Changes/FontLangProvidesToLangpacks

Font Dependencies to Langpacks

Summary

Move Provides: font(:lang=...) from fonts packages into the langpacks package, giving predictable default fonts for language scripts.

Motivation

Currently fonts packages has auto-generated font(:lang=...) provides, which can be used as a dependency identifier to satisfy font coverage required for a certain language requirement. This is used by GTK application to install missing fonts via PackageKit for example. However in practice it has not been very useful since usually there are multiple varied fonts providing coverage for languages and so an arbitrary fonts of unknown quality would get selected, so the mechanism is not unreliable.

This change uses instead the default fonts selected in langpacks for each language, to give reliable predictable default fonts for each language and improve the user application experience around fonts.

Owner

• Name: Akira TAGOH
• Email: tagoh@redhat.com
• Release notes owner:

Current status

• Targeted release: Fedora 32
• Last updated: 2019-12-27
• Tracker bug: <will be assigned by the Wrangler>

Detailed Description

The language based metadata for fonts packages was introduced in Fedora 11. The idea being to provide a mechanism to find and install a font for missing glyphs through PackageKit and was useful for minority languages which might be missing default installed fonts packages. But the user experience was generally not terribly good.

Users cannot predict which fonts will be installed. This often leads to poor fonts choices installed, particularly for languages with too many available fonts such as English, since the first font found lexically will be arbitrarily chosen with gurantee of quality or expected style. This random dependency sometimes introduces highly unexpected results too - for example a font from an external repository may get chosen by chance. This would be particularly problematic when composing ISOs, eg when including EPEL.

So this Changes proposal aims to improve the user experience around font dependencies by moving the meta-provides the langpacks package instead. Langpacks contains various dependencies to use for certain languages, including dependencies for default fonts. so it will resolve the above issues.

Specifically speaking, currently font dependency is generated like this:

$ fc-query -f %{=pkgkit}  /usr/share/fonts/dejavu/DejaVuSans.ttf
font(dejavusans)
font(:lang=aa)
font(:lang=ab)
...

and at the build time, it is transformed to:

Provides: font(dejavusans)
Provides: font(:lang=aa)
Provides: font(:lang=ab)
...

After this proposal, the above result will be:

Provides: font(dejavusans)

and then add Provides: font(:lang=...) line to corresponding sub-packages langpacks-core-*.

So asking for a font for a certain language through PackageKit will be achieved by langpacks-core-* instead of a random font package.

Benefit to Fedora

This proposal provides reliable, predictable, and consistencies in dependencies about fonts.

Scope

• Proposal owners:
  • Update fontconfig to drop font(:lang=...) from the alias of the formatter for %{=pkgkit}
  • Add a line of Provides: font(:lang=...) to each langpacks-core-.... for instance, Provides: font(:lang=hi) need to be added to langpacks-core-hi.

• Other developers: Release Engineers needs to rebuild all of fonts packages with the updated fontconfig package.

• Release engineering: #Releng issue number
  • List of deliverables: None

• Policies and guidelines: None

• Trademark approval: None

Upgrade/compatibility impact

Some packages may be installed after upgrading if corresponding langpacks-core-* packages isn't yet installed.

How To Test

1. Check dependencies in langpacks-core-*. they must have corresponding Provides: font(:lang=...) line when asking with rpm -q --provides.
2. Check dependencies in fonts packages. they must contain no Provides: font(:lang=...) lines

User Experience

Users may see better fonts for certain language when they need to install a set of fonts for certain language support through PackageKit or package dependencies from others.

Dependencies

All of fonts packages

Contingency Plan

• Contingency mechanism: (What to do? Who will do it?) Proposal owners will revert all of changes and rebuild all of fonts packages to add back deps
• Contingency deadline: the beta freeze
• Blocks release? No
• Blocks product? N/A

Documentation

N/A