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
   8 def cached(f):
   9         name = f.__name__
  10         def wrapper(self):
  11                 if self.cache is None:
  12                         return f(self)
  13                 if name not in self.cache:
  14                         self.cache[name] = (True, f(self))
  15                 return self.cache[name][1]
  16         return wrapper
  17
  18 class Element(object):
  19         CHANGED_DEFAULT = 0   # initial "pull" state
  20         CHANGED_ALL = 1       # really everything changed
  21         CHANGED_CLEAR = 2     # we're expecting a real update soon. don't bother polling NOW, but clear data.
  22         CHANGED_SPECIFIC = 3  # second tuple will specify what exactly changed
  23         CHANGED_POLL = 4      # a timer expired
  24
  25         def __init__(self):
  26                 self.downstream_elements = CList()
  27                 self.master = None
  28                 self.source = None
  29                 self.__suspended = True
  30                 self.cache = None
  31
  32         def connectDownstream(self, downstream):
  33                 self.downstream_elements.append(downstream)
  34                 if self.master is None:
  35                         self.master = downstream
  36
  37         def connectUpstream(self, upstream):
  38                 assert self.source is None
  39                 self.source = upstream
  40                 self.changed((self.CHANGED_DEFAULT,))
  41
  42         def connect(self, upstream):
  43                 self.connectUpstream(upstream)
  44                 upstream.connectDownstream(self)
  45
  46         # we disconnect from down to up
  47         def disconnectAll(self):
  48                 # we should not disconnect from upstream if
  49                 # there are still elements depending on us.
  50                 assert len(self.downstream_elements) == 0, "there are still downstream elements left"
  51
  52                 # Sources don't have a source themselves. don't do anything here.
  53                 if self.source is not None:
  54                         self.source.disconnectDownstream(self)
  55                         # sources are owned by the Screen, so don't destroy them here.
  56                         self.destroy()
  57
  58         def disconnectDownstream(self, downstream):
  59                 self.downstream_elements.remove(downstream)
  60                 if self.master == downstream:
  61                         self.master = None
  62
  63                 if len(self.downstream_elements) == 0:
  64                         self.disconnectAll()
  65
  66         # default action: push downstream
  67         def changed(self, *args, **kwargs):
  68                 self.cache = { }
  69                 self.downstream_elements.changed(*args, **kwargs)
  70                 self.cache = None
  71
  72         def reconnectUpstream(self, new_upstream):
  73                 assert self.source is not None
  74                 self.source = new_upstream
  75
  76         def setSuspend(self, suspended):
  77                 changed = self.__suspended != suspended
  78                 if not self.__suspended and suspended:
  79                         self.doSuspend(1)
  80                 elif self.__suspended and not suspended:
  81                         self.doSuspend(0)
  82
  83                 self.__suspended = suspended
  84                 if self.source is not None and changed:
  85                         self.source.checkSuspend()
  86
  87         suspended = property(lambda self: self.__suspended, setSuspend)
  88
  89         def checkSuspend(self):
  90                 self.suspended = reduce(lambda x, y: x and y.__suspended, self.downstream_elements, True)
  91
  92         def doSuspend(self, suspend):
  93                 pass
  94
  95         def destroy(self):
  96                 pass