thirddata            = thirddata            or { }
thirddata.drops      = thirddata.drops      or { }

local drops = thirddata.drops

local metafun = context.metafun

local format,todimen = string.format, string.todimen
local floor = math.floor

-- http://lua-users.org/wiki/SimpleRound
local function round(num, idp)
    local mult = 10^(idp or 0)
    return floor(num * mult + 0.5) / mult
end

function drops.numberofpixels(n,idp)
    local dimenfactor = 1/tex.pdfpxdimen
    return round(todimen(n)*dimenfactor,idp)
end

local numberofpixels = drops.numberofpixels


function drops.generate_default_path(id,width,height,radius)

    local w,h,r
    w = numberofpixels(width); h = numberofpixels(height); r = numberofpixels(radius)

    metafun.start()

    metafun("save p,pid; path p; string pid;")

    -- metafun("id := \"drops:boxshadow_w%sh%sr%s\";",w,h,r)
    metafun("pid := \"%s\";",id)
    --metafun("show pid;") -- ok
    metafun("p:= unitsquare xyscaled(%s,%s) smoothed %s;",w,h,r)

    metafun("passvariable(pid,p);")
    metafun("setbounds currentpicture to boundingbox(p);") -- 'activator'; void graphics are ignored

    metafun.stop()

end


function drops.foo(id,width,height,radius)
    drops.generate_default_path(id,width,height,radius)
    inspect(metapost.variables) -- empty here
end