title: Why windows API ActivateKeyboardLayout blocked when using KLF_SETFORPROCESS flag?
body: <p>When I called activateKeyboardLayout in my program using the KLF_SETFORPROCESS, this function will be blocked , and do not return. 
  I want to know why this api be blocked , I found less document about this.</p>
  
  <p>Other tips:
  If I change the flag of activateKeyboardLayout  to KLF_ACTIVATE, it will return immediately。 I want to figure out why , Can someone help me?</p>