gt:             if (panes == null) return null;
context: /*
   * Copyright (c) 2011, 2015, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  package com.sun.javafx.scene.control.behavior;
  
  import javafx.beans.property.ReadOnlyBooleanProperty;
  import javafx.beans.value.ChangeListener;
  import javafx.beans.value.ObservableValue;
  import javafx.collections.ListChangeListener;
  import javafx.collections.ObservableList;
  import javafx.scene.control.Accordion;
  import javafx.scene.control.FocusModel;
  import javafx.scene.control.TitledPane;
  import com.sun.javafx.scene.control.inputmap.InputMap;
  import com.sun.javafx.scene.control.inputmap.KeyBinding;
  import javafx.scene.input.KeyEvent;
  import javafx.scene.input.MouseEvent;
  
  import static javafx.scene.input.KeyCode.*;
  
  public class AccordionBehavior extends BehaviorBase<Accordion> {
  
      private final InputMap<Accordion> inputMap;
      private AccordionFocusModel focusModel;
  
      public AccordionBehavior(Accordion accordion) {
          super(accordion);
          focusModel = new AccordionFocusModel(accordion);
  
          // create a map for accordion-specific mappings (this reuses the default
          // InputMap installed on the control, if it is non-null, allowing us to pick up any user-specified mappings)
          inputMap = createInputMap();
  
          // accordion-specific mappings for key and mouse input
          addDefaultMapping(inputMap,
                  new InputMap.KeyMapping(UP, e -> pageUp(false)),
                  new InputMap.KeyMapping(DOWN, e -> pageDown(false)),
                  new InputMap.KeyMapping(LEFT, e -> {
                      if (isRTL(accordion)) pageDown(false);
                      else pageUp(false);
                  }),
                  new InputMap.KeyMapping(RIGHT, e -> {
                      if (isRTL(accordion)) pageUp(false);
                      else pageDown(false);
                  }),
                  new InputMap.KeyMapping(HOME, this::home),
                  new InputMap.KeyMapping(END, this::end),
                  new InputMap.KeyMapping(PAGE_UP, e -> pageUp(true)),
                  new InputMap.KeyMapping(PAGE_DOWN, e -> pageDown(true)),
                  new InputMap.KeyMapping(new KeyBinding(PAGE_UP).ctrl(), this::moveBackward),
                  new InputMap.KeyMapping(new KeyBinding(PAGE_DOWN).ctrl(), this::moveForward),
                  new InputMap.KeyMapping(new KeyBinding(TAB).ctrl(), this::moveForward),
                  new InputMap.KeyMapping(new KeyBinding(TAB).ctrl().shift(), this::moveBackward),
                  new InputMap.MouseMapping(MouseEvent.MOUSE_PRESSED, this::mousePressed)
          );
      }
  
      @Override public void dispose() {
          focusModel.dispose();
          super.dispose();
      }
  
      @Override public InputMap<Accordion> getInputMap() {
          return inputMap;
      }
  
      /***************************************************************************
       *                                                                         *
       * Key event handling                                                      *
       *                                                                         *
       **************************************************************************/
  
  //    private static final String HOME = "Home";
  //    private static final String END = "End";
  //    private static final String PAGE_UP = "Page_Up";
  //    private static final String PAGE_DOWN = "Page_Down";
  //    private static final String CTRL_PAGE_UP = "Ctrl_Page_Up";
  //    private static final String CTRL_PAGE_DOWN = "Ctrl_Page_Down";
  //    private static final String CTRL_TAB = "Ctrl_Tab";
  //    private static final String CTRL_SHIFT_TAB = "Ctrl_Shift_Tab";
  //
  //    protected static final List<KeyBinding> ACCORDION_BINDINGS = new ArrayList<KeyBinding>();
  //    static {
  //        ACCORDION_BINDINGS.add(new KeyBinding(KeyCode.UP, "TraverseUp"));
  //        ACCORDION_BINDINGS.add(new KeyBinding(KeyCode.DOWN, "TraverseDown"));
  //        ACCORDION_BINDINGS.add(new KeyBinding(KeyCode.LEFT, "TraverseLeft"));
  //        ACCORDION_BINDINGS.add(new KeyBinding(KeyCode.RIGHT, "TraverseRight"));
  //        ACCORDION_BINDINGS.add(new KeyBinding(KeyCode.HOME, HOME));
  //        ACCORDION_BINDINGS.add(new KeyBinding(KeyCode.END, END));
  //        ACCORDION_BINDINGS.add(new KeyBinding(KeyCode.PAGE_UP, PAGE_UP));
  //        ACCORDION_BINDINGS.add(new KeyBinding(KeyCode.PAGE_DOWN, PAGE_DOWN));
  //        ACCORDION_BINDINGS.add(new KeyBinding(KeyCode.PAGE_UP, CTRL_PAGE_UP).ctrl());
  //        ACCORDION_BINDINGS.add(new KeyBinding(KeyCode.PAGE_DOWN, CTRL_PAGE_DOWN).ctrl());
  //        ACCORDION_BINDINGS.add(new KeyBinding(KeyCode.TAB, CTRL_TAB).ctrl());
  //        ACCORDION_BINDINGS.add(new KeyBinding(KeyCode.TAB, CTRL_SHIFT_TAB).shift().ctrl());
  //    }
  
