Pango

Pango (Παν語) is an LGPL licensed open source computing library used by software developers for laying out and rendering text in high quality, emphasising support for multilingual text.^[1] Different font backends can be used, allowing cross-platform support, so that Pango-rendered text will appear similar under different operating systems, such as Linux, Apple's Mac OS and Microsoft Windows.

Utilization

Pango has been integrated into most Linux distributions. The GTK+ UI toolkit uses Pango for all of its text rendering. The Linux versions of the Mozilla Firefox web browser and Mozilla Thunderbird mail client use Pango for text rendering.

Name

The name pango comes from Greek pan (παν, "all") and Japanese go (語, "language").^[2]

Support for OpenType features

Pango 1.17 and newer support the locl script tag that allows alternate glyphs to be used for the same Unicode code point. Assuming you have Verdana version 5.01 installed, which supports the locl feature for the latn/ROM (Romanian) script, a quick demonstration (on Linux) is:

for lang in en ro; do pango-view \
 --font="Verdana 64" \
 --text "şţ vs. șț in $lang" \
 --language=$lang; done

For an explanation of the substitutions rules for Romanian, see this discussion.

Setting the locale via the POSIX environment variable, e.g. LANG=ro_RO.UTF-8 will also cause Pango to use locl font feature. Finally, you can change the language on the fly in the same text using Pango markup, e.g.:

pango-view \
 --font="Verdana 24" \
 --markup \
 --text 'In the same text: <span lang="en">şţ</span>(en) and <span lang="ro">şţ</span>(ro).'

The official showcase of Pango's script-aware features is here.

Text and graphics

Complete text handling and graphics rendering is provided when integrated with Cairo.

HarfBuzz

HarfBuzz (in Persian: حرف‌باز) is a layout/shaping engine for OpenType fonts.^[3] Its purpose is to standardize text layout in FOSS; its code originally started as part of the FreeType project, was then developed separately in Qt and Pango, and finally merged back into a common repository. Both Qt and Pango currently use HarfBuzz; other standalone users include Firefox and Chromium, the open source project behind Google Chrome.^[4]

See also

• Uniscribe (Windows multilingual text rendering engine)
• WorldScript (Old Macintosh multilingual text rendering engine)
• Core Text (modern multilingual text rendering engine introduced in Mac OS X 10.5)
• Graphite (multiplatform open source smart-font renderer from SIL)
• Cairo a vector-based graphics library with multiple backends
• FreeType a software library that implements a font rasterization engine
• FontForge a typeface (font) editor program

Notes

References

• Pango, an open-source Unicode text layout engine. by Owen Taylor in Twenty fifth Internationalization and unicode conference, April 2004
• The Pango Connection : Part 1, Tony Graham, 2001
• The Pango Connection : Part 2, Tony Graham, 2001
• "Pango: internationalized text handling" Owen Taylor in Ottawa linux symposium 2001
• "Implementation of Reverse Chaining Mechanism in Pango for Rendering Nastaliq Script" Wali, A., Rehman, S., In the Proceedings of Second Workshop of Computational Approaches to Arabic Script-based Languages (CAASL-2), Stanford University, US, 2007
• "Enhancing Contextual Substitution Support in Pango Using Opentype", Wali, A. MS Thesis, National University of Computer and Emerging Sciences, Lahore, Pakistan, 2004
• Harfbuzz API design discussion thread
• Pango Reference Manual