1 /*
   2  * Copyright (c) 2000, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   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).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  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 }