text: # TODO:
  # * Loop Delay is broken on GTKAgg. This is because source_remove() is not
  #   working as we want. PyGTK bug?
  # * Documentation -- this will need a new section of the User's Guide.
  #      Both for Animations and just timers.
  #   - Also need to update http://www.scipy.org/Cookbook/Matplotlib/Animations
  # * Blit
  #   * Currently broken with Qt4 for widgets that don't start on screen
  #   * Still a few edge cases that aren't working correctly
  #   * Can this integrate better with existing matplotlib animation artist flag?
  #     - If animated removes from default draw(), perhaps we could use this to
  #       simplify initial draw.
  # * Example
  #   * Frameless animation - pure procedural with no loop
  #   * Need example that uses something like inotify or subprocess
  #   * Complex syncing examples
  # * Movies
  #   * Can blit be enabled for movies?
  # * Need to consider event sources to allow clicking through multiple figures
  from __future__ import (absolute_import, division, print_function,
                          unicode_literals)
  
  import six
  from six.moves import xrange, zip
  
  import platform
  import sys
  import itertools
  import contextlib
  from matplotlib.cbook import iterable, is_string_like
  from matplotlib.compat import subprocess
  from matplotlib import verbose
  from matplotlib import rcParams
  
  # Process creation flag for subprocess to prevent it raising a terminal
  # window. See for example:
  # https://stackoverflow.com/questions/24130623/using-python-subprocess-popen-cant-prevent-exe-stopped-working-prompt
  if platform.system() == 'Windows':
      CREATE_NO_WINDOW = 0x08000000
      subprocess_creation_flags = CREATE_NO_WINDOW
  else:
      # Apparently None won't work here
      subprocess_creation_flags = 0
  
  # Other potential writing methods:
  # * http://pymedia.org/
  # * libmng (produces swf) python wrappers: https://github.com/libming/libming
  # * Wrap x264 API:
  
  # (http://stackoverflow.com/questions/2940671/
  # how-to-encode-series-of-images-into-h264-using-x264-api-c-c )
  
  
  # A registry for available MovieWriter classes
  class MovieWriterRegistry(object):
      def __init__(self):
          self.avail = dict()
  
      # Returns a decorator that can be used on classes to register them under
      # a name. As in:
      # @register('foo')
      # class Foo:
      #    pass
      def register(self, name):
          def wrapper(writerClass):
              if writerClass.isAvailable():
                  self.avail[name] = writerClass
              return writerClass
          return wrapper
  
      def list(self):
          ''' Get a list of available MovieWriters.'''
          return list(self.avail.keys())
  
      def is_available(self, name):
          return name in self.avail
  
      def __getitem__(self, name):
          if not self.avail:
              raise RuntimeError("No MovieWriters available!")
          return self.avail[name]
  
  writers = MovieWriterRegistry()
  
  
  class MovieWriter(object):
      '''
      Base class for writing movies. Fundamentally, what a MovieWriter does
      is provide is a way to grab frames by calling grab_frame(). setup()
      is called to start the process and finish() is called afterwards.
      This class is set up to provide for writing movie frame data to a pipe.
      saving() is provided as a context manager to facilitate this process as::
  
        with moviewriter.saving('myfile.mp4'):
            # Iterate over frames
            moviewriter.grab_frame()
  
      The use of the context manager ensures that setup and cleanup are
      performed as necessary.
  
      frame_format: string
          The format used in writing frame data, defaults to 'rgba'
      '''
      def __init__(self, fps=5, codec=None, bitrate=None, extra_args=None,
                   metadata=None):
          '''
          Construct a new MovieWriter object.
  
          fps: int
              Framerate for movie.
          codec: string or None, optional
              The codec to use. If None (the default) the setting in the
              rcParam `animation.codec` is used.
          bitrate: int or None, optional
              The bitrate for the saved movie file, which is one way to control
              the output file size and quality. The default value is None,
              which uses the value stored in the rcParam `animation.bitrate`.
              A value of -1 implies that the bitrate should be determined
              automatically by the underlying utility.
          extra_args: list of strings or None
              A list of extra string arguments to be passed to the underlying
              movie utiltiy. The default is None, which passes the additional
              argurments in the 'animation.extra_args' rcParam.
          metadata: dict of string:string or None
              A dictionary of keys and values for metadata to include in the
              output file. Some keys that may be of use include:
              title, artist, genre, subject, copyright, srcform, comment.
          '''
          self.fps = fps
          self.frame_format = 'rgba'
  
          if codec is None:
              self.codec = rcParams['animation.codec']
          else:
              self.codec = codec
  
          if bitrate is None:
              self.bitrate = rcParams['animation.bitrate']
          else:
              self.bitrate = bitrate
  
          if extra_args is None:
              self.extra_args = list(rcParams[self.args_key])
          else:
              self.extra_args = extra_args
  
          if metadata is None:
              self.metadata = dict()
          else:
              self.metadata = metadata
  
