[XeTeX] Accessing ligatures from FontForge

[Meho R.]

On 22.02.2011 23:36, John Was wrote:
> Hello
>  
> Forgive the puzzlement of a new recruit to FontForge (which is
> installed via Cygwin on a Windows XP machine).  And apologies if this
> isn't the right forum - though frequent discussion of font-related
> issues here gives me hope.
>  
> I edited a font which had just the fi and fl ligatures (in their true
> Unicode positions at FB01 and FB02) and I managed to create tolerable
> versions of the other three standard ligatures (ff, ffi, ffl).  Using
> FontForge I have added these in the slots FB00, FB03, and FB04.  But
> "mapping=tex-text" in the font call (in plain XeTeX) doesn't access
> any of them, neither the two that were there already nor the three
> that I created; however, the standard ` ' `` and '' for opening and
> closing quotations do work so the mapping call is basically
> functioning as normal.  The glyphs are accessible to TeX if I give
> them manually as \char"FB00 etc. but I obviously would like to have
> them delivered automatically as usual.
>  
> I have tinkered with various FontForge menus and had hoped that adding
> 'liga' to the GSUB window would be sufficient, but there is clearly
> something I am not doing right.  Can anyone advise?
>  
> Many thanks
>  
>  
> John
>  
>
>
>
>
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Hi,

Here are some simple observations which, I hope, may be of some use to you.
I assume having \defaultfontfeatures{Ligatures=TeX} activated, of course.

1. Fonts which are missing all ligatures except for "fi" and "fl"
usually get these two "wrong" too, i.e., those are not in their "usual"
places, at U+FB00 and U+FB01, so make sure that you have them at those
positions, or they will not be recognized (compare the resulting TTF
font from the attached .sfd file and the original one).

2. When creating ligatures composed of other ligatures, make sure you
have those also, i.e., to get "ffi" correct, you should have "ff"
created too.

3. When you create, e.g., "ffi" ligature, name it "f_f_i" and add two
liga entries:
    a) f f i
    b) f_f (ff) i
This applies to other "compound" ligatures as well. Having "f f i" only
may not be enough and it's possible that it'll get ignored.

4. The old problem about PDF search unfortunately still remains: only
basic standard ligatures are recognized. I would be happy if someone
knows a way to correct this during font creation or correcting existing
ones.

In the attachment is an example .sfd file for font Neuton.ttf from
http://www.fontsquirrel.com/fonts/neuton to which I added ligatures
"fb", "ff" and "ffh" for testing purposes.
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