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

24 Jun 2022

      ...
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

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

Max Chernoff