PPAPI插件与浏览器的通信

PPAPI的插件，原本是可以使用JS与浏览器交互的，[https://code.google.com/p/ppapi/wiki/InterfacingWithJavaScript](https://code.google.com/p/ppapi/wiki/InterfacingWithJavaScript)，这里还提供了一个JS与plugin交互的文档，但现在说不支持了，现在应该通过PPB_Messaging接口来完成Plugin和浏览器的交互，具体参考[https://src.chromium.org/viewvc/chrome/trunk/src/ppapi/c/ppb_messaging.h?revision=92312&view=markup](https://src.chromium.org/viewvc/chrome/trunk/src/ppapi/c/ppb_messaging.h?revision=92312&view=markup)这里。我实验了一下，通了。 Messaging接口很好，传递的消息可以自已定义，类型也无限制，非常方便。 > foruok原创，如需转载请关注foruok的微信订阅号“程序视界”联系foruok。 # 使用postMessage通信 Messaging接口与其它大多数接口一样，分PPB和PPP两侧。分开来说明一下要做的事情。 ### 插件侧要做这么些事情： 1. 实现PPP_Messaging接口，关键是void (*HandleMessage)(PP_Instance instance, struct PP_Var message)方法 1. 在Get_Interface中返回名字是PPP_MESSAGING_INTERFACE的接口 1. 在PPP_InitializeModule中获取 PPB_Messaging、PPB_Var、PPB_VarArray、PPB_VarDictionary等接口。 PPB_Messaging的PostMessage用于向浏览器发送消息，发送过去的消息，JS代码可以接收到。 PPB_Var可以用来构造String类型的Var，可以操作Var的引用计数 PPB_VarArray是数组接口，可以创建、访问、设置数组 PPB_VarDictionary是字典（map）接口，可以创建字典Var，可以存取key-value对。 1. PPP_Messaging的HandleMessage处理浏览器的消息，如果需要，调用PPB_Messaging的PostMessage发送消息. 注意，插件侧调用PPB_Var接口的VarFromUtf8时，传入的len不包括’\0’在内。PPAPI的ppb_var.h的注释里的示例代码片段有误，调用时传递的长度是sizeof(hello_world)，应该减去一。还有一点，插件和浏览器交互的数据，都是数据的拷贝哦，调用接口会发生复制行为。 ### 浏览器侧浏览器侧可以使用JavaScript来监听插件发送的message事件，也可以使用插件元素的postMessage发送消息给插件。基本上做下面几件事即可： 1. 实现处理消息的JS函数，其参数是MessageEvent，data成员为插件发过来的信息，可以当做JS对象来访问。 1. 监听插件的message事件 1. 在合适的时候调用插件的postMessage(object)方法发送消息给插件 # 代码分插件代码和HTML代码。 ### 插件代码代码是在[**在PPAPI插件中创建本地窗口**](http://blog.csdn.net/foruok/article/details/50513228)一文示例代码的基础上改的，添加了消息处理的部分。只贴相关的部分了。 **获取消息相关接口的代码** 在PPP_InitializeModule中添加了获取PPB_Messaging接口以及其它可能用到的PP_Var类型的接口，有Array和Dictionary。 ~~~ g_var_interface = (const PPB_Var*)get_browser_interface(PPB_VAR_INTERFACE); g_dictionary_interface = (const PPB_VarDictionary*)get_browser_interface(PPB_VAR_DICTIONARY_INTERFACE); g_array_interface = (const PPB_VarArray*)get_browser_interface(PPB_VAR_ARRAY_INTERFACE); g_message_interface = (const PPB_Messaging*)get_browser_interface(PPB_MESSAGING_INTERFACE); ~~~ **PPP_Messaging接口的实现** PPP_Messaging接口的实现代码如下： ~~~ void Plugin_HandleMessage(PP_Instance instance, struct PP_Var message) { char szLog[256] = { 0 }; sprintf_s(szLog, 256, "Plugin_HandleMessage, type = %d\r\n", message.type); OutputDebugStringA(szLog); if (message.type == PP_VARTYPE_DICTIONARY) { char command[] = "command"; struct PP_Var commandKey = g_var_interface->VarFromUtf8(command, sizeof(command) - 1); struct PP_Var commandVar = g_dictionary_interface->Get(message, commandKey); int len = 0; const char *strCommand = g_var_interface->VarToUtf8(commandVar, &len); g_var_interface->Release(commandKey); sprintf_s(szLog, 256, "Plugin_HandleMessage, dict, command = %s, len = %d\r\n", strCommand, len); OutputDebugStringA(szLog); if (len == 0) { OutputDebugString(_T("Tang_plugin, recv invalid command\r\n")); g_var_interface->Release(commandVar); return; } if (strncmp(strCommand, "joinConf", len) == 0) { char confIdKey[] = "confId"; char userNameKey[] = "userName"; char *szConfId = 0; char*szUserName = 0; struct PP_Var idKey = g_var_interface->VarFromUtf8(confIdKey, sizeof(confIdKey) - 1); struct PP_Var userKey = g_var_interface->VarFromUtf8(userNameKey, sizeof(userNameKey) - 1); struct PP_Var var = g_dictionary_interface->Get(message, idKey); const char *value = g_var_interface->VarToUtf8(var, &len); if (len > 0) { szConfId = malloc(len + 1); strncpy_s(szConfId, len+1, value, len); szConfId[len] = 0; } g_var_interface->Release(var); var = g_dictionary_interface->Get(message, userKey); value = g_var_interface->VarToUtf8(var, &len); if (len > 0) { szUserName = malloc(len + 1); strncpy_s(szUserName, len+1, value, len); szUserName[len] = 0; } g_var_interface->Release(var); sprintf_s(szLog, 256, "Plugin_HandleMessage, dict, command = joinConf, user = %s, confId = %s\r\n", szUserName, szConfId); OutputDebugStringA(szLog); if (szConfId && szUserName) { sprintf_s(szLog, 256, "plugin got confId - %s, user - %s\r\n", szConfId, szUserName); OutputDebugStringA(szLog); joinConf(szConfId, szUserName); } else { OutputDebugString(_T("Invalid conference id or userName\r\n")); } if (szConfId) free(szConfId); if (szUserName) free(szUserName); g_var_interface->Release(idKey); g_var_interface->Release(userKey); /* fake attendees*/ char szMsgTypeValue[] = "userlist"; char szTypeKey[] = "type"; struct PP_Var typeKey = g_var_interface->VarFromUtf8(szTypeKey, sizeof(szTypeKey) - 1); struct PP_Var typeValue = g_var_interface->VarFromUtf8(szMsgTypeValue, sizeof(szMsgTypeValue) - 1); struct PP_Var attendee = g_dictionary_interface->Create(); g_dictionary_interface->Set(attendee, typeKey, typeValue); struct PP_Var userArray = g_array_interface->Create(); char szUser1[] = "ZhangSan"; char szUser2[] = "LiSi"; struct PP_Var user1 = g_var_interface->VarFromUtf8(szUser1, sizeof(szUser1) - 1); struct PP_Var user2 = g_var_interface->VarFromUtf8(szUser2, sizeof(szUser2) - 1); g_array_interface->Set(userArray, 0, user1); g_array_interface->Set(userArray, 1, user2); char szValueKey[] = "value"; struct PP_Var valueKey = g_var_interface->VarFromUtf8(szValueKey, sizeof(szValueKey) - 1); g_dictionary_interface->Set(attendee, valueKey, userArray); g_message_interface->PostMessage(instance, attendee); OutputDebugString(_T("Post attendee to browser")); g_var_interface->Release(typeKey); g_var_interface->Release(typeValue); g_var_interface->Release(user1); g_var_interface->Release(user2); g_var_interface->Release(valueKey); g_var_interface->Release(userArray); g_var_interface->Release(attendee); } else if (strncmp(strCommand, "viewVideo", len) == 0) { char userIdKey[] = "userId"; char *szUserId = 0; struct PP_Var idKey = g_var_interface->VarFromUtf8(userIdKey, sizeof(userIdKey) - 1); struct PP_Var var = g_dictionary_interface->Get(message, idKey); const char *value = g_var_interface->VarToUtf8(var, &len); if (len > 0) { szUserId = malloc(len + 1); strncpy_s(szUserId, len + 1, value, len); szUserId[len] = 0; } if (szUserId) { sprintf_s(szLog, 256, "plugin got userId - %s\r\n", szUserId); OutputDebugStringA(szLog); viewVideo(szUserId, g_child_window); } else { OutputDebugString(_T("Invalid viewVideo command without userId\r\n")); } if (szUserId) free(szUserId); g_var_interface->Release(var); g_var_interface->Release(idKey); } g_var_interface->Release(commandVar); } else if (message.type == PP_VARTYPE_STRING) { char hello_world[] = "Hello world!"; struct PP_Var var = g_var_interface->VarFromUtf8(hello_world, sizeof(hello_world) - 1); g_message_interface->PostMessage(instance, var); // var will be copyed g_var_interface->Release(var); } } static PPP_Messaging message_interface = { &Plugin_HandleMessage }; ~~~ 有点长，比较潦草。 **返回PPP_Messaging的代码** 完整的PPP_GetInterface函数如下： ~~~ PP_EXPORT const void* PPP_GetInterface(const char* interface_name) { if (strcmp(interface_name, PPP_INSTANCE_INTERFACE) == 0) { OutputDebugString(_T("PPP_GetInterface, instance_interface\r\n")); return &instance_interface; } else if (strcmp(interface_name, PPP_INPUT_EVENT_INTERFACE) == 0) { OutputDebugString(_T("PPP_GetInterface, input_interface\r\n")); return &input_interface; } else if (strcmp(interface_name, PPP_MESSAGING_INTERFACE) == 0) { OutputDebugString(_T("PPP_GetInterface, message_interface\r\n")); return &message_interface; } return NULL; } ~~~ ### 网页代码网页代码如下： ~~~ <!DOCTYPE html> <html>  <head> <style type="text/css"> #contacts { margin: 10px; width: 300px; height: 200px; background-color: gray; } </style> <script type="text/javascript"> function handleMessage(message) { alert(message.data.type); if(message.data.type.localeCompare("userlist") == 0){ var i = 0; ul = document.getElementById("attendee"); for(; i < message.data.value.length; i++){ var li = document.createElement("li"); li.appendChild(document.createTextNode(message.data.value[i])); ul.appendChild(li); } } } function joinConference(){ plugin = document.getElementById('tangplugin'); plugin.postMessage({ command:"joinConf", confId: document.getElementById("confId").value, userName: document.getElementById("userName").value }); } function viewSharedVideo(){ plugin = document.getElementById('tangplugin'); plugin.postMessage({ command:"viewVideo", userId: document.getElementById("userId").value }); } function initialize() { plugin = document.getElementById('tangplugin'); plugin.addEventListener('message', handleMessage, false); } document.addEventListener('DOMContentLoaded', initialize, false); </script> <title>Tang in Plugin</title> </head> <body> <form> ConferenceID: <input type="text" id="confId" />  User: <input type="text" id="userName" />  <input type="button" value="Join" onclick="joinConference()"/> </form> <hr> <div id="contacts"> <p>contacts:</p> <ul id="attendee">  </ul> UserId:<input type="text" id="userId" />  <button type="button" onclick="viewSharedVideo()">View Video</button> </div> <p>share video:</p> <embed id="tangplugin" type="application/x-ppapi-tang-video" width="300px" height="200px" top="40px" left="20px"> </body> </html> ~~~ Join按钮会获取它前面两个文本框的内容，发送给插件，插件返回一个用户列表，网页解析（HandleMessage方法）出来，动态修改用户列表。 # 运行效果贴两幅图，点击Join按钮之前是酱紫的： ![before](https://docs.gechiui.com/gc-content/uploads/sites/kancloud/2016-02-22_56caac341008d.jpg "") 点击Join按钮后是酱紫的： ![after](https://docs.gechiui.com/gc-content/uploads/sites/kancloud/2016-02-22_56caac34279dc.jpg "") 其他参考文章： - [**CEF Windows开发环境搭建**](http://blog.csdn.net/foruok/article/details/50468642) - [**CEF加载PPAPI插件**](http://blog.csdn.net/foruok/article/details/50485448) - [**VS2013编译最简单的PPAPI插件**](http://blog.csdn.net/foruok/article/details/50485461) - [**理解PPAPI的设计**](http://blog.csdn.net/foruok/article/details/50486788) - [**PPAPI插件与浏览器的交互过程**](http://blog.csdn.net/foruok/article/details/50494061) - [**Windows下从源码编译CEF**](http://blog.csdn.net/foruok/article/details/50498740) - [**编译PPAPI的media_stream_video示例**](http://blog.csdn.net/foruok/article/details/50498873) - [**PPAPI插件的绘图与输入事件处理**](http://blog.csdn.net/foruok/article/details/50499813) - [**在PPAPI插件中创建本地窗口**](http://blog.csdn.net/foruok/article/details/50513228)