Zooming out with AffineTransform

Question

I'm trying to create a generic container panel that can zoom and pan over arbitrary JComponents. Zooming in works fine. Zooming out is getting some odd side effects from the clip. Zooming out, then resizing the window doesn't show the whole image. The top and bottom are trimmed off, despite the large space available at the top and bottom of the window.
I've overridden paintChildren() to set the Graphics' transform. mutantGraphics.setClip(mutantClip) doesn't seem to matter; the clip only gets smaller.
How do I restore the clip to the larger size?
Thanks,
Dave
   public final class ZoomPanel
        extends JPanel
        private JPanel view;
        private AffineTransform transform;
        private AffineTransform inverse;
        private static final double ZOOMINRATE = 1.1;
        private static final double ZOOMOUTRATE = 1/ZOOMINRATE;
        private Dimension originalSize;
        //todo preferred size
        ZoomPanel(JPanel view)
            super(new BorderLayout());
            add(view);
            this.view = view;
            this.originalSize = view.getPreferredSize();
            this.setPreferredSize(originalSize);
            transform = new AffineTransform();
            try
                inverse = transform.createInverse();
            catch(NoninvertibleTransformException nte)
                throw new RuntimeException(nte);
        private void transformChanged()
            try
                inverse = transform.createInverse();
            catch(NoninvertibleTransformException nte)
                throw new RuntimeException(nte);
            view.repaint();
        public void zoomOut()
            transform.translate(getWidth()/2,getHeight()/2);
            transform.scale(ZOOMOUTRATE,ZOOMOUTRATE);
            transform.translate(-getWidth()/2,-getHeight()/2);
            transformChanged();
        public void zoomIn()
            transform.translate(getWidth()/2,getHeight()/2);
            transform.scale(ZOOMINRATE,ZOOMINRATE);
            transform.translate(-getWidth()/2,-getHeight()/2);
            transformChanged();
        protected void paintChildren(Graphics originalGraphics)
            Graphics2D mutantGraphics = (Graphics2D)originalGraphics.create();
            Shape originalClip = originalGraphics.getClip();
            System.out.println("originalClip "+originalClip);
            Shape mutantClip = inverse.createTransformedShape(originalClip);
            mutantGraphics.transform(transform);
            mutantGraphics.setClip(mutantClip);
            System.out.println("mutantGraphics.getClip() "+mutantGraphics.getClip().getBounds());
            mutantGraphics.setStroke(new BasicStroke(4));
            mutantGraphics.draw(mutantGraphics.getClip().getBounds());
            super.paintChildren(mutantGraphics);
    }

Answer 1

You'll need to modify the preferred size of your component as you zoom.
Typically, I would set the component's preferred size to fit the zoomed image (ie at 0.5 zoom the width and hieght would both be double the original size) and then stuff it into a JScrollPane.
At the moment you set the preferred size initially but never change it, so your image is being clipped by the bounds of the component - it can't render outside its bounds so the component needs to be at least as large as the view.