WM_CANCELMODEThe WM_CANCELMODE message is sent to inform a window to cancel any internal mode. This message is sent to the focus window when a dialog box or message box is displayed, giving the focus window the opportunity to cancel modes such as mouse capture.
This message has no parameters.
An application should return zero if it processes this message.
The DefWindowProc function processes this message by calling the ReleaseCapture function. DefWindowProc does not cancel any other modes.