org.eclipse.swt.graphics.Region.java Source code

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/*******************************************************************************
 * Copyright (c) 2000, 2017 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.swt.graphics;

import org.eclipse.swt.*;
import org.eclipse.swt.internal.*;
import org.eclipse.swt.internal.cocoa.*;

/**
 * Instances of this class represent areas of an x-y coordinate
 * system that are aggregates of the areas covered by a number
 * of polygons.
 * <p>
 * Application code must explicitly invoke the <code>Region.dispose()</code>
 * method to release the operating system resources managed by each instance
 * when those instances are no longer required.
 * </p>
 *
 * @see <a href="http://www.eclipse.org/swt/examples.php">SWT Example: GraphicsExample</a>
 * @see <a href="http://www.eclipse.org/swt/">Sample code and further information</a>
 */
public final class Region extends Resource {
    /**
     * the OS resource for the region
     * (Warning: This field is platform dependent)
     * <p>
     * <b>IMPORTANT:</b> This field is <em>not</em> part of the SWT
     * public API. It is marked public only so that it can be shared
     * within the packages provided by SWT. It is not available on all
     * platforms and should never be accessed from application code.
     * </p>
     *
     * @noreference This field is not intended to be referenced by clients.
     */
    public long handle;

    /**
     * Constructs a new empty region.
     * <p>
     * You must dispose the region when it is no longer required.
     * </p>
     *
     * @exception SWTError <ul>
     *    <li>ERROR_NO_HANDLES if a handle could not be obtained for region creation</li>
     * </ul>
     *
     * @see #dispose()
     */
    public Region() {
        this(null);
    }

    /**
     * Constructs a new empty region.
     * <p>
     * You must dispose the region when it is no longer required.
     * </p>
     *
     * @param device the device on which to allocate the region
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if device is null and there is no current device</li>
     * </ul>
     * @exception SWTError <ul>
     *    <li>ERROR_NO_HANDLES if a handle could not be obtained for region creation</li>
     * </ul>
     *
     * @see #dispose()
     *
     * @since 3.0
     */
    public Region(Device device) {
        super(device);
        NSAutoreleasePool pool = null;
        if (!NSThread.isMainThread())
            pool = (NSAutoreleasePool) new NSAutoreleasePool().alloc().init();
        try {
            handle = OS.NewRgn();
            if (handle == 0)
                SWT.error(SWT.ERROR_NO_HANDLES);
            init();
        } finally {
            if (pool != null)
                pool.release();
        }
    }

    Region(Device device, long handle) {
        super(device);
        this.handle = handle;
    }

    /**
     * Invokes platform specific functionality to allocate a new region.
     * <p>
     * <b>IMPORTANT:</b> This method is <em>not</em> part of the public
     * API for <code>Region</code>. It is marked public only so that it
     * can be shared within the packages provided by SWT. It is not
     * available on all platforms, and should never be called from
     * application code.
     * </p>
     *
     * @param device the device on which to allocate the region
     * @param handle the handle for the region
     * @return a new region object containing the specified device and handle
     *
     * @noreference This method is not intended to be referenced by clients.
     */
    public static Region cocoa_new(Device device, long handle) {
        return new Region(device, handle);
    }

