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

-- This one is an outlier because the callback has several different calls all over
-- the line break routine. It started out as a tracing feature but can also be used
-- for adding functionality. For performance reasons we assume single usage but that
-- might change. The steps kept the identifiers from tracing: initialize, start,
-- list, stop, collect, line, delete, report, wrapup. The checks parameter is the
-- value of the 'checklinebreaks' integer variable.
--
-- In addition to the overload and tracers usage we now also handle twins with this
-- mechanism but that might change (for instance we could move that to the engine
-- but keep a traced version here.

local checklist                = { }
nodes.handlers.linebreakchecks = checklist

local report      = logs.reporter("linebreaks")
local breakcodes  = tex.breakcodes

checklist[-1] = function(what)
    report("callback %i : %s",what,breakcodes[what])
end

local function check(what,checks,...)
    local check = checklist[checks]
    if check then
        return check(what,checks,...)
    else
        -- invalid one, waste of overhead
    end
end

callback.register("line_break",check)
callback.register("balance",   check)