Get the title of the window under mouse

#include <WinAPI.au3>

HotKeySet("{ESC}", "_Exit")

Local $tPoint = DllStructCreate($tagPOINT)

Local $hWnd

While 1
    ToolTip("")
    DllStructSetData($tPoint, "x", MouseGetPos(0))
    DllStructSetData($tPoint, "y", MouseGetPos(1))

    $hWnd = _GetParent(_WinAPI_WindowFromPoint($tPoint))
    ToolTip(WinGetTitle($hWnd))
    Sleep(100)
WEnd

Func _GetParent($hWnd)
    Local $hParent = $hWnd
    While 1
        Local $hCurrent = _WinAPI_GetParent($hParent)
        If IsHWnd($hCurrent) Then
            $hParent = $hCurrent
        Else
            ExitLoop
        EndIf
    WEnd
    Return $hParent
EndFunc   ;==>_GetParent

Func _Exit()
    Exit
EndFunc   ;==>_Exit