de.eckhartarnold.client.Toolbox.java Source code

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Here is the source code for de.eckhartarnold.client.Toolbox.java

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/*
 * 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;
    }

}