Bug #3884: Make the turtle module toplevel again.

1 files changed, 0 insertions, 4051 deletions

diff --git a/Lib/tkinter/turtle.py b/Lib/tkinter/turtle.py
deleted file mode 100644
index 1497d2d..0000000
--- a/Lib/tkinter/turtle.py
+++ /dev/null
@@ -1,4051 +0,0 @@
-#
-# turtle.py: a Tkinter based turtle graphics module for Python
-# Version 1.0b1 - 31. 5. 2008
-#
-# Copyright (C) 2006 - 2008  Gregor Lingl
-# email: glingl@aon.at
-#
-# This software is provided 'as-is', without any express or implied
-# warranty.  In no event will the authors be held liable for any damages
-# arising from the use of this software.
-#
-# Permission is granted to anyone to use this software for any purpose,
-# including commercial applications, and to alter it and redistribute it
-# freely, subject to the following restrictions:
-#
-# 1. The origin of this software must not be misrepresented; you must not
-#    claim that you wrote the original software. If you use this software
-#    in a product, an acknowledgment in the product documentation would be
-#    appreciated but is not required.
-# 2. Altered source versions must be plainly marked as such, and must not be
-#    misrepresented as being the original software.
-# 3. This notice may not be removed or altered from any source distribution.
-
-
-"""
-Turtle graphics is a popular way for introducing programming to
-kids. It was part of the original Logo programming language developed
-by Wally Feurzig and Seymour Papert in 1966.
-
-Imagine a robotic turtle starting at (0, 0) in the x-y plane. Give it
-the command turtle.forward(15), and it moves (on-screen!) 15 pixels in
-the direction it is facing, drawing a line as it moves. Give it the
-command turtle.left(25), and it rotates in-place 25 degrees clockwise.
-
-By combining together these and similar commands, intricate shapes and
-pictures can easily be drawn.
-
------ turtle.py
-
-This module is an extended reimplementation of turtle.py from the
-Python standard distribution up to Python 2.5. (See: http:\\www.python.org)
-
-It tries to keep the merits of turtle.py and to be (nearly) 100%
-compatible with it. This means in the first place to enable the
-learning programmer to use all the commands, classes and methods
-interactively when using the module from within IDLE run with
-the -n switch.
-
-Roughly it has the following features added:
-
-- Better animation of the turtle movements, especially of turning the
-  turtle. So the turtles can more easily be used as a visual feedback
-  instrument by the (beginning) programmer.
-
-- Different turtle shapes, gif-images as turtle shapes, user defined
-  and user controllable turtle shapes, among them compound
-  (multicolored) shapes. Turtle shapes can be stgretched and tilted, which
-  makes turtles zu very versatile geometrical objects.
-
-- Fine control over turtle movement and screen updates via delay(),
-  and enhanced tracer() and speed() methods.
-
-- Aliases for the most commonly used commands, like fd for forward etc.,
-  following the early Logo traditions. This reduces the boring work of
-  typing long sequences of commands, which often occur in a natural way
-  when kids try to program fancy pictures on their first encounter with
-  turtle graphcis.
-
-- Turtles now have an undo()-method with configurable undo-buffer.
-
-- Some simple commands/methods for creating event driven programs
-  (mouse-, key-, timer-events). Especially useful for programming games.
-
-- A scrollable Canvas class. The default scrollable Canvas can be
-  extended interactively as needed while playing around with the turtle(s).
-
-- A TurtleScreen class with methods controlling background color or
-  background image, window and canvas size and other properties of the
-  TurtleScreen.
-
-- There is a method, setworldcoordinates(), to install a user defined
-  coordinate-system for the TurtleScreen.
-
-- The implementation uses a 2-vector class named Vec2D, derived from tuple.
-  This class is public, so it can be imported by the application programmer,
-  which makes certain types of computations very natural and compact.
-
-- Appearance of the TurtleScreen and the Turtles at startup/import can be
-  configured by means of a turtle.cfg configuration file.
-  The default configuration mimics the appearance of the old turtle module.
-
-- If configured appropriately the module reads in docstrings from a docstring
-  dictionary in some different language, supplied separately  and replaces
-  the english ones by those read in. There is a utility function
-  write_docstringdict() to write a dictionary with the original (english)
-  docstrings to disc, so it can serve as a template for translations.
-
-Behind the scenes there are some features included with possible
-extensionsin in mind. These will be commented and documented elsewhere.
-
-"""
-
-_ver = "turtle 1.0b1- - for Python 3.0   -  9. 6. 2008, 01:15"
-
-# print(_ver)
-
-import tkinter as TK
-import types
-import math
-import time
-import os
-
-from os.path import isfile, split, join
-from copy import deepcopy
-
-#from math import *    ## for compatibility with old turtle module
-
-_tg_classes = ['ScrolledCanvas', 'TurtleScreen', 'Screen',
-               'RawTurtle', 'Turtle', 'RawPen', 'Pen', 'Shape', 'Vec2D']
-_tg_screen_functions = ['addshape', 'bgcolor', 'bgpic', 'bye',
-        'clearscreen', 'colormode', 'delay', 'exitonclick', 'getcanvas',
-        'getshapes', 'listen', 'mode', 'onkey', 'onscreenclick', 'ontimer',
-        'register_shape', 'resetscreen', 'screensize', 'setup',
-        'setworldcoordinates', 'title', 'tracer', 'turtles', 'update',
-        'window_height', 'window_width']
-_tg_turtle_functions = ['back', 'backward', 'begin_fill', 'begin_poly', 'bk',
-        'circle', 'clear', 'clearstamp', 'clearstamps', 'clone', 'color',
-        'degrees', 'distance', 'dot', 'down', 'end_fill', 'end_poly', 'fd',
-        #'fill',
-        'fillcolor', 'forward', 'get_poly', 'getpen', 'getscreen',
-        'getturtle', 'goto', 'heading', 'hideturtle', 'home', 'ht', 'isdown',
-        'isvisible', 'left', 'lt', 'onclick', 'ondrag', 'onrelease', 'pd',
-        'pen', 'pencolor', 'pendown', 'pensize', 'penup', 'pos', 'position',
-        'pu', 'radians', 'right', 'reset', 'resizemode', 'rt',
-        'seth', 'setheading', 'setpos', 'setposition', 'settiltangle',
-        'setundobuffer', 'setx', 'sety', 'shape', 'shapesize', 'showturtle',
-        'speed', 'st', 'stamp', 'tilt', 'tiltangle', 'towards', #'tracer',
-        'turtlesize', 'undo', 'undobufferentries', 'up', 'width',
-        #'window_height', 'window_width',
-        'write', 'xcor', 'ycor']
-_tg_utilities = ['write_docstringdict', 'done', 'mainloop']
-##_math_functions = ['acos', 'asin', 'atan', 'atan2', 'ceil', 'cos', 'cosh',
-##        'e', 'exp', 'fabs', 'floor', 'fmod', 'frexp', 'hypot', 'ldexp', 'log',
-##        'log10', 'modf', 'pi', 'pow', 'sin', 'sinh', 'sqrt', 'tan', 'tanh']
-
-__all__ = (_tg_classes + _tg_screen_functions + _tg_turtle_functions +
-           _tg_utilities) # + _math_functions)
-
-_alias_list = ['addshape', 'backward', 'bk', 'fd', 'ht', 'lt', 'pd', 'pos',
-               'pu', 'rt', 'seth', 'setpos', 'setposition', 'st',
-               'turtlesize', 'up', 'width']
-
-_CFG = {"width" : 0.5,               # Screen
-        "height" : 0.75,
-        "canvwidth" : 400,
-        "canvheight": 300,
-        "leftright": None,
-        "topbottom": None,
-        "mode": "standard",          # TurtleScreen
-        "colormode": 1.0,
-        "delay": 10,
-        "undobuffersize": 1000,      # RawTurtle
-        "shape": "classic",
-        "pencolor" : "black",
-        "fillcolor" : "black",
-        "resizemode" : "noresize",
-        "visible" : True,
-        "language": "english",        # docstrings
-        "exampleturtle": "turtle",
-        "examplescreen": "screen",
-        "title": "Python Turtle Graphics",
-        "using_IDLE": False
-       }
-
-##print "cwd:", os.getcwd()
-##print "__file__:", __file__
-##
-##def show(dictionary):
-##    print "=========================="
-##    for key in sorted(dictionary.keys()):
-##        print key, ":", dictionary[key]
-##    print "=========================="
-##    print
-
-def config_dict(filename):
-    """Convert content of config-file into dictionary."""
-    f = open(filename, "r")
-    cfglines = f.readlines()
-    f.close()
-    cfgdict = {}
-    for line in cfglines:
-        line = line.strip()
-        if not line or line.startswith("#"):
-            continue
-        try:
-            key, value = line.split("=")
-        except:
-            print("Bad line in config-file %s:\n%s" % (filename,line))
-            continue
-        key = key.strip()
-        value = value.strip()
-        if value in ["True", "False", "None", "''", '""']:
-            value = eval(value)
-        else:
-            try:
-                if "." in value:
-                    value = float(value)
-                else:
-                    value = int(value)
-            except:
-                pass # value need not be converted
-        cfgdict[key] = value
-    return cfgdict
-
-def readconfig(cfgdict):
-    """Read config-files, change configuration-dict accordingly.
-
-    If there is a turtle.cfg file in the current working directory,
-    read it from there. If this contains an importconfig-value,
-    say 'myway', construct filename turtle_mayway.cfg else use
-    turtle.cfg and read it from the import-directory, where
-    turtle.py is located.
-    Update configuration dictionary first according to config-file,
-    in the import directory, then according to config-file in the
-    current working directory.
-    If no config-file is found, the default configuration is used.
-    """
-    default_cfg = "turtle.cfg"
-    cfgdict1 = {}
-    cfgdict2 = {}
-    if isfile(default_cfg):
-        cfgdict1 = config_dict(default_cfg)
-        #print "1. Loading config-file %s from: %s" % (default_cfg, os.getcwd())
-    if "importconfig" in cfgdict1:
-        default_cfg = "turtle_%s.cfg" % cfgdict1["importconfig"]
-    try:
-        head, tail = split(__file__)
-        cfg_file2 = join(head, default_cfg)
-    except:
-        cfg_file2 = ""
-    if isfile(cfg_file2):
-        #print "2. Loading config-file %s:" % cfg_file2
-        cfgdict2 = config_dict(cfg_file2)
-##    show(_CFG)
-##    show(cfgdict2)
-    _CFG.update(cfgdict2)
-##    show(_CFG)
-##    show(cfgdict1)
-    _CFG.update(cfgdict1)
-##    show(_CFG)
-
-try:
-    readconfig(_CFG)
-except:
-    print ("No configfile read, reason unknown")
-
-
-class Vec2D(tuple):
-    """A 2 dimensional vector class, used as a helper class
-    for implementing turtle graphics.
-    May be useful for turtle graphics programs also.
-    Derived from tuple, so a vector is a tuple!
-
-    Provides (for a, b vectors, k number):
-       a+b vector addition
-       a-b vector subtraction
-       a*b inner product
-       k*a and a*k multiplication with scalar
-       |a| absolute value of a
-       a.rotate(angle) rotation
-    """
-    def __new__(cls, x, y):
-        return tuple.__new__(cls, (x, y))
-    def __add__(self, other):
-        return Vec2D(self[0]+other[0], self[1]+other[1])
-    def __mul__(self, other):
-        if isinstance(other, Vec2D):
-            return self[0]*other[0]+self[1]*other[1]
-        return Vec2D(self[0]*other, self[1]*other)
-    def __rmul__(self, other):
-        if isinstance(other, int) or isinstance(other, float):
-            return Vec2D(self[0]*other, self[1]*other)
-    def __sub__(self, other):
-        return Vec2D(self[0]-other[0], self[1]-other[1])
-    def __neg__(self):
-        return Vec2D(-self[0], -self[1])
-    def __abs__(self):
-        return (self[0]**2 + self[1]**2)**0.5
-    def rotate(self, angle):
-        """rotate self counterclockwise by angle
-        """
-        perp = Vec2D(-self[1], self[0])
-        angle = angle * math.pi / 180.0
-        c, s = math.cos(angle), math.sin(angle)
-        return Vec2D(self[0]*c+perp[0]*s, self[1]*c+perp[1]*s)
-    def __getnewargs__(self):
-        return (self[0], self[1])
-    def __repr__(self):
-        return "(%.2f,%.2f)" % self
-
-
-##############################################################################
-### From here up to line    : Tkinter - Interface for turtle.py            ###
-### May be replaced by an interface to some different graphcis-toolkit     ###
-##############################################################################
-
-## helper functions for Scrolled Canvas, to forward Canvas-methods
-## to ScrolledCanvas class
-
-def __methodDict(cls, _dict):
-    """helper function for Scrolled Canvas"""
-    baseList = list(cls.__bases__)
-    baseList.reverse()
-    for _super in baseList:
-        __methodDict(_super, _dict)
-    for key, value in cls.__dict__.items():
-        if type(value) == types.FunctionType:
-            _dict[key] = value
-
-def __methods(cls):
-    """helper function for Scrolled Canvas"""
-    _dict = {}
-    __methodDict(cls, _dict)
-    return _dict.keys()
-
-__stringBody = (
-    'def %(method)s(self, *args, **kw): return ' +
-    'self.%(attribute)s.%(method)s(*args, **kw)')
-
-def __forwardmethods(fromClass, toClass, toPart, exclude = ()):
-    ### MANY CHANGES ###
-    _dict_1 = {}
-    __methodDict(toClass, _dict_1)
-    _dict = {}
-    mfc = __methods(fromClass)
-    for ex in _dict_1.keys():
-        if ex[:1] == '_' or ex[-1:] == '_' or ex in exclude or ex in mfc:
-            pass
-        else:
-            _dict[ex] = _dict_1[ex]
-
-    for method, func in _dict.items():
-        d = {'method': method, 'func': func}
-        if isinstance(toPart, str):
-            execString = \
-                __stringBody % {'method' : method, 'attribute' : toPart}
-        exec(execString, d)
-        setattr(fromClass, method, d[method])   ### NEWU!
-
-
-class ScrolledCanvas(TK.Frame):
-    """Modeled after the scrolled canvas class from Grayons's Tkinter book.
-
-    Used as the default canvas, which pops up automatically when
-    using turtle graphics functions or the Turtle class.
-    """
-    def __init__(self, master, width=500, height=350,
-                                          canvwidth=600, canvheight=500):
-        TK.Frame.__init__(self, master, width=width, height=height)
-        self._root = self.winfo_toplevel()
-        self.width, self.height = width, height
-        self.canvwidth, self.canvheight = canvwidth, canvheight
-        self.bg = "white"
-        self._canvas = TK.Canvas(master, width=width, height=height,
-                                 bg=self.bg, relief=TK.SUNKEN, borderwidth=2)
-        self.hscroll = TK.Scrollbar(master, command=self._canvas.xview,
-                                    orient=TK.HORIZONTAL)
-        self.vscroll = TK.Scrollbar(master, command=self._canvas.yview)
-        self._canvas.configure(xscrollcommand=self.hscroll.set,
-                               yscrollcommand=self.vscroll.set)
-        self.rowconfigure(0, weight=1, minsize=0)
-        self.columnconfigure(0, weight=1, minsize=0)
-        self._canvas.grid(padx=1, in_ = self, pady=1, row=0,
-                column=0, rowspan=1, columnspan=1, sticky='news')
-        self.vscroll.grid(padx=1, in_ = self, pady=1, row=0,
-                column=1, rowspan=1, columnspan=1, sticky='news')
-        self.hscroll.grid(padx=1, in_ = self, pady=1, row=1,
-                column=0, rowspan=1, columnspan=1, sticky='news')
-        self.reset()
-        self._root.bind('<Configure>', self.onResize)
-
-    def reset(self, canvwidth=None, canvheight=None, bg = None):
-        """Ajust canvas and scrollbars according to given canvas size."""
-        if canvwidth:
-            self.canvwidth = canvwidth
-        if canvheight:
-            self.canvheight = canvheight
-        if bg:
-            self.bg = bg
-        self._canvas.config(bg=bg,
-                        scrollregion=(-self.canvwidth//2, -self.canvheight//2,
-                                       self.canvwidth//2, self.canvheight//2))
-        self._canvas.xview_moveto(0.5*(self.canvwidth - self.width + 30) /
-                                                               self.canvwidth)
-        self._canvas.yview_moveto(0.5*(self.canvheight- self.height + 30) /
-                                                              self.canvheight)
-        self.adjustScrolls()
-
-
-    def adjustScrolls(self):
-        """ Adjust scrollbars according to window- and canvas-size.
