CefV8Callback::Execute not invoked

[nassersh]

I already understand that JS Callbacks have to be invoked in the render process. As such, here's the C++:

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class App : public CefApp, public CefRenderProcessHandler
{
    virtual CefRefPtr<CefRenderProcessHandler> GetRenderProcessHandler() OVERRIDE { return this; }
   
    virtual void OnContextCreated(
        CefRefPtr<CefBrowser> browser,
        CefRefPtr<CefFrame> frame,
        CefRefPtr<CefV8Context> context) OVERRIDE
    {
        m_clientHandler = new ClientHandler; // see below
        CefRefPtr<CefV8Value> object = context->GetGlobal();
        object->SetValue("register", CefV8Value::CreateFunction("register", m_clientHandler), V8_PROPERTY_ATTRIBUTE_NONE);
    }
};

class ClientHandler :
    public CefClient,
    public CefLifeSpanHandler,
    public CefV8Handler
{
    ClientHandler();

    virtual void OnAfterCreated(...) OVERRIDE;

    virtual bool Execute(...) OVERRIDE;
};


And the JavaScript:

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function somefunc(arg) {
    // Do stuff
}

window.register(somefunc);


Interestingly enough, commenting out the 'window.register(somefunc)' line causes the page to work just fine (without the desired JS, obviously), but uncommenting it causes the page to not load. In addition to this, calling

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alert(window.register);


Pops up an alert window that says 'function() { [native code] }', if that means anything. I've looked at http://www.magpcss.org/ceforum/viewtopic.php?f=6&t=12909 already I've also passed the app.get() instance to CefInitialize(). Any ideas?

[magreenblatt]

What is your CefV8Handler::Execute implementation? Also, you should implement CefV8Handler in a separate object from ClientHandler.

[nassersh]

Thanks for your quick response.

As per the recommendation, I've separated the CefV8Handler from ClientHandler.

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// Just implements GetLifeSpanHandler() and a constructor
class ClientHandler : public CefClient, public CefLifeSpanHandler


And created a new CefV8Handler. I've provided the Execute() implementation below, but I should note that the function is not being entered. In other words, if you run a debugger and place a break point at the first line of Execute(), it is never hit, and the web browser occasionally displays an empty window. On the other hand, the page renders correctly when the 'window.register(someFunc)' line is commented out in the JavaScript, but obviously without registering the callback.

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class JSCallbackHandler : public CefV8Handler
{
public:
    bool Execute(
        const CefString& name,
        CefRefPtr< CefV8Value > object,
        const CefV8ValueList& arguments,
        CefRefPtr< CefV8Value >& retval,
        CefString& exception ) OVERRIDE
    {
        if (name == "register" && arguments.size() == 1 && arguments[0]->IsFunction())
        {
            m_callback = arguments[0];
            m_context = CefV8Context::GetCurrentContext();
            return true;
        }
        return false;
    }

private:
    CefRefPtr<CefV8Value> m_callback;
    CefRefPtr<CefV8Context> m_context;

    IMPLEMENT_REFCOUNTING(JSCallbackHandler);
}


Finally, the app class changes to:

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class App : public CefApp, public CefRenderProcessHandler
{
    virtual CefRefPtr<CefRenderProcessHandler> GetRenderProcessHandler() OVERRIDE { return this; }
   
    virtual void OnContextCreated(
        CefRefPtr<CefBrowser> browser,
        CefRefPtr<CefFrame> frame,
        CefRefPtr<CefV8Context> context) OVERRIDE
    {
        m_clientHandler = new ClientHandler;
        CefRefPtr<CefV8Value> object = context->GetGlobal();
        CefRefPtr<CefV8Handler> handler = new JSCallbackHandler;
        object->SetValue("register", CefV8Value::CreateFunction("register", handler), V8_PROPERTY_ATTRIBUTE_NONE);
    }
};


[amaitland]

How are you attaching the debugger to the render process? Are you able to set a breakpoint anywhere in the code?

https://www.chromium.org/developers/how ... e-renderer

[nassersh]

Okay, I see the issue now. The Execute() method is being entered, I just couldn't tell because I was using the standard packaged debugger that comes with Visual Studio.