Question

I’m wondering what the correct return value for a windows message loop is. So far I’ve used the following:

case WM_LBUTTONDOWN: // left mouse button pressed.
    if (condition == true )
    {
        do_something();
    }
break;

but I’ve seen also things like:

if (IDC_BUTTON == LOWORD(wParam) && BN_CLICKED == HIWORD(wParam))
{
    do_something();
    return true;
}
break;

which one is correct? Should I return true? or should I break? Does it matter?

EDIT does it depend whether I’m interacting with a button press or a mouse movement?

Answer 1

The return value is documented on MSDN, as part of the documentation for each message. For example, the documentation for WM_LBUTTONDOWN states that

If an application processes this message, it should return zero.

For other messages, the return value might be more meaningful. You should always read the documentation, never guess.