Re: [NTG-context] Count (and limit) glyphs per line?

25 Jun 2022

      Dear list,

A brief follow-up for (1) itemizations [resolved; but question on ConTeXt hsize defaults] and (2) hyphenation [troubles].

(1) To deal with itemizations and other situation where texts are indented such as:

   \setuppapersize[landscape,letter]
   \showframe

   \starttext

	   \samplefile{knuth}

	   \ctxlua{context(tex.dimen["textwidth"])} % 37213340

	   \ctxlua{context(tex.dimen["localhsize"])} % 0

	   \startitemize[width=5em]

	   \item \samplefile{knuth}

	   \ctxlua{context(tex.dimen["textwidth"])} % 37213340

	   \ctxlua{context(tex.dimen["localhsize"])} % 33283340

	   \stopitemize

   \stoptext

The following part in the script must be adapted to the local horizontal size, I guess: 

	if chars >= max_length or width > tex.hsize then

However, tex.localhsize (or tex.dimen["localhsize"]) is 0 when the document is initialized. (Maybe a more sensible default would be textwidth rather than 0?)

So, I added:

	local localhsize = tex.dimen["textwidth"]

	if tex.dimen["localhsize"] > 0 then
		localhsize = tex.dimen["localhsize"]
	end

        if chars >= max_length or width > localhsize then

Maybe someone finds this useful in the future.

(2) I'm (now?) running into trouble with hyphenation. With the example above, I get

"
The separation of any of these four components would have hurt TEX significantly. If I had not partic-
i-
pated fully in all these activities, literally hundreds of improvements would never have been made,
"

In my own document, I also get lines with only a single character or hboxed group. I assume, this is because the hyphen is not counted and pushes the remainder to a new line where the intended breakpoint again starts another one.

Unfortunately, I don't know what to change; I know a bit about "glyph" and "glue", but what is "disc" and would it help here?

Thank you!

Benjamin
...
On Jun 25, 2022, at 11:38, Benjamin Buchmuller  wrote:
Wow, that works like a charm! Thank you, Max!
It's also a very insightful example of how to use and inject Lua code in the TeX output routine. Do you mind if I add it to the wiki? (Probably under "Wrapping".)
Many thanks again!
Benjamin
...
On Jun 24, 2022, at 01:44, Max Chernoff  wrote:
...
I've been confronted with the following 'intriguing' formatting requirement for a document:
"Intriguing" is definitely right here. I suspect these guidelines were made for typewriters and haven't been updated since.
...
to limit the number of glyphs per line to 112.
112 characters per line sounds much too long anyways.
From "The Elements of Typographic Style":
...
Anything from 45 to 75 characters is widely regarded as a satisfactory
length of line for a single-column page set in a serifed text face
in a text size. The 66-character line (counting both letters and
spaces) is widely regarded as ideal. For multiple-column work, a
better average is 40 to 50 characters.
If the type is well set and printed, lines of 85 or 90 characters
will pose no problem in discontinuous texts, such as bibliographies,
or, with generous leading, in footnotes. But even with generous
leading, a line that averages more than 75 or so characters is likely
to be too long for continuous reading.
If you use something like
\setuplayout[width=80\averagecharwidth]
then your lines will for sure have fewer than 112 characters and will probably be more readable too.
...
I'm nevertheless curious if there is a Lua/TeX solution to this "problem"?
Option 1: Use a monospaced font. Then 112 characters per line <=> page width = 112em.
Option 2: A hacky Lua solution
\startluacode
      local max_length = 112
local glyph_id = node.id "glyph"
      local disc_id = node.id "disc"
      local glue_id = node.id "glue"
function userdata.limiter(head)
          language.hyphenate(head)
local chars = 0
          local width = 0
          local n = head
          while n do
              if n.id == glyph_id or n.id == glue_id then
                  chars = chars + 1
                  width = width + n.width - (n.shrink or 0)
              end
if chars >= max_length or width > tex.hsize then
                  local back_chars = 0
                  local end_disc = nil
while n do
                      if n.id == glue_id then
                          local penalty = node.new "penalty"
                          penalty.penalty = -10000
                          node.insertbefore(head, n, penalty)
                          break
                      end
if not end_disc and n.id == disc_id then
                          end_disc = n
                      end
if end_disc and back_chars >= 5 then
                          end_disc.penalty = -10000
                          break
                      end
if n.id == glyph_id then
                          back_chars = back_chars + 1
                      end
n = n.prev
                  end
width = 0
                  chars = 0
              end
n = n.next
          end
return head
      end
nodes.tasks.appendaction(
          "processors",
          "before",
          "userdata.limiter"
      )
  \stopluacode
\setuppapersize[landscape,letter]
  \showframe
\starttext
      \setupalign[flushleft]
\setupbodyfont[14pt]
      \samplefile{knuth}
\setupbodyfont[12pt]
      \samplefile{knuth}
\setupbodyfont[10pt]
      \samplefile{knuth}
\page
      \setupalign[normal]
\setupbodyfont[14pt]
      \samplefile{knuth}
\setupbodyfont[12pt]
      \samplefile{knuth}
\setupbodyfont[10pt]
      \samplefile{knuth}
  \stoptext
This code will ensure that no line ever exceeds "max_length" characters. It uses a greedy algorithm instead of the standard TeX algorithm for line breaking, but it still produces mostly decent results.
-- Max