text: #include <sys/socket.h>
  #include <sys/stat.h>
  #include <fcntl.h>
  #include <inttypes.h>
  #include <limits.h>
  #include <stdio.h>
  #include <stdlib.h>
  
  #include <gio/gio.h>
  #include <webkit2/webkit-web-extension.h>
  #include <webkitdom/webkitdom.h>
  #include <webkitdom/WebKitDOMDOMWindowUnstable.h>
  
  #include "common.h"
  
  #define LENGTH(x)   (sizeof(x) / sizeof(x[0]))
  
  static WebKitWebExtension *webext;
  static int sock;
  
  static void
  msgsurf(guint64 pageid, const char *s)
  {
  	static char msg[MSGBUFSZ];
  	size_t sln = strlen(s);
  	int ret;
  
  	if ((ret = snprintf(msg, sizeof(msg), "%c%s", pageid, s))
  	    >= sizeof(msg)) {
  		fprintf(stderr, "webext: msg: message too long: %d\n", ret);
  		return;
  	}
  
  	if (send(sock, msg, ret, 0) < 0)
  		fprintf(stderr, "webext: error sending: %s\n", msg+1);
  }
  
  static gboolean
  readsock(GIOChannel *s, GIOCondition c, gpointer unused)
  {
  	static char js[48], msg[MSGBUFSZ];
  	WebKitWebPage *page;
  	JSCContext *jsc;
  	GError *gerr = NULL;
  	int jslen = 0;
  	gsize msgsz;
  
  	if (g_io_channel_read_chars(s, msg, sizeof(msg), &msgsz, &gerr) !=
  	    G_IO_STATUS_NORMAL) {
  		if (gerr) {
  			fprintf(stderr, "webext: error reading socket: %s\n",
  			        gerr->message);
  			g_error_free(gerr);
  		}
  		return TRUE;
  	}
  
  	if (msgsz < 2) {
  		fprintf(stderr, "webext: readsock: message too short: %d\n",
  		        msgsz);
  		return TRUE;
  	}
  
  	if (!(page = webkit_web_extension_get_page(webext, msg[0])))
  		return TRUE;
  
  	jsc = webkit_frame_get_js_context(webkit_web_page_get_main_frame(page));
  
  	switch (msg[1]) {
  	case 'h':
  		if (msgsz != 3)
  			return TRUE;
  		jslen = snprintf(js, sizeof(js),
  		                 "window.scrollBy(window.innerWidth/100*%d,0);",
  		                 msg[2]);
  		break;
  	case 'v':
  		if (msgsz != 3)
  			return TRUE;
  		jslen = snprintf(js, sizeof(js),
  		                 "window.scrollBy(0,window.innerHeight/100*%d);",
  		                 msg[2]);
  		break;
  	}
  	if (jslen) jsc_context_evaluate(jsc, js, -1);
  	return TRUE;
  }
  
  G_MODULE_EXPORT void
  webkit_web_extension_initialize_with_user_data(WebKitWebExtension *e,
                                                 const GVariant *gv)
  {
  	GIOChannel *gchansock;
  
  	webext = e;
  
  	g_variant_get(gv, "i", &sock);
  
  	gchansock = g_io_channel_unix_new(sock);
  	g_io_channel_set_encoding(gchansock, NULL, NULL);
  	g_io_channel_set_flags(gchansock, g_io_channel_get_flags(gchansock)
  	                       | G_IO_FLAG_NONBLOCK, NULL);
  	g_io_channel_set_close_on_unref(gchansock, TRUE);
  	g_io_add_watch(gchansock, G_IO_IN, readsock, NULL);
  }
  