content: """
  Abstract base classes define the primitives that renderers and
  graphics contexts must implement to serve as a matplotlib backend
  
  :class:`RendererBase`
      An abstract base class to handle drawing/rendering operations.
  
  :class:`FigureCanvasBase`
      The abstraction layer that separates the
      :class:`matplotlib.figure.Figure` from the backend specific
      details like a user interface drawing area
  
  :class:`GraphicsContextBase`
      An abstract base class that provides color, line styles, etc...
  
  :class:`Event`
      The base class for all of the matplotlib event
      handling.  Derived classes suh as :class:`KeyEvent` and
      :class:`MouseEvent` store the meta data like keys and buttons
      pressed, x and y locations in pixel and
      :class:`~matplotlib.axes.Axes` coordinates.
  
  """
  
  from __future__ import division
  import os, warnings, time
  
  import numpy as np
  import matplotlib.cbook as cbook
  import matplotlib.colors as colors
  import matplotlib.transforms as transforms
  import matplotlib.widgets as widgets
  from matplotlib import rcParams
  
  class RendererBase:
      """An abstract base class to handle drawing/rendering operations.
  
      The following methods *must* be implemented in the backend:
  
      * :meth:`draw_path`
      * :meth:`draw_image`
      * :meth:`draw_text`
      * :meth:`get_text_width_height_descent`
  
      The following methods *should* be implemented in the backend for
      optimization reasons:
  
      * :meth:`draw_markers`
      * :meth:`draw_path_collection`
      * :meth:`draw_quad_mesh`
      """
      def __init__(self):
          self._texmanager = None
  
      def open_group(self, s):
          """
          Open a grouping element with label *s*. Is only currently used by
          :mod:`~matplotlib.backends.backend_svg`
          """
          pass
  
      def close_group(self, s):
          """
          Close a grouping element with label *s*
          Is only currently used by :mod:`~matplotlib.backends.backend_svg`
          """
          pass
  
      def draw_path(self, gc, path, transform, rgbFace=None):
          """
          Draws a :class:`~matplotlib.path.Path` instance using the
          given affine transform.
          """
          raise NotImplementedError
  
      def draw_markers(self, gc, marker_path, marker_trans, path, trans, rgbFace=None):
          """
          Draws a marker at each of the vertices in path.  This includes
          all vertices, including control points on curves.  To avoid
          that behavior, those vertices should be removed before calling
          this function.
  
          *gc*
              the :class:`GraphicsContextBase` instance
  
          *marker_trans*
              is an affine transform applied to the marker.
  
          *trans*
               is an affine transform applied to the path.
  
          This provides a fallback implementation of draw_markers that
          makes multiple calls to :meth:`draw_path`.  Some backends may
          want to override this method in order to draw the marker only
          once and reuse it multiple times.
          """
          tpath = trans.transform_path(path)
          for vertices, codes in tpath.iter_segments():
              if len(vertices):
                  x,y = vertices[-2:]
                  self.draw_path(gc, marker_path,
                                 marker_trans + transforms.Affine2D().translate(x, y),
                                 rgbFace)
  
      def draw_path_collection(self, master_transform, cliprect, clippath,
                               clippath_trans, paths, all_transforms, offsets,
                               offsetTrans, facecolors, edgecolors, linewidths,
                               linestyles, antialiaseds, urls):
          """
          Draws a collection of paths, selecting drawing properties from
          the lists *facecolors*, *edgecolors*, *linewidths*,
          *linestyles* and *antialiaseds*. *offsets* is a list of
          offsets to apply to each of the paths.  The offsets in
          *offsets* are first transformed by *offsetTrans* before
          being applied.
  
          This provides a fallback implementation of
          :meth:`draw_path_collection` that makes multiple calls to
          draw_path.  Some backends may want to override this in order
          to render each set of path data only once, and then reference
          that path multiple times with the different offsets, colors,
          styles etc.  The generator methods
          :meth:`_iter_collection_raw_paths` and
          :meth:`_iter_collection` are provided to help with (and
          standardize) the implementation across backends.  It is highly
          recommended to use those generators, so that changes to the
          behavior of :meth:`draw_path_collection` can be made globally.
          """
          path_ids = []
          for path, transform in self._iter_collection_raw_paths(
              master_transform, paths, all_transforms):
              path_ids.append((path, transform))
  
          for xo, yo, path_id, gc, rgbFace in self._iter_collection(
              path_ids, cliprect, clippath, clippath_trans,
              offsets, offsetTrans, facecolors, edgecolors,
              linewidths, linestyles, antialiaseds, urls):
              path, transform = path_id
              transform = transforms.Affine2D(transform.get_matrix()).translate(xo, yo)
              self.draw_path(gc, path, transform, rgbFace)
  
      def draw_quad_mesh(self, master_transform, cliprect, clippath,
                         clippath_trans, meshWidth, meshHeight, coordinates,
                         offsets, offsetTrans, facecolors, antialiased,
                         showedges):
          """
          This provides a fallback implementation of
          :meth:`draw_quad_mesh` that generates paths and then calls
          :meth:`draw_path_collection`.
          """
          from matplotlib.collections import QuadMesh
          paths = QuadMesh.convert_mesh_to_paths(
              meshWidth, meshHeight, coordinates)
  
          if showedges:
              edgecolors = np.array([[0.0, 0.0, 0.0, 1.0]], np.float_)
              linewidths = np.array([1.0], np.float_)
          else:
              edgecolors = facecolors
              linewidths = np.array([0.0], np.float_)
  
          return self.draw_path_collection(
              master_transform, cliprect, clippath, clippath_trans,
              paths, [], offsets, offsetTrans, facecolors, edgecolors,
              linewidths, [], [antialiased], [None])
  
      def _iter_collection_raw_paths(self, master_transform, paths, all_transforms):
          """
          This is a helper method (along with :meth:`_iter_collection`) to make
          it easier to write a space-efficent :meth:`draw_path_collection`
          implementation in a backend.
  
          This method yields all of the base path/transform
          combinations, given a master transform, a list of paths and
          list of transforms.
  
          The arguments should be exactly what is passed in to
          :meth:`draw_path_collection`.
  
          The backend should take each yielded path and transform and
          create an object that can be referenced (reused) later.
          """
          Npaths      = len(paths)
          Ntransforms = len(all_transforms)
          N           = max(Npaths, Ntransforms)
  
          if Npaths == 0:
              return
  
          transform = transforms.IdentityTransform()
          for i in xrange(N):
              path = paths[i % Npaths]
              if Ntransforms:
                  transform = all_transforms[i % Ntransforms]
              yield path, transform + master_transform
  
      def _iter_collection(self, path_ids, cliprect, clippath, clippath_trans,
                           offsets, offsetTrans, facecolors, edgecolors,
                           linewidths, linestyles, antialiaseds, urls):
          """
          This is a helper method (along with
          :meth:`_iter_collection_raw_paths`) to make it easier to write
          a space-efficent :meth:`draw_path_collection` implementation in a
          backend.
  
          This method yields all of the path, offset and graphics
          context combinations to draw the path collection.  The caller
          should already have looped over the results of
          :meth:`_iter_collection_raw_paths` to draw this collection.
  
          The arguments should be the same as that passed into
          :meth:`draw_path_collection`, with the exception of
          *path_ids*, which is a list of arbitrary objects that the
          backend will use to reference one of the paths created in the
          :meth:`_iter_collection_raw_paths` stage.
  
