/*
 * @(#)OverlayLayout.java	1.18 01/11/29
 *
 * Copyright 2002 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
package javax.swing;


import java.awt.*;
import java.io.Serializable;

/**
 * A layout manager to arrange components over the top
 * of each other.  The requested size of the container
 * will be the largest requested size of the children, 
 * taking alignment needs into consideration.  
 *
 * The alignment is based upon what is needed to properly
 * fit the children in the allocation area.  The children
 * will be placed such that their alignment points are all
 * on top of each other.
 * <p>
 * <strong>Warning:</strong>
 * Serialized objects of this class will not be compatible with 
 * future Swing releases.  The current serialization support is appropriate
 * for short term storage or RMI between applications running the same
 * version of Swing.  A future release of Swing will provide support for
 * long term persistence.
 *
 * @version 1.18 11/29/01
 * @author   Timothy Prinzing
 */
public class OverlayLayout implements LayoutManager2,Serializable {

    /**
     * Constructs a layout manager that performs overlay
     * arrangment of the children.  The layout manager
     * created is dedicated to the given container.
     *
     * @param target  The container to do layout against.
     */
    public OverlayLayout(Container target) {
	this.target = target;
    }

    /**
     * Indicates a child has changed its layout related information,
     * which causes any cached calculations to be flushed.
     *
     * @param target the container
     */
    public void invalidateLayout(Container target) {
	checkContainer(target);
	xChildren = null;
	yChildren = null;
	xTotal = null;
	yTotal = null;
    }

    /**
     * Adds the specified component to the layout. Not used by this class.
     *
     * @param name the name of the component
     * @param comp the the component to be added
     */
    public void addLayoutComponent(String name, Component comp) {
    }

    /**
     * Removes the specified component from the layout. Not used by
     * this class.  
     *
     * @param comp the component to remove
     */
    public void removeLayoutComponent(Component comp) {
    }

    /**
     * Adds the specified component to the layout, using the specified
     * constraint object.
     *
     * @param comp the component to be added
     * @param constraints  where/how the component is added to the layout.
     */
    public void addLayoutComponent(Component comp, Object constraints) {
    }

    /**
     * Returns the preferred dimensions for this layout given the components
     * in the specified target container.  Recomputes the layout if it
     * has been invalidated.  Factors in the current inset setting returned
     * by getInsets().
     *
     * @param target the component which needs to be laid out
     * @return a Dimension object containing the preferred dimensions
     * @see #minimumLayoutSize
     */
    public Dimension preferredLayoutSize(Container target) {
	checkContainer(target);
	checkRequests();

	Dimension size = new Dimension(xTotal.preferred, yTotal.preferred);
	Insets insets = target.getInsets();
	size.width += insets.left + insets.right;
	size.height += insets.top + insets.bottom;
	return size;
    }

    /**
     * Returns the minimum dimensions needed to lay out the components
     * contained in the specified target container.  Recomputes the layout
     * if it has been invalidated, and factors in the current inset setting.
     *
     * @param target the component which needs to be laid out 
     * @return a Dimension object containing the minimum dimensions
     * @see #preferredLayoutSize
     */
    public Dimension minimumLayoutSize(Container target) {
	checkContainer(target);
	checkRequests();

	Dimension size = new Dimension(xTotal.minimum, yTotal.minimum);
	Insets insets = target.getInsets();
	size.width += insets.left + insets.right;
	size.height += insets.top + insets.bottom;
	return size;
    }

    /**
     * Returns the minimum dimensions needed to lay out the components
     * contained in the specified target container.  Recomputes the
     * layout if it has been invalidated, and factors in the inset setting
     * returned by getInset().
     *
     * @param target the component which needs to be laid out 
     * @return a Dimension object containing the maximum dimensions
     * @see #preferredLayoutSize
     */
    public Dimension maximumLayoutSize(Container target) {
	checkContainer(target);
	checkRequests();

	Dimension size = new Dimension(xTotal.maximum, yTotal.maximum);
	Insets insets = target.getInsets();
	size.width += insets.left + insets.right;
	size.height += insets.top + insets.bottom;
	return size;
    }

    /**
     * Returns the alignment along the x axis for the container.
     * If the major axis of the box is the x axis the default
     * alignment will be returned, otherwise the alignment needed
     * to place the children along the x axis will be returned.
     *
     * @param target the container
     * @return the alignment >= 0.0f && <= 1.0f
     */
    public float getLayoutAlignmentX(Container target) {
	checkContainer(target);
	checkRequests();
	return xTotal.alignment;
    }

    /**
     * Returns the alignment along the y axis for the container.
     * If the major axis of the box is the y axis the default
     * alignment will be returned, otherwise the alignment needed
     * to place the children along the y axis will be returned.
     *
     * @param target the container
     * @return the alignment >= 0.0f && <= 1.0f
     */
    public float getLayoutAlignmentY(Container target) {
	checkContainer(target);
	checkRequests();
	return yTotal.alignment;
    }

    /**
     * Called by the AWT when the specified container needs to be laid out.
     *
     * @param target  the container to lay out
     *
     * @exception AWTError  if the target isn't the container specified to the
     *                      BoxLayout constructor
     */
    public void layoutContainer(Container target) {
	checkContainer(target);
	checkRequests();
	
	int nChildren = target.getComponentCount();
	int[] xOffsets = new int[nChildren];
	int[] xSpans = new int[nChildren];
	int[] yOffsets = new int[nChildren];
	int[] ySpans = new int[nChildren];

	// determine the child placements
	Dimension alloc = target.getSize();
	Insets in = target.getInsets();
	alloc.width -= in.left + in.right;
	alloc.height -= in.top + in.bottom;
	SizeRequirements.calculateAlignedPositions(alloc.width, xTotal, 
						   xChildren, xOffsets,
						   xSpans);
	SizeRequirements.calculateAlignedPositions(alloc.height, yTotal,
						   yChildren, yOffsets,
						   ySpans);

	// flush changes to the container
	for (int i = 0; i < nChildren; i++) {
	    Component c = target.getComponent(i);
	    c.setBounds(in.left + xOffsets[i], in.top + yOffsets[i],
			xSpans[i], ySpans[i]);
	}
    }

    void checkContainer(Container target) {
	if (this.target != target) {
	    throw new AWTError("OverlayLayout can't be shared");
	}
    }
    
    void checkRequests() {
	if (xChildren == null || yChildren == null) {
	    // The requests have been invalidated... recalculate
	    // the request information.
	    int n = target.getComponentCount();
	    xChildren = new SizeRequirements[n];
	    yChildren = new SizeRequirements[n];
	    for (int i = 0; i < n; i++) {
		Component c = target.getComponent(i);
		Dimension min = c.getMinimumSize();
		Dimension typ = c.getPreferredSize();
		Dimension max = c.getMaximumSize();
		xChildren[i] = new SizeRequirements(min.width, typ.width, 
						    max.width, 
						    c.getAlignmentX());
		yChildren[i] = new SizeRequirements(min.height, typ.height, 
						    max.height, 
						    c.getAlignmentY());
	    }
	    
	    xTotal = SizeRequirements.getAlignedSizeRequirements(xChildren);
	    yTotal = SizeRequirements.getAlignedSizeRequirements(yChildren);
	}
    }
	    
    private Container target;
    private SizeRequirements[] xChildren;
    private SizeRequirements[] yChildren;
    private SizeRequirements xTotal;
    private SizeRequirements yTotal;
    
}