%D \module
%D   [       file=meta-imp-qrcodes,
%D        version=2025.05.27,
%D          title=\METAPOST\ Graphics,
%D       subtitle=QR codes,
%D         author=Hans Hagen,
%D           date=\currentdate,
%D      copyright={PRAGMA ADE \& \CONTEXT\ Development Team}]
%C
%C This module is part of the \CONTEXT\ macro||package and is
%C therefore copyrighted by \PRAGMA. See mreadme.pdf for
%C details.

%D In spring 2025 we played a bit with these codes in the pespective of \TEX\ error
%D reporting, think:
%D
%D \starttyping
%D % signal=qr
%D \stoptyping
%D
%D At \BACHOTEX\ we demonstrates this and Willi Egger made us wooden eartags that
%D had these codes so that those present could scan them. As a follow up on those
%D experiments as well as adding some real time color lightning to a presentation
%D (triggered by \PDF) this signal subsystem was extended with led based status
%D reporting (see signal manual).
%D
%D Here we combine the codes with colors, some trickery that we used for the
%D \CONTEXT\ 2025 meeting website. At that meeting more signals will be revealed.
%D
%D The variant below is different from the \type {\qrcode} command because if goes
%D the \METAPOST\ route and randomizes. I saw no need to bring that into the
%D official macro. After all, this is also a demo of interfacing.

%D We only have one code per page here and use bytemap 0. The original usage was
%D a poster with 30 codes so there we used 30 bytemaps and positioned them on a
%D page.


\startluacode
local random = math.random
local char   = string.char
local gsub   = string.gsub

local qrcodes    = document.qrcodes or { }
document.qrcodes = qrcodes

qrcodegen.bitmap = qrbitmap
figures.qrcode   = qrbitmap

qrcodes.colors = {
    char(200,  0,  0),
    char(  0,200,  0),
    char(  0,  0,200),
    char(  0,200,200),
    char(200,  0,200),
    char(200,200,  0),
}

qrcodes.white = char(230,230,230)

function mp.coloredqrcode(bytemap,index)
    local qrcode   = qrcodes.data and qrcodes.data[index] or tostring(index)
    local qrwhite  = qrcodes.white
    local qrblack  = char(0)
    local qrcolors = qrcodes.colors
    local count    = #qrcolors
    local data, size = qrcodegen.generate(qrcode)
    data = gsub(data,"(.)",function(c)
        if c == qrblack then
            return qrcolors[random(count)]
        else
            return qrwhite
        end
     end)
     mp.newbytemap(bytemap,size,size,3,data)
end
\stopluacode

\continueifinputfile{meta-imp-qrcodes.mkxl}

\startluacode
document.qrcodes.data = {
[[
Uh, oh. A little while ago one of the quantities that I was computing got too
large, so I'm afraid your answers will be somewhat askew. You'll probably have to
adopt different tactics next time. But I shall try to carry on anyway.
]],

[[
The equation I just processed has given some variable a value outside of the
safetyp range. Continue and I'll try to cope with that big value.
]],


[[
A funny symbol that I can't read has just been input. Continue, and I'll forget
that it ever happened.
]],

[[
Recursive macro expansion cannot be unlimited because of runtime stack
constraints. The limit is 10000 recursion levels in total.
]],

[[
I'm not currently working on a for loop, so I had better not try to end anything.
]],

[[
Sorry ... I've converted what follows to tokens, possibly garbaging the name you
gave. Please delete the tokens and insert the name again.
]],

[[
I didn't find a variable name at the left of the ':=', so I'm going to pretend
that you said '=' instead.
]],

[[
I'm not currently working on a 'begingroup', so I had better not try to end
anything.
]],

[[
Strange: this token has lost its former meaning! I'll read it as a right
delimiter this time.
]],

[[
Division by zero. I'll pretend that you meant to divide by 1.
]],

[[
Continue and I'll round the value until it fits the current numberprecision.
]],

[[
Since I don't take square roots of negative numbers, I'm zeroing this one.
Proceed, with fingers crossed.
]],

[[
Since I don't take logs of non-positive numbers, I'm zeroing this one. Proceed,
with fingers crossed.
]],

[[
The 'angle' between two identical points is undefined. I'm zeroing this one.
Proceed, with fingers crossed.
]],

[[
Tut tut: You're trying to \insert into a \box register that now contains an
\hbox. Proceed, and I'll discard its present contents.
]],

