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

[boon]

On 05/08/14 10:17, Egmont Koblinger wrote:
> which goes something like this:
OK, after a certain amount of guessing and over 1GB of download and 
install, yes, I managed to do that.

It does appear that it is now correctly recognising the CSI character.

However that then reveals another problem. The remote host is assuming 
that the terminal emulator supports the RI (Reverse Index) character 
(code 0x8D). This is another of the C1 controls.

http://en.wikipedia.org/wiki/C0_and_C1_control_codes

The effect is then that, in the editor, the left, right and down arrow 
keys work but the up arrow key does not (because the host is sending an 
RI in response).
> And these days when you watch videos of cats online, who cares about 1 
> more byte?
OK. Fair enough. The performance difference isn't all that significant. :-)

The more fundamental issue is that if a terminal emulator asserts to the 
remote host that it emulates a VT200 series terminal then it needs to do 
so. Because gnome-terminal says that it is a VT200, the remote host is 
entitled to use all of the features of that terminal. In reality much of 
the C1 control set was not standardised or is not used.

I would expect that 0x9D (OSC) and 0x9C (ST) are used and should be 
implemented. OSC, as a synonym for ESC+"]" can probably be done the way 
you have done CSI. Possibly 0x90 (DCS) would be used somewhere.

> Really out of curiosity, could you please name a few of these 
> "built-in programs (for example, the editor)" along with the system 
> they're running on?

The remote system runs the VMS operating system. As VMS was created by 
the same company that created the various VT terminal series, probably 
it is more rigorous in its demands that a VT terminal emulator really 
does emulate correctly. Almost any program under VMS that uses the 
built-in screen handling modules will malfunction if the emulation is 
not accurate.

Regards

Derek

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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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