Re: buffers (append)

[Sietse Brouwer <sbbrouwer@gmail.com>]

Hi Alan,

>> > In addition to \startbuffer \stopbuffer
>> > it would be nice to have \startappendbuffer \stopappendbuffer.
>> >
>> > I see that the lua function buffer.append() exists but I have not
>> > worked-out how to add this functionality cleanly as conTeXt macros.

Here you go!

% We want to join appended pieces with a newline
% but '\n' is a bit rotten to pass inside \ctxlua
% so we simply prepare the appending function inside \startluacode, instead
\startluacode
    userdata = userdata or { }
    function userdata.addTempToBuffer(buffername)
        buffers.append(
            buffername,
            '\n' .. buffers.getcontent('APPENDTEMP')
        )
    end
\stopluacode

\def\startappendbuffer[#1]%
  {% 1: create a \stopappendbuffer that appends APPENDTEMP to the buffer #1
   \def\stopappendbuffer%
      {\ctxlua{userdata.addTempToBuffer('#1')}}
   % 2: write the buffer to APPENDTEMP instead of overwriting buffer #1
   % then addTempToBuffer will take care of the appending.
   \dostartbuffer[APPENDTEMP][startappendbuffer][stopappendbuffer]}


%%% --- And here is an example --- %%%
%%% --- With my respects to Dorothy L. Sayers --- %%%


\setuplayout[backspace=6cm, leftmargin=5cm, width=11cm]
\showframe

\starttext

\startbuffer[x]
\inmargin{Harriet Vane}
Here then at home, by no more storms distrest,
Folding laborious hands we sit, wings furled;
Here in close perfume lies the rose-leaf curled,
Here the sun stands and knows not east nor west,
Here no tide runs; we have come, last and best,
From the wide zone through dizzying circles hurled,
To that still centre where the spinning world
Sleeps on its axis, to the heart of rest.
\stopbuffer

\startlines
\getbuffer[x]
\stoplines

------

\startappendbuffer[x]

\inmargin{Lord Peter Wimsey}
Lay on thy whips, O Love, that we upright,
Poised on the perilous point, in no lax bed
May sleep, as tension at the verberant core
Of music sleeps; for, if thou spare to smite,
Staggering, we stoop, stooping, fall dumb and dead,
And, dying so, sleep our sweet sleep no more.
\stopappendbuffer

\startlines
\getbuffer[x]
\stoplines

------

\typebuffer[x]

\stoptext
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