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


This change uses instead the default fonts chosen in `langpacks` for each language, to give reliable predictable default fonts for each language and improve the user application experience around fonts.
This change instead moves `font(:lang=xy)` provides to `langpacks-core-font-xy` which pulls in the expected default font for that language, to give reliable predictable default fonts for each language and improve the user application experience around fonts.


== Owner ==
== Owner ==
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CLOSED as NEXTRELEASE -> change is completed and verified and will be delivered in next release under development
CLOSED as NEXTRELEASE -> change is completed and verified and will be delivered in next release under development
-->
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* Tracker bug: <will be assigned by the Wrangler>
* Tracker bug: [https://bugzilla.redhat.com/show_bug.cgi?id=1792463 #1792463]
* Release Notes tracker: [https://pagure.io/fedora-docs/release-notes/issue/433 #433]


== Detailed Description ==
== 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 very good.
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 very 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 guarantee of quality or expected style.
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 ''no'' guarantee of quality or expected style.
This random dependency resolution 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.
This random dependency resolution sometimes introduces highly unexpected results too - for example a font from an external repository may get chosen by chance. This can be particularly problematic when composing ISOs, eg including EPEL.


So this Change proposal aims to improve the user experience around font dependencies by moving the `Provides:` tag into the `langpacks` package instead. Langpacks contains various dependencies to help to use that langpacks language. Langpacks have `langpacks-core-*` subpackages which installs default font and input-method. Once `Provides:` tag added to these subpackages, whenever missing glyph font installation is requested, only `langpacks-core-<lang>` package will get installed which will be anyway already having default font set using `Requires:` tag.
So this Change proposal aims to improve the user experience around font dependencies by consolidating the `Provides: font(:lang=*)` tags into the `langpacks-core-font-*` subpackages of the `langpacks` package instead. The subpackages already pull in the default font (and locale and input-method) for each language. Once all the `Provides:` tags are moved to these subpackages, whenever a missing glyph font installation is requested, the `langpacks-core-font-<lang>` package will get installed which will pull in default font using the existing `Requires:` tag.


Currently font provides are auto-generated using fc-query by rpm like this:
Currently font provides are auto-generated using fc-query by rpm like this:
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</pre>
</pre>


After this proposal will be implemented, the above result will be:
After this proposal is implemented, the result will become just:
<pre>
<pre>
Provides: font(dejavusans)
Provides: font(dejavusans)
</pre>
</pre>


and then add `Provides: font(:lang=...)` line to corresponding sub-packages langpacks-core-*.
and instead `Provides: font(:lang=...)` will be added to the corresponding sub-packages langpacks-core-font-*.


So asking for a font for a certain language through PackageKit will be achieved by langpacks-core-* instead of a random font package.
So asking for a font for a certain language through PackageKit will be achieved by langpacks-core-font-* instead of a random font package.
<!-- Expand on the summary, if appropriate.  A couple sentences suffices to explain the goal, but the more details you can provide the better. -->
<!-- Expand on the summary, if appropriate.  A couple sentences suffices to explain the goal, but the more details you can provide the better. -->


== Benefit to Fedora ==
== Benefit to Fedora ==
This proposal will provide reliable, predictable, and consistent font dependencies.
This proposal will provide more reliable, predictable, and consistent fonts installation.


<!-- What is the benefit to the distribution?  Will the software we generate be improved? How will the process of creating Fedora releases be improved?
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* Proposal owners:
* Proposal owners:
** Update fontconfig to drop generating `font(:lang=...)` from the alias of the formatter for `%{=pkgkit}`
** Update fontconfig to drop generating `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)` needs to be added to `langpacks-core-hi`.
** `Provides: font(:lang=...)` will be added to each `langpacks-core-font-...` subpackage. <br/> For instance, `langpacks-core-font-hi` will have `Provides: font(:lang=hi)`.
 
<!-- What work do the feature owners have to accomplish to complete the feature in time for release?  Is it a large change affecting many parts of the distribution or is it a very isolated change? What are those changes?-->


* Other developers: Release Engineers needs to rebuild all fonts packages with the updated fontconfig package. <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
* Other developers: Release Engineers needs to rebuild all fonts packages with the updated fontconfig package. <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
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== Upgrade/compatibility impact ==
== Upgrade/compatibility impact ==
Some packages may be installed after upgrading if corresponding langpacks-core-* packages isn't yet installed.
When upgrading some additional packages may get installed to pull in the correct requested default fonts for a language,
<!-- What happens to systems that have had a previous versions of Fedora installed and are updated to the version containing this change? Will anything require manual configuration or data migration? Will any existing functionality be no longer supported? -->
if the `langpacks-core-font-*` subpackage isn't already installed. In practice very few packages depend on `font(:lang=*)`, so in practice the impact should be small and will correct the loosely chosen font.
 
<!-- REQUIRED FOR SYSTEM WIDE CHANGES -->


== How To Test ==
== How To Test ==
<!-- This does not need to be a full-fledged document. Describe the dimensions of tests that this change implementation is expected to pass when it is done.  If it needs to be tested with different hardware or software configurations, indicate them.  The more specific you can be, the better the community testing can be.
Use this test case https://fedoraproject.org/wiki/QA:Testcase_default_font_installation
 
Remember that you are writing this how to for interested testers to use to check out your change implementation - documenting what you do for testing is OK, but it's much better to document what *I* can do to test your change.
 
