pysize/ui/gtk/threaded_pysize_tree.py

   1 from threading import Thread
   2 from Queue import Queue
   3 import gobject
   4
   5 from pysize.core.observable import observable
   6 from pysize.core.pysize_fs_tree import pysize_tree
   7 from pysize.core.compute_size import size_observable
   8
   9 # We don't want the building of a tree to block the GUI. A possible
  10 # solution is to periodically call gtk.main_iteration_do() during the
  11 # building. Unfortunately, this introduces reentrance issues when an
  12 # event trigger the building of another tree.
  13 #
  14 # So we build all trees in a single separate thread. This additional
  15 # thread never touches the GUI. So when the GUI wants an updated tree
  16 # it calls threaded_pysize_tree.schedule(), and when the thread finishes
  17 # the tree it wakes the observer that will update the GUI.
  18 #
  19 # As the thread must not touch the GUI, every gtk manipulation must be made
  20 # through a gobject.idle_add(lambda: ...).
  21
  22 # Yeah, we are using threads
  23 gobject.threads_init()
  24
  25 # The only aim of this exception is to unwind the stack in order
  26 # to abort the current building, and quickly procede to the next
  27 # one.
  28 class AbortThisTree(Exception):
  29     pass
  30
  31 class threaded_pysize_tree(object):
  32     def __init__(self):
  33         self.completion = observable()
  34         self.queue = Queue(0)
  35         size_observable.add_observer(self.size_observer)
  36         self.thread = Thread(target=self.run_thread)
  37         self.thread.setDaemon(True)
  38         self.thread.start()
  39
  40     def schedule(self, *args, **kwargs):
  41         self.queue.put((args, kwargs))
  42
  43     # Called for every computed size(), that is, periodically during
  44     # the building of a tree.
  45     def size_observer(self, *args, **kwargs):
  46         if not self.queue.empty():
  47             # The GUI wants another tree, lets stop this one
  48             raise AbortThisTree
  49
  50     def run_thread(self):
  51         while True:
  52             params = self.queue.get()
  53             while not self.queue.empty():
  54                 # Get the last item
  55                 params = self.queue.get_nowait()
  56             (args, kwargs) = params
  57             gobject.idle_add(lambda: self.completion.fire_observers(None))
  58             try:
  59                 tree = pysize_tree(*args, **kwargs)
  60             except AbortThisTree:
  61                 continue
  62             gobject.idle_add(lambda: self.completion.fire_observers(tree))