MVAR table

Provides variation deltas for global font metrics (ascender, descender, caret offset, etc.) in variable fonts.

Scope

• Format family: Shared SFNT
• Table tag in JSON: MVAR

Specs

• https://learn.microsoft.com/en-us/typography/opentype/spec/mvar
• OpenType table registry: https://learn.microsoft.com/en-us/typography/opentype/spec/otff#font-tables

JSON Skeleton

This skeleton reflects fields currently parsed/written by Font Flux JS for this table.

{
  "tables": {
    "MVAR": {
      "majorVersion": 0,
      "minorVersion": 0,
      "reserved": 0,
      "valueRecords": null,
      "valueRecordSize": 0,
      "itemVariationStore": null,
      "_checksum": 0
    }
  }
}

Top-level Fields

• majorVersion - number (0..65535)
• minorVersion - number (0..65535)
• reserved - number (0..65535)
• valueRecords - implementation-defined
• valueRecordSize - number (0..65535)
• itemVariationStore - implementation-defined

Additional Nested Keys Seen In Implementation

• valueTag
• deltaSetOuterIndex
• deltaSetInnerIndex
• _extra

Notes

• Preserve _checksum for stable round-tripping.
• If a table is only partially understood, prefer keeping unknown bytes in _raw instead of dropping data.
• Validate with .validate() after edits.