The WM_WINDOWPOSCHANGED message is sent to a window whose size, position, or place in the Z order has changed as a result of a call to the SetWindowPos function or another window-management function.
WM_WINDOWPOSCHANGED
lpwp = (LPWINDOWPOS) lParam; // points to size and position data
If an application processes this message, it should return zero.
The DefWindowProc function sends the WM_SIZE and WM_MOVE messages to the window.
The WM_SIZE and WM_MOVE messages are not sent if an application handles the WM_WINDOWPOSCHANGED message without calling DefWindowProc. It is more efficient to perform any move or size change processing during the WM_WINDOWPOSCHANGED message without calling DefWindowProc.
Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Requires version 1.0 or later.
Header: Declared in winuser.h.
Windows Overview, Window Messages, DefWindowProc, EndDeferWindowPos, SetWindowPos, WINDOWPOS, WM_MOVE, WM_SIZE, WM_WINDOWPOSCHANGING