swt/graphics/Path.java

/*******************************************************************************
 * Copyright (c) 2000, 2018 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.gdip.*;
import org.eclipse.swt.internal.win32.*;

/**
 * Instances of this class represent paths through the two-dimensional
 * coordinate system. Paths do not have to be continuous, and can be
 * described using lines, rectangles, arcs, cubic or quadratic bezier curves,
 * glyphs, or other paths.
 * <p>
 * Application code must explicitly invoke the <code>Path.dispose()</code>
 * method to release the operating system resources managed by each instance
 * when those instances are no longer required.
 * </p>
 * <p>
 * This class requires the operating system's advanced graphics subsystem
 * which may not be available on some platforms.
 * </p>
 *
 * @see <a href="http://www.eclipse.org/swt/snippets/#path">Path, Pattern snippets</a>
 * @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>
 *
 * @since 3.1
 */
public class Path extends Resource {

	/**
	 * the OS resource for the Path
	 * (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;

	PointF currentPoint = new PointF(), startPoint = new PointF();

/**
 * Constructs a new empty Path.
 * <p>
 * This operation requires the operating system's advanced
 * graphics subsystem which may not be available on some
 * platforms.
 * </p>
 * <p>
 * You must dispose the path when it is no longer required.
 * </p>
 *
 * @param device the device on which to allocate the path
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the device is null and there is no current device</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_NO_GRAPHICS_LIBRARY - if advanced graphics are not available</li>
 * </ul>
 * @exception SWTError <ul>
 *    <li>ERROR_NO_HANDLES if a handle for the path could not be obtained</li>
 * </ul>
 *
 * @see #dispose()
 */
public Path (Device device) {
	super(device);
	this.device.checkGDIP();
	handle = Gdip.GraphicsPath_new(Gdip.FillModeAlternate);
	if (handle == 0) SWT.error(SWT.ERROR_NO_HANDLES);
	init();
}

/**
 * Constructs a new Path that is a copy of <code>path</code>. If
 * <code>flatness</code> is less than or equal to zero, an unflatten
 * copy of the path is created. Otherwise, it specifies the maximum
 * error between the path and its flatten copy. Smaller numbers give
 * better approximation.
 * <p>
 * This operation requires the operating system's advanced
 * graphics subsystem which may not be available on some
 * platforms.
 * </p>
 * <p>
 * You must dispose the path when it is no longer required.
 * </p>
 *
 * @param device the device on which to allocate the path
 * @param path the path to make a copy
 * @param flatness the flatness value
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the device is null and there is no current device</li>
 *    <li>ERROR_NULL_ARGUMENT - if the path is null</li>
 *    <li>ERROR_INVALID_ARGUMENT - if the path has been disposed</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_NO_GRAPHICS_LIBRARY - if advanced graphics are not available</li>
 * </ul>
 * @exception SWTError <ul>
 *    <li>ERROR_NO_HANDLES if a handle for the path could not be obtained</li>
 * </ul>
 *
 * @see #dispose()
 * @since 3.4
 */
public Path (Device device, Path path, float flatness) {
	super(device);
	if (path == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
	if (path.isDisposed()) SWT.error(SWT.ERROR_INVALID_ARGUMENT);
	flatness = Math.max(0, flatness);
	handle = Gdip.GraphicsPath_Clone(path.handle);
	if (flatness != 0) Gdip.GraphicsPath_Flatten(handle, 0, flatness);
	if (handle == 0) SWT.error(SWT.ERROR_NO_HANDLES);
	init();
}

/**
 * Constructs a new Path with the specified PathData.
 * <p>
 * This operation requires the operating system's advanced
 * graphics subsystem which may not be available on some
 * platforms.
 * </p>
 * <p>
 * You must dispose the path when it is no longer required.
 * </p>
 *
 * @param device the device on which to allocate the path
 * @param data the data for the path
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the device is null and there is no current device</li>
 *    <li>ERROR_NULL_ARGUMENT - if the data is null</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_NO_GRAPHICS_LIBRARY - if advanced graphics are not available</li>
 * </ul>
 * @exception SWTError <ul>
 *    <li>ERROR_NO_HANDLES if a handle for the path could not be obtained</li>
 * </ul>
 *
 * @see #dispose()
 * @since 3.4
 */
public Path (Device device, PathData data) {
	this(device);
	if (data == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
	init(data);
}

