package org.eclipse.ui.internal;

/*
 * (c) Copyright IBM Corp. 2000, 2001.
 * All Rights Reserved.
 */
import org.eclipse.ui.*;

/**
 * The abstract superclass for actions that depend on the active editor.
 * This implementation tracks the active editor (see <code>getActiveEditor</code>)
 * and updates the availability of the action when an editor becomes
 * active.
 * <p>
 * Subclasses must implement the following <code>IAction</code> method:
 * <ul>
 *   <li><code>run</code> - to do the action's work</li>
 * </ul>
 * </p>
 * <p>
 * Subclasses may extend any of the <code>IPartListener</code> methods if the
 * action availablity needs to be recalculated:
 * <ul>
 *   <li><code>partActivated</code></li> 
 *   <li><code>partDeactivated</code></li>
 *   <li><code>partOpened</code></li>
 *   <li><code>partClosed</code></li>
 *   <li><code>partBroughtToTop</code></li>
 * </ul>
 * </p>
 * <p>
 * Subclasses may extend any of the <code>IPageListener</code> methods if the
 * action availablity needs to be recalculated:
 * <ul>
 *   <li><code>pageActivated</code></li> 
 *   <li><code>pageClosed</code></li>
 *   <li><code>pageOpened</code></li>
 * </ul>
 * </p>
 */
public abstract class ActiveEditorAction extends PageEventAction {
	private IEditorPart activeEditor;
/**
 * Creates a new action with the given text.
 *
 * @param text the string used as the text for the action, 
 *   or <code>null</code> if these is no text
 * @param window the workbench window this action is
 *   registered with.
 */
protected ActiveEditorAction(String text, IWorkbenchWindow window) {
	super(text, window);
	updateState();
}
/**
 * Notification that the active editor tracked
 * by the action is being activated.
 *
 * Subclasses can overwrite.
 */
protected void editorActivated(IEditorPart part) {
}
/**
 * Notification that the active editor tracked
 * by the action is being deactivated.
 *
 * Subclasses can overwrite.
 */
protected void editorDeactivated(IEditorPart part) {
}
/**
 * Return the active editor
 *
 * @return the page's active editor, and <code>null</code>
 *		if no active editor or no active page.
 */
public IEditorPart getActiveEditor() {
	return activeEditor;
}
/* (non-Javadoc)
 * Method declared on PageEventAction.
 */
public void pageActivated(IWorkbenchPage page) {
	super.pageActivated(page);
	updateActiveEditor();
	updateState();
}
/* (non-Javadoc)
 * Method declared on PageEventAction.
 */
public void pageClosed(IWorkbenchPage page) {
	super.pageClosed(page);
	updateActiveEditor();
	updateState();
}
/* (non-Javadoc)
 * Method declared on PartEventAction.
 */
public void partActivated(IWorkbenchPart part) {
	super.partActivated(part);
	if (part instanceof IEditorPart) {
		updateActiveEditor();
		updateState();
	}
}
/* (non-Javadoc)
 * Method declared on PartEventAction.
 */
public void partBroughtToTop(IWorkbenchPart part) {
	super.partBroughtToTop(part);
	if (part instanceof IEditorPart) {
		updateActiveEditor();
		updateState();
	}
}
/* (non-Javadoc)
 * Method declared on PartEventAction.
 */
public void partClosed(IWorkbenchPart part) {
	super.partClosed(part);
	if (part instanceof IEditorPart) {
		updateActiveEditor();
		updateState();
	}
}
/* (non-Javadoc)
 * Method declared on PartEventAction.
 */
public void partDeactivated(IWorkbenchPart part) {
	super.partDeactivated(part);
	if (part instanceof IEditorPart) {
		updateActiveEditor();
		updateState();
	}
}
/**
 * Set the active editor
 */
private void setActiveEditor(IEditorPart part) {
	if (activeEditor == part)
		return;
	if (activeEditor != null)
		editorDeactivated(activeEditor);
	activeEditor = part;
	if (activeEditor != null)
		editorActivated(activeEditor);
}
/**
 * Update the active editor based on the current
 * active page.
 */
private void updateActiveEditor() {
	if (getActivePage() == null)
		setActiveEditor(null);
	else
		setActiveEditor(getActivePage().getActiveEditor());
}
/**
 * Update the state of the action. By default, the action
 * is enabled if there is an active editor.
 *
 * Subclasses may overwrite this method.
 */
protected void updateState() {
	setEnabled(getActiveEditor() != null);
}
}