WS_CLIPCHILDREN does not work when in fullscreen

I have a main window created with :

if (!fullscreen)
{
    wStyle = WS_OVERLAPPED | WS_BORDER | WS_CAPTION | WS_SYSMENU | WS_MINIMIZEBOX | WS_CLIPCHILDREN;
    wExStyle = WS_EX_TOPMOST;
}
else
{
    wStyle = WS_OVERLA开发者_如何学JAVAPPEDWINDOW | WS_CLIPCHILDREN;
    wExStyle = WS_EX_TOPMOST;
}

I have also a child window created runtime with :

wStyle = WS_VISIBLE | WS_POPUP | WS_CHILD;
wExStyle = WS_EX_TOPMOST;

Everything is going well when I am not in fullscreen. (i.e. The child window is well displayed on top of the parent window.)

But, when I am on fullscreen mode, the parent window is painted over the child window which cause an awful flickering.

How to set properties to the main and the child window in order to display well the child window, even in fullscreen mode ?

Thanks in advance for all your answers.

WS_POPUP cannot be used with WS_CHILD. Not positive that's the cause though.

Those style flag combinations are invalid. A child window cannot be a popup nor can it be top-most. No idea what kind of side effects that might have, never tried to get this wrong intentionally.

Getting stuck on this might be educational but not very practical. Have you considered using a class library to take care of the gooey stuff?