/**
 * Adds to the receiver a circular or elliptical arc that lies within
 * the specified rectangular area.
 * <p>
 * The resulting arc begins at <code>startAngle</code> and extends
 * for <code>arcAngle</code> degrees.
 * Angles are interpreted such that 0 degrees is at the 3 o'clock
 * position. A positive value indicates a counter-clockwise rotation
 * while a negative value indicates a clockwise rotation.
 * </p><p>
 * The center of the arc is the center of the rectangle whose origin
 * is (<code>x</code>, <code>y</code>) and whose size is specified by the
 * <code>width</code> and <code>height</code> arguments.
 * </p><p>
 * The resulting arc covers an area <code>width + 1</code> points wide
 * by <code>height + 1</code> points tall.
 * </p>
 *
 * @param x the x coordinate of the upper-left corner of the arc
 * @param y the y coordinate of the upper-left corner of the arc
 * @param width the width of the arc
 * @param height the height of the arc
 * @param startAngle the beginning angle
 * @param arcAngle the angular extent of the arc, relative to the start angle
 *
 * @exception SWTException <ul>
 *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
 * </ul>
 */
public void addArc (float x, float y, float width, float height, float startAngle, float arcAngle) {
	x = DPIUtil.autoScaleUp(x);
	y = DPIUtil.autoScaleUp(y);
	width = DPIUtil.autoScaleUp(width);
	height = DPIUtil.autoScaleUp(height);
	addArcInPixels(x, y, width, height, startAngle, arcAngle);
}

void addArcInPixels(float x, float y, float width, float height, float startAngle, float arcAngle) {
	if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
	if (width < 0) {
		x = x + width;
		width = -width;
	}
	if (height < 0) {
		y = y + height;
		height = -height;
	}
	if (width == 0 || height == 0 || arcAngle == 0) return;
	if (width == height) {
		Gdip.GraphicsPath_AddArc(handle, x, y, width, height, -startAngle, -arcAngle);
	} else {
		long path = Gdip.GraphicsPath_new(Gdip.FillModeAlternate);
		if (path == 0) SWT.error(SWT.ERROR_NO_HANDLES);
		long matrix = Gdip.Matrix_new(width, 0, 0, height, x, y);
		if (matrix == 0) SWT.error(SWT.ERROR_NO_HANDLES);
		Gdip.GraphicsPath_AddArc(path, 0, 0, 1, 1, -startAngle, -arcAngle);
		Gdip.GraphicsPath_Transform(path, matrix);
		Gdip.GraphicsPath_AddPath(handle, path, true);
		Gdip.Matrix_delete(matrix);
		Gdip.GraphicsPath_delete(path);
	}
	Gdip.GraphicsPath_GetLastPoint(handle, currentPoint);
}

/**
 * Adds to the receiver the path described by the parameter.
 *
 * @param path the path to add to the receiver
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the parameter is null</li>
 *    <li>ERROR_INVALID_ARGUMENT - if the parameter has been disposed</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
 * </ul>
 */
public void addPath(Path path) {
	if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
	if (path == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
	if (path.isDisposed()) SWT.error(SWT.ERROR_INVALID_ARGUMENT);
	//TODO - expose connect?
	Gdip.GraphicsPath_AddPath(handle, path.handle, false);
	currentPoint.X = path.currentPoint.X;
	currentPoint.Y = path.currentPoint.Y;
}

/**
 * Adds to the receiver the rectangle specified by x, y, width and height.
 *
 * @param x the x coordinate of the rectangle to add
 * @param y the y coordinate of the rectangle to add
 * @param width the width of the rectangle to add
 * @param height the height of the rectangle to add
 *
 * @exception SWTException <ul>
 *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
 * </ul>
 */
public void addRectangle (float x, float y, float width, float height) {
	x = DPIUtil.autoScaleUp(x);
	y = DPIUtil.autoScaleUp(y);
	width = DPIUtil.autoScaleUp(width);
	height = DPIUtil.autoScaleUp(height);
	addRectangleInPixels(x, y, width, height);
}

void addRectangleInPixels(float x, float y, float width, float height) {
	if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
	RectF rect = new RectF();
	rect.X = x;
	rect.Y = y;
	rect.Width = width;
	rect.Height = height;
	Gdip.GraphicsPath_AddRectangle(handle, rect);
	currentPoint.X = x;
	currentPoint.Y = y;
}

