bugFree UCS Outline Fonts - Bugs: bug #26804, Musical Symbols: font feature...


bug #26804: Musical Symbols: font feature lookups by script

Submitter:  Steve White <Stevan_White>
Submitted:  Sun 14 Jun 2009 12:12:57 PM UTC
Category:  character range Severity:  2 - Minor
Item Group:  character substitution issue Status:  Need info
Privacy:  Public Assigned to:  Stevan_White
Open/Closed:  Open Release:  * development
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Thu 30 Nov 2017 11:20:10 PM UTC, comment #2: 

From a discussion with David Corbett, regarding positioning of combining tremolos on notes with stems:

"... with HarfBuzz, the shaper applies NFC... It would have been nice if NFC put the stem before the tremolo.

Uniscribe doesn’t apply NFC. It also doesn’t seem to apply 'kern', 'mark', or other lookups for musical symbols."

Steve White <Stevan_White>
Group administrator
Sat 04 Sep 2010 11:40:56 PM UTC, comment #1: 

FontForge warning (v 20090923)

"On Windows many apps will have problems with this font's kerning, because because 58 of its glyph kern pairs cannot be mapped to unicode-BMP kern pairs"

This was due to trying to use kerns in Musical range, which is not in the Basic Multilingual Plane (is above u+FFFF).

Steve White <Stevan_White>
Group administrator
Sun 14 Jun 2009 12:12:57 PM UTC, original submission:  

So far, have found very limited success in getting font features to work in the Musical Symbols range.  This affects at least bug reports:

bug #26803: Musical Symbols: Begin/End Beam, Phrase, Slur, Tie]

bug #26801: Musical Symbols: combining articulations in text]

  • In Linux, kerning and mark positioning works, but only in very

specific circumstances
 (I think it's a bug in the text layout engine)

  • Other features (Contextual Alternaties) I tried don't seem to be activated for the Musical Symbols range in Linux.  I know these features work in the same font for other ranges.  What's going on?

  • I don't see any of the features I tried being used in Windows (in web browsers, anyway)

As to why:

  • The question of what level of software is responsible for handling a feature is complicated and system-dependent. 

On Linux, and in some free software such as FireFox, the level is the text-layout library Pango.

  • The question of what feature should be turned on for what script is complex and messy.

 ** OpenType has a special script tag 'musc' to identify the Musical Symbols range.
    OpenType Script Tags

 ** Unicode doesn't specify a special script for Music.  This is
really too bad.  So it gets labelled as "Common".  Unfortunately, this is the way Pango determines its behaviour.
    *ISO 15924
    *Script database

 ** Some font features are script-dependent: For example the 'calt' tag
    'calt' feature description
    says: "not applicable to ideographic scripts"

I think this results in text layout engines not knowing what specific features to apply to music, and only applying a very restricted, but inconsistent, set.

Steve White <Stevan_White>
Group administrator


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    Follows 1 latest change.

    Date Changed by Updated Field Previous Value => Replaced by
    2011-10-28 Stevan_White Severity3 - Normal 2 - Minor

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