#include <WinAPI.au3>

$tRect = DllStructCreate($tagRECT)
DllStructSetData($tRect, "Left", 0)
DllStructSetData($tRect, "Top", 0)
DllStructSetData($tRect, "Right", 0)
DllStructSetData($tRect, "Bottom", 0)
MsgBox(4096, 'RectIsEmpty', _WinAPI_RectIsEmpty($tRect))