Adding a vertical bar or other marker to tkinter Text widgets at a particular column

Question

My intention is to add a vertical bar to IDLE to indicate preferred line length at column 80.

I have tried to find a configuration option for the Text tkinter widget that would allow this but have found nothing.

I was hoping it would be a simple configuration option so I could just add a another item the text_options dictionary within EditorWindow.py found within Python\Lib\idlelib.

I am not sure how styles/themes work but do they have the capability to change the background colour of only 1 column in a Text widget?

What is a "column bar"? And are you wanting to add it to IDLE or to a program you are writing? — Bryan Oakley, Feb 18 '17 at 02:26
Text widgets don't have columns, so no, you can't change the background of a column. — Bryan Oakley, Feb 18 '17 at 02:28
Set column=80 in vim, rulers in vscode. It just indicates preferred line length. I want to extend IDLE so it contains this line/bar. — stevenhuyn, Feb 18 '17 at 02:29
http://stackoverflow.com/questions/2447109/showing-a-different-background-colour-in-vim-past-80-characters. Thanks for the info. — stevenhuyn, Feb 18 '17 at 02:38
I think a better title would be "Adding a vertical bar or other marker to tkinter Text widgets at a particular column". (You must mean 'column 80', not 'line 80'.) — Terry Jan Reedy, Feb 19 '17 at 21:31

score 0 · Accepted Answer · answered Feb 19 '17 at 22:30

Outline of possible solution:

Create a 1-pixel wide Frame, with a contrasting background color, as a child of the Text.
Use .place() to position the Frame at an appropriate horizontal coordinate.

Possible issues:

I don't see any easy way to get the coordinate for a particular column. Text.bbox("1.80") looks promising, but doesn't work unless there actually are 80 characters in the line already. You may have to insert a dummy 80-character line at first, call update_idletasks to get the Text to calculate positions, call bbox to get the coordinates, then delete the dummy text. Repeat whenever the display font is changed.
The line would necessarily appear on top of any text or selection region, which isn't quite the visual appearance I'd expect for a feature like this.

Adding a vertical bar or other marker to tkinter Text widgets at a particular column

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