IActionFilter


1   /*******************************************************************************
2    * Copyright (c) 2000, 2006 IBM Corporation and others.
3    * All rights reserved. This program and the accompanying materials
4    * are made available under the terms of the Eclipse Public License v1.0
5    * which accompanies this distribution, and is available at
6    * http://www.eclipse.org/legal/epl-v10.html
7    *
8    * Contributors:
9    *     IBM Corporation - initial API and implementation
10   *******************************************************************************/
11  package org.eclipse.ui;
12  
13  /**
14   * An adapter which performs action filtering.
15   * <p>
16   * Within the workbench a plugin may extend the actions which appear in the
17   * context menu for any object.  The visibility of each action extension is controlled
18   * by action filtering.  By default, the workbench will filter each action extension using 
19   * the <code>objectClass</code> and optional <code>nameFilter</code> attributes defined
20   * in xml.  If the action extension passes this test the action will be added to the 
21   * context menu for the object. 
22   * </p>
23   * <p>
24   * In some situations the object class and name are not enough to describe the intended
25   * target action.  In those situations an action extension may define one or more 
26   * <code>filter</code> sub-elements.  Each one of these elements describes one attribute of 
27   * the action target using a <code>name value</code> pair.  The attributes for an object 
28   * are type specific and beyond the domain of the workbench itself, so the workbench 
29   * will delegate filtering at this level to an <code>IActionFilter</code>.  This is a 
30   * filtering strategy which is provided by the selection itself and may perform type 
31   * specific filtering.
32   * </p>
33   * <p>
34   * The workbench will retrieve the filter from the selected object by testing to see
35   * if it implements <code>IActionFilter</code>.  If that fails, the workbench will ask for
36   * a filter through through the <code>IAdaptable</code> mechanism.  If a filter is
37   * found the workbench will pass each name value pair to the filter to determine if it 
38   * matches the state of the selected object.  If so, or there is no filter, the action 
39   * will be added to the context menu for the object. 
40   * </p>
41   * <p>
42   * Clients that implement this filter mechanism are strongly encouraged to extend this
43   * interface to provide a list of attribute names and possible values that are
44   * considered public for other clients to reference.
45   * </p>
46   *
47   * @see org.eclipse.core.runtime.IAdaptable
48   */
49  public interface IActionFilter {
50      /**
51       * Returns whether the specific attribute matches the state of the target
52       * object.
53       *
54       * @param target the target object
55       * @param name the attribute name
56       * @param value the attribute value
57       * @return <code>true</code> if the attribute matches; <code>false</code> otherwise
58       */
59      public boolean testAttribute(Object   target, String   name, String   value);
60  }
61
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