Posted by jerron on May 24, 2011; 12:56pm
URL: https://forum.jogamp.org/display-called-repeatedly-yet-screen-not-updated-tp2979558.html

Hello.

I have the following:

--

import javax.media.opengl.GL;
import javax.media.opengl.GL2;
import javax.media.opengl.GLAutoDrawable;
import javax.media.opengl.GLCapabilities;
import javax.media.opengl.GLEventListener;
import javax.media.opengl.GLProfile;
import javax.media.opengl.fixedfunc.GLMatrixFunc;

import com.jogamp.newt.event.KeyEvent;
import com.jogamp.newt.event.KeyListener;
import com.jogamp.newt.event.WindowAdapter;
import com.jogamp.newt.event.WindowEvent;
import com.jogamp.newt.opengl.GLWindow;
import com.jogamp.opengl.util.Animator;
import com.jogamp.opengl.util.FPSAnimator;

public final class JavaGL1 implements GLEventListener, KeyListener
{
  static {
    GLProfile.initSingleton();
  }

  private static void initGL()
  {
    final GLProfile profile = GLProfile.getDefault();
    final GLCapabilities capabilities = new GLCapabilities(profile);
    final GLWindow window = GLWindow.create(capabilities);

    window.setSize(300, 300);
    window.setVisible(true);
    window.setTitle("NEWT Window Test");
    window.addWindowListener(new WindowAdapter() {
      @Override public void windowDestroyNotify(final WindowEvent arg0)
      {
        System.exit(0);
      }
    });

    final JavaGL1 test0 = new JavaGL1();
    window.addGLEventListener(test0);
    window.addKeyListener(test0);

    final Animator animator = new FPSAnimator(window, 30);
    animator.add(window);
    animator.start();
  }

  public static void main(final String[] args)
  {
    JavaGL1.initGL();
  }

  @Override public void dispose(final GLAutoDrawable drawable)
  {
    System.out.println("info: dispose");
  }

  @Override public void init(final GLAutoDrawable drawable)
  {
    System.out.println("info: init");
  }

  private void perspective (final GL2 gl, double width, double height, double fov_y, double z_near, double z_far)
  {
    final double aspect_ratio = width / height;
    final double fr_height = Math.tan(fov_y / 360 * Math.PI) * z_near;
    final double fr_width = fr_height * aspect_ratio;
    gl.glFrustum(-fr_width, fr_width, -fr_height, fr_height, z_near, z_far);
  }
 
  int screen_width = 0;
  int screen_height = 0;
 
  private float cam_pos_x = 0.0f;
  private float cam_pos_y = 0.0f;
  private float cam_pos_z = -50.0f;

  private void location()
  {
    System.out.println("info: location: x: " + this.cam_pos_x + " y: " + this.cam_pos_y + " z: " + this.cam_pos_z);
  }

  private void render(final GL2 gl)
  {
    System.out.println("info: render");
   
    gl.glMatrixMode(GLMatrixFunc.GL_PROJECTION);
    gl.glLoadIdentity();
    this.perspective(gl, this.screen_width, this.screen_height, 45.0, 0.1, 100.0);
   
    gl.glMatrixMode(GLMatrixFunc.GL_MODELVIEW);
    gl.glLoadIdentity();

    gl.glClearColor(0.0f, 0.0f, 1.0f, 1.0f);
    gl.glClear(GL.GL_COLOR_BUFFER_BIT);

    gl.glTranslatef(0.0f, 0.0f, -50.f);
    gl.glColor3f((float) Math.random(), (float) Math.random(), (float) Math.random());
    gl.glBegin(GL.GL_TRIANGLES);
    gl.glVertex3f(this.cam_pos_x, this.cam_pos_y, 0.0f);
    gl.glVertex3f(this.cam_pos_x, this.cam_pos_y + 20.f, 0.0f);
    gl.glVertex3f(this.cam_pos_x + 20.f, this.cam_pos_y, 0.0f);
    gl.glEnd();
  }

  @Override public void display(final GLAutoDrawable drawable)
  {
    final GL2 gl = drawable.getGL().getGL2();
    this.render(gl);
  }

  @Override public void reshape(final GLAutoDrawable drawable,
                                final int x,
                                final int y,
                                final int width,
                                final int height)
  {
    System.out.println("info: resize " + x + "," + y + "+" + width + "x" + height);
   
    this.screen_width = width;
    this.screen_height = height;
   
    final GL2 gl = drawable.getGL().getGL2();
    gl.glViewport(0, 0, width, height);
  }

  @Override public void keyPressed(final KeyEvent arg0)
  {
    // Nothing.
  }

  @Override public void keyReleased(final KeyEvent event)
  {
    System.out.println("info: key " + event.getKeyChar());

    switch (event.getKeyChar()) {
      case 'w':
        this.cam_pos_z += 10.0f;
        break;
      case 's':
        this.cam_pos_z -= 10.0f;
        break;
      case 'a':
        this.cam_pos_x += 10.0f;
        break;
      case 'd':
        this.cam_pos_x -= 10.0f;
        break;
      case 'f':
        this.cam_pos_y += 10.0f;
        break;
      case 'v':
        this.cam_pos_y -= 10.0f;
        break;
      default:
        break;
    }

    this.location();
  }

  @Override public void keyTyped(final KeyEvent arg0)
  {
    // Nothing.
  }
}

--

Running this program, I'd expect to see a triangle onscreen changing color at random.

Instead, the triangle appears but the screen never seems to be updated after that. Adding
TraceGL or just some simple print statements shows that display() is called repeatedly but
it apparently has no effect. Any idea what might be going on?