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1   /*
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3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5    * This code is free software; you can redistribute it and/or modify it
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8    * particular file as subject to the "Classpath" exception as provided
9    * by Oracle in the LICENSE file that accompanied this code.
10   *
11   * This code is distributed in the hope that it will be useful, but WITHOUT
12   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14   * version 2 for more details (a copy is included in the LICENSE file that
15   * accompanied this code).
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17   * You should have received a copy of the GNU General Public License version
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19   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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25  
26  package javax.imageio.metadata;
27  
28  /**
29   * An interface to be implemented by objects that can determine the
30   * settings of an <code>IIOMetadata</code> object, either by putting
31   * up a GUI to obtain values from a user, or by other means.  This
32   * interface merely specifies a generic <code>activate</code> method
33   * that invokes the controller, without regard for how the controller
34   * obtains values (<i>i.e.</i>, whether the controller puts up a GUI
35   * or merely computes a set of values is irrelevant to this
36   * interface).
37   *
38   * <p> Within the <code>activate</code> method, a controller obtains
39   * initial values by querying the <code>IIOMetadata</code> object's
40   * settings, either using the XML DOM tree or a plug-in specific
41   * interface, modifies values by whatever means, then modifies the
42   * <code>IIOMetadata</code> object's settings, using either the
43   * <code>setFromTree</code> or <code>mergeTree</code> methods, or a
44   * plug-in specific interface.  In general, applications may expect
45   * that when the <code>activate</code> method returns
46   * <code>true</code>, the <code>IIOMetadata</code> object is ready for
47   * use in a write operation.
48   *
49   * <p> Vendors may choose to provide GUIs for the
50   * <code>IIOMetadata</code> subclasses they define for a particular
51   * plug-in.  These can be set up as default controllers in the
52   * corresponding <code>IIOMetadata</code> subclasses.
53   *
54   * <p> Alternatively, an algorithmic process such as a database lookup
55   * or the parsing of a command line could be used as a controller, in
56   * which case the <code>activate</code> method would simply look up or
57   * compute the settings, call methods on <code>IIOMetadata</code> to
58   * set its state, and return <code>true</code>.
59   *
60   * @see IIOMetadata#setController
61   * @see IIOMetadata#getController
62   * @see IIOMetadata#getDefaultController
63   * @see IIOMetadata#hasController
64   * @see IIOMetadata#activateController
65   *
66   */
67  public interface IIOMetadataController {
68  
69      /**
70       * Activates the controller.  If <code>true</code> is returned,
71       * all settings in the <code>IIOMetadata</code> object should be
72       * ready for use in a write operation.  If <code>false</code> is
73       * returned, no settings in the <code>IIOMetadata</code> object
74       * will be disturbed (<i>i.e.</i>, the user canceled the
75       * operation).
76       *
77       * @param metadata the <code>IIOMetadata</code> object to be modified.
78       *
79       * @return <code>true</code> if the <code>IIOMetadata</code> has been
80       * modified, <code>false</code> otherwise.
81       *
82       * @exception IllegalArgumentException if <code>metadata</code> is
83       * <code>null</code> or is not an instance of the correct class.
84       */
85      boolean activate(IIOMetadata metadata);
86  }