    static long polyToRgn(int[] poly, int length) {
        short[] r = new short[4];
        long polyRgn = OS.NewRgn(), rectRgn = OS.NewRgn();
        int minY = poly[1], maxY = poly[1];
        for (int y = 3; y < length; y += 2) {
            if (poly[y] < minY)
                minY = poly[y];
            if (poly[y] > maxY)
                maxY = poly[y];
        }
        int[] inter = new int[length + 1];
        for (int y = minY; y <= maxY; y++) {
            int count = 0;
            int x1 = poly[0], y1 = poly[1];
            for (int p = 2; p < length; p += 2) {
                int x2 = poly[p], y2 = poly[p + 1];
                if (y1 != y2 && ((y1 <= y && y < y2) || (y2 <= y && y < y1))) {
                    inter[count++] = (int) ((((y - y1) / (float) (y2 - y1)) * (x2 - x1)) + x1 + 0.5f);
                }
                x1 = x2;
                y1 = y2;
            }
            int x2 = poly[0], y2 = poly[1];
            if (y1 != y2 && ((y1 <= y && y < y2) || (y2 <= y && y < y1))) {
                inter[count++] = (int) ((((y - y1) / (float) (y2 - y1)) * (x2 - x1)) + x1 + 0.5f);
            }
            for (int gap = count / 2; gap > 0; gap /= 2) {
                for (int i = gap; i < count; i++) {
                    for (int j = i - gap; j >= 0; j -= gap) {
                        if ((inter[j] - inter[j + gap]) <= 0)
                            break;
                        int temp = inter[j];
                        inter[j] = inter[j + gap];
                        inter[j + gap] = temp;
                    }
                }
            }
            for (int i = 0; i < count; i += 2) {
                OS.SetRect(r, (short) inter[i], (short) y, (short) (inter[i + 1]), (short) (y + 1));
                OS.RectRgn(rectRgn, r);
                OS.UnionRgn(polyRgn, rectRgn, polyRgn);
            }
        }
        OS.DisposeRgn(rectRgn);
        return polyRgn;
    }

    static long polyRgn(int[] pointArray, int count) {
        NSAutoreleasePool pool = null;
        if (!NSThread.isMainThread())
            pool = (NSAutoreleasePool) new NSAutoreleasePool().alloc().init();
        try {
            long polyRgn;
            if (C.PTR_SIZEOF == 4) {
                polyRgn = OS.NewRgn();
                OS.OpenRgn();
                OS.MoveTo((short) pointArray[0], (short) pointArray[1]);
                for (int i = 1; i < count / 2; i++) {
                    OS.LineTo((short) pointArray[2 * i], (short) pointArray[2 * i + 1]);
                }
                OS.LineTo((short) pointArray[0], (short) pointArray[1]);
                OS.CloseRgn(polyRgn);
            } else {
                polyRgn = polyToRgn(pointArray, count);
            }
            return polyRgn;
        } finally {
            if (pool != null)
                pool.release();
        }
    }

    /**
     * Adds the given polygon to the collection of polygons
     * the receiver maintains to describe its area.
     *
     * @param pointArray points that describe the polygon to merge with the receiver
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the argument is null</li>
     * </ul>
     * @exception SWTException <ul>
     *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
     * </ul>
     *
     * @since 3.0
     *
     */
    public void add(int[] pointArray) {
        if (isDisposed())
            SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
        if (pointArray == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        NSAutoreleasePool pool = null;
        if (!NSThread.isMainThread())
            pool = (NSAutoreleasePool) new NSAutoreleasePool().alloc().init();
        try {
            add(pointArray, pointArray.length);
        } finally {
            if (pool != null)
                pool.release();
        }
    }

    void add(int[] pointArray, int count) {
        count = count / 2 * 2;
        if (count <= 2)
            return;
        NSAutoreleasePool pool = null;
        if (!NSThread.isMainThread())
            pool = (NSAutoreleasePool) new NSAutoreleasePool().alloc().init();
        try {
            long polyRgn = polyRgn(pointArray, count);
            OS.UnionRgn(handle, polyRgn, handle);
            OS.DisposeRgn(polyRgn);
        } finally {
            if (pool != null)
                pool.release();
        }
    }

    /**
     * Adds the given rectangle to the collection of polygons
     * the receiver maintains to describe its area.
     *
     * @param rect the rectangle to merge with the receiver
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the argument is null</li>
     *    <li>ERROR_INVALID_ARGUMENT - if the rectangle's width or height is negative</li>
     * </ul>
     * @exception SWTException <ul>
     *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
     * </ul>
     */
    public void add(Rectangle rect) {
        if (isDisposed())
            SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
        if (rect == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        if (rect.width < 0 || rect.height < 0)
            SWT.error(SWT.ERROR_INVALID_ARGUMENT);
        NSAutoreleasePool pool = null;
        if (!NSThread.isMainThread())
            pool = (NSAutoreleasePool) new NSAutoreleasePool().alloc().init();
        try {
            add(rect.x, rect.y, rect.width, rect.height);
        } finally {
            if (pool != null)
                pool.release();
        }
    }

