/*******************************************************************************
 * Copyright (c) 2004, 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.themes;

import org.eclipse.jface.util.IPropertyChangeListener;

/**
 * A theme manager is an object that contains references to usable
 * <code>ITheme</code> objects and maintains a reference to the currently active
 * theme. This theme will be used by the workbench to decorate tab folders and
 * other controls where possible. The workbench implementation of this interface
 * will push the values of the current theme into the underlying jface
 * registries ({@link org.eclipse.jface.resource.ColorRegistry} and
 * {@link org.eclipse.jface.resource.FontRegistry} whenever the current theme
 * changes. Clients who do not need access to specific themes may instead attach
 * listeners to these registries directly.
 *
 * <p>
 * This interface is not intended to be implemented or extended by clients.
 * </p>
 *
 * @see org.eclipse.ui.IWorkbench#getThemeManager()
 * @since 3.0
 * @noimplement This interface is not intended to be implemented by clients.
 */
public interface IThemeManager {

	/**
	 * Indicates that the current theme has changed to a new theme.
	 */
	String CHANGE_CURRENT_THEME = "CHANGE_CURRENT_THEME"; //$NON-NLS-1$

	/**
	 * The default theme id.
	 */
	String DEFAULT_THEME = "org.eclipse.ui.defaultTheme"; //$NON-NLS-1$

	/**
	 * Adds a property listener to the manager. Any events fired by the underlying
	 * registries of the current theme will cause an event to be fired. This event
	 * is the same event that was fired by the registry. As such, the "source"
	 * attribute of the event will not be this manager, but rather the color or font
	 * registry. Additionally, an event is fired when the current theme changes to a
	 * new theme. The "property" attribute of such an event will have the value
	 * {@link IThemeManager#CHANGE_CURRENT_THEME}.
	 *
	 * @param listener the listener to add
	 */
	void addPropertyChangeListener(IPropertyChangeListener listener);

	/**
	 * Get the currently active theme.
	 *
	 * @return the current theme. This will never be <code>null</code>.
	 */
	ITheme getCurrentTheme();

	/**
	 * Get a theme.
	 *
	 * @param id the theme to find.
	 * @return the <code>ITheme</code> or <code>null</code> if it cannot be found.
	 */
	ITheme getTheme(String id);

	/**
	 * Removes a property listener from the workbench.
	 *
	 * @param listener the listener to remove
	 */
	void removePropertyChangeListener(IPropertyChangeListener listener);

	/**
	 * Set the currently active theme.
	 *
	 * @param id the id of the new active theme
	 */
	void setCurrentTheme(String id);
}
