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Diffstat (limited to 'bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/events/TraverseEvent.java')
| -rwxr-xr-x | bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/events/TraverseEvent.java | 137 |
1 files changed, 137 insertions, 0 deletions
diff --git a/bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/events/TraverseEvent.java b/bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/events/TraverseEvent.java new file mode 100755 index 0000000000..f50e42ab2a --- /dev/null +++ b/bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/events/TraverseEvent.java @@ -0,0 +1,137 @@ +/******************************************************************************* + * 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.events; + + +import org.eclipse.swt.widgets.*; + +/** + * Instances of this class are sent as a result of + * widget traversal actions. + * <p> + * The traversal event allows fine control over keyboard traversal + * in a control both to implement traversal and override the default + * traversal behavior defined by the system. This is achieved using + * two fields, <code>detail</code> and <code>doit</code>. + * </p><p> + * When a control is traversed, a traverse event is sent. The detail + * describes the type of traversal and the doit field indicates the default + * behavior of the system. For example, when a right arrow key is pressed + * in a text control, the detail field is <code>TRAVERSE_ARROW_NEXT</code> + * and the doit field is <code>false</code>, indicating that the system + * will not traverse to the next tab item and the arrow key will be + * delivered to the text control. If the same key is pressed in a radio + * button, the doit field will be <code>true</code>, indicating that + * traversal is to proceed to the next tab item, possibly another radio + * button in the group and that the arrow key is not to be delivered + * to the radio button. + * </p><p> + * How can the traversal event be used to implement traversal? + * When a tab key is pressed in a canvas, the detail field will be + * <code>TRAVERSE_TAB_NEXT</code> and the doit field will be + * <code>false</code>. The default behavior of the system is to + * provide no traversal for canvas controls. This means that by + * default in a canvas, a key listener will see every key that the + * user types, including traversal keys. To understand why this + * is so, it is important to understand that only the widget implementor + * can decide which traversal is appropriate for the widget. Returning + * to the <code>TRAVERSE_TAB_NEXT</code> example, a text widget implemented + * by a canvas would typically want to use the tab key to insert a + * tab character into the widget. A list widget implementation, on the + * other hand, would like the system default traversal behavior. Using + * only the doit flag, both implementations are possible. The text widget + * implementor sets doit to <code>false</code>, ensuring that the system + * will not traverse and that the tab key will be delivered to key listeners. + * The list widget implementor sets doit to <code>true</code>, indicating + * that the system should perform tab traversal and that the key should not + * be delivered to the list widget. + * </p><p> + * How can the traversal event be used to override system traversal? + * When the return key is pressed in a single line text control, the + * detail field is <code>TRAVERSE_RETURN</code> and the doit field + * is <code>true</code>. This means that the return key will be processed + * by the default button, not the text widget. If the text widget has + * a default selection listener, it will not run because the return key + * will be processed by the default button. Imagine that the text control + * is being used as an in-place editor and return is used to dispose the + * widget. Setting doit to <code>false</code> will stop the system from + * activating the default button but the key will be delivered to the text + * control, running the key and selection listeners for the text. How + * can <code>TRAVERSE_RETURN</code> be implemented so that the default button + * will not be activated and the text widget will not see the return key? + * This is achieved by setting doit to <code>true</code>, and the detail + * to <code>TRAVERSE_NONE</code>. + * </p><p> + * Note: A widget implementor will typically implement traversal using + * only the doit flag to either enable or disable system traversal. + * </p> + * + * @see TraverseListener + * @see <a href="http://www.eclipse.org/swt/">Sample code and further information</a> + */ + +public final class TraverseEvent extends KeyEvent { + + /** + * The traversal type. + * <p><ul> + * <li>{@link org.eclipse.swt.SWT#TRAVERSE_NONE}</li> + * <li>{@link org.eclipse.swt.SWT#TRAVERSE_ESCAPE}</li> + * <li>{@link org.eclipse.swt.SWT#TRAVERSE_RETURN}</li> + * <li>{@link org.eclipse.swt.SWT#TRAVERSE_TAB_NEXT}</li> + * <li>{@link org.eclipse.swt.SWT#TRAVERSE_TAB_PREVIOUS}</li> + * <li>{@link org.eclipse.swt.SWT#TRAVERSE_ARROW_NEXT}</li> + * <li>{@link org.eclipse.swt.SWT#TRAVERSE_ARROW_PREVIOUS}</li> + * <li>{@link org.eclipse.swt.SWT#TRAVERSE_MNEMONIC}</li> + * <li>{@link org.eclipse.swt.SWT#TRAVERSE_PAGE_NEXT}</li> + * <li>{@link org.eclipse.swt.SWT#TRAVERSE_PAGE_PREVIOUS}</li> + * </ul></p> + * + * Setting this field will change the type of traversal. + * For example, setting the detail to <code>TRAVERSE_NONE</code> + * causes no traversal action to be taken. + * + * When used in conjunction with the <code>doit</code> field, the + * traversal detail field can be useful when overriding the default + * traversal mechanism for a control. For example, setting the doit + * field to <code>false</code> will cancel the operation and allow + * the traversal key stroke to be delivered to the control. Setting + * the doit field to <code>true</code> indicates that the traversal + * described by the detail field is to be performed. + */ + public int detail; + + static final long serialVersionUID = 3257565105301239349L; + +/** + * Constructs a new instance of this class based on the + * information in the given untyped event. + * + * @param e the untyped event containing the information + */ +public TraverseEvent(Event e) { + super(e); + this.detail = e.detail; +} + +/** + * Returns a string containing a concise, human-readable + * description of the receiver. + * + * @return a string representation of the event + */ +public String toString() { + String string = super.toString (); + return string.substring (0, string.length() - 1) // remove trailing '}' + + " detail=" + detail + + "}"; +} +} |