    /**
     * Adds the given rectangle to the collection of polygons
     * the receiver maintains to describe its area.
     *
     * @param x the x coordinate of the rectangle
     * @param y the y coordinate of the rectangle
     * @param width the width coordinate of the rectangle
     * @param height the height coordinate of the rectangle
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_INVALID_ARGUMENT - if the rectangle's width or height is negative</li>
     * </ul>
     * @exception SWTException <ul>
     *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
     * </ul>
     *
     * @since 3.1
     */
    public void add(int x, int y, int width, int height) {
        if (isDisposed())
            SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
        if (width < 0 || height < 0)
            SWT.error(SWT.ERROR_INVALID_ARGUMENT);
        NSAutoreleasePool pool = null;
        if (!NSThread.isMainThread())
            pool = (NSAutoreleasePool) new NSAutoreleasePool().alloc().init();
        try {
            long rectRgn = OS.NewRgn();
            short[] r = new short[4];
            OS.SetRect(r, (short) x, (short) y, (short) (x + width), (short) (y + height));
            OS.RectRgn(rectRgn, r);
            OS.UnionRgn(handle, rectRgn, handle);
            OS.DisposeRgn(rectRgn);
        } finally {
            if (pool != null)
                pool.release();
        }
    }

    /**
     * Adds all of the polygons which make up the area covered
     * by the argument to the collection of polygons the receiver
     * maintains to describe its area.
     *
     * @param region the region to merge
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the argument is null</li>
     *    <li>ERROR_INVALID_ARGUMENT - if the argument has been disposed</li>
     * </ul>
     * @exception SWTException <ul>
     *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
     * </ul>
     */
    public void add(Region region) {
        if (isDisposed())
            SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
        if (region == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        if (region.isDisposed())
            SWT.error(SWT.ERROR_INVALID_ARGUMENT);
        NSAutoreleasePool pool = null;
        if (!NSThread.isMainThread())
            pool = (NSAutoreleasePool) new NSAutoreleasePool().alloc().init();
        try {
            OS.UnionRgn(handle, region.handle, handle);
        } finally {
            if (pool != null)
                pool.release();
        }
    }

    /**
     * Returns <code>true</code> if the point specified by the
     * arguments is inside the area specified by the receiver,
     * and <code>false</code> otherwise.
     *
     * @param x the x coordinate of the point to test for containment
     * @param y the y coordinate of the point to test for containment
     * @return <code>true</code> if the region contains the point and <code>false</code> otherwise
     *
     * @exception SWTException <ul>
     *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
     * </ul>
     */
    public boolean contains(int x, int y) {
        if (isDisposed())
            SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
        NSAutoreleasePool pool = null;
        if (!NSThread.isMainThread())
            pool = (NSAutoreleasePool) new NSAutoreleasePool().alloc().init();
        try {
            short[] point = new short[] { (short) y, (short) x };
            return OS.PtInRgn(point, handle);
        } finally {
            if (pool != null)
                pool.release();
        }
    }

    /**
     * Returns <code>true</code> if the given point is inside the
     * area specified by the receiver, and <code>false</code>
     * otherwise.
     *
     * @param pt the point to test for containment
     * @return <code>true</code> if the region contains the point and <code>false</code> otherwise
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the argument is null</li>
     * </ul>
     * @exception SWTException <ul>
     *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
     * </ul>
     */
    public boolean contains(Point pt) {
        if (pt == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        return contains(pt.x, pt.y);
    }

