OpenType 1.8.4 released

Peter Constable
Peter Constable Posts: 208
in Font Technology
Version 1.8.4 of the OpenType spec has been released.

The scope of changes was determined almost entirely by issues reported on OT 1.8.3 in the MicrosoftDocs/typography-issues GitHub repo. Changes in this version are mostly editorial, though there are some limited technical changes:

  • COLR table: In version 1.8.3, it was required that a font implement glyph ID 1 as the .null glyph. This is changed to a note regarding compatibility for earlier Windows versions.

  • DSIG table: Steps for signing or validating a signature have been revised to correctly match long-standing implementations.

  • STAT table:

    • Relaxed the constraint on name IDs used for AxisRecord.axisNameID.
    • Revised constraints and recommendations regarding separate axis value tables having the same information.

  • OpenType Layout tag registry:

    • Features: The 'chws', 'vchw' are added; the 'opbd' feature is deprecated.
    • Language system tags added: 'AKB ', 'BTD ', 'BTK ', 'BTM ', 'BTX ', 'BTZ ', ZHTM
    • Script tags added: Added script tags for new scripts in Unicode 12 and Unicode 13.

  • OpenType Font Variations Common Table Formats:

    • Defined a special meaning of delta-set outer- and inner-level indices 0xFFFF/0xFFFF as an indication of no variation data.
    • Added a constraint on VariationRegionList.regionCount to be less than 32,768 (high bit reserved).

Various structure or field names have been revised to follow general naming conventions used throughout the spec.

Certain structural changes have also been made:

  • Some content in the 'avar' chapter related to normalization has been moved into the OpenType Font Variations Overview chapter.
  • Subtable formats used in both GSUB and GPOS lookups that previously were documented separately and with different names for substitution and for positioning are now documented as common formats with common names in the OpenType Layout Common Table Formats chapter.
  • Certain pages that had no or very little significant content of their own, mainly providing a link to other content, have been removed. If the removed page did contain any relevant content, it has been incorporated into another related page.
  • The pages for the Windows Glyph List 4.0, that were included as an appendix to the spec, have been removed from the spec. These are not directly relevant to the file format specification—they are better characterized as guidance for development of fonts for use on Windows—and the content has been moved elsewhere on the Microsoft Typography site.

Undoubtedly, there are probably some typos introduced, and technical details that still need clarification. It's most helpful to file issues using the feedback link at the bottom of each page of the spec. 

I’d like to acknowledge and thank Google Fonts and Microsoft who have made this possible.

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