Function track

Windows doesn't natively support mouse crossing events. TrackMouseEvent() (and its comctl32.dll wrapper _TrackMouseEvent()) both allow for a window to receive the WM_MOUSELEAVE message when the mouse leaves the client area. There's no equivalent WM_MOUSEENTER because it can be simulated (https://blogs.msdn.microsoft.com/oldnewthing/20031013-00/?p=42193). Unfortunately, WM_MOUSELEAVE does not get