pysize/ui/gtk/threaded_pysize_tree.py

   1 # This program is free software; you can redistribute it and/or modify
   2 # it under the terms of the GNU General Public License as published by
   3 # the Free Software Foundation; either version 2 of the License, or
   4 # (at your option) any later version.
   5 #
   6 # This program is distributed in the hope that it will be useful,
   7 # but WITHOUT ANY WARRANTY; without even the implied warranty of
   8 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   9 # GNU Library General Public License for more details.
  10 #
  11 # You should have received a copy of the GNU General Public License
  12 # along with this program; if not, write to the Free Software
  13 # Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  14 #
  15 # See the COPYING file for license information.
  16 #
  17 # Copyright (c) 2006, 2007, 2008  Guillaume Chazarain <guichaz@gmail.com>
  18
  19 from threading import Thread, currentThread
  20 from Queue import Queue
  21 import gobject
  22
  23 from pysize.core.observable import observable
  24 from pysize.core.pysize_fs_tree import pysize_tree
  25 from pysize.core.compute_size import size_observable
  26
  27 # We don't want the building of a tree to block the GUI. A possible
  28 # solution is to periodically call gtk.main_iteration_do() during the
  29 # building. Unfortunately, this introduces reentrance issues when an
  30 # event trigger the building of another tree.
  31 #
  32 # So we build all trees in a single separate thread. This additional
  33 # thread never touches the GUI. So when the GUI wants an updated tree
  34 # it calls threaded_pysize_tree.schedule(), and when the thread finishes
  35 # the tree it wakes the observer that will update the GUI.
  36 #
  37 # As the thread must not touch the GUI, every gtk manipulation must be made
  38 # through a gobject.idle_add(lambda: ...).
  39
  40 # Yeah, we are using threads
  41 gobject.threads_init()
  42
  43 # The only aim of this exception is to unwind the stack in order
  44 # to abort the current building, and quickly procede to the next
  45 # one.
  46 class AbortThisTree(Exception):
  47     pass
  48
  49 class threaded_pysize_tree(object):
  50     def __init__(self):
  51         self.completion = observable()
  52         self.queue = Queue(0)
  53         size_observable.add_observer(self.size_observer)
  54         self.thread = Thread(target=self.run_thread)
  55         self.thread.setDaemon(True)
  56         self.thread.start()
  57
  58     def schedule(self, *args, **kwargs):
  59         self.queue.put((args, kwargs))
  60
  61     # Called for every computed size(), that is, periodically during
  62     # the building of a tree.
  63     def size_observer(self, *args, **kwargs):
  64         if not self.queue.empty() and currentThread() == self.thread:
  65             # The GUI wants another tree, lets stop this one
  66             raise AbortThisTree
  67
  68     def run_thread(self):
  69         while True:
  70             params = self.queue.get()
  71             while not self.queue.empty():
  72                 # Get the last item
  73                 params = self.queue.get_nowait()
  74             args, kwargs = params
  75             gobject.idle_add(lambda: self.completion.fire_observers(None))
  76             try:
  77                 tree = pysize_tree(*args, **kwargs)
  78             except AbortThisTree:
  79                 continue
  80             gobject.idle_add(lambda: self.completion.fire_observers(tree))