#include <WinAPI.au3>

_Main()

Func _Main()
	Local $hwnd, $tRect
	$hwnd = GUICreate("Тест")
	GUISetState()
	$tRect = _WinAPI_GetClientRect($hwnd)
	MsgBox(262144, "Прямоугольник", _
			"Левая.....: " & DllStructGetData($tRect, "Left") & @LF & _
			"Правая..: " & DllStructGetData($tRect, "Right") & @LF & _
			"Верхняя: " & DllStructGetData($tRect, "Top") & @LF & _
			"Нижняя: " & DllStructGetData($tRect, "Bottom"))
EndFunc   ;==>_Main