Index: core/startup/src/org/netbeans/core/startup/layers/SystemFileSystem.java
===================================================================
RCS file: /cvs/core/startup/src/org/netbeans/core/startup/layers/SystemFileSystem.java,v
retrieving revision 1.1
diff -u -r1.1 SystemFileSystem.java
--- core/startup/src/org/netbeans/core/startup/layers/SystemFileSystem.java	4 Jun 2005 05:11:59 -0000	1.1
+++ core/startup/src/org/netbeans/core/startup/layers/SystemFileSystem.java	20 Oct 2005 07:31:29 -0000
@@ -34,7 +34,8 @@
 *
 * @author Jan Jancura, Ian Formanek, Petr Hamernik
 */
-public final class SystemFileSystem extends MultiFileSystem implements FileSystem.Status {
+public final class SystemFileSystem extends MultiFileSystem 
+implements FileSystem.Status, org.openide.util.LookupListener {
     // Must be public for BeanInfo to work: #11186.
 
     /** generated Serialized Version UID */
@@ -55,6 +56,11 @@
     /** name of file attribute with URL to 32x32 color icon */
     private static final String ATTR_ICON_32 = "SystemFileSystem.icon32"; // NOI18N
 
+    /** lookup result we listen on */
+    private static Lookup.Result result = Lookup.getDefault ().lookup (new Lookup.Template (FileSystem.class));
+    /** the set of layers provided by the system */
+    private static FileSystem[] layers;
+
     /** user fs */
     private ModuleLayeredFileSystem user;
     /** home fs */
@@ -67,13 +73,15 @@
 
     /** @param fss list of file systems to delegate to
     */
-    private SystemFileSystem (FileSystem[] fss) throws PropertyVetoException {
-        super (fss);
-        user = (ModuleLayeredFileSystem) fss[0];
-        home = fss.length > 2 ? (ModuleLayeredFileSystem) fss[1] : null;
+    private SystemFileSystem () throws PropertyVetoException {
+        super (computeLayers ());
+        user = (ModuleLayeredFileSystem) layers[0];
+        home = layers.length > 2 ? (ModuleLayeredFileSystem) layers[1] : null;
 
         setSystemName (SYSTEM_NAME);
         setHidden (true);
+        
+        result.addLookupListener (this);
     }
 
 
@@ -107,8 +115,9 @@
             else
                 s.add (arr[i]);
 
+        layers = (FileSystem []) arr.clone ();
         // create own internal copy of passed filesystems
-        setDelegates ((FileSystem []) arr.clone ());
+        setDelegates (computeLayers ());
         firePropertyChange ("layers", null, null); // NOI18N
     }
     
@@ -121,6 +130,19 @@
         // don't return reference to internal buffer
         return (FileSystem []) getDelegates ().clone ();
     }
+    
+    private synchronized static FileSystem[] computeLayers () {
+        FileSystem[] fromLookup = (FileSystem[])result.allInstances ().toArray (new FileSystem[0]);
+        
+        if (fromLookup.length > 0) {
+            ArrayList arr = new ArrayList (layers.length + fromLookup.length);
+            arr.addAll (Arrays.asList (layers));
+            arr.addAll (Arrays.asList (fromLookup));
+            return (FileSystem[])arr.toArray (new FileSystem[0]);
+        }
+        
+        return layers;
+    }
 
     protected FileSystem createWritableOnForRename (String oldName, String newName) throws IOException {        
         return createWritableOn (oldName);
@@ -318,7 +340,8 @@
             ("org.netbeans.core.projects.FixedFileSystem", "Automatic Manifest Installation"); // NOI18N
         arr[home == null ? 1 : 2] = FixedFileSystem.deflt;
 
-        return new SystemFileSystem (arr);
+        layers = arr;
+        return new SystemFileSystem ();
     }
 
     /** Getter for message.
@@ -357,6 +380,12 @@
         new NotSerializableException ("WARNING - SystemFileSystem is not designed to be serialized").printStackTrace (); // NOI18N
         return new SingletonSerializer ();
     }
+    
+    /** Refresh layers */
+    public synchronized void resultChanged (org.openide.util.LookupEvent ev) {
+        setDelegates (computeLayers ());
+    }
+    
     private static final class SingletonSerializer extends Object implements Serializable {
         private static final long serialVersionUID = 6436781994611L;
         SingletonSerializer() {}
Index: core/test/unit/src/org/netbeans/core/projects/SystemFileSystemTest.java
===================================================================
RCS file: /cvs/core/test/unit/src/org/netbeans/core/projects/SystemFileSystemTest.java,v
retrieving revision 1.4
diff -u -r1.4 SystemFileSystemTest.java
--- core/test/unit/src/org/netbeans/core/projects/SystemFileSystemTest.java	4 Jun 2005 05:15:56 -0000	1.4
+++ core/test/unit/src/org/netbeans/core/projects/SystemFileSystemTest.java	20 Oct 2005 07:31:29 -0000
@@ -89,6 +89,21 @@
         assertEquals("correct localized data object name", "Localized Name", n.getDisplayName());
     }
     
+    public void testContentOfFileSystemIsInfluencedByLookup () throws Exception {
+        MemoryFileSystem mem = new MemoryFileSystem ();
+        String dir = "/yarda/own/file";
+        org.openide.filesystems.FileUtil.createFolder (mem.getRoot (), dir);
+        
+        assertNull ("File is not there yet", Repository.getDefault ().getDefaultFileSystem ().findResource (dir));
+        NbTopManager.get().register (mem);
+        try {
+            assertNotNull ("The file is there now", Repository.getDefault ().getDefaultFileSystem ().findResource (dir));
+        } finally {
+            NbTopManager.get().unregister (mem);
+        }
+        assertNull ("File is no longer there", Repository.getDefault ().getDefaultFileSystem ().findResource (dir));
+    }
+    
     public void testIconFromURL() throws Exception {
         FileObject bar = Repository.getDefault().getDefaultFileSystem().findResource("foo/bar.txt");
         Node n = DataObject.find(bar).getNodeDelegate();