Problem with switching application and focus

Sorry but my english is very bad.

I am writing a winapi program in c and I have a problem. The program has a main window and NO DIALOG chil开发者_运维问答d windows (controls). The controls are directly attached to the main window. When I switch the application to another application and back again, the focus is set to the main window and not to the control that owns the focus before switching.

My message loop is:

while ((rGetMessage = GetMessage(&msg, NULL, 0, 0)) != 0 && rGetMessage != -1)
{
    if(!IsDialogMessage(hwnd_principal, &msg))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
}

What is my error?

I use the IsDialogMessage function for that various keys work on (like TAB key in the controls).

When you switch back to your application, Windows will by default set the keyboard focus to its main window, regardless of which window had the focus when it was deactivated. If you want to do something different you need to handle WM_ACTIVATE and use SetFocus() to restore the focus to the control.