Help with _WinAPI_Draw

#include <GUIConstantsEx.au3>
#include <WindowsConstants.au3>
#include <WinAPI.au3>

Local $hDC, $hPen, $obj_orig

$Form1_1 = GUICreate("Form1", 201, 126, -1, -1)
$Input1 = GUICtrlCreateInput("20", 16, 24, 121, 21)
$Input2 = GUICtrlCreateInput("20", 16, 64, 121, 21)
$Button1 = GUICtrlCreateButton("1", 144, 24, 43, 25)
$Button2 = GUICtrlCreateButton("2", 146, 65, 43, 25)
GUISetState(@SW_SHOW)

$tRECT_X = DllStructCreate($tagRect)
DllStructSetData($tRECT_X, "Left", @DesktopWidth / 2)
DllStructSetData($tRECT_X, "Top", 25)
DllStructSetData($tRECT_X, "Right", 55)
DllStructSetData($tRECT_X, "Bottom", 40)

$tRECT_Y = DllStructCreate($tagRect)
DllStructSetData($tRECT_Y, "Left", 20)
DllStructSetData($tRECT_Y, "Top", @DesktopHeight / 4)
DllStructSetData($tRECT_Y, "Right", 55)
DllStructSetData($tRECT_Y, "Bottom", @DesktopHeight / 3)

$hDC = _WinAPI_GetWindowDC(0) ; DC of entire screen (desktop)
$hPen = _WinAPI_CreatePen($PS_SOLID, 3, 0x0000FF)
$obj_orig = _WinAPI_SelectObject($hDC, $hPen)

_WinAPI_DrawLine($hDC, 20, 20, 20, @DesktopHeight / 3)
_WinAPI_DrawLine($hDC, 20, 20, @DesktopWidth / 3, 20)
_WinAPI_SetBkMode($hDC, $TRANSPARENT)
_WinAPI_SetTextColor($hDC, 0x0000FF)
_WinAPI_DrawText($hDC, "X", $tRECT_X, $DT_CENTER)
_WinAPI_DrawText($hDC, "Y", $tRECT_Y, $DT_CENTER)

While 1
    $nMsg = GUIGetMsg()
    Switch $nMsg
        Case $GUI_EVENT_CLOSE
            ; refresh desktop
            _WinAPI_RedrawWindow(_WinAPI_GetDesktopWindow(), 0, 0, $RDW_INVALIDATE + $RDW_ALLCHILDREN)
            ; clear resources
            _WinAPI_SelectObject($hDC, $obj_orig)
            _WinAPI_DeleteObject($hPen)
            _WinAPI_ReleaseDC(0, $hDC)
            Exit
        Case $Button1
    EndSwitch
WEnd