[lltx] broken dash ligatures

[Ulrike Fischer]

Am Sun, 08 May 2011 23:49:51 +0200 schrieb Stephan Hennig:

> Hi,
> 
> I'm observing broken dash ligatures with certain Microsoft fonts
> (including Cambria).  The attached code tests the -- and --- ligatures
> on a number of fonts distributed by TeX Live, the Google font library
> and Windows 7.  The ligatures work for the TeX Live and Google fonts,
> but fail for all but one Windows 7 fonts (Franklin Gothic Medium).  The
> PDF file can be downloaded at
> <URL:http://home.arcor.de/stephanhennig/Downloads/dashes.pdf>, ca. 200 kB.
> 
> Is this a known problem?

Yes it has been discussed on c.t.t. and I also mentioned it on the
context list. Here a copy of my post two month ago and of Hans'
answer:

"
> On c.t.t. there was a discussion about the TeX-ligatures -- and ---
> for endash and emdash. It seems that the luaotfload/context code
> fails for some font/mode combination: For some fonts +tlig works
> with both modes, some works only with mode=base, and there was also
> a report of font which doesn't work at all (Frutiger LT 55 Roman).
>
> E.g. on my PC +tlig works for Arial (c:/windows/fonts/Arial.ttf)
> tested with a current context minimals only with mode=base.
>
> \font\test="Arial:mode=node;+tlig"
>
> \font\testb="Arial:mode=base;+tlig"
>
> \starttext
>
> \test -- --- abc %fails
>
> \testb -- --- abc %works
>
> \stoptext \bye

this is a side effect of there being two hyphens, think of:

\char 45\char 45
\char173\char173
\char173\char 45
\char 45\char173
\char 45\char 45\char 45
\char173\char173\char173
\char173\char 45\char 45
\char 45\char173\char173

fixed in next beta

Hans

"

-- 
Ulrike Fischer