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Common utilities shared across Blaise projects.
There is a newer version: 1.0.10
package com.googlecode.blaisemath.geom;

/*
 * #%L
 * BlaiseSketch
 * --
 * Copyright (C) 2014 - 2019 Elisha Peterson
 * --
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * #L%
 */

import java.awt.Shape;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Line2D;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Utility methods for creating shapes from two locations.
 * 
 * @author Elisha Peterson
 */
public abstract class ShapeFromPoints {
    
    /**
     * Create shape from mouse positions. May generate exceptions if either point
     * is null.
     * @param press where mouse was pressed
     * @param release where it was released
     * @return created shape
     */
    public abstract Shape create(Point2D press, Point2D release);
    
    /**
     * Create from nullable points.
     * @param press where mouse was pressed
     * @param release where it was released
     * @return created shape, or null if either point was null
     */
    public @Nullable Shape createFromNullable(@Nullable Point2D press, @Nullable Point2D release) {
        return press == null || release == null ? null
                : create(press, release);
    }
    
    /** Creates line from two points */
    public static class Line extends ShapeFromPoints {
        @Override
        public Shape create(Point2D press, Point2D release) {
            return new Line2D.Double(press, release);
        }
    }
    
    /** Creates circle from two points (center and outside). */
    public static class Circle extends ShapeFromPoints {
        @Override
        public Shape create(Point2D press, Point2D release) {
            double rad = press.distance(release);
            return new Ellipse2D.Double(press.getX()-rad, press.getY()-rad, 2*rad, 2*rad);
        }
    }
    
    /** Creates ellipse from two points (corners of frame). */
    public static class Ellipse extends ShapeFromPoints {
        @Override
        public Shape create(Point2D press, Point2D release) {
            Ellipse2D.Double res = new Ellipse2D.Double();
            res.setFrameFromDiagonal(press, release);
            return res;
        }
    }
    
    /** Creates ellipse from two points (corners of rectangle). */
    public static class Rectangle extends ShapeFromPoints {
        @Override
        public Shape create(Point2D press, Point2D release) {
            Rectangle2D.Double res = new Rectangle2D.Double();
            res.setFrameFromDiagonal(press, release);
            return res;
        }
    }
    
}