          Each yielded result is of the form::
  
             xo, yo, path_id, gc, rgbFace
  
          where *xo*, *yo* is an offset; *path_id* is one of the elements of
          *path_ids*; *gc* is a graphics context and *rgbFace* is a color to
          use for filling the path.
          """
          Npaths      = len(path_ids)
          Noffsets    = len(offsets)
          N           = max(Npaths, Noffsets)
          Nfacecolors = len(facecolors)
          Nedgecolors = len(edgecolors)
          Nlinewidths = len(linewidths)
          Nlinestyles = len(linestyles)
          Naa         = len(antialiaseds)
          Nurls       = len(urls)
  
          if (Nfacecolors == 0 and Nedgecolors == 0) or Npaths == 0:
              return
          if Noffsets:
              toffsets = offsetTrans.transform(offsets)
  
          gc = self.new_gc()
  
          gc.set_clip_rectangle(cliprect)
          if clippath is not None:
              clippath = transforms.TransformedPath(clippath, clippath_trans)
              gc.set_clip_path(clippath)
  
          if Nfacecolors == 0:
              rgbFace = None
  
          if Nedgecolors == 0:
              gc.set_linewidth(0.0)
  
          xo, yo = 0, 0
          for i in xrange(N):
              path_id = path_ids[i % Npaths]
              if Noffsets:
                  xo, yo = toffsets[i % Noffsets]
              if Nfacecolors:
                  rgbFace = facecolors[i % Nfacecolors]
              if Nedgecolors:
                  gc.set_foreground(edgecolors[i % Nedgecolors])
                  if Nlinewidths:
                      gc.set_linewidth(linewidths[i % Nlinewidths])
                  if Nlinestyles:
                      gc.set_dashes(*linestyles[i % Nlinestyles])
              if rgbFace is not None and len(rgbFace)==4:
                  gc.set_alpha(rgbFace[-1])
                  rgbFace = rgbFace[:3]
              gc.set_antialiased(antialiaseds[i % Naa])
  
              if Nurls:
                  gc.set_url(urls[i % Nurls])
  
              yield xo, yo, path_id, gc, rgbFace
  
      def get_image_magnification(self):
          """
          Get the factor by which to magnify images passed to :meth:`draw_image`.
          Allows a backend to have images at a different resolution to other
          artists.
          """
          return 1.0
  
      def draw_image(self, x, y, im, bbox, clippath=None, clippath_trans=None):
          """
          Draw the image instance into the current axes;
  
          *x*
              is the distance in pixels from the left hand side of the canvas.
  
          *y*
              the distance from the origin.  That is, if origin is
              upper, y is the distance from top.  If origin is lower, y
              is the distance from bottom
  
          *im*
              the :class:`matplotlib._image.Image` instance
  
          *bbox*
              a :class:`matplotlib.transforms.Bbox` instance for clipping, or
              None
  
          """
          raise NotImplementedError
  
      def option_image_nocomposite(self):
          """
          overwrite this method for renderers that do not necessarily
          want to rescale and composite raster images. (like SVG)
          """
          return False
  
      def draw_tex(self, gc, x, y, s, prop, angle, ismath='TeX!'):
          raise NotImplementedError
  
      def draw_text(self, gc, x, y, s, prop, angle, ismath=False):
          """
          Draw the text instance
  
          *gc*
              the :class:`GraphicsContextBase` instance
  
          *x*
              the x location of the text in display coords
  
          *y*
              the y location of the text in display coords
  
          *s*
               a :class:`matplotlib.text.Text` instance
  
          *prop*
            a :class:`matplotlib.font_manager.FontProperties` instance
  
          *angle*
              the rotation angle in degrees
  
          **backend implementers note**
  
          When you are trying to determine if you have gotten your bounding box
          right (which is what enables the text layout/alignment to work
          properly), it helps to change the line in text.py::
  
              if 0: bbox_artist(self, renderer)
  
          to if 1, and then the actual bounding box will be blotted along with
          your text.
          """
          raise NotImplementedError
  
      def flipy(self):
          """
          Return true if y small numbers are top for renderer Is used
          for drawing text (:mod:`matplotlib.text`) and images
          (:mod:`matplotlib.image`) only
          """
          return True
  
      def get_canvas_width_height(self):
          'return the canvas width and height in display coords'
          return 1, 1
  
      def get_texmanager(self):
          """
          return the :class:`matplotlib.texmanager.TexManager` instance
          """
          if self._texmanager is None:
              from matplotlib.texmanager import TexManager
              self._texmanager = TexManager()
          return self._texmanager
  
      def get_text_width_height_descent(self, s, prop, ismath):
          """
          get the width and height, and the offset from the bottom to the
          baseline (descent), in display coords of the string s with
          :class:`~matplotlib.font_manager.FontProperties` prop
          """
          raise NotImplementedError
  
      def new_gc(self):
          """
          Return an instance of a :class:`GraphicsContextBase`
          """
          return GraphicsContextBase()
  
      def points_to_pixels(self, points):
          """
          Convert points to display units
  
          *points*
              a float or a numpy array of float
  
          return points converted to pixels
  
          You need to override this function (unless your backend
          doesn't have a dpi, eg, postscript or svg).  Some imaging
          systems assume some value for pixels per inch::
  
              points to pixels = points * pixels_per_inch/72.0 * dpi/72.0
          """
          return points
  
      def strip_math(self, s):
          return cbook.strip_math(s)
  
      def start_rasterizing(self):
          pass
  
      def stop_rasterizing(self):
          pass
  
  
  class GraphicsContextBase:
      """
      An abstract base class that provides color, line styles, etc...
      """
  
      # a mapping from dash styles to suggested offset, dash pairs
      dashd = {
          'solid'   : (None, None),
          'dashed'  : (0, (6.0, 6.0)),
          'dashdot' : (0, (3.0, 5.0, 1.0, 5.0)),
          'dotted'  : (0, (1.0, 3.0)),
                }
  
      def __init__(self):
          self._alpha = 1.0
          self._antialiased = 1  # use 0,1 not True, False for extension code
          self._capstyle = 'butt'
          self._cliprect = None
          self._clippath = None
          self._dashes = None, None
          self._joinstyle = 'miter'
          self._linestyle = 'solid'
          self._linewidth = 1
          self._rgb = (0.0, 0.0, 0.0)
          self._hatch = None
          self._url = None
          self._snap = None
  
      def copy_properties(self, gc):
          'Copy properties from gc to self'
          self._alpha = gc._alpha
          self._antialiased = gc._antialiased
          self._capstyle = gc._capstyle
          self._cliprect = gc._cliprect
          self._clippath = gc._clippath
          self._dashes = gc._dashes
          self._joinstyle = gc._joinstyle
          self._linestyle = gc._linestyle
          self._linewidth = gc._linewidth
          self._rgb = gc._rgb
          self._hatch = gc._hatch
          self._url = gc._url
          self._snap = gc._snap
  
      def get_alpha(self):
          """
          Return the alpha value used for blending - not supported on
          all backends
          """
          return self._alpha
  
      def get_antialiased(self):
          "Return true if the object should try to do antialiased rendering"
          return self._antialiased
  
      def get_capstyle(self):
          """
          Return the capstyle as a string in ('butt', 'round', 'projecting')
          """
          return self._capstyle
  
      def get_clip_rectangle(self):
          """
          Return the clip rectangle as a :class:`~matplotlib.transforms.Bbox` instance
          """
          return self._cliprect
  
      def get_clip_path(self):
          """
          Return the clip path in the form (path, transform), where path
          is a :class:`~matplotlib.path.Path` instance, and transform is
          an affine transform to apply to the path before clipping.
          """
          if self._clippath is not None:
              return self._clippath.get_transformed_path_and_affine()
          return None, None
  
      def get_dashes(self):
          """
          Return the dash information as an offset dashlist tuple.
  
          The dash list is a even size list that gives the ink on, ink
          off in pixels.
  
          See p107 of to PostScript `BLUEBOOK
          <http://www-cdf.fnal.gov/offline/PostScript/BLUEBOOK.PDF>`_
          for more info.
  
