Drawing from multiple threads

[Matteo Landi <landimatte gmail com>]

Hi all,
these days I'm trying create a very simple spectrum analyzer using gtk
and gstreamer.

Basically there is a method invoked from the outside (gstreamer
thread) notifying me about the presence of a new audio buffer.
Inside this method, I create a new thread which: compute the fft of
the signal, create a Surface, draw the results on it and at the end
queues a redraw of the widget.
Let's see some snippet of code:

class MyWindow():
  def __init__(self):
    ...
    darea = DrawingArea()
    darea.connect('configure', self.configure_cb)
    darea.connect('expose', self.expose_cb)
    ...

  def configure_cb():
     self.surface = ..

  def expose_cb():
     # copy self.surface

  def new_audio_buffer_helper(self, buffer):
    Thread(target=self.new_audio_buffer, args=(buffer,))

  def new_audio_buffer(self, buffer):
    fft = ..
    surface = ..
    # drawing actions
    gobject.idle_add(self.refresh, surface)

  def refresh(self, surface):
    self.surface = surface
    self.queue_draw()

Is this the right way to code in this scenario? Should I protect the
private variable 'surface' even though only the main thread access to
it? Should I need to skip any redrawing actions in order to prevent
potential delay between audio and video?

Thanks in advance.

-- 
Matteo Landi
http://www.matteolandi.net/