[[
The correction glue for page breaking with insertions must have finite
shrinkability. But you may proceed, since the offensive shrinkability has been
made finite.
]],

[[
I've concluded that your \output is awry.
]],

[[
You can't dump inside a group '{...\dump}' is a no-no.
]],

[[
TeX capacity exceeded, sorry . If you really absolutely need more capacity, you
can ask a wizard to enlarge me.
]],

[[
This can't happen. I'm broken. Please show this to someone who can fix me.
]],

[[
I can't go on meeting you like this. One of your faux pas seems to have wounded
me deeply ... in fact, I'm barely conscious. Please fix it and try again.
]],

[[
The paragraph just ended includes some glue that has infinite shrinkability,
e.g., '\hskip 0pt minus 1fil'. Such glue doesn't belong there --- it allows a
paragraph of any length to fit on one line. But it's safe to proceed, since the
offensive shrinkability has been made finite.)
]],

-- [[
-- You can't use '\hrule' here except with leaders. To put a horizontal rule in an
-- hbox or an alignment, you should use \leaders or \hrulefill (see The TeXbook).
-- ]],

[[
I can't carry out that multiplication or division, since the result is out of range.
]],

[[
Please don't say '\def cs{...}', say '\def cs {...}'. I've inserted an
inaccessible control sequence so that your definition will be completed without
mixing me up too badly.
]],

[[
Double prime script, I'll add a dummy nucleus.
]],

[[
Display math should end with $$. The '$' that I just saw supposedly matches a
previous '$$'. So I shall assume that you typed '$$' both times.
]],

[[
Sorry, Pandora. (You sneaky devil.) I refuse to unbox an \hbox in vertical mode
or vice versa. And I can't open any boxes in math mode.
]],

[[
I can't work with sizes bigger than about 19 feet (45 Theodores as of 2023), 575
centimeters, 2300 Toves, 230 Ediths or 16383 points. Continue and I'll use the
largest value I can.
]],

[[
A one-character control sequence belongs after a ` mark. So I'm essentially
inserting 0 here.
]],

[[
You already have 15 parameters, I'm going to ignore the # sign you just used, as
well the token that followed it.
]],

[[
You meant to type ## instead of #, right? Or maybe a { was forgotten somewhere
earlier, and things are all screwed up? I'm going to assume that you meant ##.
]],

[[
The control sequence at the end of the top line of your error message was never
\def'ed. You can just continue as I'll forget about whatever was undefined.
]],

[[
The control sequence at the end of the top line of your error message was never
\def'ed. You can just continue as I'll forget about whatever was undefined.
]],
}
\stopluacode

\protected\def\stopcoloredqrcode
  {\ctxlua{document.qrcodes.data = { buffers.getcontent("\currentdefinedbuffer") or "" }}%
   \MPcode{lua.mp.coloredqrcode(0,1);draw unitsquare xsized 5cm withbytemap 0;}}

\definebuffer[coloredqrcode]

% \starttext
%     \startTEXpage[offset=1ts]
%         \startcoloredqrcode
%             Many readers will skim over formulas on their first reading of your exposition.
%             Therefore, your sentences should flow smoothly when all but the simplest formulas
%             are replaced by "blah" or some other grunting noise. (Donald Knuth)
%         \stopcoloredqrcode
%     \stopTEXpage
% \stoptext

\starttext

    \startTEXpage[offset=1ts]
        \qrcode[text={Hi, this uses the regular interface!},color=darkred]
    \stopTEXpage

    \startTEXpage[offset=1ts]
        \qrcode[text=Hej,color=darkblue]
    \stopTEXpage

    \startTEXpage[offset=1ts]
        \startcoloredqrcode
            This is just a test using the MetaFun interface!
        \stopcoloredqrcode
    \stopTEXpage

    \startTEXpage[offset=1ts]
        \startcoloredqrcode
            Many readers will skim over formulas on their first reading of your exposition.
            Therefore, your sentences should flow smoothly when all but the simplest formulas
            are replaced by "blah" or some other grunting noise. (Donald Knuth)
        \stopcoloredqrcode
    \stopTEXpage

    \dorecurse{31}{
        \startMPpage
            lua.mp.coloredqrcode(0, #1) ;
            draw unitsquare xsized 5cm withbytemap 0 ;
            setbounds currentpicture to boundingbox currentpicture enlarged 2mm;
        \stopMPpage
    }

\stoptext