def walk_next_selection(obj):
if isinstance(obj, mutable.Selection):
if mutable.iscont(obj.container) and obj.head < obj.last:
return enter_head(obj.container[obj.head])
else:
obj = obj.container
if isinstance(obj, mutable.Document):
return mutable.Selection(obj, len(obj))
index = obj.parent.index(obj)
if mutable.isstruct(obj.parent):
if index + 1 < len(obj.parent):
nxt = obj.parent[index+1]
return enter_head(nxt)
else:
return walk_next_selection(obj.parent)
else:
return mutable.Selection(obj.parent, index+1)
def walk_prev_selection(obj):
if isinstance(obj, mutable.Selection):
if mutable.iscont(obj.container) and obj.head > 0:
return enter_tail(obj.container[obj.head-1])
else:
obj = obj.container
if isinstance(obj, mutable.Document):
return mutable.Selection(obj, 0)
index = obj.parent.index(obj)
if mutable.isstruct(obj.parent):
if index > 0:
nxt = obj.parent[index-1]
return enter_tail(nxt)
else:
return walk_prev_selection(obj.parent)
else:
return mutable.Selection(obj.parent, index)
