gcc/libjava/java/awt/CardLayout.java

// CardLayout.java - Card-based layout engine

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

   This file is part of libgcj.

This software is copyrighted work licensed under the terms of the
Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
details.  */

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.
 *
 * @version 0.0
 * @author Tom Tromey <tromey@redhat.com>
 * @date December 2, 2000
 */
public class CardLayout implements LayoutManager2, Serializable
{
  /** Create a new CardLayout object with both gaps zero.  */
  public CardLayout ()
  {
    this (0, 0);
  }

  /** Create a new CardLayout 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.map = 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 string
   */
  public void addLayoutComponent (Component comp, Object constraints)
  {
    if (! (constraints instanceof String))
      throw new IllegalArgumentException ("Object " + constraints
					  + " is not a string");
    map.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
   */
  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, null);
  }

  /** 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, null);
  }

  /** Lay out the container's components based on the current
   * settings.
   * @param parent The parent container
   */
  public void layoutContainer (Container parent)
  {
    int width = parent.width;
    int height = parent.height;

    Insets ins = parent.getInsets ();

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

    for (int i = 0; i < num; ++i)
      {
	comps[i].setBounds (hgap + ins.left, vgap + ins.top,
			    width - 2 * hgap - ins.left - ins.right,
			    height - 2 * vgap - ins.top - ins.bottom);
      }
  }

  /** 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.
   * @param parent The parent container
   */
  public void next (Container parent)
  {
    gotoComponent (parent, NEXT, null);
  }

  /** 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.
   * @param parent The parent container
   */
  public void previous (Container parent)
  {
    gotoComponent (parent, PREV, null);
  }

  /** Remove the indicated component from this layout manager.
   * @param comp The component to remove
   */
  public void removeLayoutComponent (Component comp)
  {
    Enumeration e = map.keys ();
    while (e.hasMoreElements ())
      {
	Object key = e.nextElement ();
	if (map.get (key) == comp)
	  {
	    map.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 = map.get (name);
    if (target != null)
      gotoComponent (parent, NONE, (Component) target);
  }

  public String toString ()
  {
    return getClass ().getName () + "[" + hgap + "," + vgap + "]";
  }

  // This implements first(), last(), next(), and previous().
  private void gotoComponent (Container parent, int what,
			      Component target)
  {
    int num = parent.getComponentCount ();
    // 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;
    else if (what >= 0)
      choice = what;

    for (int i = 0; i < num; ++i)
      {
	// If TARGET is set then we are looking for a specific
	// component.
	if (target != null)
	  {
	    if (target == comps[i])
	      choice = 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
	      {
		// Do nothing if we're already looking at the right
		// component.
		if (choice == i)
		  return;
	      }
	    comps[i].setVisible (false);

	    if (choice >= 0)
	      break;
	  }
      }

    comps[choice].setVisible (true);
  }

  // Compute the size according to WHAT.
  private Dimension getSize (Container parent, int what)
  {
    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);
  }

  // The gaps.
  private int hgap;
  private int vgap;

  // This hashtable maps a name to a component.
  private Hashtable map;

  // 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;
  private int NONE = 4;

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