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from Tools.CList import CList
# down up
# Render Converter Converter Source
# a bidirectional connection
class Element:
def __init__(self):
self.downstream_elements = CList()
self.master = None
self.source = None
def connectDownstream(self, downstream):
self.downstream_elements.append(downstream)
if self.master is None:
self.master = downstream
def connectUpstream(self, upstream):
assert self.source is None
self.source = upstream
self.changed()
def connect(self, upstream):
self.connectUpstream(upstream)
upstream.connectDownstream(self)
# we disconnect from down to up
def disconnectAll(self):
# we should not disconnect from upstream if
# there are still elements depending on us.
assert len(self.downstream_elements) == 0, "there are still downstream elements left"
self.source.disconnectDownstream(self)
def disconnectDownstream(self, downstream):
self.downstream_elements.remove(downstream)
if self.master == downstream:
self.master = None
if len(self.downstream_elements) == 0:
self.disconnectAll()
# default action: push downstream
def changed(self, *args, **kwargs):
self.downstream_elements.changed(*args, **kwargs)
def reconnectUpstream(self, new_upstream):
assert self.source is not None
self.source = new_upstream
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