This function sends a WM_FOCUSCHANGE message to the window that is losing the focus and a WM_FOCUSCHANGE message to the window that is receiving the focus.

This function fails if another process or thread is currently using this function.

Other messages may be sent as a consequence of the frame control processing of the WM_FOCUSCHANGE (in Frame Controls) message, depending on the value of the flFocusChange parameter. These messages, if sent, are sent in this order:

• WM_SETFOCUS to the window losing the focus.
  
• WM_SETSELECTION to the windows losing their selection.
  
• WM_ACTIVATE to the windows being deactivated.
  
• WM_ACTIVATE to the windows being activated.
  
• WM_SETSELECTION to the windows being selected.
  
• WM_SETFOCUS to the window receiving the focus.

Note: If the WinQueryFocus function is used during processing of this function:

• The window handle of the window losing the focus is returned while the WM_FOCUSCHANGE message with the is being processed.

• The window handle of the window receiving the focus is returned while the WM_FOCUSCHANGE (in Frame Controls) message with the is being processed.

If the WinQueryActiveWindow function is used during processing of this function:

• The window handle of the window being deactivated is returned while the WM_ACTIVATE message with the is being processed.

• The window handle of the window being activated is returned while the WM_ACTIVATE message with the is being processed.

Also, there is a short period during the time after the old active window has acted on the deactivation message and before the new active window has acted on the activation message when the WinQueryActiveWindow function returns NULLHANDLE.

This function should not be made unless it is directly or indirectly the result of operator input.

Even if FC_NOSETSELECTION is not specified, the WM_SETSELECTION is not sent to a frame window that is already selected. This can occur if the focus is being transferred from a parent to a child window and FC_NOLOSESELECTION was specified.