path: root/javax/swing/SpringLayout.java

/* SpringLayout.java -- 
   Copyright (C) 2004 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
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
executable, regardless of the license terms of these independent
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package javax.swing;

import java.awt.Component;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.LayoutManager2;
import java.util.HashMap;
import java.util.Map;

/**
 * A very flexible layout manager. Components are laid out by defining the
 * relationships between them. The relationships are expressed as
 * {@link Spring}s. You can attach a Spring for each edge of a component and
 * link it to an edge of a different component. For example, you can say,
 * the northern edge of component A should be attached to the southern edge
 * of component B, and the space between them should be something between
 * x and y pixels, and preferably z pixels.
 * <p>While quite simple, this layout manager can be used to emulate most other
 * layout managers, and can also be used to solve some layout problems, which
 * would be hard to solve with other layout managers.</p>
 *
 * @author Roman Kennke (roman@ontographics.com)
 */
public class SpringLayout implements LayoutManager2
{

  /** The right edge of a component. */
  public static final String EAST = "East";

  /** The top edge of a component. */
  public static final String NORTH = "North";

  /** The bottom edge of a component. */
  public static final String SOUTH = "South";

  /** The left edge of a component. */
  public static final String WEST = "West";

  /** maps components to their constraints. */
  private Map constraintsMap;

  /**
   * The constraints that define the relationships between components.
   * Each Constraints object can hold 4 Springs: one for each edge of the
   * component. Additionally it can hold Springs for the components width
   * and the components height. Since the height and width constraints are
   * dependend on the other constraints, a component can be over-constraint.
   * In this case (like when all of NORTH, SOUTH and HEIGHT are constraint),
   * the values are adjusted, so that the mathematics still hold true.
   *
   * @author Roman Kennke (roman@ontographics.com)
   */
  public static class Constraints
  {

    // The constraints for each edge, and width and height.
    /** The Spring for the left edge. */
    private Spring x;

    /** The Spring for the upper edge. */
    private Spring y;

    /** The Spring for the height. */
    private Spring height;

    /** The Spring for the width. */
    private Spring width;

    /** The Spring for the right edge. */
    private Spring east;

    /** The Spring for the bottom edge. */
    private Spring south;

    /**
     * Creates a new Constraints object.
     * There is no constraint set.
     */
    public Constraints()
    {
      x = y = height = width = east = south = null;
    }

    /**
     * Creates a new Constraints object.
     *
     * @param x the constraint for the left edge of the component.
     * @param y the constraint for the upper edge of the component.
     */
    public Constraints(Spring x, Spring y)
    {
      this.x = x;
      this.y = y;
      width = height = east = south = null;
    }

    /**
     * Creates a new Constraints object.
     *
     * @param x the constraint for the left edge of the component.
     * @param y the constraint for the upper edge of the component.
     * @param width the constraint for the width of the component.
     * @param height the constraint for the height of the component.
     */
    public Constraints(Spring x, Spring y, Spring width, Spring height)
    {
      this.x = x;
      this.y = y;
      this.width = width;
      this.height = height;
      east = south = null;
    }

    /**
     * Returns the constraint for the edge with the <code>edgeName</code>.
     * This is expected to be one of
     * {@link #EAST}, {@link #WEST}, {@link NORTH} or {@link SOUTH}.
     *
     * @param edgeName the name of the edge.
     * @return the constraint for the specified edge.
     */
    public Spring getConstraint(String edgeName)
    {
      Spring retVal = null;
      if (edgeName.equals(SpringLayout.NORTH))
	retVal = y;
      else if (edgeName.equals(SpringLayout.WEST))
        retVal = x;
      else if (edgeName.equals(SpringLayout.SOUTH))
        {
          retVal = south;
	  if ((retVal == null) && (y != null) && (height != null))
            retVal = Spring.sum(y, height);
        }
      else if (edgeName.equals(SpringLayout.EAST))
        {
          retVal = east;
          if ((retVal == null) && (x != null) && (width != null))
            retVal = Spring.sum(x, width);
	}

      return retVal;
    }

    /**
     * Returns the constraint for the height of the component.
     *
     * @return the height constraint. 
     */
    public Spring getHeight()
    {
      Spring retVal = height;
      if ((retVal == null) && (y != null) && (south != null))
        {
          retVal = Spring.sum(south, Spring.minus(y));
        }
      return retVal;
    }

