1 #! /usr/bin/env python
 2 # -*- coding: utf-8 -*-
 3 
 4 from matplotlib import pylab as p
 5 from matplotlib.text	import Text
 6 
 7 
 8 class DragHandler(object):
 9  """ A simple class to handle Drag n Drop.
 10 
 11  This is a simple example, which works for Text objects only.
 12  """
 13  def __init__(self, figure=None) :
 14  """ Create a new drag handler and connect it to the figure's event system.
 15  If the figure handler is not given, the current figure is used instead
 16  """
 17 
 18  if figure is None : figure = p.gcf()
 19  # simple attibute to store the dragged text object
 20  self.dragged = None
 21 
 22  # Connect events and callbacks
 23  figure.canvas.mpl_connect("pick_event", self.on_pick_event)
 24  figure.canvas.mpl_connect("button_release_event", self.on_release_event)
 25 
 26  def on_pick_event(self, event):
 27  " Store which text object was picked and were the pick event occurs."
 28 
 29  if isinstance(event.artist, Text):
 30  self.is_dragged = event.artist
 31  self.pick_pos = (event.mouseevent.xdata, event.mouseevent.ydata)
 32  return True
 33 
 34  def on_release_event(self, event):
 35  " Update text position and redraw"
 36 
 37  if self.is_dragged is not None :
 38  old_pos = self.is_dragged.get_position()
 39  new_pos = (old_pos[0] + event.xdata - self.pick_pos[0],
 40  old_pos[1] + event.ydata - self.pick_pos[1])
 41  self.is_dragged.set_position(new_pos)
 42  self.is_dragged = None
 43  p.draw()
 44  return True
 45 
 46 
 47 # Usage example
 48 from numpy import *
 49 
 50 # Create arbitrary points and labels
 51 x, y = random.normal(5, 2, size=(2, 9))
 52 labels = [ "Point %d" % i for i in xrange(x.size)]
 53 
 54 # trace a scatter plot
 55 p.scatter(x, y)
 56 p.grid()
 57 
 58 # add labels and set their picker attribute to True
 59 for a,b,l in zip(x,y, labels):
 60  p.text(a, b, l, picker=True)
 61 
 62 # Create the event hendler 
 63 dragh = DragHandler()
 64 
 65 p.show()
 66 
 67 # vim: set et: