if not modules then modules = { } end modules ['typo-adj'] = {
    version   = 1.001,
    optimize  = true,
    comment   = "companion to typo-adj.mkxl",
    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
    copyright = "PRAGMA ADE / ConTeXt Development Team",
    license   = "see context related readme files"
}

local setdimen          = tex.setdimen
local isdimen           = tex.isdimen
local setmacro          = tokens.setters.macro
local expandmacro       = token.expandmacro

local nuts              = nodes.nuts
local tonut             = nodes.tonut
local getattr           = nuts.getattr
local getdepth          = nuts.getdepth
local getlistdimensions = nuts.getlistdimensions
local getexcept         = nuts.getexcept
local getheight         = nuts.getheight
local getid             = nuts.getid
local getleader         = nuts.getleader
local getlist           = nuts.getlist
local getnext           = nuts.getnext
local getprop           = nuts.getprop
local gettail           = nuts.tail
local getwhd            = nuts.getwhd
local getwidth          = nuts.getwidth
local setattr           = nuts.setattr
local setdepth          = nuts.setdepth
local setexcept         = nuts.setexcept
local setheight         = nuts.setheight
local setlink           = nuts.setlink
local setlist           = nuts.setlist
local setoffsets        = nuts.setoffsets
local setprop           = nuts.setprop
local setstate          = nuts.setstate

local hpacknodes        = nuts.hpack

local hlist_code        <const> = nodes.nodecodes.hlist
local vlist_code        <const> = nodes.nodecodes.vlist

local getbox            = nuts.getbox
local takebox           = nuts.takebox

local new_kern          = nuts.pool.kern
local new_vlist         = nuts.pool.vlist

local flattenleaders    = nuts.flattenleaders
local traverselist      = nuts.traverselist
local traverseleader    = nuts.traverseleader

local a_adaptive        <const> = attributes.private("adaptive")

local registervalue     = attributes.registervalue
local getvalue          = attributes.getvalue
local hasvalues         = attributes.hasvalues
local texsetattribute   = tex.setattribute

local v_right           <const> = interfaces.variables.right

local adaptive          = nodes.adaptive or { }
nodes.adaptive          = adaptive
local enabled           = false

----- enableaction      = nodes.tasks.enableaction

local d_adaptive_width  <const> = isdimen("d_adaptive_width")
local d_adaptive_height <const> = isdimen("d_adaptive_height")
local d_adaptive_depth  <const> = isdimen("d_adaptive_depth")
local d_adaptive_line   <const> = isdimen("d_adaptive_line")

local function setadaptive(w,h,d,l,c,a)
    setdimen(d_adaptive_width,w)
    setdimen(d_adaptive_height,h)
    setdimen(d_adaptive_depth,d)
    setdimen(d_adaptive_line,l)
    setmacro("m_adaptive_color",c)
    setmacro("m_adaptive_alternative",a)
end

local methods = {
    -- overlay
    [1] = function(settings,parent,box)
        local setups = settings.setups
        if setups and setups ~= ""  then
            local w, h, d, s, list = getlistdimensions(parent)
            setadaptive(w,h,d,settings.rulethickness,settings.color,settings.alternative)
            expandmacro("setup",true,setups)
            local l = takebox("b_adaptive_box")
            if l then
                setlist(parent,setlink(l,new_kern(-getwidth(l)),list))
            end
        end
    end
}

adaptive.methods = methods
--------.set     = setadaptive

local function handleuleader(n,grp,index,box,location)
    local m = tonut(n)
    local a = getattr(m,a_adaptive) or index -- index will become a selector
    if a then
        local settings = getvalue(a_adaptive,a) -- index triggers ...
        if settings then
            setstate(m,0) -- hm ...
            local action = methods[settings.method or 1]
            if action then
                action(settings,m,tonut(box))
            end
        end
    end
    return n
end