/**
 * Adds to the receiver the pattern of glyphs generated by drawing
 * the given string using the given font starting at the point (x, y).
 *
 * @param string the text to use
 * @param x the x coordinate of the starting point
 * @param y the y coordinate of the starting point
 * @param font the font to use
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the font is null</li>
 *    <li>ERROR_INVALID_ARGUMENT - if the font has been disposed</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
 * </ul>
 */
public void addString (String string, float x, float y, Font font) {
	x = DPIUtil.autoScaleUp(x);
	y = DPIUtil.autoScaleUp(y);
	addStringInPixels(string, x, y, font);
}

void addStringInPixels(String string, float x, float y, Font font) {
	if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
	if (font == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
	if (font.isDisposed()) SWT.error(SWT.ERROR_INVALID_ARGUMENT);
	char[] buffer = string.toCharArray();
	long hDC = device.internal_new_GC(null);
	long [] family = new long [1];
	long gdipFont = GC.createGdipFont(hDC, font.handle, 0, device.fontCollection, family, null);
	PointF point = new PointF();
	point.X = x - (Gdip.Font_GetSize(gdipFont) / 6);
	point.Y = y;
	int style = Gdip.Font_GetStyle(gdipFont);
	float size = Gdip.Font_GetSize(gdipFont);
	Gdip.GraphicsPath_AddString(handle, buffer, buffer.length, family[0], style, size, point, 0);
	Gdip.GraphicsPath_GetLastPoint(handle, currentPoint);
	Gdip.FontFamily_delete(family[0]);
	Gdip.Font_delete(gdipFont);
	device.internal_dispose_GC(hDC, null);
}

/**
 * Closes the current sub path by adding to the receiver a line
 * from the current point of the path back to the starting point
 * of the sub path.
 *
 * @exception SWTException <ul>
 *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
 * </ul>
 */
public void close() {
	if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
	Gdip.GraphicsPath_CloseFigure(handle);
	/*
	* Feature in GDI+. CloseFigure() does affect the last
	* point, so GetLastPoint() does not return the starting
	* point of the subpath after calling CloseFigure().  The
	* fix is to remember the subpath starting point and use
	* it instead.
	*/
	currentPoint.X = startPoint.X;
	currentPoint.Y = startPoint.Y;
}

/**
 * Returns <code>true</code> if the specified point is contained by
 * the receiver and false otherwise.
 * <p>
 * If outline is <code>true</code>, the point (x, y) checked for containment in
 * the receiver's outline. If outline is <code>false</code>, the point is
 * checked to see if it is contained within the bounds of the (closed) area
 * covered by the receiver.
 *
 * @param x the x coordinate of the point to test for containment
 * @param y the y coordinate of the point to test for containment
 * @param gc the GC to use when testing for containment
 * @param outline controls whether to check the outline or contained area of the path
 * @return <code>true</code> if the path contains the point and <code>false</code> otherwise
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the gc is null</li>
 *    <li>ERROR_INVALID_ARGUMENT - if the gc has been disposed</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
 * </ul>
 */
public boolean contains (float x, float y, GC gc, boolean outline) {
	x = DPIUtil.autoScaleUp(x);
	y = DPIUtil.autoScaleUp(y);
	return containsInPixels(x, y, gc, outline);
}

boolean containsInPixels(float x, float y, GC gc, boolean outline) {
	if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
	if (gc == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
	if (gc.isDisposed()) SWT.error(SWT.ERROR_INVALID_ARGUMENT);
	//TODO - should use GC transformation
	gc.initGdip();
	gc.checkGC(GC.LINE_CAP | GC.LINE_JOIN | GC.LINE_STYLE | GC.LINE_WIDTH);
	int mode = OS.GetPolyFillMode(gc.handle) == OS.WINDING ? Gdip.FillModeWinding : Gdip.FillModeAlternate;
	Gdip.GraphicsPath_SetFillMode(handle, mode);
	if (outline) {
		return Gdip.GraphicsPath_IsOutlineVisible(handle, x, y, gc.data.gdipPen, gc.data.gdipGraphics);
	} else {
		return Gdip.GraphicsPath_IsVisible(handle, x, y, gc.data.gdipGraphics);
	}
}

