_            _                 _               _     _            __  __
| |_ _____  _| |_    ___  _   _| |_ _ __  _   _| |_  | |__  _   _ / _|/ _| ___ _ __
| __/ _ \ \/ / __|  / _ \| | | | __| '_ \| | | | __| | '_ \| | | | |_| |_ / _ \ '__|
| ||  __/>  <| |_  | (_) | |_| | |_| |_) | |_| | |_  | |_) | |_| |  _|  _|  __/ |
 \__\___/_/\_\\__|  \___/ \__,_|\__| .__/ \__,_|\__| |_.__/ \__,_|_| |_|  \___|_|
                                   |_|

The text output buffer (TOB) provides a virtual terminal model
emulating a small subset of the traditional DEC VT100. It is
sufficient to support the Termina vocabulary and application
scaffold.

This is intended to be a virtual terminal, with support for the
DEC escape sequence subset used by the termina vocabulary. At
present it does not yet implement most of the needed functions.

DEPENDS:

- konilo

TODO:

- cursor row, col
- improve handling of newlines
- escape sequence support
- separate out attributes to separate buffers

You can create constants for the terminal width & height before
loading the TOB library. If you do not do so, this will create
them for an 80x25 display.

~~~
'TOB:W d:lookup [ #80 'TOB:W const ] -if
'TOB:H d:lookup [ #25 'TOB:H const ] -if
~~~

~~~
'TOB d:create TOB:W TOB:H n:mul #4 n:mul allot

'TX var (col)
'TY var (row)

:scroll (source) &TOB TOB:W n:add
        (dest)   &TOB
        (length) TOB:W TOB:H n:dec n:mul copy
                 &TY v:dec
        (erase)  #32 &TOB TOB:W TOB:H n:dec n:mul n:add TOB:W fill
;

:advance-cursor @TX TOB:W eq? [ #0 !TX &TY v:inc ] if
                @TY TOB:H eq? [ &TY v:dec scroll ] if ;

:handle
  #8   [ ] case
  #127 [ ] case
  #9   [ ] case
  #10  [ #0 !TX &TY v:inc ] case
  #13  [ #0 !TX &TY v:inc ] case
  &TOB TOB:W @TY n:mul n:add @TX n:add store &TX v:inc ;

:tob:put (:c-) handle advance-cursor ;

:tob:display
  &TOB TOB:H [ TOB:W [ fetch-next c:put ] times nl ] times drop ;

:tob:with (:q-) &tob:put &c:put set-hook call &c:put unhook ;

:tob:clear (:-)
  TOB:W TOB:H n:mul [ #32 tob:put ] times #0 !TX #0 !TY ;

tob:clear
~~~