An application sends the WM_MDINEXT message to a multiple document interface (MDI) client window to activate the next or previous child window.
WM_MDINEXT
wParam = (WPARAM) (HWND) hwndChild; // handle to child
lParam = (LPARAM) fNext; // next or previous child
The return value is always zero.
If an MDI client window receives any message that changes the activation of its child windows while the active MDI child window is maximized, the system restores the active child window and maximizes the newly activated child window.
Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Unsupported.
Header: Declared in winuser.h.
Multiple Document Interface Overview, Multiple Document Interface Messages, WM_MDIACTIVATE, WM_MDIGETACTIVE