Author: martin.v.loewis Date: Tue Sep 30 00:09:07 2008 New Revision: 66686 Log: Issue #3965: Allow repeated calls to turtle.Screen, by making it a true singleton object. Reviewed by Gregor Lingl. Modified: python/trunk/Demo/turtle/turtleDemo.py python/trunk/Doc/library/turtle.rst python/trunk/Lib/lib-tk/turtle.py python/trunk/Misc/NEWS Modified: python/trunk/Demo/turtle/turtleDemo.py ============================================================================== --- python/trunk/Demo/turtle/turtleDemo.py (original) +++ python/trunk/Demo/turtle/turtleDemo.py Tue Sep 30 00:09:07 2008 @@ -94,8 +94,8 @@ left_frame.pack(side=LEFT, fill=BOTH, expand=0) self.graph_frame = g_frame = Frame(root) - turtle.Screen._root = g_frame - turtle.Screen._canvas = turtle.ScrolledCanvas(g_frame, 800, 600, 1000, 800) + turtle._Screen._root = g_frame + turtle._Screen._canvas = turtle.ScrolledCanvas(g_frame, 800, 600, 1000, 800) #xturtle.Screen._canvas.pack(expand=1, fill="both") self.screen = _s_ = turtle.Screen() self.scanvas = _s_._canvas Modified: python/trunk/Doc/library/turtle.rst ============================================================================== --- python/trunk/Doc/library/turtle.rst (original) +++ python/trunk/Doc/library/turtle.rst Tue Sep 30 00:09:07 2008 @@ -40,10 +40,10 @@ :class:`ScrolledCanvas` as argument. It should be used when :mod:`turtle` is used as part of some application. - Derived from :class:`TurtleScreen` is the subclass :class:`Screen`. Screen - is implemented as sort of singleton, so there can exist only one instance of - Screen at a time. It should be used when :mod:`turtle` is used as a - standalone tool for doing graphics. + The function :func:`Screen` returns a singleton object of a + :class:`TurtleScreen` subclass. This function should be used when + :mod:`turtle` is used as a standalone tool for doing graphics. + As a singleton object, inheriting from its class is not possible. All methods of TurtleScreen/Screen also exist as functions, i.e. as part of the procedure-oriented interface. Modified: python/trunk/Lib/lib-tk/turtle.py ============================================================================== --- python/trunk/Lib/lib-tk/turtle.py (original) +++ python/trunk/Lib/lib-tk/turtle.py Tue Sep 30 00:09:07 2008 @@ -2422,7 +2422,7 @@ shape=_CFG["shape"], undobuffersize=_CFG["undobuffersize"], visible=_CFG["visible"]): - if isinstance(canvas, Screen): + if isinstance(canvas, _Screen): self.screen = canvas elif isinstance(canvas, TurtleScreen): if canvas not in RawTurtle.screens: @@ -3539,29 +3539,33 @@ RawPen = RawTurtle -### Screen - Klasse ######################## +### Screen - Singleton ######################## -class Screen(TurtleScreen): +def Screen(): + """Return the singleton screen object. + If none exists at the moment, create a new one and return it, + else return the existing one.""" + if Turtle._screen is None: + Turtle._screen = _Screen() + return Turtle._screen + +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) + # XXX there is no need for this code to be conditional, + # as there will be only a single _Screen instance, anyway + # XXX actually, the turtle demo is injecting root window, + # so perhaps the conditional creation of a root should be + # preserved (perhaps by passing it as an optional parameter) + 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: + if _Screen._canvas is None: width = _CFG["width"] height = _CFG["height"] canvwidth = _CFG["canvwidth"] @@ -3569,10 +3573,9 @@ leftright = _CFG["leftright"] topbottom = _CFG["topbottom"] self._root.setupcanvas(width, height, canvwidth, canvheight) - Screen._canvas = self._root._getcanvas() + _Screen._canvas = self._root._getcanvas() self.setup(width, height, leftright, topbottom) - TurtleScreen.__init__(self, Screen._canvas) - Turtle._screen = self + TurtleScreen.__init__(self, _Screen._canvas) def setup(self, width=_CFG["width"], height=_CFG["height"], startx=_CFG["leftright"], starty=_CFG["topbottom"]): @@ -3626,17 +3629,17 @@ 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 + if _Screen._root is not None: + _Screen._root.title(titlestring) + _Screen._title = titlestring def _destroy(self): root = self._root - if root is Screen._root: + if root is _Screen._root: Turtle._pen = None Turtle._screen = None - Screen._root = None - Screen._canvas = None + _Screen._root = None + _Screen._canvas = None TurtleScreen._RUNNING = True root.destroy() @@ -3728,7 +3731,7 @@ docsdict = {} for methodname in _tg_screen_functions: - key = "Screen."+methodname + key = "_Screen."+methodname docsdict[key] = eval(key).__doc__ for methodname in _tg_turtle_functions: key = "Turtle."+methodname @@ -3842,14 +3845,14 @@ for methodname in _tg_screen_functions: - pl1, pl2 = getmethparlist(eval('Screen.' + methodname)) + 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}) exec defstr - eval(methodname).__doc__ = _screen_docrevise(eval('Screen.'+methodname).__doc__) + eval(methodname).__doc__ = _screen_docrevise(eval('_Screen.'+methodname).__doc__) for methodname in _tg_turtle_functions: pl1, pl2 = getmethparlist(eval('Turtle.' + methodname)) Modified: python/trunk/Misc/NEWS ============================================================================== --- python/trunk/Misc/NEWS (original) +++ python/trunk/Misc/NEWS Tue Sep 30 00:09:07 2008 @@ -23,6 +23,9 @@ Library ------- +- Issue #3965: Allow repeated calls to turtle.Screen, by making it a + true singleton object. + - Issue #3895: It was possible to crash the interpreter when an external timer was used with cProfile that returned an object that could not be converted into a float.