GetPostion() bug with position of -1?

[7stud]

The following program allows the user to move a frame around with key presses.
The frame moves one unit in any direction depending on what arrow key is
pressed.  However, when I use SetPosition() to set the x or y position of the
frame to -1, subsequently GetPosition() reports the position as 0, which 
prevents the key presses from moving the frame into a location with negative
coordinates.  However, if  I move the frame's x or y coordinate to -2, then 
GetPostion() reports the correct coordinates, and allows the frame to move to
locations with negative coordinates.


import wx

class MyFrame(wx.Frame):

    def __init__(self, parent=None, id=-1): 
        wx.Frame.__init__(self, parent, id)
        self.Bind(wx.EVT_KEY_DOWN, self.OnKeyDown)

    def OnKeyDown(self, event): 
        key = event.GetKeyCode()
        origin = self.GetPosition()
        print origin
        
        if key == 314: #left
            print origin.x - 1
            self.SetPosition((origin.x-1, origin.y))
         
        elif key == 316: #right
            self.SetPosition((origin.x+1, origin.y))
         
        elif key == 315: #up
            print origin.y - 1
            self.SetPosition((origin.x, origin.y-1))
         
        elif key == 317: # down
            self.SetPosition((origin.x, origin.y+1))
        print key
         
app = wx.App(redirect=False)

frame = MyFrame()
frame.Show()

app.MainLoop()


Is that a bug in GetPosition()?