How to have memfun with two parameters

Question

I want to use this function "EnumWindows(EnumWindowsProc, NULL);". The EnumWindowsProc is a Callback function:

BOOL CALLBACK EnumWindowsProc(HWND hwnd, LPARAM lParam);

For this callback I want to use a member function of a class.

e.g:

Class MyClass
{
    BOOL CALLBACK My_EnumWindowsProc(HWND hwnd, LPARAM lParam);
    void          test();
};

So i want to bind the called Callback with my function !!!

I try this:

void MyClass::test()
{
    EnumWindowsProc ptrFunc = mem_fun(&MyClass::My_EnumWindowsProc);
    EnumWindows(ptrFunc, NULL);
}

It's doesn't work, "mem_fun" can take only one argument ! Is it possible to do that ? else do you know another solution ? (maybe a solution will be possible with Boost::bind)

Answer 1

You need to create an Adapter, such as:

#include <windows.h>
#include <iostream>
#include <string>
using namespace std;

class MyCallback
{
public:
    MyCallback() : count_(0) {};
    static BOOL CALLBACK CallbackAdapter(HWND, LPARAM);
    BOOL Callback(HWND);
    unsigned count_;
};

BOOL MyCallback::Callback(HWND wnd)
{
    char title[1025] = {};
    GetWindowText(wnd, title, sizeof(title)-1);
    cout << wnd << "= '" << title << "'" << endl;
    ++count_;
    return TRUE;
}

BOOL MyCallback::CallbackAdapter(HWND wnd, LPARAM lp)
{
    MyCallback* that = reinterpret_cast<MyCallback*>(lp);
    return that->Callback(wnd);
}

int main()
{
    MyCallback cb;
    EnumWindows(&MyCallback::CallbackAdapter, reinterpret_cast<LPARAM>(&cb));
    cout << "Windows Found: " << cb.count_;
    return 0;
}