-        """
-        cwidth = self._canvas.winfo_width()
-        cheight = self._canvas.winfo_height()
-        self._canvas.xview_moveto(0.5*(self.canvwidth-cwidth)/self.canvwidth)
-        self._canvas.yview_moveto(0.5*(self.canvheight-cheight)/self.canvheight)
-        if cwidth < self.canvwidth or cheight < self.canvheight:
-            self.hscroll.grid(padx=1, in_ = self, pady=1, row=1,
-                              column=0, rowspan=1, columnspan=1, sticky='news')
-            self.vscroll.grid(padx=1, in_ = self, pady=1, row=0,
-                              column=1, rowspan=1, columnspan=1, sticky='news')
-        else:
-            self.hscroll.grid_forget()
-            self.vscroll.grid_forget()
-
-    def onResize(self, event):
-        """self-explanatory"""
-        self.adjustScrolls()
-
-    def bbox(self, *args):
-        """ 'forward' method, which canvas itself has inherited...
-        """
-        return self._canvas.bbox(*args)
-
-    def cget(self, *args, **kwargs):
-        """ 'forward' method, which canvas itself has inherited...
-        """
-        return self._canvas.cget(*args, **kwargs)
-
-    def config(self, *args, **kwargs):
-        """ 'forward' method, which canvas itself has inherited...
-        """
-        self._canvas.config(*args, **kwargs)
-
-    def bind(self, *args, **kwargs):
-        """ 'forward' method, which canvas itself has inherited...
-        """
-        self._canvas.bind(*args, **kwargs)
-
-    def unbind(self, *args, **kwargs):
-        """ 'forward' method, which canvas itself has inherited...
-        """
-        self._canvas.unbind(*args, **kwargs)
-
-    def focus_force(self):
-        """ 'forward' method, which canvas itself has inherited...
-        """
-        self._canvas.focus_force()
-
-__forwardmethods(ScrolledCanvas, TK.Canvas, '_canvas')
-
-
-class _Root(TK.Tk):
-    """Root class for Screen based on Tkinter."""
-    def __init__(self):
-        TK.Tk.__init__(self)
-
-    def setupcanvas(self, width, height, cwidth, cheight):
-        self._canvas = ScrolledCanvas(self, width, height, cwidth, cheight)
-        self._canvas.pack(expand=1, fill="both")
-
-    def _getcanvas(self):
-        return self._canvas
-
-    def set_geometry(self, width, height, startx, starty):
-        self.geometry("%dx%d%+d%+d"%(width, height, startx, starty))
-
-    def ondestroy(self, destroy):
-        self.wm_protocol("WM_DELETE_WINDOW", destroy)
-
-    def win_width(self):
-        return self.winfo_screenwidth()
-
-    def win_height(self):
-        return self.winfo_screenheight()
-
-Canvas = TK.Canvas
-
-
-class TurtleScreenBase(object):
-    """Provide the basic graphics functionality.
-       Interface between Tkinter and turtle.py.
-
-       To port turtle.py to some different graphics toolkit
-       a corresponding TurtleScreenBase class has to be implemented.
-    """
-
-    @staticmethod
-    def _blankimage():
-        """return a blank image object
-        """
-        img = TK.PhotoImage(width=1, height=1)
-        img.blank()
-        return img
-
-    @staticmethod
-    def _image(filename):
-        """return an image object containing the
-        imagedata from a gif-file named filename.
-        """
-        return TK.PhotoImage(file=filename)
-
-    def __init__(self, cv):
-        self.cv = cv
-        if isinstance(cv, ScrolledCanvas):
-            w = self.cv.canvwidth
-            h = self.cv.canvheight
-        else:  # expected: ordinary TK.Canvas
-            w = int(self.cv.cget("width"))
-            h = int(self.cv.cget("height"))
-            self.cv.config(scrollregion = (-w//2, -h//2, w//2, h//2 ))
-        self.canvwidth = w
-        self.canvheight = h
-        self.xscale = self.yscale = 1.0
-
-    def _createpoly(self):
-        """Create an invisible polygon item on canvas self.cv)
-        """
-        return self.cv.create_polygon((0, 0, 0, 0, 0, 0), fill="", outline="")
-
-    def _drawpoly(self, polyitem, coordlist, fill=None,
-                  outline=None, width=None, top=False):
-        """Configure polygonitem polyitem according to provided
-        arguments:
-        coordlist is sequence of coordinates
-        fill is filling color
-        outline is outline color
-        top is a boolean value, which specifies if polyitem
-        will be put on top of the canvas' displaylist so it
-        will not be covered by other items.
-        """
-        cl = []
-        for x, y in coordlist:
-            cl.append(x * self.xscale)
-            cl.append(-y * self.yscale)
-        self.cv.coords(polyitem, *cl)
-        if fill is not None:
-            self.cv.itemconfigure(polyitem, fill=fill)
-        if outline is not None:
-            self.cv.itemconfigure(polyitem, outline=outline)
-        if width is not None:
-            self.cv.itemconfigure(polyitem, width=width)
-        if top:
-            self.cv.tag_raise(polyitem)
-
-    def _createline(self):
-        """Create an invisible line item on canvas self.cv)
-        """
-        return self.cv.create_line(0, 0, 0, 0, fill="", width=2,
-                                   capstyle = TK.ROUND)
-
-    def _drawline(self, lineitem, coordlist=None,
-                  fill=None, width=None, top=False):
-        """Configure lineitem according to provided arguments:
-        coordlist is sequence of coordinates
-        fill is drawing color
-        width is width of drawn line.
-        top is a boolean value, which specifies if polyitem
-        will be put on top of the canvas' displaylist so it
-        will not be covered by other items.
-        """
-        if coordlist is not None:
-            cl = []
-            for x, y in coordlist:
-                cl.append(x * self.xscale)
-                cl.append(-y * self.yscale)
-            self.cv.coords(lineitem, *cl)
-        if fill is not None:
-            self.cv.itemconfigure(lineitem, fill=fill)
-        if width is not None:
-            self.cv.itemconfigure(lineitem, width=width)
-        if top:
-            self.cv.tag_raise(lineitem)
-
-    def _delete(self, item):
-        """Delete graphics item from canvas.
-        If item is"all" delete all graphics items.
-        """
-        self.cv.delete(item)
-
-    def _update(self):
-        """Redraw graphics items on canvas
-        """
-        self.cv.update()
-
-    def _delay(self, delay):
-        """Delay subsequent canvas actions for delay ms."""
-        self.cv.after(delay)
-
-    def _iscolorstring(self, color):
-        """Check if the string color is a legal Tkinter color string.
-        """
-        try:
-            rgb = self.cv.winfo_rgb(color)
-            ok = True
-        except TK.TclError:
-            ok = False
-        return ok
-
-    def _bgcolor(self, color=None):
-        """Set canvas' backgroundcolor if color is not None,
-        else return backgroundcolor."""
-        if color is not None:
-            self.cv.config(bg = color)
-            self._update()
-        else:
-            return self.cv.cget("bg")
-
-    def _write(self, pos, txt, align, font, pencolor):
-        """Write txt at pos in canvas with specified font
-        and color.
-        Return text item and x-coord of right bottom corner
-        of text's bounding box."""
-        x, y = pos
-        x = x * self.xscale
-        y = y * self.yscale
-        anchor = {"left":"sw", "center":"s", "right":"se" }
-        item = self.cv.create_text(x-1, -y, text = txt, anchor = anchor[align],
-                                        fill = pencolor, font = font)
-        x0, y0, x1, y1 = self.cv.bbox(item)
-        self.cv.update()
-        return item, x1-1
-
-##    def _dot(self, pos, size, color):
-##        """may be implemented for some other graphics toolkit"""
-
-    def _onclick(self, item, fun, num=1, add=None):
-        """Bind fun to mouse-click event on turtle.
-        fun must be a function with two arguments, the coordinates
-        of the clicked point on the canvas.
-        num, the number of the mouse-button defaults to 1
-        """
-        if fun is None:
-            self.cv.tag_unbind(item, "<Button-%s>" % num)
-        else:
-            def eventfun(event):
-                x, y = (self.cv.canvasx(event.x)/self.xscale,
-                        -self.cv.canvasy(event.y)/self.yscale)
-                fun(x, y)
-            self.cv.tag_bind(item, "<Button-%s>" % num, eventfun, add)
-
-    def _onrelease(self, item, fun, num=1, add=None):
-        """Bind fun to mouse-button-release event on turtle.
-        fun must be a function with two arguments, the coordinates
-        of the point on the canvas where mouse button is released.
-        num, the number of the mouse-button defaults to 1
-
-        If a turtle is clicked, first _onclick-event will be performed,
-        then _onscreensclick-event.
-        """
-        if fun is None:
-            self.cv.tag_unbind(item, "<Button%s-ButtonRelease>" % num)
-        else:
-            def eventfun(event):
-                x, y = (self.cv.canvasx(event.x)/self.xscale,
-                        -self.cv.canvasy(event.y)/self.yscale)
-                fun(x, y)
-            self.cv.tag_bind(item, "<Button%s-ButtonRelease>" % num,
-                             eventfun, add)
-
-    def _ondrag(self, item, fun, num=1, add=None):
-        """Bind fun to mouse-move-event (with pressed mouse button) on turtle.
-        fun must be a function with two arguments, the coordinates of the
-        actual mouse position on the canvas.
-        num, the number of the mouse-button defaults to 1
-
-        Every sequence of mouse-move-events on a turtle is preceded by a
-        mouse-click event on that turtle.
-        """
-        if fun is None:
-            self.cv.tag_unbind(item, "<Button%s-Motion>" % num)
-        else:
-            def eventfun(event):
-                try:
-                    x, y = (self.cv.canvasx(event.x)/self.xscale,
-                           -self.cv.canvasy(event.y)/self.yscale)
-                    fun(x, y)
-                except:
-                    pass
-            self.cv.tag_bind(item, "<Button%s-Motion>" % num, eventfun, add)
-
-    def _onscreenclick(self, fun, num=1, add=None):
-        """Bind fun to mouse-click event on canvas.
-        fun must be a function with two arguments, the coordinates
-        of the clicked point on the canvas.
-        num, the number of the mouse-button defaults to 1
-
-        If a turtle is clicked, first _onclick-event will be performed,
-        then _onscreensclick-event.
-        """
-        if fun is None:
-            self.cv.unbind("<Button-%s>" % num)
-        else:
-            def eventfun(event):
-                x, y = (self.cv.canvasx(event.x)/self.xscale,
-                        -self.cv.canvasy(event.y)/self.yscale)
-                fun(x, y)
-            self.cv.bind("<Button-%s>" % num, eventfun, add)
-
-    def _onkey(self, fun, key):
-        """Bind fun to key-release event of key.
-        Canvas must have focus. See method listen
-        """
-        if fun is None:
-            self.cv.unbind("<KeyRelease-%s>" % key, None)
-        else:
-            def eventfun(event):
-                fun()
-            self.cv.bind("<KeyRelease-%s>" % key, eventfun)
-
-    def _listen(self):
-        """Set focus on canvas (in order to collect key-events)
-        """
-        self.cv.focus_force()
-
-    def _ontimer(self, fun, t):
-        """Install a timer, which calls fun after t milliseconds.
-        """
-        if t == 0:
-            self.cv.after_idle(fun)
-        else:
-            self.cv.after(t, fun)
-
-    def _createimage(self, image):
-        """Create and return image item on canvas.
-        """
-        return self.cv.create_image(0, 0, image=image)
-
-    def _drawimage(self, item, pos, image):
-        """Configure image item as to draw image object
-        at position (x,y) on canvas)
-        """
-        x, y = pos
-        self.cv.coords(item, (x * self.xscale, -y * self.yscale))
-        self.cv.itemconfig(item, image=image)
-
-    def _setbgpic(self, item, image):
-        """Configure image item as to draw image object
-        at center of canvas. Set item to the first item
-        in the displaylist, so it will be drawn below
-        any other item ."""
-        self.cv.itemconfig(item, image=image)
-        self.cv.tag_lower(item)
-
-    def _type(self, item):
-        """Return 'line' or 'polygon' or 'image' depending on
-        type of item.
-        """
-        return self.cv.type(item)
-
-    def _pointlist(self, item):
-        """returns list of coordinate-pairs of points of item
-        Example (for insiders):
-        >>> from turtle import *
-        >>> getscreen()._pointlist(getturtle().turtle._item)
-        [(0.0, 9.9999999999999982), (0.0, -9.9999999999999982),
-        (9.9999999999999982, 0.0)]
-        >>> """
-        cl = list(self.cv.coords(item))
-        pl = [(cl[i], -cl[i+1]) for i in range(0, len(cl), 2)]
-        return  pl
-
-    def _setscrollregion(self, srx1, sry1, srx2, sry2):
-        self.cv.config(scrollregion=(srx1, sry1, srx2, sry2))
-
-    def _rescale(self, xscalefactor, yscalefactor):
-        items = self.cv.find_all()
-        for item in items:
-            coordinates = list(self.cv.coords(item))
-            newcoordlist = []
-            while coordinates:
-                x, y = coordinates[:2]
-                newcoordlist.append(x * xscalefactor)
-                newcoordlist.append(y * yscalefactor)
-                coordinates = coordinates[2:]
-            self.cv.coords(item, *newcoordlist)
-
-    def _resize(self, canvwidth=None, canvheight=None, bg=None):
-        """Resize the canvas, the turtles are drawing on. Does
-        not alter the drawing window.
-        """
-        # needs amendment
-        if not isinstance(self.cv, ScrolledCanvas):
-            return self.canvwidth, self.canvheight
-        if canvwidth is None and canvheight is None and bg is None:
-            return self.cv.canvwidth, self.cv.canvheight
-        if canvwidth is not None:
-            self.canvwidth = canvwidth
-        if canvheight is not None:
-            self.canvheight = canvheight
-        self.cv.reset(canvwidth, canvheight, bg)
-
-    def _window_size(self):
-        """ Return the width and height of the turtle window.
-        """
-        width = self.cv.winfo_width()
-        if width <= 1:  # the window isn't managed by a geometry manager
-            width = self.cv['width']
-        height = self.cv.winfo_height()
-        if height <= 1: # the window isn't managed by a geometry manager
-            height = self.cv['height']
-        return width, height
-
-
-##############################################################################
-###                  End of Tkinter - interface                            ###
-##############################################################################
-
-
-class Terminator (Exception):
-    """Will be raised in TurtleScreen.update, if _RUNNING becomes False.
-
-    Thus stops execution of turtle graphics script. Main purpose: use in
-    in the Demo-Viewer turtle.Demo.py.
-    """
-    pass
-
-
-class TurtleGraphicsError(Exception):
-    """Some TurtleGraphics Error
-    """
-
-
-class Shape(object):
-    """Data structure modeling shapes.
-
-    attribute _type is one of "polygon", "image", "compound"
-    attribute _data is - depending on _type a poygon-tuple,
-    an image or a list constructed using the addcomponent method.
-    """
-    def __init__(self, type_, data=None):
-        self._type = type_
-        if type_ == "polygon":
-            if isinstance(data, list):
-                data = tuple(data)
-        elif type_ == "image":
-            if isinstance(data, str):
-                if data.lower().endswith(".gif") and isfile(data):
-                    data = TurtleScreen._image(data)
-                # else data assumed to be Photoimage
-        elif type_ == "compound":
-            data = []
-        else:
-            raise TurtleGraphicsError("There is no shape type %s" % type_)
-        self._data = data
-
-    def addcomponent(self, poly, fill, outline=None):
-        """Add component to a shape of type compound.
-
-        Arguments: poly is a polygon, i. e. a tuple of number pairs.
-        fill is the fillcolor of the component,
-        outline is the outline color of the component.
-
-        call (for a Shapeobject namend s):
-        --   s.addcomponent(((0,0), (10,10), (-10,10)), "red", "blue")
-
-        Example:
-        >>> poly = ((0,0),(10,-5),(0,10),(-10,-5))
-        >>> s = Shape("compound")
-        >>> s.addcomponent(poly, "red", "blue")
-        ### .. add more components and then use register_shape()
-        """
-        if self._type != "compound":
-            raise TurtleGraphicsError("Cannot add component to %s Shape"
-                                                                % self._type)
-        if outline is None:
-            outline = fill
-        self._data.append([poly, fill, outline])
-
-
-class Tbuffer(object):
-    """Ring buffer used as undobuffer for RawTurtle objects."""
