Harfbuzz

Summary

Port Pango to use Harfbuzz

Owner

Name: Behdad Esfahbod
Email: besfahbo@redhat.com

Current status

Targeted release: Fedora 12
Last updated: 2009-06-05
Percentage of completion: 20%

Harfbuzz/Pango integration happens on the harfbuzz-ng branch in the pango git repository at http://git.gnome.org/cgit/pango.

Detailed Description

HarfBuzz is an implementation of the OpenType Layout engine (aka layout engine) and the script-specific logic (aka shaping engine).

Benefit to Fedora

Harfbuzz reduces the memory consumption of the desktop, since it works with mmapped fonts. Pango may also gain support for some more OpenType features in porting to Harfbuzz, such as BASE table support and better caret positioning in ligatures.

Further down the road (in F13), Harfbuzz will become a standalone library that will hopefully also get used by Qt, which will give us unified shapers and improved support for Indic languages across both KDE and Gnome.

Scope

Only Pango needs to be changed.

How To Test

. Open a text document (TODO: point to a good multilingual document to use here) in an application that uses Pango for text rendering, e.g. gedit. Compare the text rendering between F11 and F12. There should not be any regressions.
. Repeat the above with different OpenType fonts.
. Find the PID of your application, and look at the contents of /proc/<PID>/maps. You should see font files being mmapped.

User Experience

The most noticable change in F12 will probably be the reduced memory consumption. Beyond F12, Indic users should hopefully see improved text rendering of their languages.

Dependencies

None.

Contingency Plan

Stay with a non-Harfbuzz-using version of Pango. Should only require a rebuild of pango itself.

Documentation