  //    @Override protected void callAction(String name) {
  //        Accordion accordion = getNode();
  //        boolean rtl = (accordion.getEffectiveNodeOrientation() == NodeOrientation.RIGHT_TO_LEFT);
  //
  //        if (("TraverseLeft".equals(name) && !rtl) ||
  //            ("TraverseRight".equals(name) && rtl) ||
  //            "TraverseUp".equals(name) ||
  //                PAGE_UP.equals(name)) {
  //
  //            if (focusModel.getFocusedIndex() != -1 && accordion.getPanes().get(focusModel.getFocusedIndex()).isFocused()) {
  //                focusModel.focusPrevious();
  //                int next = focusModel.getFocusedIndex();
  //                accordion.getPanes().get(next).requestFocus();
  //                if (PAGE_UP.equals(name)) {
  //                    accordion.getPanes().get(next).setExpanded(true);
  //                }
  //            }
  //        } else if (("TraverseRight".equals(name) && !rtl) ||
  //                   ("TraverseLeft".equals(name) && rtl) ||
  //                   "TraverseDown".equals(name) ||
  //                PAGE_DOWN.equals(name)) {
  //
  //            if (focusModel.getFocusedIndex() != -1 && accordion.getPanes().get(focusModel.getFocusedIndex()).isFocused()) {
  //                focusModel.focusNext();
  //                int next = focusModel.getFocusedIndex();
  //                accordion.getPanes().get(next).requestFocus();
  //                if (PAGE_DOWN.equals(name)) {
  //                    accordion.getPanes().get(next).setExpanded(true);
  //                }
  //            }
  //        } else if (CTRL_TAB.equals(name) || CTRL_PAGE_DOWN.equals(name)) {
  ////            moveForward();
  //        } else if (CTRL_SHIFT_TAB.equals(name) || CTRL_PAGE_UP.equals(name)) {
  ////            moveBackward();
  //        } else if (HOME.equals(name)) {
  ////            home();
  //        } else if (END.equals(name)) {
  ////            end();
  //        } else {
  //            super.callAction(name);
  //        }
  //    }
  
      private void pageUp(boolean doExpand) {
          Accordion accordion = getNode();
          if (focusModel.getFocusedIndex() != -1 && accordion.getPanes().get(focusModel.getFocusedIndex()).isFocused()) {
              focusModel.focusPrevious();
              int next = focusModel.getFocusedIndex();
              accordion.getPanes().get(next).requestFocus();
              if (doExpand) {
                  accordion.getPanes().get(next).setExpanded(true);
              }
          }
      }
  
      private void pageDown(boolean doExpand) {
          Accordion accordion = getNode();
          if (focusModel.getFocusedIndex() != -1 && accordion.getPanes().get(focusModel.getFocusedIndex()).isFocused()) {
              focusModel.focusNext();
              int next = focusModel.getFocusedIndex();
              accordion.getPanes().get(next).requestFocus();
              if (doExpand) {
                  accordion.getPanes().get(next).setExpanded(true);
              }
          }
      }
  
      private void moveBackward(KeyEvent e) {
          Accordion accordion = getNode();
          focusModel.focusPrevious();
          if (focusModel.getFocusedIndex() != -1) {
              int next = focusModel.getFocusedIndex();
              accordion.getPanes().get(next).requestFocus();
              accordion.getPanes().get(next).setExpanded(true);
          }
      }
  