/**
 * Adds to the receiver a cubic bezier curve based on the parameters.
 *
 * @param cx1 the x coordinate of the first control point of the spline
 * @param cy1 the y coordinate of the first control of the spline
 * @param cx2 the x coordinate of the second control of the spline
 * @param cy2 the y coordinate of the second control of the spline
 * @param x the x coordinate of the end point of the spline
 * @param y the y coordinate of the end point of the spline
 *
 * @exception SWTException <ul>
 *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
 * </ul>
 */
public void cubicTo (float cx1, float cy1, float cx2, float cy2, float x, float y) {
	cx1 = DPIUtil.autoScaleUp(cx1);
	cy1 = DPIUtil.autoScaleUp(cy1);
	cx2 = DPIUtil.autoScaleUp(cx2);
	cy2 = DPIUtil.autoScaleUp(cy2);
	x = DPIUtil.autoScaleUp(x);
	y = DPIUtil.autoScaleUp(y);
	cubicToInPixels(cx1, cy1, cx2, cy2, x, y);
}

void cubicToInPixels(float cx1, float cy1, float cx2, float cy2, float x, float y) {
	if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
	Gdip.GraphicsPath_AddBezier(handle, currentPoint.X, currentPoint.Y, cx1, cy1, cx2, cy2, x, y);
	Gdip.GraphicsPath_GetLastPoint(handle, currentPoint);
}

@Override
void destroy() {
	Gdip.GraphicsPath_delete(handle);
	handle = 0;
}

/**
 * Replaces the first four elements in the parameter with values that
 * describe the smallest rectangle that will completely contain the
 * receiver (i.e. the bounding box).
 *
 * @param bounds the array to hold the result
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the parameter is null</li>
 *    <li>ERROR_INVALID_ARGUMENT - if the parameter is too small to hold the bounding box</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
 * </ul>
 */
public void getBounds (float[] bounds) {
	if (bounds == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
	getBoundsInPixels(bounds);
	bounds = DPIUtil.autoScaleDown(bounds);
}

void getBoundsInPixels(float[] bounds) {
	if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
	if (bounds.length < 4) SWT.error(SWT.ERROR_INVALID_ARGUMENT);
	RectF rect = new RectF();
	Gdip.GraphicsPath_GetBounds(handle, rect, 0, 0);
	bounds[0] = rect.X;
	bounds[1] = rect.Y;
	bounds[2] = rect.Width;
	bounds[3] = rect.Height;
}

/**
 * Replaces the first two elements in the parameter with values that
 * describe the current point of the path.
 *
 * @param point the array to hold the result
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the parameter is null</li>
 *    <li>ERROR_INVALID_ARGUMENT - if the parameter is too small to hold the end point</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
 * </ul>
 */
public void getCurrentPoint (float[] point) {
	if (point == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
	getCurrentPointInPixels(point);
	point = DPIUtil.autoScaleDown(point);
}

void getCurrentPointInPixels(float[] point) {
	if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
	if (point.length < 2) SWT.error(SWT.ERROR_INVALID_ARGUMENT);
	point[0] = currentPoint.X;
	point[1] = currentPoint.Y;
}

/**
 * Returns a device independent representation of the receiver.
 *
 * @return the PathData for the receiver
 *
 * @exception SWTException <ul>
 *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
 * </ul>
 *
 * @see PathData
 */
public PathData getPathData() {
	if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
	PathData result = getPathDataInPixels();
	result.points = DPIUtil.autoScaleDown(result.points);
	return result;
}

PathData getPathDataInPixels() {
	int count = Gdip.GraphicsPath_GetPointCount(handle);
	byte[] gdipTypes = new byte[count];
	float[] points = new float[count * 2];
	Gdip.GraphicsPath_GetPathTypes(handle, gdipTypes, count);
	Gdip.GraphicsPath_GetPathPoints(handle, points, count);
	byte[] types = new byte[count * 2];
	int index = 0, typesIndex = 0;
	while (index < count) {
		byte type = gdipTypes[index];
		boolean close = false;
		switch (type & Gdip.PathPointTypePathTypeMask) {
			case Gdip.PathPointTypeStart:
				types[typesIndex++] = SWT.PATH_MOVE_TO;
				close = (type & Gdip.PathPointTypeCloseSubpath) != 0;
				index += 1;
				break;
			case Gdip.PathPointTypeLine:
				types[typesIndex++] = SWT.PATH_LINE_TO;
				close = (type & Gdip.PathPointTypeCloseSubpath) != 0;
				index += 1;
				break;
			case Gdip.PathPointTypeBezier:
				types[typesIndex++] = SWT.PATH_CUBIC_TO;
				close = (gdipTypes[index + 2] & Gdip.PathPointTypeCloseSubpath) != 0;
				index += 3;
				break;
			default:
				index++;
		}
		if (close) {
			types[typesIndex++] = SWT.PATH_CLOSE;
		}
	}
	if (typesIndex != types.length) {
		byte[] newTypes = new byte[typesIndex];
		System.arraycopy(types, 0, newTypes, 0, typesIndex);
		types = newTypes;
	}
	PathData result = new PathData();
	result.types = types;
	result.points = points;
	return result;
}

