Msdn:
Zitat:
rdw_frame
causes any part of the nonclient area of the window that intersects the update region to receive a wm_ncpaint message. The rdw_invalidate flag must also be specified; otherwise, rdw_frame has no effect. The wm_ncpaint message is typically not sent during the execution of redrawwindow unless either rdw_updatenow or rdw_erasenow is specified.