Problem with function and winapi

[exevan]

Hello, so i use this function:

Func Pixel_Distance($x1, $y1, $x2, $y2)
    If $x2 = $x1 And $y2 = $y1 Then
        Return 0
    Else
        $a = $y2 - $y1
        $b = $x2 - $x1
        $c = Sqrt($a * $a + $b * $b)
        Return $c
    EndIf
EndFunc

Func DrawLine($start_x, $start_y, $end_x, $end_y, $color)
    Global $hDC, $hPen, $obj_orig
    $hDC = _WinAPI_GetWindowDC(0)
    $hPen = _WinAPI_CreatePen($PS_SOLID, 1, $color)
    $obj_orig = _WinAPI_SelectObject($hDC, $hPen)
    _WinAPI_DrawLine($hDC, $start_x, $start_y, $end_x, $end_y)
    _WinAPI_RedrawWindow(_WinAPI_GetDesktopWindow(), 0, 0, $RDW_INVALIDATE + $RDW_ALLCHILDREN)
EndFunc

Func _Test()
    while 1
        Local $FirstFile = PixelSearch(389, 76,1540, 870,0xF6F2D9)
        Local $SecondFile = PixelSearch(389, 76,1540, 870,0xDA7714)
        if not @error then

            Pixel_Distance($FirstFile[0], $FirstFile[1], $SecondFile[0],$SecondFile[1])
            DrawLine($FirstFile[0], $FirstFile[1], $SecondFile[0],$SecondFile[1], 0x00)
            _WinAPI_SelectObject($hDC, $obj_orig)
            _WinAPI_DeleteObject($hPen)
            _WinAPI_ReleaseDC(0, $hDC)  
            ToolTip("Distance: "&$c,0,0)
            sleep(1000)
        else
            ContinueLoop
        endif
    wend
EndFunc 

After 15 or 20 seconds i've got a error:

Pixel_Distance($FirstFile[0],...)
               $FirstFile ^ ERROR
Error: Subscrit used on non accesible variable

What's wrong?

And next question is about WinApi

My function draw a line on desktop every one second. How can i delete last line before a new line is draw?

Edited May 3, 2014 by exevan

[JohnOne]

1) Because PixelSearch fails

2) _WinAPI_RedrawWindow

[exevan]

So what i must do when the pixelsearch is failed? i try this:

Func _Test()
    while 1
        Local $FirstFile = PixelSearch(389, 76,1540, 870,0xF6F2D9)
        Local $SecondFile = PixelSearch(389, 76,1540, 870,0xDA7714)
        if not @error then

            Pixel_Distance($FirstFile[0], $FirstFile[1], $SecondFile[0],$SecondFile[1])
            DrawLine($FirstFile[0], $FirstFile[1], $SecondFile[0],$SecondFile[1], 0x00)
            _WinAPI_SelectObject($hDC, $obj_orig)
            _WinAPI_DeleteObject($hPen)
            _WinAPI_ReleaseDC(0, $hDC)  
            ToolTip("Distance: "&$c,0,0)
            sleep(1000)
        else
            _Test()
        endif
    wend
EndFunc

but doesn't work;/

[JohnOne]

This 

if not @error then

Needs to changed to test that both $firstfile and $secondfile are arrays (IsArray() function).

You can leave continueloop and get shut of recursive _Test()

[exevan]

Thanks  Now with this clean previous draw line ;/

Edited May 3, 2014 by exevan