CardLayout.java

// CardLayout.java - Card-based layout engine

/* Copyright (C) 1999, 2000, 2002, 2003  Free Software Foundation

This file is part of GNU Classpath.

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it under the terms of the GNU General Public License as published by
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permission to link this library with independent modules to produce an
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package java.awt;

import java.util.Enumeration;
import java.util.Hashtable;
import java.io.Serializable;

/** This class implements a card-based layout scheme.  Each included
 * component is treated as a card.  Only one card can be shown at a
 * time.  This class includes methods for changing which card is
 * shown.
 *
 * @author Tom Tromey <tromey@redhat.com>
 * @author Aaron M. Renn (arenn@urbanophile.com)
 */
public class CardLayout implements LayoutManager2, Serializable
{
  static final long serialVersionUID = -4328196481005934313L;

  /**
   * Initializes a new instance of <code>CardLayout</code> with horizontal
   * and vertical gaps of 0.
   */
  public CardLayout ()
  {
    this (0, 0);
  }

  /**
   * Create a new <code>CardLayout</code> object with the specified
   * horizontal and vertical gaps.
   * @param hgap The horizontal gap
   * @param vgap The vertical gap
   */
  public CardLayout (int hgap, int vgap)
  {
    this.hgap = hgap;
    this.vgap = vgap;
    this.tab = new Hashtable ();
  }

  /** Add a new component to the layout.  The constraint must be a
   * string which is used to name the component.  This string can
   * later be used to refer to the particular component.
   * @param comp The component to add
   * @param constraints The name by which the component can later be called
   * @exception IllegalArgumentException If `constraints' is not a
   * <code>String</code>
   */
  public void addLayoutComponent (Component comp, Object constraints)
  {
    if (! (constraints instanceof String))
      throw new IllegalArgumentException ("Object " + constraints
					  + " is not a string");
    tab.put (constraints, comp);
  }

  /** Add a new component to the layout.  The name can be used later
   * to refer to the component.
   * @param name The name by which the component can later be called
   * @param comp The component to add
   * @deprecated This method is deprecated in favor of
   * <code>addLayoutComponent(Component, Object)</code>.
   */
  public void addLayoutComponent (String name, Component comp)
  {
    addLayoutComponent (comp, name);
  }

  /** Cause the first component in the container to be displayed.
   * @param parent The parent container
   */
  public void first (Container parent)
  {
    gotoComponent (parent, FIRST);
  }

  /** Return this layout manager's horizontal gap.  */
  public int getHgap ()
  {
    return hgap;
  }

  /** Return this layout manager's x alignment.  This method always
   * returns Component.CENTER_ALIGNMENT.
   * @param parent Container using this layout manager instance
   */
  public float getLayoutAlignmentX (Container parent)
  {
    return Component.CENTER_ALIGNMENT;
  }

  /** Returns this layout manager's y alignment.  This method always
   * returns Component.CENTER_ALIGNMENT.
   * @param parent Container using this layout manager instance
   */
  public float getLayoutAlignmentY (Container parent)
  {
    return Component.CENTER_ALIGNMENT;
  }

  /** Return this layout manager's vertical gap.  */
  public int getVgap ()
  {
    return vgap;
  }

  /** Invalidate this layout manager's state.  */
  public void invalidateLayout (Container target)
  {
    // Do nothing.
  }

  /** Cause the last component in the container to be displayed.
   * @param parent The parent container
   */
  public void last (Container parent)
  {
    gotoComponent (parent, LAST);
  }

  /**
   * Lays out the container.  This is done by resizing the child components
   * to be the same size as the parent, less insets and gaps.
   *
   * @param parent The parent container.
   */ 
  public void layoutContainer (Container parent)
  {
    synchronized (parent.getTreeLock ())
      {
	int width = parent.width;
	int height = parent.height;

	Insets ins = parent.getInsets ();

	int num = parent.ncomponents;
	Component[] comps = parent.component;

	int x = ins.left + hgap;
	int y = ins.top + vgap;
	width = width - 2 * hgap - ins.left - ins.right;
	height = height - 2 * vgap - ins.top - ins.bottom;

	for (int i = 0; i < num; ++i)
	  comps[i].setBounds (x, y, width, height);
      }
  }

  /** Get the maximum layout size of the container.
   * @param target The parent container
   */
  public Dimension maximumLayoutSize (Container target)
  {
    // The JCL says that this returns Integer.MAX_VALUE for both
    // dimensions.  But that just seems wrong to me.
    return getSize (target, MAX);
  }

  /** Get the minimum layout size of the container.
   * @param target The parent container
   */
  public Dimension minimumLayoutSize (Container target)
  {
    return getSize (target, MIN);
  }

