#include <GDIPlus.au3>
Opt("GUIOnEventMode", 1)
Opt("MouseCoordMode", 2)
$width = 600
$height = $width
$w05 = $width / 2
$h05 = $height / 2
$180_div_pi = 180 / ACos(-1)
Local $mx = $w05, $my = $h05
$r = 100
$r2 = $r / 2
$angle = 0
$hGUI = GUICreate("GDI+ Trigonometrie by UEZ 2010", $width, $height)
GUISetState()

_GDIPlus_Startup()
$hGraphics = _GDIPlus_GraphicsCreateFromHWND($hGUI)
$hBitmap = _GDIPlus_BitmapCreateFromGraphics($width, $height, $hGraphics)
$hBuffer = _GDIPlus_ImageGetGraphicsContext($hBitmap)
_GDIPlus_GraphicsSetSmoothingMode($hBuffer, 2)
_GDIPlus_GraphicsClear($hBuffer, 0xFFF0F0F0)
$hPen1 = _GDIPlus_PenCreate(0xFF0000A0, 2)
$hPen2 = _GDIPlus_PenCreate(0xA0000000, 1)
$hBrush1 = _GDIPlus_BrushCreateSolid(0x8000A000)
$hBrush2 = _GDIPlus_BrushCreateSolid(0x80A00000)

GUISetOnEvent(-3,"_Exit")

While Sleep(30)
    _GDIPlus_GraphicsClear($hBuffer, 0xA0F0F0F0)
    _GDIPlus_GraphicsDrawLine($hBuffer, 0, $h05, $width, $h05, $hPen2)
    _GDIPlus_GraphicsDrawLine($hBuffer, $w05, 0, $w05, $height, $hPen2)

	_GDIPlus_GraphicsDrawString($hBuffer, "X", $width - 15, $h05)
	_GDIPlus_GraphicsDrawString($hBuffer, "Y", $w05 - 15, 0)
	_GDIPlus_GraphicsDrawString($hBuffer, "-X", 2, $h05)
	_GDIPlus_GraphicsDrawString($hBuffer, "-Y", $w05 - 20, $height - 17)

    $mpos = MouseGetPos()
    $mwx = $mpos[0] - $w05
    $mwy = $h05 - $mpos[1]
    $pd = Pixel_Distance($w05, $h05, $mpos[0], $mpos[1])
    If $pd > 50 And $pd < $w05 - 10 Then
        $angle = -ATan($mwy / $mwx) * $180_div_pi
        If $mwx < 0 Then
            $angle = -180 + $angle
        ElseIf $mwx >= 0 And $mwy < 0 Then
            $angle = -360 + $angle
        EndIf
        _GDIPlus_GraphicsDrawString($hBuffer, StringFormat("%.2f", Abs($angle)) & "°", $mpos[0], $h05)
        _GDIPlus_GraphicsFillPie($hBuffer, $w05 - $r2, $h05 - $r2, $r, $r, 0, $angle, $hBrush1)
;~         _GDIPlus_GraphicsFillPie($hBuffer, $w05 - $r2, $h05 - $r2, $r, $r, -180, $angle, $hBrush2)
        _GDIPlus_GraphicsDrawLine($hBuffer, $width - $mpos[0], $height - $mpos[1], $mpos[0], $mpos[1], $hPen1)
        $mx = $mpos[0]
        $my = $mpos[1]
    Else
        _GDIPlus_GraphicsDrawString($hBuffer, StringFormat("%.2f", Abs($angle)) & "°", $mx, $h05)
        _GDIPlus_GraphicsFillPie($hBuffer, $w05 - $r2, $h05 - $r2, $r, $r, 0, $angle, $hBrush1)
;~         _GDIPlus_GraphicsFillPie($hBuffer, $w05 - $r2, $h05 - $r2, $r, $r, -180, $angle, $hBrush2)
        _GDIPlus_GraphicsDrawLine($hBuffer, $width - $mx, $height - $my, $mx, $my, $hPen1)
    EndIf
    _GDIPlus_GraphicsDrawImage($hGraphics, $hBitmap, 0, 0)
WEnd

Func Pixel_Distance($x1, $y1, $x2, $y2) ;Pythagoras theorem
    Local $a, $b, $c
    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   ;==>Pixel_Distance

Func _Exit()
    _GDIPlus_BrushDispose($hBrush1)
    _GDIPlus_BrushDispose($hBrush2)
    _GDIPlus_PenDispose($hPen1)
    _GDIPlus_PenDispose($hPen2)
    _GDIPlus_BitmapDispose($hBitmap)
    _GDIPlus_GraphicsDispose($hBuffer)
    _GDIPlus_Shutdown()
    Exit
EndFunc