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Revision as of 10:09, 25 December 2019 by Pwu (talk | contribs) (Owner)


Convert Bitmap Font

Summary

This proposal plans to start converting the bitmap fonts in Fedora from legacy BDF/PCF format to modern OpenType format.

Owner

Current status

  • Targeted release: Fedora 32
  • Last updated: 2019-12-25
  • Tracker bug: <will be assigned by the Wrangler>
  • Release notes tracker: <will be assigned by the Wrangler>

Detailed Description

In Fedora 31, pango has been upgraded to 1.44, and switch to use harfbuzz library.

But harfbuzz doesn't support bitmap fonts or Adobe Type 1 fonts. In gnome-terminal, the bitmap fonts can't be used.

In order to use the bitmap fonts with pango 1.44. We propose to convert the bitmap fonts to OpenType fonts by fonttosfnt tool.

Benefit to Fedora

Some bitmap fonts are used by many users.

After converted the bitmap fonts, users can continue to use the bitmap fonts in gnome-terminal, etc.

Scope

  • Proposal owners: Fonts SIG
  • Other developers: X.Org Maintainers
    • Need to update the fonttosfnt tool in the xorg-x11-font-utils package.
  • Release engineering: Releng issue 9130 (a check of an impact with Release Engineering is needed)
  • Policies and guidelines: Fonts Policy
  • Trademark approval: N/A (not needed for this Change)

Upgrade/compatibility impact

It depends on how we package the converted OpenType fonts.

  • If we keep the converted OpenType fonts or both fonts in the same package, the upgrade path is simple.
  • If we introduce new sub package for bitmap fonts or OpenType fonts, the upgrade path need to be considered.
    • One possible solution for upgrade is to include the converted OpenType fonts in the original package, but provide the bitmap fonts in some compatibility package.

How To Test

  1. Install the converted OpenType bitmap fonts.
  2. Check whether the converted bitmap fonts is listed in gnome-terminal, gedit, etc.
  3. Compare the font rendering with Fedora 30, the converted fonts should look similar with the original bitmap fonts.

User Experience

After converting the bitmap fonts, users will be able to use the new OpenType Bitmap font again with pango 1.44 in gnome-terminal, etc.

The converted bitmap fonts should have the similar shape for each glyph.

Dependencies

Update the fonttosfnt package in xorg-x11-font-utils, which is the needed tool for bitmap font conversion.

And we plan to pick 5-10 most popular bitmap fonts for conversion.

We will try to find the better way for the conversion, then update more bitmap fonts in later updates or next Fedora release.

Contingency Plan

  • Contingency mechanism: Fonts SIG will revert the changed 5-10 bitmap font packages.
  • Contingency deadline: Beta Freeze
  • Blocks release? No
  • Blocks product? product

Documentation

This change will enable Fedora 32 to use bitmap fonts with pango 1.44 again.

Release Notes

In Fedora 32, we provide bitmap fonts with modern font format (OpenType Bitmap Font) to use with gnome-terminal and other applications which uses pango for font rendering.