Monday, September 25, 2017

Proposed Draft UTR #53, Unicode Arabic Mark Ordering Algorithm Now Available for Public Review

The Unicode Consortium has released Proposed Draft Unicode Technical Report #53, Unicode Arabic Mark Ordering Algorithm. This UTR describes an algorithm for determining correct rendering of Arabic combining mark sequences.

The combining classes of Arabic combining characters in Unicode are a mixture of special classes for specific marks plus two more generalized classes for all the other marks. For many years this has resulted in inconsistent rendering for sequences with multiple combining marks such as:

The algorithm described in this UTR provides a method to reorder Arabic combining marks in order to accomplish the following goals:
  • The inside-out rendering rule will display combining marks in the expected visual order.
  • Ensure identical display of canonically equivalent sequences.
  • Provide a mechanism for overriding the display order in exceptional cases.
The document is in “Proposed Draft” state, and made available for public review and comment. Information about this type of document can be found on the About Unicode Technical Reports page.

For information about how to discuss this Public Review Issue and how to supply formal feedback, please see the PRI #359 page.