iaction.java

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/*******************************************************************************
 * Copyright (c) 2000, 2005 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jface.action;

import org.eclipse.core.commands.IHandlerAttributes;
import org.eclipse.jface.resource.ImageDescriptor;
import org.eclipse.jface.util.IPropertyChangeListener;
import org.eclipse.swt.events.HelpListener;
import org.eclipse.swt.widgets.Event;

/**
 * An action represents the non-UI side of a command which can be triggered
 * by the end user. Actions are typically associated with buttons, menu items,
 * and items in tool bars. The controls for a command are built by some container,
 * which furnished the context where these controls appear and configures 
 * them with data from properties declared by the action. When the end user
 * triggers the command via its control, the action's <code>run</code>
 * method is invoked to do the real work.
 * <p>
 * Actions support a predefined set of properties (and possibly others as well).
 * Clients of an action may register property change listeners so that they get 
 * notified whenever the value of a property changes.
 * </p>
 * <p>
 * Clients should subclass the abstract base class <code>Action</code> to define 
 * concrete actions rather than implementing <code>IAction</code> from scratch.
 * </p>
 * <p>
 * This interface exists only to define the API for actions.
 * It is not intended to be implemented by clients.
 * </p>
 * 
 * @see Action
 */
public interface IAction {

    /**
     * Action style constant (value <code>0</code>) indicating action style 
     * is not specified yet. By default, the action will assume a push button
     * style. If <code>setChecked</code> is called, then the style will change
     * to a check box, or if <code>setMenuCreator</code> is called, then the
     * style will change to a drop down menu.
     * 
     * @since 2.1
     */
    public static int AS_UNSPECIFIED = 0x00;

    /**
     * Action style constant (value <code>1</code>) indicating action is 
     * a simple push button.
     */
    public static int AS_PUSH_BUTTON = 0x01;

    /**
     * Action style constant (value <code>2</code>) indicating action is 
     * a check box (or a toggle button).
     */
    public static int AS_CHECK_BOX = 0x02;

    /**
     * Action style constant (value <code>4</code>) indicating action is 
     * a drop down menu.
     */
    public static int AS_DROP_DOWN_MENU = 0x04;

    /**
     * Action style constant (value <code>8</code>) indicating action is 
     * a radio button.
     * 
     * @since 2.1
     */
    public static int AS_RADIO_BUTTON = 0x08;

    /**
     * Property name of an action's text (value <code>"text"</code>).
     */
    public static final String TEXT = "text"; //$NON-NLS-1$

    /**
     * Property name of an action's enabled state
     * (value <code>"enabled"</code>).
     */
    public static final String ENABLED = "enabled"; //$NON-NLS-1$

    /**
     * Property name of an action's image (value <code>"image"</code>).
     */
    public static final String IMAGE = "image"; //$NON-NLS-1$

    /**
     * Property name of an action's tooltip text (value <code>"toolTipText"</code>).
     */
    public static final String TOOL_TIP_TEXT = "toolTipText"; //$NON-NLS-1$

    /**
     * Property name of an action's description (value <code>"description"</code>).
     * Typically the description is shown as a (longer) help text in the status line.
     */
    public static final String DESCRIPTION = "description"; //$NON-NLS-1$

    /**
     * Property name of an action's checked status (value
     * <code>"checked"</code>). Applicable when the style is
     * <code>AS_CHECK_BOX</code> or <code>AS_RADIO_BUTTON</code>.
     */
    public static final String CHECKED = "checked"; //$NON-NLS-1$

    /**
     * Property name of an action's success/fail result
     * (value <code>"result"</code>). The values are
     * <code>Boolean.TRUE</code> if running the action succeeded and 
     * <code>Boolean.FALSE</code> if running the action failed or did not
     * complete.
     * <p>
     * Not all actions report whether they succeed or fail. This property
     * is provided for use by actions that may be invoked by clients that can
     * take advantage of this information when present (for example, actions
     * used in cheat sheets). Clients should always assume that running the
     * action succeeded in the absence of notification to the contrary. 
     * </p>
     * 
     * @since 3.0
     */
    public static final String RESULT = "result"; //$NON-NLS-1$
    
    /**
     * Property name of an action's handler. Some actions delegate some or all
     * of their behaviour or state to another object. In this case, if the
     * object to which behaviour has been delegated changes, then a property
     * change event should be sent with this name.
     * 
     * This is used to support backward compatibility of actions within the
     * commands framework.
     * 
     * @since 3.1
     */
	public static final String HANDLED = IHandlerAttributes.ATTRIBUTE_HANDLED;

    /**
     * Adds a property change listener to this action.
     * Has no effect if an identical listener is already registered.
     *
     * @param listener a property change listener
     */
    public void addPropertyChangeListener(IPropertyChangeListener listener);

    /**
     * Returns the accelerator keycode for this action.
     * The result is the bit-wise OR of zero or more modifier masks
     * and a key, as explained in <code>MenuItem.getAccelerator</code>.
     *
     * @return the accelerator keycode
     * @see org.eclipse.swt.widgets.MenuItem#getAccelerator()
     */
    public int getAccelerator();

    /**
     * Returns the action definition id of this action.
     * 
     * @return the action definition id of this action, or
     * <code>null</code> if none
     * @since 2.0
     */
    public String getActionDefinitionId();

    /**
     * Returns the action's description if it has one.
     * Otherwise it returns <code>getToolTipText()</code>.
     * 
     * @return a description for the action; may be <code>null</code> 
     */
    public String getDescription();

    /**
     * Returns the disabled image for this action as an image descriptor.
     * <p>
     * This method is associated with the <code>IMAGE</code> property;
     * property change events are reported when its value changes.
     * </p>
     *
     * @return the image, or <code>null</code> if this action has no image
     * @see #IMAGE
     */
    public ImageDescriptor getDisabledImageDescriptor();

    /**
     * Returns a help listener for this action. 
     *
     * @return a help listener for this action
     */
    public HelpListener getHelpListener();

    /**
     * Returns the hover image for this action as an image descriptor.
     * <p>
     * Hover images will be used on platforms that support changing the image
     * when the user hovers over the item. This method is associated with 
     * the <code>IMAGE</code> property;
     * property change events are reported when its value changes.
     * </p>
     *
     * @return the image, or <code>null</code> if this action has no image
     * @see #IMAGE
     */
    public ImageDescriptor getHoverImageDescriptor();

    /**
     * Returns a unique identifier for this action, or <code>null</code> if it has
     * none.
     *
     * @return the action id, or <code>null</code> if none
     */
    public String getId();

    /**
     * Returns the image for this action as an image descriptor.
     * <p>
     * This method is associated with the <code>IMAGE</code> property;
     * property change events are reported when its value changes.
     * </p>
     *
     * @return the image, or <code>null</code> if this action has no image
     * @see #IMAGE
     */
    public ImageDescriptor getImageDescriptor();

    /**
     * Returns the menu creator for this action.
     *
     * @return the menu creator, or <code>null</code> if none
     */
    public IMenuCreator getMenuCreator();

    /**
     * Return this action's style.
     *
     * @return one of <code>AS_PUSH_BUTTON</code>, <code>AS_CHECK_BOX</code>,
     * <code>AS_RADIO_BUTTON</code> and <code>AS_DROP_DOWN_MENU</code>.
     */
    public int getStyle();

    /**
     * Returns the text for this action.
     * <p>
     * This method is associated with the <code>TEXT</code> property;
     * property change events are reported when its value changes.
     * </p>
     *
     * @return the text, or <code>null</code> if none
     * @see #TEXT
     */