Open Favorites tab on first project or file open

platform/favorites/src/org/netbeans/modules/favorites/Module.java

@@ -18,30 +18,45 @@
  */
 package org.netbeans.modules.favorites;
 
+import java.beans.PropertyChangeEvent;
+import java.beans.PropertyChangeListener;
 import java.io.File;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 import java.util.function.Function;
+import java.util.prefs.Preferences;
+import javax.swing.SwingUtilities;
 import javax.swing.UIManager;
 import org.netbeans.modules.favorites.api.Favorites;
 import org.netbeans.swing.plaf.LFCustoms;
 import org.openide.filesystems.FileObject;
 import org.openide.filesystems.FileUtil;
+import org.openide.util.NbPreferences;
+import org.openide.windows.Mode;
 import org.openide.windows.OnShowing;
+import org.openide.windows.WindowManager;
 
 /**
  * For lifecycle tasks.
  * @author mbien
  */
 public final class Module {
 
+    private static final String INITIAL_OPEN_DONE_KEY = "initial-open-done"; //NOI18N
+
     private Module() {}
 
     @OnShowing
     public final static class EDTInit implements Runnable {
+
         @Override
         public void run() {
+            registerFavAppenderFunction();
+            attachFirstEditorOpenListener();
+        }
+
+        private void registerFavAppenderFunction() {
             Function<File[], File[]> favAppender = (files) -> {
                 if (!UIManager.getBoolean(LFCustoms.FILECHOOSER_FAVORITES_ENABLED)) {
                     return files;
@@ -53,10 +68,40 @@ public void run() {
                         shortcuts.add(file);
                     }
                 }
-                return shortcuts.toArray(new File[0]);
+                return shortcuts.toArray(File[]::new);
             };
             UIManager.put(LFCustoms.FILECHOOSER_SHORTCUTS_FILESFUNCTION, favAppender);
         }
+
+        // very first on-editor-open event will also open the Favorites tab 
+        private void attachFirstEditorOpenListener() {
+            Preferences prefs = NbPreferences.forModule(Module.class);
+            if (prefs.getBoolean(INITIAL_OPEN_DONE_KEY, false)) {
+                return;
+            }
+            WindowManager wm = WindowManager.getDefault();
+            wm.addPropertyChangeListener(new PropertyChangeListener() {
+                @Override
+                public void propertyChange(PropertyChangeEvent evt) {
+                    if ("activeMode".equals(evt.getPropertyName())   //NOI18N
+                            && evt.getNewValue() instanceof Mode mode
+                            && wm.isEditorMode(mode)) {
+                        try {
+                            Tab favTab = Tab.findDefault();
+                            if (favTab != null && !favTab.wasOpened() && !favTab.isOpened()) {
+                                favTab.open();
+                            }
+                        } finally {
+                            prefs.putBoolean(INITIAL_OPEN_DONE_KEY, true);
+                            PropertyChangeListener thisListener = this;
+                            SwingUtilities.invokeLater(() -> {
+                                wm.removePropertyChangeListener(thisListener);
+                            });
+                        }
+                    }
+                }
+            });
+        }
     }
-    
+
 }

platform/favorites/src/org/netbeans/modules/favorites/Tab.java

@@ -139,6 +139,11 @@ protected void componentShowing () {
         run();
     }
 
+    /// true if this tab has been opened during this session
+    boolean wasOpened() {
+        return view != null;
+    }
+
     /** Initializes gui of this component. Subclasses can override
     * this method to install their own gui.
     * @return Tree view that will serve as main view for this explorer.

platform/favorites/src/org/netbeans/modules/favorites/resources/favorites.wstcgrp

@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+    Licensed to the Apache Software Foundation (ASF) under one
+    or more contributor license agreements.  See the NOTICE file
+    distributed with this work for additional information
+    regarding copyright ownership.  The ASF licenses this file
+    to you under the Apache License, Version 2.0 (the
+    "License"); you may not use this file except in compliance
+    with the License.  You may obtain a copy of the License at
+
+      http://www.apache.org/licenses/LICENSE-2.0
+
+    Unless required by applicable law or agreed to in writing,
+    software distributed under the License is distributed on an
+    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+    KIND, either express or implied.  See the License for the
+    specific language governing permissions and limitations
+    under the License.
+
+-->
+
+<tc-group version="2.0">
+    <module name="org.netbeans.core.ide/1" spec="1.13" />
+    <tc-id id="favorites" />
+    <open-close-behavior open="true" close="false"/>
+</tc-group>

platform/favorites/src/org/netbeans/modules/favorites/resources/layer.xml

@@ -21,6 +21,7 @@
 -->
 <!DOCTYPE filesystem PUBLIC "-//NetBeans//DTD Filesystem 1.2//EN" "http://www.netbeans.org/dtds/filesystem-1_2.dtd">
 <filesystem>
+
     <folder name="Favorites">
         <attr name="SystemFileSystem.localizingBundle" stringvalue="org.netbeans.modules.favorites.Bundle"/>
         <file name="Home.shadow">
@@ -38,4 +39,13 @@
             </file>
         </folder>
     </folder>
+
+    <folder name="Windows2">
+        <folder name="Groups">
+            <folder name="OpenedProjects">
+                <file name="favorites.wstcgrp" url="favorites.wstcgrp"/>
+            </folder>
+        </folder>
+    </folder>
+
 </filesystem>