Created attachment 362 [details]
Test code

Overview: On Mac OS X, the use of the accumulation buffer flips the resulting image vertically. This behavior happens both for pBuffer and GLCanvas.

Steps to Reproduce: See bottom of post and attached file.

Build Date & Platform: JOGL v2.0-RC9, MacBook Pro 6.1, GeForce GT 300M, Mac OS X 10.6.8, Java 6u33

Additional Builds and Platforms: The vertical flip does not occur on any Windows machine so far. Also, another Mac (Mac OS X 10.7, Oracle Java 7u5) doesn't have the problem.

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import java.awt.image.BufferedImage;

import javax.media.opengl.GL2;
import javax.media.opengl.GLAutoDrawable;
import javax.media.opengl.GLCapabilities;
import javax.media.opengl.GLDrawableFactory;
import javax.media.opengl.GLEventListener;
import javax.media.opengl.GLException;
import javax.media.opengl.GLPbuffer;
import javax.media.opengl.GLProfile;

import com.jogamp.opengl.util.awt.Screenshot;


public class FlippedImageTest implements GLEventListener {

    GLPbuffer glPBuffer = null;

	public FlippedImageTest() {
	        
		GLProfile glp = GLProfile.get(GLProfile.GL2);
		GLCapabilities caps = new GLCapabilities(glp);
		GLDrawableFactory glFactory = GLDrawableFactory.getFactory(glp);
		caps.setAccumRedBits(16);
		caps.setAccumGreenBits(16);
		caps.setAccumBlueBits(16);
		caps.setStencilBits(8);
		caps.setDoubleBuffered(true);
		caps.setHardwareAccelerated(true);
	       
        try {
        	glPBuffer = glFactory.createGLPbuffer(null, caps, null, 4, 4, null);
        } catch (GLException exc) {	            
        }

 
        glPBuffer.addGLEventListener(this);
	}
	
	
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		FlippedImageTest demo = new FlippedImageTest();
        
        demo.glPBuffer.display();
        demo.glPBuffer.createContext(null).makeCurrent();
        BufferedImage image = Screenshot.readToBufferedImage(4, 4);
        
        int above = image.getRGB(0, 0);
        int below = image.getRGB(0, 3);

        if (above == 0xff00ff00 && below == 0xffff0000) {
            System.out.println("image right side up");
        } else if (above == 0xffff0000 && below == 0xff00ff00) {
        	System.out.println("image is flipped");
        } else {
        	System.out.println("error in test");
        }

	}
	
	public void display(GLAutoDrawable drawable) {
		GL2 gl = drawable.getGL().getGL2();
        gl.glMatrixMode(GL2.GL_PROJECTION);
        gl.glLoadIdentity();
        gl.glMatrixMode(GL2.GL_MODELVIEW);
        gl.glLoadIdentity();

        // red below
        gl.glColor3f(1, 0, 0);
        gl.glRectf(-1, -1, 1, 0);

        // green above
        gl.glColor3f(0, 1, 0);
        gl.glRectf(-1, 0, 1, 1);
        gl.glFinish();

        gl.glAccum(GL2.GL_ACCUM, 1.0f);
        gl.glAccum(GL2.GL_RETURN, 1.0f);

		gl.glEnd();
		gl.glFlush();
	}
 
	public void init(GLAutoDrawable drawable) {
	}
 
	public void reshape(GLAutoDrawable glDrawable, int x, int y, int w, int h) {
	}

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

	public void dispose(GLAutoDrawable drawable) {
	}

}