-    def __init__(self, bufsize=10):
-        self.bufsize = bufsize
-        self.buffer = [[None]] * bufsize
-        self.ptr = -1
-        self.cumulate = False
-    def reset(self, bufsize=None):
-        if bufsize is None:
-            for i in range(self.bufsize):
-                self.buffer[i] = [None]
-        else:
-            self.bufsize = bufsize
-            self.buffer = [[None]] * bufsize
-        self.ptr = -1
-    def push(self, item):
-        if self.bufsize > 0:
-            if not self.cumulate:
-                self.ptr = (self.ptr + 1) % self.bufsize
-                self.buffer[self.ptr] = item
-            else:
-                self.buffer[self.ptr].append(item)
-    def pop(self):
-        if self.bufsize > 0:
-            item = self.buffer[self.ptr]
-            if item is None:
-                return None
-            else:
-                self.buffer[self.ptr] = [None]
-                self.ptr = (self.ptr - 1) % self.bufsize
-                return (item)
-    def nr_of_items(self):
-        return self.bufsize - self.buffer.count([None])
-    def __repr__(self):
-        return str(self.buffer) + " " + str(self.ptr)
-
-
-
-class TurtleScreen(TurtleScreenBase):
-    """Provides screen oriented methods like setbg etc.
-
-    Only relies upon the methods of TurtleScreenBase and NOT
-    upon components of the underlying graphics toolkit -
-    which is Tkinter in this case.
-    """
-#    _STANDARD_DELAY = 5
-    _RUNNING = True
-
-    def __init__(self, cv, mode=_CFG["mode"],
-                 colormode=_CFG["colormode"], delay=_CFG["delay"]):
-        self._shapes = {
-                   "arrow" : Shape("polygon", ((-10,0), (10,0), (0,10))),
-                  "turtle" : Shape("polygon", ((0,16), (-2,14), (-1,10), (-4,7),
-                              (-7,9), (-9,8), (-6,5), (-7,1), (-5,-3), (-8,-6),
-                              (-6,-8), (-4,-5), (0,-7), (4,-5), (6,-8), (8,-6),
-                              (5,-3), (7,1), (6,5), (9,8), (7,9), (4,7), (1,10),
-                              (2,14))),
-                  "circle" : Shape("polygon", ((10,0), (9.51,3.09), (8.09,5.88),
-                              (5.88,8.09), (3.09,9.51), (0,10), (-3.09,9.51),
-                              (-5.88,8.09), (-8.09,5.88), (-9.51,3.09), (-10,0),
-                              (-9.51,-3.09), (-8.09,-5.88), (-5.88,-8.09),
-                              (-3.09,-9.51), (-0.00,-10.00), (3.09,-9.51),
-                              (5.88,-8.09), (8.09,-5.88), (9.51,-3.09))),
-                  "square" : Shape("polygon", ((10,-10), (10,10), (-10,10),
-                              (-10,-10))),
-                "triangle" : Shape("polygon", ((10,-5.77), (0,11.55),
-                              (-10,-5.77))),
-                  "classic": Shape("polygon", ((0,0),(-5,-9),(0,-7),(5,-9))),
-                   "blank" : Shape("image", self._blankimage())
-                  }
-
-        self._bgpics = {"nopic" : ""}
-
-        TurtleScreenBase.__init__(self, cv)
-        self._mode = mode
-        self._delayvalue = delay
-        self._colormode = _CFG["colormode"]
-        self._keys = []
-        self.clear()
-
-    def clear(self):
-        """Delete all drawings and all turtles from the TurtleScreen.
-
-        Reset empty TurtleScreen to it's initial state: white background,
-        no backgroundimage, no eventbindings and tracing on.
-
-        No argument.
-
-        Example (for a TurtleScreen instance named screen):
-        screen.clear()
-
-        Note: this method is not available as function.
-        """
-        self._delayvalue = _CFG["delay"]
-        self._colormode = _CFG["colormode"]
-        self._delete("all")
-        self._bgpic = self._createimage("")
-        self._bgpicname = "nopic"
-        self._tracing = 1
-        self._updatecounter = 0
-        self._turtles = []
-        self.bgcolor("white")
-        for btn in 1, 2, 3:
-            self.onclick(None, btn)
-        for key in self._keys[:]:
-            self.onkey(None, key)
-        Turtle._pen = None
-
-    def mode(self, mode=None):
-        """Set turtle-mode ('standard', 'logo' or 'world') and perform reset.
-
-        Optional argument:
-        mode -- on of the strings 'standard', 'logo' or 'world'
-
-        Mode 'standard' is compatible with turtle.py.
-        Mode 'logo' is compatible with most Logo-Turtle-Graphics.
-        Mode 'world' uses userdefined 'worldcoordinates'. *Attention*: in
-        this mode angles appear distorted if x/y unit-ratio doesn't equal 1.
-        If mode is not given, return the current mode.
-
-             Mode      Initial turtle heading     positive angles
-         ------------|-------------------------|-------------------
-          'standard'    to the right (east)       counterclockwise
-            'logo'        upward    (north)         clockwise
-
-        Examples:
-        >>> mode('logo')   # resets turtle heading to north
-        >>> mode()
-        'logo'
-        """
-        if mode == None:
-            return self._mode
-        mode = mode.lower()
-        if mode not in ["standard", "logo", "world"]:
-            raise TurtleGraphicsError("No turtle-graphics-mode %s" % mode)
-        self._mode = mode
-        if mode in ["standard", "logo"]:
-            self._setscrollregion(-self.canvwidth//2, -self.canvheight//2,
-                                       self.canvwidth//2, self.canvheight//2)
-            self.xscale = self.yscale = 1.0
-        self.reset()
-
-    def setworldcoordinates(self, llx, lly, urx, ury):
-        """Set up a user defined coordinate-system.
-
-        Arguments:
-        llx -- a number, x-coordinate of lower left corner of canvas
-        lly -- a number, y-coordinate of lower left corner of canvas
-        urx -- a number, x-coordinate of upper right corner of canvas
-        ury -- a number, y-coordinate of upper right corner of canvas
-
-        Set up user coodinat-system and switch to mode 'world' if necessary.
-        This performs a screen.reset. If mode 'world' is already active,
-        all drawings are redrawn according to the new coordinates.
-
-        But ATTENTION: in user-defined coordinatesystems angles may appear
-        distorted. (see Screen.mode())
-
-        Example (for a TurtleScreen instance named screen):
-        >>> screen.setworldcoordinates(-10,-0.5,50,1.5)
-        >>> for _ in range(36):
-                left(10)
-                forward(0.5)
-        """
-        if self.mode() != "world":
-            self.mode("world")
-        xspan = float(urx - llx)
-        yspan = float(ury - lly)
-        wx, wy = self._window_size()
-        self.screensize(wx-20, wy-20)
-        oldxscale, oldyscale = self.xscale, self.yscale
-        self.xscale = self.canvwidth / xspan
-        self.yscale = self.canvheight / yspan
-        srx1 = llx * self.xscale
-        sry1 = -ury * self.yscale
-        srx2 = self.canvwidth + srx1
-        sry2 = self.canvheight + sry1
-        self._setscrollregion(srx1, sry1, srx2, sry2)
-        self._rescale(self.xscale/oldxscale, self.yscale/oldyscale)
-        self.update()
-
-    def register_shape(self, name, shape=None):
-        """Adds a turtle shape to TurtleScreen's shapelist.
-
-        Arguments:
-        (1) name is the name of a gif-file and shape is None.
-            Installs the corresponding image shape.
-            !! Image-shapes DO NOT rotate when turning the turtle,
-            !! so they do not display the heading of the turtle!
-        (2) name is an arbitrary string and shape is a tuple
-            of pairs of coordinates. Installs the corresponding
-            polygon shape
-        (3) name is an arbitrary string and shape is a
-            (compound) Shape object. Installs the corresponding
-            compound shape.
-        To use a shape, you have to issue the command shape(shapename).
-
-        call: register_shape("turtle.gif")
-        --or: register_shape("tri", ((0,0), (10,10), (-10,10)))
-
-        Example (for a TurtleScreen instance named screen):
-        >>> screen.register_shape("triangle", ((5,-3),(0,5),(-5,-3)))
-
-        """
-        if shape is None:
-            # image
-            if name.lower().endswith(".gif"):
-                shape = Shape("image", self._image(name))
-            else:
-                raise TurtleGraphicsError("Bad arguments for register_shape.\n"
-                                          + "Use  help(register_shape)" )
-        elif isinstance(shape, tuple):
-            shape = Shape("polygon", shape)
-        ## else shape assumed to be Shape-instance
-        self._shapes[name] = shape
-        # print "shape added:" , self._shapes
-
-    def _colorstr(self, color):
-        """Return color string corresponding to args.
-
-        Argument may be a string or a tuple of three
-        numbers corresponding to actual colormode,
-        i.e. in the range 0<=n<=colormode.
-
-        If the argument doesn't represent a color,
-        an error is raised.
-        """
-        if len(color) == 1:
-            color = color[0]
-        if isinstance(color, str):
-            if self._iscolorstring(color) or color == "":
-                return color
-            else:
-                raise TurtleGraphicsError("bad color string: %s" % str(color))
-        try:
-            r, g, b = color
-        except:
-            raise TurtleGraphicsError("bad color arguments: %s" % str(color))
-        if self._colormode == 1.0:
-            r, g, b = [round(255.0*x) for x in (r, g, b)]
-        if not ((0 <= r <= 255) and (0 <= g <= 255) and (0 <= b <= 255)):
-            raise TurtleGraphicsError("bad color sequence: %s" % str(color))
-        return "#%02x%02x%02x" % (r, g, b)
-
-    def _color(self, cstr):
-        if not cstr.startswith("#"):
-            return cstr
-        if len(cstr) == 7:
-            cl = [int(cstr[i:i+2], 16) for i in (1, 3, 5)]
-        elif len(cstr) == 4:
-            cl = [16*int(cstr[h], 16) for h in cstr[1:]]
-        else:
-            raise TurtleGraphicsError("bad colorstring: %s" % cstr)
-        return tuple([c * self._colormode/255 for c in cl])
-
-    def colormode(self, cmode=None):
-        """Return the colormode or set it to 1.0 or 255.
-
-        Optional argument:
-        cmode -- one of the values 1.0 or 255
-
-        r, g, b values of colortriples have to be in range 0..cmode.
-
-        Example (for a TurtleScreen instance named screen):
-        >>> screen.colormode()
-        1.0
-        >>> screen.colormode(255)
-        >>> turtle.pencolor(240,160,80)
-        """
-        if cmode is None:
-            return self._colormode
-        if cmode == 1.0:
-            self._colormode = float(cmode)
-        elif cmode == 255:
-            self._colormode = int(cmode)
-
-    def reset(self):
-        """Reset all Turtles on the Screen to their initial state.
-
-        No argument.
-
-        Example (for a TurtleScreen instance named screen):
-        >>> screen.reset()
-        """
-        for turtle in self._turtles:
-            turtle._setmode(self._mode)
-            turtle.reset()
-
-    def turtles(self):
-        """Return the list of turtles on the screen.
-
-        Example (for a TurtleScreen instance named screen):
-        >>> screen.turtles()
-        [<turtle.Turtle object at 0x00E11FB0>]
-        """
-        return self._turtles
-
-    def bgcolor(self, *args):
-        """Set or return backgroundcolor of the TurtleScreen.
-
-        Arguments (if given): a color string or three numbers
-        in the range 0..colormode or a 3-tuple of such numbers.
-
-        Example (for a TurtleScreen instance named screen):
-        >>> screen.bgcolor("orange")
-        >>> screen.bgcolor()
-        'orange'
-        >>> screen.bgcolor(0.5,0,0.5)
-        >>> screen.bgcolor()
-        '#800080'
-        """
-        if args:
-            color = self._colorstr(args)
-        else:
-            color = None
-        color = self._bgcolor(color)
-        if color is not None:
-            color = self._color(color)
-        return color
-
-    def tracer(self, n=None, delay=None):
-        """Turns turtle animation on/off and set delay for update drawings.
-
-        Optional arguments:
-        n -- nonnegative  integer
-        delay -- nonnegative  integer
-
-        If n is given, only each n-th regular screen update is really performed.
-        (Can be used to accelerate the drawing of complex graphics.)
-        Second arguments sets delay value (see RawTurtle.delay())
-
-        Example (for a TurtleScreen instance named screen):
-        >>> screen.tracer(8, 25)
-        >>> dist = 2
-        >>> for i in range(200):
-                fd(dist)
-                rt(90)
-                dist += 2
-        """
-        if n is None:
-            return self._tracing
-        self._tracing = int(n)
-        self._updatecounter = 0
-        if delay is not None:
-            self._delayvalue = int(delay)
-        if self._tracing:
-            self.update()
-
-    def delay(self, delay=None):
-        """ Return or set the drawing delay in milliseconds.
-
-        Optional argument:
-        delay -- positive integer
-
-        Example (for a TurtleScreen instance named screen):
-        >>> screen.delay(15)
-        >>> screen.delay()
-        15
-        """
-        if delay is None:
-            return self._delayvalue
-        self._delayvalue = int(delay)
-
-    def _incrementudc(self):
-        "Increment upadate counter."""
-        if not TurtleScreen._RUNNING:
-            TurtleScreen._RUNNNING = True
-            raise Terminator
-        if self._tracing > 0:
-            self._updatecounter += 1
-            self._updatecounter %= self._tracing
-
-    def update(self):
-        """Perform a TurtleScreen update.
-        """
-        for t in self.turtles():
-            t._update_data()
-            t._drawturtle()
-        self._update()
-
-    def window_width(self):
-        """ Return the width of the turtle window.
-
-        Example (for a TurtleScreen instance named screen):
-        >>> screen.window_width()
-        640
-        """
-        return self._window_size()[0]
-
-    def window_height(self):
-        """ Return the height of the turtle window.
-
-        Example (for a TurtleScreen instance named screen):
-        >>> screen.window_height()
-        480
-        """
-        return self._window_size()[1]
-
-    def getcanvas(self):
-        """Return the Canvas of this TurtleScreen.
-
-        No argument.
-
-        Example (for a Screen instance named screen):
-        >>> cv = screen.getcanvas()
-        >>> cv
-        <turtle.ScrolledCanvas instance at 0x010742D8>
-        """
-        return self.cv
-
-    def getshapes(self):
-        """Return a list of names of all currently available turtle shapes.
-
-        No argument.
-
-        Example (for a TurtleScreen instance named screen):
-        >>> screen.getshapes()
-        ['arrow', 'blank', 'circle', ... , 'turtle']
-        """
-        return sorted(self._shapes.keys())
-
-    def onclick(self, fun, btn=1, add=None):
-        """Bind fun to mouse-click event on canvas.
-
-        Arguments:
-        fun -- a function with two arguments, the coordinates of the
-               clicked point on the canvas.
-        num -- the number of the mouse-button, defaults to 1
-
-        Example (for a TurtleScreen instance named screen
-        and a Turtle instance named turtle):
-
-        >>> screen.onclick(turtle.goto)
-
-        ### Subsequently clicking into the TurtleScreen will
-        ### make the turtle move to the clicked point.
-        >>> screen.onclick(None)
-
-        ### event-binding will be removed
-        """
-        self._onscreenclick(fun, btn, add)
-
-    def onkey(self, fun, key):
-        """Bind fun to key-release event of key.
-
-        Arguments:
-        fun -- a function with no arguments
-        key -- a string: key (e.g. "a") or key-symbol (e.g. "space")
-
-        In order ro be able to register key-events, TurtleScreen
-        must have focus. (See method listen.)
-
-        Example (for a TurtleScreen instance named screen
-        and a Turtle instance named turtle):
-
-        >>> def f():
-                fd(50)
-                lt(60)
-
-
-        >>> screen.onkey(f, "Up")
-        >>> screen.listen()
-
-        ### Subsequently the turtle can be moved by
-        ### repeatedly pressing the up-arrow key,
-        ### consequently drawing a hexagon
-        """
-        if fun == None:
-            self._keys.remove(key)
-        elif key not in self._keys:
-            self._keys.append(key)
-        self._onkey(fun, key)
-
-    def listen(self, xdummy=None, ydummy=None):
-        """Set focus on TurtleScreen (in order to collect key-events)
-
-        No arguments.
-        Dummy arguments are provided in order
-        to be able to pass listen to the onclick method.
-
-        Example (for a TurtleScreen instance named screen):
-        >>> screen.listen()
-        """
-        self._listen()
-
-    def ontimer(self, fun, t=0):
-        """Install a timer, which calls fun after t milliseconds.
-
-        Arguments:
-        fun -- a function with no arguments.
-        t -- a number >= 0
-
-        Example (for a TurtleScreen instance named screen):
-
-        >>> running = True
-        >>> def f():
-                if running:
-                        fd(50)
-                        lt(60)
-                        screen.ontimer(f, 250)
-
-        >>> f()   ### makes the turtle marching around
-        >>> running = False
-        """
-        self._ontimer(fun, t)
-
-    def bgpic(self, picname=None):
-        """Set background image or return name of current backgroundimage.
