/*******************************************************************************
* Copyright (c) 2000, 2008 IBM Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-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
* @see <a href="http://www.eclipse.org/swt/">Sample code and further information</a>
*
* @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.
* <p>
* 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.
* </p>
*
* <br>Possible values are: <ul>
* <li>{@link SWT#TOP}: Attach the side to the top side of the specified control.</li>
* <li>{@link SWT#BOTTOM}: Attach the side to the bottom side of the specified control.</li>
* <li>{@link SWT#LEFT}: Attach the side to the left side of the specified control.</li>
* <li>{@link SWT#RIGHT}: Attach the side to the right side of the specified control.</li>
* <li>{@link SWT#CENTER}: Attach the side at a position which will center the control on the specified control.</li>
* <li>{@link SWT#DEFAULT}: Attach the side to the adjacent side of the specified control.</li>
* </ul>
*/
public int alignment;
/**
* Constructs a new instance of this class.
* Since no numerator, denominator or offset is specified,
* the attachment is treated as a percentage of the form.
* The numerator is zero, the denominator is 100 and the
* offset is zero.
*
* @since 3.2
*/
public 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
*
* @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. The possible alignment values are:
* <dl>
* <dt><b>{@link SWT#TOP}</b></dt>
* <dd>the side will be attached to the top side of the specified control</dd>
* <dt><b>{@link SWT#BOTTOM}</b></dt>
* <dd>the side will be attached to the bottom side of the specified control</dd>
* <dt><b>{@link SWT#LEFT}</b></dt>
* <dd>the side will be attached to the left side of the specified control</dd>
* <dt><b>{@link SWT#RIGHT}</b></dt>
* <dd>the side will be attached to the right side of the specified control</dd>
* <dt><b>{@link SWT#CENTER}</b></dt>
* <dd>the side will be centered on the same side of the specified control</dd>
* <dt><b>{@link SWT#DEFAULT}</b></dt>
* <dd>the side will be attached to the adjacent side of the specified control</dd>
* </dl>
*
* @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,
* one of TOP, BOTTOM, LEFT, RIGHT, CENTER, or DEFAULT
*/
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;
}
/**
* Returns a string containing a concise, human-readable
* description of the receiver.
*
* @return a string representation of the FormAttachment
*/
@Override
public String toString () {
String string = control != null ? control.toString () : numerator + "/" + denominator;
return "{y = (" + string + (offset >= 0 ? ")x + " + offset: ")x - " + (-offset))+"}";
}
}