I have prepared a plain example (attached) which can be run with
mtxrun --script plain --run test.tex
and also segfaults.
On 1/16/19 10:14 PM, Henri Menke wrote:
> Dear list,
>
> To answer a question on TeX.SX I wanted to compare glyph sidebearings
> using kerns. However, when trying to insert a kern before the head of
> the last line I first get an error followed by segmentation fault:
>
> warning (node filter): error: [\directlua]:12: Attempt to
> node.insert_before() a non-existing node
>
> Segmentation fault
>
> The example is attached because it's a bit larger. I marked the
> offending line with “BOOM”.
>
> Cheers, Henri
>
\font\1="[lmsans10-bold.otf]" at 60pt
\def\Huge{\1\baselineskip=72pt\relax}
\def\raggedleft{%
\parindent=0pt
\parfillskip=0pt
\rightskip=0pt
\leftskip=0pt plus 1fil
\relax
}
\def\raggedright{%
\parindent=0pt
\parfillskip=0pt
\leftskip=0pt
\rightskip=0pt plus 1fil
\relax
}
\newcount\dropsidebearings
\begingroup
\catcode`\^^M=12
\directlua{
local function drop_sidebearing(head, groupcode)
if tex.count['dropsidebearings'] == 0 then
return true
end
for n in node.traverse_id(node.id'hlist', head) do
local char = node.has_glyph(n.head)
if char then
local f = font.getfont(char.font)
if f.shared then
local kern = node.new(node.id'kern')
kern.kern = f.shared.rawdata.descriptions[char.char].boundingbox[1]*f.size/1000
node.insert_before(n, char, node.copy(kern)) -- BOOM!
node.free(kern)
end
end
for ch in node.traverse_id(node.id'glyph', n.head) do
char = ch
end
if char then
local f = font.getfont(char.font)
if f.shared then
local desc = f.shared.rawdata.descriptions[char.char]
local kern = node.new(node.id'kern')
kern.kern = - (desc.width-desc.boundingbox[3])*f.size/1000
node.insert_after(n, char, node.copy(kern))
node.free(kern)
end
end
local new_list = node.hpack(n.head, n.width, 'exactly')
new_list.head = nil
n.glue_order = new_list.glue_order
n.glue_set = new_list.glue_set
n.glue_sign = new_list.glue_sign
node.free(new_list)
end
return true
end
callback.register('post_linebreak_filter', drop_sidebearing)
}
\endgroup
\def\hairlineiv{%
\leavevmode%
\kern-0.1pt %
\smash{\vrule height 6\baselineskip depth 5pt width 0.1pt}%
\kern-0.1pt
}
\def\hairlinevi{%
\leavevmode%
\kern-0.1pt %
\smash{\vrule depth 6\baselineskip height 2ex width 0.1pt}%
\kern-0.1pt
}
\def\longtitles{Long titles must be exactly aligned with the vertical green bar.}% the main title
Note the {\bf uneven} gap between the text and the green line.
\vskip3\baselineskip
\vbox{\hsize=5in
\dropsidebearings=0 %correction OFF
\raggedleft\Huge \longtitles\hairlineiv\par
}
\eject
Perfect aligment! Each whole line was right shifted by a different amount.
\vskip3\baselineskip
\vbox{\hsize=5in
\dropsidebearings=1 %correction ON
\raggedleft\Huge \longtitles\hairlineiv
}
\vbox{\hsize=5in
\dropsidebearings=1 %correction ON
\raggedright\Huge \hairlinevi\longtitles
}
\bye
