msgs12.hlp (Topic list)
Focus and activation messages (1.2)
Message Groups  Overview                          Up Next Previous
────────────────────────────────────────────────────────────────────────────
WM_ACTIVATE         Indicates a change in activation state
WM_FOCUSCHANGE      Indicates that the focus window is changing
WM_QUERYFOCUSCHAIN  Queries the focus chain
WM_SETFOCUS         Indicates a change of focus
WM_SETSELECTION     Indicates whether a window is selected/deselected