Gtk应用内嵌网页与原生代码交互方法

在使用Gtk开发应用程序的过程中，如果需要内嵌网页，那么使用libwebkit2gtk是个非常自然和正确的选择。那么这里就可能原生程序代码可能需要跟网页交互的问题。

Gtk程序跟网页的交互，主要有两个方面：

1 Gtk程序需要调用网页js代码
2 网页需要调用Gtk程序的功能代码

需求1，使用webkit2gtk的内置webkit_web_view_run_javascript函数即可解决

需求2，使用webkit2gtk的内置的web extendsion扩展支持功能解决 或 window.webkit.messageHandlers..postMessage(value)

不多说看代码吧！

Gtk嵌入网页Demo程序

webviewgtk.c

/**
*
* Copyright (C) 2020 Wei Keting<weikting@gmail.com>. All rights reserved.
* @Time : 2021-04-04 12:18
* @Last Modified: 2022-12-10 17:27
* @File : webviewgtk.c
* @Description :
*
* 依赖下载：
* sudo apt install libwebkit2gtk-4.0-doc libwebkit2gtk-4.0-dev libgtk-3-dev
* gcc webviewgtk.c -o webviewgtk -D_GNU_SOURCE -g3 -Wall `pkg-config --cflags --libs webkit2gtk-4.0`
*
*/


#include <gtk/gtk.h>
#include <glib.h>
#include <webkit2/webkit2.h>

#include <sys/types.h>
#include <unistd.h>

static void
web_view_javascript_finished (GObject      *object,
                              GAsyncResult *result,
                              gpointer      user_data)
{
    WebKitJavascriptResult *js_result;
    JSCValue               *value;
    GError                 *error = NULL;

    js_result = webkit_web_view_run_javascript_finish (WEBKIT_WEB_VIEW (object), result, &error);
    if (!js_result) {
        g_warning ("Error running javascript: %s", error->message);
        g_error_free (error);
        return;
    }

    value = webkit_javascript_result_get_js_value (js_result);
    if (jsc_value_is_string (value)) {
        JSCException *exception;
        gchar        *str_value;

        str_value = jsc_value_to_string (value);
        exception = jsc_context_get_exception (jsc_value_get_context (value));
        if (exception)
            g_warning ("Error running javascript: %s", jsc_exception_get_message (exception));
        else
            g_print ("Script result: %s\n", str_value);
        g_free (str_value);
    } else {
        g_warning ("Error running javascript: unexpected return value");
    }
    webkit_javascript_result_unref (js_result);
}

static gboolean
on_webview_load_failed(WebKitWebView  *webview,
               WebKitLoadEvent load_event,
               gchar          *failing_uri,
               GError         *error,
               gpointer        user_data)
{
    g_printerr("%s: %s\n",failing_uri,error->message);
    return FALSE;
}

static void
handle_script_message (
  WebKitUserContentManager* self,
  WebKitJavascriptResult* js_result,
  gpointer user_data)
{
    JSCValue               *value;
    value = webkit_javascript_result_get_js_value (js_result);

    JSCException *exception;
    gchar        *str_value;

    str_value = jsc_value_to_string (value);
    exception = jsc_context_get_exception (jsc_value_get_context (value));
    if (exception)
        g_warning ("Error running javascript: %s", jsc_exception_get_message (exception));
    else
        g_printerr ("Script result: %s\n", str_value);

    g_printerr("%s: %s\n",__func__,str_value);

    g_free (str_value);

}

static void
on_button_clicked(GtkButton *button,
               WebKitWebView *webview)
{
    static gint t = 0;
    gchar buf[128]={0};
    g_snprintf(buf,sizeof(buf)-1,"change_span_id('_n%d')",t);
    t+=1;
    //在webview当前的html页面中直接运行js代码
    webkit_web_view_run_javascript(webview,buf,NULL,web_view_javascript_finished,NULL);
}

static void
webkit_web_extension_initialize (WebKitWebContext *context,
               gpointer          user_data)
{
    g_printerr("%s: %d\n",__FUNCTION__,getpid());
    //设置web extendsion扩张.so文件的搜索目录
    webkit_web_context_set_web_extensions_directory(context,".");
}


/**
** 创建window，添加webkit控件
**
**/
static void
on_activate (GtkApplication *app)
{
    GtkWindow *window;

    g_assert (GTK_IS_APPLICATION (app));

    window = gtk_application_get_active_window (app);
    if (window == NULL)
        window = g_object_new (GTK_TYPE_WINDOW,
                               "application", app,
                               "default-width", 600,
                               "default-height", 300,
                               NULL);

    //注册处理web extensions的初始化函数
    g_signal_connect(webkit_web_context_get_default(),"initialize-web-extensions",G_CALLBACK(webkit_web_extension_initialize),NULL);

    GtkWidget* webview = webkit_web_view_new();
    g_signal_connect (webview, "load-failed", G_CALLBACK (on_webview_load_failed), NULL);


    // 加载网页
    GFile *file = g_file_new_for_path("webview.html");
    gchar *uri = g_file_get_uri(file);
    webkit_web_view_load_uri(WEBKIT_WEB_VIEW(webview), uri);
    g_free(uri);
    g_object_unref(file);
    
    // 注册 window.webkit.messageHandlers.msgToNative.postMessage(value)
    // 的回调函数
    WebKitUserContentManager *manager = webkit_web_view_get_user_content_manager (WEBKIT_WEB_VIEW(webview));
    g_signal_connect (manager, "script-message-received::msgToNative",
                    G_CALLBACK (handle_script_message), NULL);
    webkit_user_content_manager_register_script_message_handler (manager, "msgToNative");

