Group: Painting and Drawing - Library: user32
BOOL PaintDesktop(
HDC hdc // handle to DC
);
DECLARE INTEGER PaintDesktop IN user32;
INTEGER hdc
hdc [in] Handle to the device context.
If the function succeeds, the return value is nonzero.
You may call this function from within the Paint event of a form and see what happens to form's native controls, which controls are windowless by definition.