[gentium] Display Bug in Overleaf and Acrobat

[pavel.farar at centrum.cz]

Hi Tom,

Some glyphs in this release of Gentium have changed from the previous release.
And I am talking about the original TrueType fonts. For example the letter H
used to be just one part, no overlapping, no self-intersection. Now it is
composed of three parts and they overlap.

The image you sent has problems in exactly these areas of letters H, e and d.
The shape of the problems also agrees. Therefore, this must be the reason of
the problems.

However, I can see the problems just in the image. I tried the project at

https://www.overleaf.com/read/cfrckzvbzdmt

but I can't see the problems myself. I use Slackware Linux and I tried firefox
and chromium and there are no artifacts for this document in these browsers. I
also downloaded the PDF and displayed it in okular, xpdf and zathura. I don't
see the problems there neither.

I must find some setup, where I can see the problems. Probably installing
Adobe Reader may help. There seems no support for Linux any more; but I found
some old 32-bit version and it should work in virtual machine. Maybe I will
get an access to some Windows machine.

My question is: Where exactly do you see the problems and where not (OS,
browser, PDF renderer; versions of these)?

The Type 1 fonts were really simply converted in FontForge.

If the fonts are validated in FontForge, there are complaints about
self-intersection and missing points at extrema (and even for the original
TrueType fonts).

Glyphs can be corrected manually using Element / Overlap / Remove Overlap and
it could be probably scripted. So technically, it should be possible to
correct the problems and I believe that it would work. However, the Type 1
fonts must be approved by the author of the original fonts (he must be happy
with the changes and he was not happy with changing just the width of three
letters in the past). For solving the issue the problem should be isolated to
just one thing. If I understand it well, you tried:

1) pdflatex + Type 1
2) lualatex + TrueType

and you viewed the results in Acrobat Reader for both cases. The problem was
just in the first case. However, there are two differences between those
cases: different TeX engine and different type of fonts.

The first thing that I would suggest would be to use pdflatex with the
original TrueType fonts and see if there is the same problem. You can achieve
this by using the map file gentium-truetype.map instead of the default
gentium-type1.map. There can be two results:

1) pdflatex + TrueType fonts give the same problem. Then I wouldn't look for
   the problem just in the converted Type 1 fonts. Even though it could be
   solved by changing the fonts.

2) pdflatex + TrueType fonts give correct document. Then the Type 1 fonts are
   the source of the problem and they should be corrected. As a big bonus you
   would also get correctly working pdflatex. Those using pdflatex would be
   probably happy with the TrueType fonts (I myself use TrueType fonts with
   pdflatex).

If you can try this, than do it, please. That would speed up the thing.

What looks strange to me is that the problems are "at some zoom levels and
some font sizes". I can't imagine reason for this. There is the same font for
all sizes (there are no optical sizes like in Computer Modern). Could you send
an example for this (e.g. bold text in different sizes with and without
problems in the same document).

Pavel