title: CDockablePane as a tabbed document does not send WM_SETFOCUS or WM_MDIACTIVATE
body: <p>I have a class derived from CDockablePane. I need to do something when the view is focused, so I handle WM_SETFOCUS and it all works nicely most of the time.</p>
  
  <p>But when the pane is docked in Tabbed Document mode (TDI), and the user activates it, the WM_SETFOCUS is not called.</p>
  
  <p>I used Spy and noticed the WM_MDIACTIVATE message is sent to the pane's parent window.</p>
  
  <p>However if I handle WM_MDIACTIVATE inside the pane or inside the mainframe, it does not get called either.</p>
  
  <p>Any ideas what I need to handle?</p>