    NSAffineTransform transform;

    void convertRgn(NSAffineTransform transform) {
        long newRgn = OS.NewRgn();
        Callback callback = new Callback(this, "convertRgn", 4);
        long proc = callback.getAddress();
        if (proc == 0)
            SWT.error(SWT.ERROR_NO_MORE_CALLBACKS);
        this.transform = transform;
        OS.QDRegionToRects(handle, OS.kQDParseRegionFromTopLeft, proc, newRgn);
        this.transform = null;
        callback.dispose();
        OS.CopyRgn(newRgn, handle);
        OS.DisposeRgn(newRgn);
    }

    long convertRgn(long message, long rgn, long r, long newRgn) {
        if (message == OS.kQDRegionToRectsMsgParse) {
            short[] rect = new short[4];
            C.memmove(rect, r, rect.length * 2);
            int i = 0;
            NSPoint point = new NSPoint();
            int[] points = new int[10];
            point.x = rect[1];
            point.y = rect[0];
            point = transform.transformPoint(point);
            short startX, startY;
            points[i++] = startX = (short) point.x;
            points[i++] = startY = (short) point.y;
            point.x = rect[3];
            point.y = rect[0];
            point = transform.transformPoint(point);
            points[i++] = (short) Math.round(point.x);
            points[i++] = (short) point.y;
            point.x = rect[3];
            point.y = rect[2];
            point = transform.transformPoint(point);
            points[i++] = (short) Math.round(point.x);
            points[i++] = (short) Math.round(point.y);
            point.x = rect[1];
            point.y = rect[2];
            point = transform.transformPoint(point);
            points[i++] = (short) point.x;
            points[i++] = (short) Math.round(point.y);
            points[i++] = startX;
            points[i++] = startY;
            long polyRgn = polyRgn(points, points.length);
            OS.UnionRgn(newRgn, polyRgn, newRgn);
            OS.DisposeRgn(polyRgn);
        }
        return 0;
    }

    @Override
    void destroy() {
        OS.DisposeRgn(handle);
        handle = 0;
    }

    /**
     * Compares the argument to the receiver, and returns true
     * if they represent the <em>same</em> object using a class
     * specific comparison.
     *
     * @param object the object to compare with this object
     * @return <code>true</code> if the object is the same as this object and <code>false</code> otherwise
     *
     * @see #hashCode
     */
    @Override
    public boolean equals(Object object) {
        if (this == object)
            return true;
        if (!(object instanceof Region))
            return false;
        Region region = (Region) object;
        return handle == region.handle;
    }

    /**
     * Returns a rectangle which represents the rectangular
     * union of the collection of polygons the receiver
     * maintains to describe its area.
     *
     * @return a bounding rectangle for the region
     *
     * @exception SWTException <ul>
     *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
     * </ul>
     *
     * @see Rectangle#union
     */
    public Rectangle getBounds() {
        if (isDisposed())
            SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
        NSAutoreleasePool pool = null;
        if (!NSThread.isMainThread())
            pool = (NSAutoreleasePool) new NSAutoreleasePool().alloc().init();
        try {
            short[] bounds = new short[4];
            OS.GetRegionBounds(handle, bounds);
            int width = bounds[3] - bounds[1];
            int height = bounds[2] - bounds[0];
            return new Rectangle(bounds[1], bounds[0], width, height);
        } finally {
            if (pool != null)
                pool.release();
        }
    }

    NSBezierPath getPath() {
        Callback callback = new Callback(this, "regionToRects", 4);
        if (callback.getAddress() == 0)
            SWT.error(SWT.ERROR_NO_MORE_CALLBACKS);
        NSBezierPath path = NSBezierPath.bezierPath();
        path.retain();
        OS.QDRegionToRects(handle, OS.kQDParseRegionFromTopLeft, callback.getAddress(), path.id);
        callback.dispose();
        if (path.isEmpty())
            path.appendBezierPathWithRect(new NSRect());
        return path;
    }

