Hyphen character missing when using luatex with DVI output about dvisvgm HOT 5 CLOSED

Looks like \automatichyphenmode=2 (defaults 0) works, but I don't know why.

The LuaTeX dvi outputs with \automatichyphenmode set to 0, 1, and 2 are already different, so the culprit might not be dvisvgm.

\documentclass{article}
\pagestyle{empty}
\def\testhyphens{%
  A-B\par
  -\par
  A-\hspace{0pt}B\par
  A-\par
  -B\par\bigskip}

\begin{document}
\automatichyphenmode=0
\testhyphens

\automatichyphenmode=1
\testhyphens

\automatichyphenmode=2
\testhyphens
\end{document}

Running

lualatex --output-format=dvi dvisvgm-gh255
dviasm dviasm dvisvgm-gh255.dvi > dvisvgm-gh255.dump

then in dvisvgm-gh255.dump

push:
  right: 77pt
  down: 63pt
  fnt: [...] at 10pt
  set: '\x1b"'
pop:
push:
  right: 77pt
  down: 75pt
  set: '@'
pop:
push:
  right: 77pt
  down: 87pt
  set: '\x1b@"'
pop:
push:
  right: 77pt
  down: 99pt
  set: '\x1b@'
pop:
push:
  right: 77pt
  down: 111pt
  set: '"'
pop:

push:
  right: 77pt
  down: 135pt
  set: '\x1b"'
pop:
push:
  right: 77pt
  down: 147pt
  set: '@'
pop:
push:
  right: 77pt
  down: 159pt
  set: '\x1b@"'
pop:
push:
  right: 77pt
  down: 171pt
  set: '\x1b@'
pop:
push:
  right: 77pt
  down: 183pt
  set: '@"'
pop:

push:
  right: 77pt
  down: 207pt
  set: '\x1b@"'
pop:
push:
  right: 77pt
  down: 219pt
  set: '@'
pop:
push:
  right: 77pt
  down: 231pt
  set: '\x1b@"'
pop:
push:
  right: 77pt
  down: 243pt
  set: '\x1b@'
pop:
push:
  right: 77pt
  down: 255pt
  set: '@"'
pop:

You can see the first and last line of each test group with \automatichyphenmode=2 are different from when \automatichyphenmode is set to other values.

from dvisvgm.

@muzimuzhi Awesome, thank you for the detailed analysis!

dvisvgm indeed converts the DVI files correctly. The initial one created by LuaTeX doesn't contain the missing hyphens so that dvisvgm can't process them.

from dvisvgm.

With lualuatex --output-format=dvi and \automatichyphenmode=(0|1), one also got

Missing character: There is no @ (U+0040) in font nullfont!
Missing character: There is no @ (U+0040) in font nullfont!

(\tracinglostchars=3 can be used to convert them into errors.)

from dvisvgm.

Turns out it's a luaotfload problem, see latex3/luaotfload#270. luaotfload maintainer Marcel Krüger has already kindly pushed a fix to dev branch, which you can test with locally by executing

git clone --branch=dev --depth=1 [email protected]:latex3/luaotfload.git
cd luaotfload
# needs l3build package
l3build install

cd /path/to/tex/files
# needs latex-base-dev and latex-bin-dev packages perhaps
# should be equivalent to "lualatex-dev --output-format=dvi"
dvilualatex-dev dvisvgm-gh255
dvisvgm --font-format=woff2 dvisvgm-gh255

from dvisvgm.

Great, thanks for the detailed explanation and for hunting down that luaotfload issue. I just confirmed that the dev branch for luaotfload does resolve this issue (and the problem I originally had that evolved into the MWE) as you said. I'll close this as the issue is in luaotfload and already fixed pending release. Thanks again.

from dvisvgm.