      @property
      def frame_size(self):
          'A tuple (width,height) in pixels of a movie frame.'
          width_inches, height_inches = self.fig.get_size_inches()
          return width_inches * self.dpi, height_inches * self.dpi
  
      def setup(self, fig, outfile, dpi, *args):
          '''
          Perform setup for writing the movie file.
  
          fig: `matplotlib.Figure` instance
              The figure object that contains the information for frames
          outfile: string
              The filename of the resulting movie file
          dpi: int
              The DPI (or resolution) for the file.  This controls the size
              in pixels of the resulting movie file.
          '''
          self.outfile = outfile
          self.fig = fig
          self.dpi = dpi
  
          # Run here so that grab_frame() can write the data to a pipe. This
          # eliminates the need for temp files.
          self._run()
  
      @contextlib.contextmanager
      def saving(self, *args):
          '''
          Context manager to facilitate writing the movie file.
  
          ``*args`` are any parameters that should be passed to `setup`.
          '''
          # This particular sequence is what contextlib.contextmanager wants
          self.setup(*args)
          yield
          self.finish()
  
      def _run(self):
          # Uses subprocess to call the program for assembling frames into a
          # movie file.  *args* returns the sequence of command line arguments
          # from a few configuration options.
          command = self._args()
          if verbose.ge('debug'):
              output = sys.stdout
          else:
              output = subprocess.PIPE
          verbose.report('MovieWriter.run: running command: %s' %
                         ' '.join(command))
          self._proc = subprocess.Popen(command, shell=False,
                                        stdout=output, stderr=output,
                                        stdin=subprocess.PIPE,
                                        creationflags=subprocess_creation_flags)
  
      def finish(self):
          'Finish any processing for writing the movie.'
          self.cleanup()
  
      def grab_frame(self, **savefig_kwargs):
          '''
          Grab the image information from the figure and save as a movie frame.
          All keyword arguments in savefig_kwargs are passed on to the 'savefig'
          command that saves the figure.
          '''
          verbose.report('MovieWriter.grab_frame: Grabbing frame.',
                         level='debug')
          try:
              # Tell the figure to save its data to the sink, using the
              # frame format and dpi.
              self.fig.savefig(self._frame_sink(), format=self.frame_format,
                               dpi=self.dpi, **savefig_kwargs)
          except RuntimeError:
              out, err = self._proc.communicate()
              verbose.report('MovieWriter -- Error '
                             'running proc:\n%s\n%s' % (out,
                                                        err), level='helpful')
              raise
  
      def _frame_sink(self):
          'Returns the place to which frames should be written.'
          return self._proc.stdin
  
      def _args(self):
          'Assemble list of utility-specific command-line arguments.'
          return NotImplementedError("args needs to be implemented by subclass.")
  
      def cleanup(self):
          'Clean-up and collect the process used to write the movie file.'
          out, err = self._proc.communicate()
          verbose.report('MovieWriter -- '
                         'Command stdout:\n%s' % out, level='debug')
          verbose.report('MovieWriter -- '
                         'Command stderr:\n%s' % err, level='debug')
  
      @classmethod
      def bin_path(cls):
          '''
          Returns the binary path to the commandline tool used by a specific
          subclass. This is a class method so that the tool can be looked for
          before making a particular MovieWriter subclass available.
          '''
          return rcParams[cls.exec_key]
  
      @classmethod
      def isAvailable(cls):
          '''
          Check to see if a MovieWriter subclass is actually available by
          running the commandline tool.
          '''
          try:
              p = subprocess.Popen(cls.bin_path(),
                               shell=False,
                               stdout=subprocess.PIPE,
                               stderr=subprocess.PIPE,
                               creationflags=subprocess_creation_flags)
              p.communicate()
              return True
          except OSError:
              return False
  
  
  class FileMovieWriter(MovieWriter):
      '`MovieWriter` subclass that handles writing to a file.'
      def __init__(self, *args, **kwargs):
          MovieWriter.__init__(self, *args, **kwargs)
          self.frame_format = rcParams['animation.frame_format']
  
      def setup(self, fig, outfile, dpi, frame_prefix='_tmp', clear_temp=True):
          '''
          Perform setup for writing the movie file.
  
          fig: `matplotlib.Figure` instance
              The figure object that contains the information for frames
          outfile: string
              The filename of the resulting movie file
          dpi: int
              The DPI (or resolution) for the file.  This controls the size
              in pixels of the resulting movie file.
          frame_prefix: string, optional
              The filename prefix to use for the temporary files. Defaults
              to '_tmp'
          clear_temp: bool
              Specifies whether the temporary files should be deleted after
              the movie is written. (Useful for debugging.) Defaults to True.
          '''
          self.fig = fig
          self.outfile = outfile
          self.dpi = dpi
          self.clear_temp = clear_temp
          self.temp_prefix = frame_prefix
          self._frame_counter = 0  # used for generating sequential file names
          self._temp_names = list()
          self.fname_format_str = '%s%%07d.%s'
  
