Call a Javascript function from C++

[winapiwrapper]

Hi,

I am creating a chat client with CEF3 on Windows 8.1.
I created a message-only window which can receive network messages at any time.

I would like to call Javascript functions by their name and without registering the callback via Javascript, like in this example: https://bitbucket.org/chromiumembedded/cef/wiki/JavaScriptIntegration.md#markdown-header-executing-functions.

I could use ExecuteJavascript, but will it be able to handle large strings containing Javascript objects? (those objects may contain binary data)

How to achieve this? Network messages can arrive at any time, that's why the solution needs to be thread-safe.

Also, how to access V8 from a C++ function and from outside the render process? C++ calls will come from the message-only window, but I don't know how to forward them.

[Czarek]

Big data should be sent to javascript using network layer.

You can communicate with V8 renderer process using IPC messaging.

[winapiwrapper]

What do you mean by "network layer"? I use Winsock to handle network operations.

IPC is pretty slow, can't I just call a Javascript function whenever I want in my C++ code, using V8?

[winapiwrapper]

Do I really need to use IPC if I want to achieve that?

[winapiwrapper]

I'm new to CEF, could anybody give me a hint?
Can I execute Javascript from any thread in my C++ app?

[magreenblatt]

V8 functions can only be called from inside the renderer process. IPC is documented here: https://bitbucket.org/chromiumembedded/ ... t-bindings

[winapiwrapper]

Thank you!

I wrote the code below, but CefV8Context::GetCurrentContext is null when a message is received by the renderer.
ClientApp is my CefApp implementation and is defined like this: class ClientApp : public CefApp, public CefBrowserProcessHandler, public CefRenderProcessHandler

Code: Select all

bool ClientApp::OnProcessMessageReceived(CefRefPtr<CefBrowser> browser, CefProcessId source_process, CefRefPtr<CefProcessMessage> message)
{
   const std::string& msg = message->GetName();

   if (CefCurrentlyOn(TID_RENDERER))
   {      
      std::cout << "renderer" << std::endl;
      CefRefPtr<CefV8Context> context = CefV8Context::GetCurrentContext();
      std::cout << context << std::endl; // =00000000
      if (context != NULL)
      {
         CefV8ValueList args;
         MyV8Handler::g_callback->ExecuteFunctionWithContext(context, NULL, args);
      }

      return true;
   }

   return false;
}

In order to call my JS function, I created a thread in my browser process. This thread sends a message to the renderer which should execute a JS callback registered beforehand.
Here's what my thread does:

Code: Select all

// waits a few seconds
// then:
CefRefPtr<CefProcessMessage> message = CefProcessMessage::Create(CefString("msg"));
   CefRefPtr<CefListValue> args = message->GetArgumentList();
   args->SetInt(0, 1);
   args->SetString(1, CefString("hi v8!"));

   browser->SendProcessMessage(PID_RENDERER, message);

Did I miss something? CefCurrentlyOn(TID_RENDERER) is true so I don't understand why GetCurrentContext is null.

[magreenblatt]

You will only have a current context when you enter C++ code from JS. Use CefFrame::GetV8Context for your use case.

[winapiwrapper]

Thank you very much! It works like a charm now!