    /**
     * Returns the constraint for the width of the component.
     *
     * @return the width constraint.
     */
    public Spring getWidth()
    {
      Spring retVal = width;
      if ((retVal == null) && (x != null) && (east != null))
        {
          retVal = Spring.sum(east, Spring.minus(x));
	}
      return retVal;
    }

    /**
     * Returns the constraint for the left edge of the component.
     *
     * @return the left-edge constraint (== WEST).
     */
    public Spring getX()
    {
      Spring retVal = x;
      if ((retVal == null) && (width != null) && (east != null))
        {
          retVal = Spring.sum(east, Spring.minus(width));
        }
      return retVal;
    }

    /**
     * Returns the constraint for the upper edge of the component.
     *
     * @return the upper-edge constraint (== NORTH).
     */
    public Spring getY()
    {
      Spring retVal = y;
      if ((retVal == null) && (height != null) && (south != null))
        {
          retVal = Spring.sum(south, Spring.minus(height));
        }
      return retVal;
    }

    /**
     * Sets a constraint for the specified edge. If this leads to an
     * over-constrained situation, the constraints get adjusted, so that
     * the mathematics still hold true.
     *
     * @param edgeName the name of the edge, one of {@link #EAST},
     *     {@link #WEST}, {@link NORTH} or {@link SOUTH}.
     * @param s the constraint to be set.
     */
    public void setConstraint(String edgeName, Spring s)
    {
    
      if (edgeName.equals(SpringLayout.WEST))
        {
          x = s;
	  if ((width != null) && (east != null))
            width = Spring.sum(east, Spring.minus(x));
        }
      else if (edgeName.equals(SpringLayout.NORTH))
        {
          y = s;
          if ((height != null) && (south != null))
          height = Spring.sum(south, Spring.minus(y));
        }
      else if (edgeName.equals(SpringLayout.EAST))
        {
          east = s;
          if ((x != null) && (width != null))
            x = Spring.sum(east, Spring.minus(width));
        }
      else if (edgeName.equals(SpringLayout.SOUTH))
        {
          south = s;
          if ((height != null) && (y != null))
	    y = Spring.sum(south, Spring.minus(height));
        }

    }

    /**
     * Sets the height-constraint.
     *
     * @param s the constraint to be set.
     */
    public void setHeight(Spring s)
    {
      height = s;
      if ((south != null) && (y != null))
        south = Spring.sum(y, height);

    }

    /**
     * Sets the width-constraint.
     *
     * @param s the constraint to be set.
     */
    public void setWidth(Spring s)
    {
      width = s;
      if ((east != null) && (x != null))
        east = Spring.sum(x, width);

    }

    /**
     * Sets the WEST-constraint.
     *
     * @param s the constraint to be set.
     */
    public void setX(Spring s)
    {
      x = s;
      if ((width != null) && (east != null))
        width = Spring.sum(east, Spring.minus(x));

    }

    /**
     * Sets the NORTH-constraint.
     *
     * @param s the constraint to be set.
     */
    public void setY(Spring s)
    {
      y = s;
      if ((height != null) && (south != null))
        height = Spring.sum(south, Spring.minus(y));

    }
  }

  /**
   * Creates a new SpringLayout.
   */
  public SpringLayout()
  {

    constraintsMap = new HashMap();
  }

  /**
   * Adds a layout component and a constraint object to this layout.
   * This method is usually only called by a {@java.awt.Container}s add
   * Method.
   *
   * @param component the component to be added.
   * @param constraint the constraint to be set.
   */
  public void addLayoutComponent(Component component, Object constraint)
  {
    constraintsMap.put(component, constraint);
  }


  /**
   * Adds a layout component and a constraint object to this layout.
   * This method is usually only called by a {@java.awt.Container}s add
   * Method. This method does nothing, since SpringLayout does not manage
   * String-indexed components.
   *
   * @param component the component to be added.
   * @param constraint the constraint to be set.
   */
  public void addLayoutComponent(String name, Component c)
  {
    // do nothing here.
  }

