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:
   8         def __init__(self):
   9                 self.downstream_elements = CList()
  10                 self.master = None
  11                 self.source = None
  12
  13         def connectDownstream(self, downstream):
  14                 self.downstream_elements.append(downstream)
  15                 if self.master is None:
  16                         self.master = downstream
  17
  18         def connectUpstream(self, upstream):
  19                 assert self.source is None
  20                 self.source = upstream
  21                 self.changed()
  22
  23         def connect(self, upstream):
  24                 self.connectUpstream(upstream)
  25                 upstream.connectDownstream(self)
  26
  27         # we disconnect from down to up
  28         def disconnectAll(self):
  29                 # we should not disconnect from upstream if
  30                 # there are still elements depending on us.
  31                 assert len(self.downstream_elements) == 0, "there are still downstream elements left"
  32
  33                 # Sources don't have a source themselves. don't do anything here.
  34                 if self.source is not None:
  35                         self.source.disconnectDownstream(self)
  36
  37         def disconnectDownstream(self, downstream):
  38                 self.downstream_elements.remove(downstream)
  39                 if self.master == downstream:
  40                         self.master = None
  41
  42                 if len(self.downstream_elements) == 0:
  43                         self.disconnectAll()
  44
  45         # default action: push downstream
  46         def changed(self, *args, **kwargs):
  47                 self.downstream_elements.changed(*args, **kwargs)
  48
  49         def reconnectUpstream(self, new_upstream):
  50                 assert self.source is not None
  51                 self.source = new_upstream