ChainEnd.java

/*
 * Copyright (c) 1998, Oracle and/or its affiliates. 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package sun.awt.geom;

final class ChainEnd {
    CurveLink head;
    CurveLink tail;
    ChainEnd partner;
    int etag;

    public ChainEnd(CurveLink first, ChainEnd partner) {
	this.head = first;
	this.tail = first;
	this.partner = partner;
	this.etag = first.getEdgeTag();
    }

    public CurveLink getChain() {
	return head;
    }

    public void setOtherEnd(ChainEnd partner) {
	this.partner = partner;
    }

    public ChainEnd getPartner() {
	return partner;
    }

    /*
     * Returns head of a complete chain to be added to subcurves
     * or null if the links did not complete such a chain.
     */
    public CurveLink linkTo(ChainEnd that) {
	if (etag == AreaOp.ETAG_IGNORE ||
	    that.etag == AreaOp.ETAG_IGNORE)
	{
	    throw new InternalError("ChainEnd linked more than once!");
	}
	if (etag == that.etag) {
	    throw new InternalError("Linking chains of the same type!");
	}
	ChainEnd enter, exit;
	// assert(partner.etag != that.partner.etag);
	if (etag == AreaOp.ETAG_ENTER) {
	    enter = this;
	    exit = that;
	} else {
	    enter = that;
	    exit = this;
	}
	// Now make sure these ChainEnds are not linked to any others...
	etag = AreaOp.ETAG_IGNORE;
	that.etag = AreaOp.ETAG_IGNORE;
	// Now link everything up...
	enter.tail.setNext(exit.head);
	enter.tail = exit.tail;
	if (partner == that) {
	    // Curve has closed on itself...
	    return enter.head;
	}
	// Link this chain into one end of the chain formed by the partners
	ChainEnd otherenter = exit.partner;
	ChainEnd otherexit = enter.partner;
	otherenter.partner = otherexit;
	otherexit.partner = otherenter;
	if (enter.head.getYTop() < otherenter.head.getYTop()) {
	    enter.tail.setNext(otherenter.head);
	    otherenter.head = enter.head;
	} else {
	    otherexit.tail.setNext(enter.head);
	    otherexit.tail = enter.tail;
	}
	return null;
    }

    public void addLink(CurveLink newlink) {
	if (etag == AreaOp.ETAG_ENTER) {
	    tail.setNext(newlink);
	    tail = newlink;
	} else {
	    newlink.setNext(head);
	    head = newlink;
	}
    }

    public double getX() {
	if (etag == AreaOp.ETAG_ENTER) {
	    return tail.getXBot();
	} else {
	    return head.getXBot();
	}
    }
}