Question

I want to know the value of virtual key pressed when a child window(like ‘edit’ or ‘button’) has focus.
How to do that?

Answer 1

Well one way is to use

WNDPROC g_OldProc;

LRESULT CALLBACK MyEditWindowProc( HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam )
{
    if ( uMsg == WM_KEYDOWN )
    {
         // Handle key down.
    }
    return g_OldProc( hwnd, uMsg, wParam, lParam );
}

then at some opportune moment

g_OldProc = (WNDPROC)GetWindowLongPtr( hEdit, GWLP_WNDPROC );
SetWindowLongPtr( hEdit, GWLP_WNDPROC, (LONG_PTR)MyEditWindowProc );

This will replace the window procedure of the hEdit control with your own window procedure that, in turn, calls the original window procedure.