Re: [NTG-context] how to simulate \hss in luametatex?

11 Nov 2022


      Hans,
thank you.
By your and Max's answers, I understand that
there must be box.glueset for the glues in the box.list to actually work.

Best regards

Huang Fusyong(黄复雄)

Hans Hagen via ntg-context  于2022年11月11日周五 18:52写道：
...
On 11/11/2022 10:53 AM, Max Chernoff via ntg-context wrote:
...
Hi,
...
I want to  simulate \hss  in lua end in ConTeXt/luametatex environment.
For example,
```ConTeXt
a{\raise 1.5ex\hbox to 0pt{\hss b}}c
```
...
And in lua, I do as follows(part of my app seen in attachment):
Your code doesn't compile as is. I think that this is the same thing
though:
\starttext
    \startluacode
    local a = node.new"glyph"
    a.char = string.byte("a")
    a.font = font.current()
local b = node.new"glyph"
    b.char = string.byte("b")
    b.font = font.current()
local c = node.new"glyph"
    c.char = string.byte("c")
    c.font = font.current()
local hss = node.new("glue")
    hss.stretch = 65536
    hss.stretchorder = 2
    hss.shrink = 65536
    hss.shrinkorder = 2
    hss.width = 0
    b = node.insertbefore(b, b, hss)
local box = node.new("hlist", "box")
    box.head = b
    box.width = 0
    box.shift = -tex.sp("1ex")
tex.forcehmode()
    node.write(a + box + c)
    \stopluacode
    \stoptext
...
And got 'b' on top of 'c' in pdf as follows:
```pdf
   b
ac
```
The \hss isn't the problem here. The problem is actually with the box.
When you manually make the \hbox like that, I think (although I could be
wrong) that you're bypassing all of TeX's glue calculations. You should
probably use "node.hpack" instead:
\starttext
    \startluacode
    local a = node.new"glyph"
    a.char = string.byte("a")
    a.font = font.current()
local b = node.new"glyph"
    b.char = string.byte("b")
    b.font = font.current()
local c = node.new"glyph"
    c.char = string.byte("c")
    c.font = font.current()
local hss = node.new("glue")
    hss.stretch = 65536
    hss.stretchorder = 2
    hss.shrink = 65536
    hss.shrinkorder = 2
    hss.width = 0
local box = node.hpack(hss + b, "exactly", 0)
    box.shift = -tex.sp("1ex")
tex.forcehmode()
    a.next = box
    box.next = c
    node.write(a)
    \stopluacode
    \stoptext
indeed, an dafter that you can check it
box.glueorder  : 2
  box.glueset    : 6.6683349609375
  box.gluesign   : 2
which will be applied (in the backend) to glues
Hans
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