package com.swtdesigner;
   
   import java.awt.Component;
   import java.awt.Container;
   import java.awt.FocusTraversalPolicy;
   
   /**
    * Cyclic focus traversal policy based on array of components.
    * 
   * This class may be freely distributed as part of any application or plugin.
   * <p>
   * 
   * @author scheglov_ke
   */
  public class FocusTraversalOnArray extends FocusTraversalPolicy {
      private final Component m_Components[];
  
      ////////////////////////////////////////////////////////////////////////////
      //
      // Constructor
      //
      ////////////////////////////////////////////////////////////////////////////
      public FocusTraversalOnArray(Component components[]) {
          m_Components = components;
      }
  
      ////////////////////////////////////////////////////////////////////////////
      //
      // Utilities
      //
      ////////////////////////////////////////////////////////////////////////////
      private int indexCycle(int index, int delta) {
          int size = m_Components.length;
          int next = (index + delta + size) % size;
          return next;
      }
  
      private Component cycle(Component currentComponent, int delta) {
          int index = -1;
          loop: for (int i = 0; i < m_Components.length; i++) {
              Component component = m_Components[i];
              for (Component c = currentComponent; c != null; c = c.getParent()) {
                  if (component == c) {
                      index = i;
                      break loop;
                  }
              }
          }
          // try to find enabled component in "delta" direction
          int initialIndex = index;
          while (true) {
              int newIndex = indexCycle(index, delta);
              if (newIndex == initialIndex) {
                  break;
              }
              index = newIndex;
              //
              Component component = m_Components[newIndex];
              if (component.isEnabled()) {
                  return component;
              }
          }
          // not found
          return currentComponent;
      }
  
      ////////////////////////////////////////////////////////////////////////////
      //
      // FocusTraversalPolicy
      //
      ////////////////////////////////////////////////////////////////////////////
      public Component getComponentAfter(Container container, Component component) {
          return cycle(component, 1);
      }
  
      public Component getComponentBefore(Container container, Component component) {
          return cycle(component, -1);
      }
  
      public Component firstComponent(Container container) {
          return m_Components[0];
      }
  
      public Component getLastComponent(Container container) {
          return m_Components[m_Components.length - 1];
      }
  
      public Component getDefaultComponent(Container container) {
          return firstComponent(container);
      }
  
      @Override
      public Component getFirstComponent(Container aContainer) {
          return firstComponent(aContainer);
      }
  }