CEF - Scheme Handler and XMLHttpRequest

[Staxcelrom]

Please explain how to create a "Scheme Handler" in CEF, in order to be able to send data from Javascript code to C++ by calling XMLHttpRequest.

I'm trying to follow this enter link description here:

CefRegisterSchemeHandlerFactory:

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class my_CEF__application_callback_class : public CefApp, public CefBrowserProcessHandler, public CefRenderProcessHandler
{

    void OnContextInitialized() override
    {
        CefRefPtr<MySchemeHandlerFactory>my_SchemeHandlerFactory_ptr;
        my_SchemeHandlerFactory_ptr = new my_SchemeHandlerFactory_class();

        CefRegisterSchemeHandlerFactory("http", "my_binary_app", my_SchemeHandlerFactory_ptr);
    }

}

my_SchemeHandlerFactory_class:

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class my_SchemeHandlerFactory_class: public CefSchemeHandlerFactory
{
public:

    virtual CefRefPtr<CefResourceHandler> Create(CefRefPtr<CefBrowser> browser, CefRefPtr<CefFrame> frame, const CefString& scheme_name, CefRefPtr<CefRequest> request) override
    {
        std::cout << "Create" << std::endl;


        CefRefPtr<CefResourceHandler>my_CefResourceHandler_ptr;
        my_CefResourceHandler_ptr = new my_ResourceHandler_class();

        return my_CefResourceHandler_ptr;
    }

    IMPLEMENT_REFCOUNTING(MySchemeHandlerFactory);
};

my_ResourceHandler_class:

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class my_ResourceHandler_class: public CefResourceHandler
{

public:

    virtual bool Open(CefRefPtr<CefRequest> request, bool& handle_request, CefRefPtr<CefCallback> callback) override
    {
        std::cout << "Open" << std::endl;

        handle_request = false;
        return false;
    }

    virtual void GetResponseHeaders(CefRefPtr<CefResponse> response, int64& response_length, CefString& redirectUrl) override
    {
        std::cout << "GetResponseHeaders" << std::endl;
    }


    virtual bool Read(void* data_out, int bytes_to_read, int& bytes_read, CefRefPtr<CefResourceReadCallback> callback) override
    {
        std::cout << "Read" << std::endl;

        return true;
    }


private:
    IMPLEMENT_REFCOUNTING(MyResourceHandler);
};

And from javascript I call the following code:

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std::string my_JS_code =

"let URL = \"http://my_binary_app\";"         

"let my_req = new XMLHttpRequest();"
"my_req.open(\"GET\", URL);"

"let my_let = \"Hello\";"
"my_req.send(my_let);";

(browser)->GetMainFrame()->ExecuteJavaScript(my_JS_code, "", 1);

And at the end - after executing the JS code - I expect to call the methods of the my_ResourceHandler_class class, but absolutely nothing happens.

I'm obviously doing something wrong, but I can't figure out what exactly I'm doing wrong.

[magreenblatt]

See https://bitbucket.org/chromiumembedded/ ... e_handler/

[Staxcelrom]

Works. Apparently the browser does not pass requests over HTTP, only over HTTPS.

But, for some reason, not calling XMLHttpRequest:

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"let URL = \"https://my_binary_app\";"       

"let my_req = new XMLHttpRequest();"
"my_req.open(\"GET\", URL);"

"let my_let = \"Hello\";"
//or
"let blob = new Blob(['abc123'], { type: 'text/plain' });"

"my_req.send(blob);";

But why is strange data coming into the Read method:

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class MyResourceHandler : public CefResourceHandler
{

public:


   virtual bool Read(void* data_out, int bytes_to_read, int& bytes_read, CefRefPtr<CefResourceReadCallback> callback) override
   {
      bytes_read = bytes_to_read;                              //Always 65536

      std::string my_string;
                my_string.resize(bytes_read);

      memcpy(&my_string[0], data_out, bytes_to_read);

      std::cout << string_GLOBALity << std::endl;     //EMPTY - All bytes == null

      return true;
   }
}


[magreenblatt]

But why is strange data coming into the Read method:

You are supposed to return your data by writing into |data_out|. See the docs.

[Staxcelrom]

But why is strange data coming into the Read method:

You are supposed to return your data by writing into |data_out|. See the docs.

I have already read the description for "Read" about 20 times.

And I can't figure out what it says::

READ response data. If data is available...

How I know - what data is available? by what parameter?

copy up to |bytes_to_read| bytes INTO |data_out|

Copy FROM ?

[magreenblatt]

The browser is reading response data from your CefResourceHandler. What did you think CefResourceHandler was for?

[Staxcelrom]

The browser is reading response data from your CefResourceHandler. What did you think CefResourceHandler was for?

For handling scheme requests.

[magreenblatt]

The browser is reading response data from your CefResourceHandler. What did you think CefResourceHandler was for?

For handling scheme requests.

That’s correct. And what does “handling” mean?

[Staxcelrom]

That’s correct. And what does “handling” mean?

I thought that this was an "interception" of a request with a signature specified in CefRegisterSchemeHandlerFactory(...).
And in Read/ReadResponse - I can get the data that I passed in the XMLHttpRequest request. I'm probably thinking wrong.

After your post - I thought that CefResourceHandler - "intercepts" my XMLHttpRequest request, which I made in js code, and in the Read/ReadResponse method - I have to set the data RESPONSE to this XMLHttpRequest - request.
I tried like this:

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function my_func()
{
let my_text_response = this.responseText; //I thought that here I should get a response, which I set to "Read/ReadResponse", but there was no response. The function "my_func" - was not called.
alert(my_text_response);
}



let URL = "https://my_js_request";     

let my_req = new XMLHttpRequest();
my_req.open(\"GET\", URL);

my_req.onload = my_func;
my_req.send();

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   virtual bool Read(void* data_out, int bytes_to_read, int& bytes_read, CefRefPtr<CefResourceReadCallback> callback) override
   {
      std::cout << "Read" << std::endl;

      bytes_read = sizeof("Hello_JS");

      memcpy(data_out, "Hello_JS", sizeof("Hello_JS"));

      return true;
   }

But that doesn't work either.


I also tried to "catch" my XMLHttpRequest in GetResourceResponseFilter() - but also without success.


And now I don't understand how it should work at all.

[magreenblatt]

I suggest you simplify things and just use CefResourceRequestHandler::GetResourceHandler instead. See https://bitbucket.org/chromiumembedded/ ... terception and the many examples in tests code.