The WM_ENTERSIZEMOVE message is sent once to a window when it enters the moving or sizing mode. The window enters the moving or sizing mode when the user clicks the window’s title bar or sizing border, or when the window passes the WM_SYSCOMMAND message to the DefWindowProc function and the wParam parameter of the message specifies the SC_MOVE or SC_SIZE value. Windows sends the WM_ENTERSIZEMOVE message regardless of whether the dragging of full windows is enabled.
WM_ENTERSIZEMOVE wParam = 0; // not used, must be zero lParam = 0; // not used, must be zero
This message has no parameters.
An application should return zero if it processes this message.