      @property
      def frame_format(self):
          '''
          Format (png, jpeg, etc.) to use for saving the frames, which can be
          decided by the individual subclasses.
          '''
          return self._frame_format
  
      @frame_format.setter
      def frame_format(self, frame_format):
          if frame_format in self.supported_formats:
              self._frame_format = frame_format
          else:
              self._frame_format = self.supported_formats[0]
  
      def _base_temp_name(self):
          # Generates a template name (without number) given the frame format
          # for extension and the prefix.
          return self.fname_format_str % (self.temp_prefix, self.frame_format)
  
      def _frame_sink(self):
          # Creates a filename for saving using the basename and the current
          # counter.
          fname = self._base_temp_name() % self._frame_counter
  
          # Save the filename so we can delete it later if necessary
          self._temp_names.append(fname)
          verbose.report(
              'FileMovieWriter.frame_sink: saving frame %d to fname=%s' %
              (self._frame_counter, fname),
              level='debug')
          self._frame_counter += 1  # Ensures each created name is 'unique'
  
          # This file returned here will be closed once it's used by savefig()
          # because it will no longer be referenced and will be gc-ed.
          return open(fname, 'wb')
  
      def grab_frame(self, **savefig_kwargs):
          '''
          Grab the image information from the figure and save as a movie frame.
          All keyword arguments in savefig_kwargs are passed on to the 'savefig'
          command that saves the figure.
          '''
          # Overloaded to explicitly close temp file.
          verbose.report('MovieWriter.grab_frame: Grabbing frame.',
                         level='debug')
          try:
              # Tell the figure to save its data to the sink, using the
              # frame format and dpi.
              myframesink = self._frame_sink()
              self.fig.savefig(myframesink, format=self.frame_format,
                               dpi=self.dpi, **savefig_kwargs)
              myframesink.close()
  
          except RuntimeError:
              out, err = self._proc.communicate()
              verbose.report('MovieWriter -- Error '
                             'running proc:\n%s\n%s' % (out,
                                                        err), level='helpful')
              raise
  
      def finish(self):
          # Call run here now that all frame grabbing is done. All temp files
          # are available to be assembled.
          self._run()
          MovieWriter.finish(self)  # Will call clean-up
  
          # Check error code for creating file here, since we just run
          # the process here, rather than having an open pipe.
          if self._proc.returncode:
              raise RuntimeError('Error creating movie, return code: '
                                 + str(self._proc.returncode)
                                 + ' Try running with --verbose-debug')
  
      def cleanup(self):
          MovieWriter.cleanup(self)
  
          # Delete temporary files
          if self.clear_temp:
              import os
              verbose.report(
                  'MovieWriter: clearing temporary fnames=%s' %
                  str(self._temp_names),
                  level='debug')
              for fname in self._temp_names:
                  os.remove(fname)
  
  
  # Base class of ffmpeg information. Has the config keys and the common set
  # of arguments that controls the *output* side of things.
  class FFMpegBase:
      exec_key = 'animation.ffmpeg_path'
      args_key = 'animation.ffmpeg_args'
  
      @property
      def output_args(self):
          # The %dk adds 'k' as a suffix so that ffmpeg treats our bitrate as in
          # kbps
          args = ['-vcodec', self.codec]
          if self.bitrate > 0:
              args.extend(['-b', '%dk' % self.bitrate])
          if self.extra_args:
              args.extend(self.extra_args)
          for k, v in six.iteritems(self.metadata):
              args.extend(['-metadata', '%s=%s' % (k, v)])
  
          return args + ['-y', self.outfile]
  
  
  # Combine FFMpeg options with pipe-based writing
  @writers.register('ffmpeg')
  class FFMpegWriter(MovieWriter, FFMpegBase):
      def _args(self):
          # Returns the command line parameters for subprocess to use
          # ffmpeg to create a movie using a pipe.
          args = [self.bin_path(), '-f', 'rawvideo', '-vcodec', 'rawvideo',
                  '-s', '%dx%d' % self.frame_size, '-pix_fmt', self.frame_format,
                  '-r', str(self.fps)]
          # Logging is quieted because subprocess.PIPE has limited buffer size.
          if not verbose.ge('debug'):
              args += ['-loglevel', 'quiet']
          args += ['-i', 'pipe:'] + self.output_args
          return args
  
