***PLEASE IGNORE THIS FILE***


subclass notes...
# make me a frame/component, so can use in other guis; coding alts:
#    def _makeWidgets(self):
#        self.canvas = Canvas(self, bg=bg)
#        vbar = Scrollbar(self)
#        hbar = Scrollbar(self, orient='horizontal')
#        self.canvas.grid(row=0, column=0)   #.pack(side=TOP,...)
#        vbar.grid(row=0, column=1)   #.pack(side=RIGHT,expand,fill
#        hbar.grid(row=1, colunm=0)   #.pack(side=BOTTOM,...
#
# alt coding:
#   def _drawLevels(self, levels):
#       for i in range(len(levels)):
#           nitems = len(levels[i])
#           for j in range(nitems):
#               node = levels[i][j]
#               if node != None:
#                   rowpos = i * Rowsz
#                   colpos = j * Colsz
# alt coding:
#     addparent = (lambda x, n=node: (x, n))
#     children = map(addparent, children)
#     nextlevel = nextlevel + children
#
# - note that levels is 1 2d array, but only stores _references_
# to parents and children on each level, not copies (== pointers);
# - note that names not startng with '_' are for cient use (convention)
# - note subclassing and wrapper alternatives; subclassing retricts tree
# viewer to one tree type, wrappers don't; embedding/composition;
# wrapper classes abstract interface to a specific kind of tree--
# child lists, labels/vaues, node clicks vary per tree type;
# note that onClick prints more info about node (may not fit in 
# label), and calls wrapper to add more text--parser uses to eval
# subtrees; could also subclass treeviewer to specialize clicks;
# - this fails to define name at end: 
#   import Part2.Lang.parser2
# and package imports require __init__.py at each dir level, even
# last one that contains the .py file (Lang); this works:
#   from Part2.Lang import parser2
# PYTHONPATH must include examples/ dir (contains Part2)
######################################################################



#########################################################################
#??? inheritance vs composition;
# only need  1 viewer for many trees (usually; should allow 1-to-1 too)
# how to make btree in other module use versions here???
#
# ???as is, can't reuse same window for > 1 tree type, since subclass
# viewer itself to spec tree parms; alt: embed a tree interface in
# the viewer instead
#
# class TreeViewEmpty:
#     def children(self):
#         return None
# 
# class TreeViewNode:
#     def label(self):
#         return None
#     def value(self):
#         return None
#     def children(self):
#         assert(0, 'TreeView trees must provide a children() method')
#
# 
#     class BinaryNode(btree.BinaryNode, TreeViewNode):
#         def children(self):
#             return [self.left, self.right]
#         def label(self):
#             return self.data
# 
#     class EmptyNode(btree.EmptyNode, TreeViewEmpty): pass