-
-        Optional argument:
-        picname -- a string, name of a gif-file or "nopic".
-
-        If picname is a filename, set the corresponing image as background.
-        If picname is "nopic", delete backgroundimage, if present.
-        If picname is None, return the filename of the current backgroundimage.
-
-        Example (for a TurtleScreen instance named screen):
-        >>> screen.bgpic()
-        'nopic'
-        >>> screen.bgpic("landscape.gif")
-        >>> screen.bgpic()
-        'landscape.gif'
-        """
-        if picname is None:
-            return self._bgpicname
-        if picname not in self._bgpics:
-            self._bgpics[picname] = self._image(picname)
-        self._setbgpic(self._bgpic, self._bgpics[picname])
-        self._bgpicname = picname
-
-    def screensize(self, canvwidth=None, canvheight=None, bg=None):
-        """Resize the canvas, the turtles are drawing on.
-
-        Optional arguments:
-        canvwidth -- positive integer, new width of canvas in pixels
-        canvheight --  positive integer, new height of canvas in pixels
-        bg -- colorstring or color-tupel, new backgroundcolor
-        If no arguments are given, return current (canvaswidth, canvasheight)
-
-        Do not alter the drawing window. To observe hidden parts of
-        the canvas use the scrollbars. (Can make visible those parts
-        of a drawing, which were outside the canvas before!)
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.screensize(2000,1500)
-            ### e. g. to search for an erroneously escaped turtle ;-)
-        """
-        return self._resize(canvwidth, canvheight, bg)
-
-    onscreenclick = onclick
-    resetscreen = reset
-    clearscreen = clear
-    addshape = register_shape
-
-class TNavigator(object):
-    """Navigation part of the RawTurtle.
-    Implements methods for turtle movement.
-    """
-    START_ORIENTATION = {
-        "standard": Vec2D(1.0, 0.0),
-        "world"   : Vec2D(1.0, 0.0),
-        "logo"    : Vec2D(0.0, 1.0)  }
-    DEFAULT_MODE = "standard"
-    DEFAULT_ANGLEOFFSET = 0
-    DEFAULT_ANGLEORIENT = 1
-
-    def __init__(self, mode=DEFAULT_MODE):
-        self._angleOffset = self.DEFAULT_ANGLEOFFSET
-        self._angleOrient = self.DEFAULT_ANGLEORIENT
-        self._mode = mode
-        self.undobuffer = None
-        self.degrees()
-        self._mode = None
-        self._setmode(mode)
-        TNavigator.reset(self)
-
-    def reset(self):
-        """reset turtle to its initial values
-
-        Will be overwritten by parent class
-        """
-        self._position = Vec2D(0.0, 0.0)
-        self._orient =  TNavigator.START_ORIENTATION[self._mode]
-
-    def _setmode(self, mode=None):
-        """Set turtle-mode to 'standard', 'world' or 'logo'.
-        """
-        if mode == None:
-            return self._mode
-        if mode not in ["standard", "logo", "world"]:
-            return
-        self._mode = mode
-        if mode in ["standard", "world"]:
-            self._angleOffset = 0
-            self._angleOrient = 1
-        else: # mode == "logo":
-            self._angleOffset = self._fullcircle/4.
-            self._angleOrient = -1
-
-    def _setDegreesPerAU(self, fullcircle):
-        """Helper function for degrees() and radians()"""
-        self._fullcircle = fullcircle
-        self._degreesPerAU = 360/fullcircle
-        if self._mode == "standard":
-            self._angleOffset = 0
-        else:
-            self._angleOffset = fullcircle/4.
-
-    def degrees(self, fullcircle=360.0):
-        """ Set angle measurement units to degrees.
-
-        Optional argument:
-        fullcircle -  a number
-
-        Set angle measurement units, i. e. set number
-        of 'degrees' for a full circle. Dafault value is
-        360 degrees.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.left(90)
-        >>> turtle.heading()
-        90
-        >>> turtle.degrees(400.0)  # angle measurement in gon
-        >>> turtle.heading()
-        100
-
-        """
-        self._setDegreesPerAU(fullcircle)
-
-    def radians(self):
-        """ Set the angle measurement units to radians.
-
-        No arguments.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.heading()
-        90
-        >>> turtle.radians()
-        >>> turtle.heading()
-        1.5707963267948966
-        """
-        self._setDegreesPerAU(2*math.pi)
-
-    def _go(self, distance):
-        """move turtle forward by specified distance"""
-        ende = self._position + self._orient * distance
-        self._goto(ende)
-
-    def _rotate(self, angle):
-        """Turn turtle counterclockwise by specified angle if angle > 0."""
-        angle *= self._degreesPerAU
-        self._orient = self._orient.rotate(angle)
-
-    def _goto(self, end):
-        """move turtle to position end."""
-        self._position = end
-
-    def forward(self, distance):
-        """Move the turtle forward by the specified distance.
-
-        Aliases: forward | fd
-
-        Argument:
-        distance -- a number (integer or float)
-
-        Move the turtle forward by the specified distance, in the direction
-        the turtle is headed.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.position()
-        (0.00, 0.00)
-        >>> turtle.forward(25)
-        >>> turtle.position()
-        (25.00,0.00)
-        >>> turtle.forward(-75)
-        >>> turtle.position()
-        (-50.00,0.00)
-        """
-        self._go(distance)
-
-    def back(self, distance):
-        """Move the turtle backward by distance.
-
-        Aliases: back | backward | bk
-
-        Argument:
-        distance -- a number
-
-        Move the turtle backward by distance ,opposite to the direction the
-        turtle is headed. Do not change the turtle's heading.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.position()
-        (0.00, 0.00)
-        >>> turtle.backward(30)
-        >>> turtle.position()
-        (-30.00, 0.00)
-        """
-        self._go(-distance)
-
-    def right(self, angle):
-        """Turn turtle right by angle units.
-
-        Aliases: right | rt
-
-        Argument:
-        angle -- a number (integer or float)
-
-        Turn turtle right by angle units. (Units are by default degrees,
-        but can be set via the degrees() and radians() functions.)
-        Angle orientation depends on mode. (See this.)
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.heading()
-        22.0
-        >>> turtle.right(45)
-        >>> turtle.heading()
-        337.0
-        """
-        self._rotate(-angle)
-
-    def left(self, angle):
-        """Turn turtle left by angle units.
-
-        Aliases: left | lt
-
-        Argument:
-        angle -- a number (integer or float)
-
-        Turn turtle left by angle units. (Units are by default degrees,
-        but can be set via the degrees() and radians() functions.)
-        Angle orientation depends on mode. (See this.)
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.heading()
-        22.0
-        >>> turtle.left(45)
-        >>> turtle.heading()
-        67.0
-        """
-        self._rotate(angle)
-
-    def pos(self):
-        """Return the turtle's current location (x,y), as a Vec2D-vector.
-
-        Aliases: pos | position
-
-        No arguments.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.pos()
-        (0.00, 240.00)
-        """
-        return self._position
-
-    def xcor(self):
-        """ Return the turtle's x coordinate.
-
-        No arguments.
-
-        Example (for a Turtle instance named turtle):
-        >>> reset()
-        >>> turtle.left(60)
-        >>> turtle.forward(100)
-        >>> print turtle.xcor()
-        50.0
-        """
-        return self._position[0]
-
-    def ycor(self):
-        """ Return the turtle's y coordinate
-        ---
-        No arguments.
-
-        Example (for a Turtle instance named turtle):
-        >>> reset()
-        >>> turtle.left(60)
-        >>> turtle.forward(100)
-        >>> print turtle.ycor()
-        86.6025403784
-        """
-        return self._position[1]
-
-
-    def goto(self, x, y=None):
-        """Move turtle to an absolute position.
-
-        Aliases: setpos | setposition | goto:
-
-        Arguments:
-        x -- a number      or     a pair/vector of numbers
-        y -- a number             None
-
-        call: goto(x, y)         # two coordinates
-        --or: goto((x, y))       # a pair (tuple) of coordinates
-        --or: goto(vec)          # e.g. as returned by pos()
-
-        Move turtle to an absolute position. If the pen is down,
-        a line will be drawn. The turtle's orientation does not change.
-
-        Example (for a Turtle instance named turtle):
-        >>> tp = turtle.pos()
-        >>> tp
-        (0.00, 0.00)
-        >>> turtle.setpos(60,30)
-        >>> turtle.pos()
-        (60.00,30.00)
-        >>> turtle.setpos((20,80))
-        >>> turtle.pos()
-        (20.00,80.00)
-        >>> turtle.setpos(tp)
-        >>> turtle.pos()
-        (0.00,0.00)
-        """
-        if y is None:
-            self._goto(Vec2D(*x))
-        else:
-            self._goto(Vec2D(x, y))
-
-    def home(self):
-        """Move turtle to the origin - coordinates (0,0).
-
-        No arguments.
-
-        Move turtle to the origin - coordinates (0,0) and set it's
-        heading to it's start-orientation (which depends on mode).
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.home()
-        """
-        self.goto(0, 0)
-        self.setheading(0)
-
-    def setx(self, x):
-        """Set the turtle's first coordinate to x
-
-        Argument:
-        x -- a number (integer or float)
-
-        Set the turtle's first coordinate to x, leave second coordinate
-        unchanged.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.position()
-        (0.00, 240.00)
-        >>> turtle.setx(10)
-        >>> turtle.position()
-        (10.00, 240.00)
-        """
-        self._goto(Vec2D(x, self._position[1]))
-
-    def sety(self, y):
-        """Set the turtle's second coordinate to y
-
-        Argument:
-        y -- a number (integer or float)
-
-        Set the turtle's first coordinate to x, second coordinate remains
-        unchanged.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.position()
-        (0.00, 40.00)
-        >>> turtle.sety(-10)
-        >>> turtle.position()
-        (0.00, -10.00)
-        """
-        self._goto(Vec2D(self._position[0], y))
-
-    def distance(self, x, y=None):
-        """Return the distance from the turtle to (x,y) in turtle step units.
-
-        Arguments:
-        x -- a number   or  a pair/vector of numbers   or   a turtle instance
-        y -- a number       None                            None
-
-        call: distance(x, y)         # two coordinates
-        --or: distance((x, y))       # a pair (tuple) of coordinates
-        --or: distance(vec)          # e.g. as returned by pos()
-        --or: distance(mypen)        # where mypen is another turtle
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.pos()
-        (0.00, 0.00)
-        >>> turtle.distance(30,40)
-        50.0
-        >>> pen = Turtle()
-        >>> pen.forward(77)
-        >>> turtle.distance(pen)
-        77.0
-        """
-        if y is not None:
-            pos = Vec2D(x, y)
-        if isinstance(x, Vec2D):
-            pos = x
-        elif isinstance(x, tuple):
-            pos = Vec2D(*x)
-        elif isinstance(x, TNavigator):
-            pos = x._position
-        return abs(pos - self._position)
-
-    def towards(self, x, y=None):
-        """Return the angle of the line from the turtle's position to (x, y).
-
-        Arguments:
-        x -- a number   or  a pair/vector of numbers   or   a turtle instance
-        y -- a number       None                            None
-
-        call: distance(x, y)         # two coordinates
-        --or: distance((x, y))       # a pair (tuple) of coordinates
-        --or: distance(vec)          # e.g. as returned by pos()
-        --or: distance(mypen)        # where mypen is another turtle
-
-        Return the angle, between the line from turtle-position to position
-        specified by x, y and the turtle's start orientation. (Depends on
-        modes - "standard" or "logo")
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.pos()
-        (10.00, 10.00)
-        >>> turtle.towards(0,0)
-        225.0
-        """
-        if y is not None:
-            pos = Vec2D(x, y)
-        if isinstance(x, Vec2D):
-            pos = x
-        elif isinstance(x, tuple):
-            pos = Vec2D(*x)
-        elif isinstance(x, TNavigator):
-            pos = x._position
-        x, y = pos - self._position
-        result = round(math.atan2(y, x)*180.0/math.pi, 10) % 360.0
-        result /= self._degreesPerAU
-        return (self._angleOffset + self._angleOrient*result) % self._fullcircle
-
-    def heading(self):
-        """ Return the turtle's current heading.
-
-        No arguments.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.left(67)
-        >>> turtle.heading()
-        67.0
-        """
-        x, y = self._orient
-        result = round(math.atan2(y, x)*180.0/math.pi, 10) % 360.0
-        result /= self._degreesPerAU
-        return (self._angleOffset + self._angleOrient*result) % self._fullcircle
-
-    def setheading(self, to_angle):
-        """Set the orientation of the turtle to to_angle.
-
-        Aliases:  setheading | seth
-
-        Argument:
-        to_angle -- a number (integer or float)
-
-        Set the orientation of the turtle to to_angle.
-        Here are some common directions in degrees:
-
-         standard - mode:          logo-mode:
-        -------------------|--------------------
-           0 - east                0 - north
-          90 - north              90 - east
-         180 - west              180 - south
-         270 - south             270 - west
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.setheading(90)
-        >>> turtle.heading()
-        90
-        """
-        angle = (to_angle - self.heading())*self._angleOrient
-        full = self._fullcircle
-        angle = (angle+full/2.)%full - full/2.
-        self._rotate(angle)
-
-    def circle(self, radius, extent = None, steps = None):
-        """ Draw a circle with given radius.
-
-        Arguments:
-        radius -- a number
-        extent (optional) -- a number
-        steps (optional) -- an integer
-
-        Draw a circle with given radius. The center is radius units left
-        of the turtle; extent - an angle - determines which part of the
-        circle is drawn. If extent is not given, draw the entire circle.
-        If extent is not a full circle, one endpoint of the arc is the
-        current pen position. Draw the arc in counterclockwise direction
-        if radius is positive, otherwise in clockwise direction. Finally
-        the direction of the turtle is changed by the amount of extent.
-
-        As the circle is approximated by an inscribed regular polygon,
-        steps determines the number of steps to use. If not given,
-        it will be calculated automatically. Maybe used to draw regular
-        polygons.
-
-        call: circle(radius)                  # full circle
-        --or: circle(radius, extent)          # arc
-        --or: circle(radius, extent, steps)
-        --or: circle(radius, steps=6)         # 6-sided polygon
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.circle(50)
-        >>> turtle.circle(120, 180)  # semicircle
-        """
-        if self.undobuffer:
-            self.undobuffer.push(["seq"])
-            self.undobuffer.cumulate = True
-        speed = self.speed()
-        if extent is None:
-            extent = self._fullcircle
-        if steps is None:
-            frac = abs(extent)/self._fullcircle
-            steps = 1+int(min(11+abs(radius)/6.0, 59.0)*frac)
-        w = 1.0 * extent / steps
-        w2 = 0.5 * w
-        l = 2.0 * radius * math.sin(w2*math.pi/180.0*self._degreesPerAU)
-        if radius < 0:
-            l, w, w2 = -l, -w, -w2
-        tr = self._tracer()
-        dl = self._delay()
-        if speed == 0:
-            self._tracer(0, 0)
-        else:
-            self.speed(0)
-        self._rotate(w2)
-        for i in range(steps):
-            self.speed(speed)
-            self._go(l)
-            self.speed(0)
-            self._rotate(w)
-        self._rotate(-w2)
-        if speed == 0:
-            self._tracer(tr, dl)
-        self.speed(speed)
-        if self.undobuffer:
-            self.undobuffer.cumulate = False
-
-## three dummy methods to be implemented by child class:
-
-    def speed(self, s=0):
-        """dummy method - to be overwritten by child class"""
-    def _tracer(self, a=None, b=None):
-        """dummy method - to be overwritten by child class"""
-    def _delay(self, n=None):
-        """dummy method - to be overwritten by child class"""
-
-    fd = forward
-    bk = back
-    backward = back
-    rt = right
-    lt = left
-    position = pos
-    setpos = goto
-    setposition = goto
-    seth = setheading
-
-
-class TPen(object):
-    """Drawing part of the RawTurtle.
-    Implements drawing properties.
-    """
-    def __init__(self, resizemode=_CFG["resizemode"]):
-        self._resizemode = resizemode # or "user" or "noresize"
-        self.undobuffer = None
-        TPen._reset(self)
-
-    def _reset(self, pencolor=_CFG["pencolor"],
-                     fillcolor=_CFG["fillcolor"]):
-        self._pensize = 1
-        self._shown = True
-        self._pencolor = pencolor
-        self._fillcolor = fillcolor
-        self._drawing = True
-        self._speed = 3
-        self._stretchfactor = (1, 1)
-        self._tilt = 0
-        self._outlinewidth = 1
-        ### self.screen = None  # to override by child class
-
-    def resizemode(self, rmode=None):
-        """Set resizemode to one of the values: "auto", "user", "noresize".