A good "how to test" should answer these four questions:
 
0. What special hardware / data / etc. is needed (if any)?
1. How do I prepare my system to test this change? What packages
need to be installed, config files edited, etc.?
2. What specific actions do I perform to check that the change is
working like it's supposed to?
3. What are the expected results of those actions?
-->
1. Currently this Change implementation is available in https://copr.fedorainfracloud.org/coprs/pnemade/FontLangProvidesToLangpacks/ Copr repository for F31+ releases. Download and enable this repository on your system.
 
2. Now if you want to install font for Japanese language, check which package is providing `font(:lang=ja)` dependency
  $ dnf repoquery --whatprovides "font(:lang=ja)" --recent
    langpacks-core-ja-0:2.0-9.1.testing.fc32.noarch
 
3. Check if any font packages are still there which are providing `font(:lang=ja)` dependency. Again same above command shows only one package in Fedora now providing Japanese language font.
 
4. Check that langpacks-core-* pulls in the only one default expected font for the language.
  <pre>
  ⬢[parag@toolbox fedora]$ sudo dnf install langpacks-core-ja
Last metadata expiration check: 0:00:28 ago on Mon Jan 13 19:50:39 2020.
Dependencies resolved.
===============================================================================
Package                        Arch  Version              Repository    Size
===============================================================================
Installing:
langpacks-core-ja              noarch 2.0-9.1.testing.fc32 copr:copr.fedorainfracloud.org:pnemade:FontLangProvidesToLangpacks
                                                                        8.8 k
Installing dependencies:
google-noto-cjk-fonts-common  noarch 20190416-5.fc31      rawhide      20 k
google-noto-sans-cjk-ttc-fonts noarch 20190416-5.fc31      rawhide      86 M
 
Transaction Summary
===============================================================================
Install  3 Packages
 
Total download size: 86 M
Installed size: 130 M
....
</pre>


== User Experience ==
== User Experience ==
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[[Category:ChangeReadyForFesco]]
[[Category:ChangeAcceptedF32]]
<!-- When your change proposal page is completed and ready for review and announcement -->
<!-- When your change proposal page is completed and ready for review and announcement -->
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<!-- remove Category:ChangePageIncomplete and change it to Category:ChangeReadyForWrangler -->

Latest revision as of 03:59, 30 January 2020


Move fonts language Provides to Langpacks

Summary

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

Motivation

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

This change instead moves font(:lang=xy) provides to langpacks-core-font-xy which pulls in the expected default font for that language, to give reliable predictable default fonts for each language and improve the user application experience around fonts.

Owner

Current status

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 very 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 no guarantee of quality or expected style. This random dependency resolution sometimes introduces highly unexpected results too - for example a font from an external repository may get chosen by chance. This can be particularly problematic when composing ISOs, eg including EPEL.

So this Change proposal aims to improve the user experience around font dependencies by consolidating the Provides: font(:lang=*) tags into the langpacks-core-font-* subpackages of the langpacks package instead. The subpackages already pull in the default font (and locale and input-method) for each language. Once all the Provides: tags are moved to these subpackages, whenever a missing glyph font installation is requested, the langpacks-core-font-<lang> package will get installed which will pull in default font using the existing Requires: tag.

Currently font provides are auto-generated using fc-query by rpm like this: 

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

and at the font package build time, it is transformed to: 

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

After this proposal is implemented, the result will become just: 

Provides: font(dejavusans)

and instead Provides: font(:lang=...) will be added to the corresponding sub-packages langpacks-core-font-*.

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

Benefit to Fedora

This proposal will provide more reliable, predictable, and consistent fonts installation.


Scope

  • Proposal owners:
    • Update fontconfig to drop generating font(:lang=...) from the alias of the formatter for %{=pkgkit}
    • Provides: font(:lang=...) will be added to each langpacks-core-font-... subpackage.
      For instance, langpacks-core-font-hi will have Provides: font(:lang=hi).
  • Other developers: Release Engineers needs to rebuild all fonts packages with the updated fontconfig package.
  • Policies and guidelines: None
  • Trademark approval: None

Upgrade/compatibility impact

When upgrading some additional packages may get installed to pull in the correct requested default fonts for a language, if the langpacks-core-font-* subpackage isn't already installed. In practice very few packages depend on font(:lang=*), so in practice the impact should be small and will correct the loosely chosen font.

How To Test

Use this test case https://fedoraproject.org/wiki/QA:Testcase_default_font_installation

User Experience

Users should see better quality fonts for the chosen languages when they install a font to cover a certain language script through PackageKit or through font meta dependencies of other packages.


Dependencies

All fonts packages

Contingency Plan

  • Contingency mechanism: proposal owners will revert all the changes and rebuild all fonts packages to add back the provides.
  • Contingency deadline: the beta freeze
  • Blocks release? No
  • Blocks product? N/A

Documentation

N/A

Release Notes

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