    NSPoint pt = new NSPoint();
    short[] rect = new short[4];

    long regionToRects(long message, long rgn, long r, long path) {
        if (message == OS.kQDRegionToRectsMsgParse) {
            C.memmove(rect, r, rect.length * 2);
            pt.x = rect[1];
            pt.y = rect[0];
            OS.objc_msgSend(path, OS.sel_moveToPoint_, pt);
            pt.x = rect[3];
            OS.objc_msgSend(path, OS.sel_lineToPoint_, pt);
            pt.x = rect[3];
            pt.y = rect[2];
            OS.objc_msgSend(path, OS.sel_lineToPoint_, pt);
            pt.x = rect[1];
            OS.objc_msgSend(path, OS.sel_lineToPoint_, pt);
            OS.objc_msgSend(path, OS.sel_closePath);
        }
        return 0;
    }

    /**
     * Returns an integer hash code for the receiver. Any two
     * objects that return <code>true</code> when passed to
     * <code>equals</code> must return the same value for this
     * method.
     *
     * @return the receiver's hash
     *
     * @see #equals
     */
    @Override
    public int hashCode() {
        return (int) handle;
    }

    /**
     * Intersects the given rectangle to the collection of polygons
     * the receiver maintains to describe its area.
     *
     * @param rect the rectangle to intersect with the receiver
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the argument is null</li>
     *    <li>ERROR_INVALID_ARGUMENT - if the rectangle's width or height is negative</li>
     * </ul>
     * @exception SWTException <ul>
     *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
     * </ul>
     *
     * @since 3.0
     */
    public void intersect(Rectangle rect) {
        if (isDisposed())
            SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
        if (rect == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        intersect(rect.x, rect.y, rect.width, rect.height);
    }

    /**
     * Intersects the given rectangle to the collection of polygons
     * the receiver maintains to describe its area.
     *
     * @param x the x coordinate of the rectangle
     * @param y the y coordinate of the rectangle
     * @param width the width coordinate of the rectangle
     * @param height the height coordinate of the rectangle
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_INVALID_ARGUMENT - if the rectangle's width or height is negative</li>
     * </ul>
     * @exception SWTException <ul>
     *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
     * </ul>
     *
     * @since 3.1
     */
    public void intersect(int x, int y, int width, int height) {
        if (isDisposed())
            SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
        if (width < 0 || height < 0)
            SWT.error(SWT.ERROR_INVALID_ARGUMENT);
        NSAutoreleasePool pool = null;
        if (!NSThread.isMainThread())
            pool = (NSAutoreleasePool) new NSAutoreleasePool().alloc().init();
        try {
            long rectRgn = OS.NewRgn();
            short[] r = new short[4];
            OS.SetRect(r, (short) x, (short) y, (short) (x + width), (short) (y + height));
            OS.RectRgn(rectRgn, r);
            OS.SectRgn(handle, rectRgn, handle);
            OS.DisposeRgn(rectRgn);
        } finally {
            if (pool != null)
                pool.release();
        }
    }

    /**
     * Intersects all of the polygons which make up the area covered
     * by the argument to the collection of polygons the receiver
     * maintains to describe its area.
     *
     * @param region the region to intersect
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the argument is null</li>
     *    <li>ERROR_INVALID_ARGUMENT - if the argument has been disposed</li>
     * </ul>
     * @exception SWTException <ul>
     *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
     * </ul>
     *
     * @since 3.0
     */
    public void intersect(Region region) {
        if (isDisposed())
            SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
        if (region == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        if (region.isDisposed())
            SWT.error(SWT.ERROR_INVALID_ARGUMENT);
        NSAutoreleasePool pool = null;
        if (!NSThread.isMainThread())
            pool = (NSAutoreleasePool) new NSAutoreleasePool().alloc().init();
        try {
            OS.SectRgn(handle, region.handle, handle);
        } finally {
            if (pool != null)
                pool.release();
        }
    }

