Toolbox.java

/*
 * Copyright 2008 Eckhart Arnold (eckhart_arnold@hotmail.com).
 * 
 * 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 de.eckhartarnold.client;

// import com.google.gwt.core.client.GWT;
import com.google.gwt.dom.client.Document;
import com.google.gwt.user.client.Window;
import com.google.gwt.user.client.ui.UIObject;

/**
 * Some tool box functions used at several places in the code. Usually, these
 * provide workarounds for known issues and browsers incompatibilities.
 *
 */
public final class Toolbox {
  /** Constants user device classes */
  public final static int PC = 1, PAD = 2, PHONE = 3;
  
  /** true, if the user device reacts to tough events */
  private static boolean hasTouchScreen;
  /** stores the device type */
  private static int   userDeviceType;
  /** stores the pixel density (dots per inch) of the user's screen */
  private static int   userDPI;
  /** stores the user's screen size in inches */
  private static float userScreenSize;
  
  /** substrings of navigator.userAgent that indicate a handheld device. */
  private static final String[] handheld_markers = 
  {
    "iPhone","Android", "Opera Mobi", "Opera Mini", "BlackBerry", "IEMobile",
    "MSIEMobile", "Windows Phone", "Symbian", "Maemo", "Midori", "Windows CE",
    "WindowsCE", "Smartphone","240x320", "320x320", "160x160", "webOS"
  };  
  
  static {
    /* determine the device type. As of now tablet computers are always 
     * classified as smartphones. */
    String userAgent = Window.Navigator.getUserAgent().toLowerCase();
    userDeviceType = PC;
    hasTouchScreen = false;
    for (String marker: handheld_markers){
      if (userAgent.contains(marker.toLowerCase())) {
        userDeviceType = PHONE;
        hasTouchScreen = true;
        break;
      }
    }
    if (Document.get().getDocumentElement().getAttribute("ontouchstart").length() > 0) {
      hasTouchScreen = true;
    }    
    
    if (userDeviceType == PC) {
      userScreenSize = 22.0f;
      userDPI = 100;
    } else if (userDeviceType == PHONE) {
      userScreenSize = 4.0f;
      userDPI = 200;
    } else {
      userScreenSize = 10.0f;
      userDPI = 150;
    }  
  }
  
  
  /**
   * Returns the offset height of an UI object. For some reason, this is often
   * zero in non-quirks mode. In this case the offset height will be guessed
   * with a very crude algorithm based on the client window's size.
   * @param uiobject the UIObject, the height of which shall be determined
   * @return the (assumed) offset height of an UI object.
   */
  public static int getOffsetHeight(UIObject uiobject) {
    int height = uiobject.getOffsetHeight();
    if (height == 0) {
      int clientW = Window.getClientWidth();
      int clientH = Window.getClientHeight();
      int width = uiobject.getOffsetWidth();
      height = clientH * width / clientW;
    }
    return height;
  }
  
  /**
   * Returns the offset width of an UI object. Usually, the same as
   * <code>uiobject.getOffsetWidth()</code>
   * @param uiobject the UIObject for which the width shall be determined
   * @return the offset width of uiobject.
   */
  public static int getOffsetWidth(UIObject uiobject) {
    return uiobject.getOffsetWidth();
  }
  
  /**
   * Determines the kind of device (personal computer, smartphone or
   * touchpad) that the user has.
   * @return  constant describing the device; either PC, PAD, or PHONE.
   */
  public static int getUserDeviceType() {
    return userDeviceType;
  }
  
  /**
   * Returns the pixel density of the user's display in dots per inch.
   * (Warning: As of now, the returned value is not very reliable)
   * @return pixel density in dots per inch
   */
  public static int getUserDPI() {
    return userDPI;
  }
  
  /**
   * Returns the user's device's screen size in inches. (Most of the
   * time this will be just an informed guess.)
   * @return screen size of the user's device in inches.
   */
  public static float getUserScreenSize() {
    return userScreenSize;
  }

}