/*

 * Copyright 2000-2004 Sun Microsystems, Inc.  All Rights Reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package javax.swing;

import java.util.Comparator;

import java.util.LinkedList;

import java.util.ListIterator;

import java.awt.Component;

import java.awt.ComponentOrientation;

import java.awt.Window;

/**

 * Comparator which attempts to sort Components based on their size and

 * position. Code adapted from original javax.swing.DefaultFocusManager

 * implementation.

 *

 * @author David Mendenhall

 */

final class LayoutComparator implements Comparator, java.io.Serializable {

    private static final int ROW_TOLERANCE = 10;

    private boolean horizontal = true;

    private boolean leftToRight = true;

    void setComponentOrientation(ComponentOrientation orientation) {

        horizontal = orientation.isHorizontal();

        leftToRight = orientation.isLeftToRight();

    }

    public int compare(Object o1, Object o2) {

        Component a = (Component)o1;

        Component b = (Component)o2;

        if (a == b) {

            return 0;

        }

        // Row/Column algorithm only applies to siblings. If 'a' and 'b'

        // aren't siblings, then we need to find their most inferior

        // ancestors which share a parent. Compute the ancestory lists for

        // each Component and then search from the Window down until the

        // hierarchy branches.

        if (a.getParent() != b.getParent()) {

            LinkedList aAncestory, bAncestory;

            for(aAncestory = new LinkedList(); a != null; a = a.getParent()) {

                aAncestory.add(a);

                if (a instanceof Window) {

                    break;

                }

            }

            if (a == null) {

                // 'a' is not part of a Window hierarchy. Can't cope.

                throw new ClassCastException();

            }

            for(bAncestory = new LinkedList(); b != null; b = b.getParent()) {

                bAncestory.add(b);

                if (b instanceof Window) {

                    break;

                }

            }

            if (b == null) {

                // 'b' is not part of a Window hierarchy. Can't cope.

                throw new ClassCastException();

            }

            for (ListIterator

                     aIter = aAncestory.listIterator(aAncestory.size()),

                     bIter = bAncestory.listIterator(bAncestory.size()); ;) {

                if (aIter.hasPrevious()) {

                    a = (Component)aIter.previous();

                } else {

                    // a is an ancestor of b

                    return -1;

                }

                if (bIter.hasPrevious()) {

                    b = (Component)bIter.previous();

                } else {

                    // b is an ancestor of a

                    return 1;

                }

                if (a != b) {

                    break;

                }

            }

        }

        int ax = a.getX(), ay = a.getY(), bx = b.getX(), by = b.getY();

        int zOrder = a.getParent().getComponentZOrder(a) - b.getParent().getComponentZOrder(b);

        if (horizontal) {

            if (leftToRight) {

                // LT - Western Europe (optional for Japanese, Chinese, Korean)

                if (Math.abs(ay - by) < ROW_TOLERANCE) {

                    return (ax < bx) ? -1 : ((ax > bx) ? 1 : zOrder);

                } else {

                    return (ay < by) ? -1 : 1;

                }

            } else { // !leftToRight

                // RT - Middle East (Arabic, Hebrew)

                if (Math.abs(ay - by) < ROW_TOLERANCE) {

                    return (ax > bx) ? -1 : ((ax < bx) ? 1 : zOrder);

                } else {

                    return (ay < by) ? -1 : 1;

                }

            }

        } else { // !horizontal

            if (leftToRight) {

                // TL - Mongolian

                if (Math.abs(ax - bx) < ROW_TOLERANCE) {

                    return (ay < by) ? -1 : ((ay > by) ? 1 : zOrder);

                } else {

                    return (ax < bx) ? -1 : 1;

                }

            } else { // !leftToRight

                // TR - Japanese, Chinese, Korean

                if (Math.abs(ax - bx) < ROW_TOLERANCE) {

                    return (ay < by) ? -1 : ((ay > by) ? 1 : zOrder);

                } else {

                    return (ax > bx) ? -1 : 1;

                }

            }

        }

    }

}