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/*******************************************************************************
* Copyright (c) 2000, 2015 IBM Corporation and others.
*
* This program and the accompanying materials
* are made available under the terms of the Eclipse Public License 2.0
* which accompanies this distribution, and is available at
* https://www.eclipse.org/legal/epl-2.0/
*
* SPDX-License-Identifier: EPL-2.0
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.ui;
import org.eclipse.jface.action.IAction;
import org.eclipse.jface.viewers.ISelection;
/**
* Interface for actions contributed via an extension point.
* <p>
* This interface should be implemented by clients who need to contribute actions
* via an extension point. The workbench will generate a <b>proxy action</b>
* object on behalf of the plug-in to avoid having to activate the plug-in until
* the user needs it. If the action is performed the workbench will load the class
* that implements this interface and create what is called an <b>action
* delegate</b> object. Then the request, and all subsequent ones, are
* forwarded through the proxy action to the action delegate, which does the
* real work.
* </p><p>
* The proxy action is the one that appears in the UI, so the action delegate
* will need to talk to the proxy action in order to keep up an appropriate
* appearance. Once the action delegate has been created, it will be
* notified of all selection changes, allowing it to enable or disable the
* proxy action appropriately.
* </p><p>
* An action delegate cannot be consulted about selection changes before the
* action is performed because it does not exist. For this reason, control of
* the action's enable state should also be exercised through simple XML rules
* contained in the extension. These rules allow enable state control before
* the action delegate's plug-in is loaded.
* </p><p>
* Clients can choose to subclass the provided abstract implementation
* <code>org.eclipse.ui.actions.ActionDelegate</code> or implement the
* interface directly.
* </p>
*
* @see org.eclipse.ui.actions.ActionDelegate
* @see org.eclipse.ui.IActionDelegate2
*/
public interface IActionDelegate {
/**
* Performs this action.
* <p>
* This method is called by the proxy action when the action has been
* triggered. Implement this method to do the actual work.
* </p><p>
* <b>Note:</b> If the action delegate also implements
* <code>IActionDelegate2</code>, then this method is not invoked but
* instead the <code>runWithEvent(IAction, Event)</code> method is called.
* </p>
*
* @param action the action proxy that handles the presentation portion of the
* action
*/
void run(IAction action);
/**
* Notifies this action delegate that the selection in the workbench has changed.
* <p>
* Implementers can use this opportunity to change the availability of the
* action or to modify other presentation properties.
* </p><p>
* When the selection changes, the action enablement state is updated based on
* the criteria specified in the plugin.xml file. Then the delegate is notified
* of the selection change regardless of whether the enablement criteria in the
* plugin.xml file is met.
* </p>
*
* @param action the action proxy that handles presentation portion of
* the action
* @param selection the current selection, or <code>null</code> if there
* is no selection.
*/
void selectionChanged(IAction action, ISelection selection);
}
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