  
  # Combine FFMpeg options with temp file-based writing
  @writers.register('ffmpeg_file')
  class FFMpegFileWriter(FileMovieWriter, FFMpegBase):
      supported_formats = ['png', 'jpeg', 'ppm', 'tiff', 'sgi', 'bmp',
                           'pbm', 'raw', 'rgba']
  
      def _args(self):
          # Returns the command line parameters for subprocess to use
          # ffmpeg to create a movie using a collection of temp images
          return [self.bin_path(), '-i', self._base_temp_name(),
                  '-vframes', str(self._frame_counter),
                  '-r', str(self.fps)] + self.output_args
  
  
  # Base class of avconv information.  AVConv has identical arguments to
  # FFMpeg
  class AVConvBase(FFMpegBase):
      exec_key = 'animation.avconv_path'
      args_key = 'animation.avconv_args'
  
  
  # Combine AVConv options with pipe-based writing
  @writers.register('avconv')
  class AVConvWriter(AVConvBase, FFMpegWriter):
      pass
  
  
  # Combine AVConv options with file-based writing
  @writers.register('avconv_file')
  class AVConvFileWriter(AVConvBase, FFMpegFileWriter):
      pass
  
  
  # Base class of mencoder information. Contains configuration key information
  # as well as arguments for controlling *output*
  class MencoderBase:
      exec_key = 'animation.mencoder_path'
      args_key = 'animation.mencoder_args'
  
      # Mencoder only allows certain keys, other ones cause the program
      # to fail.
      allowed_metadata = ['name', 'artist', 'genre', 'subject', 'copyright',
                          'srcform', 'comment']
  
      # Mencoder mandates using name, but 'title' works better with ffmpeg.
      # If we find it, just put it's value into name
      def _remap_metadata(self):
          if 'title' in self.metadata:
              self.metadata['name'] = self.metadata['title']
  
      @property
      def output_args(self):
          self._remap_metadata()
          lavcopts = {'vcodec': self.codec}
          if self.bitrate > 0:
              lavcopts.update(vbitrate=self.bitrate)
          args = ['-o', self.outfile, '-ovc', 'lavc', '-lavcopts',
                  ':'.join(itertools.starmap('{0}={1}'.format,
                                             lavcopts.items()))]
          if self.extra_args:
              args.extend(self.extra_args)
          if self.metadata:
              args.extend(['-info', ':'.join('%s=%s' % (k, v)
                           for k, v in six.iteritems(self.metadata)
                           if k in self.allowed_metadata)])
          return args
  
  
  # Combine Mencoder options with pipe-based writing
  @writers.register('mencoder')
  class MencoderWriter(MovieWriter, MencoderBase):
      def _args(self):
          # Returns the command line parameters for subprocess to use
          # mencoder to create a movie
          return [self.bin_path(), '-', '-demuxer', 'rawvideo', '-rawvideo',
                  ('w=%i:h=%i:' % self.frame_size +
                  'fps=%i:format=%s' % (self.fps,
                                        self.frame_format))] + self.output_args
  
  
  # Combine Mencoder options with temp file-based writing
  @writers.register('mencoder_file')
  class MencoderFileWriter(FileMovieWriter, MencoderBase):
      supported_formats = ['png', 'jpeg', 'tga', 'sgi']
  
      def _args(self):
          # Returns the command line parameters for subprocess to use
          # mencoder to create a movie
          return [self.bin_path(),
                  'mf://%s*.%s' % (self.temp_prefix, self.frame_format),
                  '-frames', str(self._frame_counter), '-mf',
                  'type=%s:fps=%d' % (self.frame_format,
                                      self.fps)] + self.output_args
  
  
  # Base class for animated GIFs with convert utility
  class ImageMagickBase:
      exec_key = 'animation.convert_path'
      args_key = 'animation.convert_args'
  
      @property
      def delay(self):
          return 100. / self.fps
  
      @property
      def output_args(self):
          return [self.outfile]
  
  
  @writers.register('imagemagick')
  class ImageMagickWriter(MovieWriter, ImageMagickBase):
      def _args(self):
          return ([self.bin_path(),
                   '-size', '%ix%i' % self.frame_size, '-depth', '8',
                   '-delay', str(self.delay), '-loop', '0',
                   '%s:-' % self.frame_format]
                  + self.output_args)
  
  
  @writers.register('imagemagick_file')
  class ImageMagickFileWriter(FileMovieWriter, ImageMagickBase):
      supported_formats = ['png', 'jpeg', 'ppm', 'tiff', 'sgi', 'bmp',
                           'pbm', 'raw', 'rgba']
  
      def _args(self):
          return ([self.bin_path(), '-delay', str(self.delay), '-loop', '0',
                   '%s*.%s' % (self.temp_prefix, self.frame_format)]
                  + self.output_args)
  
  
  class Animation(object):
      '''
      This class wraps the creation of an animation using matplotlib. It is
      only a base class which should be subclassed to provide needed behavior.
  
      *fig* is the figure object that is used to get draw, resize, and any
      other needed events.
  