  /**
   * Returns the constraint of the edge named by <code>edgeName</code>.
   *
   * @param c the component from which to get the constraint.
   * @param edgeName the name of the edge, one of {@link #EAST},
   *     {@link #WEST}, {@link NORTH} or {@link SOUTH}.
   * @return the constraint of the edge <code>edgeName</code> of the
   * component c.
   */
  public Spring getConstraint(String edgeName, Component c)
  {
    Constraints constraints = getConstraints(c);
    return constraints.getConstraint(edgeName);
  }

  /**
   * Returns the {@link Constraints} object associated with the specified
   * component.
   *
   * @param c the component for which to determine the constraint.
   * @return the {@link Constraints} object associated with the specified
   *      component.
   */
  public SpringLayout.Constraints getConstraints(Component c)
  {
    Constraints constraints = (Constraints) constraintsMap.get(c);
    if (constraints == null)
      {
        Container parent = c.getParent();
        constraints = new Constraints();
        if (parent != null)
          {
            constraints.setX
              (Spring.constant(parent.getInsets().left));
            constraints.setY
              (Spring.constant(parent.getInsets().top));
          }
        else
          {
            constraints.setX
              (Spring.constant(0));
            constraints.setY
              (Spring.constant(0));

          }
        constraints.setWidth
          (Spring.constant(c.getMinimumSize().width,
                           c.getPreferredSize().width,
                           c.getMaximumSize().width));
        constraints.setHeight
          (Spring.constant(c.getMinimumSize().height,
                           c.getPreferredSize().height,
                           c.getMaximumSize().height));

        constraintsMap.put(c, constraints);

      }

    return constraints;
  }

  /**
   * Returns the X alignment of the Container <code>p</code>.
   *
   * @param p the {@link java.awt.Container} for which to determine the X
   *     alignment.
   * @return always 0.0
   */
  public float getLayoutAlignmentX(Container p)
  {
    return 0.0F;
  }

  /**
   * Returns the Y alignment of the Container <code>p</code>.
   *
   * @param p the {@link java.awt.Container} for which to determine the Y
   *     alignment.
   * @return always 0.0
   */
  public float getLayoutAlignmentY(Container p)
  {
    return 0.0F;
  }

  /**
   * Recalculate a possibly cached layout.
   */
  public void invalidateLayout(Container p)
  {
    // nothing to do here yet
  }

  /**
   * Lays out the container <code>p</code>.
   *
   * @param p the container to be laid out.
   */
  public void layoutContainer(Container p)
  {

    addLayoutComponent(p, new Constraints(Spring.constant(0),
                                          Spring.constant(0)));

    int offsetX = p.getInsets().left;
    int offsetY = p.getInsets().right;

    Component[] components = p.getComponents();
    for (int index = 0; index < components.length; index++)
      {
        Component c = components[index];
        Constraints constraints = getConstraints(c);
        int x = constraints.getX().getValue();
        int y = constraints.getY().getValue();
        int width = constraints.getWidth().getValue();
        int height = constraints.getHeight().getValue();

        c.setLocation(x + offsetX, y + offsetY);
        c.setSize(width, height);
      }

  }

  /**
   * Calculates the maximum size of the layed out container. This
   * respects the maximum sizes of all contained components.
   *
   * @param p the container to be laid out.
   * @return the maximum size of the container.
   */
  public Dimension maximumLayoutSize(Container p)
  {
    int maxX = 0;
    int maxY = 0;

    int offsetX = p.getInsets().left;
    int offsetY = p.getInsets().right;

