WM_MDIACTIVATE

An application sends the WM_MDIACTIVATE message to a multiple document interface (MDI) client window to instruct the client window to activate a different MDI child window. As the client window processes this message, it sends WM_MDIACTIVATE to the child window being deactivated and to the child window being activated.

WM_MDIACTIVATE 
// Message sent to MDI client 
wParam = (WPARAM) (HWND) hwndChildAct; // child to activate 
lParam = 0;                            // not used; must be zero 
 
// Message received by MDI child 
hwndChildDeact = (HWND) wParam;        // child being deactivated 
hwndChildAct = (HWND) lParam;          // child being activated 
 

Parameters

In messages sent to an MDI client window:

hwndChildAct

Value of wParam. Handle to the MDI child window to be activated.

In messages received by an MDI child window:

hwndChildDeact

Value of wParam. Handle to the MDI child window being deactivated.

hwndChildAct

Value of lParam. Handle to the MDI child window being activated.

Return Values

If an application sends this message to an MDI client window, the return value is zero. An MDI child window should return zero if it processes this message.

Remarks

An MDI child window is activated independently of the MDI frame window. When the frame window becomes active, the child window last activated by using the WM_MDIACTIVATE message receives the WM_NCACTIVATE message to draw an active window frame and title bar; the child window does not receive another WM_MDIACTIVATE message.

QuickInfo

  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Unsupported.
  Header: Declared in winuser.h.

See Also

Multiple Document Interface Overview, Multiple Document Interface Messages, WM_MDIGETACTIVE, WM_MDINEXT, WM_NCACTIVATE