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 getFirstComponent(Container container) {
  		return m_Components[0];
  	}
  	public Component getLastComponent(Container container) {
  		return m_Components[m_Components.length - 1];
  	}
  	public Component getDefaultComponent(Container container) {
  		return getFirstComponent(container);
  	}
  }