Fedora 34 Change: Enable HarfBuzz in FreeType (Self-Contained Change)

[Ben Cotton]

https://fedoraproject.org/wiki/Changes/EnableHarfBuzzInFreeType

== Summary ==
Goal of this feature is to enable usage of HarfBuzz in FreeType to
improve hinting of glyphs of languages which needs more complicated
text shaping.

== Owner ==
* Name: [[User:mkasik| Marek Kašík]]
* Email: <mkasik(a)redhat.com&gt;
* Name: [[User:tagoh| Akira Tagoh]]
* Email: <tagoh(a)redhat.com&gt;


== Detailed Description ==
Hinting of glyphs could be complicated due to many different rules of
how to render sequence of glyphs. Thanks to enablement of HarfBuzz in
FreeType applications will display text with correct hinting of
glyphs.

Usage of HarfBuzz helps us to fix some bugs which are not fixable
without it. Mainly the bug #1853937.

Freetype upstream has already support for HarfBuzz for almost 6 years.

This change was proposed in the bug #1906714.

== Feedback ==
There is the bug #1853937 which can not be solved without this.

== Benefit to Fedora ==
Improved user experience for languages for which Unicode does not list
all variants of all glyphs. These are determined by different signs or
positions in string and their further processing is more difficult.

== Scope ==
* Proposal owners: Enabling usage of HarfBuzz in FreeType means to
handle a circular dependency which is needed due to the nature of
interconnection of these two packages. Maintainers of FreeType and
HarfBuzz will handle this via bootstraping process.

* Other developers: N/A (not needed for this Change)

* Release engineering: N/A (not needed for this Change)

* Policies and guidelines: N/A (not needed for this Change)

* Trademark approval: N/A (not needed for this Change)

* Alignment with Objectives: There will be new dependency of FreeType
on HarfBuzz so the footprint will be a little bigger on systems which
did not need HarfBuzz before.

== Upgrade/compatibility impact ==
Updates should go smooth as this change is limited to FreeType and
Harfbuzz regarding packaging point of view.

== How To Test ==
Install "pango" and "lato-fonts".
Run 'pango-view --markup -t "<span font_desc='Lato 8'>8pt t ti fi
tt</span>   <span font_desc='Lato 9'>9pt t ti fi tt</span>  
<span
font_desc='Lato 10'>10pt t ti fi tt</span>   <span
font_desc='Lato
11'>11pt t ti fi tt</span>   <span font_desc='Lato 14'>14pt t
ti fi
tt</span>"' and compare the results.
The horizontal stroke over "ti" does not correspond to the one over
"fi" for some font sizes for FreeType without HarfBuzz support.

== User Experience ==
This change improves hinting of glyphs which are composed from
multiple characters.

== Dependencies ==
This change does not need any involvement other than listed owners.

== Contingency Plan ==
This change could be easily reverted if needed.

== Documentation ==
Not needed as both FreeType and HarfBuzz are already present in Fedora
and there will be no change of their code.

== Release Notes ==
There is no need for release notes as HarfBuzz is already in Fedora,
it was just not used by FreeType.

-- 
Ben Cotton
He / Him / His
Senior Program Manager, Fedora & CentOS Stream
Red Hat
TZ=America/Indiana/Indianapolis