    Component[] components = p.getComponents();
    for (int index = 0; index < components.length; index++)
      {
        Component c = components[index];
        Constraints constraints = getConstraints(c);
        int x = constraints.getX().getMaximumValue();
        int y = constraints.getY().getMaximumValue();
        int width = constraints.getWidth().getMaximumValue();
        int height = constraints.getHeight().getMaximumValue();

        int rightEdge = offsetX + x + width;
        if (rightEdge > maxX)
          maxX = rightEdge;
        int bottomEdge = offsetY + y + height;
        if (bottomEdge > maxY)
          maxY = bottomEdge;
      }

    return new Dimension(maxX, maxY);
  }


  /**
   * Calculates the minimum size of the layed out container. This
   * respects the minimum sizes of all contained components.
   *
   * @param p the container to be laid out.
   * @return the minimum size of the container.
   */
  public Dimension minimumLayoutSize(Container p)
  {
    int maxX = 0;
    int maxY = 0;

    int offsetX = p.getInsets().left;
    int offsetY = p.getInsets().right;

    Component[] components = p.getComponents();
    for (int index = 0; index < components.length; index++)
      {
        Component c = components[index];
        Constraints constraints = getConstraints(c);
        int x = constraints.getX().getMinimumValue();
        int y = constraints.getY().getMinimumValue();
        int width = constraints.getWidth().getMinimumValue();
        int height = constraints.getHeight().getMinimumValue();

        int rightEdge = offsetX + x + width;
        if (rightEdge > maxX)
          maxX = rightEdge;
        int bottomEdge = offsetY + y + height;
        if (bottomEdge > maxY)
          maxY = bottomEdge;
      }

    return new Dimension(maxX, maxY);
  }

  /**
   * Calculates the preferred size of the layed out container. This
   * respects the preferred sizes of all contained components.
   *
   * @param p the container to be laid out.
   * @return the preferred size of the container.
   */
  public Dimension preferredLayoutSize(Container p)
  {
    int maxX = 0;
    int maxY = 0;

    int offsetX = p.getInsets().left;
    int offsetY = p.getInsets().right;

    Component[] components = p.getComponents();
    for (int index = 0; index < components.length; index++)
      {
        Component c = components[index];
        Constraints constraints = getConstraints(c);
        int x = constraints.getX().getPreferredValue();
        int y = constraints.getY().getPreferredValue();
        int width = constraints.getWidth().getPreferredValue();
        int height = constraints.getHeight().getPreferredValue();

        int rightEdge = offsetX + x + width;
        if (rightEdge > maxX)
          maxX = rightEdge;
        int bottomEdge = offsetY + y + height;
        if (bottomEdge > maxY)
          maxY = bottomEdge;
      }

    return new Dimension(maxX, maxY);
  }

  /**
   * Attaches the edge <code>e1</code> of component <code>c1</code> to
   * the edge <code>e2</code> of component <code>c2</code> width the
   * fixed strut <code>pad</code>.
   *
   * @param e1 the edge of component 1.
   * @param c1 the component 1.
   * @param pad the space between the components in pixels.
   * @param e2 the edge of component 2.
   * @param c2 the component 2.
   */
  public void putConstraint(String e1, Component c1, int pad, String e2, 
                            Component c2)
  {
    Constraints constraints1 = getConstraints(c1);
    Constraints constraints2 = getConstraints(c2);

    Spring strut = Spring.constant(pad);
    Spring otherEdge = constraints2.getConstraint(e2);
    constraints1.setConstraint(e1, Spring.sum(strut, otherEdge));

  }

  /**
   * Attaches the edge <code>e1</code> of component <code>c1</code> to
   * the edge <code>e2</code> of component <code>c2</code> width the
   * {@link Spring} <code>s</code>.
   *
   * @param e1 the edge of component 1.
   * @param c1 the component 1.
   * @param s the space between the components as a {@link Spring} object.
   * @param e2 the edge of component 2.
   * @param c2 the component 2.
   */
  public void putConstraint(String e1, Component c1, Spring s, String e2, 
                            Component c2)
  {
    Constraints constraints1 = getConstraints(c1);
    Constraints constraints2 = getConstraints(c2);

    Spring otherEdge = constraints2.getConstraint(e2);
    constraints1.setConstraint(e1, Spring.sum(s, otherEdge));

  }

  /**
   * Removes a layout component.
   * @param c the layout component to remove.
   */
  public void removeLayoutComponent(Component c)
  {
    // do nothing here
  }
}