[Bug 1297051] Re: gnome-terminal doesn't recognise C1 controls

[boon]

I've tested the second patch.

RI now works.

I tried OSC ... ST in both the unmixed C1 form and the unmixed ESC form.
They both work.

Hunting around the internet, the unmixed ESC form seems more common. I
am not worried that they wouldn't work in a mixed form. That would be
fairly perverse. I am no expert on the spec but if the C1 forms are
intended to be "equivalent" to the corresponding ESC forms then the
mixed forms _ought_ to work but I am not hassling anyone to support
that.

The C1 form of CSI still works i.e. no regression.

Thanks for your work !

I will wait until it appears in a Ubuntu release.

*****

I noticed a couple of other issues.

1. Resizing of the terminal by the remote host does not work by default.
I was only doing basic resizing (such as would work on a real terminal).

ESC[?3l should get width 80 (that sequence ends with a lower case letter L), and
ESC[?3h should get width 132

(or the equivalent CSI forms).

Looking at the source, it is necessary to send ESC[?40h before either of the above resize sequences will work. Not sure whether that's correct behaviour but I am happy to do that so am adding this comment only in case it helps someone else.
 
2. Answerback does not work

The way answerback is supposed to work is that the remote host sends an
ENQ character (CTRL/E i.e. character with value 0x05) and the terminal
is supposed to send whatever string it has been configured to send,
where that configuration should allow the user to configure to send
control characters so that, at least, the user can configure to send a
trailing carriage return.

(For security reasons, the remote host should not be allowed to set the
answerback message or at least not by default i.e. not without the user
configuring to allow that.  An escape sequence exists for the purpose of
setting the answerback message from the remote host but I think it is
not supported by this emulator anyway.)

Looking at the source, it seems as if it recognises the ENQ but
deliberately sends no response.

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https://bugs.launchpad.net/bugs/1297051

Title:
  gnome-terminal doesn't recognise C1 controls

Status in “vte3” package in Ubuntu:
  New

Bug description:
  gnome-terminal seems not to recognise the C1 control characters.

  The particular character that is a problem for me is CSI. However
  there may be a generic issue with non-support of this whole range of
  characters.

  This range of characters should only be recognised when the encoding
  is a character set that is defined to include the C1 control
  characters but, at a quick look, that is all of the ISO-8859-x
  character sets and Unicode. (C1 control characters require encoding as
  a 2 byte sequence when the encoding is UTF-8. As unlikely as this may
  be to occur in practice, UTF-8 is not inconsistent with C1 control
  characters.)

  Part of the motivation for raising this bug report is that PuTTY seems
  to have declined in reliability recently and so I looked at why I am
  using PuTTY as opposed to gnome-terminal. Correct support of C1
  control characters is one reason. This works in PuTTY. It does not
  appear to work in gnome-terminal. Perhaps resources would be better
  spent making gnome-terminal work as well as PuTTY does, rather than
  attempting to get PuTTY fixed.

  ProblemType: Bug
  DistroRelease: Ubuntu 13.10
  Package: gnome-terminal 3.6.1-0ubuntu6
  ProcVersionSignature: Ubuntu 3.11.0-18.32-generic 3.11.10.4
  Uname: Linux 3.11.0-18-generic x86_64
  NonfreeKernelModules: nvidia
  ApportVersion: 2.12.5-0ubuntu2.2
  Architecture: amd64
  Date: Tue Mar 25 11:08:00 2014
  InstallationDate: Installed on 2011-10-25 (881 days ago)
  InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
  MarkForUpload: True
  SourcePackage: gnome-terminal
  UpgradeStatus: Upgraded to saucy on 2013-11-08 (136 days ago)

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