Index: src/org/openide/WizardDescriptor.java
===================================================================
RCS file: /cvs/openide/src/org/openide/WizardDescriptor.java,v
retrieving revision 1.89
diff -u -r1.89 WizardDescriptor.java
--- src/org/openide/WizardDescriptor.java	21 Aug 2003 08:57:36 -0000	1.89
+++ src/org/openide/WizardDescriptor.java	11 Nov 2003 18:27:56 -0000
@@ -1002,6 +1002,20 @@
     public interface FinishPanel extends Panel {
     }
 
+    /** A special interface for panels that need to do additional
+     * validation when Next or Finish button is clicked.
+     */
+    public interface ValidatingPanel extends Panel {
+        /** Is called when Next of Finish buttons are clicked and 
+         * allows deeper check to find out that panel is in valid 
+         * state and it is ok to leave it.
+         *
+         * @return null if everything is ok or a localized message to show to
+         *   user
+         */
+        public String validate ();
+    }
+    
     /** Special iterator that works on an array of <code>Panel</code>s.
     */
     public static class ArrayIterator extends Object implements Iterator {
@@ -1111,6 +1125,20 @@
         public void actionPerformed (ActionEvent ev) {
             if (ev.getSource () == nextButton) {
                 Dimension previousSize = panels.current().getComponent().getSize();
+                
+                if (panels.current() instanceof ValidatingPanel) {
+                    ValidatingPanel v = (ValidatingPanel)panels.current ();
+                    String msg = v.validate();
+                    if ("xtest-fail-without-msg".equals (msg)) {
+                        return;
+                    }
+                    
+                    if (msg != null) {
+                        DialogDisplayer.getDefault().notify(new NotifyDescriptor.Message(msg));
+                        return;
+                    }
+                }
+                
                 panels.nextPanel ();
                 try {
                     // change UI to show next step, show wait cursor during
@@ -1140,6 +1168,19 @@
             }
 
             if (ev.getSource () == finishButton) {
+                if (panels.current() instanceof ValidatingPanel) {
+                    ValidatingPanel v = (ValidatingPanel)panels.current ();
+                    String msg = v.validate();
+                    if ("xtest-fail-without-msg".equals (msg)) {
+                        return;
+                    }
+                    
+                    if (msg != null) {
+                        DialogDisplayer.getDefault().notify(new NotifyDescriptor.Message(msg));
+                        return;
+                    }
+                }
+                
                 Object oldValue = getValue ();
                 setValueWithoutPCH (OK_OPTION);
                 if (Arrays.asList(getClosingOptions()).contains(finishButton)) {
Index: test/unit/src/org/openide/WizardDescTest.java
===================================================================
RCS file: /cvs/openide/test/unit/src/org/openide/WizardDescTest.java,v
retrieving revision 1.2
diff -u -r1.2 WizardDescTest.java
--- test/unit/src/org/openide/WizardDescTest.java	21 Aug 2003 12:45:49 -0000	1.2
+++ test/unit/src/org/openide/WizardDescTest.java	11 Nov 2003 18:28:02 -0000
@@ -102,16 +102,66 @@
         assertEquals ("Closed with cancel option.", WizardDescriptor.CANCEL_OPTION, wd.getValue ());
     }
 
+    public void testNextOptionWhenLazyValidationFails () throws Exception {
+        Panel panels[] = new Panel[3];
+        
+        class MyPanel extends Panel implements WizardDescriptor.ValidatingPanel {
+            public String validateMsg;
+            
+            public MyPanel () {
+                super ("enhanced panel");
+            }
+            
+            public String validate () {
+                return validateMsg;
+            }
+        }
+        
+        class MyFinishPanel extends MyPanel implements WizardDescriptor.FinishPanel {
+        }
+        
+        MyPanel mp = new MyPanel ();
+        MyFinishPanel mfp = new MyFinishPanel ();
+        panels[0] = mp;
+        panels[1] = mfp;
+        panels[2] = new Panel ("Last one");
+        wd = new WizardDescriptor(panels);
+        
+        assertNull ("Component has not been yet initialized", panels[1].component);
+        mp.validateMsg = "xtest-fail-without-msg";
+        wd.doNextClick ();
+        assertNull ("The lazy validation failed, still no initialiaation", panels[1].component);
+        assertNull ("The lazy validation failed, still no initialiaation", panels[2].component);
+        mp.validateMsg = null;
+        wd.doNextClick ();
+        assertNotNull ("Now we switched to another panel", panels[1].component);
+        assertNull ("The lazy validation failed, still no initialiaation", panels[2].component);
+        
+        // remember previous state
+        Object state = wd.getValue();
+        mfp.validateMsg = "xtest-fail-without-msg";
+        wd.doFinishClick();
+        assertNull ("The validation failed, still no initialiaation", panels[2].component);
+        assertEquals ("State has not changed", state, wd.getValue ());
+        
+        mfp.validateMsg = null;
+        wd.doFinishClick ();
+        assertNull ("Finish was clicked, no initialization either", panels[2].component);
+        assertEquals ("The state is finish", WizardDescriptor.FINISH_OPTION, wd.getValue ());
+    }
     
     public class Panel implements WizardDescriptor.Panel, WizardDescriptor.FinishPanel {
-
+        private JLabel component;
         private String text;
         public Panel(String text) {
             this.text = text;
         }
         
         public Component getComponent() {
-            return new JLabel(text);
+            if (component == null) {
+                component = new JLabel (text);
+            }
+            return component;
         }
         
         public void addChangeListener(ChangeListener l) {