https://social.msdn.microsoft.com/Forums/vstudio/en-US/b6c4cacc-e465-4adc-9faa-1211bd957395/layered-window-cant-process-wmmove-msg-correctly?forum=vcgeneral
Sending a series of WM_MOVE is probably associated with the “Show window contents while dragging” system option, which can be found in the Performance Options dialog …