          Default value is None
          """
          return self._dashes
  
      def get_joinstyle(self):
          """
          Return the line join style as one of ('miter', 'round', 'bevel')
          """
          return self._joinstyle
  
      def get_linestyle(self, style):
          """
          Return the linestyle: one of ('solid', 'dashed', 'dashdot',
          'dotted').
          """
          return self._linestyle
  
      def get_linewidth(self):
          """
          Return the line width in points as a scalar
          """
          return self._linewidth
  
      def get_rgb(self):
          """
          returns a tuple of three floats from 0-1.  color can be a
          matlab format string, a html hex color string, or a rgb tuple
          """
          return self._rgb
  
      def get_url(self):
          """
          returns a url if one is set, None otherwise
          """
          return self._url
  
      def get_snap(self):
          """
          returns the snap setting which may be:
  
            * True: snap vertices to the nearest pixel center
  
            * False: leave vertices as-is
  
            * None: (auto) If the path contains only rectilinear line
              segments, round to the nearest pixel center
          """
          return self._snap
  
      def set_alpha(self, alpha):
          """
          Set the alpha value used for blending - not supported on
          all backends
          """
          self._alpha = alpha
  
      def set_antialiased(self, b):
          """
          True if object should be drawn with antialiased rendering
          """
  
          # use 0, 1 to make life easier on extension code trying to read the gc
          if b: self._antialiased = 1
          else: self._antialiased = 0
  
      def set_capstyle(self, cs):
          """
          Set the capstyle as a string in ('butt', 'round', 'projecting')
          """
          if cs in ('butt', 'round', 'projecting'):
              self._capstyle = cs
          else:
              raise ValueError('Unrecognized cap style.  Found %s' % cs)
  
      def set_clip_rectangle(self, rectangle):
          """
          Set the clip rectangle with sequence (left, bottom, width, height)
          """
          self._cliprect = rectangle
  
      def set_clip_path(self, path):
          """
          Set the clip path and transformation.  Path should be a
          :class:`~matplotlib.transforms.TransformedPath` instance.
          """
          assert path is None or isinstance(path, transforms.TransformedPath)
          self._clippath = path
  
      def set_dashes(self, dash_offset, dash_list):
          """
          Set the dash style for the gc.
  
          *dash_offset*
              is the offset (usually 0).
  
          *dash_list*
              specifies the on-off sequence as points.  ``(None, None)`` specifies a solid line
  
          """
          self._dashes = dash_offset, dash_list
  
      def set_foreground(self, fg, isRGB=False):
          """
          Set the foreground color.  fg can be a matlab format string, a
          html hex color string, an rgb unit tuple, or a float between 0
          and 1.  In the latter case, grayscale is used.
  
          The :class:`GraphicsContextBase` converts colors to rgb
          internally.  If you know the color is rgb already, you can set
          ``isRGB=True`` to avoid the performace hit of the conversion
          """
          if isRGB:
              self._rgb = fg
          else:
              self._rgb = colors.colorConverter.to_rgba(fg)
  
      def set_graylevel(self, frac):
          """
          Set the foreground color to be a gray level with *frac*
          """
          self._rgb = (frac, frac, frac)
  
      def set_joinstyle(self, js):
          """
          Set the join style to be one of ('miter', 'round', 'bevel')
          """
          if js in ('miter', 'round', 'bevel'):
              self._joinstyle = js
          else:
              raise ValueError('Unrecognized join style.  Found %s' % js)
  
      def set_linewidth(self, w):
          """
          Set the linewidth in points
          """
          self._linewidth = w
  
      def set_linestyle(self, style):
          """
          Set the linestyle to be one of ('solid', 'dashed', 'dashdot',
          'dotted').
          """
          try:
              offset, dashes = self.dashd[style]
          except:
              raise ValueError('Unrecognized linestyle: %s' % style)
          self._linestyle = style
          self.set_dashes(offset, dashes)
  
      def set_url(self, url):
          """
          Sets the url for links in compatible backends
          """
          self._url = url
  
      def set_snap(self, snap):
          """
          Sets the snap setting which may be:
  
            * True: snap vertices to the nearest pixel center
  
            * False: leave vertices as-is
  
            * None: (auto) If the path contains only rectilinear line
              segments, round to the nearest pixel center
          """
          self._snap = snap
  
      def set_hatch(self, hatch):
          """
          Sets the hatch style for filling
          """
          self._hatch = hatch
  
      def get_hatch(self):
          """
          Gets the current hatch style
          """
          return self._hatch
  
  class Event:
      """
      A matplotlib event.  Attach additional attributes as defined in
      :meth:`FigureCanvasBase.mpl_connect`.  The following attributes
      are defined and shown with their default values
  
      *name*
          the event name
  
      *canvas*
          the FigureCanvas instance generating the event
  
      *guiEvent*
          the GUI event that triggered the matplotlib event
  
  
      """
      def __init__(self, name, canvas,guiEvent=None):
          self.name = name
          self.canvas = canvas
          self.guiEvent = guiEvent
  
  class IdleEvent(Event):
      """
      An event triggered by the GUI backend when it is idle -- useful
      for passive animation
      """
      pass
  
  class DrawEvent(Event):
      """
      An event triggered by a draw operation on the canvas
  
      In addition to the :class:`Event` attributes, the following event attributes are defined:
  
      *renderer*
          the :class:`RendererBase` instance for the draw event
  
      """
      def __init__(self, name, canvas, renderer):
          Event.__init__(self, name, canvas)
          self.renderer = renderer
  
  class ResizeEvent(Event):
      """
      An event triggered by a canvas resize
  
      In addition to the :class:`Event` attributes, the following event attributes are defined:
  
      *width*
          width of the canvas in pixels
  
      *height*
          height of the canvas in pixels
  
      """
      def __init__(self, name, canvas):
          Event.__init__(self, name, canvas)
          self.width, self.height = canvas.get_width_height()
  
  class LocationEvent(Event):
      """
      A event that has a screen location
  
      The following additional attributes are defined and shown with
      their default values
  
      In addition to the :class:`Event` attributes, the following event attributes are defined:
  
      *x*
          x position - pixels from left of canvas
  
      *y*
          y position - pixels from bottom of canvas
  
      *inaxes*
          the :class:`~matplotlib.axes.Axes` instance if mouse is over axes
  
      *xdata*
          x coord of mouse in data coords
  
      *ydata*
          y coord of mouse in data coords
  
      """
      x      = None       # x position - pixels from left of canvas
      y      = None       # y position - pixels from right of canvas
      inaxes = None       # the Axes instance if mouse us over axes
      xdata  = None       # x coord of mouse in data coords
      ydata  = None       # y coord of mouse in data coords
  
      # the last event that was triggered before this one
      lastevent = None
  
      def __init__(self, name, canvas, x, y,guiEvent=None):
          """
          *x*, *y* in figure coords, 0,0 = bottom, left
          """
          Event.__init__(self, name, canvas,guiEvent=guiEvent)
          self.x = x
          self.y = y
  
  
  
          if x is None or y is None:
              # cannot check if event was in axes if no x,y info
              self.inaxes = None
              self._update_enter_leave()
              return
  
          # Find all axes containing the mouse
          axes_list = [a for a in self.canvas.figure.get_axes() if a.in_axes(self)]
  
          if len(axes_list) == 0: # None found
              self.inaxes = None
              self._update_enter_leave()
              return
          elif (len(axes_list) > 1): # Overlap, get the highest zorder
              axCmp = lambda _x,_y: cmp(_x.zorder, _y.zorder)
              axes_list.sort(axCmp)
              self.inaxes = axes_list[-1] # Use the highest zorder
          else: # Just found one hit
              self.inaxes = axes_list[0]
  
          try:
              xdata, ydata = self.inaxes.transData.inverted().transform_point((x, y))
          except ValueError:
              self.xdata  = None
              self.ydata  = None
          else:
              self.xdata  = xdata
              self.ydata  = ydata
  
          self._update_enter_leave()
  
      def _update_enter_leave(self):
          'process the figure/axes enter leave events'
          if LocationEvent.lastevent is not None:
              last = LocationEvent.lastevent
              if last.inaxes!=self.inaxes:
                  # process axes enter/leave events
                  if last.inaxes is not None:
                      last.canvas.callbacks.process('axes_leave_event', last)
                  if self.inaxes is not None:
                      self.canvas.callbacks.process('axes_enter_event', self)
  
          else:
              # process a figure enter event
              if self.inaxes is not None:
                  self.canvas.callbacks.process('axes_enter_event', self)
  
  
          LocationEvent.lastevent = self
  
  
  
  
  class MouseEvent(LocationEvent):
      """
      A mouse event ('button_press_event', 'button_release_event', 'scroll_event',
      'motion_notify_event').
  
