Re: [Qemu-devel] handling SIGWINCH with qemu -nographic

[Rob Landley <rob@landley.net>]

On Monday 15 October 2007 8:15:29 pm Jeff Carr wrote:
> Has anyone looked into finding a way to pass SIGWINCH through to the
> guest? I started looking at linux-user/signal.c.
>
> For those that might not be familiar with SIGWINCH, supporting it
> would allow qemu -nographic to tell when the terminal is a different
> size than 80x24.

The problem is a serial port is essentially a pipe.  You don't get tty 
information about the terminal plugged into the other side, because that's a 
separate machine on the other side of a piece of hardware which doesn't pass 
through that info.  (What _is_ the width and height of a modem?)

Have your program send an ansi probe sequence:

echo -e "\e[s\e[999C\e[999B\e[6n\e[u"

Then parse the return string, which should look something like escape left 
bracket 25 semicolon 80 capital R, and use it to set $LINES=25 and 
$COLUMNS=80.

Any modern terminal program should handle that and spit back a result telling 
you big the tty is (although it doesn't tell you when it _changes_, you have 
to re-probe).  Yes, it's in-band signalling but over a serial connection 
that's all you've got.

Rob
-- 
"One of my most productive days was throwing away 1000 lines of code."
  - Ken Thompson.