lib/python/Components/Element.py

   1 from Tools.CList import CList
   2
   3 # down                       up
   4 # Render Converter Converter Source
   5
   6 # a bidirectional connection
   7 class Element(object):
   8         CHANGED_DEFAULT = 0   # initial "pull" state
   9         CHANGED_ALL = 1       # really everything changed
  10         CHANGED_CLEAR = 2     # we're expecting a real update soon. don't bother polling NOW, but clear data.
  11         CHANGED_SPECIFIC = 3  # second tuple will specify what exactly changed
  12         CHANGED_POLL = 4      # a timer expired
  13
  14         def __init__(self):
  15                 self.downstream_elements = CList()
  16                 self.master = None
  17                 self.source = None
  18                 self.__suspended = True
  19                 self.clearCache()
  20
  21         def connectDownstream(self, downstream):
  22                 self.downstream_elements.append(downstream)
  23                 if self.master is None:
  24                         self.master = downstream
  25
  26         def connectUpstream(self, upstream):
  27                 assert self.source is None
  28                 self.source = upstream
  29                 self.changed((self.CHANGED_DEFAULT,))
  30
  31         def connect(self, upstream):
  32                 self.connectUpstream(upstream)
  33                 upstream.connectDownstream(self)
  34
  35         # we disconnect from down to up
  36         def disconnectAll(self):
  37                 # we should not disconnect from upstream if
  38                 # there are still elements depending on us.
  39                 assert len(self.downstream_elements) == 0, "there are still downstream elements left"
  40
  41                 # Sources don't have a source themselves. don't do anything here.
  42                 if self.source is not None:
  43                         self.source.disconnectDownstream(self)
  44
  45         def disconnectDownstream(self, downstream):
  46                 self.downstream_elements.remove(downstream)
  47                 if self.master == downstream:
  48                         self.master = None
  49
  50                 if len(self.downstream_elements) == 0:
  51                         self.disconnectAll()
  52
  53         # default action: push downstream
  54         def changed(self, *args, **kwargs):
  55                 self.clearCache()
  56                 self.downstream_elements.changed(*args, **kwargs)
  57                 self.clearCache()
  58
  59         def reconnectUpstream(self, new_upstream):
  60                 assert self.source is not None
  61                 self.source = new_upstream
  62
  63         def clearCache(self):
  64                 self.cache = None
  65
  66         def setSuspend(self, suspended):
  67                 changed = self.__suspended != suspended
  68                 if not self.__suspended and suspended:
  69                         self.doSuspend(1)
  70                 elif self.__suspended and not suspended:
  71                         self.doSuspend(0)
  72
  73                 self.__suspended = suspended
  74                 if self.source is not None and changed:
  75                         self.source.checkSuspend()
  76
  77         suspended = property(lambda self: self.__suspended, setSuspend)
  78
  79         def checkSuspend(self):
  80                 self.suspended = reduce(lambda x, y: x and y.__suspended, self.downstream_elements, True)
  81
  82         def doSuspend(self, suspend):
  83                 pass