Re: [Matplotlib-users] Re: Matplotlib-users digest, Vol 1 #521 - 2 msgs

[John H. <jdh...@ac...>]

>>>>> "Steve" == Steve Chaplin <ste...@ya...> writes:
    Steve> I ran the script with GTKCairo and it looks fine to me.

    Steve> Perhaps you are using GTKAgg which looks like it has the
    Steve> problem. My guess is that its caused by using
    Steve> gtk.idle_add() which results in asynchronous expose_event
    Steve> updates.

I looked at this briefly and am a little confused by something.  The
base class FigureCanvasGTK.expose_event has this in the doc string

        """Expose_event for all GTK backends
        Should not be overridden.

but then the derived class 

  class FigureCanvasGTKAgg(FigureCanvasGTK, FigureCanvasAgg):

does in fact override it.

I inserted a debug print statement into
FigureCanvasGTKAgg.expose_event and it is not called until the loop is
over.  I think this is because the call to sleep is preventing the
idle handler from ever getting engaged.

Perhaps Joachim would be better off using a gtk timer to handle his
animation.  Basically, matplotlib tries to provide a GUI neutral way
to do animation (eg anim.py) but if you want to do something
semi-sophisticated like alter the timing between draws, you should use
the GUI specific functionality for this, eg gtk timers.

Here is an example

# animate increasing terms in fourier expansion of y=x
import pygtk
pygtk.require('2.0')
import gtk
import matplotlib
matplotlib.use('GTKAgg')

from matplotlib.numerix import arange, pi, sin, zeros, Float
import pylab


class Animator:
    
    def __init__(self, samples=1000, max_k=30):
        self.samples = samples
        self.max_k   = max_k
        self.fig = pylab.figure()
        self.ax = self.fig.add_subplot(111)
        x = arange(0.0, 1.0, 1.0/self.samples)

        self.s = zeros((self.max_k,samples), Float)


        for k in range(1,self.max_k):
            self.s[k] = self.s[k-1]+(-1)**(k+1)*sin(pi*x*k)/k


        self.line, = self.ax.plot(x, x*1.3, linewidth=1.0)
        self.ax.grid(True)
        self.k = 1

    def draw(self, *args):
        
        self.line.set_ydata(2./pi*self.s[self.k])
        self.ax.set_title('k = '+str(self.k))
        pylab.draw()
        self.k += 1
        return self.k<self.max_k


anim = Animator()
gtk.timeout_add(100,anim.draw)
pylab.show()