bugGNU nano - Bugs: bug #60369, cursor jumps four places when...

 
 

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bug #60369: cursor jumps four places when stepping leftward from the 9th character

Submitter:  Nick Anderegg <nickanderegg>
Submitted:  Sat 10 Apr 2021 10:24:35 PM UTC
   
 
Severity:  3 - Normal Status:  Need Info
Assigned to:  None Open/Closed:  Closed

Wed 28 Apr 2021 08:06:14 AM UTC, comment #3: 

Closing, due to lack of information.

Benno Schulenberg <bens>
Group administrator
Tue 20 Apr 2021 09:22:59 AM UTC, comment #2: 

Any more info on this issue?

Benno Schulenberg <bens>
Group administrator
Sun 11 Apr 2021 10:19:09 AM UTC, comment #1: 

Only on a certain, remote machine?  You cannot reproduce it locally?  That makes it sound like a discrepancy between the terminal description available on the remote machine and what your local terminal is actually capable of.  What terminal are you using?  And can you reproduce it also when using a different terminal?  For example a plain Linux console (VT) or a real xterm?

As you say that the issue hasn't been occurring for very long, it may also be that you have an old version of ncurses on the remote machine and a few months ago I removed two workarounds for older ncurses.  What version of libncurses does the remote machine have?  And if you could test nano-5.3 and nano-5.4 on that remote machine, then the former should work fine and only the latter should show the problem.

That the problem does not occur when using --constantshow or --minibar makes sense, because then the bottom bar gets redrawn for every keystroke, which means that afterward the cursor gets placed afresh in the text, and for such a jump ncurses uses a cursor-positioning command, which should work fine on any terminal and with any version of ncurses.  It is when making small cursor movements that ncurses uses trickery to reduce the number of bytes sent to the terminal, and this can backfire when the terminal description does not exactly match what the terminal can actually do, or when the terminal's tabsize on your remote and local machines differ.

Benno Schulenberg <bens>
Group administrator
Sat 10 Apr 2021 10:24:35 PM UTC, original submission:  

On a certain machine (when connected over SSH), if I am moving the cursor leftward on a line, when I move from the (zero-indexed) 9th cursor position to the 8th cursor position, the cursor will move four additional positions to the left.

From that point, if the cursor is moved further to the left, moving the cursor rightward will cause characters to be rendered starting with the position where the cursor jumped to.

I have attached a gif showing this occurring after running the command `nano --ignorercfiles /etc/nanorc`, with the name `nano_jumpiness.gif`. Here's an additional link to the gif: https://d.pr/i/o4DQGx

This bug stops occurring if I launch nano with either of the `--constantshow` or `--minibar` flags. This issue hasn't been occurring for very long, so I suspect it's related to the recent changes to the behavior of these flags.


Nick Anderegg <nickanderegg>

 

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    Follow 8 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2021-04-28 bens Open/ClosedOpen Closed
    2021-04-23 bens Severity4 - Important 3 - Normal
        Assigned tobens None
    2021-04-20 bens StatusNone Need Info
        SummaryCursor jumps four places when moving leftward past the 9th character cursor jumps four places when stepping leftward from the 9th character
    2021-04-11 bens Severity3 - Normal 4 - Important
        Assigned toNone bens
    2021-04-10 nickanderegg Attached File- Added nano_jumpiness.gif, #51236

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