      *event_source* is a class that can run a callback when desired events
      are generated, as well as be stopped and started. Examples include timers
      (see :class:`TimedAnimation`) and file system notifications.
  
      *blit* is a boolean that controls whether blitting is used to optimize
      drawing.
      '''
      def __init__(self, fig, event_source=None, blit=False):
          self._fig = fig
          # Disables blitting for backends that don't support it.  This
          # allows users to request it if available, but still have a
          # fallback that works if it is not.
          self._blit = blit and fig.canvas.supports_blit
  
          # These are the basics of the animation.  The frame sequence represents
          # information for each frame of the animation and depends on how the
          # drawing is handled by the subclasses. The event source fires events
          # that cause the frame sequence to be iterated.
          self.frame_seq = self.new_frame_seq()
          self.event_source = event_source
  
          # Clear the initial frame
          self._init_draw()
  
          # Instead of starting the event source now, we connect to the figure's
          # draw_event, so that we only start once the figure has been drawn.
          self._first_draw_id = fig.canvas.mpl_connect('draw_event', self._start)
  
          # Connect to the figure's close_event so that we don't continue to
          # fire events and try to draw to a deleted figure.
          self._close_id = self._fig.canvas.mpl_connect('close_event',
                                                        self._stop)
          if self._blit:
              self._setup_blit()
  
      def _start(self, *args):
          '''
          Starts interactive animation. Adds the draw frame command to the GUI
          handler, calls show to start the event loop.
          '''
          # On start, we add our callback for stepping the animation and
          # actually start the event_source. We also disconnect _start
          # from the draw_events
          self.event_source.add_callback(self._step)
          self.event_source.start()
          self._fig.canvas.mpl_disconnect(self._first_draw_id)
          self._first_draw_id = None  # So we can check on save
  
      def _stop(self, *args):
          # On stop we disconnect all of our events.
          if self._blit:
              self._fig.canvas.mpl_disconnect(self._resize_id)
          self._fig.canvas.mpl_disconnect(self._close_id)
          self.event_source.remove_callback(self._step)
          self.event_source = None
  
      def save(self, filename, writer=None, fps=None, dpi=None, codec=None,
               bitrate=None, extra_args=None, metadata=None, extra_anim=None,
               savefig_kwargs=None):
          '''
          Saves a movie file by drawing every frame.
  
          *filename* is the output filename, e.g., :file:`mymovie.mp4`
  
          *writer* is either an instance of :class:`MovieWriter` or a string
          key that identifies a class to use, such as 'ffmpeg' or 'mencoder'.
          If nothing is passed, the value of the rcparam `animation.writer` is
          used.
  
          *fps* is the frames per second in the movie. Defaults to None,
          which will use the animation's specified interval to set the frames
          per second.
  
          *dpi* controls the dots per inch for the movie frames. This combined
          with the figure's size in inches controls the size of the movie.
  
          *codec* is the video codec to be used. Not all codecs are supported
          by a given :class:`MovieWriter`. If none is given, this defaults to the
          value specified by the rcparam `animation.codec`.
  
          *bitrate* specifies the amount of bits used per second in the
          compressed movie, in kilobits per second. A higher number means a
          higher quality movie, but at the cost of increased file size. If no
          value is given, this defaults to the value given by the rcparam
          `animation.bitrate`.
  
          *extra_args* is a list of extra string arguments to be passed to the
          underlying movie utiltiy. The default is None, which passes the
          additional argurments in the 'animation.extra_args' rcParam.
  
          *metadata* is a dictionary of keys and values for metadata to include
          in the output file. Some keys that may be of use include:
          title, artist, genre, subject, copyright, srcform, comment.
  
          *extra_anim* is a list of additional `Animation` objects that should
          be included in the saved movie file. These need to be from the same
          `matplotlib.Figure` instance. Also, animation frames will just be
          simply combined, so there should be a 1:1 correspondence between
          the frames from the different animations.
  
          *savefig_kwargs* is a dictionary containing keyword arguments to be
          passed on to the 'savefig' command which is called repeatedly to save
          the individual frames. This can be used to set tight bounding boxes,
          for example.
          '''
          if savefig_kwargs is None:
              savefig_kwargs = {}
  
          # FIXME: Using 'bbox_inches' doesn't currently work with
          # writers that pipe the data to the command because this
          # requires a fixed frame size (see Ryan May's reply in this
          # thread: [1]). Thus we drop the 'bbox_inches' argument if it
          # exists in savefig_kwargs.
          #
          # [1] (http://matplotlib.1069221.n5.nabble.com/
          # Animation-class-let-save-accept-kwargs-which-
          # are-passed-on-to-savefig-td39627.html)
          #
          if 'bbox_inches' in savefig_kwargs:
              if not (writer in ['ffmpeg_file', 'mencoder_file'] or
                      isinstance(writer,
                                 (FFMpegFileWriter, MencoderFileWriter))):
                  print("Warning: discarding the 'bbox_inches' argument in "
                        "'savefig_kwargs' as it is only currently supported "
                        "with the writers 'ffmpeg_file' and 'mencoder_file' "
                        "(writer used: "
                        "'{}').".format(
                            writer if isinstance(writer, six.string_types)
                            else writer.__class__.__name__))
                  savefig_kwargs.pop('bbox_inches')
  
