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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,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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*/
package javax.imageio;
/**
* An interface to be implemented by objects that can determine the
* settings of an <code>IIOParam</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>IIOParam</code> object's
* <code>get</code> methods, modifies values by whatever means, then
* invokes the <code>IIOParam</code> object's <code>set</code> methods
* to modify the appropriate settings. Normally, these
* <code>set</code> methods will be invoked all at once at a final
* commit in order that a cancel operation not disturb existing
* values. In general, applications may expect that when the
* <code>activate</code> method returns <code>true</code>, the
* <code>IIOParam</code> object is ready for use in a read or write
* operation.
*
* <p> Vendors may choose to provide GUIs for the
* <code>IIOParam</code> subclasses they define for a particular
* plug-in. These can be set up as default controllers in the
* corresponding <code>IIOParam</code> subclasses.
*
* <p> Applications may override any default GUIs and provide their
* own controllers embedded in their own framework. All that is
* required is that the<code>activate</code> method behave modally
* (not returning until either cancelled or committed), though it need
* not put up an explicitly modal dialog. Such a non-modal GUI
* component would be coded roughly as follows:
*
* <br>
* <pre>
* class MyGUI extends SomeComponent implements IIOParamController {
*
* public MyGUI() {
* // ...
* setEnabled(false);
* }
*
* public boolean activate(IIOParam param) {
* // disable other components if desired
* setEnabled(true);
* // go to sleep until either cancelled or committed
* boolean ret = false;
* if (!cancelled) {
* // set values on param
* ret = true;
* }
* setEnabled(false);
* // enable any components disabled above
* return ret;
* }
* </pre>
*
* <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 the <code>IIOParam.setXXX</code>
* methods, and return <code>true</code>.
*
* @see IIOParam#setController
* @see IIOParam#getController
* @see IIOParam#getDefaultController
* @see IIOParam#hasController
* @see IIOParam#activateController
*
*/
public interface IIOParamController {
/**
* Activates the controller. If <code>true</code> is returned,
* all settings in the <code>IIOParam</code> object should be
* ready for use in a read or write operation. If
* <code>false</code> is returned, no settings in the
* <code>IIOParam</code> object will be disturbed (<i>i.e.</i>,
* the user canceled the operation).
*
* @param param the <code>IIOParam</code> object to be modified.
*
* @return <code>true</code> if the <code>IIOParam</code> has been
* modified, <code>false</code> otherwise.
*
* @exception IllegalArgumentException if <code>param</code> is
* <code>null</code> or is not an instance of the correct class.
*/
boolean activate(IIOParam param);
}