bugThe FreeType Project - Bugs: bug #25013, Disabled ligatures should be an...


bug #25013: Disabled ligatures should be an option

Submitted by:  Kriston Rehberg <kjrehberg>
Submitted on:  Thu 04 Dec 2008 09:07:35 PM UTC  
Votes:  1  
Severity:  3 - Normal Item Group:  Hack required
Status:  Invalid Privacy:  Public
Assigned to:  Werner LEMBERG <wl> Open/Closed:  Closed
Planned Release:  None

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Fri 05 Dec 2008 07:47:02 PM UTC, comment #5: 

There are two possibilities to display ligatures:

  (1) You directly use a code point like U+FB03 (ffi).  It
      is impossible to suppress this, except if you
      substitute the glyph with a glyph from another font.

  (2) You disable the ligature mechanism within the font by
      not applying the `liga' or similar features.  This
      could be done in fontconfig, however, I doubt that
      this is the right solution.  The proper way is to
      fix the FreeType autohinter, of course.  Volunteers

Werner LEMBERG <wl>
Project AdministratorIn charge of this item.
Fri 05 Dec 2008 07:25:53 PM UTC, comment #4: 

Do you have any ideas as to where in the rendering chain we might be able to suppress the processing of ligatures for those fonts that might not display well?
Does it appear to you that FreeType and Fontconfig are too far down the chain to be able to suppress ligatures?

Kriston Rehberg <kjrehberg>
Fri 05 Dec 2008 07:11:24 PM UTC, comment #3: 

There are high chances that the autohinter doesn't render these ligature glyphs well.  However, this problem is not special to ligatures per se but can happen with any glyph (well, it shouldn't happen with any glyph...).

Werner LEMBERG <wl>
Project AdministratorIn charge of this item.
Fri 05 Dec 2008 04:16:36 PM UTC, comment #2: 

But if ligatures have nothing to do with Freetype, why does this symptom
completely disappear when I use the native bytecode interpreter?

By the way, DejaVu bugzilla closed this bug as a bug in FreeType.

Kriston Rehberg <kjrehberg>
Thu 04 Dec 2008 10:14:09 PM UTC, comment #1: 

What you want is beyond FreeType.  Our library has no idea about `ligatures'.  You give FreeType a glyph index, and it returns a rendered image of the glyph.

Werner LEMBERG <wl>
Project AdministratorIn charge of this item.
Thu 04 Dec 2008 09:07:35 PM UTC, original submission:  

We need a way to disable ligatures.
There are some fonts, including an extremely popular free font used by all the major Linux distributions, that display malformed ligatures.
We need a way to disable the rendering of ligatures, whether mandatory or discretionary ligatures, because there are fonts that either misconfigure their own ligatures or the Freetype autohinter does not render them correctly.
Either way the end user experience is very poor, especially on a first installation of an operating system like Fedora and Debian.

Kriston Rehberg <kjrehberg>


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    Follow 4 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2008-12-05 kjrehberg Carbon-Copy- => Added kjrehberg
    2008-12-04 wl StatusNone => Invalid
        Assigned toNone => wl
        Open/ClosedOpen => Closed

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