001 /*
002 * Copyright 2000 Sun Microsystems, Inc. All Rights Reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation. Sun designates this
008 * particular file as subject to the "Classpath" exception as provided
009 * by Sun in the LICENSE file that accompanied this code.
010 *
011 * This code is distributed in the hope that it will be useful, but WITHOUT
012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014 * version 2 for more details (a copy is included in the LICENSE file that
015 * accompanied this code).
016 *
017 * You should have received a copy of the GNU General Public License version
018 * 2 along with this work; if not, write to the Free Software Foundation,
019 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020 *
021 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022 * CA 95054 USA or visit www.sun.com if you need additional information or
023 * have any questions.
024 */
025
026 package javax.imageio;
027
028 /**
029 * An interface to be implemented by objects that can determine the
030 * settings of an <code>IIOParam</code> object, either by putting up a
031 * GUI to obtain values from a user, or by other means. This
032 * interface merely specifies a generic <code>activate</code> method
033 * that invokes the controller, without regard for how the controller
034 * obtains values (<i>i.e.</i>, whether the controller puts up a GUI
035 * or merely computes a set of values is irrelevant to this
036 * interface).
037 *
038 * <p> Within the <code>activate</code> method, a controller obtains
039 * initial values by querying the <code>IIOParam</code> object's
040 * <code>get</code> methods, modifies values by whatever means, then
041 * invokes the <code>IIOParam</code> object's <code>set</code> methods
042 * to modify the appropriate settings. Normally, these
043 * <code>set</code> methods will be invoked all at once at a final
044 * commit in order that a cancel operation not disturb existing
045 * values. In general, applications may expect that when the
046 * <code>activate</code> method returns <code>true</code>, the
047 * <code>IIOParam</code> object is ready for use in a read or write
048 * operation.
049 *
050 * <p> Vendors may choose to provide GUIs for the
051 * <code>IIOParam</code> subclasses they define for a particular
052 * plug-in. These can be set up as default controllers in the
053 * corresponding <code>IIOParam</code> subclasses.
054 *
055 * <p> Applications may override any default GUIs and provide their
056 * own controllers embedded in their own framework. All that is
057 * required is that the<code>activate</code> method behave modally
058 * (not returning until either cancelled or committed), though it need
059 * not put up an explicitly modal dialog. Such a non-modal GUI
060 * component would be coded roughly as follows:
061 *
062 * <br>
063 * <pre>
064 * class MyGUI extends SomeComponent implements IIOParamController {
065 *
066 * public MyGUI() {
067 * // ...
068 * setEnabled(false);
069 * }
070 *
071 * public boolean activate(IIOParam param) {
072 * // disable other components if desired
073 * setEnabled(true);
074 * // go to sleep until either cancelled or committed
075 * boolean ret = false;
076 * if (!cancelled) {
077 * // set values on param
078 * ret = true;
079 * }
080 * setEnabled(false);
081 * // enable any components disabled above
082 * return ret;
083 * }
084 * </pre>
085 *
086 * <p> Alternatively, an algorithmic process such as a database lookup
087 * or the parsing of a command line could be used as a controller, in
088 * which case the <code>activate</code> method would simply look up or
089 * compute the settings, call the <code>IIOParam.setXXX</code>
090 * methods, and return <code>true</code>.
091 *
092 * @see IIOParam#setController
093 * @see IIOParam#getController
094 * @see IIOParam#getDefaultController
095 * @see IIOParam#hasController
096 * @see IIOParam#activateController
097 *
098 * @version 0.5
099 */
100 public interface IIOParamController {
101
102 /**
103 * Activates the controller. If <code>true</code> is returned,
104 * all settings in the <code>IIOParam</code> object should be
105 * ready for use in a read or write operation. If
106 * <code>false</code> is returned, no settings in the
107 * <code>IIOParam</code> object will be disturbed (<i>i.e.</i>,
108 * the user canceled the operation).
109 *
110 * @param param the <code>IIOParam</code> object to be modified.
111 *
112 * @return <code>true</code> if the <code>IIOParam</code> has been
113 * modified, <code>false</code> otherwise.
114 *
115 * @exception IllegalArgumentException if <code>param</code> is
116 * <code>null</code> or is not an instance of the correct class.
117 */
118 boolean activate(IIOParam param);
119 }
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