An application sends the WM_MDIGETACTIVE message to a multiple document interface (MDI) client window to retrieve the handle of the active MDI child window.
WM_MDIGETACTIVE
wParam = 0; // not used; must be zero
lParam = (LPBOOL) lpfMaximized; // optional pointer to maximized state flag
Parameters
lpfMaximized
Value of lparam. This is an optional pointer to a maximized state flag variable. If lpfMaximized is non-NULL, the BOOL it points to is set to indicate the maximized state of the MDI child window. TRUE indicates that the window is maximized, FALSE indicates that it is not. This is equivalent to the indication supplied by the high-order word of the return value of the WM_MDIGETACTIVE message under Windows version 3.x. If lpfMaximized is NULL, the parameter is ignored.
Return Values
The return value is the handle of the active MDI child window.
Remarks
Note carefully a change in how this message indicates maximization. In Windows version 3.x, the message return value includes a flag indicating whether the MDI child window is maximized. In the Win32 application programming interface (API), the return value does not include this flag. In Win32, the MDI child window's maximized state is indicated by setting a BOOL variable via the optional parameter in lParam, lpfMaximized.