      In addition to the :class:`Event` and :class:`LocationEvent`
      attributes, the following attributes are defined:
  
      *button*
          button pressed None, 1, 2, 3, 'up', 'down' (up and down are used for scroll events)
  
      *key*
          the key pressed: None, chr(range(255), 'shift', 'win', or 'control'
  
      *step*
          number of scroll steps (positive for 'up', negative for 'down')
  
  
      Example usage::
  
          def on_press(event):
              print 'you pressed', event.button, event.xdata, event.ydata
  
          cid = fig.canvas.mpl_connect('button_press_event', on_press)
  
      """
      x      = None       # x position - pixels from left of canvas
      y      = None       # y position - pixels from right of canvas
      button = None       # button pressed None, 1, 2, 3
      inaxes = None       # the Axes instance if mouse us over axes
      xdata  = None       # x coord of mouse in data coords
      ydata  = None       # y coord of mouse in data coords
      step   = None       # scroll steps for scroll events
  
      def __init__(self, name, canvas, x, y, button=None, key=None,
                   step=0, guiEvent=None):
          """
          x, y in figure coords, 0,0 = bottom, left
          button pressed None, 1, 2, 3, 'up', 'down'
          """
          LocationEvent.__init__(self, name, canvas, x, y, guiEvent=guiEvent)
          self.button = button
          self.key = key
          self.step = step
  
  class PickEvent(Event):
      """
      a pick event, fired when the user picks a location on the canvas
      sufficiently close to an artist.
  
      Attrs: all the :class:`Event` attributes plus
  
      *mouseevent*
          the :class:`MouseEvent` that generated the pick
  
      *artist*
          the :class:`~matplotlib.artist.Artist` picked
  
      other
          extra class dependent attrs -- eg a
          :class:`~matplotlib.lines.Line2D` pick may define different
          extra attributes than a
          :class:`~matplotlib.collections.PatchCollection` pick event
  
  
      Example usage::
  
          line, = ax.plot(rand(100), 'o', picker=5)  # 5 points tolerance
  
          def on_pick(event):
              thisline = event.artist
              xdata, ydata = thisline.get_data()
              ind = event.ind
              print 'on pick line:', zip(xdata[ind], ydata[ind])
  
          cid = fig.canvas.mpl_connect('pick_event', on_pick)
  
      """
      def __init__(self, name, canvas, mouseevent, artist, guiEvent=None, **kwargs):
          Event.__init__(self, name, canvas, guiEvent)
          self.mouseevent = mouseevent
          self.artist = artist
          self.__dict__.update(kwargs)
  
  
  class KeyEvent(LocationEvent):
      """
      A key event (key press, key release).
  
      Attach additional attributes as defined in
      :meth:`FigureCanvasBase.mpl_connect`.
  
      In addition to the :class:`Event` and :class:`LocationEvent`
      attributes, the following attributes are defined:
  
      *key*
          the key pressed: None, chr(range(255), shift, win, or control
  
      This interface may change slightly when better support for
      modifier keys is included.
  
  
      Example usage::
  
          def on_key(event):
              print 'you pressed', event.key, event.xdata, event.ydata
  
          cid = fig.canvas.mpl_connect('key_press_event', on_key)
  
      """
      def __init__(self, name, canvas, key, x=0, y=0, guiEvent=None):
          LocationEvent.__init__(self, name, canvas, x, y, guiEvent=guiEvent)
          self.key = key
  
  
  
  class FigureCanvasBase:
      """
      The canvas the figure renders into.
  
      Public attributes
  
          *figure*
              A :class:`matplotlib.figure.Figure` instance
  
        """
      events = [
          'resize_event',
          'draw_event',
          'key_press_event',
          'key_release_event',
          'button_press_event',
          'button_release_event',
          'scroll_event',
          'motion_notify_event',
          'pick_event',
          'idle_event',
          'figure_enter_event',
          'figure_leave_event',
          'axes_enter_event',
          'axes_leave_event'
          ]
  
  
      def __init__(self, figure):
          figure.set_canvas(self)
          self.figure = figure
          # a dictionary from event name to a dictionary that maps cid->func
          self.callbacks = cbook.CallbackRegistry(self.events)
          self.widgetlock = widgets.LockDraw()
          self._button     = None  # the button pressed
          self._key        = None  # the key pressed
          self._lastx, self._lasty = None, None
          self.button_pick_id = self.mpl_connect('button_press_event',self.pick)
          self.scroll_pick_id = self.mpl_connect('scroll_event',self.pick)
  
          if False:
              ## highlight the artists that are hit
              self.mpl_connect('motion_notify_event',self.onHilite)
              ## delete the artists that are clicked on
              #self.mpl_disconnect(self.button_pick_id)
              #self.mpl_connect('button_press_event',self.onRemove)
  
      def onRemove(self, ev):
          """
          Mouse event processor which removes the top artist
          under the cursor.  Connect this to the 'mouse_press_event'
          using::
  
              canvas.mpl_connect('mouse_press_event',canvas.onRemove)
          """
          def sort_artists(artists):
              # This depends on stable sort and artists returned
              # from get_children in z order.
              L = [ (h.zorder, h) for h in artists ]
              L.sort()
              return [ h for zorder, h in L ]
  
          # Find the top artist under the cursor
          under = sort_artists(self.figure.hitlist(ev))
          h = None
          if under: h = under[-1]
  
          # Try deleting that artist, or its parent if you
          # can't delete the artist
          while h:
              print "Removing",h
              if h.remove():
                  self.draw_idle()
                  break
              parent = None
              for p in under:
                  if h in p.get_children():
                      parent = p
                      break
              h = parent
  
      def onHilite(self, ev):
          """
          Mouse event processor which highlights the artists
          under the cursor.  Connect this to the 'motion_notify_event'
          using::
  
              canvas.mpl_connect('motion_notify_event',canvas.onHilite)
          """
          if not hasattr(self,'_active'): self._active = dict()
  
          under = self.figure.hitlist(ev)
          enter = [a for a in under if a not in self._active]
          leave = [a for a in self._active if a not in under]
          print "within:"," ".join([str(x) for x in under])
          #print "entering:",[str(a) for a in enter]
          #print "leaving:",[str(a) for a in leave]
          # On leave restore the captured colour
          for a in leave:
              if hasattr(a,'get_color'):
                  a.set_color(self._active[a])
              elif hasattr(a,'get_edgecolor'):
                  a.set_edgecolor(self._active[a][0])
                  a.set_facecolor(self._active[a][1])
              del self._active[a]
          # On enter, capture the color and repaint the artist
          # with the highlight colour.  Capturing colour has to
          # be done first in case the parent recolouring affects
          # the child.
          for a in enter:
              if hasattr(a,'get_color'):
                  self._active[a] = a.get_color()
              elif hasattr(a,'get_edgecolor'):
                  self._active[a] = (a.get_edgecolor(),a.get_facecolor())
              else: self._active[a] = None
          for a in enter:
              if hasattr(a,'get_color'):
                  a.set_color('red')
              elif hasattr(a,'get_edgecolor'):
                  a.set_edgecolor('red')
                  a.set_facecolor('lightblue')
              else: self._active[a] = None
          self.draw_idle()
  
      def pick(self, mouseevent):
          if not self.widgetlock.locked():
              self.figure.pick(mouseevent)
  
      def blit(self, bbox=None):
          """
          blit the canvas in bbox (default entire canvas)
          """
          pass
  
      def resize(self, w, h):
          """
          set the canvas size in pixels
          """
          pass
  
      def draw_event(self, renderer):
          """
          This method will be call all functions connected to the
          'draw_event' with a :class:`DrawEvent`
          """
  
          s = 'draw_event'
          event = DrawEvent(s, self, renderer)
          self.callbacks.process(s, event)
  
