Question

I have a std::map of windows, for example:

class MyWindow
{
public:
    MyWindow()
    {
        CreateWindow(...);
    }
    ... // rest of code
}

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
        // code
    }
}

std::map<string, MyWindow> windows;

And inside the WndProc function I want to know which window is now in the function, how can I get the key of this window.

Answer 1

You could use SetWindowLongPtr to store a pointer to an object (this if you’re creating a window in a class method) for a given HWND. Use GWLP_USERDATA as nIndex argument.

This way, you need no map at all: when you have a window handle, GetWindowLongPtr is enough to get an object.