-
-        (Optional) Argument:
-        rmode -- one of the strings "auto", "user", "noresize"
-
-        Different resizemodes have the following effects:
-          - "auto" adapts the appearance of the turtle
-                   corresponding to the value of pensize.
-          - "user" adapts the appearance of the turtle according to the
-                   values of stretchfactor and outlinewidth (outline),
-                   which are set by shapesize()
-          - "noresize" no adaption of the turtle's appearance takes place.
-        If no argument is given, return current resizemode.
-        resizemode("user") is called by a call of shapesize with arguments.
-
-
-        Examples (for a Turtle instance named turtle):
-        >>> turtle.resizemode("noresize")
-        >>> turtle.resizemode()
-        'noresize'
-        """
-        if rmode is None:
-            return self._resizemode
-        rmode = rmode.lower()
-        if rmode in ["auto", "user", "noresize"]:
-            self.pen(resizemode=rmode)
-
-    def pensize(self, width=None):
-        """Set or return the line thickness.
-
-        Aliases:  pensize | width
-
-        Argument:
-        width -- positive number
-
-        Set the line thickness to width or return it. If resizemode is set
-        to "auto" and turtleshape is a polygon, that polygon is drawn with
-        the same line thickness. If no argument is given, current pensize
-        is returned.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.pensize()
-        1
-        turtle.pensize(10)   # from here on lines of width 10 are drawn
-        """
-        if width is None:
-            return self._pensize
-        self.pen(pensize=width)
-
-
-    def penup(self):
-        """Pull the pen up -- no drawing when moving.
-
-        Aliases: penup | pu | up
-
-        No argument
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.penup()
-        """
-        if not self._drawing:
-            return
-        self.pen(pendown=False)
-
-    def pendown(self):
-        """Pull the pen down -- drawing when moving.
-
-        Aliases: pendown | pd | down
-
-        No argument.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.pendown()
-        """
-        if self._drawing:
-            return
-        self.pen(pendown=True)
-
-    def isdown(self):
-        """Return True if pen is down, False if it's up.
-
-        No argument.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.penup()
-        >>> turtle.isdown()
-        False
-        >>> turtle.pendown()
-        >>> turtle.isdown()
-        True
-        """
-        return self._drawing
-
-    def speed(self, speed=None):
-        """ Return or set the turtle's speed.
-
-        Optional argument:
-        speed -- an integer in the range 0..10 or a speedstring (see below)
-
-        Set the turtle's speed to an integer value in the range 0 .. 10.
-        If no argument is given: return current speed.
-
-        If input is a number greater than 10 or smaller than 0.5,
-        speed is set to 0.
-        Speedstrings  are mapped to speedvalues in the following way:
-            'fastest' :  0
-            'fast'    :  10
-            'normal'  :  6
-            'slow'    :  3
-            'slowest' :  1
-        speeds from 1 to 10 enforce increasingly faster animation of
-        line drawing and turtle turning.
-
-        Attention:
-        speed = 0 : *no* animation takes place. forward/back makes turtle jump
-        and likewise left/right make the turtle turn instantly.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.speed(3)
-        """
-        speeds = {'fastest':0, 'fast':10, 'normal':6, 'slow':3, 'slowest':1 }
-        if speed is None:
-            return self._speed
-        if speed in speeds:
-            speed = speeds[speed]
-        elif 0.5 < speed < 10.5:
-            speed = int(round(speed))
-        else:
-            speed = 0
-        self.pen(speed=speed)
-
-    def color(self, *args):
-        """Return or set the pencolor and fillcolor.
-
-        Arguments:
-        Several input formats are allowed.
-        They use 0, 1, 2, or 3 arguments as follows:
-
-        color()
-            Return the current pencolor and the current fillcolor
-            as a pair of color specification strings as are returned
-            by pencolor and fillcolor.
-        color(colorstring), color((r,g,b)), color(r,g,b)
-            inputs as in pencolor, set both, fillcolor and pencolor,
-            to the given value.
-        color(colorstring1, colorstring2),
-        color((r1,g1,b1), (r2,g2,b2))
-            equivalent to pencolor(colorstring1) and fillcolor(colorstring2)
-            and analogously, if the other input format is used.
-
-        If turtleshape is a polygon, outline and interior of that polygon
-        is drawn with the newly set colors.
-        For mor info see: pencolor, fillcolor
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.color('red', 'green')
-        >>> turtle.color()
-        ('red', 'green')
-        >>> colormode(255)
-        >>> color((40, 80, 120), (160, 200, 240))
-        >>> color()
-        ('#285078', '#a0c8f0')
-        """
-        if args:
-            l = len(args)
-            if l == 1:
-                pcolor = fcolor = args[0]
-            elif l == 2:
-                pcolor, fcolor = args
-            elif l == 3:
-                pcolor = fcolor = args
-            pcolor = self._colorstr(pcolor)
-            fcolor = self._colorstr(fcolor)
-            self.pen(pencolor=pcolor, fillcolor=fcolor)
-        else:
-            return self._color(self._pencolor), self._color(self._fillcolor)
-
-    def pencolor(self, *args):
-        """ Return or set the pencolor.
-
-        Arguments:
-        Four input formats are allowed:
-          - pencolor()
-            Return the current pencolor as color specification string,
-            possibly in hex-number format (see example).
-            May be used as input to another color/pencolor/fillcolor call.
-          - pencolor(colorstring)
-            s is a Tk color specification string, such as "red" or "yellow"
-          - pencolor((r, g, b))
-            *a tuple* of r, g, and b, which represent, an RGB color,
-            and each of r, g, and b are in the range 0..colormode,
-            where colormode is either 1.0 or 255
-          - pencolor(r, g, b)
-            r, g, and b represent an RGB color, and each of r, g, and b
-            are in the range 0..colormode
-
-        If turtleshape is a polygon, the outline of that polygon is drawn
-        with the newly set pencolor.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.pencolor('brown')
-        >>> tup = (0.2, 0.8, 0.55)
-        >>> turtle.pencolor(tup)
-        >>> turtle.pencolor()
-        '#33cc8c'
-        """
-        if args:
-            color = self._colorstr(args)
-            if color == self._pencolor:
-                return
-            self.pen(pencolor=color)
-        else:
-            return self._color(self._pencolor)
-
-    def fillcolor(self, *args):
-        """ Return or set the fillcolor.
-
-        Arguments:
-        Four input formats are allowed:
-          - fillcolor()
-            Return the current fillcolor as color specification string,
-            possibly in hex-number format (see example).
-            May be used as input to another color/pencolor/fillcolor call.
-          - fillcolor(colorstring)
-            s is a Tk color specification string, such as "red" or "yellow"
-          - fillcolor((r, g, b))
-            *a tuple* of r, g, and b, which represent, an RGB color,
-            and each of r, g, and b are in the range 0..colormode,
-            where colormode is either 1.0 or 255
-          - fillcolor(r, g, b)
-            r, g, and b represent an RGB color, and each of r, g, and b
-            are in the range 0..colormode
-
-        If turtleshape is a polygon, the interior of that polygon is drawn
-        with the newly set fillcolor.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.fillcolor('violet')
-        >>> col = turtle.pencolor()
-        >>> turtle.fillcolor(col)
-        >>> turtle.fillcolor(0, .5, 0)
-        """
-        if args:
-            color = self._colorstr(args)
-            if color == self._fillcolor:
-                return
-            self.pen(fillcolor=color)
-        else:
-            return self._color(self._fillcolor)
-
-    def showturtle(self):
-        """Makes the turtle visible.
-
-        Aliases: showturtle | st
-
-        No argument.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.hideturtle()
-        >>> turtle.showturtle()
-        """
-        self.pen(shown=True)
-
-    def hideturtle(self):
-        """Makes the turtle invisible.
-
-        Aliases: hideturtle | ht
-
-        No argument.
-
-        It's a good idea to do this while you're in the
-        middle of a complicated drawing, because hiding
-        the turtle speeds up the drawing observably.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.hideturtle()
-        """
-        self.pen(shown=False)
-
-    def isvisible(self):
-        """Return True if the Turtle is shown, False if it's hidden.
-
-        No argument.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.hideturtle()
-        >>> print turtle.isvisible():
-        False
-        """
-        return self._shown
-
-    def pen(self, pen=None, **pendict):
-        """Return or set the pen's attributes.
-
-        Arguments:
-            pen -- a dictionary with some or all of the below listed keys.
-            **pendict -- one or more keyword-arguments with the below
-                         listed keys as keywords.
-
-        Return or set the pen's attributes in a 'pen-dictionary'
-        with the following key/value pairs:
-           "shown"      :   True/False
-           "pendown"    :   True/False
-           "pencolor"   :   color-string or color-tuple
-           "fillcolor"  :   color-string or color-tuple
-           "pensize"    :   positive number
-           "speed"      :   number in range 0..10
-           "resizemode" :   "auto" or "user" or "noresize"
-           "stretchfactor": (positive number, positive number)
-           "outline"    :   positive number
-           "tilt"       :   number
-
-        This dicionary can be used as argument for a subsequent
-        pen()-call to restore the former pen-state. Moreover one
-        or more of these attributes can be provided as keyword-arguments.
-        This can be used to set several pen attributes in one statement.
-
-
-        Examples (for a Turtle instance named turtle):
-        >>> turtle.pen(fillcolor="black", pencolor="red", pensize=10)
-        >>> turtle.pen()
-        {'pensize': 10, 'shown': True, 'resizemode': 'auto', 'outline': 1,
-        'pencolor': 'red', 'pendown': True, 'fillcolor': 'black',
-        'stretchfactor': (1,1), 'speed': 3}
-        >>> penstate=turtle.pen()
-        >>> turtle.color("yellow","")
-        >>> turtle.penup()
-        >>> turtle.pen()
-        {'pensize': 10, 'shown': True, 'resizemode': 'auto', 'outline': 1,
-        'pencolor': 'yellow', 'pendown': False, 'fillcolor': '',
-        'stretchfactor': (1,1), 'speed': 3}
-        >>> p.pen(penstate, fillcolor="green")
-        >>> p.pen()
-        {'pensize': 10, 'shown': True, 'resizemode': 'auto', 'outline': 1,
-        'pencolor': 'red', 'pendown': True, 'fillcolor': 'green',
-        'stretchfactor': (1,1), 'speed': 3}
-        """
-        _pd =  {"shown"         : self._shown,
-                "pendown"       : self._drawing,
-                "pencolor"      : self._pencolor,
-                "fillcolor"     : self._fillcolor,
-                "pensize"       : self._pensize,
-                "speed"         : self._speed,
-                "resizemode"    : self._resizemode,
-                "stretchfactor" : self._stretchfactor,
-                "outline"       : self._outlinewidth,
-                "tilt"          : self._tilt
-               }
-
-        if not (pen or pendict):
-            return _pd
-
-        if isinstance(pen, dict):
-            p = pen
-        else:
-            p = {}
-        p.update(pendict)
-
-        _p_buf = {}
-        for key in p:
-            _p_buf[key] = _pd[key]
-
-        if self.undobuffer:
-            self.undobuffer.push(("pen", _p_buf))
-
-        newLine = False
-        if "pendown" in p:
-            if self._drawing != p["pendown"]:
-                newLine = True
-        if "pencolor" in p:
-            if isinstance(p["pencolor"], tuple):
-                p["pencolor"] = self._colorstr((p["pencolor"],))
-            if self._pencolor != p["pencolor"]:
-                newLine = True
-        if "pensize" in p:
-            if self._pensize != p["pensize"]:
-                newLine = True
-        if newLine:
-            self._newLine()
-        if "pendown" in p:
-            self._drawing = p["pendown"]
-        if "pencolor" in p:
-            self._pencolor = p["pencolor"]
-        if "pensize" in p:
-            self._pensize = p["pensize"]
-        if "fillcolor" in p:
-            if isinstance(p["fillcolor"], tuple):
-                p["fillcolor"] = self._colorstr((p["fillcolor"],))
-            self._fillcolor = p["fillcolor"]
-        if "speed" in p:
-            self._speed = p["speed"]
-        if "resizemode" in p:
-            self._resizemode = p["resizemode"]
-        if "stretchfactor" in p:
-            sf = p["stretchfactor"]
-            if isinstance(sf, (int, float)):
-                sf = (sf, sf)
-            self._stretchfactor = sf
-        if "outline" in p:
-            self._outlinewidth = p["outline"]
-        if "shown" in p:
-            self._shown = p["shown"]
-        if "tilt" in p:
-            self._tilt = p["tilt"]
-        self._update()
-
-## three dummy methods to be implemented by child class:
-
-    def _newLine(self, usePos = True):
-        """dummy method - to be overwritten by child class"""
-    def _update(self, count=True, forced=False):
-        """dummy method - to be overwritten by child class"""
-    def _color(self, args):
-        """dummy method - to be overwritten by child class"""
-    def _colorstr(self, args):
-        """dummy method - to be overwritten by child class"""
-
-    width = pensize
-    up = penup
-    pu = penup
-    pd = pendown
-    down = pendown
-    st = showturtle
-    ht = hideturtle
-
-
-class _TurtleImage(object):
-    """Helper class: Datatype to store Turtle attributes
-    """
-
-    def __init__(self, screen, shapeIndex):
-        self.screen = screen
-        self._type = None
-        self._setshape(shapeIndex)
-
-    def _setshape(self, shapeIndex):
-        screen = self.screen # RawTurtle.screens[self.screenIndex]
-        self.shapeIndex = shapeIndex
-        if self._type == "polygon" == screen._shapes[shapeIndex]._type:
-            return
-        if self._type == "image" == screen._shapes[shapeIndex]._type:
-            return
-        if self._type in ["image", "polygon"]:
-            screen._delete(self._item)
-        elif self._type == "compound":
-            for item in self._item:
-                screen._delete(item)
-        self._type = screen._shapes[shapeIndex]._type
-        if self._type == "polygon":
-            self._item = screen._createpoly()
-        elif self._type == "image":
-            self._item = screen._createimage(screen._shapes["blank"]._data)
-        elif self._type == "compound":
-            self._item = [screen._createpoly() for item in
-                                          screen._shapes[shapeIndex]._data]
-
-
-class RawTurtle(TPen, TNavigator):
-    """Animation part of the RawTurtle.
-    Puts RawTurtle upon a TurtleScreen and provides tools for
-    it's animation.
-    """
-    screens = []
-
-    def __init__(self, canvas=None,
-                 shape=_CFG["shape"],
-                 undobuffersize=_CFG["undobuffersize"],
-                 visible=_CFG["visible"]):
-        if isinstance(canvas, Screen):
-            self.screen = canvas
-        elif isinstance(canvas, TurtleScreen):
-            if canvas not in RawTurtle.screens:
-                RawTurtle.screens.append(canvas)
-            self.screen = canvas
-        elif isinstance(canvas, (ScrolledCanvas, Canvas)):
-            for screen in RawTurtle.screens:
-                if screen.cv == canvas:
-                    self.screen = screen
-                    break
-            else:
-                self.screen = TurtleScreen(canvas)
-                RawTurtle.screens.append(self.screen)
-        else:
-            raise TurtleGraphicsError("bad cavas argument %s" % canvas)
-
-        screen = self.screen
-        TNavigator.__init__(self, screen.mode())
-        TPen.__init__(self)
-        screen._turtles.append(self)
-        self.drawingLineItem = screen._createline()
-        self.turtle = _TurtleImage(screen, shape)
-        self._poly = None
-        self._creatingPoly = False
-        self._fillitem = self._fillpath = None
-        self._shown = visible
-        self._hidden_from_screen = False
-        self.currentLineItem = screen._createline()
-        self.currentLine = [self._position]
-        self.items = [self.currentLineItem]
-        self.stampItems = []
-        self._undobuffersize = undobuffersize
-        self.undobuffer = Tbuffer(undobuffersize)
-        self._update()
-
-    def reset(self):
-        """Delete the turtle's drawings and restore it's default values.
-
-        No argument.
-,
-        Delete the turtle's drawings from the screen, re-center the turtle
-        and set variables to the default values.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.position()
-        (0.00,-22.00)
-        >>> turtle.heading()
-        100.0
-        >>> turtle.reset()
-        >>> turtle.position()
-        (0.00,0.00)
-        >>> turtle.heading()
-        0.0
-        """
-        TNavigator.reset(self)
-        TPen._reset(self)
-        self._clear()
-        self._drawturtle()
-        self._update()
-
-    def setundobuffer(self, size):
-        """Set or disable undobuffer.
-
-        Argument:
-        size -- an integer or None
-
-        If size is an integer an empty undobuffer of given size is installed.
-        Size gives the maximum number of turtle-actions that can be undone
-        by the undo() function.