          # Need to disconnect the first draw callback, since we'll be doing
          # draws. Otherwise, we'll end up starting the animation.
          if self._first_draw_id is not None:
              self._fig.canvas.mpl_disconnect(self._first_draw_id)
              reconnect_first_draw = True
          else:
              reconnect_first_draw = False
  
          if fps is None and hasattr(self, '_interval'):
              # Convert interval in ms to frames per second
              fps = 1000. / self._interval
  
          # If the writer is None, use the rc param to find the name of the one
          # to use
          if writer is None:
              writer = rcParams['animation.writer']
  
          # Re-use the savefig DPI for ours if none is given
          if dpi is None:
              dpi = rcParams['savefig.dpi']
  
          if codec is None:
              codec = rcParams['animation.codec']
  
          if bitrate is None:
              bitrate = rcParams['animation.bitrate']
  
          all_anim = [self]
          if extra_anim is not None:
              all_anim.extend(anim
                              for anim
                              in extra_anim if anim._fig is self._fig)
  
          # If we have the name of a writer, instantiate an instance of the
          # registered class.
          if is_string_like(writer):
              if writer in writers.avail:
                  writer = writers[writer](fps, codec, bitrate,
                                           extra_args=extra_args,
                                           metadata=metadata)
              else:
                  import warnings
                  warnings.warn("MovieWriter %s unavailable" % writer)
  
                  try:
                      writer = writers[writers.list()[0]](fps, codec, bitrate,
                                                          extra_args=extra_args,
                                                          metadata=metadata)
                  except IndexError:
                      raise ValueError("Cannot save animation: no writers are "
                                       "available. Please install mencoder or "
                                       "ffmpeg to save animations.")
  
          verbose.report('Animation.save using %s' % type(writer),
                         level='helpful')
          # Create a new sequence of frames for saved data. This is different
          # from new_frame_seq() to give the ability to save 'live' generated
          # frame information to be saved later.
          # TODO: Right now, after closing the figure, saving a movie won't work
          # since GUI widgets are gone. Either need to remove extra code to
          # allow for this non-existant use case or find a way to make it work.
          with writer.saving(self._fig, filename, dpi):
              for data in zip(*[a.new_saved_frame_seq()
                                for a in all_anim]):
                  for anim, d in zip(all_anim, data):
                      # TODO: Need to see if turning off blit is really necessary
                      anim._draw_next_frame(d, blit=False)
                  writer.grab_frame(**savefig_kwargs)
  
          # Reconnect signal for first draw if necessary
          if reconnect_first_draw:
              self._first_draw_id = self._fig.canvas.mpl_connect('draw_event',
                                                                 self._start)
  
      def _step(self, *args):
          '''
          Handler for getting events. By default, gets the next frame in the
          sequence and hands the data off to be drawn.
          '''
          # Returns True to indicate that the event source should continue to
          # call _step, until the frame sequence reaches the end of iteration,
          # at which point False will be returned.
          try:
              framedata = next(self.frame_seq)
              self._draw_next_frame(framedata, self._blit)
              return True
          except StopIteration:
              return False
  
      def new_frame_seq(self):
          'Creates a new sequence of frame information.'
          # Default implementation is just an iterator over self._framedata
          return iter(self._framedata)
  
      def new_saved_frame_seq(self):
          'Creates a new sequence of saved/cached frame information.'
          # Default is the same as the regular frame sequence
          return self.new_frame_seq()
  
      def _draw_next_frame(self, framedata, blit):
          # Breaks down the drawing of the next frame into steps of pre- and
          # post- draw, as well as the drawing of the frame itself.
          self._pre_draw(framedata, blit)
          self._draw_frame(framedata)
          self._post_draw(framedata, blit)
  
      def _init_draw(self):
          # Initial draw to clear the frame. Also used by the blitting code
          # when a clean base is required.
          pass
  
      def _pre_draw(self, framedata, blit):
          # Perform any cleaning or whatnot before the drawing of the frame.
          # This default implementation allows blit to clear the frame.
          if blit:
              self._blit_clear(self._drawn_artists, self._blit_cache)
  
      def _draw_frame(self, framedata):
          # Performs actual drawing of the frame.
          raise NotImplementedError('Needs to be implemented by subclasses to'
                                    ' actually make an animation.')
  
      def _post_draw(self, framedata, blit):
          # After the frame is rendered, this handles the actual flushing of
          # the draw, which can be a direct draw_idle() or make use of the
          # blitting.
          if blit and self._drawn_artists:
              self._blit_draw(self._drawn_artists, self._blit_cache)
          else:
              self._fig.canvas.draw_idle()
  
