/******************************************************************************* * Copyright (c) 2000, 2004 IBM Corporation and others. * All rights reserved. This program and the accompanying materials * are made available under the terms of the Common Public License v1.0 * which accompanies this distribution, and is available at * http://www.eclipse.org/legal/cpl-v10.html *  * Contributors: *     IBM Corporation - initial API and implementation *******************************************************************************/package org.eclipse.swt.layout;import org.eclipse.swt.*;import org.eclipse.swt.widgets.*;/** * Instances of this class are used to define the edges of a control * within a <code>FormLayout</code>.  * <p> * <code>FormAttachments</code> are set into the top, bottom, left, * and right fields of the <code>FormData</code> for a control. * For example: * <pre> * 		FormData data = new FormData(); * 		data.top = new FormAttachment(0,5); * 		data.bottom = new FormAttachment(100,-5); * 		data.left = new FormAttachment(0,5); * 		data.right = new FormAttachment(100,-5); * 		button.setLayoutData(data); * </pre> * </p> * <p> * A <code>FormAttachment</code> defines where to attach the side of * a control by using the equation, y = ax + b. The "a" term represents  * a fraction of the parent composite's width (from the left) or height * (from the top). It can be defined using a numerator and denominator, * or just a percentage value. If a percentage is used, the denominator  * is set to 100. The "b" term in the equation represents an offset, in * pixels, from the attachment position. For example: * <pre> * 		FormAttachment attach = new FormAttachment (20, -5); * </pre> * specifies that the side to which the <code>FormAttachment</code> * object belongs will lie at 20% of the parent composite, minus 5 pixels. * </p> * <p> * Control sides can also be attached to another control. * For example: * <pre> * 		FormAttachment attach = new FormAttachment (button, 10); * </pre> * specifies that the side to which the <code>FormAttachment</code> * object belongs will lie in the same position as the adjacent side of  * the <code>button</code> control, plus 10 pixels. The control side can  * also be attached to the opposite side of the specified control. * For example: * <pre> * 		FormData data = new FormData (); * 		data.left = new FormAttachment (button, 0, SWT.LEFT); * </pre> * specifies that the left side of the control will lie in the same position * as the left side of the <code>button</code> control. The control can also  * be attached in a position that will center the control on the specified  * control. For example: * <pre> * 		data.left = new FormAttachment (button, 0, SWT.CENTER); * </pre> * specifies that the left side of the control will be positioned so that it is * centered between the left and right sides of the <code>button</code> control. * If the alignment is not specified, the default is to attach to the adjacent side. * </p> *  * @see FormLayout * @see FormData *  * @since 2.0 */public final class FormAttachment {	/**	 * numerator specifies the numerator of the "a" term in the	 * equation, y = ax + b, which defines the attachment.	 */	public int numerator;	/**	 * denominator specifies the denominator of the "a" term in the	 * equation, y = ax + b, which defines the attachment.	 * 	 * The default value is 100.	 */	public int denominator = 100;	/**	 * offset specifies the offset, in pixels, of the control side	 * from the attachment position.	 * If the offset is positive, then the control side is offset	 * to the right of or below the attachment position. If it is	 * negative, then the control side is offset to the left of or	 * above the attachment position.	 * 	 * This is equivalent to the "b" term in the equation y = ax + b.	 * The default value is 0.	 */	public int offset;	/**	 * control specifies the control to which the control side is	 * attached.	 */	public Control control;	/**	 * alignment specifies the alignment of the control side that is	 * attached to a control.	 * For top and bottom attachments, TOP, BOTTOM and CENTER are used. For left 	 * and right attachments, LEFT, RIGHT and CENTER are used. If any other case	 * occurs, the default will be used instead.	 * 	 * Possible values are:	 * 	 * TOP: Attach the side to the top side of the specified control.	 * BOTTOM : Attach the side to the bottom side of the specified control.	 * LEFT: Attach the side to the left side of the specified control.	 * RIGHT: Attach the side to the right side of the specified control.	 * CENTER: Attach the side at a position which will center the control on	 * the specified control.	 * DEFAULT: Attach the side to the adjacent side of the specified control.	 */	public int alignment;	FormAttachment () {}/** * Constructs a new instance of this class given a numerator * Since no denominator or offset is specified, the default * is to treat the numerator as a percentage of the form, with a  * denominator of 100. The offset is zero. *  * @param numerator the percentage of the position * @param offset the offset of the side from the position *  * @since 3.0 */public FormAttachment (int numerator) {	this (numerator, 100, 0);}/** * Constructs a new instance of this class given a numerator * and an offset. Since no denominator is specified, the default * is to treat the numerator as a percentage of the form, with a  * denominator of 100. *  * @param numerator the percentage of the position * @param offset the offset of the side from the position */public FormAttachment (int numerator, int offset) {	this (numerator, 100, offset);}/** * Constructs a new instance of this class given a numerator  * and denominator and an offset. The position of the side is * given by the fraction of the form defined by the numerator * and denominator. * * @param numerator the numerator of the position * @param denominator the denominator of the position * @param offset the offset of the side from the position */public FormAttachment (int numerator, int denominator, int offset) {	if (denominator == 0) SWT.error (SWT.ERROR_CANNOT_BE_ZERO);	this.numerator = numerator;	this.denominator = denominator;	this.offset = offset;}/** * Constructs a new instance of this class given a control. * Since no alignment is specified, the default alignment is * to attach the side to the adjacent side of the specified  * control. Since no offset is specified, an offset of 0 is * used. *  * @param control the control the side is attached to */public FormAttachment (Control control) {	this (control, 0, SWT.DEFAULT);}/** * Constructs a new instance of this class given a control * and an offset. Since no alignment is specified, the default * alignment is to attach the side to the adjacent side of the  * specified control. *  * @param control the control the side is attached to * @param offset the offset of the side from the control */public FormAttachment (Control control, int offset) {	this (control, offset, SWT.DEFAULT);}/** * Constructs a new instance of this class given a control, * an offset and an alignment. *  * @param control the control the side is attached to * @param offset the offset of the side from the control * @param alignment the alignment of the side to the control it is attached to */public FormAttachment (Control control, int offset, int alignment) {	this.control = control;	this.offset = offset;	this.alignment = alignment;}FormAttachment divide (int value) {	return new FormAttachment (numerator, denominator * value, offset / value);}int gcd (int m, int n) {	int temp;	m = Math.abs (m);	n = Math.abs (n);	if (m < n) {		temp = m;		m = n;		n = temp;	}	while (n != 0){		temp = m;		m = n;		n = temp % n;	}	return m;}FormAttachment minus (FormAttachment attachment) {	FormAttachment solution = new FormAttachment ();	solution.numerator = numerator * attachment.denominator - denominator * attachment.numerator;	solution.denominator = denominator * attachment.denominator;	int gcd = gcd (solution.denominator, solution.numerator);	solution.numerator = solution.numerator / gcd;	solution.denominator = solution.denominator / gcd;	solution.offset = offset - attachment.offset;	return solution;}FormAttachment minus (int value) {	return new FormAttachment (numerator, denominator, offset - value);}FormAttachment plus (FormAttachment attachment) {	FormAttachment solution = new FormAttachment ();	solution.numerator = numerator * attachment.denominator + denominator * attachment.numerator;	solution.denominator = denominator * attachment.denominator;	int gcd = gcd (solution.denominator, solution.numerator);	solution.numerator = solution.numerator / gcd;	solution.denominator = solution.denominator / gcd;	solution.offset = offset + attachment.offset;	return solution;}FormAttachment plus (int value) {	return new FormAttachment (numerator, denominator, offset + value);}int solveX (int value) {	if (denominator == 0) SWT.error (SWT.ERROR_CANNOT_BE_ZERO);	return ((numerator * value) / denominator) + offset;}int solveY (int value) {	if (numerator == 0) SWT.error (SWT.ERROR_CANNOT_BE_ZERO);	return (value - offset) * denominator / numerator;}	public String toString () { 	String string = control != null ? control.toString () : numerator + "/" + denominator;	return "y = (" + string + (offset >= 0 ? ")x + " + offset: ")x - " + (-offset));}}