import java.lang.reflect.InvocationHandler;

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Proxy;

import java.awt.*;

    private JCBRender cellRender = null;

        if (cellRender == null && topComponent != null) {

            //System.out.println("##create renderer for: " + (topComponent==null?"warmup":topComponent.getDisplayName()));

            cellRender = new JCBRender();

            cellRender.addNotify();

        }

    }

    private class JCBRender implements InvocationHandler {

        private final ListCellRenderer orig;

        private boolean isHackable = true;

        private boolean isThin = false;

        private JPopupMenu popup;

        private JList list;

        private int height = 0;

        private int width;

        private Component comp;

        private final JComboBox comboToHack;

        private boolean debug = false;

        public JCBRender() {

            this.comboToHack = NavigationView.this;

            this.orig = comboToHack.getRenderer();

            this.width = comboToHack.getWidth();

        }

        public void addNotify() {

            if (comboToHack.getRenderer() == orig) {

                comboToHack.setRenderer(getProxy());

                this.width = comboToHack.getWidth();

            }

        }

        public void removeNotify() {

            comboToHack.setRenderer(orig);

        }

        private int lastMaxWidth;

        private boolean isReshaped = false;

        private boolean isFirstRun = true;

        public void processListCellRendererComponent(JList list, Object value, int index, Component comp) {

            if (index < 0) return;

            if (index == 0) {

                popup = findPopupMenu(list);

                this.list = list;

                if (popup == null) {

                    //System.out.println("## is not hackable: " + this);

                    isHackable = false;

                    return;

                }

                height = 0;

                if (isReshaped) {

                    this.lastMaxWidth = this.width;

                    isReshaped = false;

                }

                this.width = comboToHack.getWidth();

                if (lastMaxWidth < width) lastMaxWidth = width;

            }

            Dimension size = comp.getPreferredSize();

            height += size.height;

            if (width < size.width) {

                width = size.width;

                this.comp = comp;

                isThin = true;

            }

            //System.out.println("##process: idx:"+index+",last:" + lastMaxWidth + ",curr:" + width + ",size:"+size.width + ",isThin:" + isThin + ",model:"+(list.getModel().getSize() - 1)+", @" + System.identityHashCode(this));

            if (isThin && index == list.getModel().getSize() - 1 && width != lastMaxWidth ||

                    isFirstRun && index == list.getModel().getSize() - 1) {

                isReshaped = true;

                isThin = false;

                isFirstRun = false;

                reshapePopup();

                height = 0;

            }

        }

        public Object invoke(Object proxy, java.lang.reflect.Method method, Object[] args) throws Throwable {

            Object res = null;

            try {

                res = method.invoke(orig, args);

                if (isHackable && "getListCellRendererComponent".equals(method.getName())) {

                    Component c = (Component) res;

                    JList l = (JList) args[0];

                    Object value = args[1];

                    int index = ((Integer) args[2]).intValue();

                    processListCellRendererComponent(l, value, index, c);

                }

            } catch (IllegalArgumentException ex) {

                ex.printStackTrace();

            } catch (InvocationTargetException ex) {

                Throwable t = ex.getCause();

                if (t != null) throw t;

                else ex.printStackTrace();

            }

            return res;

        }

        void reshapePopup() {

            int preferredWidth = Math.min(width + 20, getMaxWidth());

            int prefferedHeight = Math.min(height, getMaxHeight());

            //System.out.println("revalidate: w: " + preferredWidth + ", h: " +prefferedHeight + ", @" + System.identityHashCode(this) + ", AWT: " +EventQueue.isDispatchThread());

            this.comp = null;

            popup.removeAll();

            scroller.remove(list);

            popup.setPopupSize(preferredWidth, prefferedHeight);

            popup.add(createScroller());

            popup.revalidate();

            popup.repaint();

        }

        private JScrollPane scroller;

        private JPopupMenu findPopupMenu(Component c) {

            Component parent = c;

            Component previous = c;

            while (parent != null && !(parent instanceof JPopupMenu)) {

                previous = parent;

                parent = parent.getParent();

            }

            if (previous instanceof JScrollPane) {

                scroller = (JScrollPane) previous;

            } else {

                parent = null; // unsupported component hierarchy

            }

            return (JPopupMenu) parent;

        }

        /**

         * Creates the scroll pane which houses the scrollable list.

         */

        private JScrollPane createScroller() {

            JScrollPane scroller = new JScrollPane(list, 

                            ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED,

                            ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);

            scroller.setFocusable(false);

            scroller.getVerticalScrollBar().setFocusable(false);

            scroller.setBorder(null);

            return scroller;

        }

        private int maxWidth = -1;

        private int maxHeight = -1;

        private int getMaxWidth() {

            TopComponent tc = NavigationView.this.findParentTopComponent();

            if (tc != null) {

                maxWidth = tc.getX() + tc.getWidth() - comboToHack.getX();

            } else {

                maxWidth = Toolkit.getDefaultToolkit().getScreenSize().width >> 1;

            }

            return maxWidth;

        }

        private int getMaxHeight() {

            TopComponent tc = NavigationView.this.findParentTopComponent();

            if (tc != null) {

                maxHeight = tc.getY() + tc.getHeight() - comboToHack.getY() - comboToHack.getHeight();

            } else {

                maxHeight = Toolkit.getDefaultToolkit().getScreenSize().height >> 1;

            }

            return maxHeight;

        }

        public ListCellRenderer getProxy() {

            return (ListCellRenderer) Proxy.newProxyInstance(

                    this.getClass().getClassLoader(), new Class[] {ListCellRenderer.class}, this);

        }