Crash during WM_NCCREATE

[Eirik]

Hi,

I'm trying to write an custom control and I'm experiencing some problems. I have a class Button, derived from a CustomControl class. In my button class I have defined message router function for passing the messages to my message handler class member function. The thing here is I want to use a window message processer for each instance of the control that is created. (Is this a stupid way of doing things? I mean, I could have passed in a pointer to the class instance in each message handler, but then the code would be sprinkled with pointer->class_member all over).

The problem is my code crashes during WM_NCCREATE. If i return TRUE from RoutMsg() the progam seems to crash at that very moment. If i leave it out, it crashes when calling DefWindowProc() in Button::ButtonProc().

I am a bit puzzeled as to why this happens. Can someone shed some light on this?

Here's my message router function:

static LRESULT CALLBACK RouteMsg(HWND hwnd, UINT msg, WPARAM w, LPARAM l)
{
    Button *btn = reinterpret_cast<Button *>(::GetWindowLongPtr(hwnd, GWL_USERDATA));

    if(msg = WM_NCCREATE)
    {
        CREATESTRUCT *pcs = reinterpret_cast<CREATESTRUCT *>(l);
        btn = reinterpret_cast<Button *>(pcs->lpCreateParams);
        ::SetWindowLongPtr(hwnd, GWL_USERDATA, reinterpret_cast<LONG_PTR>(btn));

        btn->m_handle = hwnd;

        //return TRUE; //If I uncomment this line the program crashes here
    }

    if(btn)
        return btn->ButtonProc(hwnd,msg,w,l);
    else
        return DefWindowProc(hwnd,msg,w,l);
}

LRESULT Button::ButtonProc(HWND hwnd, UINT msg, WPARAM w, LPARAM l)
{
    switch(msg)
    {
        default:
            return DefWindowProc(hwnd,msg,w,l);
    }
}

[Salem]

> if(msg = WM_NCCREATE)
Why is this not == ?

[Eirik]

Haha! I don't believe this! Thanks for pointing that out! I guess that's the way it is when I'm using multiple programming languages with different syntaxes. It gets confusing.. It also was very late last night

Anyway, thanks! Changing to == of course sorted out the problem.