-- callback.register("handle_uleader", handleuleader) -- will be frozen

function adaptive.set(settings)
    if not enabled then
     -- enableaction("vboxbuilders","nodes.adaptive.handlehorizontal")
     -- enableaction("vboxhandlers","nodes.adaptive.handlevertical")
        callback.register("handle_uleader", handleuleader) -- will be frozen
        enabled = true
    end
    texsetattribute(a_adaptive,registervalue(a_adaptive,settings))
end

interfaces.implement {
    name      = "setadaptive",
    actions   = adaptive.set,
    arguments = {
        {
            { "setups", "string" },
            { "method", "integer" },
            { "mp", "string" },
            { "location", "string" },
            { "color", "string" },
            { "rulethickness", "dimension" },
            { "alternative", "string" },
        }
    }
}

-- The hlist leaders get done before we enter vpacking, so that is where the
-- first call kicks in. Then we do a vpack (so one can indeed also adapt the
-- ht/dp). After packing we know the glue and do the vlist leaders.

-- This is now done via a callback but it is still experimental!

local function handlehorizontal(n)
    if hasvalues(a_adaptive) then
        for _, t, _, l in traverselist(n) do
            if t == hlist_code then
                for m, _, _, ll in traverseleader(l) do
                    local a = getattr(m,a_adaptive)
                    if a then
                        local settings = getvalue(a_adaptive,a)
                        if settings then
                            setstate(m,0)
                            local action = methods[settings.method or 1]
                            if action then
                                action(settings,m,ll)
                            end
                        end
                    end
                end
            end
        end
    end
    return n
end

local function handlevertical(n)
    if hasvalues(a_adaptive) then
        -- not a list just a node
        for _, t, _, l in traverselist(n) do
            if t == vlist_code then
                for m, _, _, ll in traverseleader(l) do
                    local a = getattr(m,a_adaptive)
                    if a then
                        local settings = getvalue(a_adaptive,a)
                        if settings then
                            setstate(m,0)
                            local action = methods[settings.method or 1]
                            if action then
                                action(settings,m,ll)
                            end
                        end
                    end
                end
            end
        end
    end
    return n
end

adaptive.handlehorizontal = handlehorizontal
adaptive.handlevertical   = handlevertical

interfaces.implement {
    name      = "adaptivecheckbox",
    arguments = "integer",
    public    = true,
    protected = true,
    actions   = function(n)
        local b = getbox(n)
        if b and flattenleaders(b) > 0 then
            if getid(b) == hlist_code then
                handlehorizontal(b)
            else
                handlevertical(b)
            end
        end
    end,
}

-- Excepts:
--
-- By using the adaptive uleaders we don't need a callback although we can hook it
-- into the par node and just look at that one instead. However, now we can do it
-- anyplace. Of course this only works per line unless we also look back but that is
-- kind of tricky because then we also need to jump over glue and penalty nodes and
-- compensate for the glue: a mess.

nodes.adaptive.methods[2] = function(settings,parent,box)
    local list = getlist(parent)
    if list then
        local except,
              amount  = getexcept(box)
        local left    = nil
        local right   = nil
        local current = except
        while current do
            local location = getprop(current,"exceptlocation")
            if location == "left" then
                left = current
            elseif location == "right" then
                right = current
            end
            current = getnext(current)
        end
        if not left then
            left  = new_vlist()
            right = new_vlist()
            setprop(left, "exceptlocation","left")
            setprop(right,"exceptlocation","right")
            setlink(left,except,right)
            setexcept(box,left)
            except = left
        end
        -- todo: check for leaks !
        local target = settings.location == v_right and right or left
        -- wrapped in phantom
        local n = getlist(list)
        local nw, nh, nd = getwhd(n)
        local h = hpacknodes(n)
        if getprop(target,"except") then
            nd = getdepth(target) + nh + nd
            setlink(gettail(getlist(target)),h)
        else
            setheight(target,nh)
            setlist(target,h)
            setprop(target,"except",true)
        end
        setdepth(target,nd)
        setexcept(box,except,nd > amount and nd or amount)
        setoffsets(n,target == right and getwidth(box) or -nw)
        setlist(list)
        setlist(real)
    end
end