      # The rest of the code in this class is to facilitate easy blitting
      def _blit_draw(self, artists, bg_cache):
          # Handles blitted drawing, which renders only the artists given instead
          # of the entire figure.
          updated_ax = []
          for a in artists:
              # If we haven't cached the background for this axes object, do
              # so now. This might not always be reliable, but it's an attempt
              # to automate the process.
              if a.axes not in bg_cache:
                  bg_cache[a.axes] = a.figure.canvas.copy_from_bbox(a.axes.bbox)
              a.axes.draw_artist(a)
              updated_ax.append(a.axes)
  
          # After rendering all the needed artists, blit each axes individually.
          for ax in set(updated_ax):
              ax.figure.canvas.blit(ax.bbox)
  
      def _blit_clear(self, artists, bg_cache):
          # Get a list of the axes that need clearing from the artists that
          # have been drawn. Grab the appropriate saved background from the
          # cache and restore.
          axes = set(a.axes for a in artists)
          for a in axes:
              a.figure.canvas.restore_region(bg_cache[a])
  
      def _setup_blit(self):
          # Setting up the blit requires: a cache of the background for the
          # axes
          self._blit_cache = dict()
          self._drawn_artists = []
          self._resize_id = self._fig.canvas.mpl_connect('resize_event',
                                                         self._handle_resize)
          self._post_draw(None, self._blit)
  
      def _handle_resize(self, *args):
          # On resize, we need to disable the resize event handling so we don't
          # get too many events. Also stop the animation events, so that
          # we're paused. Reset the cache and re-init. Set up an event handler
          # to catch once the draw has actually taken place.
          self._fig.canvas.mpl_disconnect(self._resize_id)
          self.event_source.stop()
          self._blit_cache.clear()
          self._init_draw()
          self._resize_id = self._fig.canvas.mpl_connect('draw_event',
                                                         self._end_redraw)
  
      def _end_redraw(self, evt):
          # Now that the redraw has happened, do the post draw flushing and
          # blit handling. Then re-enable all of the original events.
          self._post_draw(None, self._blit)
          self.event_source.start()
          self._fig.canvas.mpl_disconnect(self._resize_id)
          self._resize_id = self._fig.canvas.mpl_connect('resize_event',
                                                         self._handle_resize)
  
  
  class TimedAnimation(Animation):
      '''
      :class:`Animation` subclass that supports time-based animation, drawing
      a new frame every *interval* milliseconds.
  
      *repeat* controls whether the animation should repeat when the sequence
      of frames is completed.
  
      *repeat_delay* optionally adds a delay in milliseconds before repeating
      the animation.
      '''
      def __init__(self, fig, interval=200, repeat_delay=None, repeat=True,
                   event_source=None, *args, **kwargs):
          # Store the timing information
          self._interval = interval
          self._repeat_delay = repeat_delay
          self.repeat = repeat
  
          # If we're not given an event source, create a new timer. This permits
          # sharing timers between animation objects for syncing animations.
          if event_source is None:
              event_source = fig.canvas.new_timer()
              event_source.interval = self._interval
  
          Animation.__init__(self, fig, event_source=event_source,
                             *args, **kwargs)
  
      def _step(self, *args):
          '''
          Handler for getting events.
          '''
          # Extends the _step() method for the Animation class.  If
          # Animation._step signals that it reached the end and we want to
          # repeat, we refresh the frame sequence and return True. If
          # _repeat_delay is set, change the event_source's interval to our loop
          # delay and set the callback to one which will then set the interval
          # back.
          still_going = Animation._step(self, *args)
          if not still_going and self.repeat:
              self.frame_seq = self.new_frame_seq()
              if self._repeat_delay:
                  self.event_source.remove_callback(self._step)
                  self.event_source.add_callback(self._loop_delay)
                  self.event_source.interval = self._repeat_delay
                  return True
              else:
                  return Animation._step(self, *args)
          else:
              return still_going
  
      def _stop(self, *args):
          # If we stop in the middle of a loop delay (which is relatively likely
          # given the potential pause here, remove the loop_delay callback as
          # well.
          self.event_source.remove_callback(self._loop_delay)
          Animation._stop(self)
  
      def _loop_delay(self, *args):
          # Reset the interval and change callbacks after the delay.
          self.event_source.remove_callback(self._loop_delay)
          self.event_source.interval = self._interval
          self.event_source.add_callback(self._step)
          Animation._step(self)
  
  
  class ArtistAnimation(TimedAnimation):
      '''
      Before calling this function, all plotting should have taken place
      and the relevant artists saved.
  