-        If size is None, no undobuffer is present.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.setundobuffer(42)
-        """
-        if size is None:
-            self.undobuffer = None
-        else:
-            self.undobuffer = Tbuffer(size)
-
-    def undobufferentries(self):
-        """Return count of entries in the undobuffer.
-
-        No argument.
-
-        Example (for a Turtle instance named turtle):
-        >>> while undobufferentries():
-                undo()
-        """
-        if self.undobuffer is None:
-            return 0
-        return self.undobuffer.nr_of_items()
-
-    def _clear(self):
-        """Delete all of pen's drawings"""
-        self._fillitem = self._fillpath = None
-        for item in self.items:
-            self.screen._delete(item)
-        self.currentLineItem = self.screen._createline()
-        self.currentLine = []
-        if self._drawing:
-            self.currentLine.append(self._position)
-        self.items = [self.currentLineItem]
-        self.clearstamps()
-        self.setundobuffer(self._undobuffersize)
-
-
-    def clear(self):
-        """Delete the turtle's drawings from the screen. Do not move turtle.
-
-        No arguments.
-
-        Delete the turtle's drawings from the screen. Do not move turtle.
-        State and position of the turtle as well as drawings of other
-        turtles are not affected.
-
-        Examples (for a Turtle instance named turtle):
-        >>> turtle.clear()
-        """
-        self._clear()
-        self._update()
-
-    def _update_data(self):
-        self.screen._incrementudc()
-        if self.screen._updatecounter != 0:
-            return
-        if len(self.currentLine)>1:
-            self.screen._drawline(self.currentLineItem, self.currentLine,
-                                  self._pencolor, self._pensize)
-
-    def _update(self):
-        """Perform a Turtle-data update.
-        """
-        screen = self.screen
-        if screen._tracing == 0:
-            return
-        elif screen._tracing == 1:
-            self._update_data()
-            self._drawturtle()
-            screen._update()                  # TurtleScreenBase
-            screen._delay(screen._delayvalue) # TurtleScreenBase
-        else:
-            self._update_data()
-            if screen._updatecounter == 0:
-                for t in screen.turtles():
-                    t._drawturtle()
-                screen._update()
-
-    def _tracer(self, flag=None, delay=None):
-        """Turns turtle animation on/off and set delay for update drawings.
-
-        Optional arguments:
-        n -- nonnegative  integer
-        delay -- nonnegative  integer
-
-        If n is given, only each n-th regular screen update is really performed.
-        (Can be used to accelerate the drawing of complex graphics.)
-        Second arguments sets delay value (see RawTurtle.delay())
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.tracer(8, 25)
-        >>> dist = 2
-        >>> for i in range(200):
-                turtle.fd(dist)
-                turtle.rt(90)
-                dist += 2
-        """
-        return self.screen.tracer(flag, delay)
-
-    def _color(self, args):
-        return self.screen._color(args)
-
-    def _colorstr(self, args):
-        return self.screen._colorstr(args)
-
-    def _cc(self, args):
-        """Convert colortriples to hexstrings.
-        """
-        if isinstance(args, str):
-            return args
-        try:
-            r, g, b = args
-        except:
-            raise TurtleGraphicsError("bad color arguments: %s" % str(args))
-        if self.screen._colormode == 1.0:
-            r, g, b = [round(255.0*x) for x in (r, g, b)]
-        if not ((0 <= r <= 255) and (0 <= g <= 255) and (0 <= b <= 255)):
-            raise TurtleGraphicsError("bad color sequence: %s" % str(args))
-        return "#%02x%02x%02x" % (r, g, b)
-
-    def clone(self):
-        """Create and return a clone of the turtle.
-
-        No argument.
-
-        Create and return a clone of the turtle with same position, heading
-        and turtle properties.
-
-        Example (for a Turtle instance named mick):
-        mick = Turtle()
-        joe = mick.clone()
-        """
-        screen = self.screen
-        self._newLine(self._drawing)
-
-        turtle = self.turtle
-        self.screen = None
-        self.turtle = None  # too make self deepcopy-able
-
-        q = deepcopy(self)
-
-        self.screen = screen
-        self.turtle = turtle
-
-        q.screen = screen
-        q.turtle = _TurtleImage(screen, self.turtle.shapeIndex)
-
-        screen._turtles.append(q)
-        ttype = screen._shapes[self.turtle.shapeIndex]._type
-        if ttype == "polygon":
-            q.turtle._item = screen._createpoly()
-        elif ttype == "image":
-            q.turtle._item = screen._createimage(screen._shapes["blank"]._data)
-        elif ttype == "compound":
-            q.turtle._item = [screen._createpoly() for item in
-                              screen._shapes[self.turtle.shapeIndex]._data]
-        q.currentLineItem = screen._createline()
-        q._update()
-        return q
-
-    def shape(self, name=None):
-        """Set turtle shape to shape with given name / return current shapename.
-
-        Optional argument:
-        name -- a string, which is a valid shapename
-
-        Set turtle shape to shape with given name or, if name is not given,
-        return name of current shape.
-        Shape with name must exist in the TurtleScreen's shape dictionary.
-        Initially there are the following polygon shapes:
-        'arrow', 'turtle', 'circle', 'square', 'triangle', 'classic'.
-        To learn about how to deal with shapes see Screen-method register_shape.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.shape()
-        'arrow'
-        >>> turtle.shape("turtle")
-        >>> turtle.shape()
-        'turtle'
-        """
-        if name is None:
-            return self.turtle.shapeIndex
-        if not name in self.screen.getshapes():
-            raise TurtleGraphicsError("There is no shape named %s" % name)
-        self.turtle._setshape(name)
-        self._update()
-
-    def shapesize(self, stretch_wid=None, stretch_len=None, outline=None):
-        """Set/return turtle's stretchfactors/outline. Set resizemode to "user".
-
-        Optinonal arguments:
-           stretch_wid : positive number
-           stretch_len : positive number
-           outline  : positive number
-
-        Return or set the pen's attributes x/y-stretchfactors and/or outline.
-        Set resizemode to "user".
-        If and only if resizemode is set to "user", the turtle will be displayed
-        stretched according to its stretchfactors:
-        stretch_wid is stretchfactor perpendicular to orientation
-        stretch_len is stretchfactor in direction of turtles orientation.
-        outline determines the width of the shapes's outline.
-
-        Examples (for a Turtle instance named turtle):
-        >>> turtle.resizemode("user")
-        >>> turtle.shapesize(5, 5, 12)
-        >>> turtle.shapesize(outline=8)
-        """
-        if stretch_wid is None and stretch_len is None and outline == None:
-            stretch_wid, stretch_len = self._stretchfactor
-            return stretch_wid, stretch_len, self._outlinewidth
-        if stretch_wid is not None:
-            if stretch_len is None:
-                stretchfactor = stretch_wid, stretch_wid
-            else:
-                stretchfactor = stretch_wid, stretch_len
-        elif stretch_len is not None:
-            stretchfactor = self._stretchfactor[0], stretch_len
-        else:
-            stretchfactor = self._stretchfactor
-        if outline is None:
-            outline = self._outlinewidth
-        self.pen(resizemode="user",
-                 stretchfactor=stretchfactor, outline=outline)
-
-    def settiltangle(self, angle):
-        """Rotate the turtleshape to point in the specified direction
-
-        Optional argument:
-        angle -- number
-
-        Rotate the turtleshape to point in the direction specified by angle,
-        regardless of its current tilt-angle. DO NOT change the turtle's
-        heading (direction of movement).
-
-
-        Examples (for a Turtle instance named turtle):
-        >>> turtle.shape("circle")
-        >>> turtle.shapesize(5,2)
-        >>> turtle.settiltangle(45)
-        >>> stamp()
-        >>> turtle.fd(50)
-        >>> turtle.settiltangle(-45)
-        >>> stamp()
-        >>> turtle.fd(50)
-        """
-        tilt = -angle * self._degreesPerAU * self._angleOrient
-        tilt = (tilt * math.pi / 180.0) % (2*math.pi)
-        self.pen(resizemode="user", tilt=tilt)
-
-    def tiltangle(self):
-        """Return the current tilt-angle.
-
-        No argument.
-
-        Return the current tilt-angle, i. e. the angle between the
-        orientation of the turtleshape and the heading of the turtle
-        (it's direction of movement).
-
-        Examples (for a Turtle instance named turtle):
-        >>> turtle.shape("circle")
-        >>> turtle.shapesize(5,2)
-        >>> turtle.tilt(45)
-        >>> turtle.tiltangle()
-        >>>
-        """
-        tilt = -self._tilt * (180.0/math.pi) * self._angleOrient
-        return (tilt / self._degreesPerAU) % self._fullcircle
-
-    def tilt(self, angle):
-        """Rotate the turtleshape by angle.
-
-        Argument:
-        angle - a number
-
-        Rotate the turtleshape by angle from its current tilt-angle,
-        but do NOT change the turtle's heading (direction of movement).
-
-        Examples (for a Turtle instance named turtle):
-        >>> turtle.shape("circle")
-        >>> turtle.shapesize(5,2)
-        >>> turtle.tilt(30)
-        >>> turtle.fd(50)
-        >>> turtle.tilt(30)
-        >>> turtle.fd(50)
-        """
-        self.settiltangle(angle + self.tiltangle())
-
-    def _polytrafo(self, poly):
-        """Computes transformed polygon shapes from a shape
-        according to current position and heading.
-        """
-        screen = self.screen
-        p0, p1 = self._position
-        e0, e1 = self._orient
-        e = Vec2D(e0, e1 * screen.yscale / screen.xscale)
-        e0, e1 = (1.0 / abs(e)) * e
-        return [(p0+(e1*x+e0*y)/screen.xscale, p1+(-e0*x+e1*y)/screen.yscale)
-                                                           for (x, y) in poly]
-
-    def _drawturtle(self):
-        """Manages the correct rendering of the turtle with respect to
-        it's shape, resizemode, strech and tilt etc."""
-        screen = self.screen
-        shape = screen._shapes[self.turtle.shapeIndex]
-        ttype = shape._type
-        titem = self.turtle._item
-        if self._shown and screen._updatecounter == 0 and screen._tracing > 0:
-            self._hidden_from_screen = False
-            tshape = shape._data
-            if ttype == "polygon":
-                if self._resizemode == "noresize":
-                    w = 1
-                    shape = tshape
-                else:
-                    if self._resizemode == "auto":
-                        lx = ly = max(1, self._pensize/5.0)
-                        w = self._pensize
-                        tiltangle = 0
-                    elif self._resizemode == "user":
-                        lx, ly = self._stretchfactor
-                        w = self._outlinewidth
-                        tiltangle = self._tilt
-                    shape = [(lx*x, ly*y) for (x, y) in tshape]
-                    t0, t1 = math.sin(tiltangle), math.cos(tiltangle)
-                    shape = [(t1*x+t0*y, -t0*x+t1*y) for (x, y) in shape]
-                shape = self._polytrafo(shape)
-                fc, oc = self._fillcolor, self._pencolor
-                screen._drawpoly(titem, shape, fill=fc, outline=oc,
-                                                      width=w, top=True)
-            elif ttype == "image":
-                screen._drawimage(titem, self._position, tshape)
-            elif ttype == "compound":
-                lx, ly = self._stretchfactor
-                w = self._outlinewidth
-                for item, (poly, fc, oc) in zip(titem, tshape):
-                    poly = [(lx*x, ly*y) for (x, y) in poly]
-                    poly = self._polytrafo(poly)
-                    screen._drawpoly(item, poly, fill=self._cc(fc),
-                                     outline=self._cc(oc), width=w, top=True)
-        else:
-            if self._hidden_from_screen:
-                return
-            if ttype == "polygon":
-                screen._drawpoly(titem, ((0, 0), (0, 0), (0, 0)), "", "")
-            elif ttype == "image":
-                screen._drawimage(titem, self._position,
-                                          screen._shapes["blank"]._data)
-            elif ttype == "compound":
-                for item in titem:
-                    screen._drawpoly(item, ((0, 0), (0, 0), (0, 0)), "", "")
-            self._hidden_from_screen = True
-
-##############################  stamp stuff  ###############################
-
-    def stamp(self):
-        """Stamp a copy of the turtleshape onto the canvas and return it's id.
-
-        No argument.
-
-        Stamp a copy of the turtle shape onto the canvas at the current
-        turtle position. Return a stamp_id for that stamp, which can be
-        used to delete it by calling clearstamp(stamp_id).
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.color("blue")
-        >>> turtle.stamp()
-        13
-        >>> turtle.fd(50)
-        """
-        screen = self.screen
-        shape = screen._shapes[self.turtle.shapeIndex]
-        ttype = shape._type
-        tshape = shape._data
-        if ttype == "polygon":
-            stitem = screen._createpoly()
-            if self._resizemode == "noresize":
-                w = 1
-                shape = tshape
-            else:
-                if self._resizemode == "auto":
-                    lx = ly = max(1, self._pensize/5.0)
-                    w = self._pensize
-                    tiltangle = 0
-                elif self._resizemode == "user":
-                    lx, ly = self._stretchfactor
-                    w = self._outlinewidth
-                    tiltangle = self._tilt
-                shape = [(lx*x, ly*y) for (x, y) in tshape]
-                t0, t1 = math.sin(tiltangle), math.cos(tiltangle)
-                shape = [(t1*x+t0*y, -t0*x+t1*y) for (x, y) in shape]
-            shape = self._polytrafo(shape)
-            fc, oc = self._fillcolor, self._pencolor
-            screen._drawpoly(stitem, shape, fill=fc, outline=oc,
-                                                  width=w, top=True)
-        elif ttype == "image":
-            stitem = screen._createimage("")
-            screen._drawimage(stitem, self._position, tshape)
-        elif ttype == "compound":
-            stitem = []
-            for element in tshape:
-                item = screen._createpoly()
-                stitem.append(item)
-            stitem = tuple(stitem)
-            lx, ly = self._stretchfactor
-            w = self._outlinewidth
-            for item, (poly, fc, oc) in zip(stitem, tshape):
-                poly = [(lx*x, ly*y) for (x, y) in poly]
-                poly = self._polytrafo(poly)
-                screen._drawpoly(item, poly, fill=self._cc(fc),
-                                 outline=self._cc(oc), width=w, top=True)
-        self.stampItems.append(stitem)
-        self.undobuffer.push(("stamp", stitem))
-        return stitem
-
-    def _clearstamp(self, stampid):
-        """does the work for clearstamp() and clearstamps()
-        """
-        if stampid in self.stampItems:
-            if isinstance(stampid, tuple):
-                for subitem in stampid:
-                    self.screen._delete(subitem)
-            else:
-                self.screen._delete(stampid)
-            self.stampItems.remove(stampid)
-        # Delete stampitem from undobuffer if necessary
-        # if clearstamp is called directly.
-        item = ("stamp", stampid)
-        buf = self.undobuffer
-        if item not in buf.buffer:
-            return
-        index = buf.buffer.index(item)
-        buf.buffer.remove(item)
-        if index <= buf.ptr:
-            buf.ptr = (buf.ptr - 1) % buf.bufsize
-        buf.buffer.insert((buf.ptr+1)%buf.bufsize, [None])
-
-    def clearstamp(self, stampid):
-        """Delete stamp with given stampid
-
-        Argument:
-        stampid - an integer, must be return value of previous stamp() call.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.color("blue")
-        >>> astamp = turtle.stamp()
-        >>> turtle.fd(50)
-        >>> turtle.clearstamp(astamp)
-        """
-        self._clearstamp(stampid)
-        self._update()
-
-    def clearstamps(self, n=None):
-        """Delete all or first/last n of turtle's stamps.
-
-        Optional argument:
-        n -- an integer
-
-        If n is None, delete all of pen's stamps,
-        else if n > 0 delete first n stamps
-        else if n < 0 delete last n stamps.
-
-        Example (for a Turtle instance named turtle):
-        >>> for i in range(8):
-                turtle.stamp(); turtle.fd(30)
-        ...
-        >>> turtle.clearstamps(2)
-        >>> turtle.clearstamps(-2)
-        >>> turtle.clearstamps()
-        """
-        if n is None:
-            toDelete = self.stampItems[:]
-        elif n >= 0:
-            toDelete = self.stampItems[:n]
-        else:
-            toDelete = self.stampItems[n:]
-        for item in toDelete:
-            self._clearstamp(item)
-        self._update()
-
-    def _goto(self, end):
-        """Move the pen to the point end, thereby drawing a line
-        if pen is down. All other methodes for turtle movement depend
-        on this one.