    /**
     * Returns <code>true</code> if the rectangle described by the
     * arguments intersects with any of the polygons the receiver
     * maintains to describe its area, and <code>false</code> otherwise.
     *
     * @param x the x coordinate of the origin of the rectangle
     * @param y the y coordinate of the origin of the rectangle
     * @param width the width of the rectangle
     * @param height the height of the rectangle
     * @return <code>true</code> if the rectangle intersects with the receiver, and <code>false</code> otherwise
     *
     * @exception SWTException <ul>
     *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
     * </ul>
     *
     * @see Rectangle#intersects(Rectangle)
     */
    public boolean intersects(int x, int y, int width, int height) {
        if (isDisposed())
            SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
        NSAutoreleasePool pool = null;
        if (!NSThread.isMainThread())
            pool = (NSAutoreleasePool) new NSAutoreleasePool().alloc().init();
        try {
            short[] r = new short[4];
            OS.SetRect(r, (short) x, (short) y, (short) (x + width), (short) (y + height));
            return OS.RectInRgn(r, handle);
        } finally {
            if (pool != null)
                pool.release();
        }
    }

    /**
     * Returns <code>true</code> if the given rectangle intersects
     * with any of the polygons the receiver maintains to describe
     * its area and <code>false</code> otherwise.
     *
     * @param rect the rectangle to test for intersection
     * @return <code>true</code> if the rectangle intersects with the receiver, and <code>false</code> otherwise
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the argument is null</li>
     * </ul>
     * @exception SWTException <ul>
     *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
     * </ul>
     *
     * @see Rectangle#intersects(Rectangle)
     */
    public boolean intersects(Rectangle rect) {
        if (rect == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        return intersects(rect.x, rect.y, rect.width, rect.height);
    }

    /**
     * Returns <code>true</code> if the region has been disposed,
     * and <code>false</code> otherwise.
     * <p>
     * This method gets the dispose state for the region.
     * When a region has been disposed, it is an error to
     * invoke any other method (except {@link #dispose()}) using the region.
     *
     * @return <code>true</code> when the region is disposed, and <code>false</code> otherwise
     */
    @Override
    public boolean isDisposed() {
        return handle == 0;
    }

    /**
     * Returns <code>true</code> if the receiver does not cover any
     * area in the (x, y) coordinate plane, and <code>false</code> if
     * the receiver does cover some area in the plane.
     *
     * @return <code>true</code> if the receiver is empty, and <code>false</code> otherwise
     *
     * @exception SWTException <ul>
     *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
     * </ul>
     */
    public boolean isEmpty() {
        if (isDisposed())
            SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
        NSAutoreleasePool pool = null;
        if (!NSThread.isMainThread())
            pool = (NSAutoreleasePool) new NSAutoreleasePool().alloc().init();
        try {
            return OS.EmptyRgn(handle);
        } finally {
            if (pool != null)
                pool.release();
        }
    }

    /**
     * Subtracts the given polygon from the collection of polygons
     * the receiver maintains to describe its area.
     *
     * @param pointArray points that describe the polygon to merge with the receiver
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the argument is null</li>
     * </ul>
     * @exception SWTException <ul>
     *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
     * </ul>
     *
     * @since 3.0
     */
    public void subtract(int[] pointArray) {
        if (isDisposed())
            SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
        if (pointArray == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        if (pointArray.length < 2)
            return;
        NSAutoreleasePool pool = null;
        if (!NSThread.isMainThread())
            pool = (NSAutoreleasePool) new NSAutoreleasePool().alloc().init();
        try {
            long polyRgn = polyRgn(pointArray, pointArray.length);
            OS.DiffRgn(handle, polyRgn, handle);
            OS.DisposeRgn(polyRgn);
        } finally {
            if (pool != null)
                pool.release();
        }
    }

    /**
     * Subtracts the given rectangle from the collection of polygons
     * the receiver maintains to describe its area.
     *
     * @param rect the rectangle to subtract from the receiver
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the argument is null</li>
     *    <li>ERROR_INVALID_ARGUMENT - if the rectangle's width or height is negative</li>
     * </ul>
     * @exception SWTException <ul>
     *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
     * </ul>
     *
     * @since 3.0
     */
    public void subtract(Rectangle rect) {
        if (isDisposed())
            SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
        if (rect == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        subtract(rect.x, rect.y, rect.width, rect.height);
    }