/**
 * Adds to the receiver a line from the current point to
 * the point specified by (x, y).
 *
 * @param x the x coordinate of the end of the line to add
 * @param y the y coordinate of the end of the line to add
 *
 * @exception SWTException <ul>
 *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
 * </ul>
 */
public void lineTo (float x, float y) {
	lineToInPixels(DPIUtil.autoScaleUp(x), DPIUtil.autoScaleUp(y));
}

void lineToInPixels(float x, float y) {
	if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
	Gdip.GraphicsPath_AddLine(handle, currentPoint.X, currentPoint.Y, x, y);
	Gdip.GraphicsPath_GetLastPoint(handle, currentPoint);
}

void init(PathData data) {
	byte[] types = data.types;
	float[] points = data.points;
	for (int i = 0, j = 0; i < types.length; i++) {
		switch (types[i]) {
			case SWT.PATH_MOVE_TO:
				moveTo(points[j++], points[j++]);
				break;
			case SWT.PATH_LINE_TO:
				lineTo(points[j++], points[j++]);
				break;
			case SWT.PATH_CUBIC_TO:
				cubicTo(points[j++], points[j++], points[j++], points[j++], points[j++], points[j++]);
				break;
			case SWT.PATH_QUAD_TO:
				quadTo(points[j++], points[j++], points[j++], points[j++]);
				break;
			case SWT.PATH_CLOSE:
				close();
				break;
			default:
				dispose();
				SWT.error(SWT.ERROR_INVALID_ARGUMENT);
		}
	}
}

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

/**
 * Sets the current point of the receiver to the point
 * specified by (x, y). Note that this starts a new
 * sub path.
 *
 * @param x the x coordinate of the new end point
 * @param y the y coordinate of the new end point
 *
 * @exception SWTException <ul>
 *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
 * </ul>
 */
public void moveTo (float x, float y) {
	moveToInPixels(DPIUtil.autoScaleUp(x), DPIUtil.autoScaleUp(y));
}

void moveToInPixels(float x, float y) {
	if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
	Gdip.GraphicsPath_StartFigure(handle);
	currentPoint.X = startPoint.X = x;
	currentPoint.Y = startPoint.Y = y;
}

/**
 * Adds to the receiver a quadratic curve based on the parameters.
 *
 * @param cx the x coordinate of the control point of the spline
 * @param cy the y coordinate of the control point of the spline
 * @param x the x coordinate of the end point of the spline
 * @param y the y coordinate of the end point of the spline
 *
 * @exception SWTException <ul>
 *    <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
 * </ul>
 */
public void quadTo (float cx, float cy, float x, float y) {
	cx = DPIUtil.autoScaleUp(cx);
	cy = DPIUtil.autoScaleUp(cy);
	x = DPIUtil.autoScaleUp(x);
	y = DPIUtil.autoScaleUp(y);
	quadToInPixels(cx, cy, x, y);
}

void quadToInPixels(float cx, float cy, float x, float y) {
	if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
	float cx1 = currentPoint.X + 2 * (cx - currentPoint.X) / 3;
	float cy1 = currentPoint.Y + 2 * (cy - currentPoint.Y) / 3;
	float cx2 = cx1 + (x - currentPoint.X) / 3;
	float cy2 = cy1 + (y - currentPoint.Y) / 3;
	Gdip.GraphicsPath_AddBezier(handle, currentPoint.X, currentPoint.Y, cx1, cy1, cx2, cy2, x, y);
	Gdip.GraphicsPath_GetLastPoint(handle, currentPoint);
}

/**
 * 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 "Path {*DISPOSED*}";
	return "Path {" + handle + "}";
}

}