[NTG-pdftex] [ pdftex-Feature Requests-715 ] highlight ligatures

noreply at sarovar.org noreply at sarovar.org
Fri Dec 22 14:08:59 CET 2006

Feature Requests item #715, was opened at 2006-12-22 10:48
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Uli Laube (ulilaube)
Assigned to: Nobody (None)
Summary: highlight ligatures

Initial Comment:

>From time to time people in de.comp.text.tex ask for a
solution to remove ligatures from german words
automatically. As this requires quite some knowledge of
the morphology of the german language, packages like 
rmligs  or  ligatex  use lists of words to remove
unwanted ligatures. As this depends on the ligatures
available in the font used, it is quite troublesome to
the compile the lists.

I'am proposing the following addtion to be incorporated
into pdftex: highlighting of the ligatures.

If enabled pdftex uses a bold version of the font when
it inserts ligatures in normal text and vice versa.
Like /em and /emph work for italic text. This would
allow the user of pdftex to prepare a draft copy of the
document were all ligatures are highlighted and can be
easily spotted. The user can then insert "| manually to
remove the unwanted ligatures.

Kind Regards and Happy Holidays

Uli Laube


>Comment By: Hartmut Henkel (hhenkel)
Date: 2006-12-22 14:08

Logged In: YES 

...an example .vpl file with colorchange command:

   (CHARWD R 0.777781)
   (CHARHT R 0.683332)
      (SPECIAL pdf:direct: 0.486 0.104 0.291 rg)
      (SETCHAR O 2)
      (SPECIAL pdf:direct: 0 0 0 rg)

Regards, Hartmut


Comment By: Hartmut Henkel (hhenkel)
Date: 2006-12-22 13:55

Logged In: YES 

For highlighting a boldface font is needed that has the same
metrics as the non-highlighted one, to keep paragraph
breaking unchanged.

What you can do right now is to generate a virtual font that
contains colored ligatures! It is in fact possible to add
PDF color change command specials into the .vpl virtual
property list files of the virtual font, These commands will
then be inserted into the PDF page stream in front of the

But also some solution on engine level should be doable.

Regards, Hartmut


Comment By: Uli Laube (ulilaube)
Date: 2006-12-22 11:22

Logged In: YES 

If a document uses different fonts, they might have
different ligatures available. The special font and the
macro packages might not be aware of this. As far as I know,
the insertion of ligatures happens late when the .dvi oder
.pdf is created. My hope is that switching to the bold
version of the font when a ligature is inserted might be a
way to have this feature work for all fonts. 


Comment By: Frank Küster (frank)
Date: 2006-12-22 11:08

Logged In: YES 

Since ligatures are inserted according to information in the
fonts, I think this should be implemented as a combination
of a special font (which uses noticeably different glyphs
for ligatures), and a macro package that switches fonts.


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