Dear Hans, I am not quite sure how I shall interpret your response. Unfortunately, I am not an expert for traditional TeX, LuaTex, XeTeX nor the OpenType specs. I am only a user who observed a problem with kerning and is now caught between two stools: the LuaTeX maintainers and the font maintainers. My remarks are below your quotes:
On 3/4/2020 10.43AM, Hans Hagen wrote: > On 3/3/2020 9:43 PM, Matthias Nagel wrote: > > as I am unsure what is the officially correct way to submit a potential > > bug, I post it here and would like to draw your attention to this post, > > because I do not know if the tracker is still in use. > > > > http://tracker.luatex.org/view.php?id=1019 > > > > My apologies, if this is a double posting. Also, I already have posted > > this problem to the Libertinus project as I initially thought this would > > be a bug in the font, but the maintainer of Libertinus said it is an > > issue with LuaTex. > w_j q^j > > the w sticks out of its boundingbox, as does the j ... in traditional > tex font processing the italic correction is always added to the width > and removed in some cases, in opentype it's only added in some cases and > the real width is used (combined with staircase kerning for relative > positioning) If I understand you correctly, you say that the specification how fonts are handled has changed for OpenType fonts in comparison to Type-1 fonts used by pdfTeX. And you say that LuaTex' way to handle things is in accordance with the OpenType specification. Is it correct to say then, that the bug is not in LuaTeX but in the font, although the font designer claim the opposite? In other words, should I again get in touch with the font maintainer and convince them to fix their font? However, XeTeX also uses OpenType and the odd kerning does not appear in XeTeX. Does this imply that Libertinus and XeTeX both handle spacing though not in accordance with the specs, but handle spacing at least consistently with each other? Of course, that would be a very unlucky situation. In that case fixing the font in accordance with the OpenType specs and LuaTeX would break the font for XeTeX. Out of curiosity: Given the assumption that XeTeX and LuaLaTeX handle kerning and spacing of OpenType fonts differently without any indication which of both is compliant to the OpenType specs, why then is it possible to have other OpenType fonts (e.g. Computer Modern Unicode, Tex Gyre) which are typeset correctly for both engines? This does not sound logical for me. If XeTeX and LuaLaTeX behave differently with respect to OpenType kerning/italic correction information, then one should observe this problem in many more cases. > now, the distance between w and j: adding the ic to w would increase the > distance, and even if it were removed later on it would then be too far > apart ... so ... no robust solution for that kind of cases (and we would > start oscillating solutions depending on the bug-of-the-day: fix this, > breaks that, add another flag here and there ... well, that's something > for macro packages to do) ... Well, in my naive view, everything should be fine if all components adhere to the specs. :-o Is it possible to fix the problem on a macro level? If yes, that would be great and I would be deeply thankful, if you could you give me an example macro how to do it. I probably cannot wait with my manuscript until either the font, LuaTeX or XeTeX accepts the problem as „their” bug and fix it. > of course one can apply some "fix feature" > (which i probably would do in context if i'd use that font) that could > either implement a staircase kern, or fix the width Could you enlighten me what a staircase kern is? Is it possible for me to introduce that by myself (whatever it is) or is this something the font maintainer has to do? Matthias > Hans > > ----------------------------------------------------------------- > Hans Hagen | PRAGMA ADE > Ridderstraat 27 | 8061 GH Hasselt | The Netherlands > tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl > ----------------------------------------------------------------- > -- Matthias Nagel Dachtlerstraße 2, 70499 Stuttgart, Deutschland Festnetz: +49-711-25295180, Mobil: +49-151-15998774 E-Mail: matthias.h.na...@posteo.de, Skype: nagmat84, Threema: 86VM8KN7
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