    /**
     * Subtracts the given rectangle from the collection of polygons
     * the receiver maintains to describe its area.
     *
     * @param x the x coordinate of the rectangle
     * @param y the y coordinate of the rectangle
     * @param width the width coordinate of the rectangle
     * @param height the height coordinate of the rectangle
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_INVALID_ARGUMENT - if the rectangle's width or height is negative</li>
     * </ul>
     * @exception SWTException <ul>
     *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
     * </ul>
     *
     * @since 3.1
     */
    public void subtract(int x, int y, int width, int height) {
        if (isDisposed())
            SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
        if (width < 0 || height < 0)
            SWT.error(SWT.ERROR_INVALID_ARGUMENT);
        NSAutoreleasePool pool = null;
        if (!NSThread.isMainThread())
            pool = (NSAutoreleasePool) new NSAutoreleasePool().alloc().init();
        try {
            long rectRgn = OS.NewRgn();
            short[] r = new short[4];
            OS.SetRect(r, (short) x, (short) y, (short) (x + width), (short) (y + height));
            OS.RectRgn(rectRgn, r);
            OS.DiffRgn(handle, rectRgn, handle);
            OS.DisposeRgn(rectRgn);
        } finally {
            if (pool != null)
                pool.release();
        }
    }

    /**
     * Subtracts all of the polygons which make up the area covered
     * by the argument from the collection of polygons the receiver
     * maintains to describe its area.
     *
     * @param region the region to subtract
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the argument is null</li>
     *    <li>ERROR_INVALID_ARGUMENT - if the argument has been disposed</li>
     * </ul>
     * @exception SWTException <ul>
     *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
     * </ul>
     *
     * @since 3.0
     */
    public void subtract(Region region) {
        if (isDisposed())
            SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
        if (region == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        if (region.isDisposed())
            SWT.error(SWT.ERROR_INVALID_ARGUMENT);
        NSAutoreleasePool pool = null;
        if (!NSThread.isMainThread())
            pool = (NSAutoreleasePool) new NSAutoreleasePool().alloc().init();
        try {
            OS.DiffRgn(handle, region.handle, handle);
        } finally {
            if (pool != null)
                pool.release();
        }
    }

    /**
     * Translate all of the polygons the receiver maintains to describe
     * its area by the specified point.
     *
     * @param x the x coordinate of the point to translate
     * @param y the y coordinate of the point to translate
     *
     * @exception SWTException <ul>
     *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
     * </ul>
     *
     * @since 3.1
     */
    public void translate(int x, int y) {
        if (isDisposed())
            SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
        NSAutoreleasePool pool = null;
        if (!NSThread.isMainThread())
            pool = (NSAutoreleasePool) new NSAutoreleasePool().alloc().init();
        try {
            OS.OffsetRgn(handle, (short) x, (short) y);
        } finally {
            if (pool != null)
                pool.release();
        }
    }

    /**
     * Translate all of the polygons the receiver maintains to describe
     * its area by the specified point.
     *
     * @param pt the point to translate
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the argument is null</li>
     * </ul>
     * @exception SWTException <ul>
     *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
     * </ul>
     *
     * @since 3.1
     */
    public void translate(Point pt) {
        if (isDisposed())
            SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
        if (pt == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        NSAutoreleasePool pool = null;
        if (!NSThread.isMainThread())
            pool = (NSAutoreleasePool) new NSAutoreleasePool().alloc().init();
        try {
            translate(pt.x, pt.y);
        } finally {
            if (pool != null)
                pool.release();
        }
    }

    /**
     * Returns a string containing a concise, human-readable
     * description of the receiver.
     *
     * @return a string representation of the receiver
     */
    @Override
    public String toString() {
        if (isDisposed())
            return "Region {*DISPOSED*}";
        return "Region {" + handle + "}";
    }
}