NONE of the documents you currently see here are complete
nor are they suitable for reference. PLEASE do not use
them as a guide or as a general information source.
As long as this warning text remains visible, the above
holds true.
At present, we are seeking comments and bugfixes on the Indic-script,
Arabic-like, Hangul, Hebrew, Thai/Lao, Tibetan, Khmer, Myanmar,
default, and USE documents. Interested readers and contributors can
begin at the
Emoji sequences do not constitute a separate shaping model,
but handling emoji sequences can incorporate many of the same
Opentype mechanisms and should not be overlooked
shaping documents and are encouraged to submit their feedback
on the text or images of any of the linked scripts. The documents are
organized by script; where there are multiple shaping models for a
particular script (including deprecated models), the various models are
all addressed in the same script-specific document.
The documents also include a description of
normalization in the OpenType
shaping context, which differs from Unicode normalization in several
respects.
Various notes about the document set and the details
of its scope, limitations, and quirks are also provided.
Some errata about the "upstream" specifications and
reference documents are noted separately.
In its final form, this repository will hold documentation describing
the shaping behavior used for layout of OpenType text. In particular,
it will focus on complex scripts.
In addition to the primary, per-script documents, implementers and
other interesteed readers are encouraged to check the
character tables for correctness and to
examine the image-generation logs to identify
issues seen in the inline images.
References
These documents cite the following informative references:
The Microsoft Script development
specifications,
which document the behaviors expected for OpenType Layout fonts and
provide guidance & examples for type designers. OpenType is a
registered trademark of Microsoft Corporation.
Related portions of the Microsoft OpenType specification, such as the
OpenType Layout tag
registry
and OpenType Layout common table
formats,
which list and define feature tags, script & language tags, and
other internals of compliant OpenType font binaries. OpenType is a
registered trademark of Microsoft Corporation.
The HarfBuzz project, which
includes a free-software/open-source implementation of OpenType
Layout shaping with full source code and documentation.
The Allsorts project, which
includes a free-software/open-source implementation of OpenType
Layout shaping with full source code and documentation.
The Unicode
Standard and
related Unicode Consortium projects such as the Unicode Character
Database, which defines
Unicode code points and formal character properties used in
shaping. Unicode and the Unicode Logo are registered trademarks of
Unicode, Inc. in the United States and other countries.
The YesLogic text corpus,
which includes real-world text data for several Indic scripts,
scraped from Wikipedia, Reddit, and multiple online news
sources. This data is used to test shaping in Allsorts and Prince.
Known but unofficial information about other shaping-engine
projects. Primarily this includes tests and reproducible issues
found via HarfBuzz, because
HarfBuzz intentionally aims to produce results that will 100% match
the output of Microsoft Uniscribe (not counting cases where
Uniscribe's output is known to be incorrect, of course).
Note: occasionally, tests or issues documenting the behavior of
Apple CoreText are also included, but CoreText compatibility is
not an explicit goal for HarfBuzz.