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Subject: Re: Running texconfig breaks backspace in Bash/MinTTY
To: cygwin AT cygwin DOT com
References: <20160316114546 DOT GO29016 AT dinwoodie DOT org> <56E952E5 DOT 2000205 AT cornell DOT edu> <20160316140012 DOT GP29016 AT dinwoodie DOT org> <56E9769B DOT 5050901 AT cornell DOT edu> <56E9DA19 DOT 4000700 AT towo DOT net> <56EA97AF DOT 8080703 AT cornell DOT edu>
From: Ken Brown <kbrown AT cornell DOT edu>
Message-ID: <56EBE7B4.2010600@cornell.edu>
Date: Fri, 18 Mar 2016 07:34:12 -0400
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On 3/17/2016 7:40 AM, Ken Brown wrote:
> On 3/16/2016 6:11 PM, Thomas Wolff wrote:
>> Am 16.03.2016 um 16:07 schrieb Ken Brown:
>>> On 3/16/2016 10:00 AM, Adam Dinwoodie wrote:
>>>> On Wed, Mar 16, 2016 at 08:34:45AM -0400, Ken Brown wrote:
>>>>> On 3/16/2016 7:45 AM, Adam Dinwoodie wrote:
>>>>>> Here's an interesting bug: normally in a Bash session in MinTTY,
>>>>>> backspace and Ctrl+H both delete the previous character, as expected.
>>>>>> However, after running texconfig and returning to the shell, both the
>>>>>> backspace key and Ctrl+H appear to just print "^H" to the terminal.
>>>>>>
>>>>>> It looks like this is genuinely the terminal trying to render a
>>>>>> backspace character, rather than just backspacing, given the
>>>>>> following:
>>>>>>
>>>>>>      $ printf ^H | xxd
>>>>>>      00000000: 08                                       .
>>>>>>
>>>>>> (To get that, I typed "printf {backspace} | xxd".)
>>>>>>
>>>>>> It's not clear to me whether this is Bash, MinTTY or texconfig that's
>>>>>> misbehaving.  Ctrl+W to delete a word, Ctrl+R to get (for me) fzf's
>>>>>> history search, and using the up and down arrows to navigate
>>>>>> history all
>>>>>> work.  Running Vim, opening a new Bash shell from within the duff 
>>>>>> one,
>>>>>> or SSHing to another box has Ctrl+H working just fine within that
>>>>>> process, but the bugged behaviour resumes when I return to the
>>>>>> original
>>>>>> Bash shell.
>>>>>
>>>>> I can't reproduce this on my system.  I tried 'texconfig --help' and
>>>>> 'texconfig conf'.  What's the precise texconfig command that you
>>>>> used?
>>>>
>>>> I'm just running `texconfig`, with no arguments.  There's a warning
>>>> prompt, that you press Enter to clear, then there's an interactive menu
>>>> that appears -- I'm assuming it's something about that interactive menu
>>>> that's causing the problem.
>>>
>>> In the interactive case, texconfig calls texconfig-dialog, which calls
>>> dialog.
>>>
>>>> Turns out, after some digging, MinTTY's "Keys" > "Backspace sends ^H"
>>>> setting is critical here -- my .minttyrc has `BackspaceSendsBS=yes`, 
>>>> but
>>>> if I remove that line and restart MinTTY, everything works fine.  If I
>>>> add that setting to a fresh Cygwin install that contains only the Base
>>>> packages, texlive-collection-basic, and their dependencies, I can
>>>> reproduce the issue.
>>>>
>>>> That probably explains why you can't reproduce it, but it still seems
>>>> like a bug -- I wouldn't expect backspace behaviour to change in that
>>>> fashion regardless of that bit of configuration.
>>>
>>> So it appears to be a MinTTY/dialog issue.
>> Checking stty -a before and after texconfig reveals that texconfig
>> mangles the stty erase setting and does not restore it.
>> That is clearly a bug of texconfig.
> 
> I'm not sure how you ruled out dialog as the culprit, but in fact you're 
> right. texconfig-dialog calls 'reset' and 'stty sane' at various places, 
> and that seems to be the problem. I'll report this upstream.

I've done this in http://tug.org/pipermail/tex-live/2016-March/037852.html, where you can also see responses by two of the TeX Live developers.

The best long-term solution is to get rid of the need for texconfig by making tlmgr work on Cygwin[*].  In the meantime, upstream TeX Live will consider patches that make texconfig stop messing with terminal settings.  [If it turns out that dialog also messes with terminal settings, then we'll have to find a different workaround.]

Here's one possibility:

--- /usr/share/texmf-dist/scripts/texlive/texconfig-dialog.sh.orig      2015-10-08 16:04:18.000000000 -0400
+++ /usr/share/texmf-dist/scripts/texlive/texconfig-dialog.sh   2016-03-18 07:26:50.708149300 -0400
@@ -43,7 +43,7 @@
   rc=$1
   $needsCleanup && test -n "$tmpdir" && test -d "$tmpdir" \
     && { cd / && rm -rf "$tmpdir"; }
-  termCtl reset
+  termCtl clear
   (exit $rc); exit $rc
 }

Adam, please give this a try and let me know if it solves the problem without creating new ones.

Ken

[*] tlmgr is currently incompatible with the Cygwin packaging of TeX Live.  I'll look into fixing this for TeX Live 2016.  I should be able to simply disable some features of tlmgr, while retaining those that replace the functionality of texconfig.


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