      def resize_event(self):
          """
          This method will be call all functions connected to the
          'resize_event' with a :class:`ResizeEvent`
          """
  
          s = 'resize_event'
          event = ResizeEvent(s, self)
          self.callbacks.process(s, event)
  
      def key_press_event(self, key, guiEvent=None):
          """
          This method will be call all functions connected to the
          'key_press_event' with a :class:`KeyEvent`
          """
          self._key = key
          s = 'key_press_event'
          event = KeyEvent(s, self, key, self._lastx, self._lasty, guiEvent=guiEvent)
          self.callbacks.process(s, event)
  
      def key_release_event(self, key, guiEvent=None):
          """
          This method will be call all functions connected to the
          'key_release_event' with a :class:`KeyEvent`
          """
          s = 'key_release_event'
          event = KeyEvent(s, self, key, self._lastx, self._lasty, guiEvent=guiEvent)
          self.callbacks.process(s, event)
          self._key = None
  
      def pick_event(self, mouseevent, artist, **kwargs):
          """
          This method will be called by artists who are picked and will
          fire off :class:`PickEvent` callbacks registered listeners
          """
          s = 'pick_event'
          event = PickEvent(s, self, mouseevent, artist, **kwargs)
          self.callbacks.process(s, event)
  
      def scroll_event(self, x, y, step, guiEvent=None):
          """
          Backend derived classes should call this function on any
          scroll wheel event.  x,y are the canvas coords: 0,0 is lower,
          left.  button and key are as defined in MouseEvent.
  
          This method will be call all functions connected to the
          'scroll_event' with a :class:`MouseEvent` instance.
          """
          if step >= 0:
              self._button = 'up'
          else:
              self._button = 'down'
          s = 'scroll_event'
          mouseevent = MouseEvent(s, self, x, y, self._button, self._key,
                                  step=step, guiEvent=guiEvent)
          self.callbacks.process(s, mouseevent)
  
  
      def button_press_event(self, x, y, button, guiEvent=None):
          """
          Backend derived classes should call this function on any mouse
          button press.  x,y are the canvas coords: 0,0 is lower, left.
          button and key are as defined in :class:`MouseEvent`.
  
          This method will be call all functions connected to the
          'button_press_event' with a :class:`MouseEvent` instance.
  
          """
          self._button = button
          s = 'button_press_event'
          mouseevent = MouseEvent(s, self, x, y, button, self._key, guiEvent=guiEvent)
          self.callbacks.process(s, mouseevent)
  
      def button_release_event(self, x, y, button, guiEvent=None):
          """
          Backend derived classes should call this function on any mouse
          button release.
  
          *x*
              the canvas coordinates where 0=left
  
          *y*
              the canvas coordinates where 0=bottom
  
          *guiEvent*
              the native UI event that generated the mpl event
  
  
          This method will be call all functions connected to the
          'button_release_event' with a :class:`MouseEvent` instance.
  
          """
          s = 'button_release_event'
          event = MouseEvent(s, self, x, y, button, self._key, guiEvent=guiEvent)
          self.callbacks.process(s, event)
          self._button = None
  
      def motion_notify_event(self, x, y, guiEvent=None):
          """
          Backend derived classes should call this function on any
          motion-notify-event.
  
          *x*
              the canvas coordinates where 0=left
  
          *y*
              the canvas coordinates where 0=bottom
  
          *guiEvent*
              the native UI event that generated the mpl event
  
  
          This method will be call all functions connected to the
          'motion_notify_event' with a :class:`MouseEvent` instance.
  
          """
          self._lastx, self._lasty = x, y
          s = 'motion_notify_event'
          event = MouseEvent(s, self, x, y, self._button, self._key,
                             guiEvent=guiEvent)
          self.callbacks.process(s, event)
  
      def leave_notify_event(self, guiEvent=None):
          """
          Backend derived classes should call this function when leaving
          canvas
  
          *guiEvent*
              the native UI event that generated the mpl event
  
          """
          self.callbacks.process('figure_leave_event', LocationEvent.lastevent)
          LocationEvent.lastevent = None
  
      def enter_notify_event(self, guiEvent=None):
          """
          Backend derived classes should call this function when entering
          canvas
  
          *guiEvent*
              the native UI event that generated the mpl event
  
          """
          event = Event('figure_enter_event', self, guiEvent)
          self.callbacks.process('figure_enter_event', event)
  
      def idle_event(self, guiEvent=None):
          'call when GUI is idle'
          s = 'idle_event'
          event = IdleEvent(s, self, guiEvent=guiEvent)
          self.callbacks.process(s, event)
  
  
      def draw(self, *args, **kwargs):
          """
          Render the :class:`~matplotlib.figure.Figure`
          """
          pass
  
      def draw_idle(self, *args, **kwargs):
          """
          :meth:`draw` only if idle; defaults to draw but backends can overrride
          """
          self.draw(*args, **kwargs)
  
      def draw_cursor(self, event):
          """
          Draw a cursor in the event.axes if inaxes is not None.  Use
          native GUI drawing for efficiency if possible
          """
          pass
  
      def get_width_height(self):
          """
          return the figure width and height in points or pixels
          (depending on the backend), truncated to integers
          """
          return int(self.figure.bbox.width), int(self.figure.bbox.height)
  
      filetypes = {
          'emf': 'Enhanced Metafile',
          'eps': 'Encapsulated Postscript',
          'pdf': 'Portable Document Format',
          'png': 'Portable Network Graphics',
          'ps' : 'Postscript',
          'raw': 'Raw RGBA bitmap',
          'rgba': 'Raw RGBA bitmap',
          'svg': 'Scalable Vector Graphics',
          'svgz': 'Scalable Vector Graphics'
          }
  
      # All of these print_* functions do a lazy import because
      #  a) otherwise we'd have cyclical imports, since all of these
      #     classes inherit from FigureCanvasBase
      #  b) so we don't import a bunch of stuff the user may never use
  
      def print_emf(self, *args, **kwargs):
          from backends.backend_emf import FigureCanvasEMF # lazy import
          emf = self.switch_backends(FigureCanvasEMF)
          return emf.print_emf(*args, **kwargs)
  
      def print_eps(self, *args, **kwargs):
          from backends.backend_ps import FigureCanvasPS # lazy import
          ps = self.switch_backends(FigureCanvasPS)
          return ps.print_eps(*args, **kwargs)
  
      def print_pdf(self, *args, **kwargs):
          from backends.backend_pdf import FigureCanvasPdf # lazy import
          pdf = self.switch_backends(FigureCanvasPdf)
          return pdf.print_pdf(*args, **kwargs)
  
      def print_png(self, *args, **kwargs):
          from backends.backend_agg import FigureCanvasAgg # lazy import
          agg = self.switch_backends(FigureCanvasAgg)
          return agg.print_png(*args, **kwargs)
  
      def print_ps(self, *args, **kwargs):
          from backends.backend_ps import FigureCanvasPS # lazy import
          ps = self.switch_backends(FigureCanvasPS)
          return ps.print_ps(*args, **kwargs)
  
      def print_raw(self, *args, **kwargs):
          from backends.backend_agg import FigureCanvasAgg # lazy import
          agg = self.switch_backends(FigureCanvasAgg)
          return agg.print_raw(*args, **kwargs)
      print_bmp = print_rgb = print_raw
  
      def print_svg(self, *args, **kwargs):
          from backends.backend_svg import FigureCanvasSVG # lazy import
          svg = self.switch_backends(FigureCanvasSVG)
          return svg.print_svg(*args, **kwargs)
  
      def print_svgz(self, *args, **kwargs):
          from backends.backend_svg import FigureCanvasSVG # lazy import
          svg = self.switch_backends(FigureCanvasSVG)
          return svg.print_svgz(*args, **kwargs)
  
      def get_supported_filetypes(self):
          return self.filetypes
  
      def get_supported_filetypes_grouped(self):
          groupings = {}
          for ext, name in self.filetypes.items():
              groupings.setdefault(name, []).append(ext)
              groupings[name].sort()
          return groupings
  
      def print_figure(self, filename, dpi=None, facecolor='w', edgecolor='w',
                       orientation='portrait', format=None, **kwargs):
          """
          Render the figure to hardcopy. Set the figure patch face and edge
          colors.  This is useful because some of the GUIs have a gray figure
          face color background and you'll probably want to override this on
          hardcopy.
  