      private void moveForward(KeyEvent e) {
          Accordion accordion = getNode();
          focusModel.focusNext();
          if (focusModel.getFocusedIndex() != -1) {
              int next = focusModel.getFocusedIndex();
              accordion.getPanes().get(next).requestFocus();
              accordion.getPanes().get(next).setExpanded(true);
          }
      }
  
      private void home(KeyEvent e) {
          Accordion accordion = getNode();
          if (focusModel.getFocusedIndex() != -1 && accordion.getPanes().get(focusModel.getFocusedIndex()).isFocused()) {
              TitledPane tp = accordion.getPanes().get(0);
              tp.requestFocus();
              tp.setExpanded(!tp.isExpanded());
          }
      }
  
      private void end(KeyEvent e) {
          Accordion accordion = getNode();
          if (focusModel.getFocusedIndex() != -1 && accordion.getPanes().get(focusModel.getFocusedIndex()).isFocused()) {
              TitledPane tp = accordion.getPanes().get(accordion.getPanes().size() - 1);
              tp.requestFocus();
              tp.setExpanded(!tp.isExpanded());
          }
      }
  
  
      /**
       * Mouse press over the background of the accordion
       * i.e. it missed all of the titled panes
       * select the last titled pane, or the accordion if
       * none present
       */
      public void mousePressed(MouseEvent e) {
          Accordion accordion = getNode();
          if (accordion.getPanes().size() > 0) {
              TitledPane lastTitledPane = accordion.getPanes().get(accordion.getPanes().size() - 1);
              lastTitledPane.requestFocus();
          }
          else {
              accordion.requestFocus();
          }
      }
  
  
      static class AccordionFocusModel extends FocusModel<TitledPane> {
  
          private final Accordion accordion;
          private final ChangeListener<Boolean> focusListener = new ChangeListener<Boolean>() {
              @Override
              public void changed(ObservableValue<? extends Boolean> observable, Boolean oldValue, Boolean newValue) {
                  if (newValue) {
                      if (accordion.getExpandedPane() != null) {
                          accordion.getExpandedPane().requestFocus();
                      } else {
                          // TODO need to detect the focus direction
                          // to selected the first panel when TAB is pressed
                          // or select the last panel when SHIFT TAB is pressed.
                          if (! accordion.getPanes().isEmpty()) {
                              accordion.getPanes().get(0).requestFocus();
                          }
                      }
                  }
              }
          };
          private final ChangeListener<Boolean> paneFocusListener = new ChangeListener<Boolean>() {
              @Override public void changed(ObservableValue<? extends Boolean> observable, Boolean oldValue, Boolean newValue) {
                  if (newValue) {
                      final ReadOnlyBooleanProperty focusedProperty = (ReadOnlyBooleanProperty) observable;
                      final TitledPane tp = (TitledPane) focusedProperty.getBean();
                      focus(accordion.getPanes().indexOf(tp));
                  }
              }
          };
          private final ListChangeListener<TitledPane> panesListener = c -> {
              while (c.next()) {
                  if (c.wasAdded()) {
                      for (final TitledPane tp: c.getAddedSubList()) {
                          tp.focusedProperty().addListener(paneFocusListener);
                      }
                  } else if (c.wasRemoved()) {
                      for (final TitledPane tp: c.getAddedSubList()) {
                          tp.focusedProperty().removeListener(paneFocusListener);
                      }
                  }
              }
          };
  
          public AccordionFocusModel(final Accordion accordion) {
              if (accordion == null) {
                  throw new IllegalArgumentException("Accordion can not be null");
              }
              this.accordion = accordion;
              this.accordion.focusedProperty().addListener(focusListener);
              this.accordion.getPanes().addListener(panesListener);
              for (final TitledPane tp: this.accordion.getPanes()) {
                  tp.focusedProperty().addListener(paneFocusListener);
              }
          }
  
          void dispose() {
              accordion.focusedProperty().removeListener(focusListener);
              accordion.getPanes().removeListener(panesListener);
              for (final TitledPane tp: this.accordion.getPanes()) {
                  tp.focusedProperty().removeListener(paneFocusListener);
              }
          }
  
          @Override
          protected int getItemCount() {
              final ObservableList<TitledPane> panes = accordion.getPanes();
              return panes == null ? 0 : panes.size();
          }
  
          @Override
          protected TitledPane getModelItem(int row) {
              final ObservableList<TitledPane> panes = accordion.getPanes();
  