Initial checking of Tk-based Python IDE.

Features: text editor with syntax coloring and undo;
subclassed into interactive Python shell which adds history.

Tools/idle/Percolator.py

@@ -0,0 +1,77 @@
+from WidgetRedirector import WidgetRedirector
+from Delegator import Delegator
+
+class Percolator:
+
+    def __init__(self, text):
+        # XXX would be nice to inherit from Delegator
+        self.text = text
+        self.redir = WidgetRedirector(text)
+        self.top = self.bottom = Delegator(text)
+        self.bottom.insert = self.redir.register("insert", self.insert)
+        self.bottom.delete = self.redir.register("delete", self.delete)
+        self.filters = []
+
+    def insert(self, index, chars, tags=None):
+        # Could go away if inheriting from Delegator
+        self.top.insert(index, chars, tags)
+
+    def delete(self, index1, index2=None):
+        # Could go away if inheriting from Delegator
+        self.top.delete(index1, index2)
+
+    def insertfilter(self, filter):
+        # Perhaps rename to pushfilter()?
+        assert isinstance(filter, Delegator)
+        assert filter.delegate is None
+        filter.setdelegate(self.top)
+        self.top = filter
+
+    def removefilter(self, filter):
+        # XXX Perhaps should only support popfilter()?
+        assert isinstance(filter, Delegator)
+        assert filter.delegate is not None
+        f = self.top
+        if f is filter:
+            self.top = filter.delegate
+            filter.setdelegate(None)
+        else:
+            while f.delegate is not filter:
+                assert f is not self.bottom
+                f.resetcache()
+                f = f.delegate
+            f.setdelegate(filter.delegate)
+            filter.setdelegate(None)
+
+
+def main():
+    class Tracer(Delegator):
+        def __init__(self, name):
+            self.name = name
+            Delegator.__init__(self, None)
+        def insert(self, *args):
+            print self.name, ": insert", args
+            apply(self.delegate.insert, args)
+        def delete(self, *args):
+            print self.name, ": delete", args
+            apply(self.delegate.delete, args)
+    from Tkinter import *
+    root = Tk()
+    root.wm_protocol("WM_DELETE_WINDOW", root.quit)
+    text = Text()
+    text.pack()
+    text.focus_set()
+    p = Percolator(text)
+    t1 = Tracer("t1")
+    t2 = Tracer("t2")
+    p.insertfilter(t1)
+    p.insertfilter(t2)
+    root.mainloop()
+    p.removefilter(t2)
+    root.mainloop()
+    p.insertfilter(t2)
+    p.removefilter(t1)
+    root.mainloop()
+
+if __name__ == "__main__":
+    main()