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

25 Jun 2022

      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

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

Benjamin Buchmuller