          Arguments are:
  
          *filename*
              can also be a file object on image backends
  
          *orientation*
              only currently applies to PostScript printing.
  
          *dpi*
              the dots per inch to save the figure in; if None, use savefig.dpi
  
          *facecolor*
              the facecolor of the figure
  
          *edgecolor*
              the edgecolor of the figure
  
          *orientation*  '
              landscape' | 'portrait' (not supported on all backends)
  
          *format*
              when set, forcibly set the file format to save to
          """
          if format is None:
              if cbook.is_string_like(filename):
                  format = os.path.splitext(filename)[1][1:]
              if format is None or format == '':
                  format = self.get_default_filetype()
                  if cbook.is_string_like(filename):
                      filename = filename.rstrip('.') + '.' + format
          format = format.lower()
  
          method_name = 'print_%s' % format
          if (format not in self.filetypes or
              not hasattr(self, method_name)):
              formats = self.filetypes.keys()
              formats.sort()
              raise ValueError(
                  'Format "%s" is not supported.\n'
                  'Supported formats: '
                  '%s.' % (format, ', '.join(formats)))
  
          if dpi is None:
              dpi = rcParams['savefig.dpi']
  
          origDPI = self.figure.dpi
          origfacecolor = self.figure.get_facecolor()
          origedgecolor = self.figure.get_edgecolor()
  
          self.figure.dpi = dpi
          self.figure.set_facecolor(facecolor)
          self.figure.set_edgecolor(edgecolor)
  
          try:
              result = getattr(self, method_name)(
                  filename,
                  dpi=dpi,
                  facecolor=facecolor,
                  edgecolor=edgecolor,
                  orientation=orientation,
                  **kwargs)
          finally:
              self.figure.dpi = origDPI
              self.figure.set_facecolor(origfacecolor)
              self.figure.set_edgecolor(origedgecolor)
              self.figure.set_canvas(self)
              #self.figure.canvas.draw() ## seems superfluous
          return result
  
      def get_default_filetype(self):
          raise NotImplementedError
  
      def set_window_title(self, title):
          """
          Set the title text of the window containing the figure.  Note that
          this has no effect if there is no window (eg, a PS backend).
          """
          if hasattr(self, "manager"):
              self.manager.set_window_title(title)
  
      def switch_backends(self, FigureCanvasClass):
          """
          instantiate an instance of FigureCanvasClass
  
          This is used for backend switching, eg, to instantiate a
          FigureCanvasPS from a FigureCanvasGTK.  Note, deep copying is
          not done, so any changes to one of the instances (eg, setting
          figure size or line props), will be reflected in the other
          """
          newCanvas = FigureCanvasClass(self.figure)
          return newCanvas
  
      def mpl_connect(self, s, func):
          """
          Connect event with string *s* to *func*.  The signature of *func* is::
  
            def func(event)
  
          where event is a :class:`matplotlib.backend_bases.Event`.  The
          following events are recognized
  
          - 'button_press_event'
          - 'button_release_event'
          - 'draw_event'
          - 'key_press_event'
          - 'key_release_event'
          - 'motion_notify_event'
          - 'pick_event'
          - 'resize_event'
          - 'scroll_event'
  
          For the location events (button and key press/release), if the
          mouse is over the axes, the variable ``event.inaxes`` will be
          set to the :class:`~matplotlib.axes.Axes` the event occurs is
          over, and additionally, the variables ``event.xdata`` and
          ``event.ydata`` will be defined.  This is the mouse location
          in data coords.  See
          :class:`~matplotlib.backend_bases.KeyEvent` and
          :class:`~matplotlib.backend_bases.MouseEvent` for more info.
  
          Return value is a connection id that can be used with
          :meth:`~matplotlib.backend_bases.Event.mpl_disconnect`.
  
          Example usage::
  
              def on_press(event):
                  print 'you pressed', event.button, event.xdata, event.ydata
  
              cid = canvas.mpl_connect('button_press_event', on_press)
  
          """
  
          return self.callbacks.connect(s, func)
  
      def mpl_disconnect(self, cid):
          """
          disconnect callback id cid
  
          Example usage::
  
              cid = canvas.mpl_connect('button_press_event', on_press)
              #...later
              canvas.mpl_disconnect(cid)
          """
          return self.callbacks.disconnect(cid)
  
      def flush_events(self):
          """
          Flush the GUI events for the figure. Implemented only for
          backends with GUIs.
          """
          raise NotImplementedError
  
      def start_event_loop(self,timeout):
          """
          Start an event loop.  This is used to start a blocking event
          loop so that interactive functions, such as ginput and
          waitforbuttonpress, can wait for events.  This should not be
          confused with the main GUI event loop, which is always running
          and has nothing to do with this.
  
          This is implemented only for backends with GUIs.
          """
          raise NotImplementedError
  
      def stop_event_loop(self):
          """
          Stop an event loop.  This is used to stop a blocking event
          loop so that interactive functions, such as ginput and
          waitforbuttonpress, can wait for events.
  
          This is implemented only for backends with GUIs.
          """
          raise NotImplementedError
  
      def start_event_loop_default(self,timeout=0):
          """
          Start an event loop.  This is used to start a blocking event
          loop so that interactive functions, such as ginput and
          waitforbuttonpress, can wait for events.  This should not be
          confused with the main GUI event loop, which is always running
          and has nothing to do with this.
  
          This function provides default event loop functionality based
          on time.sleep that is meant to be used until event loop
          functions for each of the GUI backends can be written.  As
          such, it throws a deprecated warning.
  
          Call signature::
  
              start_event_loop_default(self,timeout=0)
  
          This call blocks until a callback function triggers
          stop_event_loop() or *timeout* is reached.  If *timeout* is
          <=0, never timeout.
          """
          str = "Using default event loop until function specific"
          str += " to this GUI is implemented"
          warnings.warn(str,DeprecationWarning)
  
          if timeout <= 0: timeout = np.inf
          timestep = 0.01
          counter = 0
          self._looping = True
          while self._looping and counter*timestep < timeout:
              self.flush_events()
              time.sleep(timestep)
              counter += 1
  
      def stop_event_loop_default(self):
          """
          Stop an event loop.  This is used to stop a blocking event
          loop so that interactive functions, such as ginput and
          waitforbuttonpress, can wait for events.
  
          Call signature::
  
            stop_event_loop_default(self)
          """
          self._looping = False
  
  
  
  class FigureManagerBase:
      """
      Helper class for matlab mode, wraps everything up into a neat bundle
  
      Public attibutes:
  
      *canvas*
          A :class:`FigureCanvasBase` instance
  
      *num*
          The figure nuamber
      """
      def __init__(self, canvas, num):
          self.canvas = canvas
          canvas.manager = self  # store a pointer to parent
          self.num = num
  
          self.canvas.mpl_connect('key_press_event', self.key_press)
  
      def destroy(self):
          pass
  
      def full_screen_toggle (self):
          pass
  
      def resize(self, w, h):
          'For gui backends: resize window in pixels'
          pass
  
      def key_press(self, event):
  
          # these bindings happen whether you are over an axes or not
          #if event.key == 'q':
          #    self.destroy() # how cruel to have to destroy oneself!
          #    return
  
          if event.key == 'f':
              self.full_screen_toggle()
  
