINTS);
    gl.glVertex2i(20, 150);
gl.glEnd();

Have I missed something?

2

gl.glPointSize(5.0f); -> try without point size, check you see a normal 1 pixel point.
beware from the screen edges, points are clipped before being sized, so stay far from the edges.

3

I have tested that but it still doesn´t work.

Here is the whole code. It works with QUADS but not with POINTS. No point is beeing printed.

Can you see any error in the code?

import com.sun.opengl.util.Animator;
import java.awt.Frame;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.event.*;
import javax.media.opengl.GL;
import javax.media.opengl.GLAutoDrawable;
import javax.media.opengl.GLCanvas;
import javax.media.opengl.GLEventListener;
import javax.media.opengl.glu.GLU;


public class SimpleJOGL implements GLEventListener {


    static Frame frame;

    public static void main(String[] args) {
        frame = new Frame("OpenGL Application");
        GLCanvas canvas = new GLCanvas();

        canvas.addGLEventListener(new SimpleJOGL());
        frame.add(canvas);
        frame.setSize(640, 480);
  
        final Animator animator = new Animator(canvas);
        frame.addWindowListener(new WindowAdapter() {

            public void windowClosing(WindowEvent e) {
                // Run this on another thread than the AWT event queue to
                // make sure the call to Animator.stop() completes before
                // exiting
                new Thread(new Runnable() {

                    public void run() {
                        animator.stop();
                        System.exit(0);
                    }
                }).start();
            }
        });
        // Center frame
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
        animator.start();
        canvas.requestFocus();
    }

    public void init(GLAutoDrawable drawable) {
        // Use debug pipeline
        // drawable.setGL(new DebugGL(drawable.getGL()));

        GL gl = drawable.getGL();
        gl.glClear(GL.GL_COLOR_BUFFER_BIT);
	gl.glClear(GL.GL_DEPTH_BUFFER_BIT);

        System.err.println("INIT GL IS: " + gl.getClass().getName());

        // Enable VSync
        gl.setSwapInterval(1);

        // Setup the drawing area and shading mode
        gl.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
        gl.glShadeModel(GL.GL_SMOOTH); // try setting this to GL_FLAT and see what happens.
        drawable.addKeyListener(new KeyListener());

    }

    public void reshape(GLAutoDrawable drawable, int x, int y, int width, int height) {
        GL gl = drawable.getGL();
        GLU glu = new GLU();

        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(GL.GL_PROJECTION);
        gl.glLoadIdentity();
        gl.glMatrixMode(GL.GL_MODELVIEW);

        gl.glLoadIdentity();
        glu.gluOrtho2D(0.0, 500.0, 0.0, 300.0);


    }

    public void display(GLAutoDrawable drawable) {

        GL gl = drawable.getGL();

        // Clear the drawing area
        gl.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);
        // Reset the current matrix to the "identity"
        gl.glLoadIdentity();

        gl.glColor3f(1.5f, 1.5f, 1.5f);
        gl.glPointSize(50.0f);
        gl.glBegin(GL.GL_POINTS);
            gl.glVertex2i(20, 150);
        gl.glEnd();

        
        // Flush all drawing operations to the graphics card
        gl.glFlush();
    }

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

    private class KeyListener extends KeyAdapter
    {
        public void keyPressed(KeyEvent e)
        {
            if(e.getKeyCode() == KeyEvent.VK_ESCAPE)
           {
               System.exit(0);
           }
    }

    

}