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

[Benjamin Buchmuller]

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 <Benjamin.Buchmuller at gmail.com> 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 <mseven at telus.net> 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
>