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