boxesline-breaking
Under TeX, when I write a line too long, it prints a fat black box at the end
of the line.
That is probably a feature, but I dislike it.
How to turn that OFF? Is there a command-line option or something else?
I usually use LaTeX, but I have a complicated file which happens to be plain TeX.
This is a LuaLaTeX solution. It is a function that gets called just before TeX breaks the text into lines. It inserts ties ~ (only the penalty of 10000, the glue is already there) after the single letter word. Words will still hyphenate (see example below) - as far as I can see (after the w).
[Edit: I have added a check in the code that only letters (L* unicode character class) will be taken into account when preventing a line break after the glyph.]
\documentclass{article}
\usepackage{polski}
\usepackage[polish]{babel}
\usepackage{fontspec}
\usepackage{luatexbase}\usepackage{luacode}
\begin{luacode}
local prevent_single_letter = function (head)
while head do
if head.id == 37 and unicode.utf8.match(unicode.utf8.char(head.char),"%a") then -- a letter
if head.prev.id == 10 and head.next.id == 10 then -- only if we are at a one letter word
local p = node.new("penalty")
p.penalty = 10000
-- This is for debugging only, but then you have to
-- remove the last node.insert_after line:
-- local w = node.new("whatsit","pdf_literal")
-- w.data = "q 1 0 1 RG 1 0 1 rg 0 0 m 0 5 l 2 5 l 2 0 l b Q"
-- node.insert_after(head,head,w)
-- node.insert_after(head,w,p)
node.insert_after(head,head,p)
end
end
head = head.next
end
return true
end
luatexbase.add_to_callback("pre_linebreak_filter",prevent_single_letter,"active~")
\end{luacode}
\begin{document}
\hsize 2.7in
Noc była sierpniowa, ciepła i słodka, Księżyc oświecał srebrnem światłem wgłębienie, tak,
że twarze małego rycerza i Basi były skąpane w blasku.
Poniżej, na podwórzu zamkowem, widać było uśpione kupy żołnierzy, a także i ciała zabitych
podczas dziennej strzelaniny, bo nie znaleziono dotąd czasu na ich pogrzebanie.
\end{document}
BTW: the small hyphenation marks are made with the package showhyphens.
if you want a paragraph skip instead of the indentation then set:
\setlength\parindent{0pt}
\setlength\parskip{\medskipamount}
Best Answer
Since you are using Plain TeX, the answer is
before the text starts.