  /** Cause the next component in the container to be displayed.  If
   * this current card is the  last one in the deck, the first
   * component is displayed.
   * @param parent The parent container
   */
  public void next (Container parent)
  {
    gotoComponent (parent, NEXT);
  }

  /** Get the preferred layout size of the container.
   * @param target The parent container
   */
  public Dimension preferredLayoutSize (Container parent)
  {
    return getSize (parent, PREF);
  }

  /** Cause the previous component in the container to be displayed.
   * If this current card is the first one in the deck, the last
   * component is displayed.
   * @param parent The parent container
   */
  public void previous (Container parent)
  {
    gotoComponent (parent, PREV);
  }

  /** Remove the indicated component from this layout manager.
   * @param comp The component to remove
   */
  public void removeLayoutComponent (Component comp)
  {
    Enumeration e = tab.keys ();
    while (e.hasMoreElements ())
      {
	Object key = e.nextElement ();
	if (tab.get (key) == comp)
	  {
	    tab.remove (key);
	    break;
	  }
      }
  }

  /** Set this layout manager's horizontal gap.
   * @param hgap The new gap
   */
  public void setHgap (int hgap)
  {
    this.hgap = hgap;
  }

  /** Set this layout manager's vertical gap.
   * @param vgap The new gap
   */
  public void setVgap (int vgap)
  {
    this.vgap = vgap;
  }

  /** Cause the named component to be shown.  If the component name is
   * unknown, this method does nothing.
   * @param parent The parent container
   * @param name The name of the component to show
   */
  public void show (Container parent, String name)
  {
    Object target = tab.get (name);
    if (target != null)
      {
	int num = parent.ncomponents;
	// This is more efficient than calling getComponents().
	Component[] comps = parent.component;
	for (int i = 0; i < num; ++i)
	  {
	    if (comps[i].isVisible())
	      {
		if (target == comps[i])
		  return;
		comps[i].setVisible (false);
	      }
	  }
	((Component) target).setVisible (true);
      }
  }

  /**
   * Returns a string representation of this layout manager.
   *
   * @return A string representation of this object.
   */
  public String toString ()
  {
    return getClass ().getName () + "[" + hgap + "," + vgap + "]";
  }

  /** This implements first(), last(), next(), and previous().
   * @param parent The parent container
   * @param what The type of goto: FIRST, LAST, NEXT or PREV
   */
  private void gotoComponent (Container parent, int what)
  {
    synchronized (parent.getTreeLock ())
      {
	int num = parent.ncomponents;
	// This is more efficient than calling getComponents().
	Component[] comps = parent.component;
	int choice = -1;

	if (what == FIRST)
	  choice = 0;
	else if (what == LAST)
	  choice = num - 1;

	for (int i = 0; i < num; ++i)
	  {
	    if (comps[i].isVisible ())
	      {
		if (what == NEXT)
		  {
		    choice = i + 1;
		    if (choice == num)
		      choice = 0;
		  }
		else if (what == PREV)
		  {
		    choice = i - 1;
		    if (choice < 0)
		      choice = num - 1;
		  }
		else if (choice == i)
		  {
		    // Do nothing if we're already looking at the right
		    // component.
		    return;
		  }
		comps[i].setVisible (false);
 
		if (choice >= 0)
		  break;
	      }
	  }

	if (choice >= 0 && choice < num)
	  comps[choice].setVisible (true);
      }
  }

  // Compute the size according to WHAT.
  private Dimension getSize (Container parent, int what)
  {
    synchronized (parent.getTreeLock ())
      {
	int w = 0, h = 0, num = parent.ncomponents;
	Component[] comps = parent.component;

	for (int i = 0; i < num; ++i)
	  {
	    Dimension d;

	    if (what == MIN)
	      d = comps[i].getMinimumSize ();
	    else if (what == MAX)
	      d = comps[i].getMaximumSize ();
	    else
	      d = comps[i].getPreferredSize ();

	    w = Math.max (d.width, w);
	    h = Math.max (d.height, h);
	  }

	Insets i = parent.getInsets ();
	w += 2 * hgap + i.right + i.left;
	h += 2 * vgap + i.bottom + i.top;

	// Handle overflow.
	if (w < 0)
	  w = Integer.MAX_VALUE;
	if (h < 0)
	  h = Integer.MAX_VALUE;

	return new Dimension (w, h);
      }
  }

  /**
   * @serial Horizontal gap value.
   */
  private int hgap;

  /**
   * @serial Vertical gap value.
   */
  private int vgap;

  /**
   * @serial Table of named components.
   */
  private Hashtable tab;

  // These constants are used by the private gotoComponent method.
  private int FIRST = 0;
  private int LAST = 1;
  private int NEXT = 2;
  private int PREV = 3;

  // These constants are used by the private getSize method.
  private int MIN = 0;
  private int MAX = 1;
  private int PREF = 2;
}