[Tkinter-discuss] Cursor Index From Tkinter.Text in <KeyRelease> Gives Insconsistent Column, Test Case

jevan at freenet.de jevan at freenet.de
Fri Sep 12 05:32:33 CEST 2014

I want to get the cursor position (line and column) of the insertion point of a Tkinter.Text, but you may assume the answer is easy until you run this simple test run.  Acutally I hope someone finds it easy.

PROBLEM: My text editor project requires a custom undo/redo for Tkinter.Text. I put in the same string for both Test One and Test Two below, but undo does not act consistently due to a inconsistent column variable in KeyRelease event handler given by Tkinter. The problem seems to be that I type too fast for second test which produces a bad column value. Can you help me find the problem?



        Type this string slowly: 'one two three'
        Press F1 to see each word undo.

    Result: Works fine. (For me atleast. Ephasis: type slowly.)


        Type the same string as fast as you can: 'one two three'
        Press F1 to see each word undo.

    Result: Gets the wrong column and does not undo properly. (Restart script and repeat this step if you don't see the error at first, it sometimes works fine with fast typing. I usually get it with 3 to 4 tries at the most.)

QUESTION: Is this a bug in Tkinter, or am I not understanding something specific within Tkinter that would produce consistent columns for my undo/redo records?

from Tkinter import *

class TextView(Text):

    def __init__(self, root):
        Text.__init__(self, root)

        self.history = History(self)
        self.bind("<KeyRelease>", self.keyRelease)

        # used to capture a char at a time in keyRelease.  If space char is pressed it , self.word)

if __name__ == "__main__":
    root = Tk()

    textView = TextView(root)
    root.bind("<F1>", textView.undo)
    root.bind("<F2>", textView.redo)


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