JS binding - breakpoint on FrameCToCpp GetV8Context

[SinnerSmile]

As a continuation to my last post in this topic viewtopic.php?f=6&t=10652&start=10

For a moment I started to think, that I know, what i'm doing, now i'm not so sure.
Long story short: Got Var Ploaded in JS, that will turn to 1 when window.onload event appears, want to check for this value turned 1 in C++, and, as it will happend - do something and turn it to 0. Attempting to do this check in win32 main loop callback function. This way I'm trying to trigger some C++ function on JS event.

Got this code inside callback WndProc:

Code: Select all

        switch(msg) {//cases, cases//}       

   CefRefPtr<CefBrowser> browser;
   CefRefPtr<CefFrame> frame;
   CefRefPtr<CefV8Context> context;
   if (cf_handler.get()) {browser = cf_handler->GetBrowser();}
   if (browser.get()) {frame = browser->GetMainFrame();}
   if (frame.get()) {context = frame->GetV8Context();}
   if (context.get()) {CefRefPtr<CefV8Value> windowobj = context->GetGlobal();
    CefRefPtr<CefV8Value> GetPloaded = windowobj->GetValue("Ploaded");
   int Ploaded = GetPloaded->GetIntValue();

if (Ploaded == 1 && NiceCheck == 1) {
   context->GetGlobal()->SetValue("Ploaded", CefV8Value::CreateInt(0), V8_PROPERTY_ATTRIBUTE_NONE);
   NiceCheck = 0;
   jprint("Page is loaded - CEF");
}
}


   return DefWindowProc(hWnd,msg,wParam,lParam);

jprint prints string into JS div.

This thing builds fine, but on run gives breakpoint
> Brest.exe!CefFrameCToCpp::GetV8Context() Line 324 + 0x14 bytes C++
on
cef_v8context_t* _retval = struct_->get_v8context(struct_); string in frame_ctocpp.cc

I have a bit of simmilar stuff in jprint() function:

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void jprint(gchar *data) {
  CefRefPtr<CefBrowser> browser;
       if (cf_handler.get())
       browser = cf_handler->GetBrowser();

      if (browser.get()) {
  CefRefPtr<CefFrame> frame = browser->GetMainFrame();

 

  gchar *jprint = g_strdup_printf("%s%s%s", "print('", data, "');");

  frame->ExecuteJavaScript(jprint,
    frame->GetURL(), 0);
      }
}

and jprint is triggered by button in WM_COMMAND, works fine, but if I put in this function
CefRefPtr<CefV8Context> context = frame->GetV8Context();,
just to test it, I see the same breakpoint behavior each time I push the button.
Full code, if needed: https://gist.github.com/anonymous/6d9661ffb769d21b5d6c
Sadly, wiki, and cefclient project did not helped me a lot with this =(
Hope for Your help.

[SinnerSmile]

eagerly waiting for answer yet, I'm stuck with this

[magreenblatt]

Why don't you start at a higher level and tell me what you're trying to accomplish. What is the use case?

[SinnerSmile]

OK, Pretty simple case, I want to trigger some C++ function when window.onload JS event occurs, that's it.
Thought of doing it, by checking for JS variable in the main loop (variable set in JS, when window.onload occurs)

[magreenblatt]

OK, Pretty simple case, I want to trigger some C++ function when window.onload JS event occurs, that's it.
Thought of doing it, by checking for JS variable in the main loop (variable set in JS, when window.onload occurs)

1. Create a JS function window object binding as described here.
2. Call the function from JavaScript:

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window.onload = window.myfunc;

[SinnerSmile]

Ah, yes, Thank You, that's far more elegant way, yet, I need to get a V8context. As I get it, there is not so much difference in binding value or function, in particular, something tells me, that, if i drop this binding code in WM_CREATE, I will struck at the same issue with GetV8Context, that I encountered, when trying to bind a value.

Just tested, dropped some lines that gets a frame and then frame->GetV8Context(); in WM_CREATE after CreateBrowserSynch();
same > Brest.exe!CefFrameCToCpp::GetV8Context() Line 324 + 0x14 bytes C++ breakpoint appears
Am I doing something totally wrong?

[magreenblatt]

The V8 context can only be accessed from the renderer process. That is most easily done using the OnContextCreated method. See the GeneralUsage wiki page for useful background information.

[SinnerSmile]

Good evening.
I digged more in this, and I can hope, that I finally understood some obvious things.
Yet, I can't properly trigger C++ function on JS event.
I made small header with classes, that, as I understand it, must implement this function binding, here's the code:

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#ifndef MYV8STUFF_H_
#define MYV8STUFF_H_

#include "include/cef_client.h"

class MyV8handler : public CefV8Handler {

public:
   MyV8handler() { }
   virtual bool Execute(const CefString& name, CefRefPtr<CefV8Value> object, const CefV8ValueList& arguments, CefRefPtr<CefV8Value>& retval, CefString& exception) OVERRIDE
   {
      if (name == "post") {
      // Return my string value.
      retval = CefV8Value::CreateString("TestingJSBinding");
      return true;
      }

    // Function does not exist.
    return false;
   }
   IMPLEMENT_REFCOUNTING(MyV8handler);
};


class WinBindhandler : public CefRenderProcessHandler {

public:
   WinBindhandler() { }
    void OnContextCreated(CefRefPtr<CefBrowser> browser, CefRefPtr<CefFrame> frame, CefRefPtr<CefV8Context> context) OVERRIDE
   {
    // Retrieve the context's window object.
    CefRefPtr<CefV8Value> object = context->GetGlobal();
    // Create an instance of my CefV8Handler object.
    CefRefPtr<CefV8Handler> handler = new MyV8handler();
   
     CefRefPtr<CefV8Value> func = CefV8Value::CreateFunction("post", handler);
   
     object->SetValue("post", func, V8_PROPERTY_ATTRIBUTE_NONE);
   }
   IMPLEMENT_REFCOUNTING(WinBindhandler);
};



#endif

in my main .cpp only added #include "MyV8Stuff.h"

Whole thing compiles well, but not working.
in JS I got window.onload = alert(window.post()); and window.post() on HTML button onclick() event.
On page load i see no alert box, on button click the same, each time Visual studio console gives me
[0111/002858:INFO:CONSOLE(14)] "Uncaught TypeError: Object [object global] has no method 'post'", source: http://localhost:4242/chattest (14)
I set some breakpoints on overrided Execute and OnContextCreated in my classes, they are never triggered.
What am I missing?

[magreenblatt]

You need to implement CefApp to return the CefRenderProcessHandler instance, and pass the CefApp instance into CefExecuteProcess.

[SinnerSmile]

You need to implement CefApp to return the CefRenderProcessHandler instance, and pass the CefApp instance into CefExecuteProcess.

Ah, can't get the idea of how I need exactly to do this on the run without some digging in, can You, maybe, give me some example, or direction where can I find it?