Re: [NTG-context] Failure when loading variable font

14 Aug 2021


      On 8/14/2021 5:56 PM, Marcel Krüger via ntg-context wrote:
...
Hi,
the latest ConTeXt version fails for the following
document:
\definefontfeature
       [default:test]
       [default]
       [axis={Weight=100}]
     \definefont
       [SomeFont]
       [file:Fraunces.ttf*default:test]
     \starttext
     \SomeFont Abcdef
     \stoptext
and the font from
https://github.com/undercasetype/Fraunces/raw/master/fonts/Fraunces%5BSOFT%2...
renamed to Fraunces.ttf
with the error message
otf reader      > user instance: weight=100, factors: 0 -1.0 0 0
     otf reader      > fatal error in file 'Fraunces.ttf': ...e0dde776fb1556f32e/formats/luametatex/font-ttf-macro.lua:274: attempt to index a nil value (local 'p1')
     stack traceback:
      ...e0dde776fb1556f32e/formats/luametatex/font-otr-macro.lua:2339: in metamethod 'index'
      ...e0dde776fb1556f32e/formats/luametatex/font-ttf-macro.lua:274: in upvalue 'applyaxis'
      ...e0dde776fb1556f32e/formats/luametatex/font-ttf-macro.lua:1428: in field 'gvar'
      ...e0dde776fb1556f32e/formats/luametatex/font-ttf-macro.lua:1155: in local 'reader'
      ...e0dde776fb1556f32e/formats/luametatex/font-otr-macro.lua:2084: in upvalue 'readtable'
      ...e0dde776fb1556f32e/formats/luametatex/font-otr-macro.lua:2197: in upvalue 'readdata'
      ...e0dde776fb1556f32e/formats/luametatex/font-otr-macro.lua:2252: in function <...e0dde776fb1556f32e/formats/luametatex/font-otr-macro.lua:2235>
      [C]: in function 'xpcall'
      ...e0dde776fb1556f32e/formats/luametatex/font-otr-macro.lua:2341: in upvalue 'loadfont'
      ...e0dde776fb1556f32e/formats/luametatex/font-otr-macro.lua:2396: in field 'loadfont'
      ...mtx/tex/texmf-context/tex/context/base/mkiv/font-otl.lua:160: in field 'load'
      ...mtx/tex/texmf-context/tex/context/base/mkiv/font-otl.lua:599: in upvalue 'otftotfm'
      ...mtx/tex/texmf-context/tex/context/base/mkiv/font-otl.lua:627: in function <...mtx/tex/texmf-context/tex/context/base/mkiv/font-otl.lua:626>
      (...tail calls...)
      ...mtx/tex/texmf-context/tex/context/base/mkxl/font-def.lmt:377: in function <...mtx/tex/texmf-context/tex/context/base/mkxl/font-def.lmt:365>
      (...tail calls...)
      ...mtx/tex/texmf-context/tex/context/base/mkxl/font-def.lmt:483: in field 'read'
      ...mtx/tex/texmf-context/tex/context/base/mkxl/font-ctx.lmt:1336: in function <...mtx/tex/texmf-context/tex/context/base/mkxl/font-ctx.lmt:1193>
      (...tail calls...)
     fonts           > otf loading > loading failed due to read error
(This run used luametatex, but the same issue occurs when using luatex)
The same font worked correctly with the ConTeXt version from 2021-05-20.
that's because since then we check for the cycle (otherwise artifacts)

it probably relates to these extra points (the 'standard' is somewhat 
fuzzy in that respect also because some fonts have them and some don't 
so it's the usual wait till we run into something issue)

we can check for bounds

                         for i=1,nofpoints do
                             local d1, d2, d3 = find(i)
                             local p2 = points[i]
                             if d2 then
                                 xv[i] = xvalues[d2]
                                 yv[i] = yvalues[d2]
                             else
                                 local n1 = dpoints[d1]
                                 local n3 = dpoints[d3]
if n1 > nofpoints then
     n1 = nofpoints
end
if n3 > nofpoints then
     n3 = nofpoints
end

no crash then (the resulting shapes look good enough to me, assumign 
that the weird f is intended)

Hans

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