          # *h*ome or *r*eset mnemonic
          elif event.key == 'h' or event.key == 'r' or event.key == "home":
              self.canvas.toolbar.home()
          # c and v to enable left handed quick navigation
          elif event.key == 'left' or event.key == 'c' or event.key == 'backspace':
              self.canvas.toolbar.back()
          elif event.key == 'right' or event.key == 'v':
              self.canvas.toolbar.forward()
          # *p*an mnemonic
          elif event.key == 'p':
              self.canvas.toolbar.pan()
          # z*o*om mnemonic
          elif event.key == 'o':
              self.canvas.toolbar.zoom()
          elif event.key == 's':
              self.canvas.toolbar.save_figure(self.canvas.toolbar)
  
          if event.inaxes is None:
              return
  
          # the mouse has to be over an axes to trigger these
          if event.key == 'g':
              event.inaxes.grid()
              self.canvas.draw()
          elif event.key == 'l':
              ax = event.inaxes
              scale = ax.get_yscale()
              if scale=='log':
                  ax.set_yscale('linear')
                  ax.figure.canvas.draw()
              elif scale=='linear':
                  ax.set_yscale('log')
                  ax.figure.canvas.draw()
  
          elif event.key is not None and (event.key.isdigit() and event.key!='0') or event.key=='a':
              # 'a' enables all axes
              if event.key!='a':
                  n=int(event.key)-1
              for i, a in enumerate(self.canvas.figure.get_axes()):
                  if event.x is not None and event.y is not None and a.in_axes(event):
                      if event.key=='a':
                          a.set_navigate(True)
                      else:
                          a.set_navigate(i==n)
  
  
      def show_popup(self, msg):
          """
          Display message in a popup -- GUI only
          """
          pass
  
      def set_window_title(self, title):
          """
          Set the title text of the window containing the figure.  Note that
          this has no effect if there is no window (eg, a PS backend).
          """
          pass
  
  # cursors
  class Cursors:  #namespace
      HAND, POINTER, SELECT_REGION, MOVE = range(4)
  cursors = Cursors()
  
  
  
  class NavigationToolbar2:
      """
      Base class for the navigation cursor, version 2
  
      backends must implement a canvas that handles connections for
      'button_press_event' and 'button_release_event'.  See
      :meth:`FigureCanvasBase.mpl_connect` for more information
  
  
      They must also define
  
        :meth:`save_figure`
           save the current figure
  
        :meth:`set_cursor`
           if you want the pointer icon to change
  
        :meth:`_init_toolbar`
           create your toolbar widget
  
        :meth:`draw_rubberband` (optional)
           draw the zoom to rect "rubberband" rectangle
  
        :meth:`press`  (optional)
           whenever a mouse button is pressed, you'll be notified with
           the event
  
        :meth:`release` (optional)
           whenever a mouse button is released, you'll be notified with
           the event
  
        :meth:`dynamic_update` (optional)
           dynamically update the window while navigating
  
        :meth:`set_message` (optional)
           display message
  
        :meth:`set_history_buttons` (optional)
           you can change the history back / forward buttons to
           indicate disabled / enabled state.
  
      That's it, we'll do the rest!
      """
  
      def __init__(self, canvas):
          self.canvas = canvas
          canvas.toolbar = self
          # a dict from axes index to a list of view limits
          self._views = cbook.Stack()
          self._positions = cbook.Stack()  # stack of subplot positions
          self._xypress = None  # the  location and axis info at the time of the press
          self._idPress = None
          self._idRelease = None
          self._active = None
          self._lastCursor = None
          self._init_toolbar()
          self._idDrag=self.canvas.mpl_connect('motion_notify_event', self.mouse_move)
          self._button_pressed = None # determined by the button pressed at start
  
          self.mode = ''  # a mode string for the status bar
          self.set_history_buttons()
  
      def set_message(self, s):
          'display a message on toolbar or in status bar'
          pass
  
      def back(self, *args):
          'move back up the view lim stack'
          self._views.back()
          self._positions.back()
          self.set_history_buttons()
          self._update_view()
  
      def dynamic_update(self):
          pass
  
      def draw_rubberband(self, event, x0, y0, x1, y1):
          'draw a rectangle rubberband to indicate zoom limits'
          pass
  
      def forward(self, *args):
          'move forward in the view lim stack'
          self._views.forward()
          self._positions.forward()
          self.set_history_buttons()
          self._update_view()
  
      def home(self, *args):
          'restore the original view'
          self._views.home()
          self._positions.home()
          self.set_history_buttons()
          self._update_view()
  
      def _init_toolbar(self):
          """
          This is where you actually build the GUI widgets (called by
          __init__).  The icons ``home.xpm``, ``back.xpm``, ``forward.xpm``,
          ``hand.xpm``, ``zoom_to_rect.xpm`` and ``filesave.xpm`` are standard
          across backends (there are ppm versions in CVS also).
  
          You just need to set the callbacks
  
          home         : self.home
          back         : self.back
          forward      : self.forward
          hand         : self.pan
          zoom_to_rect : self.zoom
          filesave     : self.save_figure
  
          You only need to define the last one - the others are in the base
          class implementation.
  
          """
          raise NotImplementedError
  
      def mouse_move(self, event):
          #print 'mouse_move', event.button
  
          if not event.inaxes or not self._active:
              if self._lastCursor != cursors.POINTER:
                  self.set_cursor(cursors.POINTER)
                  self._lastCursor = cursors.POINTER
          else:
              if self._active=='ZOOM':
                  if self._lastCursor != cursors.SELECT_REGION:
                      self.set_cursor(cursors.SELECT_REGION)
                      self._lastCursor = cursors.SELECT_REGION
                  if self._xypress:
                      x, y = event.x, event.y
                      lastx, lasty, a, ind, lim, trans = self._xypress[0]
                      self.draw_rubberband(event, x, y, lastx, lasty)
              elif (self._active=='PAN' and
                    self._lastCursor != cursors.MOVE):
                  self.set_cursor(cursors.MOVE)
  
                  self._lastCursor = cursors.MOVE
  
          if event.inaxes and event.inaxes.get_navigate():
  
              try: s = event.inaxes.format_coord(event.xdata, event.ydata)
              except ValueError: pass
              except OverflowError: pass
              else:
                  if len(self.mode):
                      self.set_message('%s : %s' % (self.mode, s))
                  else:
                      self.set_message(s)
          else: self.set_message(self.mode)
  
      def pan(self,*args):
          'Activate the pan/zoom tool. pan with left button, zoom with right'
          # set the pointer icon and button press funcs to the
          # appropriate callbacks
  
          if self._active == 'PAN':
              self._active = None
          else:
              self._active = 'PAN'
          if self._idPress is not None:
              self._idPress = self.canvas.mpl_disconnect(self._idPress)
              self.mode = ''
  
          if self._idRelease is not None:
              self._idRelease = self.canvas.mpl_disconnect(self._idRelease)
              self.mode = ''
  
          if self._active:
              self._idPress = self.canvas.mpl_connect(
                  'button_press_event', self.press_pan)
              self._idRelease = self.canvas.mpl_connect(
                  'button_release_event', self.release_pan)
              self.mode = 'pan/zoom mode'
              self.canvas.widgetlock(self)
          else:
              self.canvas.widgetlock.release(self)
  
          for a in self.canvas.figure.get_axes():
              a.set_navigate_mode(self._active)
  
          self.set_message(self.mode)
  
      def press(self, event):
          'this will be called whenver a mouse button is pressed'
          pass
  
      def press_pan(self, event):
          'the press mouse button in pan/zoom mode callback'
  
          if event.button == 1:
              self._button_pressed=1
          elif  event.button == 3:
              self._button_pressed=3
          else:
              self._button_pressed=None
              return
  
          x, y = event.x, event.y
  
          # push the current view to define home if stack is empty
          if self._views.empty(): self.push_current()
  
          self._xypress=[]
          for i, a in enumerate(self.canvas.figure.get_axes()):
              if x is not None and y is not None and a.in_axes(event) and a.get_navigate():
                  a.start_pan(x, y, event.button)
                  self._xypress.append((a, i))
                  self.canvas.mpl_disconnect(self._idDrag)
                  self._idDrag=self.canvas.mpl_connect('motion_notify_event', self.drag_pan)
  
          self.press(event)
  
