[NTG-context] How to obtain the hbox's node when there is only one hbox for an entire paragraph?

[NTG-context] How to obtain the hbox's node when there is only one hbox for an entire paragraph?

[黄复雄]

Dear list,

What is the non-hacking way to obtain the hbox's node in a Lua hook
when there is only one hbox for an entire paragraph?

Best regards,
Huang Fusyong (黄复雄)

% start ConTeXt

\startluacode
Moduledata = Moduledata or {}
Moduledata.jiazhu = Moduledata.jiazhu or {}

---[[
local function show_detail(n, label)
    local l = label or "======="
    print(">>>>>>>>>"..l.."<<<<<<<<<<")
    print(nodes.toutf(n))
    for i in node.traverse(n) do
        local char
        if i.id == nodes.nodecodes.glyph then
            char = utf8.char(i.char)
            print(i, char)
        elseif i.id == nodes.nodecodes.penalty then
            print(i, i.penalty)
        elseif i.id == nodes.nodecodes.glue then
            print(i, i.width, i.stretch, i.shrink, i.stretchorder,
i.shrinkorder)
        elseif i.id == nodes.nodecodes.hlist then
            print(i,
nodes.toutf(i.list),i.width,i.height,i.depth,i.shift,i.glue_set,i.glue_sign,i.glue_order)
        elseif i.id == nodes.nodecodes.kern then
            print(i, i.kern, i.expension)
        else
            print(i)
        end
    end
end
--]]

function Moduledata.jiazhu.main(head)
    show_detail(head,"head")
    return head, true
end

nodes.tasks.appendaction("processors", "after", "Moduledata.jiazhu.main")

\stopluacode
\starttext

\hbox{a b c}
% The result is as follows (without the <node: hlist box> I expected)：
% >>>>>>>>>head<<<<<<<<<<
% a b c
% <node :    nil <=   3688 =>   3448 : glyph unset>       a
% <node :   3688 <=   3448 =>   3702 : glue spaceskip>    261738
130869  87246   0       0
% <node :   3448 <=   3702 =>   3484 : glyph unset>       b
% <node :   3702 <=   3484 =>   3716 : glue spaceskip>    261738
130869  87246   0       0
% <node :   3484 <=   3716 =>    nil : glyph unset>       c

~\hbox{a b c}
% Hacking with the `~`, the result is as follows (containing the
<node: hlist box> I expected):
% >>>>>>>>>head<<<<<<<<<<
% a b c
% <node :    nil <=   3719 =>   3377 : glyph unset>       a
% <node :   3719 <=   3377 =>   3733 : glue spaceskip>    261738
130869  87246   0       0
% <node :   3377 <=   3733 =>   3491 : glyph unset>       b
% <node :   3733 <=   3491 =>   3747 : glue spaceskip>    261738
130869  87246   0       0
% <node :   3491 <=   3747 =>    nil : glyph unset>       c
% >>>>>>>>>head<<<<<<<<<<
% a b c
% <node :    nil <=   3395 =>   3484 : par vmodepar>
% <node :   3395 <=   3484 =>   2208 : glue indentskip>   0       0
   0       0       0
% <node :   3484 <=   2208 =>   3498 : penalty userpenalty>       10000
% <node :   2208 <=   3498 =>   3325 : glue spaceskip>    261738
130869  87246   0       0
% <node :   3498 <=   3325 =>   3441 : hlist box> a b c   1702476
545484  8646    0       nil     nil     nil<node :   3325 <=   3441 =>
   nil : glue spaceskip>    261738  130869  87246   0       0

\stoptext
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