/*
 * Copyright 2011 Google Inc.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.google.gwt.sample.mobilewebapp.client.ui;

import com.google.gwt.event.logical.shared.HasAttachHandlers;
import com.google.gwt.user.client.Command;
import com.google.web.bindery.event.shared.HandlerRegistration;

/**
 * Accepts {@link Command}s to be run when the browser window or device's
 * orientation changes. Commands operate only while the associated widget is
 * attached.
 */
public interface OrientationHelper {
  /**
   * Gives efficient on demand access to the orientation of the window or
   * device.
   * 
   * @return true for portrait, false for landscape
   */
  boolean isPortrait();

  /**
   * Set commands to run on orientation change, one for portrait and one for
   * landscape. The appropriate command is fired immediately if this method is
   * called while the widget is attached.
   * <p>
   * Commands are also fired each time the widget is attached. If that is not
   * desired a widget should call {@link HandlerRegistration#removeHandler()} on
   * the returned object when it detaches.
   * 
   * @param widget the widget to help
   * @param forPortrait command to run when on shift to portrait
   * @param forLandscape command to run when on shift to landscape
   * @return registration object to be used to stop and dereference the commands
   */
  HandlerRegistration setCommands(HasAttachHandlers widget, Command forPortrait,
      Command forLandscape);
}