[Dev-luatex] letterspacing and (no) ligatures

[Robert]

Hi Taco,

here's an old issue with \letterspacefont, which I would like to raise 
again and expand upon:

On 10.02.11 18:58, Taco Hoekwater wrote:
> On 10 feb. 2011, at 15:18, Robert<w.m.l at gmx.net>  wrote:
>> On 10.02.11 06:25, Taco Hoekwater wrote:
>>> I've created a tracker item,
[1]
>>> but I am not sure yet whether either of them is actually a bug or
>>> simply a incompatibility.
>>
>> I would call it an incompatibility bug ;-)
>>
>> As others have noted, some ligatures in letterspaced text shouldn't
>> be broken. If \letterspacefont now disables all ligatures, this is
>> no longer possible except by changing the font for each and every
>> such ligature (and even for "--", "<<" etc.). This renders
>> \letterspacefont basically useless.
>>
> That is a convincing argument, i will try to fix \letterspacefont

As has been discovered recently, \letterspacefont will not only break 
ligatures, but also small caps [2,3], and, as it turns out, will in fact 
disable all features of the base font:

\input luaotfload.sty
\font\x="Linux Libertine O:+smcp;+onum"
\x Abcd 0123 (\fontname\font)\par
\letterspacefont\y\x 100
\y Abcd 0123 (\fontname\font)\bye

Now, this would basically mean that \letterspacefont can only be used
for type1, but not for opentype fonts. Is this really intended?


[1] <http://tracker.luatex.org/view.php?id=574>
[2] 
<http://tex.stackexchange.com/questions/27555/lualatex-fontspec-and-tracking-with-microtype>
[3] 
<http://tex.stackexchange.com/questions/26141/textls-breaks-smallcaps-with-luatex>

Best,
-- 
  Robert