How to debug an unfired tkinter event?

[jfong at ms4.hinet.net]

Peter Otten於 2017年10月19日星期四 UTC+8下午6時04分39秒寫道：
> jfong at ms4.hinet.net wrote:
> 
> > Peter Otten at 2017-10-19 UTC+8 PM 3:24:30 wrote:
> >> It's not clear to me what you mean with this. Did you place the table
> >> from the recipe elsewhere inside a window that you created or did you
> >> make changes in the recipe's code?
> > 
> > Thank you, Peter. I am using Python 3.4.4 under WinXP.
> > 
> > When running the file directly from download, I get a table scrolling
> > vertically only. If its Table class's __init__ parameter
> > "scroll_horizontally" changed to True, it can be scrolled horizontally
> > also. But there is a problem when scrolled horizontally, the header field
> > will not align with data field anymore. I make some modifications to make
> > it does. So far so good.
> > 
> > Later, I want to make the table also has a vertical header. The first step
> > I had taken was to move all 2nd top-level widgets(not much, just four) to
> > right one column further to make room for this new widget. I though it's a
> > simple work, just increase their grid column value by 1. But Murphy's Law
> > comes, the xscrollbar even don't show up when the table was squeezed
> > horizontally.
> 
> Thank you for the clarification; I understand your problem much better now.
> 
> > 
> >> > The canvas has a binding:
> >> >         self.canvas.bind('<Configure>', self._on_canvas_configure)
> >> > 
> >> > After this movement, the callback was only triggered when dragging the
> >> > root widget to resize canvas vertically, but not horizontally.
> >> > 
> >> > Event seems has OS involved(it's MS Windows XP in my case). How to
> >> > debug this kind of problem, under pdb?
> >> 
> >> I don't know, but if you can post a small example script that
> >> demonstrates the problem, and you are lucky, someone will see the
> >> problem.
> > 
> > This is a ~5xx lines file and I think it's not fare to ask forum members
> > to look through it. So I decide to ask for help on how to debug it,
> > instead of the solution.
> > 
> > I try to change the binding to
> >          self.bind_all('<Configure>', self._on_canvas_configure)
> > and add a line into the callback
> >          print(event.widget)
> > 
> > I got some info below each time when I squeeze the table:
> > .
> > .50077776
> > .50077776.50712528
> > .50077776.50712496
> > .50077776.50712464
> > .50077776.50712144
> > .50077776.50712528.50712560.50782256
> > .50077776.50712528.50712560.50782256.50783024
> > .50077776.50712528.50712560.50782256
> > .50077776.50712528.50712560.50782256.50783024
> > 
> > How to change these number(is it a widget ID?) to a meaning name?
> 
> That's the name of the widget in the underlying tcl/tk. You can specify it 
> in Python:
> 
> >>> import tkinter as tk
> >>> print(tk.Button())
> .139817813335904
> >>> print(tk.Button(name="mybutton"))
> .mybutton
> 
> You have to ensure that names are unique.

Thank you. It's very helpful information.

By the way, I just found this problem can be easily seen by not modifing the original file too much with the following steps:

1. copy and get the file from the link.
2. change the "scroll_horizontally" parameter in the "Table" class's __init__ method to "True"

Running it you will see it perform correctly.

3. Change the "column=x" at line 268, 282, 288, 292, 303 to "column=x+1"

Now it has the problem.

--Jach