      frame_info is a list, with each list entry a collection of artists that
      represent what needs to be enabled on each frame. These will be disabled
      for other frames.
      '''
      def __init__(self, fig, artists, *args, **kwargs):
          # Internal list of artists drawn in the most recent frame.
          self._drawn_artists = []
  
          # Use the list of artists as the framedata, which will be iterated
          # over by the machinery.
          self._framedata = artists
          TimedAnimation.__init__(self, fig, *args, **kwargs)
  
      def _init_draw(self):
          # Make all the artists involved in *any* frame invisible
          axes = []
          for f in self.new_frame_seq():
              for artist in f:
                  artist.set_visible(False)
                  # Assemble a list of unique axes that need flushing
                  if artist.axes not in axes:
                      axes.append(artist.axes)
  
          # Flush the needed axes
          for ax in axes:
              ax.figure.canvas.draw()
  
      def _pre_draw(self, framedata, blit):
          '''
          Clears artists from the last frame.
          '''
          if blit:
              # Let blit handle clearing
              self._blit_clear(self._drawn_artists, self._blit_cache)
          else:
              # Otherwise, make all the artists from the previous frame invisible
              for artist in self._drawn_artists:
                  artist.set_visible(False)
  
      def _draw_frame(self, artists):
          # Save the artists that were passed in as framedata for the other
          # steps (esp. blitting) to use.
          self._drawn_artists = artists
  
          # Make all the artists from the current frame visible
          for artist in artists:
              artist.set_visible(True)
  
  
  class FuncAnimation(TimedAnimation):
      '''
      Makes an animation by repeatedly calling a function *func*, passing in
      (optional) arguments in *fargs*.
  
      *frames* can be a generator, an iterable, or a number of frames.
  
      *init_func* is a function used to draw a clear frame. If not given, the
      results of drawing from the first item in the frames sequence will be
      used. This function will be called once before the first frame.
  
      If blit=True, *func* and *init_func* should return an iterable of
      drawables to clear.
  
      *kwargs* include *repeat*, *repeat_delay*, and *interval*:
      *interval* draws a new frame every *interval* milliseconds.
      *repeat* controls whether the animation should repeat when the sequence
      of frames is completed.
      *repeat_delay* optionally adds a delay in milliseconds before repeating
      the animation.
      '''
      def __init__(self, fig, func, frames=None, init_func=None, fargs=None,
                   save_count=None, **kwargs):
          if fargs:
              self._args = fargs
          else:
              self._args = ()
          self._func = func
  
          # Amount of framedata to keep around for saving movies. This is only
          # used if we don't know how many frames there will be: in the case
          # of no generator or in the case of a callable.
          self.save_count = save_count
  
          # Set up a function that creates a new iterable when needed. If nothing
          # is passed in for frames, just use itertools.count, which will just
          # keep counting from 0. A callable passed in for frames is assumed to
          # be a generator. An iterable will be used as is, and anything else
          # will be treated as a number of frames.
          if frames is None:
              self._iter_gen = itertools.count
          elif six.callable(frames):
              self._iter_gen = frames
          elif iterable(frames):
              self._iter_gen = lambda: iter(frames)
              if hasattr(frames, '__len__'):
                  self.save_count = len(frames)
          else:
              self._iter_gen = lambda: xrange(frames).__iter__()
              self.save_count = frames
  
          # If we're passed in and using the default, set it to 100.
          if self.save_count is None:
              self.save_count = 100
  
          self._init_func = init_func
  
          # Needs to be initialized so the draw functions work without checking
          self._save_seq = []
  
          TimedAnimation.__init__(self, fig, **kwargs)
  
          # Need to reset the saved seq, since right now it will contain data
          # for a single frame from init, which is not what we want.
          self._save_seq = []
  
      def new_frame_seq(self):
          # Use the generating function to generate a new frame sequence
          return self._iter_gen()
  
      def new_saved_frame_seq(self):
          # Generate an iterator for the sequence of saved data. If there are
          # no saved frames, generate a new frame sequence and take the first
          # save_count entries in it.
          if self._save_seq:
              return iter(self._save_seq)
          else:
              return itertools.islice(self.new_frame_seq(), self.save_count)
  
      def _init_draw(self):
          # Initialize the drawing either using the given init_func or by
          # calling the draw function with the first item of the frame sequence.
          # For blitting, the init_func should return a sequence of modified
          # artists.
          if self._init_func is None:
              self._draw_frame(next(self.new_frame_seq()))
          else:
              self._drawn_artists = self._init_func()
  
      def _draw_frame(self, framedata):
          # Save the data for potential saving of movies.
          self._save_seq.append(framedata)
  
          # Make sure to respect save_count (keep only the last save_count
          # around)
          self._save_seq = self._save_seq[-self.save_count:]
  
          # Call the func with framedata and args. If blitting is desired,
          # func needs to return a sequence of any artists that were modified.
          self._drawn_artists = self._func(framedata, *self._args)
  