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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

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 *

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package javax.imageio.metadata;

/**

 * An interface to be implemented by objects that can determine the

 * settings of an <code>IIOMetadata</code> object, either by putting

 * up a GUI to obtain values from a user, or by other means.  This

 * interface merely specifies a generic <code>activate</code> method

 * that invokes the controller, without regard for how the controller

 * obtains values (<i>i.e.</i>, whether the controller puts up a GUI

 * or merely computes a set of values is irrelevant to this

 * interface).

 *

 * <p> Within the <code>activate</code> method, a controller obtains

 * initial values by querying the <code>IIOMetadata</code> object's

 * settings, either using the XML DOM tree or a plug-in specific

 * interface, modifies values by whatever means, then modifies the

 * <code>IIOMetadata</code> object's settings, using either the

 * <code>setFromTree</code> or <code>mergeTree</code> methods, or a

 * plug-in specific interface.  In general, applications may expect

 * that when the <code>activate</code> method returns

 * <code>true</code>, the <code>IIOMetadata</code> object is ready for

 * use in a write operation.

 *

 * <p> Vendors may choose to provide GUIs for the

 * <code>IIOMetadata</code> subclasses they define for a particular

 * plug-in.  These can be set up as default controllers in the

 * corresponding <code>IIOMetadata</code> subclasses.

 *

 * <p> Alternatively, an algorithmic process such as a database lookup

 * or the parsing of a command line could be used as a controller, in

 * which case the <code>activate</code> method would simply look up or

 * compute the settings, call methods on <code>IIOMetadata</code> to

 * set its state, and return <code>true</code>.

 *

 * @see IIOMetadata#setController

 * @see IIOMetadata#getController

 * @see IIOMetadata#getDefaultController

 * @see IIOMetadata#hasController

 * @see IIOMetadata#activateController

 *

 */

public interface IIOMetadataController {

    /**

     * Activates the controller.  If <code>true</code> is returned,

     * all settings in the <code>IIOMetadata</code> object should be

     * ready for use in a write operation.  If <code>false</code> is

     * returned, no settings in the <code>IIOMetadata</code> object

     * will be disturbed (<i>i.e.</i>, the user canceled the

     * operation).

     *

     * @param metadata the <code>IIOMetadata</code> object to be modified.

     *

     * @return <code>true</code> if the <code>IIOMetadata</code> has been

     * modified, <code>false</code> otherwise.

     *

     * @exception IllegalArgumentException if <code>metadata</code> is

     * <code>null</code> or is not an instance of the correct class.

     */

    boolean activate(IIOMetadata metadata);

}