    GtkWidget *vbox = gtk_box_new(GTK_ORIENTATION_VERTICAL,0);
    GtkWidget *button = gtk_button_new_with_label ("change span");
    gtk_box_pack_start(GTK_BOX(vbox),GTK_WIDGET(webview),TRUE,TRUE,0);
    gtk_box_pack_start(GTK_BOX(vbox),GTK_WIDGET(button),FALSE,TRUE,0);
    
    gtk_container_add(GTK_CONTAINER(window),GTK_WIDGET(vbox));
    gtk_widget_show_all(GTK_WIDGET(vbox));
    gtk_window_present (window);
    
    g_signal_connect (button, "clicked", G_CALLBACK (on_button_clicked), webview);

}

int
main (int   argc,
      char *argv[])
{
    g_autoptr(GtkApplication) app = NULL;
    int ret;

    app = gtk_application_new ("com.weiketing.webkit_webview", G_APPLICATION_FLAGS_NONE);

    g_signal_connect (app, "activate", G_CALLBACK (on_activate), NULL);

    ret = g_application_run (G_APPLICATION (app), argc, argv);

    return ret;
}

Web Extension Demo

web_exten.c

/**
*
* Copyright (C) 2020 Wei Keting<weikting@gmail.com>. All rights reserved.
* @Time : 2021-04-04 12:18
* @File : web_exten.c
* @Description :
*
* 依赖下载：
* sudo apt install libwebkit2gtk-4.0-doc libwebkit2gtk-4.0-dev libgtk-3-dev
* gcc  web_exten.c -o libweb_exten.so -shared -Wl,-soname,libweb_exten.so -D_GNU_SOURCE -g3 -Wall `pkg-config --cflags --libs webkit2gtk-4.0`
**/

#include <glib.h>
#include <webkit2/webkit-web-extension.h>
#include <sys/types.h>
#include <unistd.h>

static gint
js_app_add(gpointer *first,gint num)
{
    static gint N = 0;
    g_printerr("%s: %p\n",__FUNCTION__,first);
    N += num;
    return N;
}

static void 
window_object_cleared_callback (WebKitScriptWorld *world, 
                                WebKitWebPage     *web_page, 
                                WebKitFrame       *frame, 
                                gpointer           user_data)
{
    JSCContext* jsContext;

    jsContext = webkit_frame_get_js_context_for_script_world (frame, world);

    //添加一个js全局变量gtkValue
    jsc_context_set_value(jsContext,"gtkValue",jsc_value_new_string(jsContext,"__test_js_exten"));
    /* Use JSC API to add the JavaScript code you want */
    
    //注册一个名为NativeTest的js类
    JSCClass* app = jsc_context_register_class(jsContext,"NativeTest",NULL,NULL,NULL); // g_object_new(JSC_TYPE_CLASS,"name","JSApp","context",jsContext,NULL);


    //给JSCClass类添加add方法
    jsc_class_add_method(app,"add",G_CALLBACK(js_app_add),NULL,NULL,G_TYPE_INT,1,G_TYPE_INT,NULL);

    //创建一个obj，作为JSCClass类绑定实例，JSCClass方法回调的第一个参数就是obj
    GObject *obj = g_object_new(G_TYPE_OBJECT,NULL);
    jsc_context_set_value(jsContext,"GtkNative",jsc_value_new_object(jsContext,obj,app));
    g_printerr("%s: %d %p\n",__FUNCTION__,getpid(),obj);
    g_object_unref(obj);
}

G_MODULE_EXPORT void
webkit_web_extension_initialize (WebKitWebExtension *extension)
{
    //web extension的初始化函数
    g_signal_connect (webkit_script_world_get_default (), 
                      "window-object-cleared", 
                      G_CALLBACK (window_object_cleared_callback), 
                      NULL);
}

内嵌的网页示例，webview.html

<!DOCTYPE html>
<html lang="zh">
<!--filename: webview.html -->
<head>
    <meta charset="utf-8"/>
    <meta http-equiv="Content-Language" content="zh-CN">
    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"/>
    <meta name="referrer" content="always"/>
    <title>Webkit Webview test</title>
    <script type="text/javascript">
    
    function change_span_id(v=''){
        //alert("test")
        document.getElementById('span_id').innerHTML = 'test'+v+gtkValue
        return v
    }
    
    function native_add(num){
        //调用自定义添加的js接口
        i= GtkNative.add(num)
        document.getElementById('add').innerHTML = i
    }

    function send2Gtk(){
        e = document.getElementById('msg')
        window.webkit.messageHandlers.msgToNative.postMessage(e.value)
    }
    </script>
</head>
<body>
    <span>words for test: </span><span id="span_id"></span>
    <br/>
    <button onclick="change_span_id()">change span id</button>
    <br/>
    <span>Native add: </span><span id='add'></span>
    <br/>
    <button onclick="native_add(2)">Native Add</button>
    <br/>
    <input type="text" id="msg" />
    <br/>
    <button onclick="send2Gtk()">Send to Native</button>
</body>
</html>

Web Extension相比于window.webkit.messageHandlers..postMessage(value)

的优点是有返回值。

示例运行

安装依赖：

sudo apt install libwebkit2gtk-4.0-doc libwebkit2gtk-4.0-dev libgtk-3-dev

把webviewgtk.c，web_exten.c, webview.html放在同一目录下。

编译程序：

gcc  web_exten.c -o libweb_exten.so -shared -Wl,-soname,libweb_exten.so -D_GNU_SOURCE -g3 -Wall `pkg-config --cflags --libs webkit2gtk-4.0`
gcc webviewgtk.c -o webviewgtk -D_GNU_SOURCE -g3 -Wall `pkg-config --cflags --libs webkit2gtk-4.0`

运行程序：

./webviewgtk