gdi+ and ellipse

[oMBRa 1]

this is my script:

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#include <GDIPlus.au3>
#include <WindowsConstants.au3>

Opt("GuiOnEventMode", 1)
$size = 500
$hwnd = GUICreate("Test", $size, $size, -1, -1)
GUISetState()
GUISetOnEvent(-3, "close")
_GDIPlus_Startup()
$graphics = _GDIPlus_GraphicsCreateFromHWND($hwnd)
_GDIPlus_GraphicsClear($graphics)
$bitmap = _GDIPlus_BitmapCreateFromGraphics($size, $size, $graphics)
$backbuffer = _GDIPlus_ImageGetGraphicsContext($bitmap)
$pen = _GDIPlus_PenCreate(0xFF00FF00, 2)

_AntiAlias($backbuffer, 4)

Global $AsseMa = 200    ;bigger axis of the ellipse
Global $AsseMi = 140    ;shorter axis of the ellipse

Global $SAsseMa = $AsseMa / 2
Global $SAsseMi = $AsseMi / 2
Global $BaseX = $size / 2 - $SAsseMa
Global $BaseY = $size / 2 - $SAsseMi
Global $pi = 3.14159265358979
Global $F1 = Sqrt($SAsseMa ^ 2 - $SAsseMi ^ 2)
Global $F2 = -$F1
Global $a = Sqrt($F1 ^ 2 + $SAsseMi ^ 2)
Global $x = -$SAsseMa
Global $y = 0
Global $iFX = 10
Global $iFY = 1

Do

    _GDIPlus_GraphicsClear($backbuffer, 0xFF000000)
    _GDIPlus_GraphicsDrawEllipse($backbuffer, $BaseX, $BaseY, $SAsseMa * 2, $SAsseMi * 2, $pen)
    _GDIPlus_GraphicsDrawEllipse($backbuffer, $BaseX + $SAsseMa + $x, $BaseY + $SAsseMi + $y, 10, 10, $pen)
;~  _GDIPlus_GraphicsDrawEllipse($backbuffer, $BaseX + $SAsseMa + $F1, $BaseY + $SAsseMi, 1, 1, $pen)
;~  _GDIPlus_GraphicsDrawEllipse($backbuffer, $BaseX + $SAsseMa + $F2, $BaseY + $SAsseMi, 1, 1, $pen)
    _GDIPlus_GraphicsDrawImageRect($graphics, $bitmap, 0, 0, $size, $size)
;~  MsgBox(0, '', $y&@CRLF&$X&@CR&$iFX)
        $x = $x + $iFX
    If $x >= $SAsseMa Then
        $iFX = -10
        $iFY = -1
    ElseIf $x <= -$SAsseMa Then
        $iFX = 10
        $iFY = 1
    EndIf
    $y = Sqrt((1 - (-$x ^ 2) / ($SAsseMa ^ 2)) * $SAsseMi ^ 2) * $iFY
    Sleep(10)
Until 0


Func close()
    _GDIPlus_GraphicsDispose($graphics)
    _WinAPI_DeleteObject($bitmap)
    _GDIPlus_PenDispose($pen)

    _GDIPlus_Shutdown()
    Exit
EndFunc ;==>close

Func _AntiAlias($hGraphics, $mode)
    Local $aResult
    $aResult = DllCall($ghGDIPDll, "int", "GdipSetSmoothingMode", "hwnd", $hGraphics, "int", $mode)
    If @error Then Return SetError(@error, @extended, False)
    Return SetError($aResult[0], 0, $aResult[0] = 0)
EndFunc ;==>_AntiAlias

the ''ball'' increases the speed when it reaches the end of the ellipse (and the beginning)...

how to solve this problem?

Edited April 12, 2009 by oMBra