-        """
-        ## Version mit undo-stuff
-        go_modes = ( self._drawing,
-                     self._pencolor,
-                     self._pensize,
-                     isinstance(self._fillpath, list))
-        screen = self.screen
-        undo_entry = ("go", self._position, end, go_modes,
-                      (self.currentLineItem,
-                      self.currentLine[:],
-                      screen._pointlist(self.currentLineItem),
-                      self.items[:])
-                      )
-        if self.undobuffer:
-            self.undobuffer.push(undo_entry)
-        start = self._position
-        if self._speed and screen._tracing == 1:
-            diff = (end-start)
-            diffsq = (diff[0]*screen.xscale)**2 + (diff[1]*screen.yscale)**2
-            nhops = 1+int((diffsq**0.5)/(3*(1.1**self._speed)*self._speed))
-            delta = diff * (1.0/nhops)
-            for n in range(1, nhops):
-                if n == 1:
-                    top = True
-                else:
-                    top = False
-                self._position = start + delta * n
-                if self._drawing:
-                    screen._drawline(self.drawingLineItem,
-                                     (start, self._position),
-                                     self._pencolor, self._pensize, top)
-                self._update()
-            if self._drawing:
-                screen._drawline(self.drawingLineItem, ((0, 0), (0, 0)),
-                                               fill="", width=self._pensize)
-        # Turtle now at end,
-        if self._drawing: # now update currentLine
-            self.currentLine.append(end)
-        if isinstance(self._fillpath, list):
-            self._fillpath.append(end)
-        ######    vererbung!!!!!!!!!!!!!!!!!!!!!!
-        self._position = end
-        if self._creatingPoly:
-            self._poly.append(end)
-        if len(self.currentLine) > 42: # 42! answer to the ultimate question
-                                       # of life, the universe and everything
-            self._newLine()
-        self._update() #count=True)
-
-    def _undogoto(self, entry):
-        """Reverse a _goto. Used for undo()
-        """
-        old, new, go_modes, coodata = entry
-        drawing, pc, ps, filling = go_modes
-        cLI, cL, pl, items = coodata
-        screen = self.screen
-        if abs(self._position - new) > 0.5:
-            print ("undogoto: HALLO-DA-STIMMT-WAS-NICHT!")
-        # restore former situation
-        self.currentLineItem = cLI
-        self.currentLine = cL
-
-        if pl == [(0, 0), (0, 0)]:
-            usepc = ""
-        else:
-            usepc = pc
-        screen._drawline(cLI, pl, fill=usepc, width=ps)
-
-        todelete = [i for i in self.items if (i not in items) and
-                                       (screen._type(i) == "line")]
-        for i in todelete:
-            screen._delete(i)
-            self.items.remove(i)
-
-        start = old
-        if self._speed and screen._tracing == 1:
-            diff = old - new
-            diffsq = (diff[0]*screen.xscale)**2 + (diff[1]*screen.yscale)**2
-            nhops = 1+int((diffsq**0.5)/(3*(1.1**self._speed)*self._speed))
-            delta = diff * (1.0/nhops)
-            for n in range(1, nhops):
-                if n == 1:
-                    top = True
-                else:
-                    top = False
-                self._position = new + delta * n
-                if drawing:
-                    screen._drawline(self.drawingLineItem,
-                                     (start, self._position),
-                                     pc, ps, top)
-                self._update()
-            if drawing:
-                screen._drawline(self.drawingLineItem, ((0, 0), (0, 0)),
-                                               fill="", width=ps)
-        # Turtle now at position old,
-        self._position = old
-        ##  if undo is done during crating a polygon, the last vertex
-        ##  will be deleted. if the polygon is entirel deleted,
-        ##  creatigPoly will be set to False.
-        ##  Polygons created before the last one will not be affected by undo()
-        if self._creatingPoly:
-            if len(self._poly) > 0:
-                self._poly.pop()
-            if self._poly == []:
-                self._creatingPoly = False
-                self._poly = None
-        if filling:
-            if self._fillpath == []:
-                self._fillpath = None
-                print("Unwahrscheinlich in _undogoto!")
-            elif self._fillpath is not None:
-                self._fillpath.pop()
-        self._update() #count=True)
-
-    def _rotate(self, angle):
-        """Turns pen clockwise by angle.
-        """
-        if self.undobuffer:
-            self.undobuffer.push(("rot", angle, self._degreesPerAU))
-        angle *= self._degreesPerAU
-        neworient = self._orient.rotate(angle)
-        tracing = self.screen._tracing
-        if tracing == 1 and self._speed > 0:
-            anglevel = 3.0 * self._speed
-            steps = 1 + int(abs(angle)/anglevel)
-            delta = 1.0*angle/steps
-            for _ in range(steps):
-                self._orient = self._orient.rotate(delta)
-                self._update()
-        self._orient = neworient
-        self._update()
-
-    def _newLine(self, usePos=True):
-        """Closes current line item and starts a new one.
-           Remark: if current line became too long, animation
-           performance (via _drawline) slowed down considerably.
-        """
-        if len(self.currentLine) > 1:
-            self.screen._drawline(self.currentLineItem, self.currentLine,
-                                      self._pencolor, self._pensize)
-            self.currentLineItem = self.screen._createline()
-            self.items.append(self.currentLineItem)
-        else:
-            self.screen._drawline(self.currentLineItem, top=True)
-        self.currentLine = []
-        if usePos:
-            self.currentLine = [self._position]
-
-    def filling(self):
-        """Return fillstate (True if filling, False else).
-
-        No argument.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.begin_fill()
-        >>> if turtle.filling():
-                turtle.pensize(5)
-        else:
-                turtle.pensize(3)
-        """
-        return isinstance(self._fillpath, list)
-
-##    def fill(self, flag=None):
-##        """Call fill(True) before drawing a shape to fill, fill(False) when done.
-##
-##        Optional argument:
-##        flag -- True/False (or 1/0 respectively)
-##
-##        Call fill(True) before drawing the shape you want to fill,
-##        and  fill(False) when done.
-##        When used without argument: return fillstate (True if filling,
-##        False else)
-##
-##        Example (for a Turtle instance named turtle):
-##        >>> turtle.fill(True)
-##        >>> turtle.forward(100)
-##        >>> turtle.left(90)
-##        >>> turtle.forward(100)
-##        >>> turtle.left(90)
-##        >>> turtle.forward(100)
-##        >>> turtle.left(90)
-##        >>> turtle.forward(100)
-##        >>> turtle.fill(False)
-##        """
-##        filling = isinstance(self._fillpath, list)
-##        if flag is None:
-##            return filling
-##        screen = self.screen
-##        entry1 = entry2 = ()
-##        if filling:
-##            if len(self._fillpath) > 2:
-##                self.screen._drawpoly(self._fillitem, self._fillpath,
-##                                      fill=self._fillcolor)
-##                entry1 = ("dofill", self._fillitem)
-##        if flag:
-##            self._fillitem = self.screen._createpoly()
-##            self.items.append(self._fillitem)
-##            self._fillpath = [self._position]
-##            entry2 = ("beginfill", self._fillitem) # , self._fillpath)
-##            self._newLine()
-##        else:
-##            self._fillitem = self._fillpath = None
-##        if self.undobuffer:
-##            if entry1 == ():
-##                if entry2 != ():
-##                    self.undobuffer.push(entry2)
-##            else:
-##                if entry2 == ():
-##                    self.undobuffer.push(entry1)
-##                else:
-##                    self.undobuffer.push(["seq", entry1, entry2])
-##        self._update()
-
-    def begin_fill(self):
-        """Called just before drawing a shape to be filled.
-
-        No argument.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.color("black", "red")
-        >>> turtle.begin_fill()
-        >>> turtle.circle(60)
-        >>> turtle.end_fill()
-        """
-        if not self.filling():
-            self._fillitem = self.screen._createpoly()
-            self.items.append(self._fillitem)
-        self._fillpath = [self._position]
-        self._newLine()
-        if self.undobuffer:
-            self.undobuffer.push(("beginfill", self._fillitem))
-        self._update()
-
-
-    def end_fill(self):
-        """Fill the shape drawn after the call begin_fill().
-
-        No argument.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.color("black", "red")
-        >>> turtle.begin_fill()
-        >>> turtle.circle(60)
-        >>> turtle.end_fill()
-        """
-        if self.filling():
-            if len(self._fillpath) > 2:
-                self.screen._drawpoly(self._fillitem, self._fillpath,
-                                      fill=self._fillcolor)
-                if self.undobuffer:
-                    self.undobuffer.push(("dofill", self._fillitem))
-            self._fillitem = self._fillpath = None
-            self._update()
-
-    def dot(self, size=None, *color):
-        """Draw a dot with diameter size, using color.
-
-        Optional argumentS:
-        size -- an integer >= 1 (if given)
-        color -- a colorstring or a numeric color tuple
-
-        Draw a circular dot with diameter size, using color.
-        If size is not given, the maximum of pensize+4 and 2*pensize is used.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.dot()
-        >>> turtle.fd(50); turtle.dot(20, "blue"); turtle.fd(50)
-        """
-        #print "dot-1:", size, color
-        if not color:
-            if isinstance(size, (str, tuple)):
-                color = self._colorstr(size)
-                size = self._pensize + max(self._pensize, 4)
-            else:
-                color = self._pencolor
-                if not size:
-                    size = self._pensize + max(self._pensize, 4)
-        else:
-            if size is None:
-                size = self._pensize + max(self._pensize, 4)
-            color = self._colorstr(color)
-        #print "dot-2:", size, color
-        if hasattr(self.screen, "_dot"):
-            item = self.screen._dot(self._position, size, color)
-            #print "dot:", size, color, "item:", item
-            self.items.append(item)
-            if self.undobuffer:
-                self.undobuffer.push(("dot", item))
-        else:
-            pen = self.pen()
-            if self.undobuffer:
-                self.undobuffer.push(["seq"])
-                self.undobuffer.cumulate = True
-            try:
-                if self.resizemode() == 'auto':
-                    self.ht()
-                self.pendown()
-                self.pensize(size)
-                self.pencolor(color)
-                self.forward(0)
-            finally:
-                self.pen(pen)
-            if self.undobuffer:
-                self.undobuffer.cumulate = False
-
-    def _write(self, txt, align, font):
-        """Performs the writing for write()
-        """
-        item, end = self.screen._write(self._position, txt, align, font,
-                                                          self._pencolor)
-        self.items.append(item)
-        if self.undobuffer:
-            self.undobuffer.push(("wri", item))
-        return end
-
-    def write(self, arg, move=False, align="left", font=("Arial", 8, "normal")):
-        """Write text at the current turtle position.
-
-        Arguments:
-        arg -- info, which is to be written to the TurtleScreen
-        move (optional) -- True/False
-        align (optional) -- one of the strings "left", "center" or right"
-        font (optional) -- a triple (fontname, fontsize, fonttype)
-
-        Write text - the string representation of arg - at the current
-        turtle position according to align ("left", "center" or right")
-        and with the given font.
-        If move is True, the pen is moved to the bottom-right corner
-        of the text. By default, move is False.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.write('Home = ', True, align="center")
-        >>> turtle.write((0,0), True)
-        """
-        if self.undobuffer:
-            self.undobuffer.push(["seq"])
-            self.undobuffer.cumulate = True
-        end = self._write(str(arg), align.lower(), font)
-        if move:
-            x, y = self.pos()
-            self.setpos(end, y)
-        if self.undobuffer:
-            self.undobuffer.cumulate = False
-
-    def begin_poly(self):
-        """Start recording the vertices of a polygon.
-
-        No argument.
-
-        Start recording the vertices of a polygon. Current turtle position
-        is first point of polygon.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.begin_poly()
-        """
-        self._poly = [self._position]
-        self._creatingPoly = True
-
-    def end_poly(self):
-        """Stop recording the vertices of a polygon.
-
-        No argument.
-
-        Stop recording the vertices of a polygon. Current turtle position is
-        last point of polygon. This will be connected with the first point.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.end_poly()
-        """
-        self._creatingPoly = False
-
-    def get_poly(self):
-        """Return the lastly recorded polygon.
-
-        No argument.
-
-        Example (for a Turtle instance named turtle):
-        >>> p = turtle.get_poly()
-        >>> turtle.register_shape("myFavouriteShape", p)
-        """
-        ## check if there is any poly?  -- 1st solution:
-        if self._poly is not None:
-            return tuple(self._poly)
-
-    def getscreen(self):
-        """Return the TurtleScreen object, the turtle is drawing  on.
-
-        No argument.
-
-        Return the TurtleScreen object, the turtle is drawing  on.
-        So TurtleScreen-methods can be called for that object.
-
-        Example (for a Turtle instance named turtle):
-        >>> ts = turtle.getscreen()
-        >>> ts
-        <turtle.TurtleScreen object at 0x0106B770>
-        >>> ts.bgcolor("pink")
-        """
-        return self.screen
-
-    def getturtle(self):
-        """Return the Turtleobject itself.
-
-        No argument.
-
-        Only reasonable use: as a function to return the 'anonymous turtle':
-
-        Example:
-        >>> pet = getturtle()
-        >>> pet.fd(50)
-        >>> pet
-        <turtle.Turtle object at 0x0187D810>
-        >>> turtles()
-        [<turtle.Turtle object at 0x0187D810>]
-        """
-        return self
-
-    getpen = getturtle
-
-
-    ################################################################
-    ### screen oriented methods recurring to methods of TurtleScreen
-    ################################################################
-
-##    def window_width(self):
-##        """ Returns the width of the turtle window.
-##
-##        No argument.
-##
-##        Example (for a TurtleScreen instance named screen):
-##        >>> screen.window_width()
-##        640
-##        """
-##        return self.screen._window_size()[0]
-##
-##    def window_height(self):
-##        """ Return the height of the turtle window.
-##
-##        No argument.
-##
-##        Example (for a TurtleScreen instance named screen):
-##        >>> screen.window_height()
-##        480
-##        """
-##        return self.screen._window_size()[1]
-
-    def _delay(self, delay=None):
-        """Set delay value which determines speed of turtle animation.
-        """
-        return self.screen.delay(delay)
-
-    #####   event binding methods   #####
-
-    def onclick(self, fun, btn=1, add=None):
-        """Bind fun to mouse-click event on this turtle on canvas.
-
-        Arguments:
-        fun --  a function with two arguments, to which will be assigned
-                the coordinates of the clicked point on the canvas.
-        num --  number of the mouse-button defaults to 1 (left mouse button).
-        add --  True or False. If True, new binding will be added, otherwise
-                it will replace a former binding.
-
-        Example for the anonymous turtle, i. e. the procedural way:
-
-        >>> def turn(x, y):
-                left(360)
-
-        >>> onclick(turn) # Now clicking into the turtle will turn it.
-        >>> onclick(None)  # event-binding will be removed
-        """
-        self.screen._onclick(self.turtle._item, fun, btn, add)
-        self._update()
-
-    def onrelease(self, fun, btn=1, add=None):
-        """Bind fun to mouse-button-release event on this turtle on canvas.
-
-        Arguments:
-        fun -- a function with two arguments, to which will be assigned
-                the coordinates of the clicked point on the canvas.
-        num --  number of the mouse-button defaults to 1 (left mouse button).
-
-        Example (for a MyTurtle instance named joe):
-        >>> class MyTurtle(Turtle):
-                def glow(self,x,y):
-                        self.fillcolor("red")
-                def unglow(self,x,y):
-                        self.fillcolor("")
-
-        >>> joe = MyTurtle()
-        >>> joe.onclick(joe.glow)
-        >>> joe.onrelease(joe.unglow)
-        ### clicking on joe turns fillcolor red,
-        ### unclicking turns it to transparent.
-        """
-        self.screen._onrelease(self.turtle._item, fun, btn, add)
-        self._update()
-
-    def ondrag(self, fun, btn=1, add=None):
-        """Bind fun to mouse-move event on this turtle on canvas.
-
-        Arguments:
-        fun -- a function with two arguments, to which will be assigned
-               the coordinates of the clicked point on the canvas.
-        num -- number of the mouse-button defaults to 1 (left mouse button).
-
-        Every sequence of mouse-move-events on a turtle is preceded by a
-        mouse-click event on that turtle.
-
-        Example (for a Turtle instance named turtle):
-        >>> turtle.ondrag(turtle.goto)
-
-        ### Subsequently clicking and dragging a Turtle will
-        ### move it across the screen thereby producing handdrawings
-        ### (if pen is down).
