How to pass IWebBrowser2::Navigate2 arguments? - c++

Question

I want to implement Internet Explorer webview control on my window.
I found this answer, on how to do that.
There is a problem: Navigate2 method from the answer is different from the headers I have. In the posters’s code, seems it has only one argument, and maybe others are by default, but I have 5 arguments with the stupidest thing I have ever met - VARIANT type variables (also, in poster’s code it is _variant_t which is undefined for me).
Probably I will never understand the sEiFe logic, why to make instead of Navigate2(wchar_t *,...) cool stuff VARIANT * (I know about Navigate method), but can anyone provide an example of calling that method.
This full code
#include <Windows.h>
#include <Ole2.h>
#include "resource.h"
#include <iostream>
#include <atlbase.h> //activex
#include <atlwin.h> //windows
#include <atlcom.h>
#include "exdisp.h"
#include <comutil.h>
#pragma comment(lib, "comsuppw.lib")
//This will load the browser dll then library and will generate headers
//All the declarations will be in the namespace SHDocVw
//#import "shdocvw.dll"
using namespace std;
class CMyDialog : public CAxDialogImpl<CMyDialog>
{
public:
enum { IDD = IDD_DIALOG1 };
BEGIN_MSG_MAP(CMyDialog)
MESSAGE_HANDLER(WM_INITDIALOG, OnInitDialog)
COMMAND_HANDLER(IDCANCEL, BN_CLICKED, OnBnCancel)
COMMAND_HANDLER(IDOK, BN_CLICKED, OnBnOk)
END_MSG_MAP()
CComPtr<IWebBrowser2> ctrl;
LRESULT OnInitDialog(UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL& bHandled)
{
// Do some initialization code
HRESULT hr;
//IDC_EXPLORER_TEST is the ID of your control
GetDlgControl(IDC_EXPLORER_TEST, __uuidof(ctrl), (void**)&ctrl);
VARIANT address;
address.vt = VT_BSTR;
address.bstrVal = SysAllocString(L"google.com");
VARIANT empty;
empty.vt = VT_EMPTY;
hr = ctrl->Navigate2(&address, &empty, &empty, &empty, &empty);
SysFreeString(address.bstrVal);
/*
Also fails
_variant_t a = SysAllocString(L"google.com");
VARIANT f;
f.vt = VT_I2;
f.iVal = navBrowserBar;
_variant_t fr = SysAllocString(L"_self");
_variant_t h = SysAllocString(L" ");
hr = ctrl->Navigate2(&a, &f, &fr, &h, &h);
*/
LRESULT res = CAxDialogImpl<CMyDialog>::OnInitDialog(uMsg, wParam, lParam, bHandled);
return 0;
}
public:
LRESULT OnBnCancel(WORD /*wNotifyCode*/, WORD /*wID*/, HWND /*hWndCtl*/, BOOL& /*bHandled*/)
{
EndDialog(IDCANCEL);
return 0;
}
LRESULT OnBnOk(WORD /*wNotifyCode*/, WORD /*wID*/, HWND /*hWndCtl*/, BOOL& /*bHandled*/)
{
EndDialog(IDOK);
return 0;
}
};
CComModule _Module;
int WINAPI WinMain(HINSTANCE,HINSTANCE,LPSTR,int)
{
CMyDialog dlg;
dlg.DoModal();
return 0;
}
Returns an exception at method call because of 0x0 read violation.

Answer 1

It appears that you failed to check if GetDlgControl succeeded. When it fails, ctrl has an unspecified value and might be null.
Of course, that leaves the question why it would fail, but that's another issue.