On 10.02.11 06:25, Taco Hoekwater wrote:

I've created a tracker item, 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. And to consider the fact that \tagcode and \pdfnoligatures are virtually no-ops as an incompatibility sounds like a strong euphemism to me... Of course, one could always use lua code, but if you provide the pdftex commands at all, I think they should function in a sensible way. Regards, -- Robert

On 10.02.11 18:58, Taco Hoekwater wrote:

Which would be an acceptable Compromise, i guess

Yes, OK. Thanks, -- Robert

On 6-9-2011 04:22, Robert wrote:

\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?

I'm pretty sure it has been answered before (but not sure on what lists). I cannot test it here but you should use mode=base which will create a static font that is handled by tex itself as the tex machinery will copy the font data when you do that kind of letterspacing. The engine is ignorant of anything related to the font at the lua end so one might loose some very specific features provided outside the engine but that's no big deal as letterspacing spoils the game anyway. Smallcaps and oldstyles normally are no problem. (So, it's not a luatex bug.) Hans ----------------------------------------------------------------- Hans Hagen | PRAGMA ADE Ridderstraat 27 | 8061 GH Hasselt | The Netherlands tel: 038 477 53 69 | voip: 087 875 68 74 | www.pragma-ade.com | www.pragma-pod.nl -----------------------------------------------------------------

Le 07/09/2011 05:03, Robert a écrit :

On 06.09.11 10:31, Hans Hagen wrote:

...

I cannot test it here but you should use mode=base which will create a static font that is handled by tex itself as the tex machinery will copy the font data when you do that kind of letterspacing. The engine is ignorant of anything related to the font at the lua end so one might loose some very specific features provided outside the engine but that's no big deal as letterspacing spoils the game anyway. Smallcaps and oldstyles normally are no problem.

Thanks, that works. Would you mind elaborating on the difference between base and node mode a bit, or could you point me to the relevant documentation? I'm unable to find anything more specific than that base mode does not support Opentype "fully" (luaotfload). But what exactly is not supported, what would you lose by switching from node to base mode?

If I'm not mistaken, "base mode" implements OT features like traditional TeX fonts, and thus only those features supported by TeX can be used; for instance, simple ligatures or kerning is easily done this way, because those already exist for TFM fonts. But contextual features, for instance, or even simple ligatures with more than two input glyphs, aren't supported this way, because TeX knows nothing about them; there is nothing devoted to them in the way fonts are organised. So you use "node mode", which boils down to inspecting lists of nodes before the paragraph is constructed (in one of the callbacks before linebreak_filter) and changing what must be changed; of course the traditional features can be implemented this way too. As for the documentation, I don't think there is any! Best, Paul

On 07.09.11 08:15, Paul Isambert wrote:

Le 07/09/2011 05:03, Robert a écrit :

...

On 06.09.11 10:31, Hans Hagen wrote:

...

I cannot test it here but you should use mode=base which will create a static font that is handled by tex itself as the tex machinery will copy the font data when you do that kind of letterspacing. The engine is ignorant of anything related to the font at the lua end so one might loose some very specific features provided outside the engine but that's no big deal as letterspacing spoils the game anyway. Smallcaps and oldstyles normally are no problem.

Thanks, that works. Would you mind elaborating on the difference between base and node mode a bit, or could you point me to the relevant documentation? I'm unable to find anything more specific than that base mode does not support Opentype "fully" (luaotfload). But what exactly is not supported, what would you lose by switching from node to base mode?

If I'm not mistaken, "base mode" implements OT features like traditional TeX fonts, and thus only those features supported by TeX can be used; for instance, simple ligatures or kerning is easily done this way, because those already exist for TFM fonts.

But contextual features, for instance, or even simple ligatures with more than two input glyphs, aren't supported this way, because TeX knows nothing about them; there is nothing devoted to them in the way fonts are organised. So you use "node mode", which boils down to inspecting lists of nodes before the paragraph is constructed (in one of the callbacks before linebreak_filter) and changing what must be changed; of course the traditional features can be implemented this way too.

Thanks for the information. I will tell users then to use base mode, for the time being. Probably not surprising, but just for the record (and I guess this won't change, either): The same loss of font features as with \letterspacefont also happens with \pdfcopyfonts. Regards, -- Robert

...

* in pdftex, \letterspacefont does not disable the ligatures, but this is what happens in luatex.

IMO that's a desireable behaviour, not a bug. See Bringhurst, Oliver Simon's _Introduction to Typography_ &c.

A control to turn it off or on (defaulting to disabling the ligatures) would be okay, but I've had to put a lot of effort into turning off ligatures when letterspacing and it's a pain.

In older german texts ligatures are not letter spaced. For example: B i s m a r ck (the ck ligature is not seperated) Patrick

On Feb 10, 2011, at 7:56 AM, Taco Hoekwater wrote:

On 02/10/11 13:53, Patrick Gundlach wrote:

...

...

...

* in pdftex, \letterspacefont does not disable the ligatures, but this is what happens in luatex.

IMO that's a desireable behaviour, not a bug. See Bringhurst, Oliver Simon's _Introduction to Typography_ &c.

A control to turn it off or on (defaulting to disabling the ligatures) would be okay, but I've had to put a lot of effort into turning off ligatures when letterspacing and it's a pain.

In older german texts ligatures are not letter spaced. For example:

B i s m a r ck

(the ck ligature is not seperated)

Neither was ij in dutch, but ff was separated. Which just goes to show you that doing letterspacing automatically is hard....

ck and ij would be (like ae and oe) diphthongs --- linguistic constructs denoting specific sounds. ff is a ligature --- the joining together of two or more characters for stylistic or technical reasons. William -- William Adams senior graphic designer Fry Communications Sphinx of black quartz, judge my vow.

On 02/10/11 14:02, Taco Hoekwater wrote:

On 02/10/11 13:59, William Adams wrote:

...

ck and ij would be (like ae and oe) diphthongs --- linguistic constructs denoting specific sounds.

ff is a ligature --- the joining together of two or more characters for stylistic or technical reasons.

But there is no distinction between those two in OpenType ...

Moral of this: if you want to do nice letterspacing in luatex, use lua code instead of pdftex's \letterspacefont. Best wishes, Taco

Couldn't one create that distinction by how one sets the text?

Directly input the unicode character for the diphthongs, while allowing the ligatures to be constructed by OpenType rules --- that way the diphthongs would be left alone in situations like this, while ligatures would never be made when not appropriate.

But then it would be a matter of the backend, not LuaTeX (except for \letterspacefont), right?

I thought this was the whole point behind the Unicode Consortium choosing not to allocate code points for ligatures.

what about U+FB03 for example? (LATIN SMALL LIGATURE FFI) Perhaps I misunderstood you. Patrick

...

I thought this was the whole point behind the Unicode Consortium choosing not to allocate code points for ligatures.

what about U+FB03 for example? (LATIN SMALL LIGATURE FFI)

As William says, this is for compatibility with a legacy encoding, just as the hundreds of Arabic "presentation forms" that lurk nearby. But, for that matter, this is also the reason for inclusion of the ij ligature (U+0132 LATIN CAPITAL LIGATURE IJ and lowercase U+0133). Arthur