simon-git: putty (master): Simon Tatham

[Commits to Tartarus hosted VCS]

TL;DR:
  6afa955 Option to support VT100 line drawing in UTF-8 mode.

Repository:     https://git.tartarus.org/simon/putty.git
On the web:     https://git.tartarus.org/?p=simon/putty.git
Branch updated: master
Committer:      Simon Tatham <anakin at pobox.com>
Date:           2018-05-12 08:49:24

commit 6afa955a2ebf017755af134264a9423f54b9351c
web diff https://git.tartarus.org/?p=simon/putty.git;a=commitdiff;h=6afa955a2ebf017755af134264a9423f54b9351c;hp=383302d70ad5ade17e9c451b6468e588d676bbd7
Author: Simon Tatham <anakin at pobox.com>
Date:   Sat May 12 08:43:52 2018 +0100

    Option to support VT100 line drawing in UTF-8 mode.
    
    Thanks to Jiri Kaspar for sending this patch (apart from the new docs
    section, which is in my own words), which implements a feature we've
    had as a wishlist item ('utf8-plus-vt100') for a long time.
    
    I was actually surprised it was possible to implement it in so few
    lines of code! I'd forgotten, or possibly never noticed in the first
    place, that even in UTF-8 mode PuTTY not only accepts but still
    _processes_ all the ISO 2022 control sequences and shift characters,
    and keeps running track of all the same state in term->cset and
    term->cset_attrs that it tracks in IS0-2022-enabled modes. It's just
    that in UTF-8 mode, at the very last minute when a character+attribute
    pair is about to be written into the terminal's character buffer, it
    deliberately ignores the contents of those variables.
    
    So all that was needed was a new flag checked at that last moment
    which causes it not quite to ignore them after all, and bingo,
    utf8-plus-vt100 is supported. And it works no matter which ISO 2022
    sequences you're using; whether you're using ESC ( 0 to select the
    line drawing set directly into GL and ESC ( B to get back when you're
    done, or whether you send a preliminary ESC ( B ESC ) 0 to get GL/GR
    to be ASCII and line drawing respectively so you can use SI and SO as
    one-byte mode switches thereafter, both work just as well.
    
    This implementation strategy has a couple of consequences, which I
    don't think matter very much one way or the other but I document them
    just in case they turn out to be important later:
    
     - if an application expecting this mode has already filled your
       terminal window with lqqqqqqqqk, then enabling this mode in Change
       Settings won't retroactively turn them into the line drawing
       characters you wanted, because no memory is preserved in the screen
       buffer of what the ISO 2022 state was when they were printed. So
       the application still has to do a screen refresh.
    
     - on the other hand, if you already sent the ESC ( 0 or whatever to
       put the terminal _into_ line drawing mode, and then you turn on
       this mode in Change Settings, you _will_ still be in line drawing
       mode, because the system _does_ remember your current ISO 2022
       state at all times, whether it's currently applying it to output
       printing characters or not.

 config.c          |  3 +++
 doc/config.but    | 30 ++++++++++++++++++++++++++++++
 putty.h           |  1 +
 settings.c        |  2 ++
 terminal.c        |  5 +++++
 terminal.h        |  1 +
 windows/winhelp.h |  1 +
 7 files changed, 43 insertions(+)