      def press_zoom(self, event):
          'the press mouse button in zoom to rect mode callback'
          if event.button == 1:
              self._button_pressed=1
          elif  event.button == 3:
              self._button_pressed=3
          else:
              self._button_pressed=None
              return
  
          x, y = event.x, event.y
  
          # push the current view to define home if stack is empty
          if self._views.empty(): self.push_current()
  
          self._xypress=[]
          for i, a in enumerate(self.canvas.figure.get_axes()):
              if x is not None and y is not None and a.in_axes(event) \
                      and a.get_navigate() and a.can_zoom():
                  self._xypress.append(( x, y, a, i, a.viewLim.frozen(), a.transData.frozen()))
  
          self.press(event)
  
      def push_current(self):
          'push the current view limits and position onto the stack'
          lims = []; pos = []
          for a in self.canvas.figure.get_axes():
              xmin, xmax = a.get_xlim()
              ymin, ymax = a.get_ylim()
              lims.append( (xmin, xmax, ymin, ymax) )
              # Store both the original and modified positions
              pos.append( (
                      a.get_position(True).frozen(),
                      a.get_position().frozen() ) )
          self._views.push(lims)
          self._positions.push(pos)
          self.set_history_buttons()
  
      def release(self, event):
          'this will be called whenever mouse button is released'
          pass
  
      def release_pan(self, event):
          'the release mouse button callback in pan/zoom mode'
          self.canvas.mpl_disconnect(self._idDrag)
          self._idDrag=self.canvas.mpl_connect('motion_notify_event', self.mouse_move)
          for a, ind in self._xypress:
              a.end_pan()
          if not self._xypress: return
          self._xypress = []
          self._button_pressed=None
          self.push_current()
          self.release(event)
          self.draw()
  
      def drag_pan(self, event):
          'the drag callback in pan/zoom mode'
  
          for a, ind in self._xypress:
              #safer to use the recorded button at the press than current button:
              #multiple button can get pressed during motion...
              a.drag_pan(self._button_pressed, event.key, event.x, event.y)
          self.dynamic_update()
  
      def release_zoom(self, event):
          'the release mouse button callback in zoom to rect mode'
          if not self._xypress: return
  
          last_a = []
  
          for cur_xypress in self._xypress:
              x, y = event.x, event.y
              lastx, lasty, a, ind, lim, trans = cur_xypress
  
              # ignore singular clicks - 5 pixels is a threshold
              if abs(x-lastx)<5 or abs(y-lasty)<5:
                  self._xypress = None
                  self.release(event)
                  self.draw()
                  return
  
              x0, y0, x1, y1 = lim.extents
  
              # zoom to rect
              inverse = a.transData.inverted()
              lastx, lasty = inverse.transform_point( (lastx, lasty) )
              x, y = inverse.transform_point( (x, y) )
              Xmin,Xmax=a.get_xlim()
              Ymin,Ymax=a.get_ylim()
  
              # detect twinx,y axes and avoid double zooming
              twinx, twiny = False, False
              if last_a:
                  for la in last_a:
                      if a.get_shared_x_axes().joined(a,la): twinx=True
                      if a.get_shared_y_axes().joined(a,la): twiny=True
              last_a.append(a)
  
              if twinx:
                  x0, x1 = Xmin, Xmax
              else:
                  if Xmin < Xmax:
                      if x<lastx:  x0, x1 = x, lastx
                      else: x0, x1 = lastx, x
                      if x0 < Xmin: x0=Xmin
                      if x1 > Xmax: x1=Xmax
                  else:
                      if x>lastx:  x0, x1 = x, lastx
                      else: x0, x1 = lastx, x
                      if x0 > Xmin: x0=Xmin
                      if x1 < Xmax: x1=Xmax
  
              if twiny:
                  y0, y1 = Ymin, Ymax
              else:
                  if Ymin < Ymax:
                      if y<lasty:  y0, y1 = y, lasty
                      else: y0, y1 = lasty, y
                      if y0 < Ymin: y0=Ymin
                      if y1 > Ymax: y1=Ymax
                  else:
                      if y>lasty:  y0, y1 = y, lasty
                      else: y0, y1 = lasty, y
                      if y0 > Ymin: y0=Ymin
                      if y1 < Ymax: y1=Ymax
  
              if self._button_pressed == 1:
                  a.set_xlim((x0, x1))
                  a.set_ylim((y0, y1))
              elif self._button_pressed == 3:
                  if a.get_xscale()=='log':
                      alpha=np.log(Xmax/Xmin)/np.log(x1/x0)
                      rx1=pow(Xmin/x0,alpha)*Xmin
                      rx2=pow(Xmax/x0,alpha)*Xmin
                  else:
                      alpha=(Xmax-Xmin)/(x1-x0)
                      rx1=alpha*(Xmin-x0)+Xmin
                      rx2=alpha*(Xmax-x0)+Xmin
                  if a.get_yscale()=='log':
                      alpha=np.log(Ymax/Ymin)/np.log(y1/y0)
                      ry1=pow(Ymin/y0,alpha)*Ymin
                      ry2=pow(Ymax/y0,alpha)*Ymin
                  else:
                      alpha=(Ymax-Ymin)/(y1-y0)
                      ry1=alpha*(Ymin-y0)+Ymin
                      ry2=alpha*(Ymax-y0)+Ymin
                  a.set_xlim((rx1, rx2))
                  a.set_ylim((ry1, ry2))
  
          self.draw()
          self._xypress = None
          self._button_pressed = None
  
          self.push_current()
          self.release(event)
  
      def draw(self):
          'redraw the canvases, update the locators'
          for a in self.canvas.figure.get_axes():
              xaxis = getattr(a, 'xaxis', None)
              yaxis = getattr(a, 'yaxis', None)
              locators = []
              if xaxis is not None:
                  locators.append(xaxis.get_major_locator())
                  locators.append(xaxis.get_minor_locator())
              if yaxis is not None:
                  locators.append(yaxis.get_major_locator())
                  locators.append(yaxis.get_minor_locator())
  
              for loc in locators:
                  loc.refresh()
          self.canvas.draw()
  
  
  
      def _update_view(self):
          '''update the viewlim and position from the view and
          position stack for each axes
          '''
  
          lims = self._views()
          if lims is None:  return
          pos = self._positions()
          if pos is None: return
          for i, a in enumerate(self.canvas.figure.get_axes()):
              xmin, xmax, ymin, ymax = lims[i]
              a.set_xlim((xmin, xmax))
              a.set_ylim((ymin, ymax))
              # Restore both the original and modified positions
              a.set_position( pos[i][0], 'original' )
              a.set_position( pos[i][1], 'active' )
  
          self.draw()
  
  
      def save_figure(self, *args):
          'save the current figure'
          raise NotImplementedError
  
      def set_cursor(self, cursor):
          """
          Set the current cursor to one of the :class:`Cursors`
          enums values
          """
          pass
  
      def update(self):
          'reset the axes stack'
          self._views.clear()
          self._positions.clear()
          self.set_history_buttons()
  
      def zoom(self, *args):
          'activate zoom to rect mode'
          if self._active == 'ZOOM':
              self._active = None
          else:
              self._active = 'ZOOM'
  
          if self._idPress is not None:
              self._idPress=self.canvas.mpl_disconnect(self._idPress)
              self.mode = ''
  
          if self._idRelease is not None:
              self._idRelease=self.canvas.mpl_disconnect(self._idRelease)
              self.mode = ''
  
          if  self._active:
              self._idPress = self.canvas.mpl_connect('button_press_event', self.press_zoom)
              self._idRelease = self.canvas.mpl_connect('button_release_event', self.release_zoom)
              self.mode = 'Zoom to rect mode'
              self.canvas.widgetlock(self)
          else:
              self.canvas.widgetlock.release(self)
  
          for a in self.canvas.figure.get_axes():
              a.set_navigate_mode(self._active)
  
          self.set_message(self.mode)
  
  
      def set_history_buttons(self):
          'enable or disable back/forward button'
          pass
  