Texas Instruments matrix-gui-2.0 hacking -- menubar.php

<?php
/*
 * Copyright (C) 2011 Texas Instruments Incorporated - http://www.ti.com/ 
 * 
 * 
 *  Redistribution and use in source and binary forms, with or without 
 *  modification, are permitted provided that the following conditions 
 *  are met:
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 *    Redistributions of source code must retain the above copyright 
 *    notice, this list of conditions and the following disclaimer.
 *
 *    Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the 
 *    documentation and/or other materials provided with the   
 *    distribution.
 *
 *    Neither the name of Texas Instruments Incorporated nor the names of
 *    its contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 
 *  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 
 *  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 *  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 
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*/
?>
<?php
/*
----Note----
This file is meant to be included in the php file of another page. Therefore, some variables used in this file is assumed to be set within the page that includes this file.
You will notice that these variables are always checked to make sure they are set (set from the other page). If the variable isn't set then the variable is given a default value
which usually is meant to deactivate something. This is done to allow pages that are including this file to only set the variables they care about
*/

//Some parts of the code doesn't set the submenu variable when the user is at the Main Menu which is relected in the "top" variable
# 查看子菜单是否设置,并作相应的赋值
$submenu = isset($_GET["submenu"]) == true ? $_GET["submenu"] : "main_menu" ;

# 查看前面一页是否设置
$previous_page = isset($previous_page) == true ? $previous_page : -1;
# 是否打开了前面一页的链接,如果previous_page是-1，表示不能再往前了
$enable_previous_link = $previous_page >= 0;

# 查看往后一页是否设置
$next_page = isset($next_page) == true ? $next_page : -1;
# 是否打开了往后往后一页的链接
$enable_next_link = $next_page > 0;

# 查看是否打开主页链接使能
$enable_main_menu_link = isset($enable_main_menu_link) == true ? $enable_main_menu_link : false;
?>

<!-- 由id ＝ "menubar" 可知，这是一个菜单栏 -->
<table id = "menubar" width = "100%" style = "margin-bottom:10px;">
    <tr>
        <td  align = "left" >
            <?php 
                # 构建链接地址
                $link = "submenu.php?submenu=".$submenu."&page=".$previous_page;
                # 构建css字符串,hide_link的意思是隐藏链接的意思
                $css_string = ($enable_previous_link == false) ? "hide_link" : "";

                # 生成超级链接，并根据css_string决定是否显示
                echo "<a href = '$link' class = 'previous_arrow $css_string' ><img id = 'previous_arrow_img' src= 'images/left-arrow-icon.png'></a>";

                //Added these two html elements so that each side will be even
                # 这两个图标没有超级链接的用途，当然也就被隐藏(hide_link)了
                echo "<a href = '#'  class = 'hide_link'><img id = 'exit_button_img' src= 'images/multi-icon.png'></a>";
                echo "<a href = '#'  class = 'hide_link'><img id = 'next_arrow_img' src= 'images/right-arrow-icon.png'></a>";
            ?>

        </td>
        <!-- banner: 旗帜, 貌似是说logo的意思 -->
        <td  align = "center" id = "banner" >
            <?php  
                echo "<img id = 'logo_img' src= 'images/tex.png'>";
                echo $menu_title;
            ?>
        </td>
        <td  align = "right" >
            <?php
                # 看是否有链接到主页的功能
                $css_string = ($enable_main_menu_link == false) ? "hide_link" : "";

                # 无效链接
                echo "<a  id = 'back_link' class = '$css_string' href = '#'><img id = 'back_button_img' src= 'images/back-arrow-icon.png'></a>";
                # 链接到主页的超级链接
                echo "<a  id = 'main_menu_link' class = '$css_string' href = 'submenu.php?submenu=main_menu&page=0'  ><img id = 'exit_button_img' src= 'images/multi-icon.png'></a>";

                $css_string = ($enable_next_link == true) ? "" : "hide_link";

                # 是否显示下一页的链接
                $link = "submenu.php?submenu=".$submenu."&page=".$next_page;
                echo "<a href = '$link' class = '$css_string' ><img id = 'next_arrow_img' src= 'images/right-arrow-icon.png'></a>";

            ?>
        </td>
    </tr>
</table>