-        """
-        self.screen._ondrag(self.turtle._item, fun, btn, add)
-
-
-    def _undo(self, action, data):
-        """Does the main part of the work for undo()
-        """
-        if self.undobuffer is None:
-            return
-        if action == "rot":
-            angle, degPAU = data
-            self._rotate(-angle*degPAU/self._degreesPerAU)
-            dummy = self.undobuffer.pop()
-        elif action == "stamp":
-            stitem = data[0]
-            self.clearstamp(stitem)
-        elif action == "go":
-            self._undogoto(data)
-        elif action in ["wri", "dot"]:
-            item = data[0]
-            self.screen._delete(item)
-            self.items.remove(item)
-        elif action == "dofill":
-            item = data[0]
-            self.screen._drawpoly(item, ((0, 0),(0, 0),(0, 0)),
-                                  fill="", outline="")
-        elif action == "beginfill":
-            item = data[0]
-            self._fillitem = self._fillpath = None
-            if item in self.items:
-                self.screen._delete(item)
-                self.items.remove(item)
-        elif action == "pen":
-            TPen.pen(self, data[0])
-            self.undobuffer.pop()
-
-    def undo(self):
-        """undo (repeatedly) the last turtle action.
-
-        No argument.
-
-        undo (repeatedly) the last turtle action.
-        Number of available undo actions is determined by the size of
-        the undobuffer.
-
-        Example (for a Turtle instance named turtle):
-        >>> for i in range(4):
-                turtle.fd(50); turtle.lt(80)
-
-        >>> for i in range(8):
-                turtle.undo()
-        """
-        if self.undobuffer is None:
-            return
-        item = self.undobuffer.pop()
-        action = item[0]
-        data = item[1:]
-        if action == "seq":
-            while data:
-                item = data.pop()
-                self._undo(item[0], item[1:])
-        else:
-            self._undo(action, data)
-
-    turtlesize = shapesize
-
-RawPen = RawTurtle
-
-###  Screen - Klasse  ########################
-
-class Screen(TurtleScreen):
-
-    _root = None
-    _canvas = None
-    _title = _CFG["title"]
-
-    # Borg-Idiom
-
-    _shared_state = {}
-
-    def __new__(cls, *args, **kwargs):
-        obj = object.__new__(cls, *args, **kwargs)
-        obj.__dict__ = cls._shared_state
-        return obj
-
-    def __init__(self):
-        if Screen._root is None:
-            Screen._root = self._root = _Root()
-            self._root.title(Screen._title)
-            self._root.ondestroy(self._destroy)
-        if Screen._canvas is None:
-            width = _CFG["width"]
-            height = _CFG["height"]
-            canvwidth = _CFG["canvwidth"]
-            canvheight = _CFG["canvheight"]
-            leftright = _CFG["leftright"]
-            topbottom = _CFG["topbottom"]
-            self._root.setupcanvas(width, height, canvwidth, canvheight)
-            Screen._canvas = self._root._getcanvas()
-            self.setup(width, height, leftright, topbottom)
-            TurtleScreen.__init__(self, Screen._canvas)
-        Turtle._screen = self
-
-    def setup(self, width=_CFG["width"], height=_CFG["height"],
-              startx=_CFG["leftright"], starty=_CFG["topbottom"]):
-        """ Set the size and position of the main window.
-
-        Arguments:
-        width: as integer a size in pixels, as float a fraction of the screen.
-          Default is 50% of screen.
-        height: as integer the height in pixels, as float a fraction of the
-          screen. Default is 75% of screen.
-        startx: if positive, starting position in pixels from the left
-          edge of the screen, if negative from the right edge
-          Default, startx=None is to center window horizontally.
-        starty: if positive, starting position in pixels from the top
-          edge of the screen, if negative from the bottom edge
-          Default, starty=None is to center window vertically.
-
-        Examples (for a Screen instance named screen):
-        >>> screen.setup (width=200, height=200, startx=0, starty=0)
-
-        sets window to 200x200 pixels, in upper left of screen
-
-        >>> screen.setup(width=.75, height=0.5, startx=None, starty=None)
-
-        sets window to 75% of screen by 50% of screen and centers
-        """
-        if not hasattr(self._root, "set_geometry"):
-            return
-        sw = self._root.win_width()
-        sh = self._root.win_height()
-        if isinstance(width, float) and 0 <= width <= 1:
-            width = sw*width
-        if startx is None:
-            startx = (sw - width) / 2
-        if isinstance(height, float) and 0 <= height <= 1:
-            height = sh*height
-        if starty is None:
-            starty = (sh - height) / 2
-        self._root.set_geometry(width, height, startx, starty)
-
-    def title(self, titlestring):
-        """Set title of turtle-window
-
-        Argument:
-        titlestring -- a string, to appear in the titlebar of the
-                       turtle graphics window.
-
-        This is a method of Screen-class. Not available for TurtleScreen-
-        objects.
-
-        Example (for a Screen instance named screen):
-        >>> screen.title("Welcome to the turtle-zoo!")
-        """
-        if Screen._root is not None:
-            Screen._root.title(titlestring)
-        Screen._title = titlestring
-
-    def _destroy(self):
-        root = self._root
-        if root is Screen._root:
-            Turtle._pen = None
-            Turtle._screen = None
-            Screen._root = None
-            Screen._canvas = None
-        TurtleScreen._RUNNING = True
-        root.destroy()
-
-    def bye(self):
-        """Shut the turtlegraphics window.
-
-        Example (for a TurtleScreen instance named screen):
-        >>> screen.bye()
-        """
-        self._destroy()
-
-    def exitonclick(self):
-        """Go into mainloop until the mouse is clicked.
-
-        No arguments.
-
-        Bind bye() method to mouseclick on TurtleScreen.
-        If "using_IDLE" - value in configuration dictionary is False
-        (default value), enter mainloop.
-        If IDLE with -n switch (no subprocess) is used, this value should be
-        set to True in turtle.cfg. In this case IDLE's mainloop
-        is active also for the client script.
-
-        This is a method of the Screen-class and not available for
-        TurtleScreen instances.
-
-        Example (for a Screen instance named screen):
-        >>> screen.exitonclick()
-
-        """
-        def exitGracefully(x, y):
-            """Screen.bye() with two dummy-parameters"""
-            self.bye()
-        self.onclick(exitGracefully)
-        if _CFG["using_IDLE"]:
-            return
-        try:
-            mainloop()
-        except AttributeError:
-            exit(0)
-
-
-class Turtle(RawTurtle):
-    """RawTurtle auto-crating (scrolled) canvas.
-
-    When a Turtle object is created or a function derived from some
-    Turtle method is called a TurtleScreen object is automatically created.
-    """
-    _pen = None
-    _screen = None
-
-    def __init__(self,
-                 shape=_CFG["shape"],
-                 undobuffersize=_CFG["undobuffersize"],
-                 visible=_CFG["visible"]):
-        if Turtle._screen is None:
-            Turtle._screen = Screen()
-        RawTurtle.__init__(self, Turtle._screen,
-                           shape=shape,
-                           undobuffersize=undobuffersize,
-                           visible=visible)
-
-Pen = Turtle
-
-def _getpen():
-    """Create the 'anonymous' turtle if not already present."""
-    if Turtle._pen is None:
-        Turtle._pen = Turtle()
-    return Turtle._pen
-
-def _getscreen():
-    """Create a TurtleScreen if not already present."""
-    if Turtle._screen is None:
-        Turtle._screen = Screen()
-    return Turtle._screen
-
-def write_docstringdict(filename="turtle_docstringdict"):
-    """Create and write docstring-dictionary to file.
-
-    Optional argument:
-    filename -- a string, used as filename
-                default value is turtle_docstringdict
-
-    Has to be called explicitely, (not used by the turtle-graphics classes)
-    The docstring dictionary will be written to the Python script <filname>.py
-    It is intended to serve as a template for translation of the docstrings
-    into different languages.
-    """
-    docsdict = {}
-
-    for methodname in _tg_screen_functions:
-        key = "Screen."+methodname
-        docsdict[key] = eval(key).__doc__
-    for methodname in _tg_turtle_functions:
-        key = "Turtle."+methodname
-        docsdict[key] = eval(key).__doc__
-
-    f = open("%s.py" % filename,"w")
-    keys = sorted([x for x in docsdict.keys()
-                        if x.split('.')[1] not in _alias_list])
-    f.write('docsdict = {\n\n')
-    for key in keys[:-1]:
-        f.write('%s :\n' % repr(key))
-        f.write('        """%s\n""",\n\n' % docsdict[key])
-    key = keys[-1]
-    f.write('%s :\n' % repr(key))
-    f.write('        """%s\n"""\n\n' % docsdict[key])
-    f.write("}\n")
-    f.close()
-
-def read_docstrings(lang):
-    """Read in docstrings from lang-specific docstring dictionary.
-
-    Transfer docstrings, translated to lang, from a dictionary-file
-    to the methods of classes Screen and Turtle and - in revised form -
-    to the corresponding functions.
-    """
-    modname = "turtle_docstringdict_%(language)s" % {'language':lang.lower()}
-    module = __import__(modname)
-    docsdict = module.docsdict
-    for key in docsdict:
-        try:
-#            eval(key).im_func.__doc__ = docsdict[key]
-            eval(key).__doc__ = docsdict[key]
-        except:
-            print("Bad docstring-entry: %s" % key)
-
-_LANGUAGE = _CFG["language"]
-
-try:
-    if _LANGUAGE != "english":
-        read_docstrings(_LANGUAGE)
-except ImportError:
-    print("Cannot find docsdict for", _LANGUAGE)
-except:
-    print ("Unknown Error when trying to import %s-docstring-dictionary" %
-                                                                  _LANGUAGE)
-
-
-def getmethparlist(ob):
-    "Get strings describing the arguments for the given object"
-    argText1 = argText2 = ""
-    # bit of a hack for methods - turn it into a function
-    # but we drop the "self" param.
-##    if type(ob)==types.MethodType:
-##       fob = ob.im_func
-##        argOffset = 1
-##    else:
-##        fob = ob
-##        argOffset = 0
-    # Try and build one for Python defined functions
-    argOffset = 1
-##    if type(fob) in [types.FunctionType, types.LambdaType]:
-##        try:
-    counter = ob.__code__.co_argcount
-    items2 = list(ob.__code__.co_varnames[argOffset:counter])
-    realArgs = ob.__code__.co_varnames[argOffset:counter]
-    defaults = ob.__defaults__ or []
-    defaults = list(map(lambda name: "=%s" % repr(name), defaults))
-    defaults = [""] * (len(realArgs)-len(defaults)) + defaults
-    items1 = list(map(lambda arg, dflt: arg+dflt, realArgs, defaults))
-    if ob.__code__.co_flags & 0x4:
-        items1.append("*"+ob.__code__.co_varnames[counter])
-        items2.append("*"+ob.__code__.co_varnames[counter])
-        counter += 1
-    if ob.__code__.co_flags & 0x8:
-        items1.append("**"+ob.__code__.co_varnames[counter])
-        items2.append("**"+ob.__code__.co_varnames[counter])
-    argText1 = ", ".join(items1)
-    argText1 = "(%s)" % argText1
-    argText2 = ", ".join(items2)
-    argText2 = "(%s)" % argText2
-##        except:
-##            pass
-    return argText1, argText2
-
-def _turtle_docrevise(docstr):
-    """To reduce docstrings from RawTurtle class for functions
-    """
-    import re
-    if docstr is None:
-        return None
-    turtlename = _CFG["exampleturtle"]
-    newdocstr = docstr.replace("%s." % turtlename,"")
-    parexp = re.compile(r' \(.+ %s\):' % turtlename)
-    newdocstr = parexp.sub(":", newdocstr)
-    return newdocstr
-
-def _screen_docrevise(docstr):
-    """To reduce docstrings from TurtleScreen class for functions
-    """
-    import re
-    if docstr is None:
-        return None
-    screenname = _CFG["examplescreen"]
-    newdocstr = docstr.replace("%s." % screenname,"")
-    parexp = re.compile(r' \(.+ %s\):' % screenname)
-    newdocstr = parexp.sub(":", newdocstr)
-    return newdocstr
-
-## The following mechanism makes all methods of RawTurtle and Turtle available
-## as functions. So we can enhance, change, add, delete methods to these
-## classes and do not need to change anything here.
-
-
-for methodname in _tg_screen_functions:
-    pl1, pl2 = getmethparlist(eval('Screen.' + methodname))
-    if pl1 == "":
-        print(">>>>>>", pl1, pl2)
-        continue
-    defstr = ("def %(key)s%(pl1)s: return _getscreen().%(key)s%(pl2)s" %
-                                   {'key':methodname, 'pl1':pl1, 'pl2':pl2})
-##    print("Screen:", defstr)
-    exec(defstr)
-    eval(methodname).__doc__ = _screen_docrevise(eval('Screen.'+methodname).__doc__)
-
-for methodname in _tg_turtle_functions:
-    pl1, pl2 = getmethparlist(eval('Turtle.' + methodname))
-    if pl1 == "":
-        print(">>>>>>", pl1, pl2)
-        continue
-    defstr = ("def %(key)s%(pl1)s: return _getpen().%(key)s%(pl2)s" %
-                                   {'key':methodname, 'pl1':pl1, 'pl2':pl2})
-##    print("Turtle:", defstr)
-    exec(defstr)
-    eval(methodname).__doc__ = _turtle_docrevise(eval('Turtle.'+methodname).__doc__)
-
-
-done = mainloop = TK.mainloop
-#del pl1, pl2, defstr
-
-if __name__ == "__main__":
-    def switchpen():
-        if isdown():
-            pu()
-        else:
-            pd()
-
-    def demo1():
-        """Demo of old turtle.py - module"""
-        reset()
-        tracer(True)
-        up()
-        backward(100)
-        down()
-        # draw 3 squares; the last filled
-        width(3)
-        for i in range(3):
-            if i == 2:
-                begin_fill()
-            for _ in range(4):
-                forward(20)
-                left(90)
-            if i == 2:
-                color("maroon")
-                end_fill()
-            up()
-            forward(30)
-            down()
-        width(1)
-        color("black")
-        # move out of the way
-        tracer(False)
-        up()
-        right(90)
-        forward(100)
-        right(90)
-        forward(100)
-        right(180)
-        down()
-        # some text
-        write("startstart", 1)
-        write("start", 1)
-        color("red")
-        # staircase
-        for i in range(5):
-            forward(20)
-            left(90)
-            forward(20)
-            right(90)
-        # filled staircase
-        tracer(True)
-        begin_fill()
-        for i in range(5):
-            forward(20)
-            left(90)
-            forward(20)
-            right(90)
-        end_fill()
-        # more text
-
-    def demo2():
-        """Demo of some new features."""
-        speed(1)
-        st()
-        pensize(3)
-        setheading(towards(0, 0))
-        radius = distance(0, 0)/2.0
-        rt(90)
-        for _ in range(18):
-            switchpen()
-            circle(radius, 10)
-        write("wait a moment...")
-        while undobufferentries():
-            undo()
-        reset()
-        lt(90)
-        colormode(255)
-        laenge = 10
-        pencolor("green")
-        pensize(3)
-        lt(180)
-        for i in range(-2, 16):
-            if i > 0:
-                begin_fill()
-                fillcolor(255-15*i, 0, 15*i)
-            for _ in range(3):
-                fd(laenge)
-                lt(120)
-            end_fill()
-            laenge += 10
-            lt(15)
-            speed((speed()+1)%12)
-        #end_fill()
-
-        lt(120)
-        pu()
-        fd(70)
-        rt(30)
-        pd()
-        color("red","yellow")
-        speed(0)
-        begin_fill()
-        for _ in range(4):
-            circle(50, 90)
-            rt(90)
-            fd(30)
-            rt(90)
-        end_fill()
-        lt(90)
-        pu()
-        fd(30)
-        pd()
-        shape("turtle")
-
-        tri = getturtle()
-        tri.resizemode("auto")
-        turtle = Turtle()
-        turtle.resizemode("auto")
-        turtle.shape("turtle")
-        turtle.reset()
-        turtle.left(90)
-        turtle.speed(0)
-        turtle.up()
-        turtle.goto(280, 40)
-        turtle.lt(30)
-        turtle.down()
-        turtle.speed(6)
-        turtle.color("blue","orange")
-        turtle.pensize(2)
-        tri.speed(6)
-        setheading(towards(turtle))
-        count = 1
-        while tri.distance(turtle) > 4:
-            turtle.fd(3.5)
-            turtle.lt(0.6)
-            tri.setheading(tri.towards(turtle))
-            tri.fd(4)
-            if count % 20 == 0:
-                turtle.stamp()
-                tri.stamp()
-                switchpen()
-            count += 1
-        tri.write("CAUGHT! ", font=("Arial", 16, "bold"), align="right")
-        tri.pencolor("black")
-        tri.pencolor("red")
-
-        def baba(xdummy, ydummy):
-            clearscreen()
-            bye()
-
-        time.sleep(2)
-
-        while undobufferentries():
-            tri.undo()
-            turtle.undo()
-        tri.fd(50)
-        tri.write("  Click me!", font = ("Courier", 12, "bold") )
-        tri.onclick(baba, 1)
-
-    demo1()
-    demo2()
-    exitonclick()